JPH027743Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic oil flow rate control device for power steering.

In the case of power steering, which uses hydraulic pressure to power-assist the steering force, the turning resistance of the wheels decreases as the vehicle speed increases, so in order to correspondingly reduce the power assist, the flow rate of hydraulic oil is reduced. It's changing.

FIG. 1 shows a flow rate control device for this purpose, in which hydraulic oil from a hydraulic pump (not shown) flows into an inner hole 3 of a body 2 from a pump port 1, passes through an orifice hole 4, and enters an operating port 5. From there, it is supplied to a power steering actuator (not shown).

A spool valve 6 is slidably inserted into the inner hole 3, and the spool valve 6 moves to a position where the pressure difference between the front pressure chamber 7 and the rear pressure chamber 8 becomes equal to the acting force of the spring 9.

The front pressure chamber 7 is a chamber to which the pressure upstream of the orifice hole 4 acts, and the pressure downstream of the orifice hole 4 is introduced to the back pressure chamber 8 via a passage 10.

A drooping pin 11 protruding from the spool valve 6 is inserted into the orifice hole 4, and the effective area of the orifice hole 4 is changed depending on the position of the pin 11.

When the spool valve 6 moves backward against the spring 9, the suction port 12 opens, allowing a portion of the hydraulic fluid from the pump port 1 to escape to the suction side of the hydraulic pump.

The hydraulic pump is driven to rotate in synchronization with the engine, and the discharge amount increases as the engine speed increases.

In a region where the engine speed is low, the spool valve 6 is in the position shown in the figure, and all of the hydraulic fluid from the pump port 1 flows to the operating port 5 and is sent to the power steering actuator.

As the pump discharge rate increases as the engine speed increases, the pressure drop when passing through the orifice hole 4 gradually increases, and the spool valve 6 retreats to a position where this pressure difference is balanced with the strength of the spring 9. do. When the suction port 12 eventually begins to open as the spool valve 6 retreats, a portion of the pump discharge oil is transferred to the suction port 12.
It circulates from there to the pump side.

Therefore, the flow rate sent to the operating port 5 does not increase any further, and furthermore, as the spool valve 6 retreats, the shaft portion 1 of the drooping pin 11
When the enlarged diameter portion 11a reaches the orifice hole 4 from 1b, the orifice area begins to decrease, so the flow rate supplied to the operating port 5 begins to decrease.

Therefore, in the high engine speed range, the orifice hole 4 is narrowed down significantly, and as shown in FIG. 2, the flow rate supplied to the power steering actuator is significantly reduced.

In this way, control is performed such that the supply flow rate is increased in a relatively low engine speed range, and is decreased as the engine speed shifts from a medium to high engine speed range.

Generally, in the low engine speed range, the vehicle speed is low and the steering resistance is large, so a large power assist is required.On the other hand, in the high engine speed range, the vehicle speed increases and the steering resistance becomes very small. It is necessary to reduce power assist in order to ensure safety, and for these reasons, the supply flow rate is controlled as described above.

However, engine speed and vehicle speed are not always in an absolute proportional relationship; for example, when driving uphill in a low gear, the vehicle speed is low relative to the engine speed, and the supply flow rate must be reduced in such conditions. The handle becomes very heavy.

In other words, conventional devices cannot accurately sense vehicle speed. On the other hand, Tokugansho
No. 56-173207, which combines an engine speed-sensitive hydraulic pump with a vehicle speed-sensitive flow control mechanism,
A system has been proposed in which these switching operations are performed as necessary, but in this case, there are problems in that the device becomes complicated and selection of switching is troublesome.

The present invention was proposed to solve this problem.It detects the vehicle speed and prevents the drooping pin from narrowing down the engine in the low speed range even when the engine is running at high speed. It is an object of the present invention to provide a power steering flow rate control device that secures a large supply flow rate until rotation.

Hereinafter, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 3, the valve body 2 is provided with an electromagnetic solenoid 15.
The actuating rod 16 rests against the head of the drooping pin 11.

The electromagnetic solenoid 15 is controlled by a controller 18 that receives the output of a vehicle speed sensor 17 that detects the speed of the vehicle.
6 by a certain amount, and then remove the drooping pin 11.
Push back.

The drooping pin 11 differs from that shown in FIG. 1 in that in a low speed range where the amount of pressure applied by the actuating rod 16 is small, even if the pump rotation speed increases and the spool valve 6 opens the suction port 12 wide, the expanded diameter portion 11a remains in the orifice. The shaft portion 11b is made long so as not to narrow the hole 4.

The rest of the structure is the same as that in FIG. 1, so the same reference numerals are given and the operation will be explained next.

In a low vehicle speed range, the stroke amount of the electromagnetic solenoid 15 is minute, and the spool valve 6 is moved largely to the left.

Therefore, when the engine speed increases and the pump discharge flow rate increases, the spool valve 6 moves back according to the pressure difference between the front and rear of the orifice hole 4, and eventually opens the suction port 12 and transfers the flow to the operating port 5. prevent excessive increases in supply.

The spool valve 6 further changes as the rotational speed increases thereafter, but since only the shaft portion 11b of the drooping pin 11 is located in the orifice hole 4 and no throttling is performed, as shown in FIG. 4A, The supply flow rate does not decrease even in the high rotation speed range.

In other words, it is possible to prevent the power assist force from decreasing in the low speed and high rotation range.

On the other hand, in the medium and high speed range, the vehicle speed sensor 17
Based on the output of
1 to relatively retract the spool valve 6.

As a result, when the pump rotation speed increases and some of the hydraulic oil begins to be bypassed to the suction port 12 side, the flow rate increases as the rotation speed increases and the amount of displacement of the spool valve 6 increases. Accordingly, the enlarged diameter portion 11a of the drooping pin 11 comes to be located in the orifice hole 4, so that the supply flow rate is narrowed down and the supply flow rate in the high rotational speed range is reduced as shown in FIG. 4B.

Further, the above action is achieved when the spool valve 6 is located relatively to the right in the figure, but the positioning of the spool valve 6 is achieved by the actuation rod 16 of the electromagnetic solenoid 15 directly pressing the drooping pin 11. Therefore, the operational response in controlling the amount of supplied oil is extremely good, compared to, for example, a configuration in which the displacement of the spool valve 6 is controlled only depending on the oil pressure.

Therefore, in the high vehicle speed range, the steering wheel is prevented from becoming too light, as in the conventional case, and the steering stability is improved.

As described above, according to the present invention, the supply flow rate is secured in the low vehicle speed range, and the flow rate is reduced in accordance with the rise in engine speed in the high vehicle speed range, thereby eliminating the lack of power in the low speed and high rotation range. At the same time, it improves maneuverability in high-speed ranges, while also being extremely simple in structure and reducing costs.

In addition, in the present invention, the drooping pin is directly displaced by the actuating rod protruding from the electromagnetic solenoid, which has the advantage of simplifying the structure as described above and providing excellent actuation response. It will be done.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the conventional device, Figure 2 is its control characteristic diagram, Figure 3 is a sectional view of the present invention, and Figures 4A and B.
is its control characteristic diagram. 1... Pump port, 2... Body, 4... Orifice hole, 5... Operating port, 6... Spool valve, 7... Front pressure chamber, 8... Back pressure chamber, 11...
Drooping pin, 11a... Expansion portion, 11b...
... shaft portion, 12 ... suction port, 15 ... electromagnetic solenoid, 16 ... actuation rod, 17 ... vehicle speed sensor, 18 ... controller.

Claims (1)

[Scope of utility model registration request] In a power steering system in which hydraulic oil from an engine-driven hydraulic pump is sent to the power steering actuator depending on the steering direction, the hydraulic oil from the pump port is guided to the operating port via the orifice hole. ,
A spool valve is provided that opens and closes the suction port in response to the longitudinal pressure of the orifice hole, and a drooping pin that is inserted into the orifice hole and changes the effective area is protruded from the spool valve. An electromagnetic solenoid is provided that regulates the initial position of the drooping pin to at least two positions, a position where it is retracted from the orifice hole and a position where it has entered, based on the output, and when the drooping pin is displaced from the retracted position, the drooping pin is moved from the entry position when it is displaced from the retracted position. The initial position of this drooping pin is set to be a retracted position in a relatively low vehicle speed range and an approach position in a relatively high speed range. A power steering flow rate control device, characterized in that the power steering flow rate control device is configured to control the electromagnetic solenoid.