DC HIGH VOLTAGE RELAY AND CONTACT MATERIAL FOR DC HIGH-VOLTAGE RELAY
20210012977 ยท 2021-01-14
Assignee
Inventors
- Sachihiro NISHIDE (Tomioka-shi, JP)
- Tetsuya NAKAMURA (Tomioka-shi, JP)
- Hiroyuki ITAKURA (Tomioka-shi, JP)
- Nobuhito YANAGIHARA (Tomioka-shi, JP)
Cpc classification
H01H50/58
ELECTRICITY
C22F1/00
CHEMISTRY; METALLURGY
International classification
Abstract
A DC high-voltage relay including at least one contact pair including a movable contact and a fixed contact, having a contact force and/or opening force of 100 gf or more, the DC high-voltage relay of 48 V or more. The movable contact and/or the fixed contact includes Ag oxide-based contact material. Metal components in the contact material includes at least one metal M essentially containing Sn, and a balance including Ag and inevitable impurity metals. The content of the metal M is 0.2% by mass or more and 8% by mass or less based on the total mass of all metal components in the contact material. The contact material has a material structure in which one or more oxides of the metal M are dispersed in a matrix including Ag or a Ag alloy. As metal M, In, Bi, Ni and Te can be added.
Claims
1. A DC high-voltage relay comprising at least one contact pair comprising a movable contact and a fixed contact, the contact pair having a contact force and/or opening force of 100 gf or more, the DC high-voltage relay having a rated voltage of 48 V or more, wherein the movable contact and/or the fixed contact comprises a Ag oxide-based contact material, the contact material has metal components comprising at least one metal M essentially containing Sn, and a balance being Ag and inevitable impurity metals, the contact material has a content of the metal M being 0.2% by mass or more and 8% by mass or less based on a total mass of all metal components, and the contact material has a material structure in which one or more oxides of the metal M are dispersed in a matrix including Ag or a Ag alloy.
2. The DC high-voltage relay according to claim 1, wherein the contact material contains In as metal M, the contact material has a content of In is 0.1% by mass or more and 5% by mass or less based on a total mass of all metal components, and the contact material has a content of Sn being 0.1% by mass or more and 7.9% by mass or less based on the total mass of all metal components.
3. The DC high-voltage relay according to claim 1, wherein the contact material contains Bi as metal M, a content of Bi is 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
4. The DC high-voltage relay according to claim 1, wherein the contact material contains Te as metal M, the contact material has a content of Te being 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
5. The DC high-voltage relay according to claim 2, wherein the contact material further contains Ni as metal M, the contact material has a content of Ni being 0.05% by mass or more and 1% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.85% by mass or less based on the total mass of all metal components.
6. The DC high-voltage relay according to claim 1, comprising: a drive section which generates and transmits a drive force for moving a movable contact; and a contact section which performs switching of a DC high-voltage circuit, the drive section comprises an electromagnet or a coil which generates a drive force; a transmission unit which transmits the drive force to the contact section; and a biasing unit which biases the transmission unit for closing or opening the contact pair, the contact section comprises at least one contact pair including a fixed contact and a movable contact which is moved by the transmission unit of the drive section; and at least one movable terminal bonded to the movable contact and at least one fixed terminal bonded to the fixed contact.
7. The DC high-voltage relay according to claim 1, wherein oxides dispersed in a matrix of the contact material has an average particle size of 0.01 m or more and 0.3 m or less.
8. The DC high-voltage relay according to claim 1, wherein oxides on an arbitrary cross-section of the contact material has an area ratio of 0.1% or more and 15% or less.
9. A contact material for a DC high-voltage relay, the contact material being a Ag oxide-based contact material for forming at least a surface of a movable contact and/or a fixed contact of a DC high-voltage relay, the DC high-voltage relay having a rated voltage of 48 V or more, and a contact force and/or opening force of 100 gf or more at a contact pair, wherein metal components in the contact material comprise at least one metal M essentially containing Sn, and a balance being Ag and inevitable impurity metals, the contact material has a content of the metal M being 0.2% by mass or more and 8% by mass or less based on a total mass of all metal components of, and the contact material has a material structure in which one or more oxides of the metal M are dispersed in a matrix including Ag or a Ag alloy.
10. The contact material for a DC high-voltage relay according to claim 9, wherein the contact material contains In as metal M, the contact material has a content of In being 0.1% by mass or more and 5% by mass or less based on a total mass of all metal components, and the contact material has a content of Sn being 0.1% by mass or more and 7.9% by mass or less based on the total mass of all metal components.
11. The contact material for a DC high-voltage relay according to claim 9, wherein the contact material contains Bi as metal M, the contact material has a content of Bi being 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
12. The contact material for a DC high-voltage relay according to claim 9, wherein the contact material contains Te as metal M, the contact material has a content of Te being 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
13. The contact material for a DC high-voltage relay according to claim 10, wherein the contact material further contains Ni as metal M, the contact material has a content of Ni is 0.05% by mass or more and 1% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn is 0.1% by mass or more and 7.85% by mass or less based on the total mass of all metal components.
14. The contact material for a DC high-voltage relay according to claim 9, wherein an average particle size of oxides dispersed in the matrix is 0.01 m or more and 0.3 m or less.
15. The contact material for a DC high-voltage relay according to claim 9, wherein an area ratio of the oxides on an arbitrary cross-section is 0.1% or more and 15% or less.
16. The DC high-voltage relay according to claim 2, wherein the contact material contains Bi as metal M, a content of Bi is 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
17. The DC high-voltage relay according to claim 2, wherein the contact material contains Te as metal M, the contact material has a content of Te being 0.05% by mass or more and 2% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.95% by mass or less based on the total mass of all metal components.
18. The DC high-voltage relay according to claim 4, wherein the contact material further contains Ni as metal M, the contact material has a content of Ni being 0.05% by mass or more and 1% by mass or less based on the total mass of all metal components, and the contact material has the content of Sn being 0.1% by mass or more and 7.85% by mass or less based on the total mass of all metal components.
19. The DC high-voltage relay according to claim 2, comprising: a drive section which generates and transmits a drive force for moving a movable contact; and a contact section which performs switching of a DC high-voltage circuit, the drive section comprises an electromagnet or a coil which generates a drive force; a transmission unit which transmits the drive force to the contact section; and a biasing unit which biases the transmission unit for closing or opening the contact pair, the contact section comprises at least one contact pair including a fixed contact and a movable contact which is moved by the transmission unit of the drive section; and at least one movable terminal bonded to the movable contact and at least one fixed terminal bonded to the fixed contact.
20. The DC high-voltage relay according to claim 3, comprising: a drive section which generates and transmits a drive force for moving a movable contact; and a contact section which performs switching of a DC high-voltage circuit, the drive section comprises an electromagnet or a coil which generates a drive force; a transmission unit which transmits the drive force to the contact section; and a biasing unit which biases the transmission unit for closing or opening the contact pair, the contact section comprises at least one contact pair including a fixed contact and a movable contact which is moved by the transmission unit of the drive section; and at least one movable terminal bonded to the movable contact and at least one fixed terminal bonded to the fixed contact.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0082]
[0083]
[0084]
[0085]
[0086]
[0087]
DESCRIPTION OF EMBODIMENTS
[0088] Hereinafter, an embodiment of the present invention will be described. In this embodiment, metal M and compositions were adjusted to manufacture various Ag oxide-based contact materials, and structure observation and hardness measurement were performed. The manufactured Ag oxide-based contact materials were incorporated as contacts in a DC high-voltage relay, and the properties of the contact materials were evaluated.
[0089] First Embodiment: In this embodiment, various Ag oxide-based contact materials were manufactured by an internal oxidation method and a powder metallurgy method, material properties were examined, a DC high-voltage relay (contact force/opening force: 75 gf/125 gf) was then manufactured, and performance was evaluated.
[0090] In manufacturing of the contact material by the internal oxidation method, Ag alloys having various compositions were melted in a high-frequency melting furnace, and cast into an ingot. The ingot was formed into pieces of 3 mm or less, and the pieces were internally oxidized under the above-described conditions. After the internal oxidation, the pieces were collected, and compression-molded to form billets of 50 mm. The billets were subjected to hot extrusion processing, and subsequently subjected to drawing processing to obtain a wire rod having a diameter of 2.3 mm, and a rivet-type contact material was manufactured with a header machine. For the contact materials of Examples 15 and 27, internal oxidation treatment was performed after processing of the contact materials. In Examples 15 and 27, processing steps were carried out without internally oxidizing alloy ingots, the alloy ingots were processed into a rivet shape, then subjected to internal oxidation treatment, and appropriately molded to obtain a rivet-type contact material.
[0091] In manufacturing of the contact material by the powder metallurgy method, Ag powder and oxide powder (each having an average particle size of 0.5 to 100 m) were mixed, and compression-molded to form billets of 50 mm. The manufactured billets were subjected to hot extrusion processing, and subsequently subjected to drawing processing to obtain a wire rod having a diameter of 2.3 mm, and a rivet-type contact material was manufactured with a header machine.
[0092] In this embodiment, two rivet-type contact materials, with one for a movable contact and the other for a fixed contact, were manufactured. The size of a head portion of the movable contact was set to a diameter of 3.15 mm and a height of 0.75 mm, and the size of a head portion of the fixed contact was set to a diameter of 3.3 mm and a height of 1.0 mm.
[Hardness Measurement]
[0093] In a process for manufacturing the contact materials, a wire sample was cut out from the wire rod subjected to drawing processing and annealed (temperature: 700 C.), and the hardness was measured. For hardness measurement, the sample was embedded in a resin, exposure polishing was performed so as to expose a lateral cross-section (cross-section in a short direction), and the hardness was measured with a Vickers hardness meter. For measurement conditions, the load was set to 200 gf, measurement was performed at five positions, and an average for the measurements was defined as a hardness value.
[0094] Table 1 shows the compositions and the hardness values of the contact materials of Examples (Examples 1 to 32) manufactured in this embodiment. Table 2 shows the compositions and the hardness values of the contact materials of comparative examples (Comparative Examples 1 to 10). In this embodiment, a contact material having no oxide particles and formed of pure Ag was manufactured and evaluated for comparison (Comparative Example 10). This Ag contact was manufactured by hot-extruding the melted and cast billets and performing processing etc. The hardness of the Ag contact was measured with a sample cut out after the Ag wire rod was annealed (temperature: 700 C.), and then subjected to drawing processing at a processing rate of 4.2%.
TABLE-US-00001 TABLE 1 Composition (mass %)*.sup.1 Hardness Ag Sn Bi In Ni Te (Hv) Example 1 Balance 4.70 0.10 105 Example 2 4.50 0.30 98 Example 3 4.40 0.50 103 Example 4 4.00 0.90 92 Example 5 3.90 0.90 0.10 106 Example 6 3.50 1.30 0.10 106 Example 7 3.10 1.70 0.10 99 Example 8 3.20 1.30 0.10 0.30 95 Example 9 2.90 0.10 102 Example 10 2.90 2.00 82 Example 11 3.40 2.00 82 Example 12 4.00 2.00 77 Example 13 4.50 1.50 97 Example 14 4.75 0.05 114 Example 15 4.70 0.10 118 Example 16 5.90 0.10 114 Example 17 2.80 0.10 106 Example 18 2.80 3.10 85 Example 19 3.40 0.80 119 Example 20 5.00 1.00 98 Example 21 2.80 1.50 0.50 99 Example 22 2.80 1.50 1.50 93 Example 23 2.80 1.50 0.10 0.10 96 Example 24 3.00 108 Example 25 4.80 109 Example 26 6.00 117 Example 27 4.00 0.80 91 Example 28 6.00 2.00 81 Example 29 7.90 0.10 114 Example 30 5.00 2.00 109 Example 31 7.00 1.00 91 Example 32 7.50 116 The contact material of Example 31 was manufactured by the powder metallurgy method, and the contact materials of other examples were manufactured by the internal oxidation method. *.sup.1Concentration based on all metal components
TABLE-US-00002 TABLE 2 Composition (mass %)*.sup.1 Hardness Ag Sn Bi In Ni Te (Hv) Comparative Balance 9.50 116 Example 1 Comparative 10.50 0.90 91 Example 2 Comparative 7.40 4.00 0.10 0.50 98 Example 3 Comparative 3.00 3.00 83 Example 4 Comparative 5.00 4.00 97 Example 5 Comparative 2.00 7.00 86 Example 6 Comparative 3.40 0.80 0.10 2.50 75 Example 7 Comparative 9.70 67 Example 8 Comparative 3.20 1.30 1.50 2.00 *.sup.2 Example 9 Comparative 100 50 Example 10 The contact materials of Comparative Examples 1 to 7 and 9 were manufactured by the internal oxidation method, and the contact material of Comparative Example 8 was manufactured by the powder metallurgy method. The contact material of Comparative Example 10 (Ag) was manufactured by subjecting melted and cast billets to hot extrusion processing etc. *.sup.1Concentration based on all metal components *.sup.2Sample processing was impossible
[Structure Observation]
[0095] Next, the structures of the contact materials were observed. A transverse section of a sample embedded in a resin as in hardness measurement was observed with an electron microscope (SEM) (magnification of 5000 times). The formed SEM image was subjected to image processing by the use of particle analysis software. In the image processing, the total area (area ratio to the visual field area), the average particle size and the particle size distribution of oxides were measured and analyzed as a dispersion state of the oxides in the contact material. For the analysis, Particle Analysis System AZtecFeature made by Oxford Instruments was used. The particle size was determined in terms of an equivalent circular diameter (areal equivalent circular diameter). Based on the area f of each oxide particle, the particle size of the oxide particle was calculated from an equivalent circular diameter calculation formula ((4f/).sup.1/2), and the average and the standard deviation a of the particle sizes were determined.
[0096]
TABLE-US-00003 TABLE 3 Dispersion state of oxide particles Particle Average size Area particle standard Composition (mass %)*.sup.1 ratio size deviation Ag Sn Bi In Ni Te (%) (m) (m) Example 1 Balance 4.70 0.10 9.00 0.098 0.056 Example 2 4.50 0.30 8.24 0.103 0.067 Example 3 4.40 0.50 8.63 0.116 0.079 Example 4 4.00 0.90 7.33 0.109 0.087 Example 6 3.50 1.30 0.10 6.49 0.044 0.044 Example 8 3.20 1.30 0.10 0.30 8.17 0.059 0.060 Example 9 2.90 0.10 5.77 0.086 0.043 Example 12 4.00 2.00 10.41 0.249 0.178 Example 13 4.50 1.50 9.94 0.222 0.149 Example 14 4.75 0.05 10.09 0.082 0.066 Example 16 5.90 0.10 10.83 0.087 0.072 Example 18 2.80 3.10 10.49 0.231 0.175 Example 19 3.40 0.80 6.59 0.066 0.030 Example 20 5.00 1.00 14.27 0.085 0.089 Example 23 2.80 1.50 0.10 0.10 8.39 0.075 0.059 Example 24 3.00 7.54 0.074 0.033 Example 25 4.80 9.14 0.084 0.049 Example 26 6.00 12.59 0.090 0.057 Example 28 6.00 2.00 13.94 0.232 0.179 Example 29 7.90 0.10 14.27 0.085 0.089 Example 32 7.50 8.36 0.060 0.068 Comparative 10.50 0.90 19.43 0.186 0.199 Example 2 Comparative 7.40 4.00 0.10 0.50 16.17 0.173 0.152 Example 3 Comparative 9.70 21.14 0.581 0.541 Example 8 *.sup.1Concentration based on all metal components
[0097]
[Interruption Durability Evaluation Test in DC high-Voltage Relay]
[0098] Next, DC high-voltage relays containing the contact materials of examples and comparative examples were manufactured, and tests for evaluating the properties of these DC high-voltage relays were conducted. Here, relays of the same type as in
[0099] In the test for evaluation of the DC high-voltage relay in this embodiment, an interruption operation simulating an interruption operation at the time of occurrence of abnormality was repeatedly carried out, and the number of the operations (interruptions) until interruption failure occurred due to welding of contacts was measured. The number of interruptions is a criterion showing interruption durability of the contact material, which is characterized by a relation between the contact force/opening force and the welding resistance of the relay. That is, the number of interruptions measured in this test does not give a mere assessment of welding resistance, but gives an index of usability of the relay itself. The test conditions for the interruption durability test in this embodiment were set as follows: voltage/current: DC 360 V.400 A and contact force/opening force of movable contact: 75 gf/125 gf. The setting of the contact force was adjusted by the strength of a contact pressure spring, and the setting of the opening force was adjusted by the strength of a return spring. The DC high-voltage relay used for the evaluation test has a double-break structure, the forces exerted on the contact pairs are each of the force given by the contact pressure spring and the return spring. The forces exerted on the contact pairs were defined as a contact force and an opening force, respectively. In the interruption durability test, the upper limit of the number of interruptions was set to 100 times, and the measurement of a sample was ended at the time when the 100th interruption was completed. In the interruption durability test, contacts for which the number of interruptions was 50 or more times was rated acceptable. Contacts for which the number of interruptions was less than 50 times was evaluated as being unable to satisfy welding resistance required for the DC high-voltage relay. In practical use, principal interruption of the DC high-voltage relay occurs only once at the time of abnormality. Hence, the acceptance criterion which requires that the number of interruptions be 50 times in the interruption durability test is significantly high even after consideration of a margin.
[0100] For the contact material after the interruption durability test, the melting area was measured. For measurement of the melting area, a contact surface after the interruption durability test was observed from above with a digital microscope, a molten portion was surrounded by area selection, and the area of the portion was measured as the area of the contact surface by the use of a measurement function of the digital microscope. A difference between the areas before and after the durability test was determined, the difference in area was divided by the number of interruption tests of the sample, and the thus-obtained value was defined as a melting area. The melting area is an index of ease of shape collapse of a contact, which can be caused by a load at the time of interruption. Since the DC relay of double-break structure, which was used in this embodiment, had two contact pairs, a total of four contact materials were used. The measurement of the melting area was performed for the four contact materials, and the total value for the contact materials was evaluated.
[Contact Resistance/Heat Generation Measurement]
[0101] The contact resistance was measured for the contact materials of examples and comparative examples. The contact materials were incorporated in the same relay as in the above-described interruption durability test, and an interruption operation was carried out five times under the same conditions as in the interruption durability test, followed by measuring the value of contact resistance. After the five interruption operations, the contact resistance was measured with a change made to connection of the relay to a resistance measuring circuit (DC5V30A) prepared separately from the interruption test circuit. In the contact resistance measurement, a voltage drop between the terminals was measured at the time when a current (30 A) was continuously fed to the circuit for 30 minutes). A value obtained by dividing the measured voltage drop value (mV) by the fed current (30 A) was defined as the contact resistance (m). In addition, a temperature rise caused by heat generation at the contact was measured in contact resistance measurement. The heat generation was measured in terms of a temperature rise at a terminal portion for connecting the relay containing the contact material to the resistance measuring circuit. In this measurement, the temperatures of two terminals used as an anode-side terminal and a cathode-side terminal were measured at the time of elapse of 30 minutes after the start of continuous feeding of a current for the contact resistance measurement described above, an average of temperature differences between the measured temperature and room temperature was defined as a temperature rise ( C.). The above measurement and evaluation of the properties with the DC high-voltage relay were performed with n=1 to 3 for each contact material, and an average in each test was defined as a measured value.
[Evaluation of Durability in DC Low-Voltage Relay Simulation Tester]
[0102] Further, for the contact materials of examples and comparative examples, durability under use conditions in a conventional in-vehicle DC low-voltage relay was evaluated. This evaluation test was performed by the steps of incorporating each contact material in a DC low-voltage relay simulation tester, allowing an actuator to switch contacts, generating an input current for 0.1 seconds at the time of closing the contacts to thereby weld the contacts, and reading a force separating the welded contacts with a strain gauge at the time of opening the contacts. The conditions for the test are as follows.
[0103] Test voltage: DC 14 V
[0104] Input current: 115 A
[0105] Load: four halogen lamps (240 W)
[0106] Contact force: 20 gf
[0107] Test temperature: 20 C.
[0108] Number of operations: 10000 times
[0109] It can be determined that when the separating force in opening was more than 50 gf in the switching operation with the simulation tester, failure (interruption failure) resulting from welding occurred with an opening force in a conventional relay (50 gf or less). In this embodiment, durability was evaluated with a failure probability calculated from the number of measurements (10000 times) and the number of operations at which the separating force was more than 50 gf. Evaluation in the DC low-voltage relay simulation tester was performed with n=1 for each material.
[0110] Table 4 shows the results of the above interruption durability test, melting area measurement, contact resistance/heat generation measurement, and evaluation of the failure probability under use conditions for conventional relays.
TABLE-US-00004 TABLE 4 High-voltage evaluation Low-voltage evaluation Number of Contact Heat Failure Contact Opening inter- Melting resis- gener- Opening proba- Composition (mass %)*.sup.1 force force ruptions area tance ation force*.sup.3 bility Ag Sn Bi In Ni Te (gf) (gf) (times) (mm*.sup.2) (m) ( C.) (gf) (%) Example 1 Balance 4.70 0.10 75 125 98.67 0.13 1.86 22.23 50 15.91 Example 2 4.50 0.30 95.50 0.11 1.85 23.73 6.30 Example 3 4.40 0.50 100 0.09 2.16 25.47 11.71 Example 4 4.00 0.90 95.17 0.11 1.97 24.40 14.04 Example 5 3.90 0.90 0.10 92.83 0.09 2.03 24.54 8.45 Example 6 3.50 1.30 0.10 89.33 0.11 2.03 24.52 9.15 Example 7 3.10 1.70 0.10 72.67 0.14 2.23 26.32 3.42 Example 8 3.20 1.30 0.10 0.30 87.83 0.15 2.28 26.29 10.91 Example 9 2.90 0.10 66.67 0.22 1.46 20.79 13.90 Example 10 2.90 2.00 86.00 0.17 2.01 25.65 21.17 Example 11 3.40 2.00 100 0.16 2.09 27.36 14.31 Example 12 4.00 2.00 100 0.13 2.26 28.41 10.93 Example 13 4.50 1.50 100 0.15 2.35 28.67 5.72 Example 14 4.75 0.05 77.00 0.20 2.07 24.64 11.54 Example 15 4.70 0.10 100 0.08 1.46 20.48 13.69 Example 16 5.90 0.10 79.33 0.14 2.21 25.43 5.68 Example 17 2.80 0.10 100 0.15 2.48 28.77 25.49 Example 18 2.80 3.10 100 0.10 2.40 28.41 2.44 Example 19 3.40 0.80 92.00 0.11 1.94 24.80 15.45 Example 20 5.00 1.00 100 0.08 2.32 28.20 7.79 Example 21 2.80 1.50 0.50 84.50 0.16 2.33 28.81 2.32 Example 22 2.80 1.50 1.50 70.00 0.21 2.28 29.41 6.88 Example 23 2.80 1.50 0.10 0.10 100 0.12 1.58 23.22 6.52 Example 24 3.00 100 0.19 2.21 28.29 16.07 Example 25 4.80 81.00 0.15 2.26 28.73 21.13 Example 26 6.00 100 0.08 2.31 29.09 3.43 Example 27 4.00 0.80 76 0.20 2.04 26.26 1.40 Example 28 6.00 2.00 96.67 0.13 2.53 29.06 0.02 Example 29 7.90 0.10 100 0.09 2.66 28.75 0.77 Example 30 5.00 2.00 100 0.07 2.35 28.60 4.50 Example 31 7.00 1.00 100 0.08 2.67 29.51 13.40 Example 32 7.50 89.50 0.08 2.60 29.17 1.39 Comparative 9.50 100 0.05 2.93 31.47 0.27 Example 1 Comparative 10.50 0.90 100 0.05 3.61 33.79 0.00 Example 2 Comparative 7.40 4.00 0.10 0.50 100 0.06 7.86 53.80 0.84 Example 3 Comparative 3.00 3.00 100 0.15 3.30 35.60 1.60 Example 4 Comparative 5.00 4.00 93 0.11 3.65 36.62 1.81 Example 5 Comparative 2.00 7.00 100 0.06 4.11 42.44 0.00 Example 6 Comparative 3.40 0.80 0.10 2.50 22 1.93 2.93 32.53 4.40 Example 7 Comparative 9.70 30 0.35 2.45 26.31 2.42 Example 8 Comparative 3.20 1.30 1.50 2.00 *.sup.2 *.sup.2 *.sup.2 *.sup.2 *.sup.2 Example 9 Comparative 100 7.33 2.03. 1.01 17.90 21.34 Example 10 *.sup.1Concentration based on all metal components *.sup.2Sample processing was impossible *.sup.3The separating force at the time of opening in switching operation with a simulation tester was set to an opening force (50 gf)
[0111] From the evaluation results shown in Table 4, it can be confirmed that the contact materials of Examples 1 to 32 have a smaller amount of dispersed oxides as compared to comparative examples, but have good welding resistance when applied to DC high-voltage relays, and hardly suffer the problems of contact resistance and heat generation.
[0112] That is the contact materials of examples in this embodiment each satisfied the criterion which requires that the number of interruptions is 50 times or more in an interruption durability test at a high-voltage. Thus, the contact materials of examples had good interruption durability. At the same time, the contact materials of examples were confirmed to have lower contact resistance as compared to comparative examples. In particular, the contact materials of Example 1 to Example 27 had a particularly low contact resistance of 2.5 m or less. In addition, for each of the contact materials of Example 28 to Example 32, the number of interruptions in high-voltage evaluation is 80 times or more, and particularly good interruption durability was exhibited. The contact resistance of each of the contact materials of Example 28 to Example 32 was slightly high, but lower as compared to comparative examples.
[0113] Regarding the problem of heat generation, the results of measurement performed with the contact materials actually incorporated in the relays show superiority of the contact materials of examples. The contact materials of examples have a lower temperature rise value as compared to those of comparative examples. The amount of heat generation at contacts is proportional to a square of current and a contact resistance value. In the measurement test in this embodiment, a relatively low current of 30 A is fed, but when the fed current increases with the contact material applied to an actual DC high-voltage relay, the temperature rise further increases.
[0114] Further, for the results of evaluating the melting area, the melting area in this embodiment which is shown in Table 4 is a value obtained by dividing the total of area change amounts of the surfaces of four contacts after the interruption test by the number of interruptions at the contacts (a maximum of 100 times) as described above. That is, the melting area here means a melting area per interruption. In practical use, principal interruption of the relay occurs only once at the time of abnormality, and it is assumed to be necessary that the number of interruptions with a margin be 5 times taken into consideration. Based on this assumption, for example, the contact material of Example 9 with the largest melting area among the contact materials of Examples 1 to 32 has a melting area of 0.22 mm.sup.2, and therefore five interruptions may change the area of the contact surface by 1.10 mm.sup.2 (0.22 mm.sup.25). The area of the contact surface before the test in terms of a total of four contacts is 32.68 mm.sup.2 (7.79 mm.sup.22 +8.55 mm.sup.22), and therefore the ratio of change of the area of the contact surface, which is caused by five interruptions, is 3.37% (1.10 mm.sup.2/32.68 mm.sup.2). Thus, in the contact materials of the examples, the area change at the time of interruption can be limited to 10% or less in practical use.
[0115] Metal M of the contact material that is applied in the present invention essentially has Sn, and may contain metals other than Sn (Bi, In, Ni and Te). Table 4 shows that when a contact material containing only Sn as metal M (e.g. Example 24) is set to a standard, contact materials containing Bi or the like together with Sn (e.g. Example 9 (Sn+Bi), Example 19 (Sn+In) and Example 23 (Sn+In+Ni+Te)) tend to have lower contact resistance while exhibiting good results for interruption durability and the melting area in comparison with the standard. Hence, it is confirmed that metals M other than Sn (Bi, In, Ni and Te) have an effect. A DC high-voltage relay carrying such a contact material containing a plurality of metals can also maintain required contact performance. However, it was confirmed that when a large amount of metal M other than Sn was added as in Comparative Example 9 where Ni was added a lot, processability deteriorated.
[0116] However, the results of low-voltage evaluation which gives consideration to application to conventional DC low-voltage relays show that in terms of a failure probability, the contact materials of Example 1 to Example 26, 30 and 31 are not suitable for DC low-voltage relays. This is because the contact materials of these examples tend to have a higher failure probability as compared to comparative examples. That is, the contact materials of Examples 1 to Example 26, 30 and 31 are shown to exhibit their usefulness when used in proper applications that are DC high-voltage relays. On the other hand, the contact materials of Examples 28, 29 and 32 are comparative to the contact materials of comparative examples in failure probability in low-voltage evaluation. However, the contact materials of these examples have a low contact resistance value in high-voltage evaluation, and are therefore suitable for DC high-voltage relays as well.
[0117] With respect to the contact materials of examples examined above, the contact materials of comparative examples had a large amount of oxides, and were therefore excellent in interruption durability and melting area in high-voltage evaluation. However, the contact materials of comparative examples had high values of contact resistance and heat generation. Therefore, DC high-voltage relays including the contact materials having a large amount of oxides may have the problem of heat generation at contacts.
Second Embodiment
[0118] In this embodiment, contact materials were manufactured by the internal oxidation method and the powder metallurgy method. After structure observation and hardness measurement for the materials, DC high-voltage relays (contact force/opening force: 500 gf/250 gf) were manufactured, and evaluation of durability and measurement and evaluation of contact resistance were performed. Table 5 shows contact materials manufactured in this embodiment. Table 5 also shows the results of measuring hardness measured in the same manner as in the first embodiment. The contact materials manufactured by the internal oxidation method and were manufactured in the same steps as in the first embodiment.
TABLE-US-00005 TABLE 5 Composition (mass %)*.sup.1 Hardness Ag Sn Bi In Ni Te (Hv) Example 33 Balance 0.20 82 Example 34 4.80 76 Example 35 3.10 0.10 104 Example 36 4.00 0.90 72 Example 37 2.90 0.10 102 Example 38 2.90 2.00 82 Example 39 0.10 5.00 87 Example 40 1.50 3.80 86 Example 41 2.80 0.10 106 Example 42 2.80 1.50 0.50 99 Example 43 0.50 89 Example 44 1.00 100 Example 45 3.00 108 Example 46 0.10 0.10 52 Example 47 0.10 2.00 60 Example 48 0.10 0.10 70 Example 49 3.00 5.00 89 Example 50 3.00 0.05 5.00 86 Comparative 7.40 4.00 0.10 0.50 98 Example 3 Comparative 0.10 71 Example 11 Comparative 100 50 Example 10 The contact materials of Examples 34 and 36 were manufactured by the powder metallurgy method, and the contact materials of other examples were manufactured by the internal oxidation method. *.sup.1Concentration based on all metal components
[0119]
TABLE-US-00006 TABLE 6 Dispersion state of oxide particles Particle Average size particle standard Composition (mass %)*.sup.1 Area ratio size deviation Ag Sn Bi In Ni Te (%) (m) (m) Example 36 Balance 4.00 0.90 8.58 0.113 0.101 Example 39 0.10 5.00 8.39 0.164 0.128 Example 40 1.50 3.80 7.81 0.149 0.097 Example 43 0.50 0.13 0.058 0.028 Example 44 1.00 0.23 0.040 0.015 Example 47 0.10 2.00 0.99 0.145 0.123 Example 49 3.00 5.00 12.14 0.219 0.136 *.sup.1Concentration based on all metal components
[0120] For the contact materials of the examples, an interruption durability test was conducted in a DC high-voltage relay. The details of the test were basically the same as in the first embodiment, and the same DC high-voltage relay of double-break structure was used. The test conditions were the same as in the first embodiment. However, the contact force/opening force of the movable contact was 500 gf/250 gf, and the contact force and the opening force were higher as compared to the first embodiment. In this embodiment, a DC high-voltage relay was manufactured in which a further sufficient contact force and opening force were set. In this interruption durability test, the number of interruptions was measured while the upper limit of the number of interruptions was set to 100.
[0121] In addition, the melting area for the contact material after the interruption durability test was measured. Further, the contact resistance values and heat generation for the contact materials were measured. The measurement methods were the same as in the first embodiment. In this embodiment, the contact materials of Comparative Examples 3 and 10 in the first embodiment were subjected to the same interruption durability test and evaluated, for comparison. Further, the interruption durability test was conducted for a contact material in which the content of metal M was below the lower limit (0.2% by mass) specified in the present invention. Table 7 shows the results of the above measurement and evaluation.
TABLE-US-00007 TABLE 7 High-voltage evaluation Contact Opening Number of Melting Contact Heat Composition (mass %)*.sup.1 force force interruptions area resistance generation Ag Sn Bi In Ni Te (gf) (gf) (times) (mm.sup.2) (m) ( C.) Example 33 Balance 0.20 500 250 100 0.35 0.67 14.36 Example 34 4.80 100 0.20 1.29 19.66 Example 35 3.10 0.10 100 0.19 1.56 20.30 Example 36 4.00 0.90 100 0.21 1.77 21.94 Example 37 2.90 0.10 100 0.46 0.81 18.11 Example 38 2.90 2.00 100 0.34 0.73 16.66 Example 39 0.10 5.00 100 0.27 1.19 20.02 Example 40 1.50 3.80 100 0.27 1.25 20.68 Example 41 2.80 0.10 90 0.36 0.66 15.12 Example 42 2.80 1.50 0.50 100 0.27 1.42 22.31 Example 43 0.50 100 0.57 0.75 16.60 Example 44 1.00 100 0.38 1.25 21.45 Example 45 3.00 100 0.38 0.65 17.11 Example 46 0.10 0.10 96.00 0.63 0.67 16.50 Example 47 0.10 2.00 76.25 0.63 0.87 16.93 Example 48 0.10 0.10 100 0.45 0.61 14.53 Example 49 3.00 5.00 100 0.10 2.10 26.75 Example 50 3.00 0.05 5.00 100 0.12 2.18 27.35 Comparative 7.40 4.00 0.10 0.50 100 0.05 3.49 32.43 Example 3 Comparative 0.10 81 1.48 0.60 15.43 Example 11 Comparative 100 47.50 2.51 0.65 15.79 Example 10 *.sup.1Concentration based on all metal components
[0122] From Table 7, it is understandable that DC high-voltage relays including the contact materials of Example 33 to Example 50 in this embodiment have good interruption durability. The contacts of the DC high-voltage relays have low contact resistance, and are free from the heat generation problem. These relays satisfy the criterion which requires that the number of interruptions is 50 times or more. These relays have a low contact resistance of 2.5 m, and a low heat generation amount. In addition, in evaluation for the melting area, evaluation of the contacts of Examples 46 and 47 with the largest melting area (0.63 mm.sup.2) in the same manner as in the first embodiment shows that if interruption occurs five times, the ratio of change of the area of the contact surface is 9.6%, and thus the ratio of change of the area is limited to 10% or less.
[0123] On the other hand, the contact material of Comparative Example 3 is excellent in interruption durability and melting area as with the results in the first embodiment. However, the contact material has a high contact resistance value, and an evidently large temperature rise value in heat generation, and is therefore considered to hinder application of a DC high-voltage relay when mounted in the DC high-voltage relay.
[0124] The contact material of Comparative Example 11 is a contact material in which the content of metal M is below the lower limit (0.2% by mass) specified in the present invention. This contact material has low contact resistance, and a low heat generation amount. However, the melting area of the contact is excessively large. For the melting area (1.48 mm.sup.2) in Comparative Example 11, evaluation performed in the same manner as in the first embodiment shows that provided that interruption occurs five times, the ratio of change of the area of the contact surface is 22.6%, and thus the ratio of change of the area is extremely high. When the melting area increases as described above, the contact shape markedly collapses. When the contact shape is collapsed, normal contact is not performed at a contact pair after the relay is returned, and thus contact failure occurs. This result is also observed in the contact material of Comparative Example 10 (pure Ag), and the Ag oxide contact material of Comparative Example 11 is substantially the same as pure Ag.
[0125] The contact material of Comparative Example 11 satisfies the criterion for the number of interruptions in the interruption durability test, and this is ascribable to a higher contact force and opening force as compared to the first embodiment. It is considered that when the contact force and the opening force are equivalent to the contact force and the opening force in the first embodiment, interruption failure occurs due to early welding as in Comparative Example 10. This shows that reduction of the amount of oxides in the contact material applied to the DC high-voltage relay is allowable only with limitations.
[0126] It is understandable from the results of the above examples that by optimizing the content of oxides (content of metal M) in the contact material of the contact pair in the DC high-voltage relay in which a sufficient contact force and opening force are set, excellent interruption durability is exhibited, and moreover, the problems of contact resistance and heat generation can be solved.
[0127] Third Embodiment: In the first and second embodiments, DC high-voltage relays of double-break structure containing various contact materials (
[0128] Normal use conditions of the DC high-voltage relay which are intended by the present invention will be described in detail. In DC circuits for hybrid vehicles and the like, a precharge relay appropriate to an inrush current is installed for preventing damage of contacts of a system main relay by a high inrush current at the time when a power source is turned on. After the precharge relay absorbs the high inrush current, the power source of the system main relay is turned on.
[0129] In this embodiment, a capacitor load durability test was conducted in which the same DC high-voltage relay as in the first and second embodiments was incorporated in a test circuit as shown in
[0130] In this embodiment, the contact resistance and the temperature rise (heat generation amount) were measured as in the first and second embodiments. After the capacitor load durability test, the contact resistance was measured with a change made to connection of the relay to a resistance measuring circuit (DC5V30A) which is different from a capacitor load durability test circuit. The measurement method was the same as in the first embodiment. In addition, a temperature rise caused by heat generation at the contact was measured in the contact resistance measurement. The measurement and evaluation of the properties in this embodiment were performed with n=1 for each contact material.
[0131] Table 8 shows the results of evaluating the durability life and measuring the contact resistance and the temperature rise in the capacity load durability test in this embodiment.
TABLE-US-00008 TABLE 8 High-voltage evaluation Contact Opening Contact Heat Composition (mass %)*.sup.1 force force Durability resistance generation Ag Sn Bi In Ni Te (gf) (gf) life (m) ( C.) Example 1 Balance 4.70 0.10 75 125 Acceptable 1.92 26.64 Example 4 4.00 0.90 Acceptable 2.12 26.30 Example 5 3.90 0.90 0.10 Acceptable 1.94 25.43 Example 8 3.20 1.30 0.10 0.30 Acceptable 2.27 27.71 Example 9 2.90 0.10 Acceptable 1.18 21.76 Example 10 2.90 2.00 Acceptable 2.31 27.40 Example 16 5.90 0.10 Acceptable 1.41 22.14 Example 19 3.40 0.80 Acceptable 1.28 21.47 Example 23 2.80 1.50 0.10 0.10 Acceptable 1.41 22.64 Example 26 6.00 Acceptable 1.74 23.72 Example 32 7.50 Acceptable 1.95 26.21 Comparative 7.40 4.00 0.10 0.50 Acceptable 6.96 56.57 Example 3 Example 33 0.20 Acceptable 0.54 16.30 Example 37 2.90 0.10 Acceptable 0.91 17.36 Comparative 7.40 4.00 0.10 0.50 500 250 Acceptable 1.57 24.07 Example 3 *.sup.1Concentration based on all metal components
[0132] Table 8 reveals that the DC high-voltage relays of examples were acceptable for the durability life in the load during normal use (number of operations: 100,000 times). In addition, the DC high-voltage relays had low contact resistance, and were acceptable for the heat generation amount. On the other hand, in the DC high-voltage relay of Comparative Example 3 with a large amount of oxides in the contact material, the contact resistance and the heat generation amount were high.
[0133] From the results of the above first to third embodiments, it was confirmed that the DC high-voltage relay according to the present invention operates suitably as a DC high-voltage relay due to optimization of the configurations of the contact materials of the movable contact and the fixed contact. The DC high-voltage relay according to the present invention can effectively operate with respect to interruption upon abnormal operations of the circuit, and stably operate in normal use.
INDUSTRIAL APPLICABILITY
[0134] The Ag oxide-based contact material that is applied in the DC high-voltage relay according to the present invention exhibits an excellent interruption durability property, has low contact resistance, and generates a small amount of heat. The DC high-voltage relay according to the present invention is free from the problems of heat generation and welding at contact pair, and can perform reliable on/off control. The present invention is suitably applied to system main relays in power source circuits of high-voltage batteries in hybrid vehicles and the like, power conditioners in power supply systems such as solar power generation equipment, and the like.