JPS6374775A - Four-wheel steering device for vehicle - Google Patents

Abstract

PURPOSE:To lighten the steering torque and simplify structure by instal ing an auxiliary power means into a connection passage for the front and rear wheel steering mechanisms and constituting a duplicate passage in the steering system by including a rack shaft connected with the front wheels and meshing a steering wheel and a pinion in a rear wheel steering system with the rack shaft. CONSTITUTION:An auxiliary power means 28 for the steering operation of a steering wheel 10 is installed into a communication passage C for the front and rear wheel steering mechanisms A and B, and a duplicate passage F for the front and rear wheel steering systems D and E is constituted, including a rack shaft 14 connected with front wheels 16 and 16. A pinion 13 which is turned integrally with the steering wheel 10 and a pinion 24 which constitutes the rear wheel steering system E are meshed with the rack shaft 14. Therefore, the steering torque for the steering wheel 10 which is necessary for the simultaneous steering of the front and rear wheels 16, 16, and 21, 21 can be reduced by the single power assisting means 28, and the simple structure of the duplicate passage F can be realized. Therefore, the weight of the vehicle can be reduced, and cost cut can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle equipped with power assisting means.

(Prior Art) A four-wheel steering system for a vehicle is known in which the front wheels and the rear wheels are steered by the steering operation of the steering wheels. Since the resultant force of the external force and the external force acting on the rear wheels from the road surface becomes a steering reaction force when steering the steered wheels, it is necessary for the driver or the steered wheels to apply a steering torque that exceeds the steering reaction force. In order to solve this problem, it is sufficient to equip the vehicle with a power steering device including a detection means for detecting steering torque and a power assist means for assisting the steering operation of the steered wheels.

(Problem to be solved by the invention) However, since the conventional power steering device is for steering the front wheels, the external force acting on the rear wheels of the steering torque is not detected by the detection means, and the The steering operation of the steered wheels for wheel steering is not assisted.

Therefore, in order to reduce the steering torque, it is conceivable to equip separate power steering devices for the front wheels and rear wheels, but according to this, the steering torque detection means and the power assisting means are each equipped with two separate power steering devices. This results in an increase in vehicle weight and cost.

Therefore, it is an object of the present invention to reduce the steering torque of the steered wheels required for simultaneous front and rear wheel steering by a single power assisting means, and to simplify the structure of the overlapping path between the front wheel steering system and the rear wheel steering system. To provide a four-wheel steering device for a vehicle that achieves a reduction in vehicle weight and cost.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the objects, the present invention provides a method for steering the front wheels 16 and 16 as well as the rear wheels by steering the steering wheel 10.
1.21 In a four-wheel steering system for a vehicle configured to steer a vehicle, a connecting path C connects a front wheel steering mechanism A and a rear wheel steering mechanism B.
Connected via.

A power assisting means 28 for assisting the steering operation of the steered wheels 10 is provided on the connecting path C, and the steered wheels 1O and the front wheels 16.
16, and a front wheel steering system connecting the steered wheels 10 and rear wheels 21.
21? The rear wheel steering system E is configured to form an overlapping path F, and the overlapping path F is configured to include a rack shaft 14 connected to the front wheels 16 and 16 side.
It is characterized in that a pinion 13 that rotates integrally with the rear wheel steering system E is meshed with a nion 24 that constitutes the rear wheel steering system E.

(Function) Since the power assist means 28 for assisting the steering operation of the steered wheels 10 is provided in the connection path C between the front wheel steering mechanism A and the rear wheel steering mechanism B, the steering necessary for simultaneous front wheel and rear wheel steering is provided. The steering torque of the wheels 10 can be reduced by a single power assisting means 28.

The overlapping path F between the front wheel steering system and the rear wheel steering system E is configured to include the rack shaft 14 connected to the front wheels 16 and 16 side,
Since the pinion 13 that rotates integrally with the steering wheel 10 is engaged with the rack shaft 14 and the nion 24 when configuring the rear wheel steering system E, the structure of the overlapping path F can be simplified.

Therefore, it is possible to reduce the weight and cost of the vehicle.

Furthermore, the load applied to the pinion 24 and link shaft 14 constituting the rear wheel steering system E can be reduced by the power assist means 28 provided in the connection path C between the front wheel steering mechanism A and the rear wheel steering mechanism B.

(Example) Examples will be described below based on the accompanying drawings.

As shown in the figure, the steering shaft 11 of the steering wheel lO is inserted into the gear box 12 for steering the front wheels, and the pinion 13 provided on the steering shaft 11 is engaged with a rack shaft 14 that is movable in the left and right direction within the gear box 12. Left and right tie rods 15.15 are connected to both ends of the shaft 14, and knuckle arms 17, 17 that support front wheels 16.16 are connected to the tie rods 15.15. The ship is steered to Therefore, the front wheel steering mechanism A is formed from the rack shaft 14 to the knuckle arms 17, 17.

Further, a rear wheel steering gear box 18 is disposed at the rear of the vehicle, and left and right tie rods 20 and 20 are connected to both ends of a rack shaft 19 that is movable in the left and right directions within this gear box 18. A knuckle arm 22.22 supporting the rear wheels 21.21 is connected to the knuckle arm 22.22, which forms a rear wheel steering device aB.

Furthermore, an operating shaft 23 is installed between the front and rear rack shafts 14 and 19, and the operating shaft 23 meshes with a pinion 24 provided at the front end or the rack shaft 14, and also meshes with a pinion 25 provided at the rear end or the rack shaft 19. This operating shaft 23 forms a connection path C between the front wheel steering mechanism A and the rear wheel steering mechanism 8.

A pinion 26 is further provided near the rear of the operating shaft 23, and another rack shaft 27 meshes with this pinion 26, and this rack shaft 27 is connected to a piston rod 29 of a power cylinder 28, which is a power assisting means. combined. The power cylinder 28 has a piston rod 29 that expands and contracts depending on the hydraulic pressure selectively supplied to two chambers separated by a piston, and rotational power is transmitted from the power cylinder 28 to the operating shaft 23 via the rack shaft 27 and pinion 26. Granted.

A control valve 30, which is a detection means for detecting steering torque, is coupled to the tip of the steering shaft 11 protruding from the front wheel steering gear box 12, and the control valve 30 is connected to the valve housing 3.
The valve housing 3 is slidably housed in the valve housing 3.
1 and the power cylinder 28 are connected via two oil passages 32 and 33. Furthermore, an oil supply path 36 from an oil tank 34 with an oil pump 35 interposed therebetween, and an oil return path 37 to the oil tank 34 are connected to the valve housing 31 .

Here, the control valve 30 is an open center type four-way switching valve, and as shown in the figure, the pinion 13 of the steering shaft 11 and the rack shaft 14 are engaged by helical teeth, so that the control valve 30 or the steering wheel lO can be rotated. In response, it slides slightly back and forth, and as is known, hydraulic oil is selectively supplied to two chambers within the power cylinder 28 to perform a switching operation.

Thus, the front wheel steering system that connects the steered wheel lO to the front wheels 16 and 16 and the rear wheel steering system E that connects the steered wheel lO to the rear wheels 21 and 21 overlap from the steered wheel lO to the rack axis 14. This is common to the route F, and in the embodiment for this overlapping route F, the steering shaft 11 is provided with a detection means for detecting the steering torque of the steered wheel 1O, that is, a control valve 30.

A power auxiliary means, ie, a power cylinder 28, which is connected to the control valve 30 and performs a switching operation, is provided on the operating shaft 23 forming the connection path C between the front wheel steering mechanism A and the rear wheel steering mechanism 8.

Therefore, the power cylinder 28 is used for both the front wheels and the rear wheels, and the steering torque of the steered wheels 10 required for simultaneous steering of the front wheels 16.16 and the rear wheels 21.21 is reduced.

Furthermore, the overlapping path F is the rack shaft 1 connected to the front wheel 16.16 side.
4, and this rack shaft 14 has a steering wheel weight of 0.
In addition to the pinion 13 that rotates integrally with the rear wheel steering system E, the pinion 24 that constitutes the rear wheel steering system E also meshes with the pinion 13, which simplifies the structure of the overlapping path F at the link shaft 14 portion.

In addition, the power steering 28 provided on the operating shaft 23 between the front wheel steering mechanism A and the rear wheel steering mechanism 8 reduces the load applied to the pinion 24 and rack shaft 14 that constitute the rear wheel steering system E.

(Effects of Ill) As described above, according to the present invention, the power assisting means for assisting the steering operation of the steered wheels is provided in the connection path between the front wheel steering mechanism and the rear wheel steering mechanism. The steering torque of the steered wheels required for simultaneous steering can be reduced by a single power assisting means, and the overlapping path of the 1II wheel steering system and the rear wheel steering system can be reduced by including a rack shaft connected to the front wheel side. A pinion that rotates together with the steering wheel and a pinion that constitutes the rear wheel steering system are engaged with this rack shaft, which makes it possible to simplify the structure of the overlapping path, thereby reducing the weight of the vehicle. And cost town can be achieved. Furthermore, the power assisting means provided in the connection path between the front wheel steering mechanism and the rear wheel steering mechanism can reduce the load applied to the pinion and rack shaft that constitute the rear wheel steering system.

[Brief explanation of the drawing]

The drawing is a top view showing the general basic structure of a four-wheel steering device according to the present invention. In addition, in the drawing, IO is a steering wheel, 13 is a pinion, 14 is a rack shaft, 16 is a front wheel, 21 is a rear wheel, 24 is a pinion, 2
8 is a power assisting means, 30 is a detection means, A is a front wheel steering mechanism, B is a rear wheel steering mechanism, C is a connection path, D is a front wheel steering system,
E is the rear wheel steering system, and F is the overlapping route.

Claims (1)

[Scope of Claims] A four-wheel steering system for a vehicle in which front wheels and rear wheels are steered by steering operation of a steering wheel, comprising: a front wheel steering mechanism and a rear wheel steering mechanism connected via a connecting path; A power auxiliary means for assisting the steering operation of the steered wheels is provided on the connecting route, and an overlapping route is formed between the front wheel steering system that connects the steered wheels and the front wheels, and the rear wheel steering system that connects the steered wheels and the rear wheels. The overlapping path includes a rack shaft connected to the front wheel side, and a pinion that rotates together with the steering wheel and a pinion that constitutes a rear wheel steering system are meshed with the rack shaft. The vehicle's four-wheel steering system is a feature.