Rolling bearing with rotation sensor

Abstract

A rolling bearing with a rotation sensor includes an inner race and an outer race, one of which is a rotating race and the other of which is a stationary race. An annular magnetic encoder alternately magnetized in opposite polarities in its circumferential direction is mounted on the rotating race. A magnetic sensor configured to detect the changes in magnetic flux when the magnetic encoder is rotated is mounted in a resin sensor housing mounted on the stationary race. The sensor housing is made of a resin material including a resin composition containing polyphenylene sulfide, an inorganic filler, and glass fiber.

Claims

1. A rolling bearing with a rotation sensor comprising: an inner race: an outer race, wherein one of the inner race and the outer race is a rotating race and the other of the inner race and the outer race is a stationary race; an annular magnetic encoder alternately magnetized in opposite polarities in a circumferential direction of the magnetic encoder and mounted on the rotating race; a metal outer ring attached to the stationary race; a magnetic sensor retained within the metal outer ring, the magnetic sensor being configured to detect changes in magnetic flux when the magnetic encoder is rotated, and being arranged to oppose the magnetic encoder in a radial direction of the rolling bearing; and a resin sensor housing in which is mounted the magnetic sensor and mounted on the metal outer ring; wherein the sensor housing is formed of a resin material which is a resin composition containing polyphenylene sulfide, an inorganic filler, and glass fiber.

2. The rolling bearing with a rotation sensor according to claim 1, wherein the inorganic filler is calcium carbonate.

3. The rolling bearing with a rotation sensor according to claim 2, wherein the resin material comprises 20% by weight or more and 30% by weight or less of the inorganic filler, and 20% by weight or more and 30% by weight or less of the glass fiber, with respect to the total amount of the resin material.

4. The rolling bearing with a rotation sensor according to claim 1, wherein the resin material comprises 20% by weight or more and 30% by weight or less of the inorganic filler, and 20% by weight or more and 30% by weight or less of the glass fiber, with respect to the total amount of the resin material.

5. A rolling bearing with a rotation sensor comprising: an inner race: an outer race, wherein one of the inner race and the outer race is a rotating race and the other of the inner race and the outer race is a stationary race; an annular magnetic encoder alternately magnetized in opposite polarities in a circumferential direction of the magnetic encoder and mounted on the rotating race; a magnetic sensor configured to detect changes in magnetic flux when the magnetic encoder is rotated, the magnetic sensor being arranged to oppose the magnetic encoder in a radial direction of the rolling bearing; and a resin sensor housing in which is mounted the magnetic sensor and mounted on the stationary race; wherein the sensor housing is formed of a resin material which is a resin composition containing polyphenylene sulfide, an inorganic filler, and glass fiber; and wherein the resin material comprises 20% by weight or more and 30% by weight or less of the inorganic filler, and 20% by weight or more and 30% by weight or less of the glass fiber, with respect to the total amount of the resin material.

6. The rolling bearing with a rotation sensor according to claim 5, wherein the inorganic filler is calcium carbonate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front view of a rolling bearing with a rotation sensor embodying the present invention.

(2) FIG. 2 is a cross sectional view taken along line II-II in FIG. 1.

(3) FIG. 3 is a cross sectional view taken along line III-III in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

(4) An embodiment of the present invention will be described with reference to the drawings.

(5) The rolling bearing with a rotation sensor according to the present invention includes: an inner race; an outer race, wherein one of the inner race and the outer race is a rotating race and the other is a stationary race; an annular magnetic encoder alternately magnetized in opposite polarities in the circumferential direction and mounted on the rotating race; a magnetic sensor configured to detect the changes in magnetic flux when the magnetic encoder is rotated; and a resin sensor housing in which is mounted the magnetic sensor and mounted on the stationary race.

(6) The above described rolling bearing with a rotation sensor will be described with reference to the rolling bearing shown in FIGS. 1 to 3, as an example.

(7) The rolling bearing with a rotation sensor shown in FIGS. 1 to 3 is a deep groove ball bearing including: an inner race 1, which is a rotating race; an outer race 2, which is a stationary race; and balls 3 disposed between the inner race 1 and the outer race 2 and retained by a retainer 4. This rolling bearing includes a rotation sensor portion formed by: fixedly mounting a magnetic encoder 6 on the radially outer surface of the inner race 1; fixing an outer ring 10 on the radially inner surface of the outer race 2 facing the inner race 1; press-fitting a sensor housing 9 to the inner peripheral surface of the outer ring 10, mounting magnetic sensors 7, a circuit board 8, electrical wires and the like in the sensor housing 9; sealing the opening around the magnetic sensors 7 with a molded resin 12; and fixing a side plate 11 placed over the molded resin 12 by caulking with claws at three locations.

(8) Further, a sealing member 5 for sealing the interior of the bearing is mounted on the side of the outer race 2 opposite from the sensor housing 9.

(9) The molded resin 12 is a thermosetting resin. The thermosetting resin may be an epoxy resin or urethane resin. The magnetic encoder 6 is formed by press molding a thin metal plate into a ring, and bonding a magnetic rubber thereto by vulcanized adhesion, followed by magnetizing the ring in the radial direction such that north poles and south poles are alternately arranged in the circumferential direction.

(10) Further, the two magnetic sensors 7 are disposed adjacently in the circumferential direction of the sensor housing 9 so as to face the magnetic encoder 6 in the radial direction.

(11) As shown in FIG. 3, the two magnetic sensors 7 are disposed at two locations adjacent to each other in the circumferential direction of the sensor housing 9 so as to face the magnetic encoder 6 in the radial direction, and an output cable 13 connected to the magnetic sensors 7 extends outside the bearing through a tubular cable duct 14 formed integrally with the sensor housing 9. The magnetic sensors 7, the circuit board 8 and the output cable 13 mounted in the sensor housing 9 are fixed in position in the molded resin 12. The two magnetic sensors 7 are disposed adjacently in the circumferential direction so that the direction of rotation can be detected from the time delay between the detection outputs of these two magnetic sensors 7.

(12) The sensor housing 9 is made of a resin material comprising a resin composition containing polyphenylene sulfide (PPS), an inorganic filler, and glass fiber. The sensor housing 9 is covered with the outer ring 10 and the side plate 11, which are formed by press molding a metal plate, such as a magnetic ferritic stainless steel plate, SUS430, and with the side plate 11, in order to shield the sensor housing 9 from harmful external magnetic field and to prevent corrosion. The outer ring 10 is fixedly fitted to the radially inner surface of the outer race 2, and a sealing portion 10a for sealing the interior of the bearing is formed at the inner end of the outer ring 10.

(13) Inorganic fillers usable in the present invention include: carbonates such as calcium carbonate; hydroxides such as hydroxide calcium; sulfates such as barium sulfate; oxides such as silica and alumina; and silicates such as talc, mica and wollastonite.

(14) The content of the inorganic filler contained in the resin composition forming the sensor housing 9 is preferably 20% by weight or more, and more preferably, 22% by weight or more. If the content of the inorganic filler is less than 20% by weight, the effect of reducing the creep of the sensor housing due to temperature change tends to be insufficient, and thus the effect of the present invention may not be sufficiently exhibited. The upper limit of the content of the inorganic filler, on the other hand, is preferably 30% by weight, and more preferably, 28% by weight. If the content is greater than 30% by weight, the effect of reducing the creep of the sensor housing due to temperature change tends to be insufficient, and thus the effect of the present invention may not be sufficiently exhibited.

(15) The content of the glass fiber contained in the resin composition forming the sensor housing 9 is preferably 20% by weight or more, and more preferably, 22% by weight or more. If the content of the glass fiber is less than 20% by weight, the effect of reducing the creep of the sensor housing due to temperature change tends to be insufficient, and thus the effect of the present invention may not be sufficiently exhibited. The upper limit of the content the glass fiber, on the other hand, is preferably 30% by weight, and more preferably, 28% by weight. If the content is greater than 30% by weight, the effect of reducing the creep of the sensor housing due to temperature change tends to be insufficient, and thus the effect of the present invention may not be sufficiently exhibited.

(16) The resin material forming the sensor housing 9 may include about several percent by weight of a rubber material, as necessary.

(17) In the above mentioned embodiment, a deep groove ball bearing in which the inner race is designed as the rotating race is described. However, the rolling bearing with a rotation sensor according to the present invention may be a different type of rolling bearing, such as a roller bearing, or a rolling bearing in which the outer race is designed as the rotating race. In the latter case, the magnetic encoder of the rotation sensor is mounted on the outer race, and the sensor housing in which is mounted the magnetic sensor is mounted on the inner race.

EXAMPLES

(18) The present invention will now be described specifically by way of Examples.

Example 1, Comparative Examples 1 and 2

(19) The resin materials for forming the sensor housing with the compositions shown in Table 1 were used to form samples in the actual shape of the sensor housing. The thus obtained samples were subjected to thermal shock test, followed by measuring the shrinkage rates of the outer diameters of the samples.

(20) The results of the thermal shock test are shown below.

(21) [Thermal Shock Test]

(22) One cycle consisting of the temperature change conditions as shown below was repeated 500 times.
40 C.60 min.fwdarw.room temperature10 min.fwdarw.120 C.60 min.fwdarw.room temperature10 min

(23) TABLE-US-00001 TABLE 1 Comparative Example Examples 1 1 2 PPS (% by weight) 50 35 60 PAI (% by weight) 25 Calcium carbonate (% by weight) 25 Glass fiber (% by weight) 25 40 40
(Results)

(24) In Example 1, 20 samples were prepared and subjected to the thermal shock test. The results revealed that the shrinkage rates of the thicknesses of the samples were within the range of from 0% to 15%.

(25) In Comparative Example 1, on the other hand, 10 samples were prepared and subjected to the thermal shock test. The results revealed that the shrinkage rates of the thicknesses of the samples varied in a broad range of from 25% to 130%.

(26) In Comparative Example 2, 10 samples were prepared and subjected to the thermal shock test. The results revealed that the shrinkage rates of the thicknesses of the samples varied in a broad range of from 60% to 140%.

(27) (Observation)

(28) If the shrinkage rate of the sensor housing 9 due to thermal disturbance (thermal shock test) is high, it causes an increase in the gap between the outer ring 10 and the sensor housing 9, as compared to the case in which the shrinkage rate is low. In such a case, accordingly, there is a possibility that the sensor housing 9 moves unexpectedly within the outer ring 10 due to vibrations or the temperature change during the rotation of the bearing, which could cause an undesirable decrease in the accuracy of the rotation signal. Based on the above, Example 1 embodying the present invention, which has a low shrinkage ratio, is thought to be capable of exhibiting a sufficient creep resistance.

DESCRIPTION OF SYMBOLS

(29) 1 inner race 2 outer race 3 balls 4 retainer 5 sealing member 6 magnetic encoder 7 magnetic sensors 8 circuit board 9 sensor housing 10 outer ring 10a seal portion 11 side plate 12 molded resin 13 output cable 14 cable duct