JPH0147347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering flow control device that reduces power assist as vehicle speed increases.

Power steering, which reduces the burden on the driver by hydraulically assisting vehicle steering operations, reduces hydraulic assist at high speeds to improve steering stability, as the turning resistance of the wheels decreases significantly at high speeds. Many of them are intended to improve sexual performance.

The one shown in Fig. 1 is a so-called drooping pin type flow control device, and has a valve body 1.
A pump port 2 that connects to the discharge side of the hydraulic pump P, a supply port 3 that connects to the hydraulic actuator PS of the power steering, and a bypass port 4 that returns surplus flow to the tank T side are connected to the spool hole 5, respectively. It is open to

A spool 6 is freely slidable in the spool hole 5 and functions as a flow control valve to control the release amount of excess oil. It is inserted therethrough to form a variable flow rate orifice 10.

The spool 6 is pressed until it engages with the retaining ring 13 by the spring 12 of the after pressure chamber 11 to which the after pressure of the throttle of the variable orifice 10 is guided through the passage 14, thereby closing the bypass port 4.
When the front pressure of the throttle applied to the left end of the spool increases, the spool 6 is pushed back, the bypass port 4 is opened, and a portion of the hydraulic oil is returned to the tank T. The hydraulic pump is driven in synchronization with engine rotation, and the flow rate increases as the rotation speed increases.

Therefore, when the flow rate from the pump port 2 is low, the hydraulic oil flows through the variable orifice 10 (through hole 9).
The entire amount flows to the supply port 3 through the pump port 2, but when the flow rate of the pump port 2 increases and the differential pressure generated at the variable orifice 10 becomes larger than a certain level, the spool 6 retreats against the spring 12, and the bypass port Start opening 4. A part of the hydraulic oil from the pump port 2 is bypassed to the tank side, and the front and rear pressure of the variable orifice 10 is kept almost constant.
Since the effective area of the variable orifice 10 does not change while the variable orifice 10 is located, the flow rate to the supply port 3 remains almost constant even if the pump rotation speed changes (see FIG. 2).

Next, as the pump rotational speed increases further, the spool 6 moves to increase the bypass flow rate, and the head 7B of the drooping pin 7 comes to come into contact with the through hole 9, the effective area of the variable orifice 10 suddenly decreases.

As a result, the flow rate to the supply port 3 is greatly reduced, reducing the amount of operation supplied to the power steering actuator in the pump high rotation speed range, and making the steering wheel heavier to ensure steering stability. In this way, the hydraulic assist is increased in the low engine speed range, while the hydraulic assist is decreased in the high engine speed range.

However, if the supply flow rate is controlled only as a function of the engine speed in this way, it may not match the actual steering load during driving.

For example, when driving at high speeds with the transmission in 1st and 2nd gears, such as when driving up a winding slope, the vehicle speed is low relative to the rotational speed and the switching resistance is large. Otherwise, the supply flow rate will be reduced, the handle will become excessively heavy, and
When the gear position is in 5th gear, etc., the vehicle speed will be high even if the engine speed is not very high, and there will be a region where the supply flow rate will not decrease even though power assist is almost unnecessary, making it difficult to match the two. It was becoming difficult.

The present invention was proposed in order to solve this problem, and the partition wall formed with the through hole of the variable orifice is configured to be slidable, and the partition wall is moved depending on the gear position of the transmission. An object of the present invention is to provide a power steering flow rate control device that reduces the orifice throttle rate at low speed gear positions such as 5th gear and increases the throttle rate at high speed gear positions such as 5th gear.

Embodiments of the present invention will be described below with reference to the drawings, in which the same parts as in FIG. 1 are designated by the same reference numerals.

As shown in FIG. 3, the partition wall 20 has a through hole 9 into which the drooping pin 7 is inserted.
It is connected to a cylindrical portion 22 that connects to one actuating rod.

A port 23 is formed on the circumferential surface of the cylindrical portion 22.
Maintains constant communication with supply port 3. Cylinder part 2
Solenoid 2 is pressed by return spring 26 to a position where it engages with retaining ring 25, but solenoid 2
As the excitation current of No. 1 increases, it is moved to the left in the figure.

The solenoid 21 is operated by an excitation current from a control circuit 27, and a signal is inputted to the control circuit 27 from means 28 for detecting the gear position of the transmission, and the gear position is sequentially changed from the first gear to the second, third, and so on. The solenoid excitation current value is increased as the current changes.

FIG. 4 shows this configuration as a hydraulic circuit diagram, and the operation will be explained next.

When the transmission gear position is in the first speed, the solenoid 21 is not excited via the control circuit 27, and the movable cylinder portion 22 is inserted by the return spring 26 to a position where it engages with the retaining ring 25.

In this state, drooping pin 7 of spool 6
In this case, the head 7B largely penetrates through the through hole 9 of the partition wall 20, resulting in a large amount of wrap. Therefore, even if the flow rate from the pump port 2 increases and the spool 6 moves to the right to open the bypass port 4, the drooping pin 7 will still be connected to the rod 7A.
is located near the partition wall 20 and does not reduce the effective area of the variable orifice 10.

Therefore, when the vehicle is traveling in the first gear position, even if the pump rotational speed increases, the supply flow rate is not significantly reduced, and it is possible to reliably prevent insufficient power assist, such as when traveling up a winding slope.

On the other hand, when the gear position is switched to a high speed position such as fifth speed, the control circuit 27 maximizes the excitation current of the solenoid 21 in response to a signal from the gear position detection means 28.

As a result, the cylindrical portion 22 is pulled to the left against the return spring 26, and the initial position of the drooping pin 7 to the head 7B relative to the partition wall 20 is approached.

When the spool 6 begins to open the bypass port 4 due to an increase in the flow rate from the pump port 2, the through hole 9 is narrowed down by the drooping pin 7 with a short stroke thereafter, reducing the flow rate supplied to the power steering actuator. reduce

In this way, even if the engine speed is not very high, when the vehicle is in fifth gear, where the vehicle speed is high, the flow rate is quickly reduced to ensure high-speed maneuverability.

In addition, when the gear position is from 2nd to 4th speed, the position of the partition wall 20 changes stepwise in the middle of the above, so the supply amount of hydraulic oil for power assist can be controlled almost accurately in accordance with the vehicle speed. (See Figure 5).

As described above, according to the present invention, since the flow rate is controlled by a function of the engine rotation speed and the gear position,
It is possible to prevent the flow rate from decreasing in the low-speed, high-speed range, and to reliably reduce the flow rate in the high-speed range, and has the effect of ensuring high-speed maneuverability while exerting a predetermined power assist when necessary.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a flow characteristic diagram thereof. FIG. 3 is a sectional view showing an embodiment of the present invention, FIG. 4 is a hydraulic circuit diagram thereof, and FIG. 5 is a flow characteristic diagram of the present invention. 1... Body, 2... Pump port, 3... Supply port, 4... Bypass port, 6... Spool, 7... Drooping pin, 7A... Rod,
7B... Head, 9... Through hole, 20... Partition wall, 2
DESCRIPTION OF SYMBOLS 1... Solenoid, 22... Cylindrical part, 26... Return spring, 27... Control circuit, 28... Gear position detection means.

Claims (1)

[Claims] 1. A bypass that sends discharged oil from a hydraulic pump that rotates synchronously with the engine from the pump port through a throttle part to a supply port that communicates with a hydraulic actuator, and opens and closes excess flow through a spool that responds to the pressure before and after the throttle. In a power steering flow control device in which a variable throttle is formed by freely inserting a drooping pin protruding from a spool into a throttle part while returning from a port, a partition wall having a through hole forming the throttle part is used. A flow control device for power steering, characterized in that displacement is performed via a solenoid operated by a signal from a gear position detector.