JPS639112B2 - - 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.

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 engine of the automobile. The amount of hydraulic oil discharged from this pump increases or decreases in proportion to the engine speed. Therefore, such a pump is required to have a capacity that can supply a sufficient flow rate to the operation of fluid equipment such as the power steering device even when the engine speed is low, that is, when the pump discharge amount is small. be done.

However, if you set the pump capacity like this,
In the high rotation range of the engine, an unnecessarily large flow rate is supplied to the power steering device, which is wasteful and also increases the horsepower consumption of the engine to drive the pump, which is not preferable in terms of engine saving. 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 pump for the power steering device described above.

For this reason, conventionally, a pair of pressure chambers provided at symmetrical positions in one pump cartridge have been separated.
A pressurized fluid supply device is proposed that can be used as a single pump or two separately installed small-capacity pumps, and selectively supplies pressurized oil from both pumps using a flow path switching mechanism. has been done. In other words, the above-mentioned flow path switching mechanism allows only one pump to be used for hydraulic pressure supply at all times, and the other pump is connected to the tank side to be in an unloaded state, thereby reducing horsepower consumption and allowing both pumps to be used only when necessary. Combines and supplies pressure oil from the
As a method of controlling the supply amount of pressure oil, for example, in the low rotation range of the engine, that is, when the discharge amount of each pump is small, there is a rotation that combines the pressure oil from both pumps in response to the flow rate. A pressure sensing type that detects the fluid pressure generated when the power steering device operates due to a load being applied to the fluid equipment side, regardless of the engine speed, and merges the pressure oil from both pumps. etc. are known.

However, in the former case, only one pump is driven when the car is running at high speeds, that is, in the high engine speed range, which reduces horsepower consumption, but on the other hand, energy loss is unavoidable in the low engine speed range. However, there is still room for improvement. This is because a large amount of pressure oil is required only during steering operations that place a load on the vehicle; for example, when the engine is stopped or driving straight, a small amount of pressure oil is required 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 desirable to reduce horsepower consumption during such low-speed driving.

In the latter case, the above-mentioned problem in the low engine speed range can be solved and energy can be saved, but on the other hand, energy loss in the high engine speed range is unavoidable. That is, when the power steering device is not operating in the low rotational speed range of the engine, the other pump is connected to the tank side and placed in an unloaded state, thereby reducing its horsepower consumption. However, when the power steering device operates in a high rotation range where only one pump can supply sufficient pressure oil, the flow path is switched and the pressure oil from both pumps is combined, resulting in more than necessary Pressure oil is sent to the power steering device, which is not only wasted, but also causes malfunction due to excessive flow. For this reason, a flow control valve has traditionally been attached to maintain a constant supply amount in the high rotation range, and the rest is returned to the tank, but the problem in this case is running stability. This is the point.

In other words, if a large amount of pressure oil is supplied when the car is running at high speed, the steering wheel will become too light, causing a sense of uneasiness for the driver, which is unfavorable in terms of steering performance. When driving at high speeds, the steering wheel is rarely operated significantly, and this only occurs when driving at low speeds. Therefore, it has been common practice in the past to add a so-called drooping mechanism to this type of device so that the amount of pressurized oil supplied can be reduced to some extent in the high speed range of the engine. This drooping mechanism is often used in passenger cars and the like, and its advantages are great.

When such a drooping mechanism is used, since the amount supplied is less than a predetermined amount in the high speed range of the engine, the steering wheel feels responsive and has excellent steering performance, and its effects can be demonstrated when the vehicle is running at high speed. Moreover, this drooping mechanism
Due to this configuration, when the load in the hydraulic path increases during steering operation, the necessary supply amount can be sequentially increased accordingly, so that a good steering feeling can be obtained. In addition, such a drooping mechanism reduces the amount of pressure oil supplied to the power steering device during high-speed running, thereby minimizing pressure loss in the piping and power steering device, thereby reducing energy loss. It is effective and useful.

Therefore, it has been considered to combine the drooping mechanism, which has such advantages, with the above-mentioned energy-saving pressure fluid supply device, but the problem here is that the above-mentioned In the case of a pressure sensing type, if a drooping mechanism is simply added, the drupping effect cannot be achieved unless the engine speed is considerably higher than when attached to a normal pump, which poses problems in terms of operating characteristics. There are many. This is a configuration in which the conventional drooping mechanism uses a flow control valve installed in the hydraulic pressure supply path, and the rotation speed required to obtain the amount of pressure oil supply necessary for this control valve to operate is considerably higher than that of the conventional drooping mechanism. This is because it becomes expensive.

In view of these circumstances, the present invention includes a flow path switching valve that operates according to the magnitude of the load on the fluid equipment side, and
A simple configuration in which the two pressure receiving parts of the flow control valve disposed in the fluid supply path have a difference in area, and the flow rate adjusted by the flow control valve of the pressure fluid is varied according to the magnitude of the load on the fluid equipment side. This provides a pressurized fluid supply device that not only eliminates wasted pump horsepower consumption and further improves energy saving effects, but also significantly improves the operating performance of fluid equipment. It is.

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

FIG. 1 shows an embodiment in which a pressure fluid supply device according to the present invention is applied to a power steering device for an automobile. Both pumps are rotationally driven by an engine (not shown). Both pumps 1 and 2 play the role of circulating and supplying the hydraulic oil in the tank 3 to the power steering device 5 via the control section 4.

Note that these two pumps 1 and 2 do not necessarily need to be constructed separately, but may be constructed integrally with a common casing and pump drive shaft,
Alternatively, a pair of pressure chambers provided at symmetrical positions in one pump cartridge may be used as separate pumps. In this case, the energy saving effect can be further increased by making the capacity of the first pump 1 smaller than that of the second pump 2. In addition, in the figure, 1a and 2a are the suction side pipes of each pump 1 and 2, 1b and 2b are the same discharge side pipes, and 3a
5a is a tank side pipe connected to the pipes 1a and 2a, and 5a is the control section 4 and the power steering device 5.
The pressure oil supply pipe 5b in between is a return pipe to the tank 3.

Now, according to the present invention, the control unit 4 for selectively supplying the pressure oil discharged from the first and second pumps 1 and 2 to the power steering device 5 is configured as follows. ing.

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

This flow path switching valve 12 has a valve hole 12a provided in the casing 4a so that one end opens on the side of the main passage 10, and a spool 13 slidably supported within the valve hole 12a. This spool 13 is normally biased by a spring 14 and located on the main passage 10 side of the valve hole 12a. In this state, the sub passage 11 opened at the axial center of the valve hole 12a.
is an annular groove 1 separated from the main passage 10 by the spool 13 and provided on the outer periphery of the spool 13.
It is connected to a drain passage 15 arranged in parallel to the sub passage 11 via 3a, and further communicates with the tank 3 via a drain pipe 15a continuous with this drain passage 15.

Therefore, when the flow path switching valve 12 is not in operation, only the discharge amount from the first pump 1 is supplied to the power steering device 5 via the main passage 10, and the discharge amount from the second pump 2 is supplied to the power steering device 5 via the main passage 10. Pressure oil from the tank 3 is circulated between the tank 3 and the tank 3. As a result, this second pump 2 is kept in an unloaded state, and the horsepower consumption for driving it becomes extremely small, making it possible to exhibit an energy-saving effect.This is because the pump discharge volume is small, and It is particularly large at low speeds and low pressures when the power steering device 5 is in an unloaded state.

Moreover, this flow path switching valve 12 is connected to the spool 1
3 has a check valve 16 at the end on the main passage 10 side, and when the spool 13 moves to the right in the figure, the sub It is connected to the passage 11. Of course, during this operation, the sub passage 11 and the drain passage 15 are separated by the spool 13. The check valve 16 is opened by the pressure oil from the second pump 2 and guides it into the main passage 10, as shown in FIG. 2, to join the pressure oil from the first pump 1. shows.

Incidentally, the hydraulic pressure from the tank 3 side is led to the low pressure chamber 17 on the right side of the spool 13 in which the spring 14 is disposed through a small hole 13d, and this spool 1
The left end of 3 faces into the main passage 10. Therefore, this spool 13 senses only when the fluid pressure on the main passage 10 side rises due to an increase in the load on the power steering device 5, moves to the right in the figure, and switches the flow path.

Further, there is a part in the middle of the main passage 10 for detecting the flow rate of the pressure oil from the first pump 1 or the combined pressure oil from the first and second pumps 1 and 2 flowing inside the passage 10. An orifice 20 is provided, and a flow control valve 21 that operates according to the fluid pressure difference before and after the orifice 20 is provided. The flow rate control valve 21 controls the flow rate of the pressure oil flowing through the main passage 10 and releases the excess pressure oil to the tank 3 side, and has a valve hole 21a provided in parallel with the main passage 10. It has a spool 22 that slides within it. Pressure oil on the upstream side of the orifice 20 is guided through a passage 24 to a high pressure chamber 23 formed on the left end side of this spool 22, and the orifice is introduced into a low pressure chamber 25 formed on the right end side. Pressure oil on the downstream side of the valve 20 is guided through a passage 26 having an orifice 26a for preventing valve oscillation. The spool 22 is normally connected to the low pressure chamber 2.
5 is located on the high pressure chamber 23 side due to the biasing force of a spring 27 provided in the valve hole 21a.
The drain passage 28, which opens laterally, and the high pressure chamber 23 are separated from each other. In addition, 28a in the figure is a drain pipe connecting the drain passage 28 to the tank 3 side,
29 is a relief valve attached within the spool 22.

Now, the flow rate control valve 21 having such a configuration moves sequentially to the low pressure chamber 25 side according to the pressure difference generated before and after the orifice 20, and as a result, the high pressure chamber 23
It is operated so that a part of the pressure oil in the main passage 10 is released to the tank 3 side via the passage 24 by connecting the drain passage 28 and the drain passage 28. However, the point to note here is that Two pressure receiving parts 22
A and 22b have a difference in area.
That is, the spool 22 is formed in a stepped shape so that the low pressure chamber 25 side thereof has a larger diameter, so that the low pressure chamber 25 side of the valve hole 21a is also formed to have a larger diameter.

With this configuration, the flow rate control valve 21 is given a function to follow the increase in the load on the power steering device 5, and the flow rate controlled by the valve 21, that is, the flow rate returned to the tank 3 side is changed, and the main The adjusted flow rate of the pressure oil supplied from the passage 10 to the power steering device 5 can be varied in stages. That is, the flow control valve conventionally used in this type of device has a function of maintaining the supply amount of pressure oil at a constant amount, but according to the present invention, the supply amount of pressure oil is controlled by the power steering device 5 side. It is configured to vary according to the magnitude of the load, thereby producing an effect similar to the conventional drooping effect.

Here, the dynamic balance of the spool 22 of the flow control valve 21 will be described in detail.

That is, when the power steering device 5 is in an unloaded state, that is, when no steering operation is being performed, S·P ₁ =(S+S ₁ )·P ₂ +F (1).

However, S: Area of the high pressure chamber side pressure receiving part 22a of the spool 22, S+S ₁ : Low pressure chamber side pressure receiving part 22b of the spool 22
area, P ₁ : Fluid pressure on the upstream side of orifice 20, P ₂ : Fluid pressure on the downstream side of orifice 20 (<P ₁ ), F: Spring action force Now, from the state of equation (1) above, the power steering device can be calculated. 5
When a load is applied to the side and the fluid pressure in the main passage 10 increases by ΔP, the left side of equation (1) = S・(P ₁ + ΔP) ...(2) The right side of equation (1) = (S + S ₁ ) (P ₂ + ΔP) + F (3), and comparing equations (2) and (3), the amount of increase in pressure on the equation (3) side, that is, on the low pressure chamber side pressure receiving part 22b of the spool 22 is S ₁・It is confirmed that it is larger by ΔP.

Therefore, the spool 22 moves to the left until the force F of the spring 27 becomes F-(S ₁ ·ΔP), and as a result, the drain passage 28 connected to the main passage 10
is closed by that amount, thereby increasing the amount of pressure oil supplied.

The final balance of this spool 22 is S(P ₁ +ΔP+ΔP ₁ )=(S+S ₁ )·(P ₂ +ΔP)+(F−S ₁ ·ΔP) (4).

However, ΔP ₁ is the increase in the differential pressure that occurs before and after the orifice when the supply amount of pressure oil increases.

Therefore, according to the above-described configuration device, the flow path switching valve 12 does not operate unless the power steering device 5 is operated and a load greater than the set value is applied.
The second pump 2 is disconnected from the main passage 10 and placed in an unloaded state, thereby reducing the pump horsepower consumption and increasing the energy saving effect. When the discharge amount from the first pump 1 exceeds a certain set amount, the flow rate control valve 21 is activated.
Return excess pressure oil to tank 3 side.

What should be noted here is that the adjusted flow rate of the pressure oil during no-load conditions is set to the minimum necessary, which is approximately half of the conventional flow rate, and the flow rate characteristics at this time are shown by the solid line a in Figure 3. , and the dashed line b in the same figure shows the flow rate characteristics when a conventional drooping mechanism is adopted, and the broken line in the same figure shows the flow rate characteristics at no load when a drooping mechanism is adopted in a conventional pressure sensing device. Each is shown in c. As is clear from FIG. 3, the adjusted flow rate under no load by the device of the present invention is set to substantially match the flow rate when the drooping action is performed in the conventional device.

Therefore, according to the present invention, when the automobile is running at high speed, the rigidity of the steering wheel increases to a certain extent, similar to the conventional drooping effect, and the running stability can be guaranteed, resulting in excellent steering performance. There is. Such rigidity does not pose much of a problem in terms of steering performance when traveling at low speeds, and allows for nimble steering operations. In addition, as mentioned above, by setting the adjusted flow rate of pressure oil low during no-load conditions, the back pressure applied to the pump side can be reduced, and the pressure loss due to piping can be reduced, thereby further increasing the energy saving effect. becomes possible.

Furthermore, when the power steering device 5 operates and a load is applied, the flow path switching valve 12 operates to divert the pressure oil from the second pump 2 even if the pump rotation speed is low and the discharge amount is small. is combined with the pressure oil from the first pump 1 and sent through the main passage 10. At the same time, the flow rate control valve 21 also operates in the direction shown by arrow A in FIG. supply and guarantee its operational reliability. The ^flow rate adjusted by ^the flow rate control valve 21 according to the magnitude of the load is shown in FIG.
Draw the flow characteristics shown by f and g.

Therefore, according to the device of the present invention, the flow rate necessary for the operation of the power steering device 5 can be supplied according to the magnitude of the load on the side of the power steering device 5, without any adverse effect on the operation of the power steering device 5. , allowing for nimble steering operations.

In addition, in FIG. 2, P ₁ is the first pump 1,
P ₂ indicates the second pump 2, T indicates the tank 3, and P and S indicate the power steering device 5, respectively.

Furthermore, in the above-mentioned embodiment, a case was explained in which two pumps 1 and 2 were used as the pressure oil supply source.
It goes without saying that the present invention is not limited to this, and that a plurality of pumps may be used, one of which may be used as a main pump, and the remaining pumps may be used as sub-pumps and may be appropriately connected to the main passage and merged therewith.

As explained above, according to the pressure fluid supply device according to the present invention, the flow path switching valve senses and operates when a load is applied to the fluid equipment side and combines the pressure fluids from a plurality of pumps. By cleverly combining this with a flow control valve that can sense changes in the load on the fluid equipment side and return a portion of the pressure fluid flowing through the supply passage to the tank side, the flow rate can be varied to control the supply of pressure fluid when there is no load. Reduce the amount to the minimum necessary,
As the load increases, the adjusted flow rate is increased sequentially to supply the sufficient flow rate required for fluid equipment operation, making control of the pressure fluid supply amount much more rational than before, and reducing pump horsepower consumption. It is possible to further exhibit the energy saving effect by reducing the energy consumption to a minimum level, and not only have no adverse effect on the fluid equipment, but also to obtain a good operating state according to the required operating conditions. Furthermore, according to the present invention, the above-mentioned adjusted flow rate can be controlled by providing a difference in area between the two pressure-receiving parts of the flow control valve. High flow rate control is possible.

In particular, according to the device of the present invention, the amount of power supplied during no-load conditions is kept to the minimum necessary, so when used in a power steering device, the amount of horsepower consumed when no steering operation is performed is reduced in all driving conditions of the vehicle. This has the advantage of lowering the steering wheel and increasing the stiffness of the steering wheel near the neutral position to save energy and allow for comfortable and safe steering.

[Brief explanation of the drawing]

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;
The figure is an explanatory diagram of its operation, and FIG. 3 is a characteristic diagram showing its flow characteristics. DESCRIPTION OF SYMBOLS 1...First pump, 2...Second pump, 3...Tank, 4...Control unit, 5...Power steering device, 10...Main passage, 11...Sub passage, 12...Flow path switching valve,
15... Drain passage, 16... Check valve, 20... Orifice, 21... Flow rate control valve, 22... Spool, 22
a, 22b...pressure receiving part, 23...high pressure chamber, 24...passage, 25...low pressure chamber, 26...passage, 27...spring, 28...drain passage.

Claims (1)

[Claims] 1. A first and second pump that separately discharges pressure fluid, a main passage that supplies pressure fluid from the first pump to fluid equipment, and a tank that is normally connected to the second pump. and a flow path switching valve that is activated by an increase in load on the fluid equipment side to disconnect between the second pump and the tank and connect the second pump to the main passage, and a flow path switching valve disposed in the middle of the main passage. an orifice for detecting the flow rate of the pressure fluid from the first pump or the combined pressure fluid from the first and second pumps as a pressure difference before and after the orifice; and an orifice that operates according to the fluid pressure difference before and after the orifice. and a flow control valve that has a spool that releases a part of the pressure fluid in the main passage to the tank side, and of the two pressure receiving parts in the flow control valve, the fluid pressure downstream of the orifice is guided. A pressure fluid supply device characterized by a large side pressure receiving area.