JPS58139869A - Power steering gear - Google Patents

Abstract

PURPOSE:To prevent a steering force from being rapidly changed when a pump is started or stopped, by providing a throttle in a hydraulic pressure signal passage. CONSTITUTION:Left and right cylinder chambers 15a, 15b of a power cylinder 15 are connected to each other by a bypass passage 20, a controlling valve 22 having a valve body 21 for cutting off the bypass passage 20 at the time of operating the pump 10 is provided in the passage 20, and a fixed throttle 25 or 26 is provided in either one of the passages 23, 24 for hydraulic pressure signals introduced respectively to both end sides with respect to the moving direction of the valve body 21 for operating the valve body 21. With the fixed throttle thus provided, th controlling operation of the valve 22 is made to proceed slowly, so that a change in the steering force immediately after starting or stopping the pump 10 is absorbed as much as possible, whereby a steering shock is moderated.

Description

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

This type of power steering device is generally referred to as a power steering system, and allows for light and quick steering operations, as well as stable driving without losing control even when driving on rough terrain. Because this plays a major role in reducing driver fatigue, it is widely used in vehicles ranging from large trucks and buses to small cars.

Incidentally, in such a power steering device, the pump that is the oil pressure generation source is usually rotationally driven by the engine of the automobile. Therefore, the amount of hydraulic fluid discharged from such a pump increases or decreases in proportion to the engine speed, and the pump capacity is sufficient to maintain the necessary operating fluid even in the low engine speed range, that is, when the pump discharge amount is small. It is set to be able to supply the flow rate.

However, if the pump capacity is set in this way, an unnecessarily large flow rate will be discharged in the high rotation range of the engine, resulting in a lot of waste and the horsepower consumed by the engine to drive the pump will also increase, making it difficult to implement energy-saving measures. Do you like it?

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 this causes a large steering assist force, which causes the steering wheel to become too light, causing a sense of uneasiness for the driver. This is unfavorable in terms of performance, and when driving at such high speeds, the steering wheel is rarely operated significantly, and this only occurs when driving at low speeds.

Therefore, in conventional devices of this type, 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 malfunctions due to excessive flow. In order to prevent this, it is common practice to further add a so-called drooping mechanism to reduce the supply amount of pressure oil to some extent in the high rotational range of the engine. However, with such a structure, the excess pressure oil discharged from the pump is simply drained.
Since the pump only recirculates the water, the horsepower consumption of the pump cannot be reduced, and this is not a preferable measure for energy saving.

For this rounding, we used two pumps with small capacity,
A structure in which pressure oil from both of these pumps is selectively supplied by a flow path switching mechanism is known. 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, 1
The pump in the machine is constantly running while the car is running, and the loss is large, so it cannot be said that the waste of horsepower consumed by the pump has been completely eliminated, and 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, currently in this type of power steering system, the pump that is the source of hydraulic pressure is connected to the engine via an electromagnetic clutch or driven by a motor, and the pump is controlled on and off according to the vehicle speed. That is what is being considered. That is, when the vehicle is running at low speed, the pump is operated to supply pressurized oil to generate sufficient steering assist force during steering, while when the vehicle is running at high speed, the pump is stopped and manual steering is performed. In this case, the steering operation during high-speed running does not involve turning the steering wheel much, and it is preferable for the vehicle to have a certain degree of rigidity, so there is no problem in terms of running stability. and,
With this configuration, the amount of horsepower required to drive the pump is required! & Minimum energy saving effect can be achieved.

However, a problem with such on/off control of the pump is that when the pump is turned on or off, the steering force changes suddenly, resulting in steering shock. This is shown by the solid line in FIG.

In addition, fail in the figure is the steering force when the pump is operating, f
Ovv is the steering force when the pump is stopped.

For example, when the pump is started while steering, the steering angle suddenly increases, leading to the risk of turning the steering wheel too far. The same applies even if the pump is stopped, preventing the above-mentioned sudden change in steering force, and changing the steering force to the first level.
As shown by the broken line in the figure, it is necessary to take measures to make the curve as gentle as possible. In particular, the problem of such changes in steering force is related to the driver's steering force, steering angle, vehicle speed,
Furthermore, it differs depending on the load, etc., and such points must be taken into consideration.

In addition, as mentioned above, when the pump is controlled on and off, when the pump is stopped, the steering wheel becomes extremely heavy, which causes problems such as the need for greater steering force than with normal manual steering. . 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 being subjected to resistance from the hydraulic oil in the chambers on both sides, which causes the driver to feel that the steering wheel is extremely heavy. This results in negative consequences for the driver.

For this reason, a check valve has traditionally been installed in the control valve that controls the supply of pressure oil to the left and right cylinder chambers of the power cylinder to short-circuit the discharge side and suction side of the pump. However, such check valves cannot be expected to have the effect of quickly discharging the hydraulic fluid 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 simple and appropriate configuration. There is a need for a device that can be made suitable. In particular, in a device equipped with a pump that is controlled on and off, the structure must be such that it can generate an appropriate steering assist force when the pump is in operation, and such points must also be taken into consideration.

The present invention has been made in view of the above-mentioned circumstances, and includes a bypass passage connecting the left and right cylinder chambers of the power cylinder that generates steering assist force, and operates by sensing the fluid pressure introduced when the pump is operated. The pump can be operated using a simple configuration in which a control valve that shuts off this bypass path is disposed in the bypass path, and a fixed restrictor or a variable restrictor controlled by a controller is provided in the fluid pressure signal path that operates the control valve. When the on/off control is activated, the control valve is operated gently to isolate or communicate the two cylinder chambers. This prevents sudden changes in steering force, suppresses steering shock to its lowest level, and maintains proper control when the pump is operating. An energy-saving power steering device that generates steering assist force to enable light steering operations, and reduces steering force as much as possible when the pump is stopped to provide an appropriate steering feel. This is what we provide.

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, and in the same figure, the reference numeral 10 is an oil pump serving as a hydraulic pressure source for the power steering device.
is rotationally driven by a motor 11 and plays the role of feeding hydraulic oil in an oil tank 12 to the main body of the apparatus. 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, the pump 10 is operated by the motor 11 to supply pressurized oil when the vehicle is running at a low speed below a predetermined speed, and is stopped when the vehicle is running at a high speed above a predetermined speed. Of course, this pump 10
The timing of turning on and turning off the pump 10 is set to be shifted by a desired width to prevent the pump 10 from operating intermittently.

In this embodiment, the pump 10 is configured to be driven by the motor 11, but the present invention is not limited to this. For example, the pump 10 may be driven by an automobile engine via an electromagnetic clutch, It goes without saying that this electromagnetic clutch may be configured to be controlled by the controller 213 described above.

Reference numeral 14 denotes 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); 1511t This control valve 14 allows the pressure oil from the pump 10 to be routed between left and right cylinder chambers 15a and 15.
A power cylinder that generates a steering assist force by being selectively supplied to the power cylinder 15. Piston rods 18a and 16a extending from a piston 16 that slides inside the power cylinder 15 are connected to each other via a steering linkage mechanism (not shown). are connected to the left and right steering wheels. In addition, 17a in the figure,
17b is a suction side and discharge side pipe line of the pump 10, 17c is a return pipe line from the control pulp 14 to the tank 12,
18&, 18b are conduits extending from the control pulp 14 to the left and right cylinder chambers 15a, 15b of the power cylinder 15.

Now, according to the present invention, in the power steering device having the nine configurations described above, the left and right cylinder chambers 15a and I Sb of the power cylinder 15 are connected by a bypass passage 20,
A control valve 22 having a valve body 21 that connects the bypass passage 20 when the pump is operated is disposed in the bypass passage 20, and a control valve 22 is provided at both ends of the control valve 22 in the direction of movement in order to operate the valve body 21 of the control valve 22. Leading fluid pressure signal-23,
It is characterized in that a fixed aperture 25 or 26 is provided on either one of the apertures 24.

That is, by controlling the opening and closing of the above-mentioned bypass passage 20 with the control valve 22, when the pump is operating, the left and right cylinder chambers ISa and 15b are reliably isolated to generate an appropriate steering assist force, and when the pump is stopped, the left and right cylinder chambers ISa and 15b are isolated, and when the pump is stopped, the left By short-circuiting the right cylinder chambers 15a and 15b to reduce the steering force during manual steering operation, and by slowing down the opening/closing control of the control valve 22, changes in the steering force immediately after the pump 10 is activated or stopped are minimized. It is designed to absorb and soften steering shock.

To explain this in detail, 27 in the figure is a pulp body having a pulp hole 28, 29 is a plug that closes the opening of the pulp hole 28, and an annular groove 30 is formed in the pulp hole 28 on the outer periphery of the central part in the axial direction. The valve body 21 is slidably supported, and is constantly biased upward by a spring 31 disposed at one end of the pulp hole 2B, which is the lower end in this example. A pair of passage holes 32a and 32b are bored from the sides of the pulp body 270 so as to face the annular groove 30 when the valve body 2'1 is located at the upper end side of the pulp hole 28. Bypass pipe 20a + from the left and right cylinder chambers 15a and 15b to 32b
20b is connected, thereby both pipes 20a, 20b
1 passage holes 32a, 32b and annular groove 3 of valve body 21
0 to form the bypass path 20.

Further, a recess 21a formed on the upper end side of the valve body 21
The high pressure 1!33 formed by the high pressure side fluid pressure signal path 23 that guides the discharge side fluid pressure of the pump 10 from the pump discharge side conduit 171) is formed in the passage hole 2 formed in the plug body 29.
9a.

Furthermore, the low pressure chamber 34 formed by the recess 21b on the lower end side of the valve body 21 has a passage hole 27 at the bottom of the valve body 27.
A fluid pressure signal path 24 on the low pressure side is connected via a, and this signal path 24 is connected to the tank 12 side via a return pipe 17c, through which fluid pressure on the suction side of the pump 10 is guided.

The fixed throttle 25 and the straddle 26 are provided on one of these fluid pressure signal paths 23 and 24. Note that the annular groove 30 and the depression 21b forming the low pressure chamber 34 are communicated within the valve body 21 via a passage 21c.

In such a configuration, when the pump 10 is stopped, there is no pressure difference between the fluid pressure signal paths 23 and 24.
The valve body 21 has a spring 31 as shown in FIG.
The power cylinder 1 is located on the upper end side of the pulp hole 28 due to the urging force of the bypass passage 20 formed thereby.
No. 5, the left and right cylinder chambers 15a and ISb are short-circuited. Therefore, if a steering operation is performed in this state,
The hydraulic oil in the left and right sill chambers 15a and 15b flows through the bypass passage 20 according to the movement of the piston 16 linked to the steering wheel.
Therefore, there is no problem that the liquid flows to the opposite cylinder chamber or tank 12 side, thereby creating a load that prevents the movement of the piston 16. As a result, the conventional problem of the handle becoming extremely heavy when performing manual steering when the pump 10 is stopped is eliminated, the steering force is reduced, and the handle can be operated properly and reliably.

Furthermore, when the pump 10 is operated and the supply of pressurized oil is started, the fluid pressure is guided to the high pressure chamber 33 through the signal path 23, thereby creating a pressure difference with the low pressure chamber 34 side. When 21 descends against the biasing force of spring 31, K
Become. At this time, the valve body 21 operates slowly due to the presence of the fixed throttle 25 or 26 in the signal path 23, 24, thereby preventing a sudden pressure increase in the left and right cylinder chambers 15a, 15b, and steering control. It functions to reduce sudden changes in force, so-called shock.

Furthermore, as the valve body 21 moves, the annular 1130
A passage hole 32a forming the bypass passage 20.

32t), and the bypass path 20 is cut off.

Therefore, the left and right cylinder chambers 1 of the power cylinder 15
5a and 15b are in a reliably isolated state when the pump is in operation, so that the pressure oil selectively supplied via the control pulp 14 generates a normal steering assist force and reduces the 71 steering operation. It works like this.

Then, when the pump 10 is stopped again, the valve body 21 is returned to its original state by the spring 31, and as a result, the left
A manual steering state is entered in which the right cylinder chambers 1sa and 1sb are short-circuited at the binoculars path 20.

Of course, the movement of the valve body 21 when the pump is stopped is also slow due to the presence of the fixed throttle 25 or 26 in the signal path 23, 24, as described above, and this causes sudden movement in the left and right cylinder chambers 15&, 15b. It functions to suppress the pressure drop, prevent sudden changes in steering force, and reduce steering shock.

Note that the fixed throttle 2 in the fluid pressure signal path 23 and 24 mentioned above
Only one of 5.26 and 5.26 is required, and the throttle amount is set in consideration of the vehicle speed at the time of on/off control of the pump 10, the load depending on the type of vehicle, etc.

Fig. 3 shows another embodiment of the power steering device according to the present invention, and in the figure, the same numbers are given to the parts -1 to 9 or different from those in Fig. 2, and detailed explanation thereof is given. is omitted.

According to this embodiment, the fixed throttle 25 or 26 in the fluid pressure signal path 23, 24, which slows down the movement of the valve body 21 of the control valve 22 to reduce steering shock, is replaced by a variable throttle controlled by the controller 40. It is characterized by the number 41 or 42.

That is, by making the aperture that controls the movement of the valve body 21 flexible, the control is given a degree of freedom and can be adapted to various running conditions. 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 shock, but this is not a problem when driving straight ahead. . At this time, the aperture amount may be set small or zero.

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

Hikoo, in the embodiment shown in FIG.
, 40 may be used as the same controller.

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 valve body that senses the drawn fluid pressure and operates to shut off this bypass path is provided, and a throttle 9 is provided in the fluid pressure signal path for operating the valve body of this control valve. Therefore, despite the simple configuration, when the pump is controlled on and off, the valve body of the control valve is operated gently to isolate and communicate the two cylinder chambers, which reduces the steering force. It can prevent sudden changes and reduce steering shock. Also,
When the pump is operating, the control valve works to reliably isolate both cylinder chambers, and the pressurized fluid selectively supplied to each cylinder chamber generates an appropriate and reliable steering assist force.
A light steering operation can be performed, and when the pump is stopped, both cylinder chambers are short-circuited to remove the load that impedes the movement of the piston, reducing the steering force and allowing proper manual steering.

Furthermore, by making the aperture that controls the movement of the control valve's valve body variable, it is possible to perform appropriate and reliable control according to various driving conditions9, thereby making the steering feel more appropriate. It can be made into something.

By using the above-mentioned power steering device according to the present invention, the pump is operated when the vehicle is running at low speed, and the pump is stopped when the vehicle is running at high speed, thereby reducing the consumption of fuel by driving the pump without interfering with steering performance. It is possible to reduce the horsepower to the minimum necessary and achieve energy saving effects.

Further, according to the present invention, since a control valve having a structure that can open and close the bypass passage with a single valve body is used, the structure is simple, the operational reliability is high, and mass production is possible. It has the advantage of being excellent in terms of performance and being inexpensive.

[Brief explanation of the drawing]

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... Bon, ', 11... Motor, 12...
...Tank, 13...Controller, 15...
- Power cylinder, 15a, 15b... left and right cylinder chambers, 16... piston, 20... bypass passage, 21... valve body, 22... control valve, 23.
24...Fluid pressure signal path, 25°26...Fixed throttle, 40...Controller, 41.42...Fine throttle. Patent applicant Masaki Yamakawa (#υ・1 person) Agent for Jidosha Kiki Co., Ltd.

Claims (2)

[Claims] (1) Steering assist force is achieved by a pump that is activated as needed 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. A control valve is provided with a power cylinder that generates power, a bypass passage that connects the left and right cylinder chambers of this power cylinder, and a control valve that is provided in this bypass passage and has a valve body that connects this bypass passage when the pump is operated. The control valve guides the discharge side fluid pressure and the suction body pressure of the pump to both ends of the valve body in the direction of movement, and has a fluid pressure signal path, and a throttle is disposed in the middle of this fluid pressure signal path. A power steering device that is designated as **. (2) A pump that is activated as needed 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. The control valve includes a power cylinder, a bypass passage connecting the left and right cylinder chambers of the power cylinder, and a control valve having a valve body provided in the bypass passage and connecting the bypass passage when the pump is operated. The valve has a fluid pressure signal path that guides the discharge side fluid pressure and suction side fluid pressure of the pump at both ends in the direction of movement of the valve body, and a variable pressure signal path that is controlled by the controller is located in the middle of this fluid pressure signal path. A power steering device characterized in that a throttle 9 is provided.