JPS609098Y2 - Steering force control device in power steering device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a steering force control device in a power steering system, and particularly to a steering force control device that improves the feeling of steering during high-speed running.

Conventional power steering devices have been developed with a focus on reducing the steering force of the driver.

However, in driving, it is desirable to obtain a steering sensation that corresponds to road resistance, and conventionally, a reaction chamber has been provided in the servo mechanism to feed back the force generated by the operating hydraulic pressure as a steering reaction force. ing.

However, in this case, the reaction force is proportional only to the steering load and is not directly related to the vehicle speed.

Therefore, there is a drawback that the feeling is deteriorated especially when driving at high speeds, giving the driver a great sense of anxiety.

Furthermore, the reaction force receiving area in the reaction chamber is adjusted in various ways, and the reaction force is set at a compromise between low speed and high speed, but in order to improve the feeling, the steering force is small at low speed, and the reaction force is set at a compromise between low speed and high speed. It is desirable that it be larger at high speeds.

This idea eliminates the shortcomings of the conventional devices as described above, changes the steering torque at high speeds in accordance with the vehicle speed, improves the steering feel, and makes the steering wheel easier to operate at low speeds, making it ideal. The object of the present invention is to provide a steering force control device that can obtain a steering characteristic that is similar to that of the present invention, improves the stability and responsiveness of its operation, and facilitates the adjustment of reaction characteristics.

To explain an embodiment, in FIG. 1, reference numeral 1 denotes a steering control valve chamber having a well-known steering control valve mechanism, to which fluid from a tank 3 is supplied by a hydraulic pump 2 through a main circuit 4, and a mountain stream circuit. The fluid flows into the tank 3 through the mountain stream.

As is well known, in this type of mechanism, as road resistance increases, the hydraulic pressure in the steering control valve chamber 1 increases to assist the steering torque.

5 is a hydraulic reaction chamber, and when the hydraulic pressure in the steering control valve chamber 1 increases, the hydraulic pressure supplied to the chamber 5 via the main circuit 4 increases.

In the above, the steering force control mechanism 7 is provided in the hydraulic pressure passage 6 that communicates with the main circuit 4 and transmits the hydraulic pressure of the steering control valve chamber 1 to the hydraulic reaction chamber 5.

The steering force control mechanism 7 has a hydraulic passage 8 communicating with the hydraulic passage 6 and the hydraulic reaction chamber 5, and a fixed throttle 9 branching from the passage 8, which is connected to a mountain stream passage 11 to the tank 3. The valve chamber block 12 has a valve chamber block 12 forming a branch passage 10 that communicates with the vehicle, and a vehicle speed sensor pump 13 that is driven by, for example, an output shaft of an automobile transmission and changes the flow rate according to increases and decreases in vehicle speed.

The hydraulic pressure passage 8 is provided with a shutoff control valve 14 that opens and closes the passage 8 by being actuated by a road resistance load and a change in vehicle speed, and a spring 15 that acts in the direction of opening the passage 8 performs shutoff control. The valve 14 is biased in one direction.

At least two throttle valves 16,17 are provided in the branch channel 10.
are provided and the valves 16, 17 are biased in one direction by springs 18, 19, respectively.

One throttle valve 16 is disposed between the fixed throttle 9 of the passage 10 and a hydraulic pressure chamber 20 for applying the hydraulic pressure of the passage 10 to the shutoff control valve 14, and the other throttle valve 17 is Behind the pressure chamber 20, that is, the mountain stream passage 11 of the branch passage 10
The throttle valves 16 and 17 are arranged on the side so that the hydraulic pressure of the vehicle speed sensor pump 13 acts on the throttle valves 16 and 17, and the spring 1
B, 19, when the vehicle speed is zero, the throttle valve 16 is connected to the branch passage 10.
is fully opened, and each valve 16, 17 is energized so that the throttle valve 17 is blocking the passage 10.

On the other hand, the hydraulic pressure generated by the vehicle speed sensor pump 13 is
Each hydraulic chamber 22, 2 of the throttle valve 16, 17 is connected via a passage 21.
3 to counteract the spring force, and the hydraulic pressure in the hydraulic pressure chamber 20 is configured to counteract the biasing spring force of the shutoff control valve 14.

Assuming you operate the steering wheel when the vehicle speed is zero,
Since the vehicle speed sensor pump 13 is not operating, no hydraulic pressure is applied to the two throttle valves 16 and 17. Therefore, the spring force of the setting springs 1B and 19 causes the valve 16 to fully open the passage 10, and the valve 17 to open the passage 10 fully. The passage 10 is blocked.

On the other hand, the steering control valve chamber 1 contains a liquid EEP proportional to the road resistance.
□ is generated and acts on the hydraulic pressure passage 8, increasing the hydraulic pressure in the passage 8, and the hydraulic pressure Pl also acts on the hydraulic pressure chamber 20 via the fixed throttle 99 passage 10.

Note that the fixed throttle 9 is provided to prevent the pressure within the hydraulic pressure passage 8 from decreasing below a certain value.

At this time, if the set spring force of the spring 15 acting on the cutoff control valve 14 is Fa, and the hydraulic pressure acting area of the cutoff control valve 14 is Fa, then the cutoff control valve 14 will not operate until Fa≧P1x Aa.
It does not operate due to the bias of 5, and the hydraulic pressure of P□ also acts on the reaction chamber 5.

When the hydraulic pressure in the hydraulic pressure passage 8 further increases and reaches P2, a pressure of P2x Aa is generated in the hydraulic pressure chamber 20, and Fa(P2x
Aa, the shutoff control valve 14 is moved to the left against its spring 15, and thereby the valve 14 shuts off the hydraulic passage 8.

In other words, since a hydraulic pressure of 22 or more does not act on the reaction chamber 5, the handle operating torque is O P2 in FIG.
It varies along the line of VO.

Therefore, if the set spring force Fa is set to a small value,
The steering wheel operation torque hardly increases and the steering wheel is operated with extremely light force.

When the vehicle is running and the vehicle speed increases to Vl, the vehicle speed sensor pump 13 discharges liquid at a corresponding flow rate, and by providing the fixed throttle 24, a hydraulic pressure P3 corresponding to the vehicle speed is generated in the passage 21. .

Therefore, the hydraulic pressure in the hydraulic pressure chambers 22 and 23 also becomes P3. Throttle valve 1
6's set spring force is Fb, the set spring force of the throttle valve 17 is Fc, the hydraulic pressure acting area of the throttle valve 16 is Ab, and the hydraulic pressure acting area of the throttle valve 17 is Ac, then FC<P3×AC. At that time, the throttle valve 17 starts moving to the left, and similarly Fl)
-CP3xAb, the throttle valve 16 starts moving to the left.

The throttle valves 16 and 17 have a throttle portion 1 between them and the branch passage 10.
6a and 17a, respectively, and each valve 16.17
By moving leftward, the aperture ratio of the aperture portion 16a increases (the opening area decreases), and the aperture ratio of the aperture portion 17a decreases (the aperture area increases).

In this state, when the handle is operated and a hydraulic pressure P proportional to the road resistance acts on the hydraulic passage 8, the set spring force Fa of the cutoff control valve 14 and the hydraulic pressure A acting on the hydraulic chamber 20, A hydraulic pressure of P acts on the reaction chamber 5 until the force AaxP4 generated by AaxP becomes Fa=AaxP, and when the pressure exceeds Fa (Aa x P), the shutoff control valve 14 moves to the left and the liquid The pressure passage 8 is shut off and the hydraulic pressure in the reaction chamber 5 is P.
It will not be higher than 4.

However, depending on the hydraulic pressure of the vehicle speed sensor pump 13, the throttling ratio of the throttle valves 16 and 17 changes as described above.
An increase in the throttling ratio of the throttle valve 17 lowers the pressure acting on the hydraulic chamber 20, and a decrease in the throttling ratio of the throttle valve 17 also works to lower the pressure of the hydraulic chamber 20. Therefore, the following operation is performed. It will be done.

In other words, the relationship between the pressure drop in the throttle part 16a and the flow rate Q is as follows: When the flow coefficient is C9, the fluid density is ρ, and the throttle area is α1, the relationship between the pressure drop in the throttle part 17a and the flow rate Q is as follows: When, P5 is the hydraulic pressure between the throttle valves 16 and 17, that is, the hydraulic pressure chamber 20, P6 is the pressure from the throttle valve 17 to the mountain stream passage 11 side, and the pressure P6 = 0. .

Therefore, α1 becomes smaller.

That is, due to the increase in the throttling rate of the throttle valve 16 (decrease in α□) and the decrease in the throttle rate of the throttle valve 17 (increase in α2), Ps<P
, becomes.

In other words, in the above, a lower hydraulic pressure P5 acts on the shutoff control valve than when the hydraulic pressure P directly acts on the hydraulic pressure chamber 20, so the shutoff control valve 14 is operated in the liquid level passage 8 as described above. Even when the pressure reaches P, the passage 8 remains open, and the passage 8 is activated when the pressure in the hydraulic chamber 20 becomes P5≧P4, that is, the pressure in the hydraulic passage 8 reaches P7.
cut off.

Therefore, a hydraulic pressure P7 higher than P4 acts on the reaction chamber 5, generating a steering reaction force.

If the hydraulic pressure in the hydraulic pressure passage 8 rises more than that, the shutoff control valve 14 shuts off the passage 8, so no hydraulic pressure higher than P7 acts on the reaction chamber 5, and the steering torque decreases. It will change along OP7 Vt in FIG.

When the vehicle speed further increases to V2, the flow rate from the vehicle speed sensor pump 13 further increases, and a higher hydraulic pressure than the above acts on the hydraulic pressure chambers 22 and 23, causing the throttle valves 16 and 17 to
is further moved to the left, the throttle area α□ of the throttle portion 16a decreases and the throttle area α2 of the throttle portion 17a increases compared to when the vehicle speed is V□, and becomes even larger than when P[ is V□.

As this α1 ratio increases, the pressure in the hydraulic chamber 20 further decreases,
The pressure in the hydraulic pressure passage 8 required to operate the cutoff control valve 14 needs to be greater than that at the vehicle speed of V1.

That is, an even greater hydraulic pressure acts on the reaction chamber 5 than when the vehicle speed is V1, and the hydraulic pressure at the porthole is higher than P7 at P8.
Then, the shutoff control valve 14 shuts off the hydraulic pressure passage 8, and the steering torque changes along OP8V2 in FIG.

When the vehicle speed becomes higher than v2, the flow rate from the vehicle speed sensor pump 13 further increases, and the hydraulic pressure chambers 22, 2
3 is made high pressure, the throttle valve 16 finally shuts off the branch passage 10, and the throttle valve 17 fully opens the passage 10.

As a result, the pressure in the hydraulic chamber 20 drops to near zero,
The shutoff control valve 14 leaves the passage 8 open.

Therefore, a hydraulic pressure corresponding to the road resistance load acts directly on the reaction chamber 5, and the steering torque changes along Q-Vmax in FIG. 3.

That is, in FIG. 3, the vehicle speed is zero, Vl, V2. Vm
The steering torque T (vertical axis) at the time of ax is expressed as the road resistance R (
The figures are shown in response to changes in the horizontal axis).

In the figure, 25 is a drain hole of the cutoff control valve 14 section, 26 is a drain hole of the throttle valve 16 and 17 sections, and 27 and 28 are check valves for ensuring the function of the vehicle speed sensor pump 13.

The line 0-MANU in FIG. 3 indicates the relationship between manual steering torque and road resistance when the power steering device is not operating.

By the way, in the steering device of an automobile, the road surface resistance load relative to the steering torque generally decreases as the vehicle is driven at high speed, and therefore, the hydraulic pressure in the hydraulic pressure passage 8 does not become very high when the vehicle is traveling at high speed.

For this reason, in the control mechanism as described above, for example, the third
There may be cases where factors such as the wobbling of the steering wheel when the vehicle is running, which causes Vmax in the figure, cannot be easily resolved.

In such a case, as shown in Figures 1 and 2,
A hydraulic passage 8' between the shutoff control valve 14 and the reaction chamber 5, and an extension passage 21' of the hydraulic passage 21 of the vehicle speed sensor pump 13.
A check valve 30 is provided which is activated by detecting the higher pressure of the hydraulic pressure and supplies the higher hydraulic pressure to the reaction chamber 5.

That is, the check valve 30 normally operates in both passages 8'.
, 21' are opened, and the springs 31 and 32 act in opposite directions to connect both to the reaction chamber 5, and the left chamber 33 of the valve 30 is connected to the hydraulic passage 8' via the pilot passage 34. The right ventricle 35 is connected to the pilot passage 36.
The hydraulic pressure of the hydraulic pressure passage 8' is communicated with the left chamber 33 and the vehicle speed sensor pump 13 is communicated with the right chamber 35 through the extension passage 21'.
Apply the hydraulic pressure generated by

That is, while the hydraulic pressures in the passages 8' and 21' are equal, in other words, while the hydraulic pressure generated by the road resistance load and the hydraulic pressure generated by the vehicle speed are equal, the check valve 30 is closed by the springs 31 and 3.
Both passages 8', 21 are kept in a neutral position by the balance of 2.
' through the circumferential grooves 30a, 30b of the valve 30 to the reaction chamber 5.
However, when the hydraulic pressure generated by the road resistance load becomes higher than the hydraulic pressure generated by the vehicle speed, the hydraulic pressure acting on the left ventricle 33 via the pilot passage 34 becomes higher than the hydraulic pressure acting on the right ventricle 35. Then, the check valve 30 is moved to the right to cut off the communication between the passage 21' and the reaction chamber 5, and the hydraulic pressure of the hydraulic passage 8' is applied to the reaction chamber 5.

On the other hand, when the hydraulic pressure generated by the vehicle speed becomes higher than the hydraulic pressure generated by the road resistance load, the hydraulic pressure acting on the right ventricle 35 from the extension passage 21' via the pilot passage 36, contrary to the above, increases to the left ventricle. 33, the check valve 30 is moved to the left, and the hydraulic pressure generated by the vehicle speed is applied to the reaction chamber 5, and the hydraulic pressure generated by the road resistance load is transferred to the hydraulic pressure passage 8' and the reaction chamber 5. Cut off communication with.

That is, because of the above, the higher hydraulic pressure of either the hydraulic pressure passage 8' or the extension passage 21' acts on the reaction chamber 5, so that the hydraulic pressure in the reaction chamber 5 is too low, causing the steering wheel to wobble. The inconvenience will be resolved.

This invention has the above configuration, and the throttle valve 16.1
As is clear from the above explanation, the reason for providing two hydraulic cutoff control valves is that one hydraulic cutoff control valve is provided compared to one throttle valve.
Since the pressure drop acting on the hydraulic pressure chamber 20 of No. 4 can be increased, a high-capacity vehicle speed sensor pump is not required, and the shutoff control valve 14 can be operated reliably.

In addition, high hydraulic pressure does not directly act on each throttle valve, which eliminates the cause of poor throttle effect and protects the valves.

Another advantage is that normally, when a high-pressure liquid is passed through a throttle to a lower pressure, cavitation occurs and causes noise, but this design uses two throttle valves to create a two-stage pressure drop. This prevents cavitation and eliminates the cause of noise generation.In addition, when a car suddenly decelerates from high speed, conventional systems cause a sudden reduction in steering torque due to the responsiveness of hydraulic pressure, making it difficult to drive. However, this idea has two stages of throttle valves arranged as mentioned above, with the first stage throttle valve on the throttle side and the second stage throttle valve on the throttle side.
The throttle valves in each stage are designed to operate to the open side, so during sudden deceleration, the first stage throttle valve operates to the open side to ensure sufficient flow, and the second stage throttle valve operates to the throttle side. As a result, the flow rate through the second restriction decreases, and as a result, the change in the flow rate of both restriction portions prevents a rapid drop in the hydraulic pressure in the hydraulic chamber 20 of the hydraulic cut-off control valve 14, and therefore prevents the hydraulic pressure in the reaction chamber 5 from decreasing rapidly. There is no sudden drop in oil pressure, and sudden changes in steering torque are eliminated, allowing stable steering.

Therefore, in a power steering system to which this idea is applied, the reaction force changes according to vehicle speed and road resistance, making it ideal for both stability at high speeds and reduction of steering torque at low speeds. ■ When driving at high speeds, by providing a check valve, the recoil force is obtained from the hydraulic pressure supplied from the vehicle speed sensor pump, further improving the stability of the steering; ■ At least two throttles By installing a valve, the response is extremely good, eliminating sudden changes in steering torque due to sudden deceleration, completely eliminating the unstable factor, ■ The spring characteristics of the spring acting on the two throttle valves Various reaction characteristics can be easily specified simply by selecting and adjusting appropriately.

It is possible to provide an ideal power steering device.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main part of the embodiment, FIG. 2 is an enlarged view of a part thereof, and FIG. 3 is a diagram showing the operating characteristics. 1...Steering control valve chamber, 2...Hydraulic pump, 4...Main circuit, 5...Reaction chamber, 6
．． 8.8'...Hydraulic pressure passage, 7...Steering force control mechanism, 9...Fixed throttle, 10...
・Branch passage, 11...Mountain stream passage, 13...
... Vehicle speed sensor pump, 14 ... Hydraulic pressure cutoff control valve, 15 ... Spring, 16, 17 ...
Throttle valve, 18, 19... Spring, 20.22.2
3... Hydraulic pressure chamber, 21... Passage, 24...
... Fixed throttle, 30 ... Check valve, 31, 32 ... Spring, 34, 36 ...
・Pilot passage.

Claims (2)

[Scope of utility model registration request] (1) A power steering system in which a hydraulic reaction chamber is provided in the steering mechanism to allow the driver to sense the steering reaction force, and the steering reaction force increases as the hydraulic pressure supplied to the reaction chamber increases. In the device, a steering force control mechanism is provided in a hydraulic passage that transmits a change in hydraulic pressure in a steering control valve chamber to a hydraulic reaction chamber, and a steering force control mechanism that supplies hydraulic pressure to the reaction chamber according to vehicle speed and road resistance load; The control mechanism includes a hydraulic cut-off control valve that opens and closes the hydraulic passage according to vehicle speed and road resistance load, and a hydraulic cut-off control valve that branches from the hydraulic passage and applies road resistance load to the cut-off control valve via a fixed throttle. It includes a branch passage including a pressure chamber, at least two throttle valves provided in the branch passage, and a vehicle speed sensor pump that changes the flow rate according to an increase or decrease in vehicle speed, and one of the throttle valves is connected to the fixed throttle and the hydraulic pressure chamber. In between, the other is arranged on the return passage side behind the hydraulic pressure chamber, and as the vehicle speed increases, the throttle of the branch oil passage is changed to the closing side between the fixed throttle and the hydraulic pressure chamber, A steering force control device characterized in that the two throttle valves are controlled by the hydraulic pressure of the vehicle speed sensor pump so as to change the throttle of the branch oil passage to the open side on the return passage side behind the hydraulic pressure chamber. (2) A utility model registration request in which the steering force control mechanism includes a check valve that supplies the higher of the hydraulic pressure controlled by the cutoff control valve and the hydraulic pressure generated by the vehicle speed sensor pump to the reaction chamber. The steering force control device according to range (1).