JPH0374270A - Pear wheel steering device vehicle - Google Patents

Abstract

PURPOSE:To set the hydraulic equipment of a hydraulic system to a proper value by providing two centering springs opposite to each other, and mutually differing in the set loads of the centering springs. CONSTITUTION:A centering spring 73 is formed out of two left and right centering springs 73A and 73B. Thus, when the input loads entering left and right tie rods 21, 21 are different, resulting from the layout of a vehicle, for example, differences in length of constituting members of a rear suspension and mounting position of coil springs, the spring rates of the centering springs 73A, 73B are mutually different corresponding to the respective input loads, whereby the unbalance in input loads is absorbed and removed. Consequently, when the hydraulic assist force of a power cylinder 46 is lost, the left and right tie rode 21, 21 and the rear wheels are certainly spring-energized to the center position by the springs 73A, 73B. Further, the loads of the springs 73A, 73B can be easily set, and the energization of an excess oil pressure to the hydraulic system is not required.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention includes, for example, a hydraulically assisted power steering system in a rear steering control box, and a fail-safe mechanism that eliminates the hydraulically assisted power of the power cylinder. When the rear wheels are in neutral (2WS)
) The present invention relates to a rear wheel steering system for a vehicle such as a vehicle speed sensitive 4WS equipped with a centering spring that is fixed to a vehicle.

(Prior Art) Conventionally, as the rear wheel steering device of the above-mentioned vehicle, for example,
There is an apparatus described in JP-A-62-37283.

That is, it is equipped with a single centering spring that biases the left and right tie rods toward the center position via the rear wheel steering rod of the rear wheel steering device, and when the hydraulic assist force of the power cylinder disappears, the spring of the centering spring described above is activated. This device is configured to use force to fix the rear wheels in neutral via the rear wheel steering rod and tie rod, and fix them from 4WS to 2WS.

However, such a conventional device using a single centering spring has the following problems.

In other words, due to the layout of the car, for example, if the lengths of the left and right rear suspension arms are different, or if the coil springs are installed in different positions, there will be a difference in the input load that enters the left and right tie rods, but as mentioned above, In the case of a biasing structure using a single centering spring, only the same biasing force can be obtained in the left and right directions, so there is a problem that the biasing structure cannot be reliably biased to the neutral position during 2WS.

In addition, as mentioned above, when the input load to the tie rods is different on the left and right sides, it is difficult to set the load on the centering spring, which makes it necessary to apply extra hydraulic pressure to the hydraulic system of the power steering system. As a result, it has become difficult to set the appropriate oil pressure for the hydraulic equipment, resulting in the problem that large hydraulic equipment with high oil pressure resistance must be used.

(Object of the Invention) The present invention eliminates the unbalance of input loads from the left and right rear wheels caused by the vehicle layout, and reliably urges the left and right tie rods and the rear wheels to the center position. The purpose of the present invention is to provide a rear wheel steering device for a vehicle that can set hydraulic equipment in a hydraulic system to appropriate values.

(Structure of the Invention) The present invention provides a rear wheel steering device for a vehicle including a centering spring that biases left and right tie rods toward a center position via a rear wheel steering rod of the rear wheel steering device, the centering spring as described above. A rear wheel steering device for a vehicle is characterized in that two centering springs are provided facing each other, and the set loads of the respective centering springs are made different from each other.

(Effects of the Invention) According to the present invention, since the set loads of the two centering springs described above are made different from each other, the spring rates can be set in advance to correspond to the respective input loads input from the left and right rear wheels. This makes it possible to absorb and eliminate the input load imbalance.

As a result, when the hydraulic assist force of the power cylinder disappears, there is an effect that the left and right tie rods and the rear wheel can be reliably urged to the center position.

In addition, since it is easy to set the load of the two centering springs mentioned above, there is no need to apply extra hydraulic pressure to the hydraulic system as in the past, and it is possible to set the hydraulic equipment of the hydraulic system to an appropriate value. It has the effect of

(Example) An embodiment of the present invention will be described in detail below based on the drawings.

The drawing shows a four-wheel steering system for a vehicle, and in FIG. (omitted)) and a rear wheel steering device 5 which is interlocked and connected to the front wheel steering device 2 via a linkage shaft 3 serving as a rear steering shaft to steer left and right rear wheels 4, 4.

The above-mentioned front wheel steering device 2 is constructed as follows.

That is, a pinion 8 is connected to the lower end of a steering shaft 7 connected to a steering handle 6, and this pinion 8 is connected to a main rack 10 of a steering rod 9 extending in the vehicle width direction.
At the same time, tie rods 1 are attached to both ends of the steering rod 9.
The above-mentioned front wheels 1, 1 are connected via 1.11 and knuckle arms 12, 12, and the front wheels 1, 1 are steered about a king pin by turning the steering handle 6.

On the other hand, the steering structure for the rear wheels 4, 4 is constructed as follows.

That is, an auxiliary rack is formed on the lower surface of the auxiliary rack member 13 that is fixed to the above-mentioned steering rod 9 and extends in the vehicle width direction, and the rotation of the pinion 14 meshed with this auxiliary rack is controlled by the front universal joint 15 and the linkage shaft. 3,
The signal is configured to be transmitted to the input shaft 17 of the rear wheel steering device 5 via the rear universal joint 16.

Further, the rear wheel steering rod 18.1 of the rear wheel steering device 5 described above
9 (see Figure 2) has ball joints 20.2 at both ends.
The left and right tie rods 21, 21 are connected through the knuckle arm 22,
22 to the left and right knuckles 23.23, and the above-mentioned rear wheels 4, 4 are
is configured to be steered around a kingpin.

For example, the rear wheels 4, 4 mentioned above are steered based on the following equation.

0R=F (V)xθF Here 01 is the amount of rear wheel steering F (V) is the steering ratio that changes with vehicle speed (V) θ is the amount of steering of the front wheels.

Further, the aforementioned rear wheels 4, 4 are suspended by a rear suspension 26 including a lower arm 24 and a lateral link 25, as shown in the figure.

By the way, the above-mentioned rear wheel steering device 5 is constructed as shown in FIG. 2.

That is, this rear wheel steering device 5 includes a housing 27 as a rear steering control box, a left rear wheel steering rod 18 having oil passages 28 and 29 formed therein in the axial direction, and oil passages 30 and 31 formed in the axial direction. The right rear wheel steering rod 19 formed by drilling is connected to the left and right rear wheel steering rods 18, 1.9 in a straight line, and a plurality of oil passages 32, 33, 34.
35; and a control pulp 40 as a hydraulic drive means, which is incorporated in the sleeve 36 and includes a control rod 37, a spool 38 and a centering spring 39, which are parallel to the left and right rear wheel steering rods 18, 19. , a power cylinder 46 formed between the rear wheel steering rod 18 on the left side and the housing 27, and partitioning a hydraulic chamber between the rod covers 41 and 42 on both sides into a left chamber 44 and a right chamber 45 by a power piston 43; Between the above-mentioned rod cover 41 and the lock nut 47 screwed onto the left end of the housing 27, the metal tube 48 fitted into the above-mentioned housing 27 and the driving bevel gear 50 are fitted onto the rotating shaft 49, and the steering ratio θ is /θ, and the above-mentioned driving bevel gear 50 is interlocked via a driven bevel gear 52, a rotating shaft 53, and a worm 54, and the rotating shaft 5
A control yoke 56 that swings about 5 and has a worm wheel portion at its tip that meshes with the above-mentioned worm 54, and is connected via a pin 58 to a holder 57 that is swing-operated by the above-mentioned control yoke 56. a swing arm 59; a large-diameter bevel gear 62 that is attached to the above-mentioned housing 27 via a holder 60 and a pin 61 and rotates in response to the amount of steering of the above-mentioned steering wheel 6; and a rear end of the above-mentioned input shaft 17. a small-diameter bevel gear 63 that is fitted into the large-diameter bevel gear 62 and always meshes with the large-diameter bevel gear 62; A connecting rod 67 attached through each ball joint 64°65.66, and a phase control mechanism 68 including the above-mentioned elements, that is, the step motor 51, the control yoke 56, the swing arm 59, the bevel gear 62, and the connecting rod 67. , the oil panel 69 attached to the housing 27 described above, and the pump boat P and the tank boat T, which are arranged at the protruding part of the right rear wheel steering rod 19 from the housing 27.
A block 70 having a block 70 is provided.

Here, in the above-mentioned phase control mechanism 68, the step motor 51 controls each element 49, 50, 52, 53 in accordance with the vehicle speed.
．． 54 to rotate a control yoke 56, which controls each element 57, 58, 59 .
64, 67, 65 to move the control rod 37 in the left and right direction, while the bevel gear 62 moves the steering handle 6
The control rod 37 is rotated in response to the amount of steering, and the control rod 37 is moved in the left-right direction via each element 66, 67, 65. The total movement of the control rod 37 due to the rotation is the amount of operation of the control rod 37 in the left-right direction described above.

When the control rod 37 moves to the left in FIG. 2 by the phase control mechanism 68 described above, the spool 38 slides to the left following the movement of the control rod 37, and the ring groove 71 on the outer periphery of the spool 38 causes the spool 38 to slide to the left. Since the oil passages 32 and 33 are connected, P
Hydraulic oil supplied from boat P is applied to each element 30, 32, 7.
1.33 Right chamber 45 of power cylinder 46 via 29
moves the rear wheel steering rod 18.19 to the left side and steers the rear wheels 4, 4 to the right via the left and right tie rods 21.21, while the hydraulic fluid in the left chamber 44 of the power cylinder 46 is The oil is returned from each of the oil passages 28 and 34 and the ring groove 72 through the spool 38 to the oil passage 35, and further from the oil passage 35 through the oil passage 31 and the tank port T to the tank.

Conversely, when the control rod 37 moves to the right in FIG.
Since the oil passages 32 and 34 are communicated by the ring groove 72 on the outer periphery, the hydraulic oil supplied from the P boat P is connected to each element 30, 32.
, 72, 34° 28 into the left chamber 44 of the power cylinder 46, moving the rear wheel steering rods 18, 19 to the right side, and moving the rear wheel steering rods 18, 19 to the right side through the left and right tie rods 21, 21 to the rear wheel 4.
4 to the left, while the right chamber 45 of the power cylinder 46
The hydraulic oil inside is returned to the tank via each element 29.33, 71°35.31 and tank boat T.

By the way, the left and right tie rods 21 are connected to the metal tube 48 through the rear wheel steering rods 18 and 19.
．． A centering spring 73 is provided that biases 21 toward the center position.

This centering spring 73 is connected to the power cylinder 46
This is a fail-safe mechanism that fixes the rear wheel 4.4 in neutral when the hydraulic assist force is lost, changing the speed from 4WS to 2WS.

The above-mentioned centering spring 73 consists of two springs, a left centering spring 73A and a right centering spring 73B, as shown in FIG. They are arranged opposite to each other on the wheel steering rod 18.

That is, while the annular stopper 48a as a spring seat is integrally formed on a predetermined portion of the inner wall of the metal tube 48,
The rear wheel steering rod 1 described above is connected to the nut 74 screwed onto the left end threaded portion 18a of the rear wheel steering rod 18 and the locking ring 75 fitted to the left side of the rod 18.
8, the left centering spring 73A is stretched between the left slider 76 and the annular stopper 48a, and the right centering spring 73B is inserted between the right slider 77 and the annular stopper 48a. 48a.

And each of these left and right centering springs 73A
, 73B, so-called spring rates are set to different values corresponding to the respective input loads input from the left and right rear wheels 4, 4.

However, each of the above-mentioned centering springs 73A.

The spring rate of 73B is the same as that of the control valve 40 described above.
It goes without saying that the spring rate should be set sufficiently large relative to the spring rate of the inner setan ring spring 39.

In addition, in the figure, 78 is a rubber boot.

Since the centering spring 73 is composed of two pieces, the left centering spring 73A and the right centering spring 73B, it is possible to adjust the vehicle layout, such as the length of the components of the rear suspension 26 and 26 shown in FIG. The installation position is different,
If the input loads entering the left and right tie rods 21, 21 are different due to this, by making the spring rates of the centering springs 73A, 73B different from each other in accordance with the respective input loads, the input load can be adjusted. can absorb and eliminate imbalances.

As a result, when the hydraulic assist force of the power cylinder 46 disappears, the left and right tie rods 21, 21 and the rear wheel 4
, 4 to each of the above-mentioned centering springs 73A, 73b.
This has the effect of ensuring that the spring is biased to the central position.

3 4 In addition, the two centering springs 73A mentioned above,
73B load setting becomes easy, there is no need to apply extra hydraulic pressure to the hydraulic system (specifically, the hydraulic path from the vane pump to the tank) as in the past, and various hydraulic equipment used in the hydraulic system can be properly adjusted. It has an effect that can be set to a certain value.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a schematic plan view showing a four-wheel steering device for a vehicle, FIG. 2 is a cross-sectional view showing the internal structure of a rear wheel steering device, and FIG.
It is an enlarged view of the main part of the figure. 5... Rear wheel steering device 18.19... Rear wheel steering rod 21... Tie rod

Claims (1)

[Claims] (1) Rear wheel steering device A rear wheel steering device for a vehicle equipped with a centering spring that biases left and right tie rods toward the center via a rear wheel steering rod, the two centering springs facing each other. A rear wheel steering device for a vehicle, wherein the centering springs have different set loads.