JPS58149858A - Flow controller of power steering - Google Patents

Abstract

PURPOSE:To prevent change of a flow due to a steering load in a high revolution range, by applying pressures in the upstream of a plunger and in the downstream of a variable orifice to both ends of a spool. CONSTITUTION:A plunger 8 is displaced to a position, in which a difference between pressures in front and rear sides of a variable orifice 21 and tension of a spring 15 are balanced, here the orifice 21 decreases its opening in accordance with the displacement of the plunger 8, and its pressure difference relatively increases in accordance with a decrease of opening even if an orifice flow is equal. If pressure in the downstream of the orifice 21 increases, a pressure rise in a rear pressure chamber 9 due to this increase returns a spool 7 to decrease an opening of a bypass port 4 and increase pressure of a pump port 2 correspondingly to a load, in this way, the difference between front and rear pressures of the plunger 8 is not changed, and the opening of the orifice 21 can be equally held.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate control device for working fluid in a power steering ring.

In power steering, which reduces the burden on the driver by hydraulically assisting vehicle steering operations, the hydraulic assist force is reduced at high speeds because the turning resistance of the wheels decreases significantly at high speeds. Many products are designed to improve safety.

Since the pump that serves as the hydraulic pressure source is driven in synchronization with the engine rotation, the discharge flow rate also increases in the high rotation range, resulting in a large amount of hydraulic oil being supplied to the power steering hydraulic actuator. A control valve is provided to form a drooping bin type flow rate control device that reduces the supply flow rate as the rotational speed increases.

However, in this case, when the power steering load increases, the spool of the flow control valve displaces in response to this load pressure, and the position of the drooping bin changes, so the supply flow rate fluctuates depending on the load pressure. was there.

In order to deal with such problems, Japanese Patent Application Laid-Open No. 56-1041
In No. 86, it was proposed that the control spool that serves as a drooping bin is separated from the spool of the flow control valve so that the operation of the flow control valve does not affect the opening degree of the variable orifice by the control spool. ing.

However, in this case, a restriction passage that provides a pressure difference between the front and rear of the control spool is provided separately from the control spool, which complicates the structure for guiding this pressure difference, and the restriction passage is provided in the spool of the flow control valve. Since the downstream pressure acts on the spool, the responsiveness of the spool to changes in the flow rate of the pump port is low, and there is a problem in that the control of the bypass flow rate, in other words, the feedback control characteristics of the supply flow rate deteriorates.

The present invention was proposed in order to solve such problems.The present invention has been proposed to solve this problem by providing a variable flow rate control system between the pump port from the hydraulic pump and the supply port to the hydraulic actuator, in which the opening degree changes depending on the displacement of the plunger. While the orifice is provided, the pressure upstream of the plunger and the pressure downstream of the variable orifice are applied to both ends of the spool to release the excess flow rate, thereby preventing fluctuations in the flow rate due to the steering load in the high rotation range. The present invention provides a power steering flow rate control device that has a simple structure and high control accuracy.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, a body 1 of the control device includes a pump port 2 connected to the hydraulic pump discharge side, a supply port 3 connected to the hydraulic actuator side of the power steering via a switching valve (not shown), and a reservoir for storing surplus flow. A bypass port 4 for returning the body 1 to the side is formed, and these openings are respectively opened in the spool holes 5 of the body 1.

The spool hole 5 includes a spool 7 that functions as a flow control valve to control the amount of excess oil released, and a supply port 3.
Blungiers 8 for making the flow paths variable are provided so as to be freely slidable.

The spool 7 is pressed until it engages with the retaining ring 11 by the spring 10 of the back pressure chamber 9 to which the back pressure of the variable throttle is introduced, closing the bypass port 4. When the front pressure increases, spool 7
is pushed back and opens the bypass port 4, allowing some of the hydraulic oil to escape to the reservoir side.

On the other hand, the plunger 8 has a sleeve 12 with an open end formed on the plug 13 of the supply port 3 fitted into the spool hole 5.
It is inserted freely and slides freely.

The plunger 8 is formed into a cylindrical shape with a bottom, and its bottom 17 serves as a pressure receiving part for the pre-throttling pressure, and is pressed toward the pump port by a spring 15 until it comes into contact with a retaining ring 16.

An annular passage 14 communicating with the pump port side is formed on the outer periphery of the sleeve 12, and an orifice hole 20 connecting the annular passage 14 and the sleeve internal chamber 19 is formed in the sleeve 12. The degree changes as the plunger 8 is displaced, thereby forming a variable orifice (variable throttle) 21 for controlling the flow rate.

Note that the passage 22 guides the downstream pressure of the variable orifice 21 to the back pressure chamber 9 of the spool 7.

Next, the operation will be explained with reference to FIG. 2. When the flow rate fed into the bob port 2 is small, the hydraulic oil flows from the annular passage 14 through the orifice hole 20 to the internal chamber 19 and the supply port 3.

Then, when the supply flow rate of the pump port 2 increases and the differential pressure generated at the orifice hole 20 becomes greater than a certain value, the spool 7 moves back against the spring 10 and begins to open the bypass port 4.

Therefore, a part of the hydraulic oil in the pump port 2 is bypassed to the reservoir side, and the front and rear pressure in the orifice hole 20 is
will remain more or less constant.

Therefore, the flow rate to the supply port 3 is a substantially constant flow rate depending on the opening degree of the orifice hole 20 even if the pump rotation speed changes.

By the way, at this point, the plunger 8 is in the orifice hole 2.
Since the front and rear pressure difference due to zero does not overcome the setting force of the spring 15, it does not move, and the opening degree of the orifice hole 20 does not change.

As the pump rotation speed further increases and the flow rate increases, the supply port increases in proportion to the deflection force of the spring 10 of the spool 7, even though the bypass length increases by 1 m.
Since the flow rate to port 3 increases little by little, plunger 8
The pressure difference across the orifice hole 20 correspondingly increases, and eventually the plunger 8 is displaced while bending the spring 15, so that the plunger end partially closes the orifice hole 20.

As a result, the opening degree of the variable orifice 21 is reduced, and the flow rate flowing to the supply port 3 is reduced.

Even in this state, the spool 7 is displaced to roughly increase the bypass flow rate so as to keep the differential pressure across the variable orifice substantially constant.

Thereafter, the orifice hole 20 is adjusted according to the amount of displacement of the plunger 8.
Although the effective area of spool 7 decreases, in reality the spool 7
With constant differential pressure control, the spring load changes depending on the amount of deflection of the spring 10, so even if the variable orifice opening is constant, the amount of l supplied will gradually increase, so even if the variable orifice 21 is narrowed in this way ( (Of course, it depends on the method of throttling), but the supply flow rate becomes an almost constant minimum flow rate.

By the way, regarding the movement of the plunger 8 at this time, the plunger 8 is displaced until the pressure difference between the front and rear sides of the variable orifice 21 and the force acting on the spring 15 are balanced. Since the opening degree decreases with displacement, the pressure difference relatively increases as the opening degree decreases even if the orifice flow rate remains the same.

Therefore, the pressure that moves the plunger 8 increases when the variable orifice 21 starts to narrow down, and this differential pressure can be effectively used as a driving force for the plunger 8.
The opening degree of 1 can be sensitively increased or decreased.

On the other hand, if the pressure downstream of the variable orifice 21 increases due to load fluctuations on the supply port 3 side, the spool 7 is returned due to the associated pressure increase in the rear pressure chamber 9, and the opening degree of the bypass port 4 is reduced. The pressure at the pump port 2 is increased in accordance with the load -↓, but as a result, the differential pressure across the plunger 80 does not change, so the opening degree of the variable orifice 21 is kept the same, and the supply flow rate is changed from the conventional drooping. Like the bin method, you can prevent it from increasing.

That is, in the present invention, the spool 7 for constant differential pressure control and the metering orifice 21 are not integrated, and the variable orifice 21 can be independently controlled regardless of the bypass flow rate.

By the way, since the pump port pressure (front pressure) directly acts on the spool 7 for differential pressure control, the responsiveness to this pressure fluctuation is extremely good, and highly accurate pressure feedback control can be performed.

As described above, according to the present invention, the supply flow rate in the pump rotation range is reduced regardless of power steering load fluctuations, improving maneuverability. Since the port pressure is applied directly, the response is excellent, and because the differential pressure across the variable orifice is used to drive the plunger, it is possible to effectively magnify minute pressure differential changes to displace the plunger. This has the effect of providing control accuracy with high throttle response to changes in pump discharge amount.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the invention. FIG. 2 is a flow characteristic diagram of the present invention. 1...Body, 2...Pump port, 3...Supply port, 4...Bypass port, 7...Spool,
8...Plunger, 10.15...Spring, 1
2... Sleeve, 20... Orifice hole, 21...
・Variable orifice.

Claims (1)

[Claims] The oil discharged from the hydraulic pump is sent from the pump port through the throttle part to the supply port communicating with the hydraulic actuator, and the excess flow is returned through the spool that opens and closes the bypass port in response to the pressure before and after the throttle. In the power steering flow control device, a variable oil valve is installed in which a plunger is located between the pump port and the supply port and is freely slidable inside the sleeve, and the opening degree changes according to the displacement of the plunger. 1. A power steering flow rate control device, characterized in that it is formed on the sliding surface of the sleeve to guide the pressure of the pump port and the downstream pressure of the variable orifice to both ends of the plunger and spool.