JP3845488B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in a steering gear box of an electric power steering apparatus.
[0002]
[Prior art]
In the electric power steering device, the magnitude and direction of the input torque from the steering side such as the steering wheel is detected by the torque detection device, and the assist force from the electric motor according to the detected value of the input torque is transmitted to the assist force transmission mechanism. The steering force is applied via In such a steering gear box of an electric power steering apparatus, a configuration in which a pinion shaft connected to the steering side, a torque detection device, an electric motor, an assist force transmission mechanism from the electric motor, and the like are unitized is disclosed in, for example, No. 8 and Japanese Patent Laid-Open No. 8-34355.
[0003]
FIG. 3 is a sectional view showing a steering gear box of the electric power steering apparatus disclosed in Japanese Patent Laid-Open No. 8-175403. As shown in the figure, the pinion shaft 101 is connected to the input shaft 104 supported by the upper half 103a of the pinion shaft housing portion 103 of the housing via the bearing 102, the torsion bar 105, and the bearings 106 and 107. The pinion shaft housing portion 103 includes a lower half portion 103 b and an output shaft 109 that is supported by the rack shaft housing portion 108.
[0004]
The input shaft 104 linked to the steering side is connected to the output shaft 109 via a torsion bar 105 housed in the hollow portion 110. On the other hand, a pinion 112 is formed on the outer periphery of the output shaft 109 protruding from the opening 111 between the pinion shaft housing portion 103 of the housing and the rack shaft housing portion 108 toward the rack shaft housing portion 108, and meshes with the pinion 112. The rack shaft 113 is linked to a steered side such as a wheel (not shown).
[0005]
The torque detection device includes a differential transformer 115 and a slide member 116. A cylindrical slide member 116 fitted to the outer periphery of the input shaft 104 and the output shaft 109 engages with a skew guide portion 117 formed on the input shaft 104, and a vertical direction guide portion formed on the output shaft 109. 118, and the torsion of the torsion bar 105 (relative rotation between the input shaft 104 and the output shaft 109) according to the magnitude and direction of the input torque is converted into the movement of the slide member 116 in the direction of the pinion shaft 101. It is detected via the dynamic transformer 115.
[0006]
The electric motor 119 that generates an assist force according to the detected value of the input torque is integrally held in the pinion shaft housing portion 103, and is connected to the output shaft 109 via an assist force transmission mechanism that includes the ring member 120 and the advance / retreat member 121. An assist force is applied to the.
[0007]
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 illustrated, an input shaft 203 supported via a bearing 202 on a cover 201a constituting an upper half of the pinion shaft housing portion 201 of the housing is connected to a lower half of the pinion shaft housing portion 201 via a torsion bar 204. Are connected to an output shaft 207 supported by a base 201b via a bearing 205 and a bearing 206. Similarly, the base 201b is opened to the rack shaft accommodating portion 208 that constitutes a part of the housing, and a pinion formed on the outer periphery of the output shaft 207 meshes with the rack shaft 209 accommodated in the rack shaft accommodating portion 208. The rack shaft 209 is linked to a steered side (not shown).
[0008]
Further, the torque detection device includes a slider 211 that slides in the axial direction of the pinion shaft (the input shaft 203 and the output shaft 207) according to the twist of the torsion bar 204, and a potentiometer 212 that detects the slide of the slider 211. Is housed in the cover 201a.
[0009]
The assist force transmission mechanism between the electric motor 213 and the output shaft 207 includes a small hypoid gear 214 on the outer periphery of the output shaft of the electric motor 213 and a large hypoid gear 215 on the outer periphery of the output shaft 207 that meshes with the small hypoid gear 214. Is housed inside.
[0010]
[Problems to be solved by the invention]
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 protrude from the openings at both ends of the steering gear box and are connected to the steered side via tie rods (not shown). However, the rack shaft 113 or the rack shaft 209 and the tie rod are covered with a dustproof and waterproof boot, and the rack shaft housing portion 108 or the rack shaft housing portion 201 is opened from the opening at both ends of the steering gear box. Intrusion of foreign matter such as muddy water into the water is prevented (see FIG. 1).
[0011]
However, such boots are easily damaged by, for example, stepping stones. When the boots are damaged, muddy water or the like enters from the outside into the rack shaft housing portion 108 or the rack shaft housing portion 201. In this case, in the conventional steering gear box as shown in FIGS. 3 and 4 described above, muddy water or the like reaches the pinion shaft housing portion 103 side or the pinion shaft housing portion 201 side.
[0012]
In other words, in the electric power steering apparatus of FIG. 3, the rack shaft housing portion 108 and the pinion shaft housing portion 103 communicate with each other through the opening 111, so that the muddy water that has entered from the damaged boot remains as it is. It penetrates into the housing 103 and reaches the bearing 106, the assist force transmission mechanism, and the torque detection device.
[0013]
In the electric power steering apparatus of FIG. 4, the first chamber A in which the torque detection device 210 in the cover 201a is accommodated, and the second chamber B in which the small hypoid gear 214 and the large hypoid gear 215 that are assist force transmission mechanisms are accommodated. Is sealed with the seal member 216 because the lubricating oil (grease) used in these chambers is different, but the rack shaft accommodating portion 208 and the inside of the base 201b communicate with each other as it is, so that the damaged boot The muddy water or the like that has entered the rack shaft accommodating portion 208 reaches the second chamber B through the base 201b.
[0014]
In the electric power steering apparatus shown in FIG. 3, the muddy water that has entered in this way passes through the ring member 120 and advance / retreat member 121 of the assist force transmission mechanism, the slide member 116 of the torque detector, the bearing 102, the bearing 106, etc. In the electric power steering apparatus of FIG. 4, the small hypoid gear 214, the large hypoid gear 215, the bearing 206, etc. of the assist force transmission mechanism are rusted, which causes malfunction and sticking.
[0015]
The present invention has been made paying attention to such problems, and even when the cover member at the end of the steering gear box is damaged, the assist force transmission mechanism, the torque detection device, etc. in the steering gear box can be used as muddy water. An object of the present invention is to provide an electric power steering device that can appropriately protect against foreign objects.
[0016]
[Means for Solving the Problems]
1st invention meshes | engages with the pinion shaft provided with the input shaft into which an input torque is input from a steering wheel, the output shaft connected with the said input shaft via a torsion bar, and the pinion of the said output shaft tip outer periphery A rack shaft linked to the wheel side at the end, a torque detection device that detects an input torque to the pinion shaft, an electric motor that applies assist force to steering based on a detection signal from the torque detection device, A pinion housing that houses the input side of the pinion shaft; an opening that opens toward the pinion housing ; a coupling housing that houses a meshing portion of the pinion and the rack shaft; and the rack shaft. A rack-side housing to be accommodated, and a cover member that covers an open end of the rack-side housing from which an end of the rack shaft extends. The electric power steering system wherein the output shaft and a seal member provided in a gap between the opening of the connecting housing, the foreign matter is the pinion side entering from the open end of the rack housing at breakage of the cover member The torque detection device was accommodated in the pinion side housing while preventing it from entering the inside of the housing.
[0017]
The second invention comprises an assist force transmission mechanism for transmitting the assist force from the electric motor to the pinion shaft, accommodating the assist force transmission mechanism to the pinion housing.
[0018]
[Action]
In the first invention, when input torque is input from the steering wheel side to the pinion shaft, the pinion on the outer periphery of the pinion shaft slides the rack shaft, and the wheel side linked to the rack shaft is steered. Is applied with an assist force from the electric motor according to the magnitude and direction of the input torque detected by the torque detector, and power assist appropriate for steering is performed. In this case, the front end of the rack shaft protrudes from the open end of the housing and is linked to the wheel side. However, according to the present invention, the cover member covering the open end of the housing is damaged by stepping stones or the like, and foreign matter such as muddy water from the open end. Even if the intrusion occurs, the seal member provided between the region in which the housing accommodates the input end side of the pinion shaft and the region in which the housing accommodates the rack shaft makes the region that accommodates the input end side of the pinion shaft Intrusion of foreign objects is prevented. Therefore, the torque detection device accommodated in this region, the bearing that supports the pinion shaft, etc. are not adversely affected by rust due to foreign matters such as muddy water, and malfunctions and sticking do not occur. The correct operation of the electric power steering device is guaranteed and the reliability of the device is significantly improved.
[0019]
In the second invention, the assist force transmission mechanism is protected from foreign matters 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 there is no problem in assist force transmission. The correct operation of the electric power steering device is guaranteed and the reliability of the device is significantly improved.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0021]
FIG. 1 shows the overall configuration of the steering gear box of the electric power steering apparatus.
[0022]
As shown in the figure, the housing 1 of the steering gear box includes a pinion side housing 3 that houses the input side of the pinion shaft 2, and a connecting portion housing 4 that houses a meshing portion (see FIG. 2) of the pinion gear 51 and the rack gear 52. , And a rack-side housing 5 that houses a rack shaft 6 extending from the connecting portion housing 4. The pinion-side housing 3 is mounted so as to cover the upper part of the connecting portion housing 4. In addition to the pinion shaft 2, a torque detection device and an assist force transmission mechanism are accommodated and an electric motor 20 is attached, as will be described later.
[0023]
Both ends of the rack shaft 6 projecting from the open ends 1a, 1b at both ends of the housing 1 of the steering gear box are connected to tie rods 9, 10 connected to the steered side (not shown) via ball joints 7, 8, respectively. . A boot 11 and a boot 12 as cover members are put on the connecting portions between the both ends of the rack shaft 6 and the tie rods 9 and 10, respectively, so that dust and water resistance in the gear box housing 1 is achieved.
[0024]
FIG. 2 is a cross-sectional view of the electric power steering apparatus shown in FIG.
[0025]
As illustrated, the pinion shaft 2 includes an input shaft 21, an output shaft 22, and a torsion bar 23. The input shaft 21 is accommodated in the pinion side housing 3 with one end protruding, and is linked to a steering side (steering wheel or the like) (not shown) on the protruding end side, and this protruding end is connected to the inner periphery of the pinion side housing 3 via a bearing 24. The other end is supported on the surface and the inner diameter hole 25 of the output shaft 22. A torsion bar 23 is accommodated in the hollow portion 26 of the input shaft 21, and one end of the torsion bar 23 is fixed to the input shaft 21 via a pin 27 and the other end is connected to an output shaft 22 via a serration 28. Fixed to. As a result, the input shaft 21 and the output shaft 22 are relatively rotated by the amount of twist of the torsion bar 23 caused by the input torque.
[0026]
A sleeve 30 is mounted on the outer periphery of the pinion shaft 2. A female helical spline 31 is formed on the inner periphery of the sleeve 30 on the input shaft 21 side. The helical spline 31 is a male type formed on the outer periphery of the portion between the bearing 24 and the inner diameter hole 25 of the input shaft 21. Mesh with the helical spline 32. An axial groove 33 extending in the direction of the pinion shaft 2 is formed on the inner peripheral surface of the sleeve 30 on the output shaft 22 side, and a pin 34 press-fitted into the output shaft 22 is engaged with the axial groove 33. As a result, when the torsion bar 23 is twisted according to the input torque and the input shaft 21 and the output shaft 22 rotate relative to each other, the sleeve 30 moves along the spiral trajectory of the cam mechanism including the helical splines 31 and 32 along the pinion shaft 2. It slides in the axial direction.
[0027]
On the other hand, a step portion 35 is formed on the outer periphery of the sleeve 30, and a detection lever 37 of a potentiometer 36 attached to the side of the pinion side housing 3 is engaged with the step portion 35. As a result, 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 incorporates a spring member (not shown) that presses the detection lever 37 against the step portion 35 so that the step portion 35 of the detection lever 37 moves integrally and the backlash of the sleeve 30 is prevented. ing. The torque detection device includes the potentiometer 36 and the sleeve 30.
[0028]
A collar 41 is press-fitted into 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 a flange portion 41 a formed on the outer periphery of the collar 41 and the flange portion 41 a. The lower ring 43 is locked while being restrained in the axial direction. The ring 43 is fixed to the collar 41 by being plastically deformed in the radial direction after being inserted into a groove on the outer periphery of 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 accommodated in the connecting portion housing 4 is press-fitted into the bearing hole 44 of the connecting portion housing 4. The bearing 45 is rotatably supported. Since the bearing 45 is in the connecting portion housing 4 and is not protected from muddy water or the like by the oil seal 60 described later, it is preferable to use a non-ferrous material that does not cause rusting problems in advance.
[0029]
A worm wheel 47 is press-fitted into the outer periphery of the output shaft 22, and the worm wheel 47 meshes with a worm 46 with 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 assist force from the electric motor 20 according to the magnitude and direction of the input torque from the torque detector is output via the worm 46 and the worm wheel 47. It is applied to the shaft 22.
[0030]
The pinion gear 51 at the outer periphery of the output shaft 22 is accommodated in the connecting portion housing 4 through the opening 4 a and meshes with the rack gear 52 of the rack shaft 6. The rack shaft 6 is biased on the back surface by a spring 54 via a pressure pad 53, and the meshing of the pinion gear 51 and the rack gear 52 is ensured. The spring 54 is assembled to a plug 56 that is fixed to the connecting portion housing 4 by a nut 55.
[0031]
Further, a step 4b is formed at the end of the opening 4a, and an oil seal 60 is press-fitted into the step 4b as a feature of the present invention. The oil seal 60 closes the annular gap formed between the opening 4a of the connecting portion housing 4 and the output shaft 22, and the boot 11 or 12 shown in FIG. Even if foreign matter such as muddy water enters from both ends of the gear box housing 1, the foreign matter is prevented from entering the pinion side housing 3, and the assist force transmission mechanism, torque detection device, and bearing 42 in the pinion side housing 3 are prevented. Etc. are to be protected.
[0032]
An oil seal 61 is press-fitted on the protruding end side of the input shaft 21, and 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 the pinion side housing 3 and the connecting portion housing. 4 is provided with an O-ring 63, and an attachment portion of the potentiometer 36 to the pinion-side housing 3 is provided with an O-ring 64, and a seal within the pinion-side housing 3 is achieved.
[0033]
Next, the operation will be described.
[0034]
In the power steering device of the present invention, when input torque is input to the input shaft 21 from the steering side such as a steering wheel, the outer periphery of the output shaft 22 is caused by the rotation of the output shaft 22 connected to the input shaft 21 via the torsion bar 23. The pinion slides the rack shaft 6 and the steered side linked to the rack shaft 6 is steered. The rotational torque of the output shaft 22 is based on the torsion of the torsion bar 23 and the torque detection device (sleeve 30). The assist torque from the electric motor 20 according to the magnitude and direction of the input torque detected by the potentiometer 36) is applied via the assist force transmission mechanism (worm 46 and worm wheel 47), and power assist suitable for steering. Is made.
[0035]
By the way, the tip of the rack shaft 6 that transmits the torque from the output shaft 22 to the steered side is connected to the tie rods 9 and 10 via the ball joints 7 and 8. Covered and foreign matter such as muddy water entering the housing 1 from the open ends 1a and 1b is prevented. 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 steering gear box from the open ends 1a and 1b of the housing 1.
[0036]
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. The foreign matter that has entered from the open ends 1 a and 1 b of the steering gear box housing 1 does not enter the inside of the pinion side housing 3. Therefore, in the present invention, the assist force transmission mechanism (worm 46 and worm wheel 47) accommodated in the pinion side housing 3, the torque detection device (sleeve 30 and potentiometer 36), the bearing 24 that supports the input shaft 21, the output Since foreign matter such as muddy water reaches the bearing 42 that supports the shaft 22 and does not cause, for example, rusting and the like, the malfunction and sticking of these devices are prevented, so that the power steering device can be accurately used. Operation is guaranteed.
[0037]
In the embodiment shown in FIGS. 1 and 2, the assist force transmission mechanism (worm 46 and worm wheel 47) is provided in the pinion side housing 3 that accommodates the pinion shaft 2, and assist force from the electric motor 20. However, according to the present invention, the electric motor 20 and the assist force transmission mechanism are arranged apart from the pinion shaft 2 to which the input torque is applied, and the assist force from the electric motor 20 is increased. Of course, the present invention can also be applied to an electric power steering device that is made to act directly on the rack shaft 6 via an assist force transmission mechanism (for example, a second pinion). It is possible to effectively protect the bearings, the torque detection device, and the like from entry of foreign matter such as muddy water.
[0038]
【The invention's effect】
According to the first invention, even when the cover member covering the housing open end is damaged by a flying stone or the like and foreign matter such as muddy water enters from the open end, the housing accommodates the input end side of the pinion shaft. The seal member provided between the housing and the region for accommodating the rack shaft prevents foreign matter from entering the region for accommodating the input end side of the pinion shaft. Therefore, the torque detection device accommodated in this region, the bearing that supports the pinion shaft, etc. are not adversely affected by foreign matter such as muddy water, etc., and malfunction and adhesion do not occur. The correct operation of the electric power steering device is guaranteed and the reliability of the device is significantly improved.
[0039]
According to the second invention, the assist force transmission mechanism is protected from foreign matters such as muddy water by the seal member in the region where the housing accommodates the input end side of the pinion shaft, and therefore the assist force transmission is not hindered. Therefore, the proper operation of the electric power steering apparatus is ensured, and the reliability of the apparatus is remarkably 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.
2 is a cross-sectional view taken along the line AA of the steering gear box of FIG. 1; FIG.
FIG. 3 is a cross-sectional view showing a conventional steering gear box.
FIG. 4 is a cross-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 Connection part housing 4a Opening part 4b Step 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)

A pinion shaft including an input shaft to which input torque is input from the steering wheel, and an output shaft connected to the input shaft via a torsion bar;
A rack shaft that meshes with the pinion on the outer periphery of the output shaft tip and that is linked to the wheel side at the end;
A torque detection device for detecting an input torque to the pinion shaft;
An electric motor for applying an assist force to steering based on a detection signal from the torque detection device;
A pinion side housing for accommodating the input side of the pinion shaft;
A connection portion housing having an opening that opens toward the pinion-side housing, and housing a meshing portion between the pinion and the rack shaft;
A rack-side housing that houses the rack shaft;
An electric power steering apparatus comprising: a cover member that covers an open end of the rack-side housing from which an end of the rack shaft extends;
A seal member is provided in a gap between the output shaft and the opening of the connecting portion housing so that foreign matter that has entered from the open end of the rack side housing when the cover member is broken does not enter the inside of the pinion side housing. In addition, an electric power steering device characterized in that the torque detection device is accommodated in the pinion side housing. An assist force transmission mechanism for transmitting an assist force from the electric motor to the pinion shaft;
The electric power steering apparatus according to claim 1, wherein the assist force transmission mechanism is housed in the pinion-side housing.

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