JPH0152229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device that is mounted on various types of automobiles and used to reduce the steering force of a driver.

This type of power steering device is generally referred to as power steering, and allows for light and quick steering operations, as well as stable driving without the need to take the steering wheel, even when driving on rough terrain. Because they play a major role in reducing human fatigue, they are widely used in everything from large trucks and buses to small cars.

By the way, in such a power steering device,
The pump that is the source of the oil pressure is usually rotationally driven by an automobile engine. Therefore, the amount of hydraulic oil discharged from such a pump increases or decreases in proportion to the engine speed, and the pump capacity is adjusted to the level required for operation even in the low engine speed range, that is, when the pump discharge amount is small. It is set to supply a sufficient flow rate.

However, if you set the pump capacity like this,
In a high rotational speed range of the engine, an unnecessarily large flow rate is discharged, resulting in a lot of waste, and the horsepower consumed by the engine for driving the pump increases, which is not preferable from an energy-saving measure.

In particular, during actual driving, a large steering assist force from the power steering device is required when stopped and when driving at low speeds, and conversely, when driving at high speeds, a large steering assist force is not required. becomes. In other words, when the car is running at high speed, the amount of pressure oil supplied is large, and if this applies a large steering assist force, the steering wheel will become too light.
This creates a sense of anxiety for the driver, which is unfavorable in terms of steering performance, and the steering wheel is rarely operated greatly when driving at such high speeds, but only when driving at low speeds.

Therefore, in conventional devices of this kind, a flow control valve is installed in the middle of the discharge side passage of the pump to maintain a constant amount of pressure oil supplied to the device body in the high engine speed range, and to prevent activation due to excessive flow. In order to prevent defects, it is common practice to further add a so-called drooping mechanism to reduce the amount of pressure oil supplied to a certain extent in the high rotational range of the engine.

However, with this structure, the excess pressure oil discharged from the pump is simply returned to the tank, so it is not possible to reduce the horsepower consumption of the pump, and it is not possible to reduce energy consumption. This is not a desirable countermeasure.

For this reason, a configuration is conventionally known in which two pumps with small capacities are used and pressure oil from these two pumps is selectively supplied by a flow path switching mechanism. In other words, the above-mentioned flow path switching mechanism allows the pressure oil from both pumps to be combined and supplied to the main body only when necessary, and normally only one pump is used for oil pressure supply, while the other is connected to the tank side and is not used. The pump is in a loaded state, thereby reducing the horsepower consumption of the pump.

However, even if such a structure is adopted, each pump is constantly driven while the car is driving, and the loss is large, so it cannot be said that the waste of pump horsepower consumption has been completely eliminated. ,
There is still room for improvement. In particular, in recent years, there has been a great demand for improving the 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, in current power steering systems of this type, the pump, which is the source of hydraulic pressure, is connected to the engine via an electromagnetic clutch or driven by a motor, so that the pump can be turned on and off according to the vehicle speed.
It is considered that it can be turned off. That is,
When the car is running at low speeds, the pump is operated to supply pressurized oil to generate sufficient steering assist force when steering, but when the car is running at high speeds, the pump is stopped.
It is configured to perform manual steering. In this case, the steering operation during high-speed running is less likely to result in jerks if the steering wheel is turned too far, and it is preferable for the vehicle to have a certain degree of rigidity, so there is no problem in terms of running stability. With such a configuration, it is possible to minimize the horsepower consumption required to drive the pump, thereby achieving an energy saving effect.

However, the problem with controlling the pump on and off in this way is that when the pump is stopped, the steering wheel becomes extremely heavy and requires greater steering force than normal manual steering. It is to become like that. That is, even if the supply of pressure oil by the pump is stopped, the left and right cylinder chambers of the power cylinder that generate the steering assist force are filled with hydraulic oil on average. Therefore, when the driver operates the steering wheel, the piston of the power cylinder connected to the steering wheel moves while experiencing resistance from the hydraulic fluid in both chambers, which causes the steering wheel to become extremely heavy. The result is a sense of sensation for the driver.

For this reason, a check valve that short-circuits the discharge side and suction side of the pump has traditionally been attached to the control valve that controls the supply of pressure oil to the left and right cylinder chambers of the power cylinder. However, with such a check valve, it is impossible to expect the effect of quickly draining the hydraulic oil in the left and right cylinder chambers of the power cylinder in response to steering operations, but it is possible to achieve the above-mentioned steering feel with a simpler and more appropriate configuration. There is a need for a device that can be made suitable. In particular, the above-mentioned steering force during manual steering varies depending on driving conditions such as vehicle speed, payload, and even steering angle, so it is necessary to take these points into account to obtain an appropriate steering feel. It is hoped that Furthermore, in a device equipped with a pump that is controlled on and off, the structure must be such that an appropriate steering assist force can be generated when the pump is in operation, and such points must also be taken into consideration.

Further, in the above-mentioned system that controls the pump on and off, there is a problem in that when the pump is activated or stopped, the steering force suddenly changes, resulting in a steering wheel shock. This is shown by the solid line in FIG. In addition, in the figure, f _ON is the steering force when the pump is operating, and f _OFF is the steering force when the pump is stopped.

For example, when the pump is started while steering, the steering angle suddenly increases, which may result in the steering wheel being turned too much. Similarly, even if the steering wheel is stopped, it is necessary to take measures to prevent the above-mentioned sudden change in steering force and to make the change in steering force as gradual as possible, as shown by the broken line in FIG. In particular, the problem of such changes in steering force also differs depending on the steering force of each driver, steering angle, vehicle speed, and even the loaded load, so these points must also be taken into consideration.

The present invention has been made in view of these circumstances, and includes a bypass passage connecting the left and right cylinder chambers of the power cylinder that generates steering assist force, and a pump that operates by sensing the fluid pressure introduced when the pump is activated. A control valve having a pair of left and right valve bodies that shuts off this bypass path is installed, and is variably controlled by a controller in series with the control valve in the bypass path in accordance with various running conditions of the vehicle when the pump is stopped. Even if the pump is controlled on and off, it is possible to reliably isolate both cylinder chambers and generate an appropriate steering assist force when the pump is in operation. When stopped, both cylinder chambers are short-circuited via a bypass path, and the flow path resistance is adjusted, allowing manual steering to be performed appropriately depending on the driving conditions.Furthermore, the fluid pressure that controls the operation of the control valve is Similarly, by providing a variable throttle on the signal path that is variably controlled by the controller according to various vehicle running conditions immediately after the pump is activated or stopped, it is possible to prevent sudden changes in the steering force when the pump is turned on or off. The present invention provides an energy-saving type power steering device.

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

FIG. 2 shows an embodiment of the power steering device according to the present invention. In the same figure, the reference numeral 10 is an oil pump serving as a hydraulic pressure source for the power steering device, and this pump 10 is connected to a motor. 11, and serves to feed the hydraulic oil in the oil tank 12 to the main body of the device. The motor 11 that drives the pump 10 is controlled on and off by a controller 13 that sends out a control signal depending on the vehicle speed. That is, when the vehicle is running at a low speed below a predetermined speed, the pump 10 is activated by the motor 11.
is activated to supply pressure oil, and is configured to be stopped when the vehicle is traveling at a predetermined speed or higher. Of course, the points at which the pump 10 is turned on and the points at which it is turned off are set to be shifted by a desired width,
Care is taken to prevent the pump 10 from operating intermittently.

In this embodiment, the pump 10 is connected to the motor 11.
However, the present invention is not limited thereto, and the pump 10 may be driven, for example, by an automobile engine via an electromagnetic clutch, and this electromagnetic clutch may be controlled by the controller 13 described above. Needless to say, it may be configured as follows.

14 is a control valve that switches the flow path of the pressure oil from the pump 10 according to the steering direction of a steering wheel (not shown), and 15 is the control valve 14 that allows the pressure oil from the pump 10 to flow through the left and right cylinder chambers 15a, A piston rod 16 extends from a piston 16 that slides within this power cylinder 15.
a, 16a are connected to left and right steering wheels via a steering link mechanism (not shown). In the figure, 17a and 17b are the suction side and discharge side pipes of the pump 10, 17c is the return pipe from the control valve 14 to the tank 12, and 18a and 18b are the left side from the control valve 14 to the inside of the power cylinder 15.
This is a pipe line leading to the right cylinder chambers 15a and 15b.

Now, according to the present invention, in the power steering device having the above-described configuration, the left and right cylinder chambers 15a and 15b of the power cylinder 15 are connected to the bypass path 2.
A pair of left and right valve bodies 21 and 22 which are connected at 0 and shut off this bypass passage 20 by sensing the fluid pressure introduced when the pump is operated.
A control valve 23 having a control valve 23 is interposed in the bypass path 20, and a controller 24 is operated according to various running conditions of the vehicle when the pump is stopped.
The present invention is characterized in that a variable throttle 25 that is variably controlled by is arranged in series with the control valve 23 in the bypass passage 20.

That is, the bypass passage 20 described above is connected to the control valve 2.
By controlling the opening and closing at 3, the left and right cylinder chambers 15a and 15b are reliably isolated when the pump is in operation to generate an appropriate steering assist force, and the left and right cylinder chambers 15a and 15b are short-circuited when the pump is stopped. This structure reduces the steering force required for manual steering operation, and allows the steering force when the pump is stopped to be adjusted depending on various driving conditions.

To explain this in detail, in the figure, 27 is a valve body having a valve hole 28, 29 is a plug that closes the opening of the valve hole 28, and inside this valve hole 28 are a pair of left and right valve bodies 21, 22. is slidably supported and biased toward both ends by a spring 30 disposed at the center. A low pressure side fluid pressure signal path 31 is connected between these valve bodies 21 and 22 through a passage hole 27a to form a low pressure chamber 32, and this signal path 31 is connected to the return pipe 17c.
is connected to the tank 12 side, that is, the pump suction side.

Further, high pressure chambers 33a and 33b formed by recesses 22a and 22a formed at the outer ends of each valve body 21 and 22 are provided with a passage hole 34a formed at the bottom of the plug body 29 and the valve body 27. , 34b, a pair of left and right conduits 20a, 20b constituting the bypass path 20 are connected. When the pump is stopped, the left and right cylinder chambers 1 of the power cylinder 15 are connected to the pipes 20a and 20b.
5a, 15b flows into the high pressure chambers 33a, 33b of the control valve 23, and when the pump is in operation, the fluid pressure on the discharge side from the pump 10 flows into the control valve 14, the left and right cylinder chambers 15a,
15b. That is, in the control valve 23 according to the present invention, the high-pressure side fluid pressure signal that guides the fluid pressure signal during pump operation is transferred to the pipe line 2 constituting the bypass passage 20.
Another feature is that 0a and 20b are used. This configuration has the advantage that the circuit configuration of the entire device is easy, and it is advantageous in terms of operation, ease of assembly, and cost.

Further, each of the valve bodies 21 and 22 has an annular groove 35 and 36 on the outer periphery near the center of the valve hole 28, and each of these annular grooves 35 and 36 has a passage 21b formed in the valve body 21 and 22, 22b, the high pressure chamber 3
It is connected to the recesses 21a, 22b forming the recesses 3a, 33b. The annular grooves 35 and 36 are configured to be connected by a communication path 37 formed on the side of the valve body 27 when the valve bodies 21 and 22 are located at both ends of the valve hole 28 when the pump is stopped. Thus, a bypass path 20 is formed. In addition, 38 in the figure indicates each valve body 21, 2.
This is a stopper for regulating the movement of 2.

In the middle of the bypass passage 20 having the control valve 23 configured as described above, that is, in the communication passage 37 connecting between the annular grooves 35 and 36 of each valve body 21 and 22 of the control valve 23, various types of vehicles are connected when the pump is stopped. A variable aperture 25 is provided that is variably controlled by a controller 24 depending on driving conditions and the like. In this case, the variable throttle 25 is provided on the communication path 37 because the bypass pipe 25 forming the bypass path 20 is
This is because 0a and 20b serve as fluid pressure signal paths for operating the respective valve bodies 21 and 22, and therefore they need to be disposed at positions that do not have any influence.

That is, in the configuration described above, the pump 10
When the valve body 21, 22 is stopped, there is no pressure difference between the bypass pipes 20a, 20b, which also serve as the fluid pressure signal path on the high pressure side, and the fluid pressure signal path 31.
As shown in FIG. 2, the left and right cylinder chambers 15a, 15a of the power cylinder 15 are located at both ends of the valve hole 28 due to the biasing force of the spring 30, and the bypass passage 20 formed thereby allows the left and right cylinder chambers 15a, 15b
is shorted. Therefore, if a steering operation is performed in this state, the left and right cylinder chambers 15a,
The problem is that the hydraulic oil in 15b flows through the bypass passage 20 to the opposite cylinder chamber or tank 12 side in response to the movement of the piston 16 that is linked to the steering wheel, and this becomes a load that impedes the movement of the piston 16. This eliminates the problem of the handle being extremely heavy as in the past.
It becomes possible to perform appropriate manual steering with reduced steering force.

At this time, the variable aperture 25 according to the present invention
By providing this in the communication path 37 forming the bypass path 20, it becomes possible to adjust the manual steering force when the pump is stopped depending on various running conditions. This is due to the amount of throttle of these variable throttles 25.
This can be easily understood from the fact that the hydraulic oil flowing between a and 15b is subjected to resistance, which acts as a load on the piston 16 and changes the steering force.

For example, in high-speed cars, it is preferable that the steering force be heavy, and the aperture amount of the variable aperture 25 should be increased.On the other hand, in low-speed cars, it is preferable that the steering force be as light as possible, and the aperture amount should be small or zero. .

Therefore, the conditions given to the controller 24 that controls the variable aperture 25 include, for example, vehicle speed (when the speed is high, the aperture amount is large), live load (large load → small aperture amount), and steering angle (large angle → aperture amount). small quantity),
Various conditions can be considered, such as steering force (large force→small throttle amount), and a manual knob or the like may be provided to allow adjustment according to the driver's preference.

In addition, in this case, the controller 24 and motor 1
It is free to use the same controller 13 that controls the first and other controllers.

Further, when the pump 10 is operated and the supply of pressure oil is started, the fluid pressure is applied to the signal paths 20a and 20b.
The valve bodies 21 and 22 move toward the low pressure chamber 32 against the biasing force of the spring 30, respectively. and,
By moving the valve bodies 21 and 22 in this manner, each of the annular grooves 35 and 36 is separated from the communication passage 37 constituting the bypass passage 20, and the bypass passage 20 is blocked. Therefore, the left and right cylinder chambers 15a and 15b of the power cylinder 15 are reliably isolated, so that the pressure oil selectively supplied via the control valve 14 can provide normal steering assist force. It functions to reduce steering wheel operation.

Then, when the pump 10 is stopped again, each valve body 21, 22 is returned to its original state by the spring 30, and as a result, the left and right cylinder chambers 15a, 1
5b is short-circuited at the bypass path 20, resulting in a manual steering state.

Fig. 3 shows another embodiment of the power steering device according to the present invention, and in this figure, the same or corresponding parts as in Fig. 2 are given the same numbers, and detailed explanation thereof will be omitted. .

Now, according to this embodiment, in addition to the first variable throttle 25 provided on the communication path 37 of the bypass path 20, the pump 1
Second variable apertures 40, 41 that are variably controlled according to various driving conditions of the vehicle immediately after the zero operation or stop.
or 42 is provided in either one of the fluid pressure signal paths 20a, 20b, or 31 for operating the valve bodies 21, 22 of the control valve 23. That is, the fluid pressure signal path 20
a, 20b; By providing a throttle in a part of 31, the opening/closing control operation of the control valve 23 is slowed down to prevent a sudden change in the steering force immediately after the pump 10 is activated or stopped, and to reduce the steering wheel shock. By making the diaphragm variable, the control can be controlled with a degree of freedom, making it possible to cope with various driving conditions.

To explain this in detail, when the pump 10 is activated or stopped, pressure oil is rapidly sent to the power cylinder 15 side, or the delivery of pressure oil is suddenly stopped, so that the pressure oil suddenly flows inside the left and right cylinder chambers 15a and 15b. This causes a sudden increase or decrease in the pressure, which causes a sudden change in the steering force. However, as mentioned above, the variable restrictor 40, 41 or 42 is provided in a part of the fluid pressure signal path 20a, 20b; 31. Therefore, each of the valve bodies 21 and 22 can be operated slowly, making it possible to absorb the above-mentioned sudden changes.

However, the need for the slow operation of the valve bodies 21 and 22 described above differs depending on various driving conditions.
In some cases, it may become unnecessary.

For example, when the pump 10 is turned on and off during steering, it is necessary to increase the throttle amount to prevent sudden changes in steering force and reduce steering wheel shock.
It's not really a problem when driving straight. and,
At this time, the amount of aperture may be made small or zero.

Therefore, the conditions given to the controller 24 that controls the second variable aperture 40, 41, or 42 include, for example, the steering angle (when the angle is large, the aperture amount is large), the vehicle speed (vehicle speed is large → the aperture amount is Possible factors include: (small), live load (large load → large amount of throttle), steering force (large force → large amount of throttle), and driver preference. Under these conditions, the amount of aperture of the variable aperture 40, 41, or 42 may be adjusted as appropriate.

What should be noted about the control of the second variable diaphragm 40, 41 or 42 by the controller 24 is that it is completely opposite to the control of the first variable diaphragm 25 described above. In the example, both variable apertures are controlled by the same controller 24. However, it goes without saying that the control unit is not limited to this and may be provided as a separate control unit. In addition, the second
The variable diaphragm 40, 41 or 42 can function satisfactorily by providing it at any one location.

In the two embodiments described above, in the control valve 23 having a pair of left and right valve bodies 21, 22, a high pressure chamber 33a,
33b, and a low pressure chamber 32 is formed therebetween, and the low pressure chamber 32 is also used. However, the present invention is not limited to this, and the present invention is not limited to this. The body may be moved, and various modifications are possible. Moreover, the shape, structure, etc. of other parts can be changed as appropriate.

As explained above, according to the power steering device according to the present invention, there is provided a bypass passage connecting the left and right cylinder chambers of the power cylinder that generates a steering assist force, and a bypass passage that is disposed in this bypass passage and that is guided when the pump is operated. A control valve having a pair of left and right valve bodies is provided in the bypass passage to sense the fluid pressure being released and operate to shut off the bypass passage. Because we have installed a variable throttle that is variably controlled by the controller, despite the simple configuration, even if the pump is controlled on and off, when the pump is operating, both cylinder chambers are reliably isolated and proper steering can be achieved. While it is possible to generate an auxiliary force and perform light steering operations, when the pump is stopped, both cylinder chambers are short-circuited and the flow path resistance is adjusted to perform appropriate manual steering according to the driving conditions. can.

Further, according to the present invention, the fluid pressure signal path for operating the above-mentioned control valve also has a second variable that is variably controlled by the controller depending on various running conditions of the vehicle immediately after the pump is activated or stopped. By providing a throttle, it is possible to prevent sudden changes in steering force when controlling the pump on and off, taking into consideration driving conditions, etc., reducing steering wheel shock, and improving reliability as a power steering device. This makes it possible to improve the performance and further improve functionality, which has a great effect.

By using the above-mentioned power steering device according to the present invention to operate the pump when the vehicle is running at low speeds and stop the pump when the vehicle is running at high speeds, the consumption caused by driving the pump can be reduced without any hindrance to steering performance. It is possible to reduce the horsepower to the minimum necessary and achieve energy saving effects.

Further, according to the present invention, a control valve having a structure capable of opening and closing a bypass passage with a pair of valve bodies is used, and the fluid pressure for operating each valve body is guided using the bypass passage. Because of this, it has the advantages of a simple structure, high operational reliability, excellent mass productivity, and low cost.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram showing changes in steering force when a pump is controlled on and off in a conventional power steering device, and FIG. 2 is a schematic configuration diagram showing an embodiment of a power steering device according to the present invention. FIG. 3 is a schematic configuration diagram showing another embodiment of the present invention. 10... Pump, 11... Motor, 12... Tank, 13... Controller, 15... Power cylinder, 15a, 15b... Left and right cylinder chambers,
16... Piston, 20... Bypass path, 20
a, 20b... Bypass pipe line, 21, 22... Valve body, 23... Control valve, 24... Controller, 2
5...First variable throttle, 31...Fluid pressure signal path,
40, 41; 42...Second variable aperture.

Claims (1)

[Claims] 1. A pump that is turned on and off as necessary to send out pressurized fluid, and that the pressurized fluid from this pump is selectively supplied to left and right cylinder chambers in response to steering operations. A power cylinder that generates steering assist force, a bypass passage that connects the left and right cylinder chambers of this power cylinder, and a bypass passage that is interposed in this bypass passage and operates by sensing the fluid pressure introduced when the pump is activated. and a control valve having a pair of left and right valve bodies that shut off this bypass passage when the pump is stopped. The controlled variable aperture
A power steering device, characterized in that it is arranged in series with the control valve. 2. A pump that is turned on and off as necessary to send out pressurized fluid, and the pressurized fluid from this pump is selectively supplied to the left and right cylinder chambers in response to steering operations to generate steering assist force. a power cylinder that connects the left and right cylinder chambers of this power cylinder, and a bypass passage that is interposed in this bypass passage and is activated by sensing the fluid pressure introduced when the pump is activated. a control valve having a pair of left and right valve bodies for blocking the passage; and a control valve provided in the bypass passage in series with the control valve, and is variably controlled by a controller in accordance with various vehicle running conditions when the pump is stopped. A bypass path which also serves as a fluid pressure signal path for guiding the fluid pressure on the discharge side of the pump is connected to one end side in the moving direction of each valve body of the control valve. A fluid pressure signal path that guides fluid pressure on the suction side of the pump is connected to the other end, and one of these fluid pressure signal paths is connected to a controller that is connected to a controller depending on vehicle running conditions immediately after the pump is activated or stopped. The second
A power steering device characterized by being provided with a variable throttle.