JPH037549B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a power steering device that uses hydraulic pressure to reduce the steering force of a vehicle, and more specifically, the present invention relates to a power steering device that uses hydraulic pressure to reduce the steering force of a vehicle. The present invention relates to a speed-sensitive power steering device that stops power assist by restricting the movement of a control valve.

(Prior art and its problems) Power steering devices, such as power steering devices for automobiles, are generally connected to the wheels (steering mechanism) through a control valve that switches based on input rotation from the steering wheel. The steering wheel operation force is reduced by selectively supplying pressure oil to the output drive section.

By the way, as the running speed of the vehicle increases, the resistance force generated between the wheels and the road surface when operating the steering wheel becomes smaller, and the pump oil pressure has a property of increasing in proportion to the engine rotation speed. There was a problem in that the power assist force for steering wheel operation sometimes became excessive, impairing the steering stability of the steering wheel.

For this reason, in recent power steering devices, as the traveling speed of the vehicle or the rotational speed of the engine increases, the hydraulic pressure applied to the output drive section is reduced to reduce the steering force.

The present invention provides such a speed-sensitive power steering device, but in the present invention, the spool-type control valve that switches the supply of pressure oil to the output drive section is restrained at a neutral position during high-speed running. By cutting off the supply of pressurized oil to the output drive unit, power assist for steering wheel operations is stopped during high-speed driving, and the purpose is to improve high-speed stability.

(Means for Solving the Problems) For this purpose, the present invention includes a spool-type control valve that switches based on the input rotation from the handle, and provides pressure oil to the output drive unit connected to the wheels via the control valve. In a power steering device that selectively supplies power, a rod having a large diameter portion in the middle is connected to one end of the spool of the control valve, and a rod is connected to both sides of the large diameter portion of the rod in the axial direction. Defines a reaction oil chamber with a larger inner diameter than the large diameter part,
Each of the two reaction oil chambers is provided with an annular valve seat through which the rod passes, and a spring that presses the valve seat against the end face of the large diameter portion to urge the spool to a neutral position. A passage is formed between the large diameter portion and its sliding hole to communicate the reaction oil chambers with each other, and the valve seat is in close contact with the end surface of the reaction chamber around the large diameter portion of the rod at the spool neutral position. a circuit that is formed so as to block the passage and communicate the reaction oil chambers with each other independently of the passage, and a solenoid valve that closes the circuit when the speed of the vehicle or engine is above a predetermined value. Equipped with.

(Function) In the above configuration, when the spool is in the neutral position, the valve seats of both reaction force oil chambers receive the tension of the spring to position the spool in the neutral position, and at the same time, the reaction force oil chamber around the large diameter portion of the rod It is in close contact with the end face and blocks the passage connecting each reaction oil chamber. Therefore, each reaction oil chamber is in a state where it can communicate only through the electromagnetic valve, and when the electromagnetic valve is closed in this state, each reaction oil chamber becomes in an oil lock state. Therefore, when the electromagnetic valve is closed during high-speed operation, the switching operation of the spool and the resulting hydraulic assisting action are blocked, and the steering force becomes moderately heavy.

(Example) Examples of the present invention will be described below based on the drawings. The drawing shows one embodiment of the present invention, and is an example in which the present invention is applied to a rack-and-pinion type power steering device.

This rack and pinion type power steering device is
The pinion shaft 34, which engages with a rack connected to the steering arm of the wheel via a tie rod (not shown) and rotates together with the steering handle, is connected to the rack (not shown) perpendicularly to the pinion shaft 34 through an elongated hole in the direction of the arrow. The spool-type control valve 3 is disposed in a direction perpendicular to the pinion shaft 34, and is supported so as to be able to move in parallel by a predetermined distance along the axis (extending to The spool 12 is switched by a pin 36a of a drive lever 36 that is aligned with the sliding direction of the spool 12 and swings around a fulcrum 35 of the main body of the device.

Two annular grooves 14 and 15 are formed on the inner surface of the main body valve hole 10 in which the spool 12 is slidably housed. Each of the annular grooves 14 and 15 forms an operating port that communicates with two opposing pressure chambers of a power cylinder (not shown), and cooperates with an annular groove of the spool 12 to be described later to move the spool 12 to the switching position. It has a function of supplying hydraulic pressure to one of the pressure chambers and opening the other pressure chamber to the tank 21 accordingly.

Further, three annular grooves 16 to 18 are formed on the outer peripheral surface of the spool 12. The annular groove 17 in the center serves as a pump port into which pressure oil from a hydraulic pump (not shown) is introduced through a passage 19, and when the spool 12 is in the neutral position as shown in the figure, it serves as the annular groove 14 as the operating port. It communicates with both of the 15. On the other hand, the left and right annular grooves 16
and 18 function as tank ports, respectively, and when the spool 12 is in the neutral position, the left annular groove 16 connects with the annular groove 14 and the right annular groove 1.
8 communicates with the annular groove 15. However, the spool 12 is formed with a bore 13 that communicates both the annular grooves 16 and 18 with each other, so that the left annular groove 16 is also connected to the tank via a passage 20 that opens to the right annular groove 18. 21.

Although the above configuration is similar to the known device, the present invention further includes: when the vehicle or engine speed (hereinafter simply referred to as "speed") increases;
Means are provided to hold the spool 12 in a neutral position so that it cannot be switched.

Specifically, a large diameter portion 37a is formed in the middle portion of the rod 37 connected to one end of the spool 12, and its outer diameter and width are adjusted to match the valve hole large diameter portion 10a.
It is formed to be slightly smaller than the inner diameter and slightly smaller than the width of the small diameter part (sliding hole) 10b formed in the middle, and the large diameter part 37a of the rod 37 and the valve hole small diameter part 10b form a large diameter part. Two reaction oil chambers 23 and 24 having an inner diameter larger than that of 37a are defined.

Inside each of the reaction oil chambers 23 and 24, an annular valve seat 25 whose inner diameter is slightly smaller than the large diameter portion 37a of the rod is housed so that the rod 37 is inserted therethrough. Each valve seat 25 is biased by a spring 26 so as to be pressed against the adjacent end surfaces of both reaction force oil chambers 23 and 24 in the neutral state. A groove-shaped passage 31 is formed in the axial direction between the sliding surface of the small diameter portion 10b of the valve hole and the large diameter portion 37a of the rod, and when the valve seat 25 is separated from the end face of the small diameter portion 10b, In other words, when it is not neutral, this passage 3
1, the left and right reaction oil chambers 23 and 24 communicate with each other.

The width of the rod large diameter portion 37a is made slightly shorter than the valve hole small diameter portion 10b in order to ensure that the flat valve seat 25 is in close contact with the peripheral end surface of the valve hole small diameter portion 10b in the neutral state. However, when the valve seat 25 has a shape that protrudes toward the end surface, the width of the rod large diameter portion 37a may be the same as or slightly larger than the valve hole small diameter portion 10b. Further, in this embodiment, a seal ring 10c is provided around the valve hole 10b in order to improve the sealing performance when the valve seat 25 is in close contact with the valve seat 25.

On the other hand, a circuit 27 that communicates with each other is connected to the reaction oil chambers 23 and 24 separately from the passage 31, and an electromagnetic valve 28 that opens and closes according to commands from the control device 30 is interposed in the middle of the circuit 27. . Control device 30
comprises, for example, a comparator that compares the signal from the speed sensor 29 with a set value and outputs a drive signal for the electromagnetic valve 28, and therefore drives the electromagnetic valve 28 in the closing direction as long as the speed is above the set value.

The electromagnetic valve 28 consists of a valve 28a and an electromagnetic solenoid 28b, and a passage orthogonal to the valve 28 is formed, one both ends of which are connected to the reaction oil chamber 23 via parts 27a and 27b of the circuit 27, respectively. , 24. Also, one of the other passages is connected to the annular groove 16 on the left side of the spool 12, and the inner cavity 1 to the left of the spool 12.
3, communicates with the tank 21 via the annular groove 18 and the passage 20 on the right side, and an electromagnetic solenoid 28 on the other side.
An on-off valve 28c driven by b is slidably housed. This solenoid valve 28 is normally open and communicates the reaction oil chambers 23 and 24 with the circuit 27 to open the tank 21, but when the solenoid 28b is actuated by the output signal of the control device 30, the on/off valve is opened. 28c is pushed out to close the circuit 27.

Next, the overall operation of the above configuration will be explained.

First, to explain the normal power steering action when the speed is below a predetermined value, when the steering wheel is operated to rotate the pinion shaft 34 in either direction, the resistance of the rack connected to the steering link is large. Therefore, the pinion shaft 34 is displaced approximately radially along the rack in this direction of rotation by the amount allowed by the long hole, as shown by the arrow.

At this time, the drive lever 36 engages with the pinion shaft 34 and swings around the fulcrum 35, displacing the spool 12 in the same direction as the pinion shaft 34. On the other hand, the reaction oil chamber 2 in the direction of displacement of the spool 12
3 or 24 is in communication with the tank 21 via the circuit 27a or 27b and the electromagnetic valve 28, the displacement of the spool 12 cannot be prevented, and power assist is performed based on this.

For example, if the reaction oil chamber 24 is in communication with the tank 21 via the circuit 27b and the electromagnetic valve 28 at this time, the spool 12 contracts the oil chamber 24 and is freely displaced to the right. Then, the pressure oil from the pump, which had been flowing back to the tank 21 via the passage 19 (pump port), the annular grooves 14 to 18 and the passage 20, is switched by the right movement of the spool 12 and flows back to the annular groove 17, 15 into one pressure chamber of a power cylinder (not shown). At this time, the other pressure chamber of the power cylinder communicates with the passage 20 via the annular grooves 14, 16, and 18 and becomes the low pressure side, so the power cylinder generates an assist force that urges the wheel in the steering direction. become. Furthermore, when the steering wheel is turned in the opposite direction, the spool 12 moves to the left, and the power cylinder generates an assist force to turn the wheel in the opposite direction. In this way, the steering force is reduced in low speed ranges where the ground resistance of the wheels is large.

On the other hand, when the speed increases and exceeds a predetermined value, the electromagnetic solenoid 28b drives the on-off valve 28c in the distal direction based on a command from the control device 30, that is, the valve closes and the dual reaction oil chamber 23 , 24, the rod 37 and spool 12 are in an oil lock state at the neutral position. That is, the displacement of the spool 12 in the axial direction is restrained, and thereby the movement of the pinion shaft 34 in the radial direction is restrained via the drive lever 36.

In this way, the switching operation of the control valve 3 is prevented at high speeds, and the spool 1
While the oil lock condition 2 continues, a manual operation condition is established in which no hydraulic assist force is applied to the steering wheel operation. As a result, the steering force does not become unnecessarily light during high-speed driving, and a stable steering feel can be obtained.

By the way, when the spool 12 of the control valve 3 is displaced in any direction from the neutral position, the reaction hydraulic pressures 23 and 24 are in communication with each other via the passage 31, so that when the handle is operated, Even if the electromagnetic valve 28 closes after exceeding a predetermined speed, the spool 12 will not be oil-locked until it returns to the neutral position.

Note that the speed at which the spool 12 should be oil-locked can be determined as appropriate depending on the specifications of the vehicle and engine, but the amount of oil from the pump, which is the oil pressure source for the power steering system, can be determined as the speed. If a drooping pin type flow rate control valve is provided, which decreases the flow rate as the engine rises, it goes without saying that the setting is such that the oil locks in a speed range where the discharge flow rate decreases sufficiently. Also,
Although the above embodiment is an example of application to a rack-and-pinion power steering device, the present invention is not limited to this.
Needless to say, the present invention is applicable to other types of power steering devices as long as they have a spool type control valve.

(Effects of the Invention) As explained above, according to the present invention, after the traveling speed of the vehicle or the rotational speed of the engine increases above a certain level, the spool of the control valve is oil-locked in the neutral position to prevent pressure oil from flowing to the power cylinder. By stopping the inflow, the hydraulic assist for steering wheel operation is suppressed, so that the steering wheel operating force can be appropriately increased during high-speed driving to create a stable steering feeling.

Furthermore, since only one electromagnetic valve is required for oil locking the reaction oil chamber, the structure can be simplified.

Furthermore, in the present invention, since the oil locking means consisting of a reaction oil chamber and the like is integrated at one end of the spool, the means does not require a major change in the configuration and dimensions of the switching valve, and therefore the device It is possible to make it compact and easy to mount on a vehicle, and there is also the advantage that only the oil lock means can be integrated into a unit for rationalization.

[Brief explanation of the drawing]

The drawing is a sectional view showing an embodiment of the present invention. 3... Control valve, 10... Valve hole, 10b
... Valve hole small diameter part, 11 ... Sleeve, 12 ...
...Spool, 13...Spool lumen, 23, 24
...Reaction oil chamber, 25...Valve seat, 26...
Spring, 27...Circuit, 28...Solenoid valve, 28c...Opening/closing valve, 30...Control device, 31
... Passage, 34 ... Pinion shaft, 36 ... Drive lever, 37 ... Rod, 37a ... Rod large diameter part.

Claims (1)

[Claims] 1. A power steering device comprising a spool-type control valve that switches and operates based on input rotation from a steering wheel, and selectively supplies pressurized oil to an output drive unit connected to wheels via the control valve,
A rod having a large diameter section in the middle is connected to one end of the spool of the control valve, and a reaction oil chamber having an inner diameter larger than the large diameter section is defined on both sides of the large diameter section of the rod in the axial direction. Each of the two reaction oil chambers is provided with an annular valve seat through which the rod passes, and a spring that presses the valve seat against the end face of the large diameter portion to urge the spool to a neutral position. , a passage is formed between the large diameter portion and its sliding hole that communicates both the reaction oil chambers with each other, and the valve seat is attached to the end surface of the reaction chamber around the large diameter portion of the rod at the spool neutral position. a circuit that is formed so as to close together to block the passageway and communicate the reaction oil chambers with each other independently of the passageway; and a circuit that closes the circuit when the speed of the vehicle or engine is equal to or higher than a predetermined value. A power steering device characterized by comprising a solenoid valve.