JPS6145580B2 - - 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 is used that has the function of reducing the amount of pressure fluid supplied to the power steering device as the engine speed increases beyond 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 enable easy steering operation, while when driving at high speeds, the flow is reduced to reduce the output of the power steering device. 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 the same as those of the seventh 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 7).
is large), and as the output increases, the change in steering force due to vehicle speed becomes small (b in FIG. 7 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 output 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 when driving at high speeds becomes too light, giving the driver a sense of anxiety. On the other hand, the second
Since the means changes the steering force by applying pressure to the hydraulic reaction force chamber, its characteristics are as shown in Fig. 8.Contrary to the case of the first means, the change in steering force due to vehicle speed is large in the range of large output. (d in Figure 8)
is large), and in a small output range, it is small (c in Fig. 8 is small), and a sufficient sense of stability cannot be expected when changing lanes on an expressway.

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, Even if the output of the power steering device is increased, in this case, the same high pressure introduced into the hydraulic reaction chamber will apply a steering reaction force to the steering wheel, thereby increasing the entire range of output. To provide a steering force control device for a power steering device, which has a large change in steering force depending on vehicle speed over a period of time and can ensure stable and comfortable steering operation during any high-speed running.

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. 2, 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 2 by increasing the engine speed by a predetermined value or more; for example, it may reduce the pump's 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 2. 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 8 at 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.

Furthermore, 23 is a bypass pipe that communicates the upstream side and the downstream side of the orifice 6, and a control mechanism 24 is provided in the middle of this bypass pipe 23 to control the opening and closing of the bypass pipe 23.
has been established. This control mechanism 24 has its main body 25
A plunger 26 slidably fitted inside the plunger 26, a chamber 27 formed at the lower end of the plunger 26, and a pair of ports 28 and 29 that communicate the chamber 27 with the upstream and downstream sides of the bypass pipe 23. The plunger 26 is normally urged downward by the elastic force of the spring 30, and the plunger 26 is normally urged downward by the elastic force of the spring 30, and the lower end surface of the plunger 26 is biased downwardly by the elastic force of the spring 30.
9 is closed to block communication with the bypass pipe 23. Further, 31 is a solenoid coil that urges the plunger 26 upward when energized and opens the opening of the port 29 to communicate the bypass pipe 23, and 32 is a sensor that detects the shift position of the gear change lever 34 of the transmission 33. This detector 32 is
In the illustrated embodiment, the coil 31 is connected to the battery 35 when the gear change lever 34 is shifted to the third and fourth gear positions.

By the way, as clarified in the above explanation, the meaning of using a pump with a flow rate characteristic as shown in Figure 2, which reduces the supply flow rate as the vehicle speed increases, and having a configuration in which a flow path switching valve is provided. The purpose of this method is to utilize both the change in steering force due to a change in flow rate and the change in steering force due to a change in the supply pressure to the reaction force chamber.
To explain this point with reference to FIG. 3 showing the relationship between the internal pressure of the supply side conduit 3 and the steering force, when the gear shift lever 34 is located at the 1st and 2nd gear shift positions, that is, when the vehicle is running at low speed. At times, the coil 31 of the control mechanism 24 is not energized, the bypass pipe 23 is closed and all of the supply flow from the pump 1 flows through the orifice 6. At this time, for example, when accelerating or climbing a hill, the engine speed may be high despite driving at low speed, and therefore, as shown in FIG. The supply flow rate increases or decreases. However, if the flow path area of the orifice 6 is set appropriately, it is possible to generate a sufficient pressure difference across the orifice 6 even when the supply flow rate is reduced, and the pressure before and after the orifice is adjusted to the conduit 11, respectively. , 12 into the chambers 9, 10, the spool 8 is displaced downward against the spring 13. That is, when the shift lever 34 is positioned at a shift position other than 3rd or 4th speed, the spool 8 is always held at the lower sliding end position regardless of the engine speed.

In this state, as described above, the annular grooves 14 and 17 overlap each other and communicate the hydraulic reaction chamber of the power steering device 2 with the conduit 4 on the tank 5 side. No pressure is introduced. In this case, when the engine speed is low and a sufficient flow rate is supplied to the power steering device 2, a large output of the power steering device 2 can be easily obtained. As can be understood from the characteristic curve A, the steering wheel can be operated easily over the entire output range. On the other hand, the gear change lever 34 is shifted to 1st and 2nd speeds as described above, but when the engine speed is high and the amount of power supplied to the power steering device 2 is reduced, that is, when accelerating or climbing a slope, In such cases, the disadvantages of conventional steering force control devices can be used as advantages. In other words, in this case, the characteristic curve B in FIG.
As shown in (), in a region where the pressure increase in the conduit 3 due to the operation of the power steering device 2 is small, that is, in a region where the output is small, the steering force is However, if a higher output is required and the pressure inside the conduit 3 increases, the power steering device 2 requires a large supply amount, as described as a disadvantage of the conventional device. As in the case, sufficient output is generated, so in this case as well, the above curve A
As with the case, you will be able to perform light steering operations. Furthermore, in the vehicle state as in the case of curve B, there is virtually no difference from the case in curve A since the vehicle is used in a large output range in most cases.

Next, when the speed change lever 34 is shifted to the third or fourth speed, the coil 31 of the control mechanism 24 is energized by the detector 32 that detects this, and the plunger 26 is pulled up against the spring 30. The bypass pipe 23 is brought into communication. Then, most of the pressure fluid from the pump 1 flows through the bypass pipe 23 and is supplied to the power steering device 2, so the pressure difference before and after the orifice 6 becomes extremely small. It is returned to the illustrated position by the elastic force of , and the hydraulic reaction force chamber is communicated with the supply side conduit 3 . When the power steering device 2 is operated in this state, the pressure within the supply conduit 3 increases, and this pressure is introduced into the hydraulic reaction force chamber. At this time, when the pressure inside the conduit 3 increases, the output of the power steering device increases regardless of the magnitude of the supply amount as described above, but the increased pressure enters the hydraulic reaction chamber of the power steering device 2. 3, it is possible to obtain a large steering reaction force as shown by the characteristic curve C or C' in FIG.

Among these characteristic curves, curve C is for when the transmission gear is 3rd or 4th gear and the engine speed is low, but in actual vehicle use, it is used just before stopping when braking, and steering is rarely done in this state. impossible. On the other hand, curve C' is when the transmission gear is 3rd or 4th gear and the engine speed is high, which corresponds to high-speed driving conditions, where the steering force is large over the entire output range and a stable steering feel can be obtained.

However, in this embodiment, the flow path area of the port 29 is set to an appropriate size, and the port 29 is
If this is used as an orifice passage, the steering force can be controlled in accordance with the engine speed when the speed change lever 34 is shifted to 3rd or 4th speed, and a better steering feeling can be obtained. That is, the operation when the gear shift lever 34 is shifted to a shift position other than 3rd or 4th gear is the same as described above, but when shifted to 3rd or 4th gear, the pressure fluid from the pump 1 is has two orifices, namely orifice 6 and port 29.
The pressure difference between the two orifices becomes relatively small compared to the case where the entire amount flows through a single orifice 6. At this time, as shown in FIG. 4, the pressure difference obtained by the single orifice 6 when the supply amount is small (see curve a) and the pressure difference obtained by the two orifices 6 and 29 when the supply amount is large. If the pressure difference (see curve b) between Unlike the above embodiment, when the pressure difference is reached, the pressure difference makes it possible to displace the spool 8 to the position shown in the figure and connect the hydraulic reaction chamber to the tank side conduit 4. Power steering device 2
Even if the pressure in the supply side conduit 3 increases by operating the pump, this pressure will not be introduced into the hydraulic reaction force chamber, thus making it possible to operate the handle easily. When the state shifts to high-speed running, the pressure difference across the orifice decreases due to a decrease in the supply amount, as shown by curve b in FIG. 4, so the spool 8 is displaced upward by the spring 13 and The same effect as when the bypass pipe 23 is opened is obtained, and due to the displacement of the spool 8 at this time, during the transition period when the annular groove 14 overlaps with the annular groove 17, it overlaps with the annular groove 16. Since the width of the annular groove 14 is set to be approximately equal to or slightly narrower than the width of the land portion 22 between the annular grooves 16 and 17, the hydraulic reaction force chamber is connected to the tank 5 via the annular grooves 14 and 17. From the state in which it is in communication with the supply-side conduit 3 through the annular groove 16, the steering reaction force can be smoothly increased.

Furthermore, as described above, the gear shift lever 34 is
When the spool 8 is controlled to move forward or backward by increasing or decreasing the supply amount in the shift position of 1st or 4th gear, depending on the type of pump 1, when the discharge pressure, that is, the pressure in the supply conduit 3 increases, the engine Even if the supply amount is reduced due to high rotation, the pressure increase may increase the supply amount, so when using such a pump 1,
As shown in FIG. 1, it is preferable to provide a locking device 36 that restrains the spool 8 and holds it so that it does not displace when the pressure inside the conduit 3 exceeds a predetermined value.

That is, 37 is a hole formed in a direction perpendicular to the hole 15 and communicated with the annular groove 17, 38 is a plunger that is slidably and tightly fitted into the hole 37, and the tip of the plunger 38 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. 39,40
is a chamber defined by the plunger 38, and a spring 41 is housed in the chamber 39 on the spool 8 side, and the elastic force of the spring 41 normally holds the plunger 38 in a position where it does not come into contact with the spool 8. ing.
On the other hand, the chamber 40 on the other side is communicated with the supply side conduit 3 via a conduit 42, and when the pressure inside the conduit 3, that is, the chamber 40 exceeds a predetermined value, the plunger 38 is moved to the left against the spring 41. I'm trying to make it possible for them to do so.

Therefore, when the gear shift lever 34 is shifted to 3rd or 4th gear and the engine speed is high, that is, when driving at high speed, the spool 8 is displaced upward, and the hydraulic reaction force The chamber communicates with the supply conduit 3. When the power steering device 2 is operated in this state, the pressure inside the conduit 3 increases, and this pressure is introduced into the hydraulic reaction chamber and simultaneously acts on the pump 1, as described above.
Depending on the type of pump 1, the feed rate may be increased. As a result, the pressure difference before and after the orifice 6 increases and the spool 8 tries to be displaced downward, but since the locking device 36 is provided, the pump 1 is prevented from increasing the fluid pressure in the supply conduit 3. Therefore, the supply amount is increased, and then the pressure difference across the orifice 6 increases due to the increase in the supply amount, and before the spool 8 starts to be displaced due to this increase in pressure difference, the above-mentioned conduit 3
The plunger 38 immediately moves to the left against the spring 41 due to the pressure increase in the chamber 40 communicating with the pump 1, and the spool 8 is restrained. Therefore, the spool 8 cannot be displaced even if the flow rate of the pump 1 is increased. figure,
Therefore, since the hydraulic pressure in the supply conduit 3 continues to be introduced into the hydraulic reaction force chamber, a heavy and stable steering force can be ensured during high-speed running.

Note that instead of detecting the shift position, the actual vehicle speed may be detected, and the coil 31 of the control mechanism 24 may be energized when the vehicle speed exceeds a predetermined value.

Next, FIG. 5 shows a modification of the embodiment shown in FIG. 1. In the embodiment shown in FIG. The pressure difference before and after the pressure is adjusted. In this embodiment, a variable orifice 43 is provided in the middle of the conduit 3, and while the entire amount of supply is flowing through this variable orifice, the flow area is controlled by the control mechanism 24. This makes it possible to adjust the pressure difference. Therefore, in this embodiment, there is no member corresponding to the bypass pipe 23 described above. The variable orifice 43 includes a needle-like member 44 protruding from the lower end of the plunger 26 of the control mechanism 24 and the port 29. When the plunger 26 is moved downward by the spring 30, the needle-like member 44 is located in the port 29 to narrow down the flow path area, and the coil 31 is energized and the plunger 2
6 is pulled upward and the needle-like member 44 is pulled out from the port 29, a large flow area can be secured. Note that the other configurations are the same as in FIG. 1.

Furthermore, FIG. 6 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 configured as a part of the pressure fluid supply passage. The upstream side of the conduit 3 is directly connected to the inside of the chamber 9, and the downstream side is connected to the inside of the chamber 9 through a port 45 that opens on the inner peripheral surface of the hole 15.
and spool 8, a kind of variable orifice 4
6. 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 up and down in accordance with the increase/decrease in the supply flow rate from the pump 1, and operates to keep the pressure difference across the variable orifice 46 substantially constant at all times. Pressure loss can be reduced compared to those provided with a fixed orifice 6 or a variable orifice 43. When the entire amount of pressure fluid from the pump 1 is flowing, the spool 8 is displaced downward even when the engine speeds up and the flow rate is reduced, and the hydraulic reaction chamber is connected to the tank side conduit. 4, and on the other hand, when the speed change lever 34 is shifted to 3rd or 4th speed, the bypass pipe 23 is communicated, and most of the pressure fluid from the pump 1 flows through the bypass pipe 32, the upper , and connects the hydraulic reaction force chamber to the supply side conduit 3.
It is possible to obtain the same effect as the embodiment shown in FIGS.

In addition, in the embodiment shown in FIGS. 5 and 6 above, in the same way as explained in the embodiment shown in FIG.
Of course, the port 29 may be used as an orifice passage, a locking device 36 may be provided, or the control mechanism 24 may be actuated by the speed of the vehicle.

Further, in all 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. 1 and 6, It may also be connected directly to the conduit 3 via the conduit 47. In this case, if the conduit 47 is connected to the upstream side of the orifices 6, 43, 46, in addition to the pressure increase due to the operation of the power steering device 2, the orifices 6, 43, 46
3 and 46 can also be introduced into the hydraulic reaction chamber, which is preferable, but is not necessarily limited to this.

As described above, the present invention enables the hydraulic reaction chamber of the power steering device to be switched and connected to the tank side or the supply side passage according to the increase/decrease of the supply amount, and the supply amount can be changed depending on the shift position or vehicle speed. The switching timing can be controlled by making adjustments, or the switching timing can be controlled by adjusting the pressure difference before and after the orifice, and adjusting the flow path area of the orifice depending on the shift position or vehicle speed. Therefore, it is possible to expect the effect of being able to obtain a steering force suitable for the speed of the vehicle.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an embodiment of the present invention with main parts in cross section; Fig. 2 is a characteristic curve diagram showing the flow rate characteristics of the pump; Fig. 3 is a characteristic curve diagram showing the characteristics of the steering force; FIG. 4 is a characteristic curve diagram showing changes in the pressure difference before and after the orifice due to the operation of the control mechanism, FIG. 5 is a sectional view showing the main part of another embodiment of the present invention, and FIG. 7 and 8 are system diagrams showing main parts in cross section showing the embodiment.
It is a characteristic curve diagram showing the steering force characteristics of each of the means and the second means. 1... Pump, 2... Power steering device, 3, 4...
... Conduit, 5 ... Tank, 6, 43, 46 ... Orifice, 7 ... Flow path switching valve, 23 ... Bypass pipe, 24 ... Control mechanism, 29 ... Port, 34 ...
...Shift lever.

Claims (1)

[Scope of Claims] 1. Steering force control of a power steering device comprising a pump that reduces the supply flow rate when the engine speed increases beyond a predetermined value, and a power steering device connected to the pump via a supply passage. The device is controlled to move forward or backward according to the increase or decrease in the supply flow rate, and the hydraulic reaction chamber of the power steering device is connected to the tank side passage in the position when the supply amount increases, and the hydraulic reaction force chamber is connected to the tank side passage in the position when the supply amount decreases. a flow path switching valve that selectively connects the flow path to the supply passage, and a portion of the supply flow rate that acts on the flow path switching valve in response to a specific shift position of the gear shift lever of the transmission or an increase in vehicle speed exceeding a predetermined value. A steering force control device for a power steering device, comprising: a control mechanism for bypassing the power steering device to the power steering device. 2. A steering force control device for a power steering device comprising a pump that reduces the supply flow rate when the engine speed increases beyond a predetermined value, and a power steering device connected to the pump via a supply passage, wherein the supply passage An orifice is installed in the middle of the orifice, and the movement is controlled according to the pressure difference before and after the orifice. When the pressure difference increases, the hydraulic reaction chamber of the power steering device is placed in the tank side passage, and when the pressure difference decreases, the hydraulic reaction chamber of the power steering device is placed in the tank side passage. a flow path switching valve that selectively connects the hydraulic reaction chamber to the supply passage at each position, and a flow path area of the orifice that changes the flow path area of the orifice according to a specific shift position of the gear shift lever of the transmission or an increase in vehicle speed beyond a predetermined value. 1. A steering force control device for a power steering device, characterized in that a control mechanism for increasing the steering force is provided.