JP2020090262A - Electric power steering device - Google Patents

Abstract

To improve mountability of an electric power steering device comprising an internal pressure adjusting part.SOLUTION: An electric power steering device 100 comprises: a rack housing 17 in which a rack accommodation space for accommodating a rack shaft 12 is formed; a worm housing 53 in which a worm wheel 52 and a worm shaft 51 are accommodated, and a worm accommodation space communicating with the rack accommodation space is formed; and an internal pressure adjusting part 60, 70 disposed in the worm housing 53 in order to adjust pressure force inside the rack accommodation space and the worm accommodation space. The internal pressure adjusting part 60, 70 has a bellows 61, 71 which blocks at least one opening end of a first storage hole 54 storing the worm wheel 52 and a second storage hole 55 storing the worm shaft 51, and the bellows 61, 71 deforms according to differential pressure between the pressure force outside and the pressure force inside the worm accommodation space.SELECTED DRAWING: Figure 3

Description

The present invention relates to an electric power steering device.

Patent Document 1 discloses an electric power steering apparatus including a transmission unit that transmits a steering force from a steering unit to a rack shaft, and an internal pressure adjustment unit that adjusts the pressure inside a housing that houses the transmission unit. There is.

JP, 2016-179763, A

The internal pressure adjusting unit in the electric power steering device described in Patent Document 1 is provided so as to project to the outside of the housing that houses the transmitting unit. For this reason, there is a possibility that a member provided around the electric power steering device may interfere with the internal pressure adjusting section, and the mountability of the electric power steering device on the vehicle may deteriorate.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the mountability of an electric power steering apparatus including an internal pressure adjusting unit.

According to the present invention, an electric power steering apparatus rotationally drives a rack shaft having a rack, a drive shaft having a pinion that meshes with the rack, a worm wheel provided on the drive shaft, a worm shaft that meshes with the worm wheel, and a worm shaft. An electric motor, a rack housing in which a first accommodation space for accommodating a rack shaft is formed, a worm housing in which a second accommodation space for accommodating a worm wheel and a worm shaft and communicating with the first accommodation space is formed, and a worm housing And an internal pressure adjusting section for adjusting the pressure in the first accommodation space and the second accommodation space, the second accommodation space including a first accommodation hole for accommodating the worm wheel and a second accommodation space for accommodating the worm shaft. And a housing member, and the internal pressure adjusting unit includes a membrane member that closes an open end of at least one of the first housing hole and the second housing hole, and the membrane member is configured to receive an external pressure and a second housing space. It is characterized in that it deforms in accordance with the pressure difference from the pressure.

According to this aspect of the invention, the internal pressure adjusting section that can adjust the pressure in the first accommodation space and the second accommodation space is provided at the open end of at least one of the first accommodation hole and the second accommodation hole. As described above, the internal pressure adjusting portion is not provided so as to project from the rack housing or the worm housing, but is housed in the dead space generated at the opening end of the first accommodation hole or the opening end of the second accommodation hole. Therefore, it is possible to avoid the interference between the member provided around the electric power steering device and the internal pressure adjusting unit.

According to the present invention, the internal pressure adjusting unit further has a holding member that holds the membrane member at the opening end, the holding member is provided with a vent hole through which outside air flows in and out, and the vent hole prevents liquid from passing therethrough. A filter that allows the passage of gas is provided.

In the present invention, a filter that suppresses the passage of liquid and allows the passage of gas is provided in the vent hole that guides the external pressure to the membrane member. By thus providing the waterproof and moisture-permeable filter, it is possible to prevent water from entering the internal pressure adjusting unit, and as a result, when the electric power steering device is submerged or exposed to water, the internal pressure adjusting unit can be used. It is possible to prevent water from entering the inside of the electric power steering device.

The present invention is characterized in that the internal pressure adjusting section further includes a limiting section for limiting the deformation of the membrane member.

In the present invention, the limiting portion that limits the deformation of the membrane member is provided. In this way, by limiting the deformation of the membrane member, it is possible to prevent the membrane member from coming into contact with the surrounding members and being damaged or sticking to the surrounding members. As a result, the membrane member can be smoothly deformed according to the pressure difference.

The present invention is characterized in that the membrane member is provided at the opening end of the first accommodation hole.

In the present invention, the membrane member is provided at the opening end of the first accommodation hole that accommodates the worm wheel. Since the outer diameter of the first housing hole for housing the worm wheel is larger than the outer diameter of the worm wheel, it is possible to set the outer diameter of the membrane member to be relatively large. If the outer diameter of the membrane member is large, the volumes of the first accommodating space and the second accommodating space can be greatly changed even if the membrane member is slightly deformed. It is possible to quickly adjust the pressure in the second accommodation space.

In the present invention, the first central axis of the first accommodation hole and the second central axis of the second accommodation hole intersect at an angle when viewed from a direction orthogonal to the first central axis and the second central axis. Is characterized by.

In the present invention, the first center axis of the first accommodation hole and the second center axis of the second accommodation hole intersect at an angle. When the first central axis CL1 and the second central axis CL2 intersect at an angle, the width of the communication opening communicating the first accommodation hole and the second accommodation hole in the direction of the first central axis CL1 increases, and the first accommodation hole The dead space generated at the open end of is large. As described above, by incorporating the internal pressure adjusting section at the opening end of the first accommodation hole where a large dead space is generated, it is possible to improve the mountability of the electric power steering apparatus including the internal pressure adjusting section on the vehicle.

The present invention further includes a pair of tie rods swingably connected to the rack shaft, and a boot that covers a connecting portion between the rack shaft and the tie rod and defines a part of the first accommodation space. The member is characterized in that it deforms with less pressure than the boot.

In this invention, the membrane member deforms with a pressure smaller than that of the boot. By making the membrane member deformable more easily than the boot, it is possible to reliably prevent the boot from being deformed or damaged when a pressure difference occurs.

The present invention is characterized in that the membrane member is a bellows or a diaphragm.

In the present invention, the membrane member is a bellows or a diaphragm. As described above, by adopting the bellows or the diaphragm having a simple structure as the film member, it is possible to reduce the manufacturing cost of the electric power steering apparatus including the internal pressure adjusting section.

According to the present invention, it is possible to improve the mountability of the electric power steering device including the internal pressure adjusting unit.

FIG. 1 is a configuration diagram of an electric power steering device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the electric power steering device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view of the internal pressure adjusting unit of the electric power steering device according to the first embodiment of the present invention. FIG. 4 is a sectional view taken along the line IV-IV in FIG. FIG. 5 is a sectional view taken along the line VV of FIG. FIG. 6 is a configuration diagram of an electric power steering apparatus according to the second embodiment of the present invention. FIG. 7 is a cross-sectional view of the internal pressure adjusting portion of the electric power steering device according to the second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
An electric power steering apparatus 100 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

The electric power steering device 100 is a device that is installed in a vehicle and assists the driver in steering the steering wheel 1.

In the present embodiment, as shown in FIG. 1, a dual pinion type electric power steering apparatus 100 in which steering torque by a driver and steering assist torque by an electric motor 21 are independently input to a rack shaft 12 will be described.

First, the overall configuration of the electric power steering device 100 will be described with reference to FIG.

The electric power steering apparatus 100 is input through the steering wheel 1 by a driver, a steering mechanism 10 that steers the wheels 2 according to the rotation of the steering wheel 1 by the steering of the driver, an assist mechanism 20 that assists the steering of the driver. A torque sensor 40 for detecting the steering torque is provided, and a controller 30 for controlling the drive of the electric motor 21 based on the detection result of the torque sensor 40.

The steering mechanism 10 includes a steering shaft 11 that rotates according to the rotation of the steering wheel 1 and a rack shaft 12 that steers the wheels 2 according to the rotation of the steering shaft 11.

The steering shaft 11 includes an input shaft 13 that rotates as the driver steers the steering wheel 1, an output shaft 15 that links the rack shaft 12 that steers the wheels 2, and a torsion that connects the input shaft 13 and the output shaft 15. And a bar 14. A first pinion 16 that meshes with a rack 12 a formed on the rack shaft 12 is formed below the output shaft 15.

The rack shaft 12 is a shaft-shaped member that extends in the left-right direction of the vehicle, and is connected to the wheels 2 via the tie rods 5 and the knuckle arms 4. The tie rods 5 are swingably connected to the rack shaft 12 via ball joints 6 as connecting portions provided at both ends of the rack shaft 12. The connecting portion that connects the rack shaft 12 and the tie rod 5 is not limited to the ball joint 6, and a universal joint of another type may be used.

When the steering wheel 1 is steered by the driver, the steering shaft 11 rotates, and the rotation is converted into a linear movement of the rack shaft 12 by the first pinion 16 and the rack 12a, and the wheel 2 through the tie rod 5 and the knuckle arm 4. Is steered. Note that, instead of the configuration in which the first pinion 16 is formed in the lower portion of the output shaft 15, the configuration may be such that the pinion shaft that meshes with the rack shaft 12 and the output shaft 15 are connected via an intermediate shaft.

The assist mechanism 20 includes an electric motor 21 that is a power source of steering assist torque, a drive shaft 22 that transmits the driving force of the electric motor 21 to the rack shaft 12, and a rotation of the electric motor 21 that is decelerated and transmitted to the drive shaft 22. And a deceleration mechanism 50. The speed reduction mechanism 50 has a worm shaft 51 connected to the output shaft of the electric motor 21, and a worm wheel 52 meshing with the worm shaft 51 and connected to the drive shaft 22.

A second pinion 23 as a pinion that meshes with the rack 12 a formed on the rack shaft 12 is formed below the drive shaft 22. When the electric motor 21 rotates, the drive shaft 22 rotates via the speed reduction mechanism 50, and the rotation is converted into a linear motion of the rack shaft 12 by the second pinion 23 and the rack 12a, and a steering assist torque is applied to the rack shaft 12. To be done.

The torque sensor 40 detects the steering torque applied to the torsion bar 14 based on the rotation angle difference between the input shaft 13 and the output shaft 15, and outputs a voltage signal corresponding to the detected steering torque to the controller 30.

The controller 30 includes a CPU (Central Processing Unit) that performs arithmetic processing, a ROM (Read-Only Memory) that stores a control program executed by the CPU, and a RAM (random access memory) that stores the arithmetic result of the CPU. And a microcomputer including. The controller 30 may be composed of a single microcomputer or may be composed of a plurality of microcomputers.

The controller 30 calculates the torque output by the electric motor 21 based on the voltage signal from the torque sensor 40, and controls the drive of the electric motor 21 so that the torque is generated.

As described above, the electric power steering apparatus 100 detects the steering torque applied to the input shaft 13 by the torque sensor 40, and based on the detection result, controls the drive of the electric motor 21 by the controller 30 to control the driver. Assist steering operation.

Further, as shown in FIG. 2, the electric power steering apparatus 100 includes a rack housing 17 for housing the rack shaft 12, a shaft housing 18 for housing the steering shaft 11, a worm housing for housing a worm shaft 51 and a worm wheel 52. 53 is further provided.

The rack housing 17 has a housing hole 17a that is formed so as to penetrate therethrough in the axial direction and accommodates the rack shaft 12, and a first insertion hole 17b and one of the first insertion hole 17b that is formed so that one end of the rack housing 17 is open at the outer peripheral surface and intersects the housing hole 17a. 2 insertion holes 17c. A shaft housing 18 is coupled to the rack housing 17 through a bolt (not shown) so that the output shaft 15 is inserted into the first insertion hole 17b, and a worm housing 53 is inserted so that the drive shaft 22 is inserted into the second insertion hole 17c. Are coupled via a bolt (not shown).

Boots 19 are attached to both ends of the rack housing 17 in order to protect the ball joint 6 and prevent water and the like from entering the rack housing 17. The boot 19 is a rubber bellows-like member, and one end thereof is fastened to the end portion of the rack housing 17 and the other end thereof is fastened to the tie rod 5 by a band-shaped fastening member (not shown).

In this way, in the rack housing 17, the rack accommodation space as the first accommodation space defined by the accommodation hole 17a and the boot 19 is formed. The rack accommodation space communicates with the shaft accommodation space formed in the shaft housing 18 through the first insertion hole 17b, and the worm accommodation as a second accommodation space formed in the worm housing 53 through the second insertion hole 17c. Communicate with the space.

Here, the storage space including the rack storage space, the shaft storage space, and the worm storage space is in a hermetically sealed state in order to prevent water or foreign matter from entering from the outside. Generally, the pressure in the closed space rises as the temperature rises and drops as the temperature falls, so in the electric power steering device 100, a pressure difference occurs between the pressure in the housing space and the external pressure. Will occur. As a result, the boot 19 formed of a relatively easily deformable material such as rubber or resin bursts due to a pressure difference or is extremely deformed to come into contact with the rack 12a or the like and be damaged, so that water or foreign matter can be electrically powered. There is a risk that the steering device 100 may get inside.

Such a phenomenon can be avoided by providing an internal pressure adjusting section capable of adjusting the pressure in the accommodation space partly defined by the boot 19. However, if the internal pressure adjusting portion is provided so as to project from the rack housing 17, a member provided around the electric power steering device 100 and the internal pressure adjusting portion interfere with each other, which may deteriorate the mountability of the electric power steering device 100 in a vehicle. There is.

In order to prevent the mountability of the electric power steering device 100 from deteriorating, the internal pressure adjusting unit is arranged in the dead space of the electric power steering device 100 in this embodiment.

Next, the first internal pressure adjusting unit 60 arranged in the dead space of the electric power steering system 100 will be described with reference to FIGS. 3 and 4. FIG. 3 is a partial cross-sectional view showing a part of the cross section of the worm housing 53 along the axis of the drive shaft 22. 4 is a cross-sectional view showing a cross section of the worm housing 53 taken along the line IV-IV of FIG. 3, and members other than the worm housing 53 are omitted.

As shown in FIG. 3, the worm housing 53 accommodates a first accommodating hole 54 having a first central axis CL1 as a central axis and accommodating the worm wheel 52, and a worm shaft 51 having a second central axis CL2 as a central axis. The second accommodation hole 55 and the second accommodation hole 55 are formed so as to be orthogonal to each other, and the first accommodation hole 54 and the second accommodation hole 55 communicate with each other through the communication opening 57. The communication opening 57 is an opening provided for meshing the worm shaft 51 and the worm wheel 52.

Here, as shown in FIGS. 3 and 4, the width of the communication opening 57 in the first central axis CL1 direction is usually larger than the width of the worm wheel 52. In order to reliably seal the first accommodation hole 54, it is necessary to assemble a closing member that closes the opening end of the first accommodation hole 54 to the worm housing 53 so as not to reach the communication opening 57.

That is, since the space for assembling the closing member has to be secured while avoiding the communication opening 57, the length of the worm housing 53 in the first central axis CL1 direction is inevitably long. As a result, due to the opening of the communication opening 57, a dead space in which nothing is arranged occurs on the opening end side of the first accommodation hole 54.

In particular, in order to change the layout of the electric motor 21, when it is necessary to mesh the worm wheel 52 and the worm shaft 51 at a predetermined angle, the first central axis CL1 and the second central axis CL2 are different from each other. , When viewed from a direction orthogonal to the first central axis line CL1 and the second central axis line CL2, they are inclined and intersect with each other.

In this state, the width of the communication opening 57 in the direction of the first central axis CL1 is shown by a solid line as shown by the broken line in FIG. 4 (when the first central axis CL1 and the second central axis CL2 are orthogonal to each other). ) Is larger than Therefore, the length of the worm housing 53 in the direction of the first central axis CL1 is further increased because the blocking member is assembled while avoiding the communication opening 57.

That is, when the worm wheel 52 and the worm shaft 51 are engaged with each other in a state of being inclined by a predetermined angle, the opening of the first accommodation hole 54 is larger than that in the case where the worm wheel 52 and the worm shaft 51 are orthogonal to each other. A larger dead space will occur on the end side.

In the present embodiment, the first internal pressure adjusting section 60, which is an internal pressure adjusting section capable of adjusting the pressure in the worm accommodation space formed of the first accommodation hole 54 and the second accommodation hole 55, is used as the first internal pressure adjusting section 60 in which the dead space is generated. It is provided at the open end of the accommodation hole 54. Since the worm storage space communicates with the rack storage space through the second insertion hole 17c, as a result, the first internal pressure adjusting section 60 reduces the pressure inside the rack storage space, a part of which is defined by the boot 19. It will be adjusted.

As shown in FIG. 3, the first internal pressure adjusting unit 60 includes a bellows 61 as a film member that is deformed according to a pressure difference, a support member 62 that assists in assembling the bellows 61 into the first housing hole 54, and a bellows. And a holding member 63 that holds 61 at the opening end of the first accommodation hole 54.

The bellows 61 includes a disc-shaped bottom portion 61a, a cylindrical bellows portion 61b having one end coupled to the periphery of the bottom portion 61a, and an annular flange portion 61c having an inner circumferential side coupled to the other end of the bellows portion 61b. And an annular seal portion 61d such as an O-ring provided on the outer peripheral side of the flange portion 61c. The bottom portion 61a, the bellows portion 61b, and the flange portion 61c are made of thin metal, and the seal portion 61d is made of rubber or resin.

The support member 62 has a cylindrical insertion portion 62a that is inserted into the first accommodation hole 54, and an annular flange portion 62b that extends radially outward from the outer peripheral surface of the insertion portion 62a. At one end of the insertion portion 62a on the side to be inserted into the first accommodation hole 54, a first limiting portion 62d is formed as a limiting portion that is formed annularly from the inner peripheral surface toward the inner side in the radial direction. A holding groove 62c for holding the seal portion 61d of the bellows 61 is formed in an annular shape at the other end of the insertion portion 62a.

The support member 62 is fixed to the worm housing 53 with a bolt that is inserted through an insertion hole (not shown) provided in the flange portion 62b. A seal member 65 is provided between the support member 62 and the worm housing 53 to prevent water and the like from entering the worm housing space and prevent air from leaking from the worm housing space.

The holding member 63 has a disc-shaped holding portion 63a, a ventilation hole 63b formed through the center of the holding portion 63a, and a restriction formed by surrounding the ventilation hole 63b and projecting in an annular shape from the holding portion 63a. And a second limiting portion 63c as a portion.

The vent hole 63b is provided with a filter 64 that allows the passage of gas while suppressing the passage of liquid. The filter 64 is, for example, a waterproof/moisture permeable membrane body such as GORE-TEX (registered trademark). The filter 64 may be provided inside the ventilation hole 63b, or may be attached to the holding portion 63a so as to close the ventilation hole 63b.

The support member 62 and the holding member 63 are joined to each other by joining the peripheral edge of the holding portion 63a to the support member 62 by welding or the like with the bellows 61 sandwiched therebetween. Note that the connection between the support member 62 and the holding member 63 is not limited to welding, and may be screw connection, or if the support member 62 and the holding member 63 are made of resin, welding connection may be used. Since the gap between the support member 62 and the holding member 63 is sealed by the seal portion 61d of the bellows 61, the entry of water or the like into the worm accommodation space and the leakage of air from the worm accommodation space are prevented. To be prevented. The external pressure introduced through the ventilation hole 63b acts on one surface of the bellows 61 facing the holding member 63 side, and the pressure in the worm housing space acts on the other surface of the bellows 61. Become.

Further, the bellows 61 is sandwiched between the support member 62 and the holding member 63, so that the expansion amount of the bellows 61 is limited by the first limiting portion 62d and the second limiting portion 63c. Specifically, since the expansion of the bellows 61 is limited by the first limiting portion 62d provided on the worm wheel 52 side, the bellows 61 is prevented from coming into contact with the worm wheel 52 and being damaged. Further, since the contraction of the bellows 61 is limited by the second limiting portion 63c, the bellows 61 is prevented from sticking to the holding portion 63a.

Next, the operation of the first internal pressure adjusting unit 60 having the above configuration will be described.

When the temperature in the accommodation space including the rack accommodation space, the shaft accommodation space, and the worm accommodation space rises, and the pressure in the accommodation space becomes higher than the external pressure, the bellows 61 responds to the pressure difference between these pressures. It contracts so as to expand the volume of the accommodation space. By expanding the volume in this way, the pressure in the accommodation space decreases, and the pressure difference between the inside and the outside decreases. As a result, damage to the boot 19 is prevented, and water or foreign matter is prevented from entering the inside of the electric power steering device 100.

On the other hand, when the temperature in the accommodation space decreases and the pressure in the accommodation space becomes lower than the external pressure, the bellows 61 expands so as to reduce the volume of the accommodation space according to the pressure difference between these pressures. By reducing the volume in this way, the pressure in the accommodation space rises and the pressure difference between the inside and the outside decreases. As a result, damage to the boot 19 can be prevented, and water or foreign matter can be prevented from entering the inside of the electric power steering device 100.

Further, the electric power steering device 100 according to the present embodiment further includes a second internal pressure adjusting section 70 as an internal pressure adjusting section in addition to the above-described first internal pressure adjusting section 60.

Next, the second internal pressure adjusting section 70 will be described with reference to FIG. FIG. 5 is a cross-sectional view showing a cross section of a part of the assist mechanism 20 taken along the line VV of FIG.

The opening end of the second accommodation hole 55 that accommodates the worm shaft 51 is normally closed by a closing member. That is, a dead space is not a little generated on the opening end side of the second accommodation hole 55.

In the present embodiment, the second internal pressure adjusting section 70 capable of adjusting the pressure in the worm accommodation space formed of the first accommodation hole 54 and the second accommodation hole 55 is provided in the opening of the second accommodation hole 55 in which the above-mentioned dead space occurs. It is provided at the end. Note that, as described above, the worm storage space communicates with the rack storage space through the second insertion hole 17c, and as a result, the second internal pressure adjusting section 70 has a rack storage space partially defined by the boot 19. The pressure in the space will be adjusted.

As shown in FIG. 5, the second internal pressure adjusting unit 70 includes a bellows 71 as a film member that deforms according to a pressure difference, and a holding member 72 that holds the bellows 71 at the opening end of the second accommodation hole 55. Have.

Similar to the bellows 61, the bellows 71 has a disc-shaped bottom portion 71a, a cylindrical bellows portion 71b having one end joined to the periphery of the bottom portion 71a, and a circle having an inner circumferential side joined to the other end of the bellows portion 71b. It has an annular flange portion 71c and an annular seal portion 71d such as an O-ring provided on the outer peripheral side of the flange portion 71c. The bottom portion 71a, the bellows portion 71b, and the flange portion 71c are made of thin metal, and the seal portion 71d is made of rubber or resin.

The holding member 72 is a disc-shaped member, and has a ventilation hole 72a formed at its center. The ventilation hole 72a is provided with a filter 73 that allows the passage of gas while suppressing the passage of liquid. The filter 73 is, for example, a waterproof and moisture-permeable membrane body such as GORE-TEX (registered trademark). The filter 73 may be provided inside the ventilation hole 72a, or may be attached to the holding member 72 so as to close the ventilation hole 72a.

A holding groove 55a for holding the seal portion 71d of the bellows 71 is formed in an annular shape at the opening end of the second accommodation hole 55 of the worm housing 53.

The worm housing 53 and the holding member 72 are joined to each other by welding the peripheral edge of the holding member 72 to the worm housing 53 with the bellows 71 sandwiched therebetween.

Since the gap between the worm housing 53 and the holding member 72 is sealed by the seal portion 71d of the bellows 71, water and the like enter the worm housing space and air leaks from the worm housing space. To be prevented. The external pressure introduced through the ventilation hole 72a acts on one surface of the bellows 71 facing the holding member 72 side, and the pressure in the worm housing space acts on the other surface of the bellows 71. Become.

The second internal pressure adjusting unit 70 having the above-described configuration functions similarly to the above-described first internal pressure adjusting unit 60. Therefore, the description of the operation is omitted.

As described above, in the present embodiment, the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70 capable of adjusting the pressure in the accommodation space including the rack accommodation space, the shaft accommodation space, and the worm accommodation space are provided from the rack housing 17. As described above, the electric power steering device 100 is arranged in the dead space without being projected. Therefore, the mountability of the electric power steering device 100 including the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70 can be improved.

Even when the first internal pressure adjusting section 60 and the second internal pressure adjusting section 70 are provided, if the bellows 61 is less likely to be deformed than the boot 19, damage to the boot 19 may not be prevented. Therefore, in order to more reliably prevent damage to the boot 19, the material and shape of the bellows 61 are appropriately set so that the bellows 61 expands and contracts at a pressure lower than that of the boot 19.

Specifically, the shape and material of the bellows 61 are selected so as to have a lower elastic modulus than that of the boot 19. The membrane member is not limited to the bellows 61, and may be any member as long as it can be deformed by a pressure difference between the inside and the outside, for example, a diaphragm made of rubber or metal. ..

According to the above-mentioned 1st Embodiment, there exists an effect shown below.

In the electric power steering device 100, the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70 capable of adjusting the pressure in the accommodation space including the rack accommodation space, the shaft accommodation space, and the worm accommodation space are provided in the first accommodation hole 54. And the opening end of the second accommodation hole 55. As described above, the first internal pressure adjusting portion 60 and the second internal pressure adjusting portion 70 are not provided so as to project from the rack housing 17 or the worm housing 53, and the opening end of the first accommodation hole 54 and the opening of the second accommodation hole 55 are not provided. It is built into the dead space at the edge. For this reason, it is possible to prevent the members provided around the electric power steering device 100 from interfering with the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70, and as a result, the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70. It is possible to improve the mountability of the electric power steering device 100 including the adjustment unit 70 in a vehicle.

Although the electric power steering device 100 is provided with the first internal pressure adjusting unit 60 and the second internal pressure adjusting unit 70 as the internal pressure adjusting unit, if only one of them is provided, the pressure in the accommodation space is reduced. It is possible to adjust.

<Second Embodiment>
Next, an electric power steering apparatus 200 according to the second embodiment of the present invention will be described with reference to FIGS. 6 and 7. Below, it demonstrates centering around a different point from 1st Embodiment, attaches|subjects the same code|symbol to the same structure as 1st Embodiment, and abbreviate|omits description.

The basic configuration of the electric power steering device 200 is the same as that of the electric power steering device 100 according to the first embodiment. The electric power steering device 200 is a so-called single pinion type, and is a dual pinion type in that the assist mechanism 20 is connected to the steering shaft 11 via a first pinion 16 formed at a lower portion of the output shaft 15. It is different from the electric power steering device 100.

As shown in FIG. 6, in the electric power steering device 200, the assist mechanism 20 is arranged on the opposite side of the steering shaft 11 with the rack shaft 12 interposed therebetween, and is formed in the worm housing 53 as shown in FIG. 7. The first accommodation hole 54 for accommodating the worm wheel 52 is opened downward.

That is, in the electric power steering device 200, the first internal pressure adjusting unit 60 is assembled in the vertical direction opposite to the first internal pressure adjusting unit 60 of the electric power steering device 100 according to the first embodiment.

As described above, when the first internal pressure adjusting unit 60 is disposed below, there is a high possibility that water will enter the worm accommodation space through the first internal pressure adjusting unit 60. However, since the seal portion 61d and the seal member 65 are provided at the joint portion of the first internal pressure adjusting portion 60, and the filter 64 which is a waterproof and moisture permeable membrane is provided at the ventilation hole 63b, the first internal pressure is obtained. Water is prevented from entering the worm accommodation space through the adjusting unit 60.

The structure and function of the first internal pressure adjusting unit 60 are the same as those of the first internal pressure adjusting unit 60 of the electric power steering apparatus 100 according to the above-described first embodiment, and thus the description thereof will be omitted.

As described above, in the present embodiment, the first internal pressure adjusting portion 60 capable of adjusting the pressure in the accommodation space including the rack accommodation space, the shaft accommodation space, and the worm accommodation space does not protrude from the rack housing 17, and the electric power The steering device 200 is arranged in the dead space. Therefore, the mountability of the electric power steering device 200 including the first internal pressure adjusting unit 60 can be improved. Although not shown, a second internal pressure adjusting section 70 may be provided at the opening end of the second accommodation hole 55.

According to the second embodiment described above, the following effects can be obtained.

In the electric power steering device 200, the first internal pressure adjusting section 60 capable of adjusting the pressure in the accommodation space including the rack accommodation space, the shaft accommodation space, and the worm accommodation space is provided at the opening end of the first accommodation hole 54. As described above, the first internal pressure adjusting portion 60 is built in the dead space formed at the open end of the first housing hole 54 without being provided so as to project from the rack housing 17 or the worm housing 53. For this reason, it is possible to prevent the members provided around the electric power steering device 200 from interfering with the first internal pressure adjusting unit 60, and as a result, the electric power steering device 200 including the first internal pressure adjusting unit 60 with respect to the vehicle. The mountability can be improved.

Note that the following modified examples are also within the scope of the present invention, and the configurations described in the modified examples may be combined with the configurations described in the above-described embodiments, or the configurations described in different modified examples below may be combined. It is also possible.

In each of the above-described embodiments, the steering wheel 1 and the rack shaft 12 are mechanically connected via the steering shaft 11. The configuration of the electric power steering device is not limited to this, and the electric motor 21 may be connected to the rack shaft 12 via the reduction mechanism 50, and the steering wheel 1 and the rack shaft 12 are mechanically connected. A non-steer-by-wire electric power steering device may be used.

The configuration of the electric power steering device is a single pinion type electric power steering device in which the steering torque by the driver and the steering assist torque by the electric motor 21 are input to the rack shaft 12 via the common steering shaft 11. Good. In this case, the worm housing 53 cannot be provided with the first internal pressure adjusting section 60, and thus only the second internal pressure adjusting section 70 is provided.

Further, the first internal pressure adjusting unit 60 in each of the above-described embodiments has a support member 62. The configuration of the first internal pressure adjusting portion 60 is not limited to this, and the support member 62 is eliminated by having the worm housing 53 hold the seal portion 61d of the bellows 61 like the second internal pressure adjusting portion 70. The number of parts may be reduced. In this case, the bellows 61 may be fixed by connecting the holding member 63 to the worm housing 53 via a bolt, or may be fixed by welding the holding member 63 to the worm housing 53.

Further, the second internal pressure adjusting section 70 in each of the above-described embodiments does not have a member corresponding to the support member 62 of the first internal pressure adjusting section 60. The configuration of the second internal pressure adjusting unit 70 is not limited to this, and may be a configuration including a member corresponding to the support member 62. Further, the second internal pressure adjusting section 70 does not have a limiting section corresponding to the first limiting section 62d and the second limiting section 63c of the first internal pressure adjusting section 60, but may have a limiting section. Further, in the second internal pressure adjusting unit 70, the holding member 72 is welded and joined to the worm housing 53, but the holding member 63 may be joined to the worm housing 53 via a bolt.

Further, in the bellows 61, 71 in each of the above-described embodiments, the bottom portions 61a, 71a, the bellows portions 61b, 71b, and the flange portions 61c, 71c are formed of metal. The bellows 61, 71 are not limited to this, and the bottom portions 61a, 71a, the bellows portions 61b, 71b, and the flange portions 61c, 71c may be integrally formed of resin or the like, or the bottom portions 61a, 71a, 71a and the bellows portions 61b and 71b may be formed of metal, and the flange portions 61c and 71c may be formed of resin. In this way, at least the flange portions 61c, 71c of the bellows 61, 71 are made of resin, and the support member 62 to which the bellows 61, 71 are assembled are made of resin. It becomes possible to weld them, and as a result, the assembling property of the internal pressure adjusting parts 60, 70 can be improved. When the bellows 61, 71 are welded to the support member 62, the seal portions 61d, 71d may be provided separately from the bellows 61, 71.

Further, in each of the above-described embodiments, the ventilation holes 63b and 72a are provided with the filters 64 and 73 which are waterproof and moisture permeable membranes. When the positions where the vent holes 63b and 72a are provided are positions where there is no risk of splashing or submersion of water, the filters 64 and 73 may be mesh filters or micropore filters to reduce the manufacturing cost. May be.

Hereinafter, the configuration, operation, and effect of the embodiment of the present invention will be collectively described.

The electric power steering apparatus 100, 200 includes a rack shaft 12 having a rack 12a, a drive shaft 22 having a second pinion 23 meshing with the rack 12a, a worm wheel 52 provided on the drive shaft 22, and a worm meshing with the worm wheel 52. The shaft 51, the electric motor 21 that rotationally drives the worm shaft 51, the rack housing 17 that forms a rack housing space that houses the rack shaft 12, the worm wheel 52, and the worm shaft 51 that are housed and communicate with the rack housing space. The worm housing 53 includes a worm housing 53 in which a worm housing space is formed, and internal pressure adjusting units 60 and 70 that are provided in the worm housing 53 and adjust pressures in the rack housing space and the worm housing space. And a second accommodation hole 55 for accommodating the worm shaft 51, and the internal pressure adjusting portions 60, 70 include at least one of the first accommodation hole 54 and the second accommodation hole 55. It has bellows 61, 71 for closing the open ends, and the bellows 61, 71 are deformed according to the pressure difference between the external pressure and the pressure in the worm accommodating space.

In this configuration, the internal pressure adjusting portions 60 and 70 capable of adjusting the pressures in the rack accommodation space and the worm accommodation space are provided at the open ends of at least one of the first accommodation hole 54 and the second accommodation hole 55. As described above, the internal pressure adjusting portions 60 and 70 are not provided so as to project from the rack housing 17 or the worm housing 53, but are built in a dead space generated at the opening end of the first housing hole 54 or the opening end of the second housing hole 55. To be done. Therefore, the interference between the members provided around the electric power steering devices 100 and 200 and the internal pressure adjusting units 60 and 70 is avoided, and as a result, the electric power steering device 100 including the internal pressure adjusting units 60 and 70, It is possible to improve the mountability of the 200 in a vehicle.

Further, the internal pressure adjusting parts 60, 70 further include holding members 63, 72 for holding the bellows 61, 71 at their open ends, and the holding members 63, 72 are provided with vent holes 63b, 72a for the outside air to flow in and out. The ventilation holes 63b and 72a are provided with filters 64 and 73 that suppress passage of liquid and allow passage of gas.

In this structure, filters 64 and 73 that suppress passage of liquid and allow passage of gas are provided in the vent holes 63b and 72a that guide external pressure to the bellows 61 and 71. By thus providing the waterproof and moisture-permeable filters 64 and 73, it is possible to prevent water from entering the internal pressure adjusting units 60 and 70, and as a result, the electric power steering devices 100 and 200 are submerged or covered. It is possible to prevent water from entering the inside of the electric power steering devices 100 and 200 through the internal pressure adjusting units 60 and 70 when water is splashed. Further, in this configuration, water is prevented from entering the bellows 61, 71, so that the deformation of the bellows 61, 71 is prevented from being hindered by water, so that the internal pressure adjusting portions 60, 70 are stabilized. Can be activated.

Further, the internal pressure adjusting parts 60, 70 further include restricting parts 62d, 63c for restricting the deformation of the bellows 61, 71.

In this configuration, the limiting portions 62d and 63c that limit the deformation of the bellows 61 and 71 are provided. In this way, by limiting the deformation of the bellows 61, 71, it is possible to prevent the bellows 61, 71 from coming into contact with and damaging the surrounding members or sticking to the surrounding members. As a result, the bellows 61, 71 can be smoothly deformed according to the pressure difference.

Further, the bellows 61 is provided at the opening end of the first accommodation hole 54.

In this configuration, the bellows 61 is provided at the open end of the first housing hole 54 that houses the worm wheel 52. Since the outer diameter of the first housing hole 54 that houses the worm wheel 52 is larger than the outer diameter of the worm wheel 52, the outer diameter of the bellows 61 can be set relatively large. If the outer diameter of the bellows 61 is large, the volumes of the rack housing space and the worm housing space can be greatly changed even if the bellows 61 is slightly deformed. Therefore, the internal pressure adjusting unit 60 allows the rack housing space and the worm housing space to be housed. It is possible to quickly adjust the pressure in the space.

Further, the first central axis line CL1 of the first accommodation hole 54 and the second central axis line CL2 of the second accommodation hole 55 intersect at an angle when viewed from a direction orthogonal to the first central axis line CL1 and the second central axis line CL2. is doing.

In this configuration, the first central axis line CL1 of the first accommodation hole 54 and the second central axis line CL2 of the second accommodation hole 55 intersect at an angle. When the first central axis CL1 and the second central axis CL2 intersect at an angle, the width of the communication opening 57 that communicates the first accommodation hole 54 and the second accommodation hole 55 in the direction of the first central axis CL1 increases, and The dead space generated at the open end of the first accommodation hole 54 becomes large. In this way, by incorporating the internal pressure adjusting section 60 at the opening end of the first accommodation hole 54 in which a large dead space is generated, the mountability of the electric power steering apparatus 100 including the internal pressure adjusting section 60 on a vehicle can be improved. it can.

Further, a pair of tie rods 5 swingably connected to the rack shaft 12 and a boot 19 that covers the connecting portion 6 of the rack shaft 12 and the tie rod 5 and defines a part of the rack housing space are further provided. The bellows 61 and 71 are deformed with a pressure smaller than that of the boot 19.

In this configuration, the bellows 61, 71 are deformed with a pressure smaller than that of the boot 19. By making the bellows 61, 71 deform more easily than the boot 19, it is possible to reliably prevent the boot 19 from being deformed or damaged when a pressure difference occurs.

The membrane member is a bellows or a diaphragm.

In this configuration, the membrane member is a bellows or a diaphragm. As described above, by adopting the bellows or the diaphragm, which has a simple structure, as the film member, it is possible to reduce the manufacturing cost of the electric power steering devices 100 and 200 including the internal pressure adjusting units 60 and 70.

Although the embodiment of the present invention has been described above, the above embodiment merely shows a part of the application example of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

100, 200... Electric power steering device, 5... Tie rod, 6... Ball joint (connecting part), 12... Rack shaft, 12a... Rack, 17... Rack housing, 17a. ..Housing hole (first housing space), 19... Boots, 21... Electric motor, 22... Drive shaft, 23... Second pinion (pinion), 51... Worm shaft, 52 ... worm wheel, 53... worm housing, 54... first accommodation hole, 55... second accommodation hole, 57... communication opening, 60... first internal pressure adjusting portion (internal pressure adjustment Part), 61... Bellows (membrane member), 62... Support member, 62d... First restricting part (restricting part), 63... Holding member, 63b... Vent hole, 63c... -Second limiting portion (limiting portion), 64... Filter, 70... Second internal pressure adjusting portion (internal pressure adjusting portion), 71... Bellows (membrane member), 72... Holding member, 72a... ..Ventilation holes, 73... Filters, CL1... First central axis, CL2... Second central axis

Claims (7)

An electric power steering device,
A rack shaft having a rack,
A drive shaft having a pinion that meshes with the rack;
A worm wheel provided on the drive shaft,
A worm shaft that meshes with the worm wheel,
An electric motor for rotationally driving the worm shaft,
A rack housing in which a first housing space for housing the rack shaft is formed;
A worm housing for accommodating the worm wheel and the worm shaft, and forming a second accommodating space communicating with the first accommodating space;
An internal pressure adjusting portion provided in the worm housing for adjusting the pressure in the first accommodation space and the second accommodation space,
The second accommodation space has a first accommodation hole for accommodating the worm wheel and a second accommodation hole for accommodating the worm shaft,
The internal pressure adjusting section has a membrane member that closes an open end of at least one of the first accommodation hole and the second accommodation hole,
The electric power steering device according to claim 1, wherein the membrane member is deformed according to a pressure difference between an external pressure and a pressure in the second accommodation space. The internal pressure adjusting unit further includes a holding member that holds the membrane member at the opening end,
The holding member is provided with a vent hole through which outside air flows in and out,
The electric power steering apparatus according to claim 1, wherein a filter that suppresses passage of liquid and allows passage of gas is provided in the vent hole. The electric power steering apparatus according to claim 1, wherein the internal pressure adjusting unit further includes a limiting unit that limits deformation of the film member. The electric power steering apparatus according to claim 1, wherein the film member is provided at the opening end of the first accommodation hole. The first central axis of the first accommodation hole and the second central axis of the second accommodation hole intersect at an angle when viewed from a direction orthogonal to the first central axis and the second central axis. The electric power steering device according to claim 4, which is characterized in that. A pair of tie rods swingably connected to the rack shaft,
A boot that covers the connecting portion between the rack shaft and the tie rod and defines a part of the first housing space,
The electric power steering apparatus according to any one of claims 1 to 5, wherein the film member is deformed with a pressure smaller than that of the boot. 7. The electric power steering device according to claim 1, wherein the film member is a bellows or a diaphragm.

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