JPS6145581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering force control device for a power steering device.

BACKGROUND ART Conventionally, as a steering force control device for a power steering device, there are two means for increasing the steering force in accordance with vehicle speed (hereinafter, they will be described as a first means and a second means).

First means: This means reduces the flow rate supplied to the power steering device in accordance with an increase in vehicle speed, and increases the steering force by utilizing the characteristics of the control valve of the power steering device itself.

Specifically, a pump that has the function of reducing the amount of pressurized fluid supplied to the power steering device by increasing the vehicle speed by more than a predetermined value, or more simply by increasing the engine speed by more than a predetermined value. When driving at low speeds, sufficient flow is supplied to the power steering device so that the power steering device has sufficient output to provide easy steering operation, while when driving at high speeds, the flow is reduced and the power steering device The output of the extraction device is suppressed,
This allows for moderately heavy and stable steering operation.

A method of bypassing the cylinder passage of the power steering device is also a type of this first means.

Second means: providing a hydraulic reaction chamber in the power steering device,
This means to increase the pressure supplied there according to the vehicle speed to increase the steering force.

However, each of the above two means had the following drawbacks. That is, since the first means utilizes changes in valve characteristics due to changes in flow rate, the characteristics are similar to those of the fifth means.
As shown in the figure, the change in steering force due to vehicle speed is large in the range where the output is relatively small (a in Figure 5).
is large), and as the output increases, the change in steering force due to vehicle speed becomes small (b in FIG. 5 is small).
Therefore, when changing lanes on a highway (when using low output), the steering force is heavy and gives a sense of stability, but when driving on a winding road at high speed (when using high output), the steering force is heavy. There will be little sense of increase, and a sense of stability will be lacking.

In other words, the operating source of the power steering device is the pressure of the pressure fluid, so even if the flow rate is reduced during high-speed running, the supply pressure may become high depending on the operating state of the power steering device. Under these conditions, sufficient power is generated with a steering force that is not much different from that when driving at low speeds, and as a result, the steering force at high speeds becomes too light, giving the driver a sense of anxiety, and especially when the above functions are Many of the pumps have
An increase in the supply fluid pressure will tend to increase the supply rate thereby further exacerbating the above disadvantages. On the other hand, the second means changes the steering force by applying pressure to the hydraulic reaction force chamber, so its characteristics are as shown in FIG. Although the change is large (d in Figure 6 is large), it is small in the small output range (c in Figure 6 is small).
A sufficient sense of stability cannot be expected when changing lanes on a highway.

The present invention solves both the drawbacks of the first means having a small change in steering force when the output is large and the second means having a small change in the steering force when the output is small. or, more simply, by using a pump that has the function of reducing the amount of pressure fluid supplied to the power steering device by increasing the engine speed by more than a predetermined value, the engine speed is increased by more than a predetermined value. By making it possible to introduce the pressure in the supply passage, which increases due to the operation of the steering device, into the hydraulic reaction chamber of the power steering device, even if the pressure in the supply passage becomes high during high-speed driving, and Even if this pressure causes the pump to increase the supply flow rate and increase the output of the power steering device, the same high pressure introduced into the hydraulic reaction chamber causes a steering reaction to occur on the steering wheel. Steering force control of the power steering system that applies a large amount of force to the vehicle, which allows for large changes in steering force depending on vehicle speed over the entire output range, ensuring stable and comfortable steering operation when driving at any high speed. It provides equipment.

The present invention will be described below with reference to the illustrated embodiments.
In FIG. 1, 1 is a conventionally known pump driven by an engine (not shown), 2 is a conventionally known power steering device connected to the discharge side of this pump via a conduit 3, and the pump 1 is powered by a conventional power steering device. For example, as shown in FIG. 3, the amount of pressure fluid supplied to the steering device 2 is set to decrease as the engine speed increases beyond a predetermined value. Furthermore, pump 1
The type of pump may be one that has the function of reducing the amount supplied to the power steering device 1 by increasing the engine speed by a predetermined value or more; for example, it may reduce the pump discharge amount itself; Even if the amount increases, part of the discharged amount may be recirculated to the tank side, thereby reducing the amount supplied to the power steering device 1. Furthermore, the discharge side of the power steering device 2 is connected via a conduit 4 to a tank 5 .

6 is an orifice provided in the middle of the conduit 3, and 7 is the hydraulic reaction chamber of the power steering device 2, depending on the pressure difference before and after the orifice 6. A flow path switching valve that is connected to
are slidably and tightly fitted to define chambers 9 and 10 at the front and rear thereof, one chamber 9 is connected to the conduit 3 upstream of the orifice 6 via a conduit 11, and the other chamber 1 is connected to the conduit 3 upstream of the orifice 6.
0 is connected via a conduit 12 to a conduit 3 downstream of the orifice 6 thereof. Also, chamber 10 on the low pressure side
A spring 13 is housed inside, and the resiliency of the spring 13 normally holds the spool 7 in the position shown.

Further, an annular groove 14 is carved on the outer periphery of the spool 8, and two annular grooves 16 and 17 are carved on the inner peripheral surface of the hole 15 into which the spool 8 is fitted. 8 to the chamber 9 on the high pressure side, and the other annular groove 17 connects via a conduit 19 to the conduit 4 on the tank 5 side.
They are connected to each other so that they can communicate with each other at all times.
Further, a port 20 is formed in the main body of the flow path switching valve 7 between the pair of annular grooves 16 and 17 and is always open in the annular groove 14, and this port 20 and the hydraulic reaction chamber ( (not shown) and the conduit 21
are connected via. The width of the annular groove 14 of the spool 8 is set to be approximately the same or slightly narrower than the width of the land portion 22 between the pair of annular grooves 16 and 17, and the annular grooves 14 and 16 are set to be approximately the same or slightly narrower in the illustrated position of the spool. superimposed on each other, the hydraulic reaction chambers communicate with the supply conduit 3 via the conduit 21, the port 20, the annular grooves 14, 16, the internal passage 18, the chamber 9 and the conduit 11, while the downward flow of the spool 8 During displacement, the annular grooves 14 and 17 overlap each other to connect the hydraulic reaction chamber to the conduit 21, the port 20, and the annular groove 1.
4, 17 and a conduit 19 to allow communication with the conduit 4 on the tank 5 side.

Further, the main body of the flow path switching valve 7 is provided with a locking device 23 that restrains the spool 8 and holds it so that it does not displace when the power steering device 2 is operated. That is, 24 is a hole formed in a direction perpendicular to the hole 15 so as to communicate with the annular groove 17, and 25 is a plunger that is slidably and tightly fitted into this hole 24, and the tip of this plunger 25 is connected to the spool 8.
The spool 8 is opposed to the outer circumferential surface of the spool 8, and when it moves to the left, it comes into contact with the outer circumferential surface of the spool 8 and can restrain the spool 8. 26, 27
is a chamber defined by the plunger 25, and a spring 28 is housed in the chamber 26 on the spool 8 side, and the elastic force of the spring 28 normally holds the plunger 25 in a position where it does not come into contact with the spool 8. ing.
On the other hand, the chamber 27 on the other side is connected to the supply side conduit 3 via a conduit 29, and when the pressure inside the conduit 3, that is, the chamber 27 exceeds a predetermined value, the plunger 25 is moved to the left against the spring 28. I'm trying to make it possible for them to do so.

With the above configuration, when the engine speed is low, that is, when the vehicle is generally running at low speed, the amount of supply supplied from the pump 1 to the power steering device 2 is reduced, as can be understood from FIG. Therefore, since the pressure difference between the front and rear of the orifice 6 is large, the pressure difference between the chambers 9 and 10, which are connected to the front and rear of the orifice 6 via the conduits 11 and 12, also becomes large, and the spool 8 is forced into the spring 13. It is resisted and displaced downward. Then, as mentioned above, the annular groove 1
4 and 17 overlap with each other to connect the hydraulic reaction chamber of the power steering device 2 to the conduit 4 on the tank 5 side, so that no fluid reaction force is introduced into the hydraulic reaction chamber. Therefore, even if the fluid pressure in the supply side conduit 3 increases by operating the power steering device in this state, this pressure will not be introduced into the hydraulic reaction force chamber, so that the steering resistance will be reduced. This makes it possible to perform light steering when driving at low speeds. The relationship between the oil pressure in the conduit 3 and the steering force at this time is shown by characteristic curve A in FIG. 4.

Next, when the engine speed is high, that is, when the vehicle is generally running at high speed, the amount of pressure fluid supplied from the pump 1 to the power steering device 2 decreases, so there is a pressure difference before and after the orifice 6. That is, the pressure difference between the chambers 9 and 10 becomes smaller, and the spool 8 is displaced upward by the elastic force of the spring 13, causing the annular groove 14 to overlap the annular groove 16. As a result, the hydraulic reaction force chamber is communicated with the supply side conduit 3, so that fluid pressure is introduced into the hydraulic reaction force chamber. If the power steering device 2 is operated in this state, the fluid pressure in the supply conduit 3 will rise, and this pressure will be introduced into the hydraulic reaction force chamber, increasing the steering reaction force (see the curve in Figure 4). (See B) Therefore, it is possible to perform appropriately heavy and stable steering during high-speed running with low steering resistance. At this time, as described above, most of the pump 1 is connected to the supply side conduit 3.
When the fluid pressure inside increases, the supply amount increases, which increases the pressure difference before and after the orifice 6 and attempts to displace the spool 8 downward. However, in this embodiment, the pump 1 is on the supply side. The supply amount is increased by increasing the fluid pressure in the conduit 3, and then this increase in supply amount increases the pressure difference across the orifice 6, and this increase in pressure causes the spool 8 to start displacing. Before the time elapses, the chamber 27 communicating with the conduit 3
The plunger 25 immediately moves to the left against the spring 28 due to the increase in pressure inside the pump, and the spool 8 is restrained. Therefore, even if the pump 1 increases the flow rate, the spool 8 cannot be displaced. The hydraulic pressure in the supply conduit 3 continues to be introduced into the hydraulic reaction chamber. Incidentally, since the pressure increase in the conduit 3 due to the operation of the power steering device 2 is substantially equal before and after the orifice 6, there is no possibility that the spool 8 will be displaced due to the pressure increase.

By the way, as clarified in the above explanation, the meaning of using a pump with a flow rate characteristic as shown in FIG. 3, which reduces the supply flow rate as the vehicle speed increases, and providing a flow path switching valve. The purpose of this is to utilize both the change in steering force caused by a change in flow rate and the change in steering force caused by a change in the supply pressure to the reaction force chamber.
The characteristics exhibited by such a configuration are shown in FIG.

First, as described above, in the conventional steering force control device for a power steering device that does not include the flow path switching valve 7, the engine speed is high and the amount of pressure fluid supplied from the pump to the power steering device is small. When the power steering device 2 is operated in this state, that is, when it corresponds to the first means, the conduit 3 due to the operation of the power steering device 2 is
Even if it shows good characteristics according to the difference in the supply amount in a region where the pressure rise within is small, as the pressure rise increases, the output of the power steering device 2 also decreases as the pressure rises, i.e., the supply amount increases. Moreover, the increase in pressure increases the flow rate, causing a sense of uneasiness as the steering force becomes too light, and the steering force suddenly becomes lighter during steering, while the hydraulic reaction force When using the second means of increasing the steering force by providing a chamber and increasing the pressure supplied therein according to the vehicle speed, as shown in characteristic curve D in FIG. 4, when the engine is running at high speed and the output is small, For example, when driving at high speed on a highway, the steering force when changing lanes becomes too light, giving a sense of uneasiness.

However, in the present invention, the flow rate supplied to the power steering device is reduced in accordance with the vehicle speed to increase the steering force, so the steering force is light when changing lanes when driving at high speeds with little steering resistance. You can eliminate the excessive feeling of anxiety (e in Figure 4 is large), and the conduit 3
Even if the output of the power steering device 2 increases due to an increase in the pressure within the power steering device 2, as described above, the increased pressure is introduced into the hydraulic reaction chamber of the power steering device 2, and the pressure increase causes the pump 1 to increase. Even if the flow rate is increased to switch the flow path of the flow path switching valve 7, the locking device 23 restricts the operation of the flow path switching valve 7, so that the hydraulic reaction force chamber In addition to being able to continuously apply pressure to the steering wheel, it is also possible to secure a large steering force even at high speeds where there is a lot of steering resistance, such as when driving at high speed on a winding road. A sense of stability can be obtained (f in Fig. 4 is large). In other words, it is clear that the steering force is large and a stable steering feeling can be obtained over the entire output range.

Furthermore, in the transition period when the annular groove 14 overlaps with the annular groove 17 and overlaps with the annular groove 16, the width of the annular groove 14 is changed between the annular grooves 16 and 16.
Since the width of the land portion 22 between the annular grooves 17 and 17 is approximately the same or slightly narrower, the hydraulic reaction force chamber
4, 17 to the tank 5, it gradually becomes connected to the supply side conduit 3 via the annular groove 16, and the steering reaction force can be smoothly increased.

Next, FIG. 2 shows another embodiment of the present invention. In this embodiment, the high pressure side chamber 9 of the flow path switching valve 7 is connected to the middle of the conduit 3, and the chamber 9 is used for supplying pressure fluid. It is constructed as part of the passage. And conduit 3
The upstream side of is directly connected to the chamber 9, and the downstream side thereof is connected to the chamber 9 through a port 30 that opens on the inner peripheral surface of the hole 15. A kind of variable orifice 31
It consists of Note that the other configurations are similar to those of the above embodiment, and the same or identical parts are denoted by the same reference numerals.

In such a configuration, the spool 8 moves forward and backward in the vertical direction in FIG. 2 in response to increases and decreases in the supply flow rate from the pump 1, and operates to keep the pressure difference across the variable orifice 31 substantially constant at all times. , the pressure loss can be reduced compared to that of the above embodiment in which the fixed orifice 3 is provided. The spool 8 moves forward and backward in response to increases and decreases in the supply flow rate, thereby switchingly connecting the hydraulic reaction force chamber to the supply side flow path or the tank 5 side, so that the same effects as in the above embodiment can be obtained.

In each of the above embodiments, the annular groove 16 is connected to the supply conduit 3 via the internal passage 18 formed in the spool 8, but as shown by the dotted line in FIGS. It may also be connected directly to the conduit 3 via the conduit 32. In this case, if the conduit 32 is connected to the upstream side of the orifices 6, 31, in addition to the pressure increase due to the operation of the power steering device 2, the pressure generated by the orifices 6, 31 can also be absorbed by the hydraulic reaction force. Although it is preferable because it can be introduced into the room, it is not necessarily limited to this. Furthermore, in the above embodiment, the supply amount is reduced when the engine speed increases beyond a predetermined value, but if the speed of the vehicle is detected and the supply amount is reduced when the vehicle speed increases beyond a predetermined value. , it is clear that more ideal steering characteristics can be obtained.

As described above, the present invention is provided with a flow path switching valve that can switch and connect the hydraulic reaction chamber of the power steering device to the tank side or the supply side passage in accordance with an increase or decrease in the supply amount, and When the pressure exceeds a predetermined value, the locking device restricts the operation of the flow path switching valve, so when running at high speed with a small supply amount, the pressure in the supply side passage is reduced in the hydraulic reaction chamber. In addition, even if the supply flow rate changes in this state, the locking device allows the above-mentioned locking device to continue this state, and therefore it is possible to ensure a moderately heavy steering force required during high-speed running. You can get the effect that you can.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention with main parts cut away; Fig. 2 is a system diagram showing another embodiment; Fig. 3 is a characteristic curve diagram showing the flow rate characteristics of the pump;
The figure is a characteristic curve diagram showing a comparison of the steering force characteristics of the device of the present invention and the conventional device. Figures 5 and 6 are characteristic curve diagrams showing the respective steering force characteristics of the first means and the second means in the conventional device. It is. 1... Pump, 2... Power steering device, 3, 4...
... Conduit, 5 ... Tank, 7 ... Flow path switching valve, 23
...Locking device.

Claims (1)

[Claims] 1. A steering force control device for a power steering device comprising a pump that reduces the supply flow rate when the vehicle speed or engine rotational speed increases by a predetermined value or more, and a power steering device connected to the pump via a supply passage,
The hydraulic reaction chamber of the power steering device is controlled to move forward or backward according to the increase or decrease of the supply flow rate, and the hydraulic reaction chamber of the power steering device is supplied to the tank side passage in the position when the supply volume increases, and the hydraulic reaction force chamber is supplied to the tank side passage when the supply volume decreases. A flow path switching valve is provided which is selectively connected to each of the passages, and a locking device is provided which restrains the operation of the flow path switching valve when the pressure within the supply passage exceeds a predetermined value. Steering force control device for power steering device.