JPS58152666A - Flow rate controller for power steering - Google Patents

Abstract

PURPOSE:To elevate the response by arranging a fixed orifice in parallel with a variable orifice made up of a through hole of a piston and a fixed drooping pin to apply a variable orifice downstream pressure to a spool. CONSTITUTION:When the flow rate to a pump port 2 is limited, the total flow moves to a supply port 3. A differential pressure in a fixed orifice through hole 20 exceeds a specified value with increase in the supply flow rate, a spool 7 begins to open a bypass port 4 against a spring 10 so that the pressure is kept roughly constant before and after the fixed and variable orifices 23 and 21 to ensure the supply of a roughly constant flow rate. As the flow rate increases with a further rise in the revolutions of a pump, the supply flow rate increases in proportion to a deflection force of a spring 10 and a piston body 8 displaces with a high pressure difference working thereon against a spring 15 so that a taper section of the drooping pin 17 will moves into the through hole 20 to make the supply flow rate the roughly constant minimum level by reducing the opening of the variable orifice 21. Thus, the response of a variable choking can be elevated with the fixed orifice.

Description

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

φ The power steering system uses hydraulic assist to operate both steering wheels and reduces the burden on the driver. Many of them are designed to improve steering stability by reducing the amount of fuel.

The pump that serves as the hydraulic pressure source is driven in synchronization with the engine rotation, so the discharge flow increases in the high rotation range, and more hydraulic oil is supplied to the power steering hydraulic actuator. In order to prevent this, a flow control valve is provided, and a trusing bottle type flow rate control device is constructed which reduces the supply flow rate as the rotational speed increases.

However, in this case, when the power steering load increases, the spool of the C-]t, l-control valve is displaced in response to this load pressure, and the position of the drooping bin changes, so the supply flow rate changes to the load pressure. It may vary depending on.

In order to deal with this problem, Japanese Patent Application Laid-open No. B61041
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 back 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 flow control pulp. Since the downstream pressure of
There was a problem in that the quantity feedback control characteristics deteriorated.

The present invention was proposed in order to solve such problems, and a piston body is freely slidably interposed between a pump boat from a hydraulic pump and a supply boat to a hydraulic actuator. A fixed drooping bottle is inserted into the through hole of the piston body to form a variable flow rate υJI [I variable orifice 1 whose opening degree changes depending on the displacement of the piston body, and a fixed orifice is provided in series with this. It has a simple structure that allows the pressure of the flow and the pressure downstream of the variable orifice to act on both ends of the spool that controls the release of excess flow to prevent fluctuations in flow due to steering load in the high rotation range. The present invention also provides a power steering flow rate control device with high control accuracy.

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

In the embodiment shown in FIG. 1, the body 1 of the control device includes a pump boat 12 connected to the discharge side of the hydraulic pump, a supply boat 3 connected to the hydraulic actuator side of the power steering via a switching valve (not shown), and a surplus boat 3 connected to the hydraulic actuator side of the power steering. A bypass port 4 is formed to return the flow rate to the reservoir side.
They each open into a spool hole 5 of the body 1.

The spool hole 5 has a spool 7 that controls the release amount of excess oil as a flow control valve, and a supply boat 3.
A piston body 8 that makes the flow path variable is provided so as to be freely slidable.

The spool 7 is pushed until it engages with the stopper 14 by the spring 10 of the back pressure chamber 9 to which the high pressure of the variable throttle is introduced, thereby closing the bypass port 4. However, when the front pressure of the throttle applied to the left end of the spool increases , the spool 7 is pushed back to open the bypass port 4, allowing some of the hydraulic oil to escape to the reservoir side.

On the other hand, the piston body 8 is slidably inserted into a sleeve (cylindrical portion) 12 formed on the plug 13 of the supply boat 3 fitted into the spool hole 5 .

The piston body 8 is formed into a cylindrical shape, and the distance W! A through hole 20 is provided in the center of the pump 11, and the pump port 11 is pushed toward the pump port by a spring 15 until it comes into contact with a stopper 14 that is locked to a retaining ring 16.

The end of the stopper 14 is connected to the head 1 through the taper.
．． A drooping bottle 17 with a diameter of 7A is integrally provided, and this drooping bottle 17 enters and exits a through hole 20 connecting the pump boat 3 and the sleeve internal chamber 19 to change the opening degree of the orifice. , constitutes a variable orifice (variable aperture) 21.

The stopper 14 is attached to the sleeve 12 as shown in the upper part 2, and a fixed orifice 23 is formed therein, forming two stages of orifices in series with the variable orifice 21. Further, a spool 7 for adjusting the bypass flow rate is brought into contact with the opposite surface of the stopper 14, and the upstream pressure of the variable throttle is applied to the left end of the spool 7.

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. When the flow rate fed into the bob boat 2 is small, the entire amount of hydraulic oil flows lightly through the internal chamber 19 from the fixed orifice 23 and the through hole 20 to the supply boat 3.

Then, when the supply flow rate of the pump boat 2 increases and the differential pressure generated in the fixed orifice passage 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 portion of the hydraulic oil in the pump port 2 is bypassed to the reservoir side, and the front and rear pressures of the fixed orifice 23 and the variable orifice 21 are kept approximately constant.

Therefore, even if the pump rotation speed changes, the flow rate to the supply port 3 can be maintained between the fixed orifice 23 and the variable orifice 21.
The flow is almost constant depending on the opening degree of the valve.

By the way, at this point, the piston body 8 does not move because the pressure difference between the front and back due to the variable orifice 21 does not overcome the setting force of the spring 15, and the opening degree of the through hole 20 does not change.

Then, as the pump rotation speed further increases and the flow rate increases, the flow to the supply boat 3 increases little by little in proportion to the deflection force of the spring 10 of the snor lure, even though the bypass flow increases. Therefore, the pressure difference between the front and rear of the variable orifice 21 applied to the piston body 8 increases accordingly, and the piston body 8 is eventually displaced while bending the spring 15, and the tapered portion of the drooping bottle 17 is inserted into the through hole 20. inserted.

As a result, the opening degree of the variable orifice 21 is rapidly reduced, and the flow opening to the supply boat 3 is reduced.

Thereafter, the effective area of the variable orifice 21 decreases according to the displacement of the piston body 8, but in reality, the constant differential pressure control by the spool 7 changes the spring load depending on the amount of deflection of the spring 10. Even if the variable orifice opening is constant, the supply flow ■ will gradually increase, so even if the variable orifice 21 is narrowed down in this way (of course it depends on how it is narrowed), the supply flow rate will be an almost constant minimum flow rate. It is.

The total differential pressure ΔP generated by the fixed orifice 23 and the variable orifice 21 is the sum of the differential pressure ΔP of the fixed orifice 23 and the differential pressure ΔP2 of the variable orifice 21 (ΔP−ΔP1
+ΔP2).

As shown in FIG. 3, in order to obtain the differential pressure ΔP, both orifices 2 are initially set so that, for example, 8P, =P.
By setting the initial opening degrees of 3 and 21, the variation width PW2 of the differential pressure ΔP2 with respect to the pump rotation speed can be made larger than the variation width PW of the total differential pressure ΔP.

After the variable orifice 21 is calibrated, the change in the differential pressure ΔP with respect to the change in flow rate rises rapidly, whereas the differential pressure ΔP of the fixed orifice 23 whose opening degree does not change sharply.
tends to decrease rather because the restriction of its trailing edge becomes stronger, so that the range of change in the differential pressure ΔP can be made larger than the range of change in the total differential pressure ΔP.

Therefore, compared to the case where the fixed orifice 23 is not provided and only the variable orifice 21 is used and the piston body 8 is driven by this differential pressure (corresponding to ΔP), the two orifices 23 and 21 are used as in the present invention. By driving the piston body 8 with a differential pressure (ΔP,) having a large variation range in the variable orifice 21, a larger displacement can be achieved in response to a change in flow rate, and the position of the piston body 8 can be controlled accordingly. can be done easily and accurately.

By the way, the piston body 8 moves to a position where the longitudinal pressure of the variable orifice 21 and the acting force of the spring 15 are balanced, but since the variable orifice 21 decreases with the displacement of the piston body 8, the longitudinal pressure difference between the two Even if the orifice passage flow remains the same, it increases relatively as the degree of opening decreases.

Therefore, the pressure that moves the piston body 8 increases as the variable orifice 21 begins to constrict.In other words, the differential pressure can be effectively used as a driving force for the piston body 8, and in combination with the above, the opening degree of the variable orifice 21 is slightly reduced. It becomes possible to increase or decrease the flow rate sensitively to changes in flow rate.

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 pressure increase in the rear pressure chamber 9 due to this, and the opening degree of the bypass port 4 is reduced. , the pressure in the pump port 2 is increased in accordance with the load, but even if the spool 7 is displaced, the opening degree of the variable orifice 21 remains the same, so the supply flow rate remains the same as in the conventional drooping pin method. can be prevented 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 boat pressure (front pressure) directly acts on the spool 7 for differential pressure control, the responsiveness to this pressure fluctuation is extremely good, and a good pressure feedback control of 11 degrees can be performed.

In the second embodiment shown in FIG. 2, a stopper 14 having a fixed orifice 23 is disposed inside a sleeve 12, and a drooping pin 17 is used to change the surface structure of a through hole 20 as the piston body 8 is displaced. A spool 7 is brought into contact with the tip.

In this case, the drooping bin 17 is arranged so that the area of the through hole 20 decreases as the piston body 8 is pushed in.
The head 17B is formed to have a small diameter. It is clear that control is performed in this case as well in substantially the same manner as in the above embodiment.

As described above, according to the present invention, the supply flow rate in the 1^ rotation range of the cylinder is reduced regardless of power steering load fluctuations to improve steering stability, while the spool that controls the bypass flow rate is Since the pressure of the pump boat is applied directly, the response is excellent. In addition, a variable orifice is provided in series with the fixed orifice, and the piston body is driven by the front and rear pressure of the variable A refill, so that the piston body is displaced by effectively magnifying minute changes in differential pressure caused by slight changes in the flow layer. This has the effect of significantly increasing the responsiveness of the variable throttle to increases in pump discharge and the degree of freedom in control.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the present invention. FIG. 2 is a sectional view of the second embodiment. FIG. 3 is a flow rate and pressure characteristic diagram of the present invention. DESCRIPTION OF SYMBOLS 1... Body, 2... Pump port, 3... Supply port 1-14... Bypass port, 7... Spool, 8... Piston body, 10.15... Spring,
12... Sleeve, 14... Stopper, 17...
Drooping bin, 20...Through hole, 21...Variable orifice, 23...Fixed 4 ref. Patent applicant Kayaba Kogyo Co., Ltd.

Claims (1)

[Claims] The oil discharged from the hydraulic pump is sent to the supply port that communicates with the hydraulic actuator through the pump port gap, and the surplus flow is connected to a spool that opens and closes the bypass port 1 in response to the fluid force before and after the throttle. In the power steering flow control device, a piston body is slidably inserted between the pump port and the supply port, and a fixed drooping bin is provided in the through hole in the piston body. A variable A orifice whose opening degree changes with the displacement of the piston body is formed, and a fixed orifice is provided in series with this variable orifice, while the pressure at the pump port and the downstream pressure of the variable orifice are controlled by - A power steering flow rate l1l device characterized in that the flow is guided to both ends of a power steering wheel.