JP3168481B2 - Power steering device - 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 device.

[0002]

2. Description of the Related Art A conventional power steering device is shown in FIG.
As shown in FIG. 7, in order to keep the pressure before and after the metering orifice MO of the flow control valve FC constant, a bypass hole B through which excess fluid is bypassed from the discharge side of the pump P to the suction side or the low pressure side.
A sensor S that controls the opening of H and electrically detects the steering angle or steering torque of the steering wheel HD, and an electromagnetic servo valve ES according to a control signal output by a control circuit C based on the detection signal of the sensor S. When the steering angle or the steering torque is equal to or less than the set value, a part of the pressure oil supplied from the flow control valve FC is supplied to the low pressure side via the electromagnetic servo valve ES, and the flow supplied to the rotary valve RV It lowers.

[0003] In the above-mentioned conventional apparatus, a power cylinder P is controlled by a rotary valve RV as a servo valve through a high-pressure hose HH based on a flow rate controlled by an electromagnetic servo valve.
The steering direction is controlled by controlling the moving direction of C.

[0004]

As shown in FIG. 10, the conventional power steering apparatus reduces the flow rate when the steering angle or the like is equal to or smaller than a set value. Since the control circuit C and the electromagnetic servo valve ES are required, there is a problem that the device is complicated and expensive.

Accordingly, the present inventors have focused on the technical idea of the present invention that lowers the flow rate based on the pressure of the pressure oil supplied from the flow control valve when the steering wheel is in the neutral position, and further researches and develops the same. As a result of reducing the supply flow rate of the flow control valve by the bypass valve, the sensor, control circuit, and electromagnetic servo valve are not required, thereby reducing pressure loss and energy loss in the entire apparatus and realizing energy saving. The invention has been achieved which achieves the objectives.

[0006]

The power steering apparatus according to the present invention (first invention according to claim 1) has a spring for controlling the flow rate of the pressure oil discharged from the supply pump to be constant.
When the handle is neutral based on the pressure of the hydraulic oil supplied from the flow control valve having the spring chamber provided, the spring chamber of the flow control valve is communicated with the low pressure side.
By the way, a bypass valve for lowering the level of the flow rate of the pressure oil supplied from the flow control valve, a servo valve for controlling the supply direction of the pressure oil from the flow control valve according to the steering direction, and a pressure control by the servo valve And a power cylinder that is steered in a direction corresponding to the oil supply direction.

[0007] In the power steering apparatus according to the present invention (the second aspect of the present invention), a spring is provided in order to keep the front-rear pressure of the measuring orifice provided in the discharge passage of the supply pump constant. By controlling the opening of the bypass passage leading to the low pressure side by the pressure and spring force acting on the spring chamber,
It has a control valve for controlling the flow rate, and has a flow control valve for supplying a controlled amount of pressure oil, and a spool that moves according to the pressure of the pressure oil supplied from the flow control valve, and the pressure of the pressure oil When the pressure is low, the spring chamber of the flow control valve communicates with the low pressure side by the positional relationship of the spool, thereby reducing the flow level of the pressure oil supplied from the flow control valve, and the pressure oil from the flow control valve. It comprises a servo valve for controlling the supply direction in accordance with the steering direction, and a power cylinder for steering in a direction in accordance with the supply direction of the pressure oil controlled by the servo valve.

[0008]

The power steering apparatus according to the first aspect of the present invention having the above-described structure, when the steering wheel is in a neutral state in which the steering wheel is not steered ,
By connecting the low pressure side with the spring chamber of the flow control valve,
As the pressure of the pressure oil supplied from the flow control valve decreases , the flow rate of the pressure oil from the flow control valve is reduced by the bypass operation of the bypass valve, and is supplied from the flow control valve when the steering wheel is steered. Since the pressure of the pressurized oil is increased, the bypass operation of the bypass valve is not performed. Therefore, the flow level of the pressurized oil from the flow control valve is increased, and the supply direction of the pressurized oil is controlled by the servo valve according to the steering direction. The steering is performed in the steering direction by the power cylinder.

In the power steering apparatus according to the second aspect of the present invention, since the pressure of the pressure oil supplied from the flow control valve becomes low when the steering wheel is in neutral without steering, the spool of the bypass valve moves and the flow control valve is moved. The pressure oil on the discharge side of the supply pump, which is on the upstream side of the metering orifice of the flow control valve, is supplied to the low-pressure side via the bypass passage in order to communicate the spring chamber of the metering orifice with the low-pressure side. The flow level of the pressure oil supplied from the flow control valve on the downstream side is reduced.

In the second invention, when the steering wheel is steered, the pressure of the hydraulic oil increases due to the operation of the servo valve. Therefore, the spool of the bypass valve is moved in the opposite direction to the above, and the flow control valve is moved. Since the communication between the spring chamber and the low pressure side is cut off, the bypass passage of the flow control valve is cut off. Therefore, the communication between the discharge side and the low pressure side of the supply pump, which is on the upstream side of the metering orifice of the flow control valve, is interrupted, and the pressure on the upstream side of the metering orifice increases. The flow level of the pressurized oil is increased, the supply direction of the pressurized oil is controlled by the servo valve according to the steering direction, and the steering is performed in the steering direction by the power cylinder.

[0011]

According to the power steering apparatus of the first invention having the above-mentioned effects, the spring chamber of the flow control valve communicates with the low pressure side when the steering wheel is in a neutral state without steering.
As a result, the flow rate of the pressure oil from the flow control valve is reduced by the bypass operation of the bypass valve, so that the pressure loss and energy loss of the entire device are reduced, energy saving is achieved, and the sensor, the control circuit, and the solenoid valve are reduced. This has the effect of not being necessary.

In the power steering apparatus according to the second aspect of the present invention, the spool of the bypass valve moves in the neutral state, and the pressure oil on the discharge side of the supply pump upstream of the metering orifice of the flow control valve is reduced to the low pressure side. And, as a result, the flow level of the pressure oil from the flow control valve is reduced, so that the pressure loss and energy loss of the entire device are reduced,
This achieves the effect of realizing energy saving and eliminating the need for a sensor control circuit and a solenoid valve.

[0013]

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

(First Embodiment) A power steering apparatus according to a first embodiment is a first and second embodiments of the present invention. As shown in FIG. 1 to FIG. An oil supply unit 1, a bypass valve 2 for lowering a flow level of the pressure oil supplied by the pressure oil supply unit 1 when the handle HD is in a neutral position, and a rotary valve as a servo valve for supplying the pressure oil in a direction corresponding to the steering direction. 3 and rotary valve 3
And a power cylinder 4 that performs power steering by the relative movement between the piston and the cylinder by the pressure oil supplied from the power cylinder.

The pressure oil supply unit 1 comprises a supply pump 10 driven by the onboard engine EG, and a flow control valve 11 for controlling the flow rate Qo of the pressure oil discharged from the supply pump 10 to a constant flow rate Q. The flow control valve 11 is connected to the supply pump 1
And a measuring orifice 12 disposed in the discharge side passage of the pressure chamber 0.
And a control valve 14 that controls the opening of the bypass passage 13 that is urged by the spring 16 and communicates with the low-pressure side to maintain the front-rear pressure constant.

The bypass valve 2 has a first port 22 communicating with a passage communicating with the metering orifice 12 and an orifice 2.
3 connected to the spring chamber 15 of the flow control valve 11
20 having a port 24 and a third port 25 communicating with the low-pressure side, a spool 21 inserted in the cylinder 20 to form a slit 21S,
And a spring 26 inserted between the third port 25 and the end of the cylinder 20 provided with the third port 25.

As shown in FIG. 2, the rotary valve 3 is coaxially rotatably housed in a rack-and-pinion type gear housing 30 in the gear housing and connected to each other via a torsion bar 31 so as to be relatively rotatable. Input shaft 32 connected to a steering handle (not shown in FIG. 2)
And an output shaft 33 connected to a rack shaft 34 and an input shaft 3
2 and the high pressure hose 3H connected to the flow control valve 11 by the relative rotation of the inner shaft 35 provided on the output shaft 33 and the outer valve 36 provided on the output shaft 33, and the input shaft 32 and the output shaft 33 accompanying the steering of the handle HD. Supply port S
P is connected to one of the first and second cylinder ports 38 and 39 and the other is connected to the discharge port EP. A rotary type directional control valve 37 and a rack shaft 34 formed at the tip of an output shaft 33 are provided. And meshed pinion teeth PG.

The power cylinder 4 has a piston 41 connected to a steering mechanism interposed in a cylinder 42 and a directional control valve 37.
The moving direction of the piston 41, that is, the steering direction of the steering mechanism is determined by which of the first and second cylinder ports 38, 39 is supplied with the pressure oil.

In the first embodiment having the above-described structure, the pressure oil of the flow rate Q ₀ discharged from the supply pump 10 driven by the on-vehicle engine is supplied by the flow control valve 11 at a constant flow rate Q
Is controlled and supplied to the pressure oil.

At this time, when the steering wheel HD is in a neutral state in which the steering wheel is not steered, the pressure oil of the flow rate Q supplied from the flow control valve 11 is supplied from the supply port SP of the rotary valve 3 through the high pressure hose 3H. Since the pressure is supplied to both the first and second cylinder ports 38 and 39 and discharged to the low pressure side, the pressure is reduced. Therefore, since the spring force of the spring 26 is greater than the pressing force due to the pressure acting via the first port 22 of the bypass valve 2, the state in which the spring 26 is pressed to the left in FIG. ), The spring chamber 15 of the flow control valve 11
A second port 24 connected to the spool 21 and a third port 25 connected to the low pressure side have a slit 21S formed in the spool 21.
, The pressure oil in the spring chamber 15 of the flow control valve 11 flows to the low pressure side, and the pressure in the spring chamber 15 decreases.

Since the discharge pressure of the supply pump 10 is acting on the upper part of the valve 14 of the flow control valve 11 in FIG. 1, the valve 14 moves downward in FIG. 1 and the opening of the bypass passage 13 is enlarged. (Illustrated state), the pressure oil supplied from the supply pump 10 is supplied to the rotary valve 3 and the power cylinder 4 via the measuring orifice 12 in order to supply more pressure oil to the low pressure side via the bypass passage 13. The oil flow level is reduced to Qn as shown by the dashed line in FIG. The pressure-flow characteristics of the metering orifice 12 are as shown in FIG.

When the steering wheel HD is steered, the pressure acting on the first port 22 of the bypass valve 2 increases, and the spool 21 is moved rightward in FIG. In order to disconnect the low pressure side of the spring chamber 15 of the flow control valve 11, the pressure of the spring chamber 15 increases and the valve 14 is moved upward in FIG. 1 to reduce the opening of the bypass passage 13, and through the metering orifice 12. As shown in FIG. 4, the flow rate Q supplied gradually increases from Qn and returns to the original high level Qh when the pressure reaches Ps.
Power steering is performed by the pressure oil.

In the first embodiment having the above operation, when the steering wheel HD having a certain ratio with respect to time is in the neutral state, the level of the flow rate of the pressure oil supplied to the rotary valve 3 and the power cylinder 4 is changed during steering. Since it can be reduced from Qh to Qn, supply pump, high pressure pipe, rotary valve,
Since the pressure loss in each part of the power cylinder and other devices is reduced, the effect of reducing energy loss and realizing energy saving is achieved.

(Second Embodiment) A power steering device according to a second embodiment is one in which the first and second inventions are applied to a power steering device responsive to an engine speed.
A description will be given focusing on differences from the first embodiment with reference to FIG.

The power steering device of the second embodiment is
In the first embodiment, a rotation speed sensitive orifice 5 is added in parallel with the measuring orifice 12 of the pressurized oil supply unit 1 of FIG.
As shown in FIG.
The pressure oil upstream of the metering orifice 12 is guided to the right side, and the spring 52 having a constant urging force is disposed. The rotation speed of the engine EG is, for example, N1 rotation (rp.
m. ), The supply pump 1
Since the pressure of the pressure oil supplied from 0 overcomes the pressure of the pressure oil acting on the right side of the spool 51 and the spring force of the spring 52, the spool 51 is moved rightward in FIG. 5 (leftward in FIG. 6).
, And N2 rotations (r.
p. m. ), The spool 51 reaches the right end (the left end in FIG. 6), the opening of the orifice portion 53 becomes zero, and the bypass flow of the pressure oil from the supply pump 10 through the rotation speed sensitive orifice 5 is blocked. The flow level downstream of the metering orifice 12 is only the flow rate passing through the metering orifice 12, and is configured to be controlled to be constant, for example, Qm.

In the power steering apparatus of the second embodiment having the above-described structure, as shown in FIG. 7, when the rotational speed of the engine EG exceeds N1, the spool 51 moves and the opening of the orifice portion 53 is gradually reduced. The flow rate Qh of the pressure oil to the rotary valve 3 is gradually reduced, and when the flow rate exceeds N2, the opening degree of the orifice portion 53 becomes completely zero. Therefore, the flow rate Qm of only the flow rate passing through the measuring orifice 12 is controlled to be constant. Is done. The pressure-flow rate characteristics as shown in FIG.

When such a rotational speed sensitive control is performed and the handle HD is in the neutral position, the bypass valve 2 is operated to reduce the flow rate Qn as shown by the broken line in FIG. 7 as in the first embodiment. , But the handle HD
Is operated, the operation of the bypass valve 2 is stopped, and the operation returns to the above-described rotation speed sensitive characteristic.

The device of the second embodiment having the above-described operation is provided by the first device.
As in the embodiment, in addition to the effect of realizing energy saving by reducing the pressure loss and the energy loss in the entire apparatus, the rotation speed response characteristic of the flow rate is realized, so that the high speed stability of steering is improved.

The above-described embodiments have been described by way of example only, and the present invention is not limited to these embodiments. The technology of the present invention can be recognized by those skilled in the art from the description of the claims. Changes and additions are possible as long as they are not against the idea.

For example, the supply pump 10 is shown to be driven by an on-vehicle engine. However, the supply pump 10 can be driven by a motor, and a flow control valve is not required if it is electrically controlled at a constant speed.

Although the spool valve having a slit is shown as the bypass valve 2, the slit is not essential.
Bypass operation is possible even with different types of spool valves, rotary valves and other types of valves, as long as they have similar functions and effects.

Although an example of a rotary valve has been described as a direction switching valve, switching control of the supply direction of pressure oil is possible even with a different type of rotary valve, spool valve, or other type of servo valve. The present invention is applicable as long as it has the function and effect of (1).

In the second embodiment, an example is shown in which a rotational speed sensitive orifice is added. However, this orifice is not an essential requirement of the present invention, and other orifices having the same function and effect can be used. Applicable.

[Brief description of the drawings]

FIG. 1 is a hydraulic system diagram of a power steering device according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional view showing a rotary valve of the first embodiment.

FIG. 3 is a diagram illustrating a relationship between a flow rate and an engine speed of the first embodiment device.

FIG. 4 is a diagram showing pressure-flow characteristics of a flow control valve of the first embodiment device.

FIG. 5 is a hydraulic system diagram of the second embodiment device.

FIG. 6 is a longitudinal sectional view showing a flow control valve and a rotation speed sensitive control valve of the second embodiment.

FIG. 7 is a diagram showing the relationship between the flow rate and the engine speed of the second embodiment device.

FIG. 8 is a diagram showing pressure-flow characteristics of the flow control valve of the second embodiment.

FIG. 9 is a hydraulic diagram of a conventional device.

FIG. 10 is a diagram showing a relationship between a flow rate and an engine speed of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure oil supply part 2 Bypass valve 3 Rotary valve 4 Power cylinder 5 Revolution-sensitive orifice 10 Supply pump 11 Flow control valve 12 Metering orifice 13 Bypass passage 14 Control valve 15 Spring chamber 16, 26 Spring 20, 42 Cylinder 21, 51 Spool 23 Orifice 30 Gear Housing 32 Input Shaft 33 Output Shaft 34 Rack Shaft 35 Inner Valve 36 Outer Valve 37 Direction Switching Valve 3H High Pressure Hose 41 Piston

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-209656 (JP, A) JP-A-61-200061 (JP, A) JP-A-1-144172 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) B62D 5/07

Claims (2)

(57) [Claims] 1. A flow control valve having a spring chamber provided with a spring for controlling a flow rate of pressure oil discharged from a supply pump to be constant, and a handle based on a pressure of the pressure oil supplied from the flow control valve. When the pressure is neutral, the spring chamber of the flow control valve is
A bypass valve that lowers the level of pressure oil supplied from the flow control valve by communicating with it, a servo valve that controls the direction of supply of pressure oil from the flow control valve according to the steering direction, and a servo valve that controls And a power cylinder that is steered in a direction corresponding to a supply direction of the pressurized oil to be supplied. 2. A bypass passage connected to a low pressure side by a pressure and a spring force acting on a spring chamber in which a spring is disposed in order to maintain a constant longitudinal pressure of a measuring orifice disposed in a discharge passage of a supply pump. A flow control valve for supplying a controlled flow of hydraulic oil, and a spool moving in accordance with the pressure of the hydraulic oil supplied from the flow control valve. When the pressure of the pressure oil is low, a bypass valve that lowers the flow level of the pressure oil supplied from the flow control valve by communicating the spring chamber of the flow control valve with the low pressure side depending on the positional relationship of the spool, A servo valve for controlling a supply direction of pressure oil from the control valve according to a steering direction; and a power cylinder for steering in a direction corresponding to a supply direction of pressure oil controlled by the servo valve. War steering device.