Vehicle steering system

Abstract

Even if it is difficult to create an ideal steering angle difference between the left and right steering wheels using the suspension geometry during steering, this system will enable the creation of a stable steering angle difference between the left and right steering wheels. [Solution] The vehicle's steering device comprises a steering mechanism having a rack shaft connected to steering knuckles that support the left and right steering wheels and steers the steering wheels; a suspension arm that swingably connects the vehicle body and the knuckle arm; a stabilizer bar arranged along the steering mechanism to suppress the roll of the vehicle body, the ends of which of the stabilizer bar are connected to the suspension arm, a stabilizer bush that supports the stabilizer bar rotatably and slidably in the vehicle width direction relative to the vehicle body, and a link lever that connects the rack shaft and the stabilizer bar and slides the stabilizer bar relative to it in the opposite direction to the sliding direction of the rack shaft.

Description

Technical Field

[0001] The present invention relates to a steering device for a vehicle.

Background Art

[0002] For vehicles such as automobiles, in order to make the running during turning smooth, when the steering wheel (mainly the front wheels) is steered, the central axes of each wheel are set to intersect at one point. The center of turning is set on the extension line of the wheels that are not steered (mainly the rear wheels). And there is known Ackermann geometry in which the extension lines of the axles of the left and right steering wheels intersect at this turning center, and all the wheels turn around the same turning center.

[0003] By turning the vehicle according to Ackermann geometry, smooth turning without burden on the tires becomes possible. In Ackermann geometry, a steering angle difference (Ackermann angle) occurs in which the steering angle of the steering wheel on the inner side of the turn is larger than the steering angle of the steering wheel on the outer side of the turn.

[0004] This Ackermann angle is realized by suspension geometry (the geometric shape and positional relationship of the elements constituting the suspension).

[0005] However, due to restrictions in the vehicle body structure such as brake design, it is difficult to obtain an ideal steering angle difference with suspension geometry even when the steering angle becomes large. As a result, the steering feeling deteriorates, and furthermore, abnormal noise during steering and uneven wear due to dragging on the tires occur.

[0006] Therefore, the applicant proposed in Patent Document 1 (Japanese Patent No. 5374282) a technique for increasing the steering angle of the inner steering wheel during turning by utilizing the fact that the suspension arm (lower arm) that supports the inner steering wheel during turning is pulled in the direction of the turning center by the cornering force, displacing the rear bush provided at the connecting portion between the suspension arm and the vehicle body, and rotating the suspension arm by this displacement.

Prior Art Documents

[0007] [Patent Document 1] Patent No. 5374282 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The techniques disclosed in the aforementioned literature increase the steering angle of the steering wheel on the inside of the turn, thereby bringing the Ackermann angle closer to the Ackermann geometry.

[0009] However, this paper describes using cornering force to increase the steering angle of the inner steering wheel during a turn. Cornering force changes depending on the vehicle speed and turning curvature during a turn. Therefore, the amount of increase in the steering angle of the inner steering wheel is not constant, making it difficult to always obtain a stable steering feel.

[0010] The present invention aims to provide a vehicle steering system that can provide a stable steering angle difference between the left and right steering wheels, even when it is difficult to achieve an ideal steering angle difference between the left and right steering wheels with the suspension geometry during steering, thereby obtaining a good steering feel. [Means for solving the problem]

[0011] The present invention relates to a steering device for a vehicle comprising: a steering mechanism having a rack shaft whose ends are connected to left and right steering knuckles that support the left and right steering wheels and which steers the steering wheels; a suspension arm that swingably connects the vehicle body and a knuckle arm provided on the steering knuckle; and a stabilizer bar arranged along the steering mechanism to suppress the roll of the vehicle body, wherein both ends of the stabilizer bar are connected to the suspension arm, and the stabilizer bar is further supported by a stabilizer bush that is rotatable and slidable relative to the vehicle body in the vehicle width direction, and a link lever that connects the rack shaft and the stabilizer bar and slides the stabilizer bar relative to it in the opposite direction to the sliding direction of the rack shaft. [Effects of the Invention]

[0012] According to the present invention, both ends of the stabilizer bar are connected to the suspension arms, and the stabilizer bar is supported relative to the vehicle body via stabilizer bushings so that it can rotate and slide in the vehicle width direction. The stabilizer bar and the rack shaft are connected by a link lever, and the stabilizer bar is made to slide relative to the rack shaft in the opposite direction to the sliding direction. As a result, even when it is difficult to create an ideal steering angle difference between the left and right steering wheels with the suspension geometry during steering, the stabilizer bar displaces the suspension arms, making it possible to create a stable steering angle difference between the left and right steering wheels. As a result, a good steering feel can be obtained. [Brief explanation of the drawing]

[0013] [Figure 1] Schematic plan view showing the steering mechanism of the steering wheel. [Figure 2] Schematic plan view of the steering mechanism showing the movement of the left and right steering wheels during a right turn. [Figure 3] Partial plan view of the steering mechanism showing the movement of the inner steering wheel during a right turn. [Figure 4] Characteristic diagram showing the change in steering angle with respect to rack stroke of the steering inner wheel during turning. [Figure 5] Characteristic diagram showing the change in steering angle with respect to rack stroke of the steering outer wheel during turning. [Modes for carrying out the invention]

[0014] An embodiment of the present invention will be described below with reference to the drawings. The steering device 1 shown in Figure 1 is installed at the front of the vehicle. This steering device 1 steers the left and right steering wheels (front wheels) 2l and 2r in conjunction with the operation of a steering wheel (not shown) or the drive of an EPS (Electric Power Steering) motor.

[0015] This steering device 1 has a steering mechanism 3. The steering mechanism 3 is, for example, a rack and pinion type and is arranged in the vehicle width direction. The steering gearbox 3a of this steering mechanism 3 is fixed to the vehicle frame. A rack shaft 3b is supported within this steering gearbox 3a so as to be able to reciprocate and slide in the axial direction. A pinion formed on a pinion shaft meshes with a rack (not shown) formed on this rack shaft 3b. This pinion shaft is connected to the steering shaft. A steering wheel operated by the driver is fixed to the base end of this steering shaft.

[0016] Both ends of the rack shaft 3b protrude from both ends of the steering gearbox 3a. The ends of tie rods 4 are connected to both ends of this rack shaft 3b via ball joints 6. The ends of these tie rods 4 (tie rod ends) are pivotably connected via ball joints 6 to the front end of the knuckle arm 5a of the steering knuckle 5, on the vehicle width side.

[0017] This knuckle arm 5a is integrally formed with the steering knuckle 5. The steering knuckle 5 rotatably supports the axles to which the left and right steering wheels 2l, 2r are fixed. The lower part of a suspension (not shown) is fixed to the steering knuckle 5. The steering knuckle 5 rotates the left and right steering wheels 2l, 2r together with the suspension about the kingpin axis to determine the travel of the host vehicle. When the driver operates the steering wheel or the EPS motor is driven, the rack shaft 3b of the steering mechanism 3 rotates the steering knuckle 5 via the tie rod 4.

[0018] Also, the rear end portion on the vehicle width direction inner side of the knuckle arm 5a is connected to the outer end portion in the vehicle width direction of a suspension arm (lower arm) 7 via a ball joint 8. The front and rear of the inner end portion of the suspension arm 7 are swingably connected to the vehicle body frame via rubber bushes 9, 10. The hardness of the rubber bush 10 is high and rigid. In contrast, the hardness of the rubber bush 9 is low and soft compared to the hardness of the rubber bush 10.

[0019] Also, a stabilizer bar 12 of a stabilizer 11 is disposed in front of the steering mechanism 3. The stabilizer 11 has this stabilizer bar 12 and stabilizer links 13. The stabilizer bar 12 is a rod-shaped member having spring properties such as spring steel.

[0020] The central portion of the stabilizer bar 12 is disposed parallel to the steering mechanism 3. Also, both end portions 12a of the stabilizer bar 12 are bent in the direction of the suspension arm 7. Further, stabilizer bushes 14 are mounted on the left and right of the central portion of the stabilizer bar 12 at a predetermined interval. A bracket (not shown) is mounted on the outer periphery of this stabilizer bush 14. This bracket is fixed to the vehicle body frame. The stabilizer bush 14 supports the stabilizer bar 12 so as to be rotatable about the axis and slidable in the axial direction.

[0021] One end of the stabilizer link 13 is connected to the end 12a of the stabilizer bar 12 via a ball joint 18a. Also, the other end of the stabilizer link 13 is the front end of the suspension arm 7 and is connected via a ball joint 18b on the extension of one end of the stabilizer link 13. The stabilizer bar 12 generates torsional stress when the vehicle turns and a stroke difference occurs between the left and right suspensions, and suppresses the rolling (tilting) of the vehicle body by its restoring force.

[0022] Also, the portion of the stabilizer bar 12 sandwiched by the stabilizer bush 14 and the rack shaft 3b provided in the steering mechanism portion 3 are connected via a link lever 15. The middle of this link lever 15 is rotatably supported by the vehicle body frame via a support shaft 16. The link lever 15 relatively slides the stabilizer bar 12 in the opposite direction with respect to the slide of the rack shaft 3b. Also, long holes 15a are formed at both ends of the link lever 15.

[0023] Pin shafts 17a and 17b are inserted through both of these long holes 15a. One pin shaft 17a is implanted in the stabilizer bar 12. The other pin shaft 17b is implanted in the rack shaft 3b. The long holes 15a are formed such that the long side direction is along the long side direction of the link lever 15. The width of the short side of this long hole 15a is the same as or slightly wider than the diameter of the pin shafts 17a and 17b. Although not shown, a relief hole for allowing the movement of the pin shaft 17b that slides together with the rack shaft 3b is drilled in the steering gear box 3a. The relief hole and the pin shaft 17b are covered with a rubber boot having a sealing property. The internal sealing property is maintained by this rubber boot.

[0024] The tip of the pin shaft 17b protrudes from the rubber boot. The protruding portion of this pin shaft 17b is inserted through the long hole 15a.

[0025] When the rack shaft 3b slides, the stabilizer bar 12 slides relatively in the opposite direction via the link lever 15. The amount of slide of the stabilizer bar 12 relative to the rack shaft 3b is adjusted by changing the lever ratio from the support shaft 16 to both pin shafts 17a and 17b. When the stabilizer bar 12 slides relative to the rack shaft 3b in the opposite direction, the stabilizer links 13 connected to both ends displace the left and right suspension arms 7. This increases the steering angle of the inner wheel and decreases the steering angle of the outer wheel, thereby widening the difference in steering angles between the two wheels.

[0026] Next, the operation of the steering device 1 with this configuration will be explained. In the following explanation, the vehicle will be described using the example of turning to the right. Therefore, the left and right will be reversed when turning to the left. Also, as shown in Figure 2, when turning to the right, the right steering wheel (front wheel) 2r becomes the inner steering wheel, and the left steering wheel (front wheel) 2l becomes the outer steering wheel.

[0027] When a vehicle enters a right-hand curve or attempts to change lanes to the right, and the driver operates the steering wheel or the driver assistance system drives the EPS motor, the rack shaft 3b of the steering mechanism 3 is supported by the steering gearbox 3a and slides toward the right steering wheel 2r. Then, the tie rod 4 connected to the rack shaft 3b rotates the steering knuckle 5 around the kingpin axis via the knuckle arm 5a, causing the steering wheels 2l and 2r to have a steering angle in the turning direction. At this time, due to the well-known suspension geometry, the steering angle θin of the right steering wheel 2r is greater than the steering angle θou of the left steering wheel 2l, resulting in a greater steering difference.

[0028] Furthermore, during driving, the movement of the suspension is transmitted to the suspension arm 7 via the steering knuckle 5. When a roll moment is generated in the vehicle towards the outside of the turn due to cornering, a torsional reaction force (restoring force) is generated in the stabilizer bar 12, which is connected to the suspension arm 7 via the stabilizer link 13. This suppresses the occurrence of roll.

[0029] By the way, as the steering angles of the steering wheels 2l and 2r gradually increase, it becomes difficult to obtain the ideal steering angle difference (Ackermann angle) between the left and right steering wheels 2l and 2r using the suspension geometry.

[0030] In this embodiment, the stabilizer bar 12 is used to increase the steering angle difference. That is, as shown in Figure 2, when the rack shaft 3b slides toward the right steering wheel 2r, the link lever 15, which is connected to one end of the rack shaft 3b via a pin shaft 17b and supported by the support shaft 16, rotates in the counterclockwise direction in Figure 2.

[0031] Then, this link lever 15 presses against the stabilizer bar 12, which is connected to the other end via a pin shaft 17a. As a result, the stabilizer bar 12, while supported by the stabilizer bush 14, slides in the opposite direction to the sliding direction of the rack shaft 3b.

[0032] When the stabilizer bar 12 slides in the opposite direction to the sliding direction of the rack axis 3b, the right end 12a of the stabilizer bar 12 pulls the right suspension arm 7 forward via the stabilizer link 13. On the other hand, the left end 12a of the stabilizer bar 12 pushes the left suspension arm 7 backward via the stabilizer link 13.

[0033] The rubber bushing 10 supporting the suspension arm 7 is hard. The rubber bushing 9, on the other hand, is relatively soft. When the stabilizer bar 12 pulls the right suspension arm 7 forward, the suspension arm 7 attempts to displace in the counterclockwise direction shown by the arrows in Figures 2 and 3, with the hard rubber bushing 10 as the center and the softer rubber bushing 9 elastically deforming.

[0034] During a turn, the vehicle body experiences roll towards the outside of the turn. As a result, the stabilizer bar 12 experiences a downward reaction force due to the twist caused by this roll. This reaction force acts as stress on the left and right suspension arms 7. Consequently, the right suspension arm 7 is subjected to both the forward pulling force from the stabilizer bar 12 and the reaction force due to the twist of the stabilizer bar 12.

[0035] The load applied to the right suspension arm 7 is transmitted to the knuckle arm 5a via the ball joint 8. The steering knuckle 5, which is integrated with the knuckle arm 5a, is supported so as to be rotatable about the kingpin axis. The steering knuckle 5 is integrated with the suspension and is allowed to move vertically.

[0036] Therefore, the steering knuckle 5 is pushed downward by both the displacement caused by the counterclockwise load applied to the right suspension arm 7 and the reaction force caused by the twisting of the stabilizer bar 12. As a result, the distance (radius) between the kingpin axis and the end of the tie rod 4 of the suspension arm 7 appears to shorten. Therefore, as shown in Figure 4, as the stroke of the rack axis 3b increases, the steering angle θ of the right steering wheel 2r increases by Δθin.

[0037] On the other hand, the left suspension arm 7 is pressed towards the rear of the vehicle by the stabilizer link 13. The stabilizer link 13 bends slightly when pressing against the left suspension arm 7. Therefore, the left suspension arm 7 is displaced by a smaller amount than the right suspension arm 7. In this case, the left suspension arm 7 is simultaneously subjected to a load due to the upward reaction force from the stabilizer bar 12.

[0038] The load applied to the left suspension arm 7 is transmitted to the knuckle arm 5a via the ball joint 8. As a result, the left steering knuckle 5 is pushed upward by the load from the left suspension arm 7. Consequently, the apparent distance (radius) between the kingpin axis and the end of the tie rod 4 of the suspension arm 7 becomes longer. Therefore, as shown in Figure 5, as the stroke of the rack axis 3b decreases, the steering angle θ of the left steering wheel 2l decreases by Δθou.

[0039] Thus, when the vehicle is turned, as the rack stroke of the rack axis 3b increases toward the inside of the turn, the steering angle of the right steering wheel 2r increases by θin + Δθin, and the steering angle of the left steering wheel 2l decreases by θou - Δθou, as shown in Figures 4 and 5. Therefore, the difference in steering angles between the two steering wheels increases by Δθin + Δθuo.

[0040] As a result, even when it is difficult to achieve an ideal steering angle difference between the left and right steering wheels 2l and 2r using the suspension geometry during cornering, the radius of the suspension arm 7 appears to shorten by displacing the suspension arm 7 with the stabilizer bar 12 on the inside of the turn. Conversely, the radius of the left suspension arm 7 appears to lengthen slightly by displacing the suspension arm 7 with the stabilizer bar 12 on the outside of the turn. Therefore, by adjusting the lever ratio of the link lever 15 for each vehicle model, the steering angle difference can be brought closer to the ideal value.

[0041] Thus, in this embodiment, when the steering mechanism 3 is operated during cornering, the stabilizer bar 12 slides in the opposite direction to the sliding direction of the rack axis 3b due to the operation of the link lever 15. As a result, on the steering inner wheel side, the suspension arm 7 is pulled forward, and the radius of the suspension arm 7 appears to become shorter. On the other hand, on the steering outer wheel side, the suspension arm 7 is pushed backward, and the radius of the suspension arm 7 appears to become slightly shorter.

[0042] As a result, the steering angle of the inner steering wheel increases, and the steering angle of the outer steering wheel decreases, thus widening the steering angle difference. This widening of the steering angle difference can be set by adjusting the lever ratio of the link lever 15. Therefore, by adjusting the lever ratio of the link lever 15, even when it is difficult to achieve an ideal steering angle difference between the left and right steering wheels with the suspension geometry during cornering, it becomes possible to achieve a stable steering angle difference between the left and right steering wheels, resulting in a good steering feel.

[0043] Furthermore, the present invention is not limited to the embodiments described above. For example, the steering device 1 can be applied not only to front-wheel steering but also to rear-wheel steering and four-wheel steering. [Explanation of Symbols]

[0044] 1... Steering device, 2l, 2r…Steering wheel (front wheel), 3…Steering mechanism, 3a... Steering gearbox, 3b... Rack axis, 4...Tie rod, 5... Steering knuckle, 5a... Knuckle arm, 6... Ball joint, 7…Suspension arm (lower arm), 8... Ball joint, 9,10…Rubber bushings, 11… Stabilizer, 12... Stabilizer bar, 12a...end, 13… Stabilizer link, 14… Stabilizer bushing, 15... Link lever, 15a...long hole, 16...Support shaft, 17a, 17b... pin axis, 18a, 18b... Ball joint, θin, θou… rudder angle

Claims

1. A steering mechanism having a rack shaft that steers the steering wheels, with both ends connected to left and right steering knuckles that support the left and right steering wheels, A suspension arm that swingably connects the vehicle body and the knuckle arm provided on the steering knuckle, A stabilizer bar is positioned along the steering mechanism to suppress the roll of the vehicle body. In a steering device of a vehicle equipped with, Both ends of the stabilizer bar are connected to the suspension arm, A stabilizer that supports the aforementioned stabilizer bar with respect to the vehicle body so as to be rotatable and slidable in the vehicle width direction of the vehicle body, A link lever is provided to connect the rack shaft and the stabilizer bar, and to slide the stabilizer bar relative to the rack shaft in the opposite direction to the sliding direction of the rack shaft. A steering device for a vehicle, further comprising the following:

2. The link lever is rotatably supported in the middle by the vehicle body via a support shaft, and the rack shaft and the stabilizer bar are connected to the link lever on the opposite side of the support shaft. The steering device for a vehicle according to claim 1, characterized in that it is a steering device for a vehicle.

3. The suspension arm is supported by the vehicle body via a bushing that is elastically deformable. The steering device for a vehicle according to claim 1, characterized in that it is a steering device for a vehicle.

4. The stabilizer bar and the suspension arm are connected via a stabilizer link. The steering device for a vehicle according to claim 1, characterized in that it is a steering device for a vehicle.

5. The lever ratio from the support shaft of the link lever to the rack shaft and the stabilizer bar is set to be variable. The steering device for a vehicle according to claim 2.

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