JPH027744Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a vehicle speed sensitive power steering device.

In power steering devices that use hydraulic pressure to power assist steering wheel operations, wheel turning resistance decreases as vehicle speed increases, so we have developed a vehicle speed-sensitive type that reduces the power assist force in response to this. system is proposed.

Figure 1 shows this, where 1 is the handle, 2
3 is the power steering section consisting of the power cylinder, switching valve, etc., 3 is the hydraulic oil reservoir,
4 is a hydraulic pump that is driven in synchronization with the engine rotation speed; 5 is a control valve that increases or decreases the hydraulic fluid supplied from the hydraulic pump 4 to the power steering unit 2 according to the vehicle speed; 6 is the opening degree of the control valve 5; This is a controller that controls based on the output of the vehicle speed sensor 7.

When the handle is operated, a switching valve (not shown) in the power steering section 2 is switched, and hydraulic oil from the hydraulic pump 4 is sent to the power cylinder of the power steering section 2, and this hydraulic pressure is used to control the wheels via the steering gear, linkage, etc. The direction is changed in accordance with the operating direction of the handle 1.

The steering resistance of the wheels reaches its maximum value when the vehicle is stationary, such as when the vehicle is stationary, and becomes extremely small when the vehicle is running at high speed. Therefore, the flow rate required by the power steering section 2 decreases as the vehicle speed increases.

Therefore, the control valve 5 reduces the opening degree as the vehicle speed increases based on the output of the vehicle speed sensor 7, and reduces the supply flow rate in the high speed range to prevent the steering wheel from becoming too light and improve maneuverability.

By the way, even if you control the supply flow rate in this way,
Steering load may change independently of vehicle speed,
For this reason, if the pressure of the hydraulic oil fluctuates, even if the opening degree of the control valve 5 is the same, the flow rate changes (the supply flow rate decreases when the load pressure increases). A flow rate control device 10 as shown in the figure is provided to perform pressure compensation.

That is, the pump discharge oil flows from the pump port 11 into the inner hole 13 of the valve body 12, and is sent to the control valve 5 from the operating port 15 via the orifice hole 14.

A spool valve 16 is slidably inserted into the inner hole 13, and the spool valve 16 is inserted into the orifice hole 1.
The pressure receiving end faces each of the front pressure chamber 17 and the rear pressure chamber 18 so as to respond to the differential pressure between the front pressure and the rear pressure 4.

A return spring 19 is interposed in the rear pressure chamber 18, and pressure on the downstream side of the orifice hole 14 is introduced through a passage 20.

A drooping pin 21 protruding from the spool valve 16 is inserted into the orifice hole 14, and the pin 2
The effective area of the orifice is changed depending on the position of 1.

When the spool valve 16 retreats to a certain value against the spring 19 due to the increase in the differential pressure, the suction port 22 opens and the pump port 1
A portion of the hydraulic oil from 1 is returned to the pump suction side.

Since the hydraulic pump 4 is driven in synchronization with the engine rotation, the discharge flow rate increases in proportion to the engine rotation speed.

In the region where the engine speed is low, the spool valve 16 is in the state shown in the figure, and the pump port 11 is in the state shown in the figure.
All of the hydraulic fluid flows to the working port 15.

When the pump discharge flow rate increases as the engine speed increases, the pressure difference when passing through the orifice hole 14 gradually increases, and the spool valve 16 is gradually pushed back against the spring 19, until a certain flow rate is reached. Suction port 22 begins to open.

Therefore, after this point, the flow rate on the working port 15 side does not increase, and the excess pump discharge oil flows back from the suction port 22 to the pump suction side.

In such a state, if the steering load changes, for example, the load pressure increases, this pressure increase is fed back to the operating port 15 side, and the pressure in the rear pressure chamber 18 of the spool valve 16 increases by that amount.

In conjunction with this, the spool valve 16 moves to reduce the opening degree of the suction port 22, increasing the pressure on the upstream side of the orifice hole 14. As a result, the supply pressure increases in proportion to the increase in the steering load pressure, and by keeping the differential pressure across the orifice hole 14 the same, the supply flow rate is prevented from decreasing (pressure compensation is performed). It is.

By the way, when the amount of displacement of the spool valve 16 exceeds a certain value when the pump discharge amount increases, the drooping pin 21 of the spool valve 16 moves from the previous shaft portion 21a with respect to the orifice hole 14.
The head 21b begins to be inserted, and begins to reduce the effective area of the orifice and reduce the flow rate.
In other words, the supply flow rate is reduced in the high engine rotation range where the pump rotation speed increases. Generally, when the pump rotational speed is high, it is often in a high-speed running range, and together with the control valve 5, the supply flow rate is reliably reduced in the high-speed and high-speed range, thereby increasing the stability of steering wheel operation.

However, when using the hydraulic pump 4 of this speed-sensitive flow rate control device, the supply flow rate decreases when the engine speed is high even in a low vehicle speed range (such as when climbing a winding slope in a low gear). The problem was that the power assist was insufficient and the steering wheel became heavy.

In response to this, the present applicant has proposed a device in Japanese Patent Application No. 173207/1983 that allows the functions of the vehicle speed-sensitive control valve and the rotation speed-sensitive hydraulic pump to be switched and used as needed. Although it has been proposed, the mechanism for switching is complex and only one of the functions can be obtained by switching, so high flow rate control accuracy by combining both is not required.

In order to solve these problems, this invention has developed a vehicle speed-sensitive hydraulic pump by not restricting the flow rate in the low-speed and high-speed range while retaining the pressure compensation function. It is an object of the present invention to provide a power steering device that further promotes highly accurate flow control characteristics based on a combination with a control valve.

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

As shown in FIGS. 3 and 4, an electromagnetic solenoid 25 is provided on the valve body 12 of the flow rate control device 10 of the hydraulic pump 4 as a rotation speed sensitive release means, and the operating rod 26 of the electromagnetic solenoid 25 is connected to a drooping pin. 21's head.

The electromagnetic solenoid 25 is simultaneously controlled by a controller 6 which generates a control signal for the control valve 5 from the output of the vehicle speed sensor 7.

That is, when the vehicle speed reaches a high speed range, the electromagnetic solenoid 25 pushes out the actuating rod 26 by a certain amount and pushes back the drooping pin 21.

In this case, the drooping pin 21 differs from that shown in FIG.
The shaft portion 21a is set to be long so that even if the suction port 22 is opened wide, the expanded diameter head portion 21b will not narrow the orifice hole 14.

With this configuration, the controller 6 hardly excites the electromagnetic solenoid 25 in the low-medium speed range, so the stroke of the actuating rod 26 is minute and the spool valve 16 moves largely to the left.

In this state, when the engine speed increases and the spool valve 16 retreats according to the differential pressure across the orifice hole 14, and eventually opens the suction port 22, the flow rate supplied to the operating port 15 becomes excessive. However, since only the shaft portion 21a of the drooping pin 21 is inserted into the orifice hole 14, the supply flow rate does not decrease even in a high rotation range, as shown in FIG. 5A.

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

On the other hand, in the high speed range, the actuating rod 26 of the electromagnetic solenoid 25 is pushed out by the controller 6 to push the drooping pin 21 back.

Therefore, in this state, when the pump rotation speed increases and the amount of displacement of the spool valve 16 increases, the enlarged diameter portion 21b of the drooping pin 21 is inserted into the orifice hole 14, and as before, the pump rotation speed increases and the displacement amount of the spool valve 16 increases. The supply flow rate is reduced as shown in Figure 5B to ensure high-speed maneuverability.

By the way, the pressure compensation function of the spool valve 16 is maintained in the same way in both the low-medium speed range and the high-speed range. Therefore, if the load pressure fluctuates, the spool valve 16 will be displaced and supplied accordingly. Since the pressure is increased or decreased, it is possible to prevent fluctuations in the supply flow rate at the same vehicle speed.

As described above, according to the present invention, a vehicle speed-sensitive control valve and a rotation-speed-sensitive hydraulic pump (flow control device) are combined, and the hydraulic pump is configured to release the throttle at high rotation speeds in the low and medium speed range. This makes it possible to reliably improve high-speed maneuverability by appropriately increasing the steering force in high-speed ranges without increasing the steering force in low-speed ranges.

Further, in the present invention, since the retraction amount of the drooping pin is directly regulated by the electromagnetic solenoid, the structure is simplified and excellent responsiveness is obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional device, Fig. 2 is a sectional view of a pump flow rate control device, Fig. 3 is a circuit diagram showing an embodiment of the present invention, Fig. 4 is a sectional view of a pump flow rate control device, and Fig. 5 is a sectional view of a pump flow rate control device. Figures A and B are also flow rate control characteristic diagrams. 2... Power steering section, 4... Hydraulic pump, 5... Control valve, 6... Controller, 7... Vehicle speed sensor, 10... Flow control device, 16... Spool valve, 21... Drooping pin, 25... Electromagnetic solenoid, 26... Operating rod.

Claims (1)

[Scope of utility model registration request] In power steering, hydraulic oil from an engine-driven hydraulic pump is sent to the power steering actuator depending on the steering direction, and a vehicle speed sensor detects the vehicle speed. A control valve that reduces the flow rate is provided, and a spool valve that guides the hydraulic oil from the pump port to the operating port via the orifice hole and opens and closes the suction port in response to the back and forth pressure of the orifice hole, and this spool. A flow control means including a drooping pin protruding from the valve and inserted into the orifice hole to change the effective area is provided, and the initial position of the drooping pin is retracted from the orifice hole based on the output of the vehicle speed sensor. A regulating electromagnetic solenoid is provided in at least two positions, ie, a retracted position and an advanced position, and the orifice hole effective area is reduced by a smaller amount when the drooping pin is displaced from the retracted position than when displaced from the advanced position. The electromagnetic solenoid is controlled so that the initial position of the drooping pin is set to a retracted position in a relatively low vehicle speed range and to an approach position in a relatively high speed range. Power steering device.