JPH0334382Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a load-sensitive power steering device that adjusts the magnitude of steering force according to the load.

[Prior Art] A power steering device is known that reduces steering force by selectively supplying pressurized oil from an oil pump to oil cylinders linked to wheels via a flow control valve linked to input rotation from a steering wheel. Also known is a vehicle speed-sensitive power steering device that adjusts the magnitude of the steering force depending on the vehicle speed. (For example, Japanese Utility Model Application Publication No. 58-176067, Japanese Utility Model Application Publication No. 58-176068, and Japanese Utility Model Application Publication No. 59-1999, filed by the present applicant)
Publication No. 2678, etc.).

By the way, the resistance from the road surface when turning the wheels changes significantly, especially in large trucks where the vehicle weight differs greatly between loaded and empty, and the resistance when turning the wheels changes significantly. The required steering force is much larger.

Therefore, it is normal to set the vehicle so that a predetermined power assist force is obtained when the vehicle is loaded, but in this case, there is a problem that the steering wheel is too light when the vehicle is empty, making the steering unstable.

[Purpose of the invention] The present invention was made in view of the above-mentioned problems, and its purpose is to provide a load-sensitive power steering device that adjusts the magnitude of the steering force according to the load.

[Structure of the invention] According to the invention, the pressure oil of the oil pump is selectively supplied to the oil cylinder linked to the wheels via the flow control valve linked to the input rotation from the steering wheel to reduce the steering force. In the power steering device, a hydraulic control valve 2 is provided in a hydraulic circuit L1 connecting the oil pump 1 and the flow rate control valve 4, and the hydraulic control valve 2 is connected to an inlet port 21 leading to the oil pump 1 and the flow rate control valve. A spool 24 is housed in a cavity 23 of the body 20 to define an inlet chamber 25 and an outlet chamber 26. A passage 27 communicating with the exit chamber 26
A ball 30 is provided on the spool 24 and is biased by a spring 29 to open and close the passage.
A spring 33 is housed in the cavity 32 on the entrance chamber 25 side, and the sheet 34 and the spool 24 on the entrance side are urged by the spring 33. A spacer 35 and a spring 36 are provided between the spool 24 and the spacer 35, a gap C1 is formed between the spool 24 and the spacer 35, and one end of the pin 37 is connected to the spacer 35 at the bulge of the sheet. C2, and the other end of the pin 37 is connected to a load sensor 40 that detects deflection of the suspension of the vehicle.

[Description of the function and effect of the invention] Therefore, when the vehicle is empty, the pin 37 is pulled toward the side opposite to the cavity 23, and the spacer 35 is pulled away from the cavity 23 due to the difference between the tensile force of the pin 37 and the pressing force of the spring 33. Go away. Then, the spring 36 is also loosened, so the spool 24 moves toward the cavity 32 due to the pressing force of the spring 29, and the oil pressure in the inlet port 21 is throttled by the ball 30 from the passage 27, lowering the pressure, and flowing from the outlet port 22 to the flow rate control valve 4. Sent. Since the suspension flexes when the vehicle is loaded, the pin 37 is pressed toward the cavity 22, reducing the gaps C2 and C1 to zero and moving the spacer 35.
is moved toward the cavity 23, and as a result, the spool 24 is moved to the side opposite to the cavity 32. Then, the drooping pin 31 protrudes and the ball 30 enters the passage 27.
Since it is opened, the differential pressure between the inlet port 21 and the outlet port 22 becomes smaller, and more oil flows than when the vehicle is empty, and the steering force is reduced by the amount of oil flowing, allowing relatively light steering even when the vehicle is loaded. can.

As described above, according to the present invention, the combination of the gaps C1 and C2 and the springs 29, 33, and 36 absorbs vertical vibrations during running, so that the vehicle does not receive disturbance signals during running. Further, even if the pin 37 moves relatively largely during running, there is no problem because the spool will not move much due to the balance of the springs 29, 33, and 36.

Therefore, according to the present invention, the steering force does not change due to vibrations during running, and the steering force can be changed substantially linearly in response to the load amount.

[Examples] Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, the pressure oil of the pump 1 is supplied to one of the left and right pressure chambers 5a and 5b of an oil cylinder 5 linked to the wheels via a pump circuit L1 and a flow control valve 4 which is switched by the input rotation of the handle 3. For example, the oil is supplied to the pressure chamber 5a, causing the oil cylinder 5 to extend and actuate, turning the wheel, for example, to the left, and reducing the steering force of the steering wheel 3. The pump 1 is provided with a relief valve (not shown) that relieves oil when the discharge pressure exceeds a certain value. At this time, the oil in the other reaction force chamber 5b is returned to the tank 6 via the flow rate control valve 4 and the tank circuit L2. A pump circuit L1, which is a hydraulic circuit that connects the oil pump 1 and the flow rate control valve 4, is provided with a hydraulic control valve 2 that controls the hydraulic pressure according to the load amount. This hydraulic control valve 2 is provided in the brake hydraulic circuit of the wheel, and is similar to a known load sensing proportion valve so-called LSPV that controls the brake operating hydraulic pressure to be larger when the vehicle is loaded than when the vehicle is empty, depending on the loaded load. It is configured. That is, a cavity 23 provided in the body 20 of the hydraulic control valve 2 and communicating with an inlet port 21 and an outlet port 22 is divided into an inlet chamber 25 and an outlet chamber 26 by a spool 24 slidably housed in the cavity 23. The inlet chamber 25 is connected to the outlet chamber 26 via a passage 27.
is communicated with. The connection between the passage 27 and the outlet chamber 26 is formed in a small hole 28, and a ball 30, which is biased by a spring 29, is opposed to the small hole 28. A pin 31 is connected to the spool 24. This drooping pin 31 locks the ball 30 and positions the ball 30 by moving the spool 24 to change the effective flow area of the small hole 28 and constitute a variable orifice that adjusts the outlet pressure of the hydraulic control valve 2. It's becoming like that. On the other hand, a cavity 32 is formed on the side of the spool 24 facing the drooping pin 31, and a pressing force W1 is applied to one end surface of the cavity 32 and a spring 33.
A spacer 35 made of a soft material such as rubber, for example, is sandwiched between the sheet 34 and the sheet 34 which is urged. A spring 36 is stretched between the spacer 35 and the spool 24, and positions the spool 24 in balance with the spring 29, thereby forming a gap C1 between the spool 24 and the spacer 35. One end of a pin 37 is locked to the bulging portion of the seat 34 with a spacer 35 forming a gap C2, and the other end of the pin is used to detect the deflection of the suspension of the vehicle. Connected to a load sensor. The load sensor 40 includes a bell crank 41 connected to a pin 37 at one end, a wire 43 connected to an axle 42 at one end, and a leaf spring 44 connecting the other ends of the bell crank 41 and the wire 43. .

Next, the effect will be explained.

When the vehicle is empty, there is little deflection of the suspension, so the leaf spring 44 of the load sensor 40 deflects as shown by the solid line and applies a tensile force W2 to the pin 37 via the bell crank 41. Therefore, the sheet 34 presses the spacer 35 with the differential force W between the pressing force W1 of the spring 33 and the tensile force W2 of the pin 37. At this time, the spool 24 is in the position shown and the dreaming pin 3 is
1, the ball 30 is positioned at the illustrated position, and therefore the hydraulic pressure in the inlet port 21 is throttled and reduced by the variable orifice and sent from the outlet port 22 to the flow rate control valve 4.

When the vehicle is loaded, the suspension is largely deflected, and therefore the deflection of the leaf spring 44 is reduced as shown by the chain line, causing the bell crank 41 to rotate counterclockwise and apply a pressing force W3 to the pin 37. . As a result, the pin 37 moves to the left in the drawing, and the gap C2
Then, remove C1 and move the spool 24 to the left via the spacer 35. Therefore, ball 3
0 is pushed by the drooping pin 31 and moves to the left. As a result, the effective flow area of the variable orifice is increased, and the inlet port 21 and the outlet port 2
The differential pressure between the two becomes smaller. i.e. exit port 22
The pressure is adjusted to be greater than when the vehicle is empty, as shown in FIG. Note that the chain line represents the relief pressure of the pump 1 as described above. As a result, as shown in Figure 3, the output torque of the oil cylinder is adjusted so that it is larger when the vehicle is loaded than when the vehicle is empty, and therefore it is possible to steer with the same steering force when the vehicle is loaded as when the vehicle is empty. It is. Note that power assist is not performed after the chain line corresponding to the relief pressure shown in FIG. 2 of the steering wheel input torque, and steering is performed manually.

FIG. 4 shows another embodiment of the present invention, in which the present invention is implemented in a vehicle speed sensitive power steering device. In other words, the relief valve 4 is connected to the pump circuit L1.
The variable orifice 46 is controlled based on the vehicle speed signal from the vehicle speed sensor 47, and the flow rate of the pump 1 is controlled according to the vehicle speed so that it is smaller at high speeds than at low speeds. The parts are constructed in the same way as in FIG. According to this embodiment, as shown in FIG. 5, the oil cylinder output torque varies depending on the vehicle speed and loading amount, and is divided into four types: a low-speed loaded vehicle, a low-speed empty vehicle, a high-speed loaded vehicle, and a high-speed empty vehicle.
As expected, the lower the vehicle speed and the greater the load, the greater the oil cylinder output torque is controlled.
As a result, the vehicle can be steered with the same steering force regardless of vehicle speed and payload.

[Summary] As explained above, according to the present invention, the hydraulic circuit connecting the oil pump and the flow rate control valve is provided with a hydraulic control valve that controls the hydraulic pressure according to the loading amount, so that the outlet pressure of the hydraulic control valve is is controlled so that it is larger when the vehicle is loaded than when the vehicle is empty, so that the same steering force can be used for steering both when the vehicle is loaded and when the vehicle is empty.

[Brief explanation of the drawing]

Fig. 1 is a hydraulic circuit diagram showing a first embodiment of the present invention, Fig. 2 is a control characteristic diagram of its hydraulic control valve, and Fig. 3 is a hydraulic circuit diagram showing a first embodiment of the present invention.
The figure is the oil cylinder output torque characteristic diagram, 4th
The figure is a hydraulic circuit diagram showing the second embodiment of the present invention.
The figure is a diagram showing the oil cylinder output torque characteristics. L1...Hydraulic circuit connecting the oil pump and the flow rate control valve, 1...Oil pump, 2...Hydraulic pressure control valve, 3...Handle, 4...Flow rate control valve, 5...
...Oil cylinder.

Claims (1)

[Scope of utility model registration request] In a power steering device that reduces steering force by selectively supplying pressurized oil from an oil pump to an oil cylinder linked to a wheel via a flow control valve linked to input rotation from a steering wheel, the oil pump 1 and A hydraulic control valve 2 is provided in the hydraulic circuit L1 connected to the flow rate control valve 4, and the hydraulic control valve 2 has an inlet port 21 leading to the oil pump 1.
and an outlet port 22 leading to the flow control valve 4, and a cavity 2 of the body 20.
A spool 24 is housed in 3 to define an inlet chamber 25 and an outlet chamber 26, and a passage 27 that communicates the inlet chamber 25 and outlet chamber 26 is attached with a spring 29 in the direction of closing the passage 27. A ball 30 is provided which opens and closes the passage by being biased, and the ball 30 is engaged with a drooping pin 31 provided on the outlet chamber 26 side of the spool 24, and is engaged with a drooping pin 31 provided on the outlet chamber 26 side of the spool 24.
A spring 33 is housed in the cavity 2.
A spacer 35 and a spring 36 are provided between the sheet 34 that is biased toward the third side and the end face of the spool 24 on the inlet side, and a gap C1 is formed between the spool 24 and the spacer 35. One end of a pin 37 forms a gap C2 with a spacer 35 in the bulge of the seat, and the other end of the pin 37 is connected to a load sensor 40 that detects deflection of the suspension of the vehicle. Load-sensitive power steering device.