JPH0466373A - Four-wheel steering gear - Google Patents

Abstract

PURPOSE:To improve safety by providing a maximum steering quantity regulating device for mechanically restricting the maximum moving quantity of a rear wheel steering rod so as to adjust the maximum moving quantity of the rear wheel steering rod restricted mechanically according to the front wheel steering oil pressure. CONSTITUTION:In a four-wheel steering gear provided with a front wheel steering gear 1 including a hydraulic cylinder integrally formed at a part of a front housing 5 and a rear wheel steering gear 2 for controlling the steering quantity of rear wheels 28 by controlling a motor 42, the rear wheel steering gear 2 is provided with a maxi mum steering quantity regulating device 50 for mechanically restricting the maximum moving quantity of a rack rod 21. This regulating device 50 is formed by fitting a variable regulating member 58 of rectangular parallelepipedic shape short in the longitu dinal length slidably into a recessed part 53, and initial regulation is performed by the engagement among a V-shape regulating groove 63 provided on the front lower face of the regulating member, the rack rod 21 and a fixed moving quantity regulating pin 64. The regulating member 58 moves forward/backward according to the front wheel steering oil pressure fed into a cylinder hole 54 to adjust the lateral maximum moving quantity of the rack rod 21.

Description

[Detailed description of the invention] Industrial applications do.

Conventional technology A four-wheel steering system for an automobile is equipped with a front wheel steering system and a rear wheel steering system. It is known that the rear wheels are steered by
136876).

In such a rear wheel steering device, the relative steering direction of the rear wheels (the steering direction of the rear wheels with respect to the steering direction of the front wheels) and the maximum allowable steering amount are controlled depending on the vehicle speed.

FIG. 8 shows an example of the relationship between the vehicle speed, the relative steering direction of the rear wheels, and the amount of steering (steering angle).

In the figure, the horizontal axis represents vehicle speed (km/h), and the vertical axis represents steering amount (degrees). A steering amount of 0 means a neutral state, a + steering amount means the steering direction of the rear wheels is the same as the steering direction of the front wheels (in-phase steering), and a − steering amount means the steering direction of the rear wheels is opposite to the steering direction of the front wheels. Each represents steering with an opposite phase. The solid curve (^) represents the maximum allowable steering amount at each vehicle speed. In this case, when the vehicle speed is low,
When anti-phase steering is performed, the maximum allowable steering amount increases as the vehicle speed decreases, and when the vehicle speed is high,
Steering is performed in the same phase, and as the vehicle speed increases, the maximum allowable steering amount increases once and then decreases. Then, within the range of the maximum allowable steering amount according to the vehicle speed, that is, the song! ! Within the range surrounded by (A) and the horizontal axis, the amount of steering of the rear wheels is controlled in accordance with the amount of steering of the front wheels. In addition, in either case of anti-phase steering or same-phase steering, the actual steering direction of the rear wheels changes depending on the steering direction of the front wheels. This represents the maximum allowable steering amount in each direction.

In the rear wheel steering device as described above, the amount of movement of the rear wheel steering rod is mechanically (structurally) limited, and within this mechanical maximum amount of movement, the amount of movement of the rear wheel steering rod as described above is limited. Control is carried out. In Figure 8, two chain lines parallel to the horizontal axis (B) (C
) represents the steering amount when the rear wheel steering rod moves to the left and right mechanical limit ends, and this steering amount is naturally slightly larger than the maximum value of the maximum allowable steering amount of curve (A).

Mechanically, the rear wheel steering rod can be moved by the maximum mechanical movement amount regardless of the vehicle speed, and therefore the rear wheels can also be steered between the straight line (B) and the straight line (C).

When the entire rear wheel steering system is operating normally, the amount of rear wheel steering does not leave the range surrounded by the curve (A) and the horizontal axis in FIG. 8. However, if, for example, the electric motor goes out of control, the rear wheels mechanically move in two straight lines (B) (
Since the vehicle may be steered between C), the amount of steering of the rear wheels may greatly exceed the maximum allowable amount of steering for each vehicle speed, which is particularly dangerous when driving at high speeds.

An object of the present invention is to provide a safe rear wheel steering device that solves the above problems.

Means for Solving the Problems A four-wheel steering device according to the present invention includes a front wheel steering device that steers the front wheels using hydraulic pressure according to the rotation of a steering wheel and its rotational torque, and a rear wheel steering device that uses an electric motor to steer the front wheels according to the amount of steering of the front wheels. In a four-wheel steering system equipped with a rear wheel steering device that steers the rear wheels by moving a rod, the rear wheel steering device is provided with a mechanism that mechanically limits the maximum amount of movement of the rear wheel steering rod and that this maximum amount of movement is limited. A maximum steering amount regulating device having a variable regulating member that can adjust the amount of movement is provided, and as the steering hydraulic pressure of the front wheels decreases, the maximum amount of movement of the rear wheel steering rod that is mechanically limited by the variable regulating member decreases. The maximum steering amount regulating device is connected to the hydraulic circuit of the front wheel steering device so that the maximum steering amount regulating device is connected to the hydraulic circuit of the front wheel steering device.

Operation The front wheel steering hydraulic pressure of the front wheel steering device is small when the steering wheel is not operated (rotated) or when the steering wheel is operated at high speed, and high when the steering wheel is operated when the vehicle is stopped or driving at low speed.

When the steering wheel is not operated or when the steering wheel is operated at high speed, the front wheel steering hydraulic pressure is small, so the maximum movement of the rear wheel steering rod, which is mechanically limited by the variable restriction member, is reduced, and the electric motor is Even if I run out of control,
The rear wheels are never steered far beyond the maximum allowable steering amount.

In addition, when the steering wheel is operated when stopped or driving at low speed, the front wheel steering hydraulic pressure is large, so the maximum movement of the rear wheel steering rod, which is mechanically limited by the variable restriction member, increases, causing the rear wheels to be steered significantly. becomes possible.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 shows a schematic configuration of a four-wheel steering system for an automobile, which is equipped with a front wheel steering system (1) and a rear wheel steering system (2), and Figure 2 shows a small mechanical part of the rear wheel steering system (2). .

The front wheel steering device (1) is, for example, a known rack and pinion type in which rotation of a steering wheel (3) is transmitted to a front rack rod (front wheel steering rod) (4) via a pinion (not shown). It is equipped with a hydraulic power steering mechanism. The rack rod (4) extends in the left-right direction and is supported by the front housing (5) so as to be movable in the left-right direction (axial direction). The housing (5) is fixed to the vehicle body. Front wheels (8) are connected to both ends of the rack rod (4) via tie rods (6) and knuckle arms (7).
are connected. By rotating the handle (3), the rack rod (4) moves in the left-right direction, and the front wheels (8) are steered.

Hydraulic power steering mechanisms are also well known, and although detailed illustrations are omitted, they are configured as follows, for example. A hydraulic cylinder is integrally formed in a part of the front housing (5), and a piston is provided in the middle part of the front rack rod (4) to slide on the inner peripheral surface of this cylinder. on the other hand,
The input shaft connected to the handle (3) and the output shaft connected to the pinion are connected via a shaft, and a rotary control valve (9) is connected between them.
), and the two oil chambers of the cylinder and the hydraulic pump (10) are connected via this rotary valve (9). The front wheels (8) are then steered by the rotation of the /1 steering wheel (3) and the hydraulic pressure corresponding to its rotational torque.

The front wheel steering system (2) also includes a front wheel steering system (2) that controls the front wheels (8
) is provided with a front wheel steering W detection device (11) for detecting the amount of steering.

Like the front wheel steering device (1), the rear wheel steering device (2) includes a rear rack rod (rear wheel steering rod) (21) supported by a rear housing (20). Housing (20)
is formed into a cylindrical shape extending in the left-right direction by a housing main body (22) and a housing tube (23) fitted on the right side of the housing main body (22).

The rack rod (21) is inserted into the housing (20) and extends in the left-right direction, and is supported by a known bushing (24) and a support yoke (25) (see Fig. 3) inside the housing (20). It is possible to move to. Both ends of the rack rod (21) are connected to tie rods (26).
and a rear wheel (28) via a knuckle arm (27). Then, by moving the rack rod (21) in the left-right direction, the rear wheels (28) are steered.

An inward flange member (
29) is fixed, and an inward flange (30) is formed at a portion farther to the right. Housing body (22
) Rack rod (21) corresponding to the inward facing collar member (29)
An outward facing flange member (31) is fixed to the outer periphery of the portion near the left end. The inward flange of the housing body (22) (
Attach a retaining ring (3) to the outer periphery of the rack rod (21) corresponding to
2) is fixed, and the stopper ring (33
) is fitted. In the part between the inward facing flange member (29) and the inward facing flange part (30) of the housing body (22), there is a left slide on the outer periphery of the rack rod (21) immediately to the right of the outward facing flange member (31). The sliding ring (34) has a right sliding ring (34) located immediately to the left of the stopper ring (33).
5) are fitted so that they can freely slide left and right. Left and right sliding rings (34) (35) on the outer periphery of the rack rod (21)
), a centering spring consisting of a compression coil spring (
36) is fitted. A cylindrical left movement regulating member (37) extending to the right on the outer periphery of the left sliding ring (34).
is fixed, and a right side movement amount regulating member (38) extending to the left side is also fixed to the outer periphery of the right side sliding ring (35). If no left-right force is acting on the rack rod (21),
The centering spring (36) allows the left and right sliding rings (
34) (35) are urged away from each other, the left sliding ring (34) is urged against the outward facing collar member' (31) of the rack rod (21), and the right sliding ring (35) is urged away from the rack rod (21).
1) are pressed against the stopper rings (33). Note that at this time, the stopper ring (33) is prevented from moving to the right by the retaining ring (32). Also, at this time, the left sliding ring (34) is attached to the inward flange member (29) of the housing body (22), and the right sliding ring (35) is attached to the inward flange (30) of the housing body (22). They are in pressure contact with each other, and the rack rod (21) is held in a neutral state.

When the rack rod (21) is in a neutral state, the right end of the left regulating member 37) and the left end of the right regulating member (38) are slightly separated from each other in the left and right directions. When a horizontal force larger than the centering spring (36) is applied to the rack rod (21), the rack rod (21) can move left and right by the distance of the left and right regulating members (37) (3g). . When a leftward force acts on the rack rod (21), the outward facing collar member (
31) is separated from the left sliding ring (34) and moves to the left of the rack rod (21). When the rack rod (2'') moves to the left, the retaining ring (32) and stopper ring (33)
, the right sliding ring (35) and the right regulating member (38) also move to the left, and when the left end of the right regulating member (3B) hits the right end of the stationary left regulating member (37), the rack The rod (21) is moved or stopped. Conversely, if a rightward force is applied to the rack rod (2I), the stopper ring (
33) is separated from the right sliding ring (35) and moves to the right of the rack rod (21). When the rack rod (21) moves to the right, it is pushed by the outward facing collar member (31), and the left sliding ring (34) and the left regulating member (37) also move to the right, causing the left regulating member (37) to move to the right. When the right end hits the left end of the stationary right side regulating member (38), the rack rod (21) stops moving. In this way, the rack rod (2 pieces) mechanically has the right and left regulating members (37) (3) in the neutral state.
Move left and right by twice the distance in 8).

Hereinafter, this amount of movement will be referred to as the mechanical maximum amount of movement of the rack rod (21), and the corresponding amount of steering (steering angle) of the rear wheels (2B) will be referred to as the maximum amount of mechanical steering.

A rack rod drive device (39) for moving the rack rod (21) in the left-right direction and a rear wheel (28) are attached to the housing body (22).
) for detecting the steering amount of the first steering amount detection device (40
) and a second steering amount detection device (41).

The rack rod drive device (39) includes an electric motor (42) as a drive source, a clutch (43), and a speed reduction device (44).
It is equipped with As shown in Figure 3, the housing body (
22) A pinion shaft (45) extending in the front-back direction is rotatably supported within the pinion shaft (45), and a rack (47) is formed on the pinion shaft (45) or on the rack rod (21). They are engaged. And the motor (42
) is transmitted to the pinion (46) via the clutch (43) and reduction gear (44), and the rack rod (21) that meshes with the pinion (46) moves left and right.

The first steering amount detection device (40) includes, for example, a potentiometer, and detects the amount of steering of the rear wheels (28) by detecting rotation of the pinion shaft (45).

The second steering amount detection device (41) converts the movement of the rack rod (21) in the left and right direction into rotation by an appropriate means, and detects the amount of steering of the rear wheels (28) by detecting the second rotation. .

The rear wheel steering device (2) includes a vehicle speed sensor (48), a front wheel steering 2 detection device (]1), and a first and second steering amount detection device (
40) Depending on the output of (41), the rack rod drive device (3
9) is provided with a control device (49) that controls the motor (42) and clutch (43). The control device (49) is configured by a computer.

The control device (49) controls the amount of movement of the rear rack rod (21), that is, the amount of steering of the rear wheels (28), by controlling the amount of rotation of the motor (42) according to the vehicle speed and the amount of steering of the front wheels (8). Control. That is, from the vehicle speed detected by the vehicle speed sensor (48), the steering direction and maximum allowable steering amount of the rear wheels (28) at that vehicle speed are known based on the relationship shown in FIG. 8, and the range of this maximum allowable steering amount is determined. The motor (42) is controlled according to the amount of steering of the front wheels (8). At this time, the steering amount of the rear wheels (28) is detected by the first steering amount detection device (40) and fed back to the control device (49). In addition, the control device (49) constantly compares the output of the first steering amount detection device (40) and the output of the second steering amount detection device (41), and when a difference of more than a predetermined amount occurs between them, , it is determined that an abnormality has occurred in the detection of the amount of steering of the rear wheels (28), and the clutch (43) is turned off and the motor (42) is turned off to prevent the rear wheels (28) from being steered. Make it.

The rear wheel steering device (2) includes a maximum steering amount regulating device (50) that mechanically limits the maximum amount of movement of the rack rod (21) within the range of the mechanical maximum amount of movement.

An example of the configuration of the maximum steering limit device (50) is shown in FIGS. 4-7.

A block part (51) in the shape of a rectangular parallelepiped that is long in the front-rear direction is integrally formed on the upper wall of the housing body (22), and a cylinder part (52) in the shape of a column extending forward is integrally formed on the front surface of this block part (51). It is formed.

A square-shaped guide recess (53) is formed on the upper surface of the block portion (51).
) is formed, and a cylinder hole (54) is formed in the front part of the block part (51) and the cylinder part (52), which reaches from the fourth part (58) to the front end surface of the cylinder part (52).

Elongated holes (55) (5B) are formed in the left-right direction in the earthen wall of the housing body (22) at the bottom of the fourth part (53) and the corresponding tube (23).

The upper opening of the recess (53) is closed by a lid (57), and inside the recess (53) is a rectangular parallelepiped-shaped variable regulating member (58) that is shorter in longitudinal length than the fourth part (53) and is slidable back and forth. A plunger (59) extending in the front-rear direction is fixed to the front end surface of the regulating member (58) in a forward-protruding manner, and the plunger (59) is slid into the cylinder hole (54) tightly from the rear and back and forth. I am addicted to it freely. Cylinder hole (5
4) is attached with a seal (60) that seals between it and the plunger (59). A spring hole (61) is formed in the rear end surface of the regulating member (58), and a compression coil spring (61) is provided between the hole (61) and the rear wall of the recess (53) to bias the regulating member (58) forward. 62) is installed.

A regulating groove (63) extending rearward from the front end is formed on the lower front surface of the regulating member (58). This miso (63)
It forms a V-shape starting from the bottom, and its left and right width gradually decreases towards the back. A movement regulating bin (64) is fixed to the rack rod (21). This bottle (64) protrudes upward from the upper outer periphery of the rack bar 21) and enters the recess (53) through the tube (23) and the elongated holes (56) (55) of the housing body (22). , so as to fit into the miso (63) of the regulating member (58).

A taper threaded portion (65) for piping is formed at the front end of the cylinder hole (54), and the hydraulic power of the hydraulic power steering mechanism of the front wheel steering device (1) is connected through this portion or appropriate piping. It is connected to a suitable part of the circuit where the front wheel steering hydraulic pressure acts, for example, to the discharge side of a hydraulic pump (10).

When the hydraulic pressure supplied to the cylinder hole (54) is small, the regulating member (58) is activated by the spring (
C2), it is moved to the front end position where it contacts the front wall of the recess (53). At this time, the bottle (64) is in the groove (6
3) fits into the rear end, and the groove width of this part is the same as that of the bottle (64
) is only slightly thicker than the diameter of the bottle (6
4) can hardly be moved left or right, and the rack rod (21) can hardly be moved left or right. As the hydraulic pressure supplied to the cylinder hole (54) increases, the force pushing the plunger (59) backward increases, and as shown in FIG. 7, the regulating member (58) resists the force of the spring (82). and move backward from the front end position. At this time, the bottle (64) is the groove (63)
bottle (64) and rack rod (21).
) can now move left or right by two distances determined by the width of the groove in that area. The amount of rearward movement of the regulating member (58) corresponds to the oil pressure, and as the oil pressure increases, the amount of movement also increases. As the amount of rearward movement of the regulating member (5g) increases, the width of the portion where the bin (64) fits increases, and the maximum width of the bin (64) and rack rod (21) in the left and right direction increases. The amount of movement also increases.

When the steering wheel (3) is not operated, the hydraulic pressure for steering the front wheels (8) by the hydraulic power steering mechanism of the front wheel steering device (1) is very small, and the hydraulic pressure supplied to the regulating device (50) is also very small. small. Therefore, the regulating member (58) is located at or near the front end position, and the maximum amount of movement of the rear rack rod (21) that is mechanically restricted by the miso (63) is very small.

Therefore, even if the motor (42) starts running, the rear wheels (28) are hardly ever steered.

When the steering wheel (3) is operated when stopped or driving at low speed, the steering hydraulic pressure of the front wheels (8) is large and the regulating device (50)
The hydraulic pressure supplied to the is also large. For this reason, the regulating member (58
) moves rearward, and the maximum movement of the rear rack rod (2]), which is mechanically limited by the miso (63), increases.

Therefore, it is possible to largely steer the rear wheels (28).

When the vehicle speed increases, the steering hydraulic pressure of the front wheels (8) when operating the steering wheel (3) decreases, and the regulating device (50)
The hydraulic pressure supplied to the engine also decreases. Therefore, as the vehicle speed increases, the restriction member (58) moves forward, and the rear rack rod (2) is mechanically restricted by the restriction member (63).
1) The maximum movement amount becomes smaller. Therefore, the motor (
42) Even if the vehicle runs out of control, the rear wheels (28) will not be steered far beyond the maximum allowable steering amount.

Effects of the Invention According to the four-wheel steering system of the present invention, as described above, when driving at high speed, the maximum movement of the rear wheel steering rod, which is mechanically limited by the variable regulating member, becomes smaller, and the electric motor may run out of control. This can prevent the rear wheels from being steered far beyond the maximum allowable steering amount.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a four-wheel steering system for an automobile showing an embodiment of the present invention, Fig. 2 is a partially cutaway plan view showing the mechanical part of the rear wheel steering system, and Fig. 3 is a schematic diagram of a four-wheel steering system for an automobile showing an embodiment of the present invention. Figure 4 is an enlarged cross-sectional view of line IV-IV in Figure 2, Figure 5 is a cross-sectional view of line ■-V in Figure 4, Figure 6 is a cross-sectional view of Figure 4 Vl-VT
A cross-sectional view of the line, FIG. 7 is a drawing corresponding to FIG. 6 showing a state different from that of FIG. 6, and FIG. 8 is a graph showing the relationship between vehicle speed and relative steering amount of the rear wheels. (1)...Front wheel steering device, (2)...Rear wheel steering device, (3)...Handle, (8)...Front wheel, (21)
...Rear rack rod (rear wheel steering rod), (28)...
Rear wheel, (50)...Rear wheel steering amount regulating device, (58)...
...Variable regulation member. Above Figure 3 Figure 1 Figure 5

Claims (1)

[Claims] A front wheel steering device that steers the front wheels using oil pressure according to the rotation of a handle and its rotational torque, and a front wheel steering device that steers the rear wheels by moving a rear wheel steering rod using an electric motor according to the amount of steering of the front wheels. A four-wheel steering device equipped with a rear wheel steering device, wherein the rear wheel steering device has a variable regulating member that mechanically limits the maximum amount of movement of the rear wheel steering rod and can adjust this maximum amount of movement. A steering amount regulating device is provided, and the maximum steering amount regulating device controls the front wheel steering device so that as the front wheel steering hydraulic pressure becomes smaller, the maximum amount of movement of the rear wheel steering rod that is mechanically limited by the variable regulating member becomes smaller. A four-wheel steering device characterized by being connected to a hydraulic circuit.