JPS5854280A - Pressure compensating type flow regulation valve - Google Patents

Abstract

PURPOSE:To improve refinement of flow regulation in the regulation valve, described at the heading, which is used for controlling steering power of a power steering device or for other purposes by lessening a hydraulic pressure which is applied to a spool of a pressure compensating part. CONSTITUTION:While fluid having passed through a pressure reducing passage 14 runs through a spacing 16 between a throat 12d and the internal face 11d of a guide hole, the fluid is inverted by the throat 12d while guided by the internal face 11d of the guide hole, and then comes against an angular land 12c to apply a right pressure to a spool 12. The pressure is reversed to the hydraulic pressure of the fluid which acts on the spool 12 while flowing through the pressure reducing passage 14, on account of which the hydraulic pressure which acts on the spool 12 may be lessened. As the result, the pressure compensating function of keeping the differential pressures before and behind a variable throttle 8 at specified values may be reliably performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a pressure compensating flow control valve used in a power steering power transmission system and the like.

Power steering and its steering force control device are generally the first
It is constructed as shown in the figure, and includes an engine-driven constant flow pump l, a power steering operating valve, a power cylinder ~x3, a working fluid supply path, and a working fluid return! A pressure compensator inserted into the bypass path 6 that short-circuits between the two? And variable aperture part! A pressure compensation type wave amount adjustment valve is provided.

The above elements l to j constitute a power steering system, and a constant flow rate QT of fluid discharged from the pump is passed through the valve 2 through the retreat path! is returned to the reservoir tank/θ which is integrated into the pump l. Here, when the steering wheel is operated 19, the valve responds to the furnace operation load, and the upstream side
That is, a pressure P1 is generated in the passageway, and this pressure is introduced into the room through the corresponding power cylinder J, and the power cylinder 1 is activated to power-assist the steering force transmission system in the steering direction, thereby providing light steering. Power steering is possible. By the way, the sweeping force control device gt composed of the above-mentioned 114 to 9,
Since the variable throttle part r is opened according to the vehicle speed via the servo motor, the pump discharge fluid is extracted by the amount IQ corresponding to the vehicle speed, and the fluid of 'n side view Qc=QT-Q is applied to the valve. -, and the steering force can be controlled to an appropriate value according to the vehicle speed. On the other hand, the difference ΔP e P2 + p between the front and rear pressures P2 and Ps of the pressure compensation section 2#-i variable throttle section ♂
It exists to keep s at a constant value, so that it does not change even when the amount of hydraulic oil drawn through the variable throttle part t changes due to positive pressure %, and functions to keep it at a value that corresponds to the opening degree of the variable throttle part l. The aim is to control the steering force with high precision.

For example, a pressure compensating flow rate regulating valve with 4 pins for such applications has its pressure compensating portion conventionally configured as shown in Figure 1.
- Slidably fitted, spool/- one end enlarged part l core a
The spring force of the spring 13 and the downstream pressure Ps1 of the variable restrictor l are applied to the right direction 1 in the figure! Apply a variable throttle to the other end land part /2b of the spool /2 and the enlarged end part /2a, and adjust the valve body /l.
Spool land guide hole //eL K annular #l //b
The discharge fluid from the constant flow pump l is placed in the mound-shaped decompression passage /* existing between the weft shoulder and the corner of the spool land /cob /, 2C. arrow 2
As shown in , the pressure is reduced from P1 to P2 by passing through it,
After that, the flow g is determined by the opening degree of the variable throttle s and rv.
The remaining fluid, which is drawn into the reservoir tank 10 by the FQ and whose flow rate has been adjusted in this way, can be supplied to the fluid operating equipment (the joint venture shown in FIG. 1) through the circuit.

In such a configuration, considering the steady balance equation of the force acting on the spool 7.2, k (Xl −X) s= #QV1a1111I+
A(P2-Ps) - (/1, where the left side is the spring force due to spring /J, and the first term on the right side is the fluid force %tlK
The second term represents the force due to the fluid pressure P2, 1) 5. From this equation, the differential pressure ΔP across the variable restrictor r becomes ΔP wax PI - Ps, and the first term on the right side of the above equation is a constant term. ,
The 1st term and 1@3 term on the right side of the above equation are variable terms, respectively.

The conventional pressure-compensated flow rate regulating valve adjusts the amount of fluid drawn into the variable restrictor r to the pump discharge pressure PI.
However, under other operating conditions, the above-mentioned variable As mentioned above, the mK term can be kept small and negligible, but it becomes a large value, and the differential pressure ΔP cannot be kept at a constant value due to the influence of these v number terms. This means that the differential pressure - This means that even if the variable throttle opening amount Q is the same as the amount of fluid withdrawn by the variable throttle part t, a cape #- occurs, making it difficult to obtain an accurate flow rate adjustment function. Figure 1 shows the type of malfunction that can occur in equipment that uses valves.
An example of a ring will now be described. First, Figure 1 shows the change characteristics of the fluid withdrawal amount Q and the compensation pressure (differential pressure) ΔP with respect to the change in the opening area of the variable throttle part 9r.As is clear from this characteristic diagram, the opening area of the variable throttle part ♂ Naturally, the fluid withdrawal amount Q increases as shown by Ql and Q2 as .
P is ΔP1. As shown by ΔP2, it cannot be maintained at a constant rate, and as the opening area of the variable diaphragm r increases, it decreases. Although this decrease is as low as ^P1 when the pressure P1 is low, As the pressure P1 increases, the size of the button increases as shown in ΔP2, and such a decrease in the differential pressure ΔP makes it impossible to make the fluid withdrawal amount Q correspond to the opening area of the variable throttle part l, and especially the variable throttle part/17) opening. Is there a constriction part where the fluid withdrawal amount Q is variable like Ql and Ql in the area where the area becomes large? There is a large downward deviation (below the corresponding value) from the linear characteristic corresponding to the opening WU product of O. This tendency also occurs when the pressure P1 is low (
This is more noticeable when the pressure P1 is higher (indicated by Ql) than in the case where the pressure P1 is higher (indicated by Ql).

In this way, due to one error, the fluid withdrawal amount Q can correspond to the opening area of the variable throttle section l, and if it becomes less than the corresponding value, the displacement amount of the spool etc. that constitutes the variable throttle section r and the fluid withdrawal amount The relationship with Q is no longer linear, and in order to correct this, the control circuit of the servo motor that drives the spool etc. to determine the opening area of the variable diaphragm 9 section r becomes complicated. If an error occurs in the amount of fluid withdrawn due to the pressure P1, the opening area of the variable relief part r may be kept at a constant value corresponding to the vehicle speed. If the change is good, the amount of fluid withdrawn Q will change (due to the change in pressure P1) even though the vehicle is running at the same speed and the steering force must be maintained at the same level. Fluid Φ toward the valve
changes, the steering force changes, and highly accurate steering force control becomes impossible. Here, considering the above error, the above (the right-hand side, second term, and The third term, X%v1, is obtained by applying Bernoulli's equation to the fluid flowing through the decompression passage/4tK, using the following equation: Substitute into equation (k) to find.

Examining the influence of the variable terms (error terms) in equation (1), that is, the first and third terms on the right-hand side, we find that as %q and (Pl-P2) increase, the wholesale value of the error term increases. It can be seen from the above equation (2) that a large error occurs in the differential pressure ΔPK, and in this case, the error due to the third term becomes dominantly large. This is the third method to reduce the error in the differential pressure ΔP and increase the flow rate adjustment accuracy of the pressure compensation type flow rate adjustment valve.
It is clear that the countermeasure for the term Σ is effective, and the measures K for this purpose are: ■ Increasing the area size, ■ Said -) In the equation, ρ
QV+(2)φ and (in the formula Q■φJkoρ(Pl-P2
) It is necessary to reduce the fluid force represented by To increase this, the most effective measure is ■.

On the other hand, if the differential pressure ΔP is set high, the influence of the error term is small, but when a pressure compensation type flow rate regulating valve is used in a steering force control device as shown in Fig. 1, this is also possible for the following reasons. In other words, when the amount of fluid withdrawn by the variable restrictor ♂ is zero, the pressure loss at the valve λ is generally -
The pressure loss is approximately cR2, but the larger the fluid withdrawal amount Q is, the smaller the pressure loss is. ∆P must be set small.When using conventional pressure compensation type flow rate adjustment valves for such applications, the accuracy of flow rate adjustment becomes increasingly poor due to the small set differential pressure P as described above. This has become even more remarkable since the pressure P1 of the power steering hydraulic system changes over a wide range and pressure compensation is required throughout its entire hydraulic range.

Based on the above points, the present invention reduces the fluid force applied to the spool K of the pressure compensator, thereby reducing the influence on the flow rate adjustment accuracy, and increasing the overall size.

It is an object of the present invention to provide a pressure-compensated flow rate Ill valve that is improved so that a highly accurate flow rate regulator can be achieved without increasing the compensation pressure.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 3 shows an embodiment of the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals.

In the present invention, the constriction part /Jd adjacent to the land corner part /20 of the spool 12 is formed into a conical shape whose diameter gradually increases as it goes away from the land corner part, and this constriction part 1AY
As for the r land 12bKtt, as shown in the example shown in the figure, the radius gradually expands as shown in the ξ angle /26, and the land corner part /-20
The conical constriction part d is integrated with the land l-b at the point where the diameter becomes the same as that of the conical constriction part l-b. A sharp step may be set between the small diameter end and the land corner lco0.

The inner peripheral surface of the spool land guide hole //a that surrounds the constricted part /J(1 with a gap between it) is //
As shown by d, at least a considerable length of the conical constriction part /S is inclined in the same direction as the conical constriction part in a portion facing the conical constriction part.

In the pressure compensation type flow rate regulating valve of the present invention, a part of the fluid from the constant flow pump passes through the pressure reducing passage/4t and then extracts the reservoir tank 10K through the variable throttle part t. By keeping the fluid at the set value, the flow rate adjustment function determined by the opening area of the variable throttle part ttV can be carried out in the same way as in the past.In the present invention, the fluid after passing through the pressure reducing passage 14tYr has a conical constriction. When passing through the gap /4 between part /λd and the inner peripheral surface of the tapered spool land guide hole //a and ゛, the conical neck part /J as shown by arrow a.
After being reversed from the IJK, the tapered spool land guide hole inner circumferential surface // is guided from the dK and the spool is re-routed from Maro.
2, more specifically, the land corner / 20f (collides with the spool and does not exert a force to the right in the figure. This force is caused by the flow of fluid passing through the decompression passage / 4t to the left on the spool / JK in the figure). It is applied in the opposite direction to the physical force, reducing or canceling it. Therefore, the fluid force acting on the spool/- becomes smaller overall or becomes zero, and as a result, the error term in the above equation (-) can be made small, and the pressure compensation function that keeps the differential pressure across the variable throttle part r at the set value can be performed with high precision, and the flow rate adjustment function that depends on this can be performed with high precision. The compensation type flow rate adjustment valve has the shape described above on the inner peripheral surface of the spool land guide hole surrounding the constriction part /j and the groove of the spool /λ, and the pressure reduction passage /4t
Since the fluid after passing through K exerts a force on the spool saw in the direction of opening the vacuum connection/da, the fluid force in the direction of closing the vacuum passage that the fluid passing through is applied to the spool 12 as described above. It can be reduced or canceled out by the force, and the error in the flow rate adjustment function that conventionally occurred due to the fluid force can be almost eliminated, without increasing the overall size or increasing the differential pressure across the variable throttle part l. It is possible to perform a highly accurate flow rate adjustment function.

Note that in the above example, the fluid from the butterfly pump / flows into the annular groove // b through a single boat, and then flows into the vacuum passage / (
As shown in the Chikuri diagram (al and d), there is an annular groove//b 17) Several boats (tit in the illustrated example) opening at the bottom of the boat/7. /♂ are arranged at equal intervals in the circumferential direction, and the pump /♂ is provided through these boats.
By allowing the fluid from to flow into the annular groove //b, the force exerted by this inflow fluid in the radial direction of the spool land /2b becomes uniform over the entire circumference.

Spool/, 2 Y! ``It does not twist and can reduce the frictional force between it and the valve body/l, reducing the hysteresis that occurs when the spool/2 moves, and further improving the accuracy of flow rate adjustment.''

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a power steering system with a steering force control device showing an application example of a pressure-compensated flow regulating valve, Fig. 1 is a vertical side view showing a conventional pressure-compensated flow regulating valve, and Fig. 3 is a diagram of the present invention. ll1tlf indicating the pressure compensated flow rate lil valve
T side view, Fig. 7 (al is a vertical sectional side view similar to Fig. 11 to 3 showing another example of the flow rate regulating valve of the present invention. 1 is a sectional view, and FIG. 5 is a diagram showing the action characteristics of the conventional flow rate-valve control shown in FIG. , /θ...Reservoir tank, /I...Valve body, //&,...Spool land guide hole, //b...
Thyroid groove, //C・=N m s tia...Inner peripheral surface of tapered spool land guide hole, 12...Spool, /λa...Miner end, /Jb...Spool land, /2o ...Land corner, /2d...Conical constriction, /J...Spring, /G...Wave pressure passage, /! ...
Fluid operating device connection circuit, /6... gap, /7. ///
...Fluid inflow boat.

Claims (1)

[Claims] 1. Comprising a valve body and a spool slidably fitted to the valve body, a constant flow pump is installed in the pressure reducing passage between the land corner of the spool and the shoulder set in the stool land guide hole of the valve body. After passing the discharged fluid from the spool, a predetermined amount is extracted through the variable throttle part P, and the remaining discharged fluid is supplied to the fluid operating equipment from the upstream side of the pressure reduction passage, and the opening area of the pressure reduction passage is increased by moving the spool. The pressure compensation type wave amount adjusting valve is designed to maintain a constant differential pressure across the variable restrictor by adjusting the pressure. The spool land guide hole has a conical shape with an @ mark, and the inner peripheral surface of the spool land guide hole surrounding the conical constriction with a gap therebetween is tapered in the same direction as the conical constriction. Pressure compensated wave amount adjustment valve.