HEATER AND METHOD OF MANUFACTURING SAME

Abstract

Provided is a heater in which heater patterns are provided in parallel between terminals. Each terminal is divided into a divided terminal having electrical conduction only with one heater pattern, and a divided terminal having electrical conduction only with the other heater pattern. After a heater body is fabricated, in a state prior to mounting a feed bolt, resistance adjustment is performed with respect to each of a virtual series path formed between the divided terminals and a virtual series path formed between the divided terminals. Then the feed bolt is mounted to each terminal, whereby a plurality of virtual series heater patterns are placed in electrical conduction with each other, thus forming a parallel circuit.

Claims

1. A parallel-type heater wherein a plurality of heater patterns are formed in parallel between a pair of terminals to which power supply bolts are fitted respectively the parallel-type heater comprising: each of said pair terminals is divided into a plurality of spaced segmental terminals of the same number as said plurality of heater patterns, said plurality of segmental terminals being electrically connected with each other by said power supply bolt, a plurality of imaginary serial heater patterns arc formed between one of said segmental terminals divided from one of said pair of terminals and one of said segmental terminals divided from the other pair of terminals when said power supply bolts are not yet fitted, said plurality of imaginary serial heater patterns being electrically connected with each other to form parallel circuits when said power supply bolts are fitted.

2. The parallel-type heater of claim 1 wherein a head of said power supply bolt is in contact with a heater element forming said heater pattern directly or via a washer made by conductive material.

3. The parallel-type heater of claim 1 wherein first and second heater patterns are formed in parallel between a pair of said pair of terminals, each terminal being divided into a first segmental terminal to be electrically connected only with a first heater pattern of said plurality of heater patterns and a second segmental terminal to be electrically connected only with a second heater pattern of said plurality of heater patterns.

4. The parallel-type heater of claim 3 wherein each of said first and second segmental terminals is formed in substantially a semicircular ring shape, said first and second heater patterns being insulated with each other by a gap extending in a radial direction between said segmental terminals.

5. The parallel-type heater of claim 1 wherein first to fourth heater patterns are formed in parallel between the pair of said terminals, each terminal being divided into a first segmental terminal to be electrically connected only with said first heater pattern, a second segmental terminal to be electrically connected with said second heater pattern, a third segmental terminal to be electrically connected with said third heater pattern and a fourth segmental terminal to be electrically connected only with said fourth heater pattern.

6. The parallel-type heater of claim 5 wherein each of said first to fourth segmental terminals is formed in substantially a quadrant ring shape, said first to fourth heater patterns being insulated with each other by gaps extending in radial and circumferential directions between said segmental terminals.

7. A production of the parallel-type heater of claim 1, comprising: producing a heater body having a plurality of heater patterns in parallel between a pair of terminals, performing resistance adjustment for each of said imaginary serial heater patterns formed between one segmental terminal of one terminal and one segmental terminal of the other terminal before fitting said power supply bolts to said terminals, and then fitting said power supply bolts to said terminals so that said plural imaginary serial heater patterns become electrically connected with each other to form a parallel circuit.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0023] FIG. 1 is an overall plan view of a parallel-type heater (in a complete state where the power supply bolts are fitted) according to an embodiment (Embodiment 1) of the present invention.

[0024] FIG. 2(a) is an enlarged plan view showing a part around the terminal of FIG. 1 and (b) is a cross-section taken along the section line I-I in (a).

[0025] FIG. 3 is an overall plan view of the heater in a state where the power supply bolts are removed.

[0026] FIG. 4(a) is an enlarged plan view showing a part around the terminal of FIG. 3 and (b) is a cross-section taken along the section line II-II in (a).

[0027] FIG. 5 is an explanatory view showing the manner of resistance adjustment for the heater of FIG. 3 and FIG. 4.

[0028] FIG. 6 is an overall plan view of a parallel-type heater according to another embodiment (Embodiment 2) of the present invention, which is shown in a state where the power supply bolts are removed as in FIG. 3

[0029] FIG. 7 is an overall plan view of a serial-type heater according to the prior art.

[0030] FIG. 8 is an overall plan view of a parallel-type heater according to the prior art.

[0031] FIG. 9(a) is an overall plan view showing the serial-type heater of FIG. 7 in which resistance measurement points are plotted and (b) is an explanatory view showing the manner of resistance adjustment for this heater.

[0032] FIG. 10(a) is an overall plan view showing the parallel-type heater of FIG. 8 in which resistance measurement points are plotted and (b) is an explanatory view showing the manner of resistance adjustment for this heater.

[0033] FIG. 11 is an explanatory view showing, by way of example, that it is difficult to conduct resistance adjustment for the parallel-type heater of FIG. 8.

EMBODIMENTS OF INVENTION

[0034] The present invention will be described in detail in reference to some embodiments thereof.

Embodiment 1

[0035] FIG. 1 and FIG. 2 show a parallel-type heater 30 according to one embodiment (Embodiment 1) of the present invention. In this heater 30, symmetrically designed heater patterns 31, 32 are formed between terminals A, B.

[0036] This heater 30 comprises a heater body 36 of a triple-layered structure comprising a disc-shaped heater base 33, at least its front and back surfaces being made from insulating material such as PBN (pyrolytic boron nitride, including one into which a small amount of carbon is incorporated), heater element 34 made from conductive material such as PG (pyrolytic graphite) forming the heater patterns 31, 32 (their center lines being shown by dashed lines), and an overcoat 35 made from insulating material such as PBN. The heater body 36 may be manufactured by a routine procedure comprising the steps of vapor-depositing heater element 34 onto the heater base 33, partly removing the heater element to form the heater patterns 31, 32, forming the overcoat 35 thereon, and then removing opposite end portions of the overcoat 35 to expose the heater element 34 to thereby form the terminals A, B. The overcoat 35 is shown in FIG. 2(b) but omitted in FIG. 1 and FIG. 2(a).

[0037] Each terminal A, B is divided into two segmental terminals 37, 38 each having a semicircular ring shape, and includes a power supply bolt 40 inserted into a bolt hole 39 extending through the heater base 33, a nut 41 for fastening the power supply bolt 40 with the heater body 36 being interposed therebetween, and washers 42, 43. The segmental terminal 37 is electrically connected only with the heater pattern 31, whereas the segmental terminal 38 is electrically connected only with the heater pattern 32. The segmental terminals 37, 38 are separated and insulated from each other by a gap 44 extending in a radial direction, but once the power supply bolt 40 is fitted, a head 40a of the power supply bolt 40 becomes in contact with both of the segmental terminals 37, 38 via the washer 42 so that the heater patterns 31, 32 becomes electrically connected with each other to form the parallel-type heater 30. The power supply bolt 40 and the washer 42 are made from insulating material such as PBN. The washer 43 may be of insulating or non-insulating material.

[0038] FIG. 3 and FIG. 4 show the above-constructed parallel-type heater 30 in a state where the power supply bolt 40 is removed (or a halfway state during production of the heater 30 where the heater body 36 has been obtained but the power supply bolt 40 is not yet fitted). As described before, in this state, the segmental terminal 37 and the segmental terminal 38 are insulated from each other by the gap 44, so that the heater pattern 31 is formed between the segmental terminals 37, 37 of the terminals A, B, and the heater pattern 32 is formed between the segmental terminals 38, 38 of the terminals A, B, each forming a serial heater route 45, 46. Accordingly, in this state, the resistance adjustment can be performed easily in the same way as for the aforementioned serial-type heaters 10 (FIG. 7).

[0039] The measurement points P21 to P24 are plotted along the heater patterns 31, 32 in the same way as in the aforementioned conventional parallel-type heater 20 (FIG. 8), and the resistance adjustment can be performed in the following manner, which will now be described in reference to FIG. 5. In this example, the resistance value of the heater 30 by design is 1.61 ohms (meaning that the resistance values of the routes 45, 46 are both 3.22 ohms), wherein a section between the terminal A and the measurement point P1 should have a sectional resistance value r21=1.26 ohms, a section between the measurement points P21 and P22 should have a sectional resistance value r22=1.19 ohms, a section between the measurement point P22 and the terminal B should have a sectional resistance value r23=0.77 ohms, a section between the terminal B and the measurement point P23 should have a sectional resistance value r24=1.26 ohms, a section between the measurement points P23 and P24 should have a sectional resistance value r25=1.19 ohms, and a section between the measurement point P24 and the terminal A should have a sectional resistance value r25=0.77 ohms (each sectional resistance value r21 to r25 is a reference value after being adjusted).

[0040] In the state where the power supply bolt 40 is not yet fastened, the route 45 is a serial route from the terminal A to the terminal B. Accordingly, in the same way as in the resistance adjustment for the serial-type heater 10 (FIG. 7) which has been described in reference to FIG. 9, it is possible to measure the resistance values between the terminal A and the measurement points P21, P22 and the terminal B and then adjust them sequentially to become equal to the respective reference values. Likewise, the resistance adjustment may be performed for the route 46 as well. Thus, the resistance adjustment may be carried out relatively easily. In practice, the element of the heater patterns 31, 32 is formed at first a little bit thicker to provide a resistance value of a little bit smaller than the design resistance value, which should then be partly scraped depending upon the resistance values measured at the respective measurement points for the resistance adjustment.

[0041] After the resistance adjustment has been performed for the imaginary serial routes 45, 16 in the above-described manner, the power supply bolt 40, the nut 41 and the washers 42, 43 are fitted to each terminal A, B. Thus, as described before, a head 40a of the power supply bolt 40 becomes in contact with both of the segmental terminals 67, 38 via the washer 42 so that the heater patterns 31, 32 becomes electrically connected with each other to thereby form the parallel-type heater 30.

Embodiment 2

[0042] The above-described parallel-type heater 30 according to Embodiment 1 has two heater patterns 31, 32 in parallel between a pair of terminals A, B and therefore is designed such that each terminal A, B is divided into two segmental terminals 37, 38 separated by the radially-extending gap 44. However, in case where more definite temperature control is required for a larger heater, for example, it may be designed such that a greater number of heater patterns, for example four heater patterns are formed in parallel between a pair of terminals A, B.

[0043] An example of such design is shown in FIG. 6. This parallel-type heater 50 has four heater patterns 51-54 formed between terminals A, B, and each terminal A, B is divided into four segmental terminals 55-58. The heater pattern 51 (its center line being shown by a dashed line) is formed between the segmental terminals 55, 55 of the terminals A, B, the heater pattern 52 (its center line being shown by a broken line) is formed between the segmental terminals 56, 56 of the terminals A, B, the heater patterns 53 (its center line being shown by a dashed line) is formed between the segmental terminals 57, 57 of the terminals A, B, and the heater patterns 54 (its center line being shown by a broken line) is formed between the segmental terminals 58, 58 of the terminals A, B. Each segmental terminal 55-58 is formed in a quarter-circular ringed shape, which is separated from each other by gaps 59 extending in radial and peripheral directions.

[0044] Although the present invention has been described in detail in reference to the embodiments thereof, it is not limited thereto and may be implemented in various modified applications. For example, although the heater patterns 31, 32 (the routes 45, 46) becomes electrically connected with each other via the washer 42 when the power supply bolt 40 is fitted in Embodiment 1, it may also be designed that the bottom of the power supply bolt head 40a be in contact with the heater patterns 31, 32 directly, which will require no washer 42. For a single heater having plural terminal pairs, each terminal of each pair is divided into a plural numbers of, for example, two (Embodiment 1) or four (Embodiment 2) segmental terminals, the number thereof being corresponding to the number of the heater patterns formed in parallel between the terminals, so that imaginary serial patterns can be formed until the power supply bolts are fitted.

LEGENDS

[0045] 10 serial-type heater (prior art) [0046] 20 parallel-type heater (prior art) [0047] 30 parallel-type heater (embodiment of the present invention) [0048] 31, 32 parallel heater pattern [0049] 33 heater base [0050] 34 heater element [0051] 35 overcoat [0052] 36 heater main body [0053] 37, 38 segmental terminal (divided into two) [0054] 39 bolt hole [0055] 40 power supply bolt [0056] 41 nut [0057] 42 washer [0058] 43 washer [0059] 44 gap [0060] 45,46 route [0061] 50 parallel-type heater (embodiment of the present invention) [0062] 51-54 parallel heater pattern [0063] 55-58 segmental terminal (divided into four) [0064] 59 gap