JPH0532237U - Four-wheel steering system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a connecting mechanism that mechanically connects a front wheel side steering member and a rear wheel side steering mechanism with play.
While increasing the force that can be transmitted by this connecting mechanism,
Increase credibility. A rotary shaft 53 that rotates in synchronization with the movement of a steering wheel has a driving-side bevel gear 54 and a driven-side bevel gear 59.
The cylindrical cam 60 is rotated via and. The engagement of the cam groove 62 of the cylindrical cam 60 and the cam pin 61 causes the rod 55 to be displaced in the axial direction. The rod 55 is not displaced at the neutral position of the cam groove 62,
Displaces at both ends. The first connecting rod 17 that swings with the displacement of the rod 55 drives the rear wheel side steering mechanism.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The four-wheel steering system according to the present invention is used as a steering system for an automobile, and when the course of the automobile is changed, not only the front wheels but also the rear wheels are changed in direction to reduce the turning radius. It also helps to maintain driving stability.

[0002]

[Prior Art]

 To reduce the turning radius of the vehicle so that the course can be changed easily on a narrow road, or to maintain the stability of the vehicle even when changing the course at high speeds, use the steering wheel. In recent years, four-wheel steering systems that move not only the front wheels but also the rear wheels when operated have become popular.

Further, in order to avoid the risk that a large steering angle is given to the rear wheels during high-speed traveling, increasing the steering angle of the rear wheels is performed only in relation to the steering angle of the front wheels, and the rear wheels are made smaller. Steering can be done independently of the steering of the front wheels, so that the stability of the vehicle at high speeds is ensured and the turning performance is improved when the vehicle is parked. A steering device is conventionally known as described in Japanese Patent Application Laid-Open No. 2-237869.

First, a conventionally known four-wheel steering system to which the present invention is applied will be described with reference to FIGS. In FIG. 11, reference numeral 1 denotes a rack which is a front wheel side steering member, which meshes with a pinion 3 which is rotated by a steering wheel 2, and is displaced in the left and right direction of FIG. Add a steering angle. An arm piece 4 is fixed to the end of the rack 1, and one end of a cable 7 constituting a Bowden wire 6 is loosely inserted into a through hole 5 formed at the tip of the arm piece 4. .. A pair of stoppers 8a, 8b are fixedly provided at one end of the cable 7 so as to move the rack 1 only when the arm piece 4 collides with the stoppers 8a, 8b. Is transmitted to the cable 7, thereby forming a play mechanism for preventing the displacement of the input side rod 10 which is an input member of the rear wheel side steering mechanism 9 which will be described later when the operation amount of the steering wheel 2 is small. is doing.

That is, in a state where the steering wheel 2 is not rotated in any direction (state in which the vehicle is traveling straight), the arm piece 4 exists at an intermediate position between the pair of stoppers 8a and 8b. However, there is a play of length L 1 between each side of the arm piece 4 and each of the stoppers 8a and 8b. Therefore, when the displacement amount H of the rack 1 is smaller than the play (L> H), the movement of the rack 1 is not transmitted to the cable 7, but the displacement amount H of the rack 1 is larger than the play. When it becomes large (L <H), the movement of the rack 1 is transmitted to the cable 7.

The other end of the cable 7 is connected to one end portion (the left end portion in FIG. 11) of the input side rod 10 that constitutes the rear wheel side steering mechanism 9. A pair of stop rings 11 and 11 are provided at an intermediate portion of the input side rod 10 at intervals, and a pair of stop rings 12 and 12 are provided on the surfaces of the stop rings 11 and 11 facing each other. A compression spring 13 is provided between the two retaining rings 12 to support the inner peripheral edge portion. The outer peripheral edge portions of the retaining rings 12, 12 are opposed to the inward flange-shaped portions 15, 15 formed in the opening portions at both ends of the casing 14, respectively. The casing 14 is supported on a substrate or the like that supports the rear wheel side steering mechanism 9. As a result, the input side rod 10 is in the neutral position shown in the figure unless external force is applied (the cable 7 is not pushed or pulled). Held in.

Reference numeral 16 denotes an output side rod which constitutes the rear wheel side steering mechanism 9 together with the input side rod 10 and steers the rear wheel by moving in the axial direction (the left and right direction in FIG. 11). The output side rod 16 and the input side rod 10 are arranged substantially parallel to each other. However, in order to allow relative displacement with the first connecting rod 17 described below, at least if necessary, One rod 10 (or 16) is supported on the vehicle body so as to be slightly swingable.

At the intermediate portion of the first connecting rod 17 which has both ends thereof pivotally supported by the input side rod 10 and the output side rod 16 as described above, a second connecting rod is provided via a pivoting member 20. The middle portion of the cord 21 is connected. Then, one end of the second connecting rod 21 is pivotally supported on the end portion of the spool 23 of the hydraulic pressure switching valve 22.

A cylinder 23 of a hydraulic switching valve 22, which includes a spool 23 inside the cylinder 24 so as to be freely displaced in the axial direction, has a hydraulic oil supply port 26 communicating with a discharge port of a hydraulic oil pump 25 and an oil supply port 26. A discharge port 28 communicating with the tank 27 and first and second ports 32, 33 communicating with first and second chambers 30, 31 of a hydraulic cylinder 29, which will be described later, are formed respectively, and The communication between the pressure oil supply port 26 and the discharge port 28 and the communication between the first port 32 and the second port 33 is switched based on the displacement in the axial direction.

Further, the outer peripheral edge portions of the retaining rings 35, 35 fitted onto the base end portion and the tip end portion of the projecting rod 34 protrudingly provided on the one end surface of the spool 23 are formed on the inner peripheral surface of the cylinder 24. The spool 23 is held at the neutral position (the position shown in FIG. 12) unless the external force is applied to the spool 23 by facing the step portions 36, 36 and providing a compression spring 37 between the two retaining rings 35, 35. The pressure oil supply port 26 and the discharge port 28 are directly communicated with each other, so that pressure oil is not supplied to or discharged from any of the chambers 30 and 31 of the hydraulic cylinder 29 described later.

On the other hand, similar retaining rings 38, 38 and compression springs 39 are provided around the intermediate portion of the output side rod 16, and the outer peripheral edge of each retaining ring 38, 38 is provided in the hydraulic cylinder 29 described below. By facing the steps 40, 40 formed on the inner peripheral surface, the output side rod 16 is held in the neutral position and no steering angle is given to the rear wheels unless external force is applied.

A hydraulic cylinder 29 is provided at a position surrounding the output side rod 16, and a piston 41 fixed to an outer peripheral surface of an intermediate portion of the output side rod 16 is provided in the hydraulic cylinder 29 in an oil-tight and axial direction. It is fitted so that it can move freely. The first and second chambers 30 and 31 located on both sides of the piston 41 in the hydraulic cylinder 29 and the first and second ports 32 and 33 of the hydraulic pressure switching valve 22 are , Second hydraulic passages 42, 43 are connected to each other.

On the other hand, one end of the spool 23 of the hydraulic pressure switching valve 22 is pivotally supported at one end thereof, and an intermediate portion thereof is swingably coupled to an intermediate portion of the first connecting rod 17 via a pivot support member 20. A nut piece 44 is pivotally attached to the other end of the second connecting rod 21. The nut piece 44 is formed on the outer peripheral surface of the output shaft of the stepping servomotor 45 mounted on the fixed portion of the vehicle body. The male screw portion 46 is screwed together. Therefore, with the rotation of the stepping servomotor 45, the second connecting rod 21 swings around the pivot member 20 to move the spool 23 in the axial direction.

The stepping servomotor 45 is rotated by a command signal from the controller 47 in a suitable direction by a suitable angle (rotation speed). The control unit 47 has a built-in microcomputer. The control unit 47 has two steering wheels 48 provided in the vicinity of the handle shaft 48 in order to detect the rotation angle of the steering wheel 2 and the rotation angular velocity of the steering wheel 2. The angle sensors 49a and 49b, the vehicle speed sensor 50 for detecting the vehicle speed, the magnitude of the reaction force generated in the steering device for the front wheels, the acceleration (G) applied in the lateral direction of the vehicle body, and the vehicle body that accompanies the side wind or sloping ground. Signals are input from various sensors that detect one or more elements selected from among those that affect the operation of the vehicle, such as stress.

Then, the controller 47 rotates the stepping servomotor 45 in an appropriate direction and at an appropriate angle (rotation speed) in accordance with the operating condition of the vehicle, which is obtained according to the signals sent from the respective sensors. Let With the rotation of the stepping servomotor 45, the nut piece 44 is displaced in the axial direction based on the screw engagement with the male screw portion 46, and the second connecting rod 21 having the end portion pivotally supported by the nut piece 44. , But swings around the pivot member 20. Further, the second connecting rod 21 displaces the spool 23 in the axial direction thereof.

Such movement of the stepping servomotor 45 is performed by a rotation angle sensor 51 that directly detects the rotation angle of the stepping servomotor 45 and a displacement sensor 52 that detects the amount of displacement of the nut piece 44 in the axial direction. The detected signals are input to the controller 47.

In the case where the conventional four-wheel steering system configured as described above is used and steering of the vehicle is performed while relating steering angle imparting to the rear wheels to steering angle imparting to the front wheels, steering wheel 2 When the rotation angle is small, the arm piece 4 provided at the end of the rack 1 does not collide with any of the stoppers 8a and 8b, the cable 7 is not pushed and pulled, and the steering angle is set to the rear wheel. It will not be granted. Further, in order to greatly change the traveling direction of the vehicle, the steering wheel 2 is turned greatly, and when the displacement amount of the rack 1 increases, the arm piece 4 abuts against any stopper 8a (or 8b), Push and pull the cable 7.

As a result, the input side rod 10 of the rear wheel side steering mechanism 9 is displaced by an amount L smaller than the displacement amount of the rack 1 in accordance with the displacement of the rack 1. Pivot portion a between the input rod 10 and one end of the first connecting rod 17, from a ₀ position in FIG. 14, moving up to a ₁ position of the figure, the first connecting rod 17, the output side The first connecting rod 17, which has been in the state shown by the solid line in FIG. 14 until then, is displaced as shown by the broken line in FIG. Along with this, the pivot member 20 connecting the intermediate portions of the first connecting rod 17 and the second connecting rod 21 is moved from the c ₀ position in FIG. 14 to the c ₁ position in the same figure. Move up to.

As a result, the pivotal support part d between the second connecting rod 21 and the spool 23 moves from the position d _{0 to the} position d _{1 in the} figure, and the spool 23 in the state shown in FIG. The relationship with the cylinder 24 is changed to the state shown in FIG. 13, and the ports 26, 28, 32, 33 of the hydraulic switching valve 22 are switched, and the pressure oil supply port 26 and the first port 32 (or The second port 33), the discharge port 28 and the second port 33 (or the first port 32) communicate with each other, and the first chamber 30 (or the second port 30) of the hydraulic cylinder 29 is connected. The pressure oil is sent to the chamber 31) through the first hydraulic passage 42 (or the second hydraulic passage 43), and the oil is supplied from the second chamber 31 (or the first chamber 30) to the second hydraulic passage. It is discharged through the passage 43 (or the first hydraulic passage 42). At the moment when the hydraulic pressure switching valve 22 is switched in this way, the output side rod 16 has not moved yet, and the pivotal support portion b between the first connecting rod 17 and the output side rod 16 is at the b ₀ position in FIG. Exists in.

As described above, the ports 26, 28, 32, 33 of the hydraulic pressure switching valve 22 are switched according to the movement of the spool 23, and the hydraulic pressure is changed via the first and second hydraulic pressure passages 42, 43. When pressure oil is supplied to and discharged from the cylinder 29, the output side rod 16 moves in the axial direction via the piston 41 fitted in the hydraulic cylinder 29, and the rear wheels are steered.

Along with the movement of the output side rod 16, the pivotal support portion b between the first connecting rod 17 and the output side rod 16 moves from the position b _{0 to the} position b _{1 in} FIG. When the one connecting rod 17 becomes the state shown by the chain line in the same figure, the pivotal support member 20 connecting the intermediate part of the first connecting rod 17 and the intermediate part of the second connecting rod 21 to each other c ₁ position located et c ₀ moves up to the position (back). As a result, the displacement of the pivot member 20, which connects the intermediate portion of the first connecting rod 17 and the intermediate portion of the second connecting rod 21 whose one end is pivotally supported by the spool 23, is eliminated.

This displacement correction, that is, the operation of moving the position of the pivot member 20 as c ₀ → c ₁ → c ₀ by the movement of the input side rod 10 and the output side rod 16 in the axial direction is instantaneously performed. since the rope lines, in practice, about the first connecting rod 17 as if c ₀ position to the fixing of the pivot member 20, until the state shown by the chain line in FIG from the state shown by the solid line in FIG. 14 The movement of the input-side rod 10 is transmitted to the output-side rod 16 as if it were rotated, and the steering of the rear wheels is performed in association with the steering of the front wheels.

Therefore, the steering angle of the rear wheels in this case can be made sufficiently large in consideration of safety, and the turning radius of the vehicle can be made small.

Next, when steering the rear wheels independently of the front wheels, a signal from a sensor (not shown) that detects the state of the vehicle or a signal that indicates the steering state detected by the steering angle sensors 49a and 49b. Based on the above, the controller 47 sends a signal to the stepping servomotor 45, and the stepping servomotor 45 connects the nut piece 44 and one end of the second connecting rod 21 via the male screw portion 46 and the nut piece 44. The pivot point e of FIG. ₀ E from position₁ Move to position. Along with this, the second connecting rod 21 rotates about the pivot member 20 from the state shown by the solid line to the state shown by the broken line in FIG. The pivot part d with the spool 23 is ₂ From position d₃ Move to position. Along with this, the spool 23 of the hydraulic switching valve 22 moves in an appropriate direction by an appropriate length in accordance with the direction and magnitude of the disturbance detected by the sensor.

With the movement of the spool 23, the ports 26, 28, 32, 33 of the hydraulic switching valve 22 are switched, and the hydraulic cylinder 29 is switched through the first and second hydraulic passages 42, 43. The pressure oil is supplied to and discharged from the output side rod 16, and the output side rod 16 is moved in the axial direction via the piston 41.

As a result, the pivotal support portion b between the output side rod 16 and the first connecting rod 17, which had been in the b ₂ position in FIG. 15 until then, moved to the b ₃ position in the same figure, and The steering of the wheels is performed independently of the front wheels regardless of the movement of the input side rod 10.

In this way, when the output side rod 16 axially moves by an amount necessary and sufficient for appropriately steering the rear wheels, the intermediate portions of the first and second connecting rods 17 and 21 are brought into contact with each other. The pivot member 20 which is connected to each other moves from the c ₂ position in FIG. 15 to the c ₃ position in FIG. 15, and the second connecting rod 21 moves from the broken line position to the chain line position around the e ₁ position. By pivoting, the pivotal support part d between the other end of the second connecting rod 21 and the spool 23 moves (returns) from the d ₃ position to the d ₂ position in the figure. For this reason, the spool 23 and the cylinder 24, which have been in the state as shown in FIG. 13 until then (when each part moves in the direction of FIG. 15, the spool 23 is actually switched in the opposite direction). The relative positional relationship is in a neutral state as shown in FIG. As a result, the supply and discharge of pressure oil to and from the hydraulic cylinder 29 is stopped, the output side rod 16 does not move any further, and the steering angle of the rear wheels is fixed. When the disturbance is eliminated, the reverse operation eliminates the steering angle of the rear wheels.

After all, in the case of the conventional four-wheel steering device described in the above publication, the front wheel steering angle θ _F given to the front wheels and the rear wheel steering given to the rear wheels according to the movement of the steering wheel 2. The relationship with the angle θ _R is as shown in FIG. That is, when no disturbance such as lateral acceleration is applied to the vehicle, the rear wheel steering angle θ _R changes according to the front wheel steering angle θ _F as shown by the solid line a in the figure. However, when a disturbance is applied to the vehicle, the rear-wheel steering angle θ _R changes within a certain range centered on the solid line a, as shown by the slanted grid in the figure, to ensure vehicle stability. Try to.

[0029]

[Problems to be solved by the device]

 By the way, in the case of putting the conventional four-wheel steering device configured and working as described above into practical use, it is desired to improve the following points in order to stabilize the operation state of the vehicle.

That is, in the conventional four-wheel steering system, when the operation amount of the steering wheel 2 is small, a play mechanism for not displacing the input side rod 10 which is an input member of the rear wheel side steering mechanism. Is provided between the cable 7 of the Bowden wire 6 and the arm piece 4 fixed to the rack 1, it is difficult to transmit a large force from the rack 1 to the input side rod 10, and the four-wheel steering device is It is inevitable that the degree of freedom in designing will decrease.

Further, since the cable 7 of the Bowden wire 6 does not move as long as the operation amount of the steering wheel 2 is small, the cable 7 may be rusted or dewed unless sufficient rust prevention and dew condensation prevention are aimed at. , There is a risk of malfunction.

Further, although it is inevitable that the cable 7 slightly expands as it is used for a long period of time, the characteristics of the four-wheel steering system change by that amount when expanded, which is also preferable. Absent.

The four-wheel steering system of the present invention was devised in view of the above-mentioned circumstances.

[0034]

[Means for solving the problem]

 Each of the four-wheel steering devices of the present invention is similar to the above-described conventional four-wheel steering device and is used to steer the front wheel-side steering member that displaces according to the movement of the steering wheel to steer the front wheels and the rear wheels. A connecting mechanism that mechanically connects the input member of the rear wheel steering mechanism is provided, and if a certain amount or more of displacement occurs in both directions around the neutral position of the front wheel steering angle in the middle of this connecting mechanism, the displacement It is configured by providing a play mechanism for transmission.

Further, in the four-wheel steering system of the present invention, in the four-wheel steering system according to claim 1, the play mechanism is a component of the coupling mechanism, and the steering wheel is And a cylindrical cam that is a component of the coupling mechanism and that rotates with the rotation of the rotating shaft, and a rotating shaft that rotates based on the operation of the rotary cam, and a cylindrical cam that is provided in the circumferential direction of the cylindrical cam. And a cam groove in which inclined portions that are inclined in opposite directions in the circumferential direction are formed at both ends of a straight portion that is formed in the central portion and that is not inclined in the circumferential direction, and the input member. A rod provided inside the cylindrical cam, concentric with the cylindrical cam, and freely displaceable in the axial direction; and a component member of the connecting mechanism, which is fixed to an intermediate portion of the rod. And a cam pin that is loosely engaged with the cam groove. It is characterized by

Further, in the four-wheel steering system according to the second aspect, the play mechanism is a constituent member of the coupling mechanism, and a rotary shaft that rotates based on an operation of the steering wheel, The input member is a rod that operates the rear wheel side steering mechanism by displacing in the axial direction, a first rotating member that rotates together with the rotating shaft, and the first rotating member has a predetermined angle. With the above rotation, the first rotation member and the second rotation member that rotates together are provided, and the rod is engaged with the second rotation member to cause the second rotation member to rotate. It is characterized in that it is displaced in the axial direction as the member rotates.

[0037]

[Action]

 Like the conventional four-wheel steering system described above, the four-wheel steering system of the present invention configured as described above is operated by an idle mechanism when the steering wheel operation amount is small. Is not transmitted to the input member of the rear wheel steering mechanism. Then, when the steering wheel is turned largely, the play mechanism transmits the movement of the steering wheel to the input member of the rear wheel side steering mechanism and imparts a steering angle to the rear wheels according to the steering angle of the front wheels. ..

That is, in the case of the four-wheel steering system according to claim 1, when the operation amount of the steering wheel is small and the displacement amount of the front wheel side steering member is small, the cam pin fixed to the intermediate portion of the rod is It is located in a straight line in the center of the cam groove provided in the circumferential direction of the cylindrical cam. As a result, the rod is not displaced in the axial direction, and the steering angle is not given to the rear wheels.

When the steering wheel is largely operated to largely change the course of the vehicle, as a result, when the displacement amount of the front wheel side steering member increases, the cam pin reaches the inclined portion of the cam groove end portion and fixes the cam pin. The rod is displaced along its axial direction. As a result, a steering angle corresponding to the displacement amount of the rod is given to the rear wheel.

In the four-wheel steering system according to the second aspect, when the steering wheel operation amount is small and the front wheel side steering member displacement amount is small, the first rotating member is rotated. Regardless, the second rotary member does not rotate, and the rod engaged with the second rotary member is not displaced in the axial direction. Therefore, no steering angle is applied to the rear wheels.

When the steering wheel is largely operated to largely change the course of the vehicle, and as a result, the displacement amount of the front wheel side steering member increases, the second rotating member rotates in accordance with the rotation of the first rotating member. Rotates, the rod engaged with the second rotating member is displaced in the axial direction thereof, and the steering angle corresponding to the displacement amount of the rod is given to the rear wheel.

[0042]

【Example】

 1 to 3 show a first embodiment of the present invention corresponding to the invention described in claim 1. The present invention is not limited to the first embodiment, but in all the embodiments, the front wheel steering member for steering the front wheels and the input member of the rear wheel steering mechanism for steering the rear wheels are used as mechanical components. The structure and action of the play mechanism provided in the middle of the connecting mechanism for mechanically connecting them are the same.The other structure and action are the same as those of the conventional four-wheel steering device described above, and thus duplicated explanation will be given. Omit it.

By engaging with the rack 1 which is a front wheel side steering member that steers the front wheels 65, 65 by displacing in accordance with the movement of the steering wheel 2, the rack 1 rotates along with the displacement of the rack 1. The drive-side bevel gear 54 is fixed to the end of the rotating shaft 53. The rod 55, which is an input member of the rear wheel side steering mechanism 9 for steering the rear wheels 66, 66, is located at a position orthogonal to the rotary shaft 53 in the axial direction (left and right direction in FIG. 1). It is supported so that it can be freely displaced.

That is, the buffer mechanism 19 incorporating the compression spring 18 is provided in the middle portion, and the entire length thereof can be elastically expanded and contracted when a strong force is applied in the axial direction. It is supported by a pair of bearings 56, 56 that are provided so as to be spaced apart so as to be displaceable in the axial direction. Further, the rotation of the rod 55 is prevented by engaging a pin 57 projecting on the side surface of the intermediate portion of the rod 55 with an engaging groove 58 provided on the inner surface of the housing or the like.

On the other hand, around the intermediate portion of the rod 55, a driven-side bevel gear 59, which is concentric with the rod 55 and has a circular ring shape, is rotatably supported by a support device (not shown). By engaging the gear 59 with the drive-side bevel gear 54, together with the cylindrical cam 60 and the cam pin 61 described below, the rack 1 which is the front wheel side steering member for steering the front wheels 65, 65, and the rear wheel 66, The rod 55, which is an input member of the rear wheel steering mechanism 9 for steering the steering wheel 66, is mechanically coupled to form a coupling mechanism.

A cylindrical cam 60 that is concentric with the rod 55 is fixed to the side surface of the driven bevel gear 59, and a cam groove 62 formed in the cylindrical cam 60 is provided on the side surface of the intermediate portion of the rod 55. The fixed cam pin 61 is loosely engaged so that the rod 55 is axially displaced along with the rotation of the driven bevel gear 59.

As shown in FIG. 1 (FIG. 1 shows the shape of the cam groove 62 in an expanded state), the cam groove 62 is located at the center and inclined in the circumferential direction. From both ends of the straight line portion 63, inclined portions 64a and 64b inclined in the circumferential direction are continuous.

By engaging the cam pin 61 fixed on the side surface of the intermediate portion with the cam groove 62 having such a shape, the rod 55 can move in the axial direction (when the rotation amount of the rotation shaft 53 is small). It does not displace in the left-right direction in FIG. 1). Therefore, in this state, the steering angles are not given to the rear wheels 66, 66 regardless of the steering angles being given to the front wheels 65, 65.

When the rotation amount of the rotary shaft 53 increases with the increase of the operation amount of the steering wheel 2, the rod 55 rotates with the rotation of the rotary shaft 53. Displaces in the axial direction. That is, when the cylindrical cam 60 is rotated in the direction of arrow α in FIG. 1 by the rotating shaft 53 via the driving-side bevel gear 54 and the driven-side bevel gear 59, the rotation amount is small and the cam pin 61 is While the cam pin 61 is fixed, the rod 55, which is fixed to the cam pin 61, is not displaced in the axial direction while the cam pin 61 is positioned. However, when the rotation amount increases, the cam pin 61 slips out of the straight part 63. And reaches the inclined portion 64a, the rod 55 is further displaced rightward in FIG. Contrary to the above case, when the cylindrical cam 60 is rotated in the direction of arrow β in FIG. 1, the cam pin 61 enters the inclined portion 64b, so that the rod 55 moves leftward in FIG. Displace.

One end of the first connecting rod 17 is pivotally supported on the end of the rod 55, as in the case of the conventional four-wheel steering system described above. Then, as shown in FIG. 3, the other end portion of the first connecting rod 17 is an intermediate portion of the output side rod 16 for imparting a steering angle to the rear wheels 66, 66 with the displacement over the axial direction. Is pivoted to the department. Further, one end of the second connecting rod 21 having the intermediate portion pivotally attached to the intermediate portion of the first connecting rod 17 is connected to the end portion of the spool 23 of the hydraulic pressure switching valve 22, and the other end is connected to the stepping servomotor 45. Are respectively pivoted to nut pieces 44 screwed onto the output shaft of the.

In the four-wheel steering system of the present invention configured as described above, when the steering wheel 2 is turned a large amount, the displacement amount of the rack 1 which is the front wheel side steering member exceeds a certain amount and becomes large. Then, the cylindrical cam 60 is largely rotated via the driving-side bevel gear 54 and the driven-side bevel gear 59. As a result, the cam pin 61 fixed to the intermediate portion of the rod 55 reaches the inclined portion 64a (or 64b) of the cam groove 62 of the cylindrical cam 60, and the rod 55 is displaced in the axial direction. A sufficiently large steering angle is given to the wheels 66, 66 according to the steering angles of the front wheels 65, 65.

Further, when it is necessary to maintain the safety of the vehicle, such as when a steep steering operation is performed during high-speed traveling, the stepping servomotor 45 operates regardless of the steering angle applied to the front wheels. , The spool 23 of the hydraulic pressure switching valve 22 is displaced through the second connecting rod 21, the pressure oil is supplied to and discharged from the hydraulic cylinder 29, and the rear wheels 66, 66 are delicately steered to control the vehicle. To stabilize.

As described above, the hydraulic pressure switching valve for imparting the steering angle to the rear wheels 66, 66 based on the operation of the steering wheel 2 or directly regardless of the operation of the steering wheel 2. The movements of 22 and the first and second connecting rods 17 and 21 are almost the same as those of the conventional four-wheel steering system described above.

Next, FIG. 4 shows a second embodiment of the present invention, which also corresponds to the device described in claim 1. In the first embodiment described above, in order to transmit the movement of the rotating shaft 53 to the cylindrical cam 60, the driving-side bevel gear 54 fixed to the end of the rotating shaft 53 and the driven-side bevel gear to which the cylindrical cam 60 is fixed. In contrast to the structure in which the gear 59 and the gear 59 are meshed with each other to constitute the coupling mechanism, in the case of the present embodiment, the worm 67 fixed to the end of the rotary shaft 53 and the cylindrical cam 60 are fixed. The worm wheel 68 is meshed with each other to form a connecting mechanism. Other configurations and operations are the same as in the case of the first embodiment described above.

Next, FIGS. 5 to 6 show a third embodiment of the present invention, which corresponds to the invention described in claim 2. As in the case of the first to second embodiments, a transmission shaft 69 is rotatably provided in parallel with the rotary shaft 53 that rotates with the displacement of the rack 1 that is the front wheel side steering member. Then, the small gear 70 fixed to the end portion of the rotating shaft 53 and the large gear 71 fixed to the middle portion of the transmitting shaft 69 are meshed with each other, so that the transmitting shaft 69 has a lower speed than the rotating shaft 53. And it is designed to rotate with a large torque.

A diamond-shaped cam piece 72, which is a first rotating member, is fixed to the end of the transmission shaft 69. Around the cam piece 72, a cam ring 73, which is a second rotating member, is rotatably supported by a supporting device (not shown). A substantially oval through hole 74 is formed in the center of the cam ring 73, and the cam piece 72 is inserted into the inside center of the through hole 74.

The rod 75 (corresponding to the input side rod 10 in FIG. 11) that is an input member of the rear wheel side steering mechanism and that operates the rear wheel side steering mechanism by being displaced in the axial direction is as follows. As long as an external force does not act by the neutral position holding mechanism, which is also composed of a pair of stop rings 11 and 11 and retaining rings 12 and 12 and a compression spring 13 provided between the retaining rings 12 and 12, respectively. As long as the rotational force of the rotary shaft 53 is not transmitted to the rod 75, it is held at the neutral position in the axial direction.

A long hole 76 is formed at the end of the rod 75 in a direction perpendicular to the displacement direction of the rod 75, and a pin 77 is formed in the long hole 76 on the side surface of the cam ring 73. Are playing together. The rod 75 is displaced axially along with the rotation of the cam ring 73 by the loose engagement between the elongated hole 76 and the pin 77.

In the case of the four-wheel steering system of the present invention configured as described above, when the operation amount of the steering wheel is small and the displacement amount of the rack 1 (FIG. 11) which is the front wheel side steering member is small. The rotation angle of the rotary shaft 53 and the transmission shaft 69 is small, and the peripheral surface of the cam piece 72 fixed to the intermediate portion of the transmission shaft 69 abuts the inner peripheral surface of the through hole 74 at the center of the cam ring 73. Nor. Therefore, regardless of the rotation of the cam piece 72, which is the first rotating member, the cam ring 73, which is the second rotating member, does not rotate, and the cam ring 73 engages with the cam ring 73 due to the play between the pin 77 and the long hole 76. The combined rod 75 will not be displaced along its axial direction. Therefore, the steering angle is not given to the rear wheels.

When the steering wheel is largely operated to largely change the course of the vehicle, as a result of which the displacement amount of the rack 1 is increased and the rotation angle of the rotary shaft 53 and the transmission shaft 69 is increased, the cam piece 72 is increased. The outer circumferential surface of the cam ring 73 abuts the inner circumferential surface of the through hole 74 at the center of the cam ring 73, and the cam ring 73 rotates as the cam piece 72 rotates. As a result of the rotation of the cam ring 73 in this way, the rod 75 engaged with the cam ring 73 due to the loose engagement between the pin 77 and the long hole 76 is displaced in the axial direction thereof, and the rod 75 is attached to the rear wheel. The steering angle is given according to the amount of displacement.

Next, FIGS. 7 to 8 show a fourth embodiment of the present invention, which also corresponds to the invention described in claim 2. As in the case of the first to third embodiments, a spline portion 78 is provided at the end portion of the rotary shaft 53 that rotates with the displacement of the rack 1 that is the front wheel side steering member. In addition, a rotating cylinder 79, which is a first rotating member, is supported so as to be freely displaceable in the axial direction (vertical direction in FIG. 7) with respect to the rotating shaft 53 and to rotate together with the rotating shaft 53. There is. Around the rotary cylinder 79, a cam cylinder 80, which is a second rotary member, is rotatably supported by a support device (not shown).

A spiral recessed groove 81 whose both ends are dead ends is formed in the axially intermediate portion of the inner peripheral surface of the cam cylinder 80. An engaging pin 82 protruding from the outer peripheral surface of the rotary cylinder 79 is loosely fitted in the spiral groove 81.

The rod 75, which is an input member of the rear wheel side steering mechanism and operates the rear wheel side steering mechanism by axially displacing, is the same as in the third embodiment described above. External force does not work due to the neutral position holding mechanism composed of the pair of stop rings 11 and 11 and the retaining rings 12 and 12 and the compression spring 13 provided between the retaining rings 12 and 12. As long as possible, it is kept in the axial neutral position.

Then, also at the end portion of the rod 75, a long hole 76 is formed in a direction perpendicular to the displacement direction of the rod 75, and the long hole 76 is planted on the side surface of the cam cylinder 80. Pin 77 is loosely engaged. The rod 75 is displaced in the axial direction as the cam cylinder 80 rotates by the loose engagement between the elongated hole 76 and the pin 77.

In the case of the four-wheel steering system of the present invention configured as described above, when the operation amount of the steering wheel is small and the displacement amount of the rack 1 (FIG. 11) which is the front wheel side steering member is small. The rotation angle of the rotary shaft 53 and the rotary cylinder 79 is small, and the engaging pin 82 planted on the outer peripheral surface of the rotary cylinder 79 is displaced only inside the spiral groove 81. And the dead end of the spiral groove 81 does not abut. Therefore, the cam cylinder 80, which is the second rotary member, does not rotate regardless of the rotation of the rotary cylinder 79, which is the first rotary member, and the cam ring 73 and the cam ring 73 are loosened by the loose engagement of the pin 77 and the long hole 76. The engaged rod 75 will not be displaced over its axial direction. Therefore, the steering angle is not given to the rear wheels.

When the steering wheel is largely operated to largely change the course of the vehicle, the displacement amount of the rack 1 increases, and when the rotation angle of the rotary shaft 53 and the cam cylinder 80 increases, the cam cylinder 80 moves. The engagement pin 82 planted on the outer peripheral surface abuts the dead end of the spiral groove 81 formed on the inner peripheral surface of the cam cylinder 80, and the cam cylinder 80 is rotated by the rotation of the rotary cylinder 79. Rotate. As a result of the rotation of the cam cylinder 80 in this way, the rod 75 engaged with the cam ring 73 due to the play between the pin 77 and the elongated hole 76 is displaced in the axial direction thereof, and the rod 75 is engaged with the rear wheel. The steering angle is given according to the displacement amount of 75.

Next, FIGS. 9 to 10 show a fifth embodiment of the present invention, which also corresponds to the invention described in claim 2. As in the case of the first to fourth embodiments, at the end of the rotary shaft 53 that rotates with the displacement of the rack 1 that is the front wheel side steering member, the sun gear 83 that is the first rotary member is provided. Is fixed, and the sun gear 83 is meshed with the planetary gears 84, 84 that are the second rotating member. Further, a ring gear 85 is provided around the planetary gears 84, 84 concentrically with the sun gear 83, and the ring gear 85 and the planetary gears 84, 84 are meshed with each other.

One end (right end in FIG. 10) of the connecting rod 86 is coupled and supported to the support frame 91 supporting both planetary gears 84, 84, and the other end (left end in FIG. 10) of this connecting rod 86. In addition, one end (upper end of FIGS. 9 to 10) of the swing rod 87 is pivotally supported. An intermediate portion of the swing rod 87 is swingably supported by a support portion (not shown). The other end (lower end in FIGS. 9 to 10) of the swing rod 87 is an input member of the rear wheel side steering mechanism, and is a rod for operating the rear wheel side steering mechanism by axially displacing it. It is pivoted to 75.

Compression springs 90, 90 are respectively provided between both end surfaces of the displacement member 88 pivotally supported at the intermediate portion of the connecting rod 86, and a pair of fixed wall surfaces 89, 89 facing each other with a space therebetween. The displacement member 88 is elastically pressed toward the intermediate portion of the fixed wall surfaces 89, 89. Therefore, the support frame 91 and the swing rod 87, which are respectively coupled or pivotally supported to both ends of the connecting rod 86, are connected to the support frame 91 from the sun gear 83 via the planet gears 84, 84. Unless a strong force is applied, the state shown in FIG. 9 remains.

Further, a locking pin 92 is provided on the outer peripheral surface of the ring gear 85 so as to project, and the locking pin 92 is loosely fitted in a recess 93 formed in a fixed portion. Therefore, the ring gear 85 is rotatable within a range in which the locking pin 92 can be displaced inside the recess 93.

In the case of the four-wheel steering system of the present invention constructed as described above, when the operation amount of the steering wheel is small and the displacement amount of the rack 1 (FIG. 11) which is the front wheel side steering member is small. Has a small rotation angle of the rotary shaft 53 and the sun gear 83, and the locking pin 92 planted on the outer peripheral surface of the ring gear 85 meshed with the sun gear 83 via the planetary gears 84, 84 is The locking pin 92 does not abut against both end surfaces of the recess 93 only by being displaced inside the 93.

Therefore, when the sun gear 83, which is the first rotating member, rotates, the ring gear 85 rotates, and the planetary gears 84, 84, which are the second rotating members, only rotate on their own. It will not revolve around 83. Therefore, the rod 75 engaged with the planetary gears 84, 84 via the support frame 91, the connecting rod 86, and the swing rod 87 will not be displaced in the axial direction. As a result, no steering angle is applied to the rear wheels.

As a result of operating the steering wheel largely in order to greatly change the course of the vehicle, the displacement amount of the rack 1 increases, the rotation angles of the rotary shaft 53 and the sun gear 83 increase, and the planetary gear 84, When the rotation angle of the ring gear 85 meshed with the sun gear 83 via 84 increases, the locking pin 92 planted on the outer peripheral surface of the ring gear 85 abuts the end of the recess 93. However, the ring gear 85 does not rotate any more.

When the sun gear 83 fixed to the end of the rotary shaft 53 further rotates from this state, the planetary gears 84 and 84 revolve around the sun gear 83 while rotating on their own axis. As a result, the connecting rod 86, one end of which is connected to the support frame 91 supporting the planetary gears 84, 84, is displaced against the elastic force of the compression springs 90, 90, and the connecting rod 90 and the swinging motion. The rod 75 engaged through the rod 87 is displaced in the axial direction thereof, and the rear wheel is provided with a steering angle corresponding to the displacement amount of the rod 75.

[0075]

[Effect of the device]

 Since the four-wheel steering system of the present invention is constructed and operates as described above, a play mechanism is provided in the middle of the connecting mechanism that mechanically connects the front wheel side steering member and the rear wheel side steering mechanism input member. In this case, a relatively large force can be transmitted through this connecting mechanism, which increases the degree of freedom when designing a four-wheel steering system.

Further, since the coupling mechanism does not malfunction and the constituent members do not deform due to long-term use, a highly reliable four-wheel steering device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view showing an assembled state of the four-wheel steering device.

FIG. 4 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of an essential part showing a third embodiment of the present invention.

FIG. 6 is a view on arrow B of FIG.

FIG. 7 is a cross-sectional view of essential parts showing a fourth embodiment of the present invention.

FIG. 8 is a view on arrow C of FIG. 7.

FIG. 9 is a cross-sectional view of essential parts showing a fifth embodiment of the present invention.

FIG. 10 is a view seen from the right side of FIG. 9 with some parts omitted.

FIG. 11 is a sectional view showing the overall configuration of a conventional four-wheel steering system.

FIG. 12 is an enlarged cross-sectional view of a portion X in FIG. 11 showing a neutral state of a hydraulic switching valve incorporated in a conventional four-wheel steering system.

FIG. 13 is an enlarged cross-sectional view of the X part of FIG. 11, showing the same switched state.

FIG. 14 is a schematic diagram showing the movement of each part when steering is performed while associating front wheels and rear wheels.

FIG. 15 is a schematic diagram showing the movement of each part when the rear wheels are steered independently of the front wheels.

FIG. 16 is a diagram showing a relationship between a front wheel steering angle and a rear wheel steering angle in a conventional device.

[Explanation of sign]

 1 rack 2 steering wheel 3 pinion 4 arm piece 5 through hole 6 Bowden wire 7 cables 8a, 8b stopper 9 rear wheel side steering mechanism 10 input side rod 11 stop ring 12 retaining ring 13 compression spring 14 casing 15 inward flange portion 16 output Side rod 17 First connecting rod 18 Compression spring 19 Buffer mechanism 20 Pivoting member 21 Second connecting rod 22 Hydraulic switching valve 23 Spool 24 Cylinder 25 Pressure oil pump 26 Pressure oil supply port 27 Oil tank 28 Discharge port 29 Hydraulic cylinder 30 1st chamber 31 2nd chamber 32 1st port 33 2nd port 34 Projecting rod 35 Stop ring 36 Step part 37 Compression spring 38 Stop ring 39 Compression spring 40 Step part 41 Piston 42 First hydraulic passage 43 Second hydraulic passage 44 Nut piece 45 Stepper Servo motor 46 Male screw part 47 Controller 48 Handle shaft 49a, 49b Steering angle sensor 50 Vehicle speed sensor 51 Rotation angle sensor 52 Displacement sensor 53 Rotation shaft 54 Drive side bevel gear 55 Rod 56 Bearing 57 Pin 58 Engagement groove 59 Driven side umbrella Gear 60 Cylindrical cam 61 Cam pin 62 Cam groove 63 Straight part 64a, 64b Inclined part 65 Front wheel 66 Rear wheel 67 Worm 68 Worm wheel 69 Transmission shaft 70 Small gear 71 Large gear 72 Cam piece 73 Cam ring 74 Through hole 75 Rod 76 Long hole 77 Pin 78 Spline part 79 Rotating cylinder 80 Cam cylinder 81 Spiral groove 82 Engaging pin 83 Sun gear 84 Planetary gear 85 Ring gear 86 Connecting rod 87 Swing rod 88 Displacement member 89 Fixed wall surface 90 Compression spring 91 Support frame 92 Locking pin 93 recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Tatsuya Akita 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (72) Creator Takeshi Takema 8-5-2, Takahanadai, Maebashi, Gunma Prefecture ( 72) Creator Hiroshi Eda 1612, Komagata-cho, Maebashi, Gunma Prefecture 10 (72) Creator Nobuyasu Ando 504-1 Egi-cho, Takasaki-shi, Gunma Prefecture (72) Creator Yoshimoto Shin 1-3-15, Heiwacho, Maebashi-shi, Gunma

Claims (2)

[Scope of utility model registration request] 1. A connecting mechanism for mechanically connecting a front wheel side steering member that displaces according to the movement of a steering wheel to steer the front wheels and an input member of a rear wheel side steering mechanism for steering the rear wheels. In the four-wheel steering system, a play mechanism is provided in the middle of the connecting mechanism, the play mechanism transmitting the displacement when a predetermined amount or more of displacement occurs in both directions around the neutral position of the front wheel steering angle. The mechanism is a component of the coupling mechanism, and is a rotating shaft that rotates based on the operation of the steering wheel, and a component that is also the component of the coupling mechanism and that rotates with the rotation of the rotating shaft. The cam and the cylindrical cam are provided in the circumferential direction, and are provided at both ends of a straight portion formed in the central portion and not inclined in the circumferential direction, in opposite directions in the circumferential direction. Cam groove with inclined part And a rod which is the input member, is provided inside the cylindrical cam, is concentric with the cylindrical cam, and is freely displaceable in the axial direction, and is a constituent member of the coupling mechanism. A four-wheel steering system comprising a cam pin fixed to an intermediate portion of the cam pin and engaged with the cam groove. 2. A connecting mechanism for mechanically connecting a front wheel-side steering member that displaces according to the movement of the steering wheel to steer the front wheels and an input member of a rear-wheel-side steering mechanism for steering the rear wheels. In the four-wheel steering system, a play mechanism is provided in the middle of the connecting mechanism, the play mechanism transmitting the displacement when a predetermined amount or more of displacement occurs in both directions around the neutral position of the front wheel steering angle. The mechanism is a constituent member of the coupling mechanism, and is a rotating shaft that rotates based on an operation of the steering wheel, and the input member, and operates the rear wheel side steering mechanism by axially displacing the rotating shaft. A rod and a first rotating member that rotates together with the rotating shaft;
A second rotating member that rotates together with the first rotating member as the first rotating member rotates by a predetermined angle or more, and the rod is engaged with the second rotating member. The four-wheel steering system is characterized in that it is displaced in the axial direction in accordance with the rotation of the second rotary member.