JPS60213574A - Vehicle steering device - Google Patents

Abstract

PURPOSE:To enhance the follow-up function of rear wheels, by reducing the flow rate of hydraulic oil fed into a rear wheel power cylinder in accordance with decreases in the flow rate of hydraulic oil fed into a front wheel power cylinder. CONSTITUTION:In a front wheel side hydraulic oil feed passage 68 there is disposed a main flow control valve 82 which reduces the flow rate of hydraulic oil fed into a power cylinder as the vehicle speed increases, to adjust the steering force of a steering wheel in response to the vehicle speed. Further, in a rear wheel side hydraulic oil feed passage 76 there is disposed a compensating flow rate control valve 86 which is adapted to reduce the flow rate of hydraulic oil fed into a rear power cylinder 26 in accordance with decreases in the flow rate of the main flow control valve 82. The compensating amount of this control valve 86 is set in proportion to the flow rate controlled by the main flow control valve 82. With this arrangement the front wheels and the rear wheels are synchronized together with the use of a simple mechanism, thereby assisting force may be obtained by hydraulic pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a vehicle steering system, and more particularly to an improvement in a power steering system for a vehicle that simultaneously steers not only the front wheels but also the rear wheels.

[Background of the invention]

Conventionally, power steering mechanisms have been adopted in steering devices from the perspective of reducing the steering force of vehicles, and front and rear wheel steering devices have been proposed that completely steer not only the front wheels but also the rear wheels (Japanese Patent Application Laid-Open No. 1983-1999). 112875).

By the way, when steering both the front and rear wheels, as disclosed in the above publication, if the front and rear wheels are synchronized via a link mechanism etc., mechanical errors cannot be avoided, so accurate steering control is not possible. It becomes possible. Therefore, in general, a control system is adopted in which independent hydraulic systems are installed separately for the front and rear wheels of the power cylinder assembly, and the five front and rear wheels are synchronized.

However, since the hydraulic control system for steering must be completely independent and the two systems must be related to each other for steering, the device configuration becomes complicated and a separate control means is required for synchronization. .

[Purpose of the invention]

The present invention has focused on the above-mentioned problems, and an object of the present invention is to provide a vehicle steering system which has a simple structure for steering front and rear wheels and can ensure stable steering performance.

[Summary of the invention]

In order to achieve all of the above objects, "a vehicle steering system according to the present invention first includes a control valve arranged in parallel on the binion shaft of a rack-and-binion type steering mechanism, and connects a power cylinder for steering the front wheels and a power cylinder for steering the rear wheels. This is based on the knowledge that if used to switch the oil supply path of the power cylinder of the engine, the front and rear wheel steering can be fully synchronized.In other words, when a rack-and-binion type steering mechanism requires a large steering force, By providing a shifting displacement in the binion that meshes with the rack, and taking this shifting displacement as the operating displacement of the control valve for all front and rear wheel power cylinders, it is possible to operate both the front and rear cylinders in synchronization with all handle operations. In this case, if applied as is to a vehicle speed-sensitive power steering mechanism that controls the total flow of oil supplied to the front power cylinders to adjust the steering force of the steering wheel according to the vehicle speed and steering angle, the amount of oil supplied to the rear power cylinders will be reduced. As the vehicle speed increases, the flow rate becomes larger than the specified flow rate, which becomes sensitive and dangerous.This is because Binyon Sharad is transferred as the steering wheel is operated. However, on the front wheel side, flow control is performed appropriately in response to speed and steering angle, so that the amount of supply is felt and the assist force of the power cylinder is reduced, whereas on the rear wheel side, control is performed in response to the front wheel side. This is because even though the flow rate is different, the same amount is supplied according to the opening degree of the synchronized control valve, resulting in excessive steering of the rear wheels compared to the front wheels, resulting in imbalance. From this point of view, in order to keep the supply flow rate of □ to the rear wheel power cylinder at least constant or decrease it depending on the amount of flow reduction on the front wheel side,
A correction flow control valve was installed in the oil supply path to the rear power cylinder.

For this reason, even if the flow rate supplied to the front wheel power cylinders is gradually increased in response to vehicle speed, the flow rate passing through the rear wheel control valve operated by the same pinion shaft will be lower than that of the front wheels. Since it can be corrected so as to be reduced in accordance with the side supply flow rate, it is possible to optimize the steering performance of the front and rear wheels to prevent imbalance.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a vehicle steering system according to an embodiment, with a handle 1
The front wheels 18' (1) are steered by a pinion shaft 12 that is rotated by 0 and a rack 16 (see Fig. 2) linked to a tie rod 14, and the steering force is reduced. For front wheel 18 tie rod 1
4 and power cylinders 24.26 are connected to the tie rods 22 of the rear wheels 20, respectively, to form a single power cylinder 24.26.
A control valve mechanism 28 is provided on the front packing pinion shaft 12 in order to control oil passage switching.

The control valve mechanism 28 is as shown in the second and third teeth.

It consists of two identical control valves 30.3OA arranged in parallel on the pinion shaft 12. Both valves 30.3
Since the OAs are the same, one valve 30 will be described.

The mass and pinion shaft 12 is supported within a gear box 34 by a bearing 32, with its meshing portion with the rack 16 sandwiched therebetween. This shaft 12 is supported in a box 34 in a princely manner so that it can be moved left and right on the rack 16 when the rack 16 is experiencing movement resistance due to wheel ground resistance.

A swing lever 36 for valve operation is attached to a fixed position of the protrusion of the pinion shaft 12 from the gear box 34. The swing lever 36 is connected to the pinion shaft 1
2, and a support pin 40 and a drive pin 42 that protrude at symmetrical positions along the diameter direction of the ring part 38.

At the mounting position of the swing lever 36, the gear box 34 is connected to a valve block main body 44, which is a casing assembly of the control valve 30.
A valve spool 48 is fitted into a sleeve portion 46 having a vc shape in a direction perpendicular to the pinion shaft 12. The swing lever 36 has its drive pin 42 inserted into a pin hole 50Vc formed in the valve spool 48, and the support pin 40 on the opposite side inserted into a fulcrum hole 5 formed in the valve block body 44.
2 and serves as a rotational fulcrum.゛Thus, when the pinion shaft 12 rolls, the swing lever 36 swings around the support pin 40, and the drive pin 42 at the tip
This allows the valve spool 48 to reciprocate in the axial direction.

The valve spool 48 has an annular groove 54.5 forming a pressure oil passage with the Vc1 sleeve portion 46 as shown in FIG.
6 is provided in the sleeve portions 4 and 6, and the annular groove 5 is provided in the sleeve portions 4 and 6.
4.56, a pump port 58, cylinder ports 60, 62, and a tank port 64 are formed which selectively communicate with the entire hydraulic chamber of the power cylinder 24 (26) on the pump side or the tank side. When the valve spool 48 moves from the neutral position in the figure to the right or left, the direction of pressure oil supply to the power cylinders 24+26) via the valve block body 44 changes depending on the direction of movement.

The configuration of the control valve 30 described above is the same for the other adjacent control valve 30A, so the symbol Ay is attached to the same number and the explanation is omitted.

And one control pulp 30 all front wheel power cylinder 2
The other control valve 3oAv is arranged in the oil supply and discharge path to the rear wheel power cylinder 26.

The oil supply/drainage path on the front wheel side is a supply path 68 that runs from the hydraulic source pump 66 to the power cylinder 24 via the control valve 30. ! −
, a discharge path 72 that similarly runs from the power cylinder 24 through a control valve 30 to a tank 70, and a pump 6.
6 and tank 70 are connected to form a closed loop as a whole. The same goes for the oil supply and drainage path on the rear wheel side, which is a closed loop consisting of a supply path 76 that runs from the pump 74 to the rear wheel power cylinder 26 via the control valve 30A, and a discharge path 80 that returns to the tank 78, in addition to the hydraulic system. It is considered a circuit.

Here, a flow rate control valve is disposed in each of the supply passages 68 and 76 among the supply and discharge passages on both sides for the front wheels and the rear wheels. That is, the oil supply path 68 on the front wheel side is provided with a main flow control valve 82 that reduces the supply flow rate to the power cylinder 24 as the vehicle speed V increases, and adjusts the steering force in response to the vehicle speed. This makes it a so-called urine flow control type vehicle speed sensitive power steering device.

Note that the flow rate controlled by the main flow control valve 82 takes not only the vehicle speed V but also the steering angle θ as a control factor, and reduces the flow rate change rate at a relatively slow vehicle speed in accordance with the steering angle used at the slow vehicle speed. The rate of change in flow rate at relatively high vehicle speeds is made to correspond to the steering angle used, so that the rate of change in flow rate is reduced at a greater rate than at slower vehicle speeds.

This control command is given to controller 84.

In addition, an oil correction flow control valve 86 is provided in the rear wheel side oil supply passage 76 so as to reduce the supply flow rate to the rear wheel power cylinder 26 in accordance with the amount of flow reduction of the main flow control valve 82. It's dressed up. In other words, depending on the vehicle speed ■ and steering angle θ, the value of non/$1.0 or steering force ゛. is adjusted by the key control of the main flow control valve 82, but if the rear wheel control valve 30A is operated by the binion shaft 12 that is common to the front wheel side, the amount of supply to the rear wheel power cylinder 26 will be adjusted as it is. Since the flow rate becomes excessive and the flow rate becomes 1-1, the correction flow rate control valve 86 is used to completely reduce the flow rate so that an excessive flow rate is not supplied. Therefore, the correction flow control valve 8
6, the total flow rate in the rear wheel steering oil supply path 76 is corrected in accordance with the flow rate control amount by the main flow control valve 82 so as to maintain a constant relationship. This correction amount may be proportional to the flow rate control amount by the main flow control valve 82, and can therefore be obtained by directly operating the correction flow control valve 86 via the controller 84 from the vehicle speed V and steering angle θ, which are flow rate control factors. It will be done. The correction flow control valve 86 may have a structure similar to that of the main flow control valve 82.
As shown in the figure, there is a proportional solenoid section 88 actuated by an electric signal from a controller 84, a movable plunger 89 that uses the thrust of the solenoid to throttle the variable throttle hole 87, and generates a differential pressure before and after the throttle hole. This is a flow control valve composed of a valve spool 90 that opens and closes according to the differential pressure of this throttle, and adjusts the flow rate from the pump boat 92 to the cylinder boat 94 according to the opening degree of the throttle, and the remaining amount is transferred to the tank. Bypass port 96.

In a vehicle steering system with such a configuration, the vehicle speed and
The steering angle sensitive front wheel power steering mechanism and the rear wheel 20
In order to have a steering function, a rear wheel power steering mechanism is added, and both of these mechanisms can be operated by a single axis using a pinion shaft 12 that is rotated by operating the handle 10 to simultaneously switch the front and rear valves. Wheel steering can be synchronized with a simple mechanism. Moreover.

Since the structure is synchronized by a hydraulic circuit, there is little play, and accuracy is significantly improved compared to the case of a link mechanism. Also,
Although the flow rate control of the main flow control valve 82 is made responsive to vehicle speed, etc., the unbalance of front and rear wheel steering due to synchronization can be corrected by controlling the total flow rate of the supply flow to the rear wheel power cylinder 26 using the flow rate control valve 86. Main flow control valve 820
Since it can be corrected according to the control amount, the tracking performance of the rear wheels can be optimized and improved, and the (1
1) Eliminates the risk of increased steering sensitivity.

In the above embodiment, a direction switching valve 98 is provided in the oil supply/discharge path between the rear wheel power cylinder 26 and the control valve 30A, so that the front wheel 18 and the rear wheel 20 can be operated in the same direction or in opposite directions as necessary. This allows the vehicle to be steered to.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to synchronize the front wheels and the rear wheels with a simple structure and obtain hydraulic assist force. The following performance is optimized and improved, resulting in an excellent effect of being able to steer with a good front-rear balance.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a vehicle steering system according to an embodiment, Fig. 2 is a sectional view of the control valve structure, Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2, and Fig. 4 is a sectional view of the corrected flow rate control valve. It is a diagram. 10...handle, 12...pinion shaft. 16...Rack, 18...Front wheel, 20...Rear wheel, (12) 24.26...Power cylinder, 30.3OA...
・Control valve, 36, 36A... Swing lever. 48.48A...Valve spool, 66.74...
Pump, 68.76... Supply path, 70.78... Tank, 82... Main flow control valve, 84... Controller, 86... Correction flow control valve. Agent: Tatsuyuki Unuma (and 1 other person) Figure 1 Figure 2 Figure 3 Garden, 445n, -27/17t=mays (*mTokyo Showa G
O-213574 (5) Figure 4 Colletrora calyx 1

Claims (1)

[Claims] (1) At least two control valves that are operated by following the rotational displacement of the pinion shaft in a rack-and-pinion type power steering mechanism are attached, and each control valve is used to supply oil to the power cylinders for steering each front and rear wheel. The front wheel steering oil supply path is provided with a main flow control valve that is sensitive to vehicle speed, etc., and the rear wheel steering oil supply path is provided with a main flow control valve that responds to the amount of flow reduction caused by the main flow control valve.
A vehicle steering system characterized in that it is provided with a correction control valve that reduces a semicircular supply flow rate.