JPH023749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure fluid supply device that selectively supplies pressure fluid discharged from a plurality of pumps to fluid equipment, and particularly relates to a flow rate control valve that recirculates excess pressure fluid to a tank side. .

For example, in a power steering device mounted on an automobile to reduce the steering force of a driver, a pump that is a source of oil pressure generation is usually rotationally driven by the automobile's engine. The amount of hydraulic oil discharged from this pump increases or decreases in proportion to changes in engine speed. Therefore, such a pump is required to have a capacity that can supply a sufficient flow rate to fluid equipment such as the power steering device even when the engine is in a low rotation range, that is, when the pump discharge amount is small.

However, if you set the pump capacity like this,
In the high speed range of the engine, an unnecessarily large amount of flow is supplied to the power steering device, resulting in a lot of waste.
In addition, the horsepower consumption of the engine for the pump increases, which is not preferable in terms of energy saving measures. In particular, in recent years there has been a call for improved fuel efficiency of automobile engines, and it is desired to minimize the horsepower consumption of the above-mentioned power steering device pump.

For this purpose, we use two small-capacity pumps and a flow path switching valve, and when the discharge volume of each pump is small, they are combined and supplied, and when the discharge volume of each pump becomes large, one pump is used. In addition to supplying only one pressure oil to the power steering device, the other pump is connected to the tank side to recirculate the pressure oil, and the horsepower required to drive this pump is minimized to reduce horsepower consumption. Pressure fluid supply devices that achieve this have been proposed in the past.

However, the above-mentioned device is configured to switch the flow path based on the discharge amount of each pump, that is, the engine rotation speed, and it is difficult to reduce the horsepower consumption when the car is running at high speed, that is, in the high engine speed range. However, energy loss is unavoidable in the low engine speed range, and there is still room for improvement.

In other words, in the above-mentioned power steering system, the amount of pressure oil supplied becomes a problem when a high load is applied and high output is required, that is, during steering operations, and at other times, such as when stopping. When driving in the middle or straight ahead, the amount of pressure oil supplied may be small even if the engine is in a low rotation range. In particular, automobiles are most often driven in urban areas represented by, for example, a 10-mode driving pattern, and it is necessary to reduce horsepower consumption during such low-speed driving.

To this end, it is best to adopt a flow path switching mechanism that senses and operates when a load is applied to the power steering device, but the problem with such a mechanism is that the engine rotates at high speed and Even when the discharge amount from one pump is sufficient, the flow path is switched and the horsepower consumption increases.

In addition, a structure that electrically detects the vehicle's running speed and uses this detection signal to switch the flow path is being considered, but vehicle speed is not necessarily proportional to the engine rotation speed, that is, the pump discharge amount. Therefore, it is difficult to say that the horsepower consumption can be effectively reduced, and there is a lot of waste. In particular, in overloaded trucks, the engine often reaches a high speed range even when traveling at low speeds, which is a problem, and electric detection means and solenoid valves operated by this are a problem. There are structural problems when using it.

Furthermore, in configuring a control unit that can achieve the energy-saving effect described above, there is a problem in that out of the pressure oil discharged from each pump, there is no need to use pressure oil that is unnecessary for the operation of the power steering system. The purpose of the present invention is to improve the operational reliability of a flow rate control valve that recirculates water to the tank side, and to further improve the energy saving effect. In particular, in this type of flow control valve, it is desirable to have a structure that allows excess pressure oil out of the pressure oil from each pump to be smoothly and appropriately returned to the tank side without creating flow path resistance. In addition, consideration must be given to the smooth operation of the valve and the workability of each part.

Furthermore, in the pressurized fluid supply device used in the above-mentioned power steering device, the amount of pressure fluid supplied in the high rotation range of the engine poses a problem in terms of running stability of the automobile. In other words, when a car is running at high speed, if the steering wheel is too light, the driver feels uneasy.To eliminate this, it is possible to reduce the amount of pressure oil supplied to some extent. It is necessary to provide a certain so-called drooping mechanism. Such a drooping mechanism is generally operated using the above-mentioned flow control valve, and there is a growing demand for the operational reliability of this flow control valve.

The present invention was made in view of these circumstances, and includes a pressure-sensing flow path switching valve that operates according to the magnitude of the load on the fluid equipment side, and a pressure-sensing flow path switching valve that operates according to the discharge amount from each pump. The structure is configured to switch the flow path by skillfully combining the flow control valve with a flow path switching function to recirculate the pressure fluid to the tank side, and the return flow path in the flow control valve is connected to the main A small-diameter passage hole drilled by machining that defines the operating stroke of the spool for connecting the passage to the tank side is mutually independent from the small-diameter passage hole that defines the operating stroke of the spool, and the valve hole partially overlaps at the same location in the axial direction. The simple structure of the flow control valve, which consists of a combination of at least one channel hole with a large flow channel cross-sectional area, greatly improves the operational reliability of the flow control valve while taking into account its workability. Moreover, even when a drooping mechanism is attached, the effect can be further demonstrated.Furthermore, it is possible to make adjustments between each pump and fluid equipment, and maintain an appropriate amount of supply from the pump to the fluid equipment. The present invention provides a pressurized fluid supply device that can reduce the horsepower consumption of a pump without affecting the operation of fluid equipment, and can further improve the energy saving effect.

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 1 shows an embodiment of a pressure fluid supply device according to the present invention, and in this embodiment, a case where the pressure fluid supply device is applied to a power steering device for an automobile will be explained.

In the figure, reference numerals 1 and 2 are first and second pumps that discharge pressure oil separately, both of which are rotationally driven by an engine (not shown), and which transfer hydraulic oil in a tank 3 to power through a flow path switching mechanism 4. It plays the role of circulating supply to the steering device 5. Note that these pumps 1 and 2 do not necessarily have to be constructed separately, and may be constructed integrally with a common casing and pump drive shaft, but in this case, the capacity of the first pump 1 is the same as that of the first pump 1. It is preferable that the pump is smaller than the pump 2 of No. 2. Further, in the figure, 1a and 2a are suction side pipes of each pump 1 and 2, 1b and 2b are discharge side pipes, and 3a is a tank side pipe connected to the suction side pipes 1a and 2a, Furthermore, 5a is a pressure oil supply pipe connecting between the flow path switching mechanism 4 and the power steering device 5, and 5b is a recirculation pipe to the tank 3.

In addition, the first and second pumps 1 and 2 described above
The flow path switching mechanism 4 for selectively supplying the pressure oil discharged from the power steering device 5 to the power steering device 5 is composed of various members described in detail below.

That is, the reference numeral 10 in the figure indicates the first pump 1.
The main passage 11 is a sub passage through which the pressure oil from the second pump 2 is guided, and between the main passage 10 and the sub passage 11, the power A pressure-sensing flow path switching valve 12 is interposed, which operates by sensing a change in the pressure of the pressure oil in the main passage 10 depending on the magnitude of the load on the steering device 5.

This flow path switching valve 12 is connected to the main passage 1
A spool valve 13 is slidably supported in a valve hole 12a with one end open on the 0 side, and this spool valve 13 is normally biased by a spring 14 to the main passage 10 side (left side in the figure). The sub passage 11 located at the axial center of the valve hole 12a is separated from the main passage 10. In this state, sub passage 1
1 is an annular groove 1 on the outer periphery of the central part of the spool valve 13
The reflux passage 1 is arranged in parallel with the sub-passage 11 via 3a.
5, and further communicates with the tank 3 via a reflux pipe 15a.

The flow path switching valve 12 also has a check valve 16 at the end of the spool valve 13 on the main passage 10 side.
3 is connected to the sub passage 11 through the through hole 13b and the annular groove 13c on the outer periphery thereof. Of course, this flow path switching valve 1
2, the sub passage 11 and the reflux passage 15 are separated by the spool valve 13. In this state, the check valve 16 is opened by the pressure oil from the second pump 2 and guides it into the main passage 10 as long as the flow rate control valve having a flow path switching function, which will be described later, is in an inactive state. It plays the role of flowing and merging the pressure oil from the first pump 1. (See FIG. 2A) Note that the low pressure chamber 17 in which the spring 14 of this flow path switching valve 12 is disposed
The pressure on the tank 3 side is led through the small hole 13d, and the main passage 10 is connected to the opposite high pressure chamber 18 side.
When the fluid pressure on the main passage 10 side increases due to an increase in the load on the power steering device 5, the spool valve 13 senses this and moves it to the right side in the figure. Moving.

Further, on the downstream side of the main passage 10 in parallel with the flow passage switching valve 12, there is provided a passage switching function that senses and operates when the flow rate flowing in the main passage 10 exceeds a predetermined value. A flow control valve 20 is provided. This flow control valve 2
0 is the power that, when the discharge amount from the first pump 1 or the discharge amount from the second pump 2 joins it, a part of it is released to the tank 3 side if the flow rate is more than a predetermined amount. It has substantially the same configuration as a conventionally known flow control valve that plays the role of maintaining the amount of supply to the steering device 5 below a certain amount.

That is, it includes a spool valve 21 slidably supported in a valve hole 20a whose one end is open to the main passage 10, and an orifice 22 provided in the middle of the main passage 10. The high pressure chamber 23 defined by the above structure is located upstream of the orifice 22 through a passage 24, and the low pressure chamber 25 is located downstream of the orifice 22 through a passage 26 having an orifice 26a for preventing oscillation of the spool valve 21. It is connected. The spool valve 21 is always located on the high pressure chamber 23 side (left side in the figure) by a spring 27 provided in the low pressure chamber 25, and in this state, it is connected to the main passage 10 and the tank via the high pressure chamber 23 and the passage 24. Connection with the reflux path 28 communicating with the third side via the pipe line 28a is blocked. In addition, 29 in the figure is a relief valve attached to the spool valve 21. Further, the spring 27 on the flow control valve 20 side has a weaker biasing force than the spring 14 on the first switching valve 12 side.

Here, in the flow rate control valve 20 configured as described above, the noteworthy point is that the bypass passage 30 communicating with the flow path switching valve 12
Pressure oil from the second pump 2 is guided to this bypass passage 30 via the sub passage 11. Normally, that is, when the flow control valve is not in operation, the bypass passage 30
is open to the annular groove 21a of the spool valve 21 on the low pressure chamber 25 side, and is separated from the reflux path 28. Therefore, in this state, the second
Pressure oil from the pump 2 is guided to the tank 3 or the main passage 10 according to the flow switching operation of the flow switching valve 12.

On the other hand, when this flow control valve 20 operates,
As shown in FIG. 2B, part of the pressure oil flowing through the main passage 10 is returned to the tank 3 side, and the bypass passage 30 opens into the annular groove 21b on the high pressure chamber 23 side of the spool valve 21. It communicates with the reflux path 28 via. At this time, if the flow path switching valve 12 is in the non-operating state, the sub-path 11 is in communication with the tank 3 through the reflux paths 15 and 28, and the pressure oil from the second pump 2 is directed to the tank 3 side. Naturally, it returns and there is no problem, but on the other hand, when the flow path switching valve 12 is operated, the sub passage 11 is connected to the main passage 10 via the through hole 13b provided with the check valve 16 and the annular groove 13c. Tank 3 via the bypass passage 30, further the annular groove 21b on the second switching valve 20 side, and the reflux passage 28.
connected to the side. Therefore, in this state, the check valve 16 is not opened to the pressure difference on both sides thereof, and as a result, the pressure oil from the second pump 2 in the sub passage 11 is returned via these two valves 12 and 20. Road 28
Pass through and return to the tank 3 side. This state is shown in Figure 2C.
is shown.

Then, the flow path switching mechanism 4 configured in this way
The operation will be explained below in terms of the relationship between the discharge amount of each pump 1, 2, that is, the rotational speed of the engine, and the power steering device 5. First, FIG. This shows a case where the steering device 5 is in an inoperative state, that is, no load is applied to the power steering device 5 and the fluid pressure in the main passage 10 is low. In this state, both valves 12, 20
As a result, the pressure oil from the first pump 1 is supplied to the power steering device 5 through the main passage 10, but the second pump 2 is supplied to the power steering device 5 through the sub passage 11 and the return passage 15. connected to tank 3 via
Pressure oil circulates through the second pump 2 and tank 3, and is maintained in an unloaded state. This is because even if the supply amount of pressure oil is small, it does not affect the power steering device 5 at all. The flow rate characteristics in this state are shown by the solid line a in Figure 3, and the horsepower consumption due to this is shown by the broken line a in Figure 4, which is about half that of the conventional one (see the two-dot chain line shown by b in the same figure). That's fine.

In addition, P ₁ in Fig. 3 is the discharge amount of the first pump,
P ₂ is the discharge amount of the second pump, and P ₁ +P ₂ is a straight line showing the relationship between the total discharge amount and the rotation speed.

Furthermore, when the load increases due to the operation of the power steering device 5 from the low speed and low pressure state shown in FIG. 1, and the state becomes low speed and high pressure, the flow path switching valve 12 is activated as shown in FIG. 2A. Second pump 2, tank 3
The second pump 2 is connected to the main passage 10 via the check valve 16. Therefore, the second
The pressure oil from the pump 2 is supplied to the first pump in the main passage 10.
The pressure oil from the pump 1 is joined with the power steering device 5.
is supplied to generate the necessary steering operation assistance force,
There is no problem in operation. The flow rate characteristics when this load is large are shown by the solid line b in Figure 3, and the horsepower consumption is shown by the solid line c as shown in Figure 4, which is the same as in the conventional system (see the dashed line d in the same figure). .
Of course, in this state, the horsepower consumption cannot be reduced.

In addition, in a high-speed, low-pressure state where the pump discharge amount increases to a predetermined amount or more as the rotation speed increases and the power steering device 5 is inactive, the flow rate control valve 20 increases as shown in FIG. 2B. is activated to release a portion of the pressure oil from the first pump 1 flowing through the main passage 10 to the tank 3 side via the reflux path 28, thereby controlling the supply amount to the power steering device 5 at a constant level. At this time, the flow path switching valve 12 is in an inactive state, and the pressure oil from the second pump 2 returns to the tank 3 via the sub-path 11 and the reflux path 15. Of course, a part of it returns to the tank 3 via the reflux path 28 which communicates with the sub-path 11 via the flow rate control valve 20. The flow rate characteristic in this state is shown by the solid line a or b in Figure 3.
The horsepower consumption is shown by a continuous solid line c at the corner points X and Y, and the horsepower consumption is sufficiently small as shown by the broken line a in FIG.

Furthermore, during this high-speed rotation, when the power steering device 5 is activated and becomes in a high pressure state, the flow path switching valve 12 is also activated together with the flow rate control valve 20, as shown in FIG. The sub passage 11 through which the pressure oil from the pump 2 is guided is connected to the reflux passage 28 via the bypass passage 30 and the flow rate control valve 20, as described above, and communicates with the tank 3 side. Then, this pressure oil returns to the tank 3 side without opening the check valve 16, and on the other hand, a part of the pressure oil from the first pump 1 in the main passage 10 is also returned to the reflux passage 28 by this flow rate control valve 20. As a result, a certain amount of pressure oil is supplied to the power steering device 5. The flow rate characteristics at this time are shown by the solid line c in Figure 3, and the horsepower consumption is shown by the 4th line c.
In the figure, it is indicated by a solid line e that is continuous with the solid line c, and this may be about half that of the conventional one (dotted chain line d in the figure).

In addition, in Fig. 2 A to C, P ₁ is the first
_P2 indicates the second pump 2, T indicates the tank 3, and PS indicates the power steering device 5, respectively.

The energy saving effect of the device of this embodiment described above is also apparent from the relationship diagram between horsepower consumption and pump discharge pressure shown in FIG.

First, if the pump rotation speed is in the low speed rotation range,
As shown by the solid line a, in a no-load state, the horsepower consumption is about half that of the conventional system (see the two-dot chain line b in the figure), and becomes the same as the load increases.

In addition, in the high speed rotation range, as shown by the solid line c,
The horsepower consumption is approximately half that of the conventional system (see the dashed line d in the figure). This is because, at high speeds, regardless of the magnitude of the load, only the first pump 1 is involved in supplying hydraulic pressure to the power steering device 5, and the second pump 2 is unrelated.

Now, according to the present invention, as described above, part of the pressure oil from the first pump 1 in the main passage 10 and the pressure oil from the second pump 2 are transferred to the tank 3 at high speed and high pressure. The operation stroke of the spool valve 21 for connecting the main passage 10 to the tank 3 side at its valve hole 20a (Fig. 9A)
A small-diameter passage hole (small-diameter passage 28a) bored by machining to define the middle dimension L) and a small-diameter passage hole (small-diameter passage 28a) that is mutually independent and at the same location in the axial direction of the valve hole 20a (the part shown in the same figure). It is characterized in that it is constructed in combination with at least one flow passage hole (for example, the cast hole 28b) having a large flow passage cross-sectional area that overlaps the portion indicated by the middle dimension l.

That is, conventionally, as this type of reflux path, generally a hole 31 having a circular cross section as shown in FIG.
is used, but such a circular reflux path 3
When 1 is applied to the above-mentioned device, the following problems occur. To briefly explain this using FIGS. 7A and 7B, the spool valve 21 of the flow rate control valve 20 is moved inside the valve hole 20a due to the increase in the amount of pressurized oil in the main passage 10 as the pump rotation speed increases. It moves to the right side in the figure and returns a part of the pressure oil in the main passage 10 to the tank 3 side via the reflux passage 31. As the amount of pressurized oil increases, the spool valve 21
moves to the right one after another, and the flow area between the main passage 10, that is, the first pump 1 and the reflux passage 31, increases one after another. Pressure oil return path 31
The opening area for the second
Flow path resistance increases on the pump 2 side, resulting in energy loss.

Therefore, in order to eliminate such a problem, a shape that alleviates the increase in flow path resistance of the pressure oil flow path from the second pump 2 when the spool valve 21 moves to the right is created. you need to choose,
As shown in FIG. 8A, two machined circular holes 32a and 32b are continuous in the axial direction of the valve hole 20a, and as shown in FIG.
A cast hole 33 having a substantially rectangular shape extending in the axial direction of a is conceivable. However, in the former case, while the overflow timing accuracy (indicated by dimension L in the figure), which is a problem with this type of return passage 31, can be obtained, when drilling the second hole, it is not necessary to cut a part of the hole. The cutting force becomes unstable in the circumferential direction due to the presence of parts, resulting in interrupted cutting, which is a problem in terms of machinability, and is preferable from the viewpoint of tool life and hole dimensional accuracy. isn't it. On the other hand, in the latter case, although the molding process is easy and the shape can be made into any desired shape, there is a problem in that the above-mentioned dimensional accuracy cannot be obtained. Also,
If the diameter of the reflux passage 34 is enlarged as shown in FIG. 3C, the spool valve 21 cannot operate properly, causing problems in terms of operability.

Therefore, according to this embodiment, the reflux path 28
A small-diameter passage 28a machined to obtain overflow timing accuracy and an overlapping portion (dimension l in the figure) independent of this and at the same location in the axial direction of the valve hole 20a.
) A cast hole 28 having a substantially L-shape
It consists of b. Note that 35 in the figure is a ball that closes the hole drilled during machining of the small diameter passage 28a.

According to such a configuration, the reflux path 28
It is possible to obtain timing accuracy during valve operation with the small diameter passage 28a that constitutes the second pump 2, and the presence of the cast hole 28b, which can be easily formed by machining, allows the flow path from the second pump 2 to be narrowed by the valve operation. , it is possible to eliminate the problems caused by increased flow path resistance, ensure a sufficient opening area, and achieve an energy saving effect. This is the 10th
This will be clear from the characteristic curve of the overflow passage opening area with respect to the valve displacement shown by the solid line a in the figure. In addition, the broken line b in the same figure shows the case of a general circular passage, and the thin line c in the same figure shows the case of a combined passage of large and small diameter holes, respectively.

In particular, according to this embodiment, except for the small-diameter passage 28a, which requires timing accuracy, the cast holes 28b are formed easily and inexpensively, and precision is not required, and a free shape can be obtained. That's a big advantage.

However, the present invention is not limited to the return passage 28 formed by the combination of the small-diameter passage 28a and the cast hole 28b that are machined as described above; for example, modifications as shown in FIGS. 11 and 12 are possible. It will be done.

The embodiment shown in FIG. 11 shows a case where a return flow path 36 consisting of a small diameter passage 36a and a large diameter passage 36b, which are drilled from opposite directions with a drill or the like, is formed in the valve hole 20a, and a part of the return flow path 36 is They are formed so as to overlap in the axial direction of the valve hole 20a, and timing accuracy is obtained on the small diameter passage 36a side. In such a configuration, each passage 36a, 36b
Since these are independent of each other, no problems arise in terms of workability.

Further, in the embodiment shown in FIG. 12, the small diameter passage 3
7a and the large-diameter passage 37b are formed to be slightly shifted in the circumferential direction and axial direction with respect to the valve hole 20a, and even in this case, it is easy to achieve the same effect as described above. be understood.

FIG. 13 shows another embodiment of the pressure fluid supply device according to the present invention.
Portions that are the same as or correspond to those in the figures are given the same numbers, and detailed explanation thereof will be omitted. In addition, in the figure, P ₁ is the first pump 1, P ₂ is the second pump 2,
T indicates a tank 3, and PS indicates a power steering device 5 as a fluid device.

Now, the difference in this embodiment is that the flow control valve 20 is provided with a drooping mechanism. That is, the orifice 22 provided in the middle of the main passage 10 for supplying pressure oil from the first pump 1 to the power steering device 5 opens on the low pressure chamber 27 side within the valve hole 20a of the flow control valve 20. And this main passage 1
0 is configured to pass through the valve hole 20a via a stepped annular groove 40 formed on the low pressure chamber 27 side of the spool valve 21 within the valve hole 20a. Then, by moving the spool valve 21 to the left side in the figure due to the operation of the flow control valve 20, the orifice 22 in the annular groove large-diameter portion 40a becomes a variable throttle, and the supply amount of pressure oil is gradually decreased in the high speed rotation range of the pump. A variable orifice is formed which performs a so-called drooping effect. Of course, various modifications can be made to the configuration for forming the variable orifice that performs such a drooping action.

In the flow path switching valve 12, two types of springs 1, large and small, are used to bias the spool valve 13 toward the high pressure chamber 18 side of the valve hole 12a.
4A and 14B are used to buffer the problem caused by the pressure oil from the second pump 2 suddenly joining the main passage 10 side when the spool valve 13 is activated, causing an excessive pressure rise. It is. That is, the large and small springs 14 mentioned above
The biasing force exerted on the spool valve 13 by A and 14B exhibits non-linear characteristics and serves to slow down the rapid movement of the spool valve 13. Further, an annular groove 13e formed on the low pressure chamber 17 side of the land portion 13d of the spool valve 13 also plays a similar role. In addition, 13f in the figure is spool valve 1.
This is a rod part that regulates the amount of movement of 3.

The apparatus configured as described above operates as follows.

First, FIG. 13 shows that the engine speed is low and the power steering device 5 is in a non-operating state, that is, no load is applied to the power steering device 5 and the main passage 1
The case where the fluid pressure in 0 is low pressure is shown. In this state, both valves 12 and 20 remain inactive, and as a result, pressure oil from the first pump 1 is supplied to the power steering device 5 through the main passage 10, but the pressure oil from the second pump 2 is supplied to the power steering device 5 through the main passage 10. is sub passage 11, reflux passage 1
It is connected to the tank 3 via the pump 5, and the pressure oil circulates through the second pump 2 and the tank 3, and is maintained in an unloaded state. This is because even if the supply amount of pressure oil is small, it does not affect the power steering device 5 at all. The flow rate characteristics in this state are shown by the solid line a in Fig. 15, and the horsepower consumption due to this is shown by the solid line a in Fig. 16, which is about half or less than the conventional one (see the broken line b in the figure). .

In addition, in Fig. 15, P ₁ is the discharge amount of the first pump 1, P ₂ is the discharge amount of the second pump 2, and P ₁ + P ₂ is a straight line showing the relationship between the total discharge amount and the pump rotation speed. be.

In addition, in Fig. 16, P ₁ is the horsepower consumption of the first pump 1, P ₂ is the horsepower consumption of the second pump 2, P ₁ +P ₂
is a straight line showing the relationship between the total horsepower consumption and the pump rotation speed.

On the other hand, when the load increases due to the operation of the power steering device 5 from the low speed and low pressure state shown in FIG. 13, and the state becomes low speed and high pressure, the flow path switching valve 12 is activated as shown in FIG. 14A. The second pump 2 and tank 3 are separated, and the second pump 2 is connected to the main passage 10 via the check valve 16. Therefore,
The pressure oil from the second pump 2 joins the pressure oil from the first pump 1 in the main passage 10 and is supplied to the power steering device 5 to generate the necessary steering operation assisting force and improve the operation. There is no problem. The flow rate characteristics when the load is large are shown by the solid line b in FIG. 15, and the horsepower consumption is shown by the solid line c as shown in FIG. 16, which is the same as in the conventional case (see the broken line d in the same figure). Of course, in this state, the horsepower consumption cannot be reduced.

In addition, in a high-speed, low-pressure state where the pump discharge amount increases to a predetermined amount or more as the rotation speed increases and the power steering device 5 is inactive, the flow rate control valve 20 increases as shown in FIG. 14B. operates to release a part of the pressure oil from the first pump 1 flowing through the main passage 10 to the tank 3 side via the return path 28, and control the amount of supply to the power steering device 5 at a constant level. The large diameter portion 4 of the stepped annular groove 40 that further narrows the orifice 22
The supply amount is reduced by the drooping effect of 0a and further maintained at a constant amount at a predetermined position. At this time, the flow path switching valve 12 is in a non-operating state, and the pressure oil from the second pump 2 is transferred to the sub-path 1.
1 and return to the tank 3 via the reflux path 15. Of course, a part of it is the sub passage 11 and the flow control valve 2.
The water returns to the tank 3 via a reflux path 28 that communicates with the tank 3 via the The flow rate characteristics in this state are shown in FIG. 15 by solid line a and solid lines c and d that are continuous at corner points X and Y, and the horsepower consumption is sufficiently small as shown by solid line a in FIG. 16.

Furthermore, during this high-speed circuit, when the power steering device 5 is activated and becomes in a high pressure state, the flow path switching valve 12 is also activated together with the flow rate control valve 20, as shown in FIG. 14C, and as a result, the second As described above, the sub passage 11 to which the pressure oil from the pump 2 is guided is connected to the reflux passage 28 via the bypass passage 30 and the annular groove 20b of the flow rate control valve 20, and communicates with the tank 3 side. Then, this pressure oil returns to the tank 3 side without opening the check valve 16, and on the other hand, a part of the pressure oil from the first pump 1 in the main passage 10 is also returned to the tank 3 side by this flow rate control valve 20. As a result, a certain amount of pressure oil is supplied to the power steering device 5. The flow rate characteristics at this time are shown by the solid line e in Fig. 15, and the horsepower consumption is shown by the solid line e continuous to the solid line c in Fig. 16, which is about half that of the conventional one (broken line d in the same figure). good.

The energy saving effect of the device of this embodiment described above is also made clear from the relationship diagram between horsepower consumption and pump discharge pressure shown in FIG. 17.

First, if the pump rotation speed is in the low speed rotation range,
As shown by the solid line a, in the no-load state, the horsepower consumption is about half that of the conventional system (see the broken line b in the figure), and as the load increases, the horsepower consumption remains the same.

In addition, in the high speed rotation range, as shown by the solid line c,
The horsepower consumption is approximately half that of the conventional method (see broken line d in the figure). This is because, at high speeds, regardless of the magnitude of the load, only the first pump 1 is involved in supplying hydraulic pressure to the power steering device 5, and the second pump 2 is unrelated.

Now, in this embodiment described above as well, the recirculation path 28 of the flow rate control valve 20 is constituted by a combination of a plurality of mutually independent holes, similar to the embodiment described above. The return flow path 28 formed by such a plurality of holes, for example, the small diameter passage 28a and the cast hole 28b shown in FIGS. 9A and 9B,
It has the following effects.

In other words, what is required in the flow rate control valve 20 that performs the drooping action as described above is to make the movement of the spool valve 21 as large as possible even when the specific discharge amount of pressure oil from the first pump 1 is small. The variable orifice that performs the drooping action must be appropriately constricted to improve its operability. On the other hand, it is necessary to secure a return path for the pressure oil from the second pump 2, and a low pressure chamber in the axial direction of the small diameter passage 28a and its valve hole 20a that narrows the opening side of the overflow passage as described above. Cast hole 28b that opens wide on the 27 side
According to the reflux path 28 consisting of the following, this effect can be exhibited. In particular, in the device configured as described above, when the rotational speed exceeds _N2 , the second pump 2 is always connected to the tank 3 side, and the main passage 10
The supply amount in the tank becomes about half or less than the normal amount, and as a result, the amount of valve displacement of the flow rate control valve 20 becomes small, and the above-mentioned countermeasures are required.
According to the above-described reflux path 28, as shown by the solid line a in FIG. 18, the effect can be expected to be greater than that of the conventional general circular passage (shown by the broken line b). In this case, C in the figure shows the characteristics of a shape that is a combination of large and small passage holes. Although the characteristics are somewhat similar to those of the present application, there are problems in terms of processability as described above,
Furthermore, if the valve displacement becomes large, the opening area becomes smaller than that of the present invention, which is unfavorable in terms of operation. Furthermore, in the reflux path according to the present invention, its characteristics can be freely changed by arbitrarily selecting the shape of the rear hole, which is a great advantage.

In addition, although the above-mentioned embodiment describes the case where the reflux path in the flow control valve is configured by a combination of two holes, the present invention is not limited to this, and the reflux path in the flow control valve is configured by a combination of a plurality of holes. It is easy to understand that it is sufficient if In short, the return flow path 28 formed in the valve hole 20a is a small diameter passage hole 28 that is bored by machining to define the operating stroke of the spool valve 21 for connecting the main passage 10 to the tank 3 side.
a and the valve hole 20 are mutually independent and
It is sufficient that the hole 28b is combined with at least one passage hole 28b having a large passage cross-sectional area that partially overlaps at the same location in the axial direction of the hole 28a.

Furthermore, in each of the embodiments described above, the first and second
Although a case has been described in which hydraulic pressure is supplied to the fluid equipment 5 using only the pumps 1 and 2, the present invention is not limited to this, and the present invention is not limited to this. Needless to say, it may be configured such that it can be connected to or disconnected from the main pump side passage in sequence.

Further, the pressure fluid supply device according to the present invention is not limited to the shape, structure, etc. described in each of the above-described embodiments, and can of course be modified and changed as appropriate.

As explained above, the pressure fluid supply device according to the present invention includes a pressure-sensing flow path switching valve that operates according to the magnitude of the load on the fluid equipment side, and a pressure-sensing flow path switching valve that operates according to the discharge amount from each pump. In order to skillfully combine this with a flow control valve that has a flow path switching function that recirculates excess pressure fluid to the tank side, and to connect the recirculation path in the flow control valve and the main passage to the tank side at its valve hole. A small-diameter passage hole bored by machining that defines the operating stroke of the spool, and at least one large passage cross-sectional area that is independent from the other and partially overlaps at the same location in the axial direction of the valve hole. Since it is constructed by combining with a single flow channel hole, the flow control valve can operate properly and reliably and exert its flow control function despite its simple structure and excellent workability. This has various excellent effects such as increasing the operational reliability of the entire device and significantly improving energy saving effects. Further, according to the present invention, when a drooping mechanism is attached, there is an advantage that the effect can be quickly and appropriately exerted.

Further, according to the device of the present invention, a plurality of pumps are used for supplying pressure fluid to fluid equipment, one pump is used as a main pump, and the remaining pumps are used as sub pumps, and these pumps are used to supply pressurized fluid to fluid equipment using a simple flow path switching mechanism. Since it is configured to be selectively disconnected from the equipment supply passage, despite its simple configuration, it can supply the minimum necessary pressure fluid, eliminate waste that was conventionally considered energy loss, and further reduce horsepower consumption. It has excellent effects such as reducing energy consumption, achieving energy savings, and maintaining reliable operating conditions without affecting fluid equipment in any way. Further, according to the present invention, the flow path switching mechanism is a structure in which a pressure sensing type flow path switching valve and a flow rate control switching valve having a flow path switching function are skillfully combined, and the structure is simple.
It has the advantage that it can be manufactured easily and that it can be expected to make the entire device lighter and more compact.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment in which the pressure fluid supply device according to the present invention is applied to a power steering device;
Figures A, B, and C are explanatory diagrams showing their operating states;
The figures are characteristic diagrams showing flow characteristics, Figures 4 and 5.
The figure is a characteristic diagram showing the relationship between horsepower consumption, pump rotation speed, and pump discharge pressure, and Figures 6 to 8 are diagrams for explaining the reflux path that characterizes the present invention.
9A and 9B are a plan view and a cross-sectional view showing an embodiment of the reflux passage that characterizes the present invention, FIG. 10 is a characteristic diagram showing the relationship between the opening area of the overflow passage of the sub-pump and the valve displacement, and FIG. 11 12 to 12 are plan views, cross-sectional views, and schematic diagrams seen from the direction of arrow C showing modified examples of the return flow path, and FIGS. 13 and 14 A, B, and C are systems showing other embodiments of the present invention. Figures 15 to 17 are characteristic diagrams showing the relationships between flow rate characteristics and pump rotational speed, horsepower consumption and pump rotational speed, and horsepower consumption and pump discharge pressure.
The figure is a characteristic diagram showing the relationship between the overflow passage opening area and the valve displacement. 1...First pump, 2...Second pump, 3
... Tank, 4 ... Flow path switching mechanism, 5 ... Power steering device (fluid equipment), 10 ... Main passage, 11
...Sub passage, 12...Flow path switching valve, 15...
...reflux path, 16... check valve, 20... flow rate control valve, 22... orifice, 28... return flow path, 2
8a...Small diameter passage, 28b...Cast hole, 29...
...Relief valve, 30...Bypass passage, 36,3
7... Reflux path, 36a, 36b; 37a, 37b
...Large and small diameter passages, 40...Stepped annular groove, 40a
...Large diameter section.

[Claims]

1 Power cylinder with cylinder bore
Assembled from a casing, a power piston reciprocatingly slidably disposed in the cylinder bore to define a pair of cylinder chambers within the cylinder bore, and an operating rod fixedly connected to the power piston. a power cylinder; a valve casing having a spool chamber; a cylindrical valve spool reciprocatably disposed in the spool chamber; The reaction plunger is assembled from a pair of reaction plungers forming a reaction chamber inside the cylindrical valve spool, and a reaction spring disposed between the pair of reaction plungers within the reaction chamber. Connect the chamber to the discharge side of the oil pump, and then connect the valve to the oil pump.
a control valve opening into the spool chamber for reciprocally sliding a spool into the valve chamber to selectively connect the discharge and suction sides of the oil pump to a pair of cylinder chambers of the power cylinder; The communication port formed in the valve casing,

Claims (1)

It is arranged in the middle of the inlet passage, and normally connects the second pump and the tank, and is activated by an increase in the load on the fluid equipment side to disconnect the second pump and the tank and connect the second pump to the tank. a flow path switching valve having a spool connected to the main passage; and a flow path switching valve connected in the middle of the main passage to supply pressure fluid from the first pump or a portion of the pressure fluid from the first and second pumps, respectively. A flow rate control valve having a spool that returns the flow to the tank side, and a variable orifice that throttles the main passage and performs a drooping action according to the amount of movement of the spool of the flow control valve, and the variable orifice that slides the spool of the flow control valve. The freely held valve hole has a small diameter passage hole drilled by machining that defines the operating stroke of the spool for connecting the main passage to the tank side, and the small diameter passage hole is independent of each other. A return flow path to the tank side is opened at the same location in the axial direction of the valve hole, which is formed by a combination of at least one flow path hole having a large flow path cross-sectional area that partially overlaps. Pressure fluid supply device.