JPH0421022Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a pressure control device for a variable displacement hydraulic motor or a variable displacement hydraulic pump, in particular, for keeping the drive oil pressure of the motor or the discharge pressure of the pump constant. This invention relates to a pressure control device.

[Prior art] A variable displacement hydraulic motor has a swash plate as a means for changing the capacity of the hydraulic motor, and if the amount of driving pressure oil is the same, if the angle of the swash plate, that is, the tilt angle increases, one revolution will occur. The amount of pressurized oil required to drive increases, the rotational speed decreases, and the output torque increases. Also, if the tilt angle decreases, the amount of pressurized oil required to drive one rotation will decrease.
The rotational speed increases and the output torque decreases. Therefore,
When a variable displacement hydraulic motor is used to perform work, the swash plate must be tilted in response to external force in order to prevent an excessive load from being applied to the hydraulic motor or to handle a large load without increasing the drive oil pressure. Pressure control is performed to adjust the angle and keep the motor drive oil pressure constant.

A conventional constant pressure control device for a variable displacement hydraulic motor is shown in FIG.

The tilt angle θ of a swash plate 30 of a variable displacement hydraulic motor (hereinafter referred to as a hydraulic motor) 1 is adjusted by a differential cylinder 2, and pressure oil is supplied to the differential cylinder 2 via a pilot valve 3. It is made so that it will be exposed.

The structure of the pilot valve 3 will be briefly described below.

The cylinder block 4 has a large diameter hole 5, a medium diameter hole 6, and a small diameter hole 7 that are continuous with each other and have the same axis, and a spool 8 is slidably fitted into the medium diameter hole 6 and the small diameter hole 7. match.

The spool 8 has a narrow end portion 9 that fits into the small diameter hole 7, and large diameter portions 10, 1 that fit into the medium diameter hole 6.
1 and 12 are formed, and the small diameter end portion 9 and the small diameter hole 7 partition off the oil reservoir chamber 13, and the large diameter portions 10, 11, and 12 partition the medium diameter hole 6 into oil chambers 14, 15, 1
6 is formed. The spool 8 is provided with an oil passage 17 that opens into the oil reservoir chamber 13 at one end and communicates with the oil chamber 16 at the other end, and a throttle 18 is provided at a predetermined position of the oil passage 17. The large-diameter hole 5 is formed in a liquid-tight oil chamber 19, into which the large-diameter portion 12 of the spool 8 enters and exits, and urges the spool 8 toward the oil reservoir chamber 13. A spring 20 is provided.

The cylinder block 4 is also provided with a pressure sensitive port 21 communicating with the oil chamber 14 and a pressure oil introduction port 22 communicating with the oil chamber 15 at the neutral position of the spool 8 (the oil pressure in the oil chamber 14 and the biasing force of the spring 20). An orifice port 23 which is closed by the large diameter portion 11 at a balanced position), a discharge port 24 communicating with the oil chamber 16, and an input/output port 25 communicating with the oil chamber 19 are provided, respectively. The pressure sensitive port 21 and the pressure oil introduction port 22 are connected to the oil supply line 2 of the hydraulic motor 1.
6, the pressure oil introduction port 22 communicates with the rod side cylinder chamber 27 of the differential cylinder 2, the orifice port 23 communicates with the piston side cylinder chamber 28, and the discharge port 24 and the input/output port 25 communicate with the oil tank 29. Connect to.

In such a conventional variable displacement hydraulic motor,
Oil supply line 26 set by spring 20
If the actual hydraulic pressure is smaller than Po, the force received from the pressure oil in the oil chamber 14 will be smaller than the biasing force of the spring 20, and the spool 8 will
moves to the right. By moving the spool 8 to the right, the orifice port 23 and the discharge port 24 communicate with each other via the oil chamber 16. Due to the communication between the orifice port 23 and the discharge port 24, the piston-side cylinder chamber 28 communicates with the oil tank 29, the pressure decreases, the piston moves to the left in the figure, and the swash plate 30
Decrease the tilt angle of Therefore, the rotational speed of the hydraulic motor 1 increases, and the load pressure of the hydraulic motor 1 increases. When the oil pressure in the oil supply line 26 reaches Po due to an increase in load pressure, the spool 8 becomes the neutral position.
The large diameter portion 11 closes the orifice port 23,
The movement of the differential cylinder 2 is stopped. Therefore, the supply oil pressure (driving oil pressure) returns to Po.

Further, when the actual oil pressure in the oil supply line 26 is greater than Po, the spool 8 is moved to the left by the oil pressure in the oil chamber 14. By moving the spool 8 to the left, the pressure oil introduction port 22 and orifice port 2
3 communicates with each other via the oil chamber 15, and the cylinder chamber 27
and 28 are communicated. Due to the difference in the pressure receiving area of the piston, the piston moves to the right, increasing the tilting angle θ and decreasing the rotation speed of the hydraulic motor 1. As the rotational speed decreases, the load pressure is reduced and the supply oil pressure decreases. When the supply oil pressure decreases to Po, the large diameter portion 11 closes the orifice port 23 and the movement of the differential cylinder 2 stops, as described above.

Therefore, the supply oil pressure is controlled at a constant pressure of Po.

[Problems to be Solved by the Invention] In the pilot valve described above, oil flows into and out of the oil reservoir chamber 13 via the oil passage 17 in accordance with the movement of the spool 8. When the oil passes through the oil passage 17, which is a path for oil to flow into and out of the oil reservoir chamber 13, resistance is applied to the oil by the throttle 18, and the movement of the spool 8 is braked. This braking of the spool 8 prevents the hunting phenomenon of the spool 8 and allows the differential cylinder 2 to operate smoothly.

However, although the throttle 18 has the effect of preventing the spool 8 from hunting, it also suppresses the responsiveness of the spool 8. In other words, the differential cylinder 2 increases the delay in the operation of increasing or decreasing the tilting angle in accordance with the motor load.
In particular, if the motor load suddenly increases and the response of the tilt angle is delayed, the load pressure of the motor becomes undesirably greater than necessary. For example, when driving a winch with a hydraulic motor, when a suspended load is held by the brake, the brake is released, and the suspended load load is transferred to the motor (winch startup), the motor load pressure may increase extremely. This is a problem as the suspended load may fall suddenly.

[Means for solving the problems] The present invention was made in view of the above-mentioned circumstances, and includes a small diameter hole 7, a medium diameter hole 6, and a large diameter hole 5 from one end A side.
The cylinder block 4 has a small-diameter tip portion 9 that fits into the small-diameter hole 7 and large-diameter portions 10, 11, and 12 that fit into the medium-diameter hole 6. a spool 8 slidably inserted therein, an oil reservoir chamber 13 formed by the tip small diameter portion 9 and the small diameter hole 7, and the large diameter portions 10, 1.
oil chambers 14, 15, 16 formed by partitioning the medium diameter hole 6 by the medium diameter holes 1, 12; an oil chamber 19 formed by the large diameter portion 12 and the large diameter hole 5; an oil passage 17 whose one end communicates with the oil reservoir chamber 13 and whose other end communicates with the oil chamber 16; and the oil chamber 19.
a spring 20 provided therein which biases the spool 8 from the other end B side toward one end A side; a pressure sensitive port 21 bored in the cylinder block 4 so as to communicate with the oil chamber 14; A pressure oil introduction port 22 is formed in the cylinder block 4 so as to communicate with the oil chamber 15, a discharge port 24 is formed in the cylinder block 4 so as to communicate with the oil chamber 16, and a large An orifice port 23 is closed by the diameter portion 11 and is bored in the cylinder block 4 so that it can communicate with the discharge port 24 via the oil chamber 16 when the spool 8 moves to the B side, and an oil chamber in the cylinder block 4. 19, and a fixed orifice 31 provided in the discharge port 24. The piston rods of the dynamic cylinder 2 are connected, and the pressure sensitive port 21 and the pressure oil introduction port 22 are connected to the rod side cylinder chamber 27 of the differential cylinder 2 and the oil supply line 26 of the variable displacement hydraulic motor or hydraulic pump 1. , the orifice port 23 is connected to the piston side cylinder chamber 28 of the differential cylinder 2, and the discharge port 24 and the input/output port 25 are connected to the oil tank 2.
It is characterized by being connected to 9.

[Function] By moving the spool 8 to the B side, the pressure introduction port 22 and the orifice port 23 communicate with each other via the oil chamber 15, and pressure oil flows into both cylinder chambers 27, 2.
8, the piston of the differential cylinder 2 moves from the side with a larger pressure-receiving area to the side with a smaller pressure-receiving area, changing the tilt angle of the swash plate 30.

Further, by moving the spool 8 toward the A side, the orifice port 23 and the discharge port 24 communicate with each other via the oil chamber 16, and the cylinder chamber 28 communicates with the oil tank 29.

The pressure oil in the other cylinder chamber 28 is pushed by the piston and discharged to the oil tank 29 via the fixed orifice 31 of the discharge port 24, but the discharge speed is suppressed by the fixed orifice 31, so the differential The piston movement speed of the cylinder 2, that is, the tilt angle change speed of the swash plate 30 is controlled.

[Example] An example of the present invention will be described below based on the drawings.

Components in FIG. 1 that are the same as those shown in FIG. 2 are given the same reference numerals.

The present invention has substantially the same configuration as the pilot valve 3 described above, but the oil passage 17 does not have a restriction 18 and the discharge port 24 is provided with a fixed orifice 31.

Even in such a pilot valve 32, the position of the spool 8 is still determined by the balance between the biasing force of the spring 20 and the oil pressure in the oil chamber 14, and when the supplied oil pressure is equal to the set pressure Po, the spool 8 is neutral. position, and when the supply oil pressure is smaller than the set pressure Po, the cylinder chamber 28 and the oil tank 29 are in communication, and when the supply oil pressure is greater than the set pressure Po, the cylinder chamber 27 is in communication.
and 28 communicate with each other.

When the supply oil pressure is lower than the set pressure Po, the spool 8 moves to the right in the figure, but the oil in the oil reservoir chamber 13 is discharged to the tank 29 via the oil passage 17 and the fixed orifice 31. At this time, the fixed orifice 31 creates oil discharge resistance, which suppresses the moving speed of the spool 8 and prevents hunting. The movement of the spool 8 brings the cylinder chamber 28 and oil tank 29 into communication, and the oil in the cylinder chamber 28 is discharged to the oil tank 29. During this discharge process, the oil still passes through the fixed orifice 31, so the oil discharge speed is suppressed and the operating speed of the differential cylinder 2 is controlled.

Next, when the supply oil pressure is higher than the set pressure Po, the spool 8 moves to the left in the figure, and the oil in the tank 29 passes through the fixed orifice 31 and the oil passage 17 to the oil reservoir chamber 13.
being sucked inward. During this suction process, the oil also passes through the fixed orifice 31, so the suction speed is suppressed and hunting of the spool 8 is also prevented.

When both cylinder chambers 27 and 28 communicate with each other, the piston moves to the right, and oil in the cylinder chamber 27 and oil in the oil supply line 26 flow into the cylinder chamber 28 via the pressure oil introduction port 22 and the orifice port 23. In this process, since there is no orifice in the flow path, the oil flows without resistance, the differential cylinder 2 operates quickly, and the tilting angle θ of the swash plate 30 increases rapidly.

This is preferable because the output torque of the hydraulic motor quickly follows the increase in load.

Note that various shapes of the spool of the pilot valve etc. can be considered and are not limited to the shapes of the above embodiments.

Furthermore, although the above embodiments have been described with respect to a hydraulic motor, it goes without saying that the present invention can also be implemented with a hydraulic pump.

[Effects of the invention] As described above, according to the invention, the output torque of the hydraulic motor is gradually decreased in response to a decrease in load, and the output torque is rapidly increased in response to an increase in load. In either case, the output of the hydraulic motor is controlled safely, and the degree of reduction in output torque is kept constant to perform stable capacity control of the variable motor.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention;
The figure is an explanatory diagram showing a conventional example. 1 is a hydraulic motor or hydraulic pump, 2 is a differential cylinder, 4 is a cylinder block, 5 is a large diameter hole,
6 is a medium diameter hole, 7 is a small diameter hole, 8 is a spool, 9 is a small diameter part at the tip, 10, 11, 12 is a large diameter part, 13 is an oil reservoir chamber, 14, 15, 16, 19 is an oil chamber, 17 is an oil path, 20 is a spring, 21 is a pressure sensitive port, 22
is the pressure oil introduction port, 23 is the orifice port, 2
4 is a discharge port, 25 is an input/output port, 26 is an oil supply line, 27 is a cylinder chamber on the rod side, 28 is a cylinder chamber on the piston side, 29 is an oil tank, 30 is a swash plate, 31 is a fixed orifice, and 32 is a pilot valve. .

Claims (1)

[Scope of utility model registration request] A cylinder block 4 has a small-diameter hole 7, a medium-diameter hole 6, and a large-diameter hole 5 drilled on the same axis from one end A side, and the small-diameter portion 9 at the tip that fits into the small-diameter hole 7 fits into the medium-diameter hole 6. a spool 8 having large diameter portions 10, 11, 12 and slidably inserted into the cylinder block 4; an oil reservoir chamber 13 formed by the tip narrow diameter portion 9 and the small diameter hole 7; Said large diameter portion 10,1
oil chambers 14, 15, 16 formed by partitioning the medium diameter hole 6 by the medium diameter holes 1, 12; an oil chamber 19 formed by the large diameter portion 12 and the large diameter hole 5; an oil passage 17 whose one end communicates with the oil reservoir chamber 13 and whose other end communicates with the oil chamber 16; and the oil chamber 19.
a spring 20 provided therein which biases the spool 8 from the other end B side toward one end A side; a pressure sensitive port 21 bored in the cylinder block 4 so as to communicate with the oil chamber 14; A pressure oil introduction port 22 is formed in the cylinder block 4 so as to communicate with the oil chamber 15, a discharge port 24 is formed in the cylinder block 4 so as to communicate with the oil chamber 16, and a large An orifice port 23 is closed by the diameter portion 11 and is bored in the cylinder block 4 so that it can communicate with the discharge port 24 via the oil chamber 16 when the spool 8 moves to the B side, and an oil chamber in the cylinder block 4. 19, and a fixed orifice 31 provided in the discharge port 24. The piston rods of the dynamic cylinder 2 are connected, and the pressure sensitive port 21 and the pressure oil introduction port 22 are connected to the rod side cylinder chamber 27 of the differential cylinder 2 and the oil supply line 26 of the variable displacement hydraulic motor or hydraulic pump 1. , the orifice port 23 is connected to the piston side cylinder chamber 28 of the differential cylinder 2, and the discharge port 24 and the input/output port 25 are connected to the oil tank 2.
9. A pressure control device for a variable displacement hydraulic motor and a hydraulic pump.