Seal member

Abstract

A seal member (90) for sealing between an outer circumferential surface of a steering shaft (11) and an inner circumferential surface of an accommodation part (81) in which the steering shaft (11) is accommodated comprises: an annular body section (91) that is provided between the outer circumferential surface of the steering shaft (11) and the inner circumferential surface of the accommodation part (81); and a filter (99) that transmits gas but does not transmit liquid. The body section (91) has formed therein a ventilation part (97) that penetrates the body section (91) in the axial direction, and the filter (99) is provided in the ventilation part (97).

Description

Sealing material

[0001] The present invention relates to a seal member.

[0002] JPH10-258749A discloses an electric power steering device that includes a pinion shaft, a rack shaft that meshes with a pinion on the outer periphery of the pinion shaft, a torque detection device that detects input torque to the pinion shaft, an electric motor that applies an assist force to steering based on a detection signal from the torque detection device, and a housing that accommodates the pinion shaft and the rack shaft.

[0003] The housing includes a pinion-side housing that accommodates the pinion shaft, a connecting housing that accommodates the meshing portion between the pinion gear and rack gear, and a rack-side housing that accommodates the rack shaft. An oil seal is provided between the pinion shaft and the connecting housing. Even if the boot covering the rack shaft is damaged, the oil seal prevents foreign matter from entering the pinion-side housing, protecting the torque detector and other components inside the pinion-side housing.

[0004] Generally, oil seals seal both liquids and gases. In the electric power steering device described in JPH10-258749A, an oil seal is provided in the connecting housing between the pinion-side housing and the rack-side housing. Therefore, when a leak test is performed by filling the housing with gas during manufacturing, the entire housing cannot be filled with gas at once; it is necessary to fill the pinion-side housing and the rack-side housing separately. In other words, the provision of the oil seal makes the leak test more time-consuming.

[0005] An object of the present invention is to eliminate the influence of a sealing member on a leak test that is carried out by filling a gas.

[0006] According to one aspect of the present invention, a sealing member that seals between the outer peripheral surface of a shaft and the inner peripheral surface of a storage section in which the shaft is housed comprises an annular main body portion provided between the outer peripheral surface of the shaft and the inner peripheral surface of the storage section, and a filter that is permeable to gas but not to liquid, wherein a ventilation portion that passes through the main body portion in the axial direction is formed in the main body portion, and the filter is provided in the ventilation portion.

[0007] FIG. 1 is a configuration diagram of an electric power steering device. FIG. 2 is a partial cross-sectional view of a housing. FIG. 3 is a perspective view of a seal member according to this embodiment. FIG. 4 is a perspective view of a core portion. FIG. 5 is a cross-sectional view taken along line VV in FIG. 3. FIG. 6 is an enlarged cross-sectional view of A shown in FIG. 5. FIG. 7 is a perspective view of a core portion according to a modified example of this embodiment.

[0008] A seal member 90 according to an embodiment of the present invention will be described with reference to the drawings.

[0009] The seal member 90 of this embodiment is provided in an electric power steering device 100. As shown in Fig. 1 , the electric power steering device 100 includes a steering shaft 11 that rotates in response to steering of a steering wheel 1 by a driver, a first pinion gear 16 that is provided on the steering shaft 11 and rotates together with the steering shaft 11, and a rack shaft 12 that has a rack gear 12a that meshes with the first pinion gear 16 and steers the wheels 2.

[0010] The steering shaft 11 has an input shaft 13 that rotates in response to a steering operation performed by the driver operating the steering wheel 1, an output shaft 15 that displaces the rack shaft 12, and a torsion bar 14 that connects the input shaft 13 and the output shaft 15.

[0011] The rack shaft 12 is a shaft-shaped member extending in the left-right direction of the vehicle, and is connected to the wheels 2 via tie rods 5 and knuckle arms 4 .

[0012] The output shaft 15 and the rack shaft 12 are connected to each other via a rack-and-pinion mechanism consisting of a first pinion gear 16 provided at the end of the output shaft 15 and a rack gear 12a provided on the rack shaft 12. Torque of the output shaft 15 is converted into an axial load of the rack shaft 12 via the first pinion gear 16 and the rack gear 12a, which mesh with each other, and transmitted to the rack shaft 12. As a result, the rack shaft 12 is displaced in the axial direction and steers the wheels 2 via the tie rod 5. In addition, the rack shaft 12 is biased toward the first pinion gear 16 by a biasing mechanism 17 (see FIG. 2 ). This reduces backlash between the rack gear 12a and the first pinion gear 16, and reduces rattle noise when the rack shaft 12 is displaced.

[0013] The electric power steering device 100 includes an assist unit 20 that generates steering assist torque using an electric motor 21. The assist unit 20 transmits the torque of the electric motor 21 to the rack shaft 12 independently of the output shaft 15, thereby assisting the steering operation of the driver. The assist unit 20 includes a drive shaft 22 that is rotationally driven by the electric motor 21, a second pinion gear 23 that is provided on the drive shaft 22 and rotates together with the drive shaft 22, and a speed reducer 50 that reduces the rotation of the electric motor 21 and transmits it to the drive shaft 22.

[0014] The speed reducer 50 is a worm gear mechanism including a worm shaft 51 driven by the electric motor 21 and a worm wheel 52 provided on the drive shaft 22. The worm shaft 51 and the worm wheel 52 are meshed with each other, and the second pinion gear 23 and the rack gear 12a are meshed with each other. Torque of the electric motor 21 is transmitted to the rack shaft 12 via the worm shaft 51, the worm wheel 52, the drive shaft 22, the second pinion gear 23, and the rack gear 12a.

[0015] The electric power steering device 100 includes a torque sensor 40 that detects the torque acting on the torsion bar 14, and a controller 30 that controls the drive of the electric motor 21 in accordance with the detected value of the torque sensor 40. The controller 30 calculates the torque to be output by the electric motor 21 based on the output signal from the torque sensor 40, and controls the drive of the electric motor 21 so that this torque is generated.

[0016] In this way, in the electric power steering device 100 configured as described above, the steering torque applied to the input shaft 13 is detected by the torque sensor 40, and the drive of the electric motor 21 is controlled by the controller 30 based on the detection result, thereby assisting the driver in steering operation.

[0017] As shown in FIG. 2 , the electric power steering device 100 includes a housing 60 that accommodates the steering shaft 11 and the rack shaft 12 .

[0018] The housing 60 is made of a metal such as aluminum. The housing 60 includes a rack housing 70 that houses the rack shaft 12, the biasing mechanism 17, etc., and a handle-side housing 80 that is fastened to the rack housing 70 via bolts 61. A storage section 81, which is a space within the handle-side housing 80, houses a portion of the input shaft 13, a portion of the torsion bar 14, a portion of the output shaft 15, and the torque sensor 40. The input shaft 13 and the output shaft 15 are rotatably supported by the handle-side housing 80 via bearings 62 and 63, respectively. A seal member 90 is provided between the outer circumferential surface of the output shaft 15 of the steering shaft 11 and the inner circumferential surface of the storage section 81 of the handle-side housing 80 to seal the gap between them.

[0019] The seal member 90 is intended to prevent foreign matter such as water from entering the handle-side housing 80 from the rack housing 70, thereby protecting electrical components such as the torque sensor 40 inside the handle-side housing 80. As shown in Fig. 3, the seal member 90 includes an annular main body 91 provided between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the accommodating portion 81, and a filter 99 that is permeable to gas but impermeable to liquid.

[0020] The main body 91 has an annular core 92 (see FIGS. 4 and 5) made of metal, and an annular seal 95 (see FIGS. 3 and 5) in which the core 92 is provided.

[0021] As shown in Figures 4 to 6, the core metal portion 92 has a flat, annular flat plate portion 92a and a cylindrical tubular portion 92b extending axially from the radially outer end of the flat plate portion 92a. In other words, the core metal portion 92 has a shape in which the boundary between the flat plate portion 92a and the cylindrical portion 92b is bent at a substantially right angle. The core metal portion 92 has first ventilation portions 97a. The first ventilation portions 97a are through-holes that penetrate the flat plate portion 92a in the axial direction, and multiple first ventilation portions 97a are formed at equal intervals in the circumferential direction (see Figure 4). In Figure 3, the first ventilation portions 97a are hidden by the filter 99 and are indicated by dotted lines. Multiple first ventilation portions 97a may be formed at different circumferential intervals.

[0022] The seal portion 95 is formed, for example, from resin. As shown in FIGS. 3, 5, and 6, the seal portion 95 includes an annular inner seal portion 95a provided radially inward, an annular outer seal portion 95b provided radially outward, and an annular connecting portion 95c provided between the upper ends of the inner seal portion 95a and the upper ends of the outer seal portion 95b in FIGS. 3, 5, and 6. The inner seal portion 95a is formed to extend in the axial direction, and its inner circumferential surface is formed to bulge radially inward. The outer seal portion 95b is formed to extend in the axial direction, and the boundary between the flat portion 92a and the cylindrical portion 92b of the core portion 92 and the cylindrical portion 92b are provided inside the connecting portion 95c. The inner and outer ends of the flat portion 92a of the core portion 92 are provided inside the connecting portion 95c. A second vent portion 97b is formed in the connecting portion 95c as a through-hole that penetrates the connecting portion 95c in the axial direction. The second ventilation portion 97b is formed in an annular shape, and the flat portion 92a of the core metal portion 92 is provided such that the area corresponding to the second ventilation portion 97b is not covered by the connecting portion 95c. The seal member 90 is attached by pressing the inner seal portion 95a against the outer peripheral surface of the output shaft 15 with an annular member 98 such as a snap ring. When the seal member 90 is attached between the outer peripheral surface of the output shaft 15 and the inner peripheral surface of the accommodating portion 81, the inner peripheral surface of the inner seal portion 95a comes into close contact with the outer peripheral surface of the output shaft 15, and the outer peripheral surface of the outer seal portion 95b comes into close contact with the inner peripheral surface of the accommodating portion 81.

[0023] The first ventilation portion 97a and the second ventilation portion 97b are in communication with each other. The first ventilation portion 97a and the second ventilation portion 97b form a ventilation portion 97 that axially penetrates the main body portion 91. Even when the seal member 90 is provided between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the accommodating portion 81, the space on the front side (handle-side housing 80 side) of the seal member 90 and the space on the back side (rack housing 70 side) thereof are in communication with each other through the first ventilation portion 97a and the second ventilation portion 97b. Note that the second ventilation portion 97b does not have to be formed in an annular shape, and multiple second ventilation portions 97b may be formed at equal intervals in the circumferential direction corresponding to the first ventilation portions 97a.

[0024] The filter 99 is a waterproof and breathable membrane made of, for example, polytetrafluoroethylene (PTFE). As shown in FIG. 3 , the filter 99 is formed in an annular shape and is provided in the ventilation portion 97. Specifically, the filter 99 is provided to cover the openings of the first ventilation portions 97a formed in the flat portion 92a of the core portion 92. One filter 99 is provided to cover each opening of the multiple first ventilation portions 97a. As shown in FIG. 6 , the inner peripheral edge 99a of the filter 99 is sandwiched between the inner peripheral side of the connecting portion 95c and the flat portion 92a, and the outer peripheral edge 99b of the filter 99 is sandwiched between the outer peripheral side of the connecting portion 95c and the flat portion 92a. This allows the filter 99 to be easily positioned in the axial direction. The core portion 92, the seal portion 95, and the filter 99 are integrally molded, for example, by insert molding, with the filter 99 and the core portion 92 positioned using a mold. The filter 99 allows gas to pass through the first ventilation portion 97a and the second ventilation portion 97b but prevents liquid from passing through them. Therefore, the seal member 90 blocks the movement of liquid between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the accommodating portion 81. As a result, even if a foreign object such as water enters the rack housing 70 due to damage to the boot (not shown) covering the rack shaft 12, the foreign object is prevented from entering the handle-side housing 80, and electrical components such as the torque sensor 40 inside the handle-side housing 80 are protected.

[0025] Here, a leak test is performed on the electric power steering device 100 before shipping. In the leak test, gas is filled into the housing 60 and the airtightness is inspected. If the seal member 90 were configured to seal both liquid and gas, the entire housing 60 could not be filled with gas at once when performing the leak test, and it would be necessary to fill the rack housing 70 and the handle-side housing 80 with gas separately. In other words, the provision of the seal member 90 makes the leak test more time-consuming.

[0026] In contrast, in the seal member 90 of this embodiment, a filter 99 that is permeable to gas but not to liquid is provided in the ventilation section 97 of the main body 91. Therefore, the seal member 90 seals the gap between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the accommodating section 81 so that gas can pass through but liquid cannot. Therefore, during a leak test, when gas is filled into one of the rack housing 70 and the handle-side housing 80, gas is also filled into the other, so there is no need to fill gas into both the rack housing 70 and the handle-side housing 80. This eliminates the effect of the seal member 90 on a leak test that is performed by filling the gas.

[0027] Furthermore, a plurality of ventilation sections 97 are formed at intervals in the circumferential direction of the main body 91. As a result, even if one of the ventilation sections 97 is blocked by a foreign object or the like, gas can pass through the other ventilation sections 97. Furthermore, since the plurality of ventilation sections 97 provide ventilation between the rack housing 70 and the handle-side housing 80, the size of each ventilation section 97 can be reduced. As a result, even if the filter 99 has low rigidity, the filter 99 can be provided in the ventilation section 97 without causing a large recess.

[0028] Furthermore, in this embodiment, the filter 99 is provided on the handle-side housing 80 side of the ventilation section 97 (upper side in Figures 2, 3, and 5). This prevents the filter 99 from becoming contaminated and clogged with lubricating oil, etc., inside the rack housing 70. The filter 99 may also be provided on the rack housing 70 side of the ventilation section 97 (lower side in Figures 2, 3, and 5). In this case, the filter 99 is prevented from becoming contaminated and clogged with lubricating oil, etc., from the adjacent bearing 63.

[0029] According to the present embodiment described above, the following advantageous effects are achieved.

[0030] In the seal member 90, a filter 99 that is permeable to gas but impermeable to liquid is provided in the ventilation section 97 of the main body 91. Therefore, the seal member 90 seals the gap between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the housing section 81 so that gas can pass through but liquid cannot. This eliminates the effect of the seal member 90 on a leak test that is performed by filling the space with gas.

[0031] Next, modifications of the present embodiment will be described. The following modifications are also within the scope of the present invention, and it is possible to combine the following modifications with the configurations of the above embodiment, or to combine the following modifications with each other.

[0032] <Variation 1> In the above embodiment, the main body 91 of the seal member 90 includes an annular core 92 having a flat plate portion 92a and a cylindrical portion 92b, and an annular seal portion 95 having an inner seal portion 95a, an outer seal portion 95b, and a connecting portion 95c. However, the configuration of the core 92 and the seal portion 95 is not limited to the above, and the main body 91 does not have to include the core 92. The main body 91 may be configured to at least be provided between the outer circumferential surface of the output shaft 15 and the inner circumferential surface of the housing portion 81 to seal the gap between them, and to have a ventilation portion 97 that penetrates the main body 91 in the axial direction.

[0033] <Modification 2> In the above embodiment, a plurality of ventilation portions 97 are formed at intervals in the circumferential direction of the main body portion 91. However, this is not limiting, and only one ventilation portion 97 may be formed in the main body portion 91. Even with this configuration, the same effects as those of the above embodiment can be achieved.

[0034] <Modification 3> In the above embodiment, the filter 99 is formed in an annular shape and provided in the ventilation portion 97, and one filter 99 is provided to cover each opening of the plurality of first ventilation portions 97 a. However, the present invention is not limited to this. For example, the filter 99 may be formed in a circular shape, and a plurality of filters 99 may be provided so that one filter 99 covers the opening of one first ventilation portion 97 a.

[0035] <Modification 4> In the above embodiment, the filter 99 is positioned in the axial direction by sandwiching the inner peripheral edge 99a between the connecting portion 95c and the flat plate portion 92a and the outer peripheral edge 99b between the connecting portion 95c and the flat plate portion 92a. However, this is not limited to this. For example, as shown in FIG. 7 , a positioning portion 92c that engages with the filter 99 to position the filter 99 may be formed on the core portion 92, and the filter 99 may be positioned by the positioning portion 92c. The positioning portion 92c is formed to protrude axially from the flat plate portion 92a toward the filter 99. The positioning portion 92c is formed in a triangular shape and engages with a notch (not shown) formed in the filter 99. This allows for easy circumferential positioning of the filter 99. Alternatively, the positioning portion 92c may be formed in a wall shape at the inner end of the flat plate portion 92a. In this case, the positioning portion 92c engages with the inner peripheral surface of the annular filter 99. This allows for easy radial positioning of the filter 99.

[0036] <Modification 5> In the above embodiment, the seal member 90 is provided in the electric power steering device 100. However, the present invention is not limited to this, and the seal member 90 may be provided in other equipment that is filled with gas and used for leak testing.

[0037] The configuration, operation, and effects of the embodiment of the present invention configured as above will be described below.

[0038] The sealing member 90, which seals between the outer peripheral surface of the steering shaft 11 as a shaft and the inner peripheral surface of the accommodation portion 81 in which the steering shaft 11 is accommodated, comprises an annular main body portion 91 provided between the outer peripheral surface of the steering shaft 11 and the inner peripheral surface of the accommodation portion 81, and a filter 99 that is permeable to gas but not to liquid, and the main body portion 91 is formed with a ventilation portion 97 that passes through the main body portion 91 in the axial direction, and the filter 99 is provided in the ventilation portion 97.

[0039] In this configuration, a filter 99 that is permeable to gas but impermeable to liquid is provided in the ventilation portion 97 of the main body 91 of the seal member 90. Therefore, the seal member 90 seals the gap between the outer circumferential surface of the steering shaft 11 and the inner circumferential surface of the housing portion 81 so that gas can pass through but liquid cannot. This eliminates the effect of the seal member 90 on a leak test that is performed by filling the gap with gas.

[0040] The main body 91 also has a ring-shaped core portion 92 made of metal and a ring-shaped seal portion 95 in which the core portion 92 is provided, and the ventilation portion 97 is formed in the core portion 92 and the seal portion 95.

[0041] Furthermore, a plurality of ventilation portions 97 are formed at intervals in the circumferential direction of the main body portion 91 .

[0042] In these configurations, even if one of the ventilation sections 97 is blocked by a foreign object or the like, gas can still pass through the other ventilation sections 97 .

[0043] In addition, the filter 99 is arranged to cover the opening of the ventilation portion 97 (first ventilation portion 97a) formed in the core portion 92, and the core portion 92 is formed with a positioning portion 92c that engages with the filter 99 to position the filter 99.

[0044] In this configuration, the filter 99 can be easily positioned by the positioning portion 92c.

[0045] In addition, the filter 99 is arranged to cover the opening of the ventilation portion 97 (first ventilation portion 97a) formed in the core portion 92, and the edges (99a, 99b) of the filter 99 are sandwiched between the seal portion 95 and the core portion 92.

[0046] In this configuration, the edges (99a, 99b) of the filter 99 are sandwiched between the seal portion 95 and the core metal portion 92, so that the filter 99 can be easily positioned in the axial direction.

[0047] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0048] This application claims priority based on Japanese Patent Application No. 2023-123653, filed with the Japan Patent Office on July 28, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A sealing member that seals between the outer peripheral surface of a shaft and the inner peripheral surface of a storage section in which the shaft is housed, comprising: an annular main body portion provided between the outer peripheral surface of the shaft and the inner peripheral surface of the storage section; and a filter that is permeable to gas but not to liquid, wherein a ventilation portion that passes through the main body portion in the axial direction is formed in the main body portion, and the filter is a sealing member provided in the ventilation portion.

2. A sealing member as claimed in claim 1, wherein the main body portion has an annular core portion made of metal and an annular seal portion in which the core portion is provided, and the ventilation portion is formed in the core portion and the seal portion.

3. A seal member according to claim 1, wherein the ventilation portions are formed in a plurality at intervals in the circumferential direction of the main body portion.

4. A sealing member as claimed in claim 2, wherein the filter is provided to cover an opening of the ventilation section formed in the core metal portion, and the core metal portion is formed with a positioning section that engages with the filter to position the filter.

5. A sealing member as claimed in claim 2, wherein the filter is provided to cover an opening of the ventilation section formed in the core metal portion, and the edge of the filter is sandwiched between the sealing section and the core metal portion.

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