JPH0141553B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improvements in flow control valves used in vehicle power steering.

Generally, power steering is used for the purpose of reducing the steering force of a vehicle, and when the vehicle is stopped or running at low speed, it can be easily steered, pulled over, turned around, etc. with an extremely small amount of operating force, and when the vehicle is running at high speed. In some cases, vehicles have been designed to enable steering with a relatively large operating force and improve running stability.

In power steering, the flow control valve controls the amount of pressurized oil sent from the oil pump to the control valve and power cylinder side, and the return amount of pressurized oil sent back to the suction side of the oil pump. Adjust the amount to increase the boosting effect when stationary or at low speed and large steering angle,
It also prevents the operating force from becoming too light when driving at high speeds.

Therefore, when the rotational speed of the oil pump continues to rise in the high-speed rotation range, the flow rate of the pressure oil sent to the control valve and power cylinder side is reduced by the flow control valve. Although the flow rate is reduced to a predetermined level without being proportional to the pump rotation speed, the oil pump rotation speed continues to increase, so the oil pump's drive system, that is, the internal combustion engine installed in the vehicle, The burden of these efforts continued to increase. In addition, the vehicle may be parked, moved to the side,
The operating force required for turning, etc. depends on the oil and
It is determined by the output of the power steering when the pump is rotating at low speed, and the output can be increased by increasing the pressure receiving area of the power piston in the power cylinder.
Even in such cases, the burden on the internal combustion engine as the drive system for the oil pump tends to increase.

Of course, if the relief pressure in the flow control valve is configured to be low when the oil pump is rotated at high speed and high when the oil pump is rotated at low speed, the load on the internal combustion engine can be reduced. , when the oil pump rotates at low speed,
Sufficient output required for offsetting, widening, turning, etc. can be obtained, but the opening/closing conditions of the relief valve in existing flow control valves, that is, the relief pressure is set to a predetermined pressure by the relief spring. Because it is set to
As mentioned above, it has been difficult to configure the relief pressure to be changed depending on each condition.

The purpose of this invention is to reduce the burden on the oil pump drive system by increasing the relief pressure when the oil pump is rotated at low speed and lowering the relief pressure when the oil pump is rotated at high speed. Furthermore, it is extremely easy to park, pull over, turn around, etc., reducing steering fatigue, and when the oil pump rotates at high speeds, the operating force required for steering is relatively large. Our goal is to provide flow control valves used in power steering, which improve driving stability.

For those problems, the flow control system used in the power steering of this invention
A valve has a valve chamber, a pump port and a suction port that connect the valve chamber to the oil pump, a control valve port that connects the valve chamber, and a control valve port that connects the valve chamber to the oil pump.
Between the valve port and the valve. The valve casing consists of a throttle placed in the chamber, the amount of pressure oil discharged from its control valve port, and its suction.
An oil return control spool reciprocally slidably disposed within the valve chamber and downstream of the restriction so as to adjust the amount of pressure oil returned to the port. A pilot communication passage is connected to the end face of the control spool and communicates with the back pressure chamber formed in the valve chamber, and a pilot communication passage is provided so that the pressure oil in the back pressure chamber can be returned to the suction port side. a relief chamber formed within the oil return control spool and each having a back pressure chamber side port and a communication hole;
A relief valve is arranged in the relief chamber to open and close the back pressure chamber side port, and an oil return valve is arranged in line with the relief chamber through a partition wall.
A cylinder chamber formed in the control spool, a push rod penetrating the partition wall thereof and slidably disposed in the relief chamber and the cylinder chamber; A valve spring disposed within the relief chamber so as to press the relief valve against the valve seat of the back pressure chamber side port, and divide the cylinder chamber into an upstream pressure chamber and a downstream pressure chamber. The oil return control spool is connected to a piston reciprocatably disposed in the cylinder chamber and provided in the push rod, and to connect the pump port side to the upstream pressure chamber. an upstream pressure port formed in the oil return control spool and a downstream pressure port formed in the oil return control spool to connect the back pressure chamber to the downstream pressure chamber.

Hereinafter, preferred specific examples of the flow control valve used in power steering according to the present invention will be described with reference to the drawings.

The figure shows a specific example 10 of a flow control valve used in the power steering of the present invention applied to a cab-over type truck.

The flow control valve 10 includes a valve chamber 22, a valve chamber 22,
a pump port 23 and a suction port 24 for connecting the pump to an oil pump (not shown);
A valve comprising a control valve port 25 connected to the valve chamber 22 and a restriction 26 disposed in the valve chamber 22 between the pump port 23 and the control valve port 25. a reciprocating slide within the casing 11 and its valve chamber 22 to adjust the amount of pressure oil discharged from the casing 11 and its control valve port 25 and the amount of pressure oil returned to its suction port 24; A movably arranged oil return control spool 12 and a downstream side of its throttle 26 are connected to the oil return control spool 12 and its downstream side.
A pilot communication passage 13 cooperates with the end face of the spool 12 and communicates with a back pressure chamber 27 formed in the valve chamber 22, and returns pressure oil in the back pressure chamber 27 to the suction port 24 side. A relief chamber 14 is formed in the oil return control spool 12 and has a back pressure chamber side port 28 and a communication hole 29, respectively, and a relief chamber 14 is formed in the oil return control spool 12 so as to open and close the back pressure chamber side port 28. a relief valve 15 disposed within the relief chamber 14; and a relief valve 15 formed within the oil return control spool 12 so as to be disposed side by side in the relief chamber 14 with a partition wall 30 in between. a cylinder chamber 16, which is provided with a cylinder chamber 16;
The push rod 17 pushes the relief valve 28 against the valve seat of the back pressure chamber side port 28.
4 and the cylinder chamber 16 is connected to an upstream pressure chamber 31 and a downstream pressure chamber 32.
A piston 19 is disposed so as to be able to reciprocate and slide in the cylinder chamber 16 and is integrally provided with the push rod 17 so as to divide the pump port 23 into an upstream pressure chamber 31. an upstream pressure side port 20 formed in the oil return control spool 12 to connect to the oil return control spool 12 and an upstream pressure side port 20 formed in the oil return control spool 12 to connect the back pressure chamber 27 to the downstream pressure chamber 32; 12, and a downstream pressure side port 21 formed at 12.

The valve casing 11 may be provided independently between an oil pump (not shown) and a control valve (not shown) that constitute the power steering, or may be installed between the oil pump and the control valve. It is formed integrally with the casing of the valve and has a cylindrical valve chamber 22 inside.

Pump port 23 and suction port 24 are orthogonally connected to valve chamber 22 of valve casing 1 .
1 at predetermined intervals.

Its pump port 23 and suction port 24 are connected to the discharge and suction sides of the oil pump, respectively, via hydraulic piping (not shown).

A control valve port 25 is formed in the valve casing 11 so as to be disposed approximately coaxially with the valve chamber 22 at a position proximal to the pump port 23; A restriction 26 is formed between the valve port 23 and its pump port 23 .

The control valve port 25 is connected to a control valve supply port (not shown) via hydraulic piping (not shown).

Oil return control spool 1
2 has a reciprocating slide in its valve chamber 22 so as to adjust the amount of pressure oil discharged from its control valve port 25 and the amount of pressure oil returned to its suction port 24. It is arranged so that it can be moved.

If the oil return control spool 12 is so positioned within the valve chamber 22, the valve chamber 22
A back pressure chamber 27 is formed in cooperation with the end face of the oil return control spool 12.

Of course, a valve spring 33 is arranged in the back pressure chamber 27 and presses the oil return control spool 12 against the throttle 26 side.

The pilot communication passage 13 is connected to its control
The downstream side of the restriction 26 in the valve port 25 is formed in the valve casing 11 so as to communicate with the back pressure chamber 27.

Additionally, the valve chamber 22 may be
A relief chamber 14 is formed inside the oil return control spool 12 disposed therein at a position on the back pressure chamber 27 side.

The relief chamber 14 includes the back pressure chamber 2
A back pressure chamber side port 28 opened to the 7 side, and
Each of them is provided with a communication hole 29 opened on the suction port 24 side, so that the pressure oil in the back pressure chamber 27 can be returned to the suction port 24 side.

The relief valve 15 is a ball type,
It is arranged within the relief chamber 14 to open and close the back pressure chamber side port 28.

Furthermore, inside the oil return control spool 12, a cylinder chamber 16 is provided.
Through the partition wall 30, the relief chamber 1
It is formed so as to be lined up with 4.

The push rod 17 passes through the partition wall 30 and is arranged to be able to slide back and forth into the relief chamber 14 and the cylinder chamber 16.

A valve spring 18 is disposed within the relief chamber 14, and the push rod 17 causes the relief valve 1 to
5 is pressed against the valve seat of the back pressure chamber side port 28.

The piston 19 is disposed so as to be able to slide back and forth within the cylinder chamber 16 so as to divide the cylinder chamber 16 into an upstream pressure chamber 31 and a downstream pressure chamber 32, and is integrally formed with the push rod 17. ing.

Of course, the tip of the push rod 17 is the oil return control spool 1.
The push rod 17 is inserted through the front partition wall 35 in the cylinder chamber 16 so that the piston 19 is positioned approximately in the center of the cylinder chamber 16.
is integrally formed. Therefore, the piston 19 has the upstream pressure chamber 31 and the downstream pressure chamber 32.
The push rods 17 are provided so that the pressure receiving areas at the push rods 17 are approximately equal.

Also, its oil return control
A drain chamber 34 is formed inside the spool 12 at a position forward of its cylinder chamber 16, and the drain chamber 34 is connected to the relief chamber 14 described above via a drain passage 36. .

The upstream pressure side port 20 is formed in the oil return control spool 12 so as to guide the pressure oil on the pump port 23 side of the valve casing 11 to the upstream pressure chamber 31 thereof.

Further, the downstream pressure side port 21 is formed in the oil return control spool 12 so as to guide the pressure oil in the back pressure chamber 27 to the downstream pressure chamber 32.

That is, the pressure on the pump port 23 side, in other words, the pressure on the upstream side of the throttle 26 acts in the upstream pressure chamber 31, and the back pressure acts in the downstream pressure chamber 32. The pressure within the chamber 27, in other words, the pressure on the downstream side of the throttle 26 acts, and the piston 19 is reciprocated due to the difference in these pressures.

Therefore, the pressure at which the relief valve 15 is opened, the so-called relief pressure, is changed depending on the pressure difference between the upstream pressure chamber 31 and the downstream pressure chamber 32.

Next, the above-mentioned flow control valve 1
To explain the operation of No. 0, when the oil pump is rotating at low speed, the oil return control spool 12 is pushed toward the throttle 26 by the valve spring 33, and the suction port 24 is closed. , closed by its oil return control spool.

When the oil pump is rotating at such a low speed, the pressure drop at the throttle 26 is small, so the difference in pressure between the upstream pressure chamber 31 and the downstream pressure chamber 32 is small, and the relief pressure in such a case is is determined essentially only by the spring constant of the valve spring 18 that presses the relief valve 15 against the valve seat of the back pressure chamber side port 28.

That is, if a valve spring 18 with a predetermined spring constant is used, the relief pressure will be increased in accordance with the spring constant when the oil pump rotates at a low speed.

Therefore, when the relief pressure is increased in this way, a sufficient amount of pressure oil can be discharged at the control valve port 25, which improves the output of power steering, making it extremely easy to steer, close to the width, turn around, etc. easily done.

Furthermore, as the oil pump speed increases, the oil return control spool 12 is increasingly slid against the valve spring 33, and the pressure drop across the restriction 26 increases as the oil pump speed increases. The pressure in the upstream pressure chamber 31 gradually becomes larger than the pressure in the downstream pressure chamber 32 because it increases almost in proportion to the rotation speed.

That is, the pressure in the upstream pressure chamber 31 slides the piston 19, pulls the push rod 17 against the valve spring 18, and releases the relief.
Since it acts to open the valve 15, when the pressure difference between the upstream pressure chamber 31 and the downstream pressure chamber 32 increases, in other words, when the rotation speed of the oil pump increases, the relief pressure gradually decreases. Become.

Therefore, when the oil pump is rotated at high speed,
Since the relief pressure is lower, the burden on the internal combustion engine as the drive system for the oil pump is reduced.

Of course, when the oil pump is rotated at such a high speed, the oil return control spool 12 slides to the suction port 2.
4 is opened and the pump port 23 is connected to its suction port 24, so that the excess flow of pressure oil is returned to the suction side of the oil pump;
This prevents the steering force from becoming too light, improving driving stability.

According to this invention configured as above, the valve
The relief pressure is changed according to the pressure drop in the casing throttle, and when the oil pump is rotated at low speed, the relief pressure is high, and when the oil pump is rotated at high speed, the relief pressure is low. The load on the oil pump's drive system is reduced, and it becomes extremely easy to park, close, turn, etc., reducing steering fatigue.Furthermore, when the oil pump rotates at high speed, Relatively large force is required, driving stability is improved, and it becomes extremely practical.

[Brief explanation of drawings]

The figure is a schematic diagram showing a specific example of a flow control valve used in the power steering system of the present invention applied to a cab-over type truck. 10...Flow control valve used in power steering, 11...Valve
Casing, 12...Oil return control spool, 13...Pilot communication passage,
14... Relief chamber, 15... Relief valve, 16... Cylinder chamber, 17... Bush rot, 18... Valve spring, 1
9...Piston, 20...Upstream pressure side port, 21
... Downstream pressure side port, 22 ... Valve chamber, 23 ... Pump port, 24 ... Suction port, 25 ... Control valve port, 26 ... Throttle, 27 ... Back pressure chamber, 28 ... …
Back pressure chamber side port, 29...Communication hole, 30...Partition wall, 31...Upstream pressure chamber, 32...Downstream pressure chamber.

Claims (1)

[Claims] 1. A valve chamber, a pump port and a suction port connecting the valve chamber to an oil pump, a control valve port connected to the valve chamber, and a pump port. a valve casing consisting of a restriction located in the valve chamber between the control valve port and the control valve port; An oil return control spool is reciprocatably disposed within the valve chamber to adjust the return amount of pressurized oil;
A pilot communication passage cooperates with the end face of the control spool and communicates with the back pressure chamber formed in the valve chamber, and a pilot communication passage is provided so that the pressure oil in the back pressure chamber can be returned to the suction port side. A relief chamber formed within the oil return control spool and each having a back pressure chamber side port and a communication hole; a cylinder chamber formed in the oil return control spool so as to be disposed side by side with the relief chamber through the partition wall; A push rod is arranged to be able to reciprocate in the relief chamber and the cylinder chamber, and the push rod pushes the relief valve against the valve seat of the back pressure chamber side port. A valve spring disposed in the chamber, and a valve spring disposed in the cylinder chamber so as to be able to reciprocate and slide in the cylinder chamber so as to divide the cylinder chamber into an upstream pressure chamber and a downstream pressure chamber, and provided in the push rod. an upstream pressure side port formed in the oil return control spool to connect the pump port side to the upstream pressure chamber, and an upstream pressure side port formed in the oil return control spool to connect the back pressure chamber to the downstream pressure chamber. To,
A flow control valve used in power steering including a downstream pressure side port formed on its oil return control spool.