JPH10258749A - Electrically powered steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly protect an assist force transmission mechanism or a torque detection device in a steering gear box from foreign matters such as muddy water even if a cover member of the end part of the steering gear box is broken. SOLUTION: In the housing of a steering gear box, an oil seal 60 is pressed into the opening part 4a of a connecting part housing 4 for housing an engaged part between the pinion gear 51 of a pinion shaft 2 and the rack gear 52 of a rack shaft 6 and, by sealing a gap between the output shaft 22 of the pinion shaft 2 and the opening part 4a, an assist force transmission mechanism, a torque detector, a bearing 42 for supporting the pinion shaft 2 or the like housed in a pinion side housing 3 together with the input shaft 21 side of the pinion shaft 2 is protected from the incursion of foreign matters from the open end of the housing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in a steering gear box of an electric power steering device.

[0002]

2. Description of the Related Art In an electric power steering device, the magnitude and direction of input torque from a steering side such as a steering wheel is detected by a torque detection device, and an assisting force from an electric motor according to the detected value of the input torque is detected. ,
It is added to the steering force via the assist force transmission mechanism. In a steering gear box of such an electric power steering device, a configuration in which a pinion shaft connected to a steering side, a torque detection device, an electric motor, a mechanism for transmitting assist force from the electric motor, and the like are unitized is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-1.
It has been proposed in Japanese Patent Application Laid-Open No. 75403 and Japanese Patent Application Laid-Open No. 8-34355.

FIG. 3 is a sectional view showing a steering gear box of the electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 8-175403. As shown, the pinion shaft 101 is connected to an input shaft 1 that is supported by a top half 103a of a pinion shaft receiving portion 103 of a housing via a bearing 102.
04, torsion bar 105, bearings 106, 107
The output shaft 109 is supported by the lower half 103b of the pinion shaft housing 103 and the rack shaft housing 108 via
Consists of

[0004] An input shaft 104 linked to the steering side is connected to an output shaft 109 via a torsion bar 105 housed in a hollow portion 110. On the other hand, the opening 1 between the pinion shaft receiving portion 103 and the rack shaft receiving portion 108 of the housing.
The output shaft 10 protruding from the rack shaft 11 toward the rack shaft housing 108
A pinion 112 is formed around the outer periphery of the pinion 9.
The rack shaft 113 that meshes with the wheel 12 is linked to a steered side such as wheels (not shown).

[0005] The torque detector comprises a differential transformer 115,
It is composed of a slide member 116. The cylindrical slide member 116 fitted on the outer periphery of the input shaft 104 and the output shaft 109 is provided with a skew guide portion 117 formed on the input shaft 104.
And the torsion of the torsion bar 105 according to the magnitude and direction of the input torque (relative rotation between the input shaft 104 and the output shaft 109). Is converted into the movement of the slide member 116 in the direction of the pinion shaft 101, and the differential transformer 1
15 is detected.

An electric motor 119 that generates an assisting force according to the detected value of the input torque is integrally held by a pinion shaft receiving portion 103, and is transmitted through an assisting force transmission mechanism including a ring member 120 and an advancing / retreating member 121. An assist force is applied to the output shaft 109.

FIG. 4 is a sectional view showing a steering gear box of an electric power steering apparatus disclosed in Japanese Patent Application Laid-Open No. 8-34355. As shown, a cover 201 constituting an upper half of a pinion shaft receiving portion 201 of a housing is provided.
a of the input shaft 203 supported on the pinion shaft 201 through a torsion bar 204.
Is connected to an output shaft 207 supported via a bearing 205 and a bearing 206 on a base 201b constituting the lower half. The base 201b is opened on the side of the rack shaft accommodating portion 208 which also forms a part of the housing, and the output shaft 20 is attached to the rack shaft 209 accommodated in the rack shaft accommodating portion 208.
The pinions formed on the outer periphery of the gear 7 mesh with each other. Rack shaft 20
9 is linked to a steered side (not shown).

The torque detecting device is provided with a slider 2 which slides in the axial direction of the pinion shaft (input shaft 203 and output shaft 207) in accordance with the torsion of the torsion bar 204.
11 and a potentiometer 212 for detecting the sliding of the slider 211, which are housed in the cover 201a.

The assist force transmitting mechanism between the electric motor 213 and the output shaft 207 includes a small hypoid gear 214 on the outer periphery of the electric motor 213 and the small hypoid gear 2.
Large hypoid gear 2 on the outer periphery of the output shaft 207 that meshes with
15 and housed in the cover 201a.

[0010]

By the way, in such an electric power steering apparatus, the rack shaft 113 in FIG. 3 and the rack shaft 209 in FIG. 4 respectively protrude from the openings at both ends of the steering gear box, and have tie rods (not shown). The rack shaft 113 or the connection between the rack shaft 209 and the tie rods is covered with dustproof and waterproof boots.
Foreign matter such as muddy water is prevented from entering the rack shaft housing 108 or the rack shaft housing 201 from the openings at both ends of the steering gear box (see FIG. 1).

However, such a boot is easily damaged by, for example, a stepping stone, and if the boot is damaged, the rack shaft accommodating portion 108 or the rack shaft accommodating portion 201 is damaged.
Mud water or the like from the outside enters into the inside, but in this case, in the conventional steering gear box as shown in FIGS.
Side or the pinion shaft housing 201 side.

That is, in the electric power steering apparatus shown in FIG. 3, the rack shaft housing 108 and the pinion shaft housing 1
Since the muddy water that has entered from the damaged boot enters the pinion shaft receiving portion 103 as it is, the muddy water that has entered from the damaged boot enters the bearing 106, the assist force transmitting mechanism, and the torque detecting device. Will reach.

In the electric power steering apparatus shown in FIG. 4, a first chamber A in which the torque detecting device 210 in the cover 201a is accommodated, and a small hypoid gear 214 and a large hypoid gear 215 which are assist force transmitting mechanisms are accommodated. The two chambers B are sealed by the seal member 216 because the lubricating oil (grease) used in these chambers is different. However, since the rack shaft housing 208 and the inside of the base 201b communicate with each other as they are, Muddy water or the like that has entered the rack shaft housing 208 from the damaged boot is removed from the base 201b.
It reaches the second chamber B through the inside.

In the electric power steering apparatus shown in FIG. 3, the muddy water that has entered in this way is the ring member 120 and the advance / retreat member 121 of the assist force transmission mechanism, the slide member 116 of the torque detector, the bearing 102, the bearing 106, and the like. 4, the small hypoid gear 214, the large hypoid gear 215, the bearing 206, and the like of the assist force transmission mechanism are rusted, respectively, which causes malfunction and sticking.

The present invention has been made in view of such a problem. Even when a cover member at an end of a steering gear box is damaged, an assist force transmitting mechanism, a torque detecting device, and the like in the steering gear box are provided. It is an object of the present invention to provide an electric power steering device capable of appropriately protecting the vehicle from foreign substances such as muddy water.

[0016]

According to a first aspect of the present invention, there is provided a pinion shaft having an input end connected to a steering wheel side and having a pinion on an outer periphery on an output end side; A rack shaft linked to the wheel side in the section, a torque detection device for detecting an input torque to a pinion shaft, an electric motor for applying an assist force to steering based on a detection signal from the torque detection device, and the pinion shaft An electric power steering apparatus comprising: a housing for accommodating a rack shaft; and a cover member for covering an open end of the housing from which an end of the rack shaft extends, wherein the housing accommodates an input end side of the pinion shaft. A seal member is provided between a region where the housing accommodates the rack shaft and a region where the housing accommodates the rack shaft. When the member is damaged, foreign matter that has entered from the end of the housing is prevented from entering the region where the housing accommodates the input end side of the pinion shaft, and the torque detecting device is connected to the input end side of the pinion shaft. Was accommodated in the area for containing.

According to a second aspect of the present invention, there is provided an assist force transmitting mechanism for transmitting an assist force from the electric motor to the pinion shaft, and the assist force transmitting mechanism is provided in an area where the housing accommodates the input end side of the pinion shaft. Housed.

[0018]

According to the first aspect of the invention, when an input torque is input to the pinion shaft from the steering wheel side, the pinion on the outer periphery of the pinion shaft slides on the rack shaft, and the wheel side linked to the rack shaft is steered. The steering force is provided with an assist force from the electric motor according to the magnitude and direction of the input torque detected by the torque detection device, and power assist appropriate for steering is performed. In this case, the tip of the rack shaft projects from the open end of the housing and is linked to the wheel side. However, according to the present invention, the cover member that covers the open end of the housing is damaged by flying stones or the like, and foreign matter such as muddy water from the open end. When the housing enters the pinion shaft, the housing accommodates the input end of the pinion shaft and the housing accommodates the rack shaft. Prevents entry of foreign matter. Therefore, the torque detecting device and the bearing supporting the pinion shaft accommodated in this region are not adversely affected by rust or the like due to foreign matter such as muddy water, and do not malfunction or stick. Proper operation of the electric power steering device is guaranteed, and the reliability of the device is significantly improved.

In the second invention, the assist force transmission mechanism includes:
In the area where the housing accommodates the input end side of the pinion shaft, the sealing member protects the foreign matter such as muddy water, so that the transmission of the assist force is not hindered, and the correct operation of the electric power steering device is guaranteed. In addition, the reliability of the device is significantly improved.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows the overall structure of a steering gear box of an electric power steering apparatus.

As shown in the figure, a housing 1 of the steering gear box is connected to a pinion-side housing 3 for accommodating an input side of a pinion shaft 2 and a meshing portion (see FIG. 2) of a pinion gear 51 and a rack gear 52. The housing includes a housing 4 and a rack-side housing 5 that houses a rack shaft 6 extending from the connection housing 4. The pinion-side housing 3 is mounted so as to cover the upper part of the connecting portion housing 4, and in addition to the pinion shaft 2,
As will be described later, the torque detection device and the assist force transmission mechanism are housed, and the electric motor 20 is attached.

[0023] Housing 1 for steering gear box
Both ends of the rack shaft 6 protruding from the open ends 1a and 1b at both ends are connected to tie rods 9 and 10 connected to a steered side (not shown) via ball joints 7 and 8, respectively. Boots 11 and 12 as a cover member are put on the connecting portions between both ends of the rack shaft 6 and the tie rods 9 and 10, respectively, so as to prevent dust and water in the gear box housing 1.

FIG. 2 is a sectional view of the electric power steering apparatus taken along line AA of FIG.

As shown, the pinion shaft 2 includes an input shaft 21, an output shaft 22, and a torsion bar 23. The input shaft 21 is housed in the pinion-side housing 3 with one end protruding, and is linked with a steering side (steering wheel or the like) (not shown) on the protruding end side.
This protruding end is connected to the pinion side housing 3 via a bearing 24.
The other end is supported by the inner peripheral surface of the output shaft 22 and the other end is supported by the inner diameter hole 25 of the output shaft 22. A torsion bar 23 is housed in the hollow portion 26 of the input shaft 21.
Is fixed to the input shaft 21 via a pin 27, and the other end is fixed to the output shaft 22 via a serration 28. Thus, the input shaft 21 and the output shaft 22 are relatively rotated by the amount of twist of the torsion bar 23 due to the input torque.

A sleeve 30 is provided around the outer periphery of the pinion shaft 2.
Is attached. A female helical spline 31 is formed on the inner periphery of the sleeve 30 on the input shaft 21 side, and the helical spline 31 is a male helical spline formed on the outer periphery of a portion between the bearing 24 and the inner diameter hole 25 of the input shaft 21. Mesh with the helical spline 32 of the above. Also, the output shaft 2 of the sleeve 30
An axial groove 3 extending in the direction of the pinion shaft 2 is formed on the inner peripheral surface on the second side.
A pin 34 press-fitted into the output shaft 22 is engaged with the axial groove 33. Thereby, when the torsion bar 23 is twisted according to the input torque, and the input shaft 21 and the output shaft 22 rotate relatively, the sleeve 30
It slides in the axial direction of the pinion shaft 2 along the spiral trajectory of the cam mechanism including the helical splines 31 and 32.

On the other hand, a step 35 is formed on the outer periphery of the sleeve 30, and a detection lever 37 of a potentiometer 36 mounted on the side of the pinion side housing 3 is engaged with the step 35. Thus, the detection lever 37 is moved according to the movement of the sleeve 30 in the direction of the pinion shaft 2, and the magnitude and direction of the input torque are detected. The potentiometer 36 has a built-in spring member (not shown) for pressing the detection lever 37 against the step portion 35.
Of the sleeve 30 is prevented, and the backlash of the sleeve 30 is prevented. The torque detector is
It comprises the potentiometer 36 and the sleeve 30.

A collar 41 is press-fitted on the outer periphery of the output shaft 22, and an inner ring of a bearing 42 provided at a joint portion between the pinion side housing 3 and the connecting portion housing 4 is formed with a flange portion 41 a formed on the outer periphery of the collar 41. Locked while being restrained in the axial direction with the ring 43 below the flange 41a. After inserting the ring 43 into the groove on the outer periphery of the collar 41,
It is plastically deformed in the radial direction and fixed to the collar 41. The input shaft 21 side of the output shaft 22 is rotatably supported by the bearing 42, and the distal end side of the output shaft 22 housed in the connecting portion housing 4 is pressed into a bearing hole 44 of the connecting portion housing 4. The bearing 45 is rotatably supported by the bearing 45. The bearing 45 is connected to the connecting portion housing 4.
Since the oil seal 60 is not protected from muddy water and the like by an oil seal 60 described later, a non-ferrous material that does not cause a problem of rust in advance may be used.

A worm wheel 47 is pressed into the outer periphery of the output shaft 22, and the worm wheel 47 meshes with a worm 46 to which the output of the electric motor 20 is linked. The worm 46 and the worm wheel 47 constitute an assist force transmission mechanism, and the electric motor 20 according to the magnitude and direction of the input torque from the torque detector.
Is applied to the output shaft 22 via the worm 46 and the worm wheel 47.

The pinion gear 51 on the outer periphery of the tip of the output shaft 22
Are housed in the connecting portion housing 4 through the opening 4a,
It meshes with the rack gear 52 of the rack shaft 6. The rack shaft 6 is connected to a spring 54 via a pressure pad 53.
As a result, the rear surface is urged, and the engagement between the pinion gear 51 and the rack gear 52 is ensured. The spring 54 is
It is assembled to a plug 56 fixed to the connecting portion housing 4 by a nut 55.

Further, a step 4b is formed at an end of the opening 4a, and an oil seal 60 is press-fitted into the step 4b as a feature of the present invention.
With this oil seal 60, the oil seal 60 closes an annular gap created between the opening 4a of the connecting portion housing 4 and the output shaft 22, and temporarily closes the boot 11 shown in FIG.
Or, even if 12 is damaged and foreign matter such as muddy water enters from both ends of the housing 1 of the steering gear box,
This foreign matter is prevented from entering the pinion side housing 3 side, and an assist force transmission mechanism in the pinion side housing 3 is provided.
The torque detecting device, the bearing 42 and the like are protected.

An oil seal 61 is press-fitted into the protruding end of the input shaft 21, an O-ring 62 is provided between the inner peripheral surface of the hollow portion of the input shaft 21 and the torsion bar 23, and An O-ring 63 is provided at a joint portion with the connecting portion housing 4, and an O-ring 64 is provided at a portion where the potentiometer 36 is attached to the pinion-side housing 3, thereby sealing the inside of the pinion-side housing 3.

Next, the operation will be described.

In the power steering apparatus according to the present invention, when an input torque is input to the input shaft 21 from a steering side such as a steering wheel, the output shaft 22 is connected to the input shaft 21 via the torsion bar 23 to output the torque. The pinion on the outer periphery of the shaft 22 slides the rack shaft 6, and the steered side associated with the rack shaft 6 is steered. The rotational torque of the output shaft 22 includes a torque detecting device based on the torsion of the torsion bar 23. The assist torque from the electric motor 20 according to the magnitude and direction of the input torque detected by the (sleeve 30 and the potentiometer 36) is applied via the assist force transmission mechanism (the worm 46 and the worm wheel 47) and is suitable for steering. Power assist is performed.

The tip of the rack shaft 6 for transmitting the torque from the output shaft 22 to the steered side is connected to the tie rods 9 and 10 via ball joints 7 and 8,
The connecting portion is covered by boots 11 and 12 to prevent foreign matter such as muddy water from entering the housing 1 from the open ends 1a and 1b. However, the boots 11 and 12 may be damaged by flying stones or the like while the vehicle is running. In this case, foreign matter such as muddy water enters the inside of the steering gear box from the open ends 1a and 1b of the housing 1.

On the other hand, in the present invention, the oil seal 60 is press-fitted into the opening 4a on the outer periphery of the output shaft 22, and the oil seal 60 closes the gap between the opening 4a and the output shaft 22. Therefore, foreign matter that has entered from the open ends 1a and 1b of the housing 1 of the steering gear box does not enter the inside of the pinion-side housing 3. Therefore, in the present invention, the assist force transmission mechanism (the worm 46) housed in the pinion-side housing 3 is used.
And a worm wheel 47), a torque detecting device (sleeve 30 and potentiometer 36), a bearing 24 supporting the input shaft 21, a bearing 42 supporting the output shaft 22, and the like. The operation of these devices is prevented from malfunctioning and sticking, and proper operation of the power steering device is guaranteed.

In the embodiment shown in FIGS. 1 and 2, the assist force transmission mechanism (the worm 46 and the worm wheel 47) is provided in the pinion-side housing 3 that accommodates the pinion shaft 2, and the electric motor 20 Is applied to the output shaft 22. However, in the present invention, the electric motor 20 and the assist force transmission mechanism are arranged separately from the pinion shaft 2 to which the input torque is applied,
Naturally, the present invention can also be applied to an electric power steering device in which the assist force from the electric motor 20 is applied directly to the rack shaft 6 via an assist force transmission mechanism (for example, a second pinion). In addition, it is possible to effectively protect the bearing, the torque detecting device, and the like in the steering gear box from foreign matter intrusion such as muddy water.

[0038]

According to the first aspect of the present invention, even if the cover member covering the open end of the housing is broken by a flying stone or the like and foreign matter such as muddy water enters from the open end, the housing remains on the input end side of the pinion shaft. The seal member provided between the area for housing the rack shaft and the area for housing the rack shaft prevents foreign matter from entering the area for housing the input end side of the pinion shaft. Therefore, the torque detecting device and the bearing supporting the pinion shaft accommodated in this region are not adversely affected by rust or the like due to foreign matter such as muddy water, and do not malfunction or stick. Proper operation of the electric power steering device is guaranteed, and the reliability of the device is significantly improved.

According to the second aspect of the present invention, the assist force transmission mechanism is protected from foreign matter such as muddy water by the seal member in the region where the housing accommodates the input end side of the pinion shaft, so that the assist force transmission is not hindered. This does not occur, correct operation of the electric power steering device is guaranteed, and the reliability of the device is significantly improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a steering gear box according to an embodiment of the present invention.

FIG. 2 shows the steering gear box of FIG.
It is A sectional drawing.

FIG. 3 is a sectional view showing a conventional steering gear box.

FIG. 4 is a sectional view showing another conventional steering gear box.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 1a Open end 1b Open end 2 Pinion shaft 3 Pinion side housing 4 Connecting part housing 4a Opening 4b Stepped part 5 Rack side housing 6 Rack shaft 7 Ball joint 8 Ball joint 9 Tie rod 10 Tie rod 11 Boot 12 Boot 20 Electric motor 21 Input shaft 22 Output shaft 23 Torsion bar 30 Sleeve 36 Potentiometer 46 Worm 47 Worm wheel 51 Pinion gear 52 Rack gear 60 Oil seal

Claims (2)

[Claims] 1. A pinion shaft linked to a steering wheel at an input end and provided with a pinion on an outer periphery on an output end side, and a rack shaft engaged with a pinion on an outer periphery of the pinion shaft and linked to a wheel at an end. A torque detection device that detects an input torque to a pinion shaft; an electric motor that applies assisting force to steering based on a detection signal from the torque detection device; a housing that houses the pinion shaft and a rack shaft; An electric power steering apparatus comprising: a cover member that covers an open end of the housing from which an end of a rack shaft extends; and an area in which the housing houses an input end side of the pinion shaft; and the housing includes the rack shaft. A seal member is provided between the housing member and the housing. Foreign matter intruding from the end of the pinion is prevented from entering the region where the housing accommodates the input end side of the pinion shaft, and the torque detecting device is moved to the region where the housing accommodates the input end side of the pinion shaft. An electric power steering device characterized by being housed. 2. An assist force transmitting mechanism for transmitting an assist force from the electric motor to the pinion shaft, wherein the housing accommodates the assist force transmitting mechanism in an area for accommodating an input end side of the pinion shaft. The electric power steering device according to claim 1, wherein