JP3079926B2 - Drive steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus for a vehicle, for example.

[0002]

2. Description of the Related Art Among steering devices for vehicles, a steering device with power assist (a so-called power steering device) is generally known. (As an example, see the actual opening 60-24
670).

This steering system includes a hydraulic pump for generating a steering assist force (assist force) in addition to a steering mechanism composed of a rack and pinion. The hydraulic pump is driven by a motor, and is further connected to left and right cylinder chambers of an assist power cylinder via a control valve. When the steering wheel is steered, a motor is driven based on the steering torque, and pressure fluid from a hydraulic pump is supplied to a power cylinder to obtain a steering assist force (assist force).

In the conventional steering apparatus with power assist as disclosed in the above publication, the pressure fluid generated by the hydraulic pump is distributed by a control valve (for example, a four-way switching valve) according to the left and right steering of the steering wheel, and the power is increased. The structure is such that the oil is supplied to the left and right cylinder chambers of the cylinder, and since the hydraulic pump and the control valve are separately provided, it has been difficult to reduce the size and cost of the device. In particular,
The control valve as described above itself has a complicated structure, which results in an increase in size and cost of the device.

[0005]

SUMMARY OF THE INVENTION In consideration of the above fact, the present invention can reduce the steering force of the steering shaft by quickly applying an auxiliary driving force to the steered rod in accordance with the steering force of the steering shaft. It is another object of the present invention to provide a power steering device capable of realizing this at a low cost with a simple and compact structure.

[0006]

According to a first aspect of the present invention, there is provided a power steering apparatus for connecting a left and right knuckle arm to steer a steered wheel, and a steering wheel attached to the power steering apparatus. A steering shaft that transmits a steering force to the steering rod to be driven in the axial direction and whose tip is displaced by a steering reaction force; and a power cylinder provided on the steering rod for an auxiliary steering force. And a cam ring that is arranged corresponding to the tip of the steering shaft and that constitutes a suction-side pump chamber and a discharge-side pump chamber by a rotor that is moved and rotated according to the displacement of the steering shaft tip. The suction-side pump chamber and the discharge-side pump chamber are respectively communicated with a cylinder chamber of the power cylinder, and a displacement variable in which a discharge amount and a discharge direction are changed by movement of the cam ring when the steering shaft is steered. And it includes a pump, a.

According to a second aspect of the present invention, in the power steering apparatus according to the first aspect, the power steering apparatus is disposed corresponding to a moving direction of the cam ring, and is provided in each of the suction side pump chamber and the discharge side pump chamber. A hydraulic reaction mechanism is provided which is in communication with the hydraulic pump and is operated by hydraulic pressure supplied from the variable displacement pump to suppress the movement of the cam ring in accordance with the hydraulic pressure.

[0008]

In the power steering apparatus according to the first aspect, when the steering shaft is steered, the steering force of the steering shaft is transmitted to the steered rod, the steered rod is driven in the axial direction, and the steered wheels are steered. You. Also,
The pressure fluid generated by the variable displacement pump is supplied from the discharge side pump chamber formed by the rotor and the cam ring to the cylinder chamber of the power cylinder and returned to the suction side pump chamber. Thereby, the auxiliary driving force is applied to the steered rod, and the steering force of the steering shaft is reduced.

Here, immediately after the steering shaft is steered, the steering rod (that is, the tire side) has a large resistance, so that the steering rod is immovable. Displacement. Accordingly, the cam ring of the variable displacement pump provided corresponding to the tip of the steering shaft is moved, and the volumes of the suction side pump chamber and the discharge side pump chamber formed by the rotor are changed. By changing the volume of the pump chamber, the discharge amount is changed and the discharge direction is switched. In other words, the amount of pressure fluid supplied to the cylinder chamber of the power cylinder is changed by the cam ring moved by the steering reaction of the steering shaft, and the direction of the supply is also switched.

That is, the cam rings constituting the suction-side pump chamber and the discharge-side pump chamber have the same function as the control valve used in the conventional steering device, and have an auxiliary function corresponding to the left and right steering forces of the steering shaft. Driving force can be applied to the steering rod. Therefore, the conventional control valve becomes unnecessary (can be eliminated), and the device is downsized.

Further, since the cam ring is moved in tandem with the steering of the steering shaft and the volumes of the suction side pump chamber and the discharge side pump chamber are changed, the auxiliary driving force is quickly changed following the steering of the steering shaft. It is possible to reduce the steering force of the steering shaft by applying to the steering rod.

As described above, in the power steering apparatus according to the first aspect, it is possible to reduce the steering force of the steering shaft by quickly applying the auxiliary driving force to the steered rod in accordance with the steering force of the steering shaft. In addition, this can be realized with a simple and small structure at low cost.

In the power steering apparatus according to the second aspect, the cam ring is moved in accordance with the steering of the steering shaft, the volumes of the suction side pump chamber and the discharge side pump chamber are changed, and the pressure supplied to the cylinder chamber of the power cylinder is changed. The fluid supply amount is changed and its supply direction is also switched, but the pressure fluid supplied to the cylinder chamber is also supplied to the hydraulic reaction mechanism.

Here, the hydraulic reaction mechanism is arranged corresponding to the moving direction of the cam ring, and operates by the supplied hydraulic pressure to suppress the movement of the cam ring in accordance with the hydraulic pressure of the pressure fluid supplied to the cylinder chamber. I do. That is, a hydraulic reaction force type power steering apparatus can be realized with an extremely simple configuration.

[0015]

FIG. 1 is a sectional view showing the overall structure of a power steering device 10 according to a first embodiment of the present invention. FIG. This is shown in the figure.

The power steering device 10 includes a steering rod 14 as an output shaft disposed in a housing 12.
The steered rod 14 is supported by bushes 16 near both ends in the axial direction, and further connected to steered wheels via tie rods (both not shown) connected to a knuckle arm. Thus, the steered wheels 14 can steer the steered wheels by moving in the axial direction. A rack gear 18 is formed on the steering rod 14. The housing 12 supports a steering shaft 20 as an input shaft. The steering shaft 20 includes the steering rod 1
4 and is supported by the housing 12 by the bearing 22. The bearing 22 is of a self-centering type, and the steering shaft 20 can slightly swing about the bearing 22 as a fulcrum. The steering shaft 20 is provided with a pinion 24, which meshes with the rack gear 18 of the steering rod 14.

The housing 12 is provided with a power cylinder 26 corresponding to the steering rod 14. The power cylinder 26 includes a piston 28 fixed to the steering rod 14.
And a cylinder chamber 30 and a cylinder chamber 32 which are separated from each other by the piston 28 are provided.

At the tip of the steering shaft 20, a variable displacement pump 34 is arranged correspondingly. As shown in FIG. 3, the variable displacement pump 34 is of a vane type, and a rotor 38 and a cam ring 40 are arranged in a case 36. These rotor 38 and cam ring 40
The pump chamber 42 and the pump chamber 44 are constituted by these. A plurality of vane plates 46 are radially attached to the rotor 38 and are connected to a motor 47. By driving the motor 47, the rotor 38 rotates to supply hydraulic oil from the port 48 or the port 50.

On the other hand, the cam ring 40 is movable relative to the rotor 38. The movement of the cam ring 40 changes the volumes of the pump chamber 42 and the pump chamber 44. A pair of springs 52 and 54 are provided between the cam ring 40 and the case 36,
The cam ring 40 is held at a neutral position (the state shown in FIG. 3). Further, a fitting hole 56 is formed at an end of the cam ring 40, and the pin 58 provided at the tip of the steering shaft 20 described above enters therein. Thereby, the steering shaft 2
0 swings on the bearing 22 as a fulcrum, whereby the cam ring 40 is moved against the urging force of the springs 52 and 54.

When the steering shaft 20 (pin 58) is in the neutral state, the rotor 38 and the cam ring 40 are relatively in the neutral position, and the pump chambers 42 and 44 have the same volume. The dimensions etc. are set.

The variable displacement pump 34 having such a configuration is described.
One port 48 is connected to the cylinder chamber 30 of the power cylinder 26, and the other port 50 is connected to the cylinder chamber 32.

In the power steering device 10 having the above configuration, when the vehicle is traveling straight (ie, when the steering shaft 20 is in the neutral state),
As shown in FIG. 3, the rotor 38 of the variable displacement pump 34 and the cam ring 40 are at a relatively neutral position. Therefore, one pump chamber 42 and the other pump chamber 44 have equal volumes. For this reason, the flow of hydraulic oil in one pump chamber 42 and the other pump chamber 44 is balanced, and
8. No hydraulic oil is supplied from the port 50.

When the steering shaft 20 is steered in either the left or right direction (for example, when turning right as shown in the direction of arrow A in FIG. 4), the steering force of the steering shaft 20 is transmitted via the pinion 24 and the rack gear 18. The steering rod 14 is transmitted to the steering rod 14.
Is driven in the axial direction (direction of arrow B) to steer the steered wheels.

In this case, immediately after the steering shaft 20 is steered, the steering rod 14 (that is, the tire side) has a large resistance, so that the steering rod 14 is immovable. It swings slightly (the direction of arrow C in FIG. 4). For this reason, as shown in FIG.
The cam ring 40 connected to 8 is moved in the same direction, the volume of one pump chamber 42 constituted by the rotor 38 decreases, and the volume of the other pump chamber 44 increases.
Therefore, the hydraulic oil in the other pump chamber 44 is supplied from the port 48 to the cylinder chamber 30 of the power cylinder 26, and is returned from the cylinder chamber 32 via the port 50.

As a result, an auxiliary driving force in the right-turn direction (direction of arrow B) is applied to the turning rod 14, and the steering force of the steering shaft 20 is reduced.

On the other hand, when turning left as shown in the direction of arrow D in FIG. 6, the steering shaft 20 swings in the opposite direction to the above with the bearing 22 as a fulcrum by the same operation as described above (in the direction of arrow E in FIG. 6). ). For this reason, as shown in FIG. 7, the cam ring 40 connected to the pin 58 of the steering shaft 20 is moved in the same direction, and the one pump chamber 4 constituted by the rotor 38 is moved.
2, the volume of the other pump chamber 44 is reduced. Therefore, the hydraulic oil in one pump chamber 42 is supplied from the port 50 to the cylinder chamber 32 of the power cylinder 26, and is returned from the cylinder chamber 30 via the port 48.

As a result, an auxiliary driving force in the left turning direction (the direction of arrow F) is applied to the turning rod 14, and the steering force of the steering shaft 20 is reduced.

As described above, in the power steering apparatus 10, the cam ring 40 of the variable displacement pump 34 is moved in accordance with the steering of the steering shaft 20, and the volumes of the pump chamber 42 and the pump chamber 44 formed by the rotor 38 are reduced. Be changed. By changing the volumes of the pump chambers 42 and 44, the discharge amount of the hydraulic oil is changed and the discharge direction is switched. In other words, the amount of hydraulic oil supplied to the cylinder chamber 30 and the cylinder chamber 32 of the power cylinder 26 is changed by the cam ring 40 moved by the steering reaction of the steering shaft 20, and the direction of the supply is also changed. Can be switched.

That is, the pump chamber 42 and the pump chamber 44
The cam ring 40 has the same function as a control valve used in a conventional steering device, and automatically controls an auxiliary driving force (assist force) according to left and right steering forces of the steering shaft 20. To the steering rod 14. Therefore, the conventional control valve becomes unnecessary (can be eliminated), and the device is downsized.

Further, since the cam ring 40 is moved in tandem with the steering of the steering shaft 20 and the volumes of the pump chambers 42 and 44 are changed, the auxiliary driving force is quickly followed by the steering of the steering shaft 20. The steering force of the steering shaft 20 can be reduced by applying it to the steering rod 14.

As described above, in the power steering apparatus 10 according to the first embodiment, the assisting driving force is quickly applied to the turning rod 14 in accordance with the steering force of the steering shaft 20 to reduce the steering force of the steering shaft 20. This can be reduced, and this can be realized with a simple and small structure at low cost.

Next, another embodiment of the present invention will be described. It should be noted that the same parts as those of the first embodiment
The same reference numerals as in the embodiment are given, and the description is omitted.

FIG. 8 shows the structure of a main part of a power steering device 60 according to the second embodiment.

The power steering device 60 includes a pair of cylinders 62 and 64 that constitute a hydraulic reaction force mechanism. The cylinder 62 and the cylinder 64 are arranged at positions facing the moving direction of the cam ring 40, respectively.
An oil chamber 66 and an oil chamber 68 are provided by the cam ring 40, respectively.
Is composed. The oil chamber 66 and the oil chamber 68 are connected to the port 48 and the port 50, respectively.

In the power steering device 60, the first
Similarly to the power steering device 10 according to the embodiment, the cam ring 40 of the variable displacement pump 34 is moved in accordance with the steering of the steering shaft 20, and the pump chamber 4 is constituted by the rotor 38.
2 and the volume of the pump chamber 44 are changed, the amount of hydraulic oil supplied to the cylinder chamber 30 and the cylinder chamber 32 of the power cylinder 26 is changed, and the direction of the supply is also switched. From port 50 to cylinder chamber 3
0, the hydraulic oil supplied to the cylinder chamber 32 is also supplied to the oil chamber 66 or the oil chamber 68.

For example, as shown in FIG. 8, when the steering shaft 20 is turned to the right, the cam ring 40 is moved to reduce the volume of one pump chamber 42 and increase the volume of the other pump chamber 44, and the right-hand direction is increased. The auxiliary driving force is applied to the steering rod 14. In this case, the operating oil in the other pump chamber 44 is also supplied to the oil chamber 68 via the port 50. Therefore, the pressure of the oil chamber 68 increases, and thereby the movement of the cam ring 40 is suppressed.

As described above, in the power steering device 60, the cylinders 62 and 64 constituting the hydraulic reaction force mechanism are arranged to face the moving direction of the cam ring 40, and the oil chamber 66 or the oil The chamber 68 is pressurized and the movement of the cam ring 40 is suppressed. That is, a hydraulic reaction force type power steering apparatus can be realized with an extremely simple configuration.

In the above-described first and second embodiments, the power steering devices 10 and 60 have been described as so-called rack and pinion type steering devices. However, the present invention is not limited to this, and the steering devices having other configurations are applicable. The present invention is also applicable to a device.
Similarly, in the first and second embodiments, the variable displacement pump 34 has been described as a so-called vane type. However, the present invention is not limited to this, and a pump having another configuration can be applied.

[0039]

As described above, the power steering apparatus according to the present invention can reduce the steering force of the steering shaft by quickly applying the auxiliary driving force to the steering rod in accordance with the steering force of the steering shaft. ,
In addition, there is an excellent effect that this can be realized at a low cost with a simple and small structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a power steering device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing details of a main part of the power steering device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing details of a variable displacement pump of the power steering apparatus according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view corresponding to FIG. 2, showing a configuration of a main part of the power steering apparatus according to the first embodiment of the present invention, and showing a state where a steering shaft is steered to the right.

FIG. 5 is a cross-sectional view corresponding to FIG. 3 and showing a configuration of a variable displacement pump of the power steering apparatus according to the first embodiment of the present invention, with a steering shaft being steered to the right.

FIG. 6 is a cross-sectional view corresponding to FIG. 4, showing a configuration of a main part of the power steering apparatus according to the first embodiment of the present invention, and showing a state where a steering shaft is steered to the left.

FIG. 7 is a cross-sectional view corresponding to FIG. 5 and showing a configuration of a variable displacement pump of the power steering apparatus according to the first embodiment of the present invention, in which a steering shaft is steered to the left.

FIG. 8 is a sectional view showing a configuration of a main part of a power steering device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power steering device 14 Steering rod 18 Rack gear 20 Steering shaft 24 Pinion 26 Power cylinder 30 Cylinder room 32 Cylinder room 34 Variable capacity pump 38 Rotor 40 Cam ring 42 Pump room 44 Pump room 48 Port 50 Port 58 Pin 60 Power steering device 62 Cylinder (hydraulic reaction mechanism) 64 Cylinder (hydraulic reaction mechanism) 66 Oil chamber 68 Oil chamber

Claims (2)

(57) [Claims] 1. A steering rod for connecting left and right knuckle arms to steer steered wheels, and a steering wheel attached to the steering rod and connected to the steering rod to transmit steering force to the steering rod. A steering shaft whose tip is displaced by a steering reaction force while being driven in the direction, a power cylinder for an auxiliary steering force provided on the steering rod, and a steering shaft disposed corresponding to the tip of the steering shaft; A cam ring that forms a suction-side pump chamber and a discharge-side pump chamber by a rotor that is moved and rotated in accordance with the displacement of the tip end of the steering shaft, wherein the suction-side pump chamber and the discharge-side pump chamber are A variable displacement pump that is communicated with a cylinder chamber and that changes a discharge amount and a discharge direction by moving the cam ring when the steering shaft is steered. 2. The movement of the cam ring, which is arranged corresponding to the direction of movement of the cam ring, communicates with the suction-side pump chamber and the discharge-side pump chamber, and is operated by hydraulic pressure supplied from the variable displacement pump. The power steering apparatus according to claim 1, further comprising a hydraulic reaction force mechanism that suppresses the pressure in accordance with the hydraulic pressure.