JP3090976B2 - Hydraulic drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a variable displacement motor.
The present invention relates to a hydraulic drive circuit provided with volume control means for controlling a product .

[0002]

2. Description of the Related Art Generally, a hydraulic drive equipped with a variable displacement motor is used.
In the dynamic circuit, means for changing the drive speed in response to a change in load are taken to improve workability.

Conventionally, as shown in FIG. 4, for example, there is known a displacement control apparatus for a variable displacement motor in which a displacement control cylinder 102 of the variable displacement motor 100 is controlled by a constant horsepower control valve 104 (Japanese Patent Publication No. Hei 3 (1994)). -8401). In this displacement control device, the constant horsepower control valve 104
Makes the drive pressure from the spring 106 and the motor 100 and the pilot pressure from the remote control valve 108 oppose each other via the spool 110, and sets the displacement per motor to a pilot pressure with respect to the spring 106 and the motor drive pressure. It is configured to control the volume control cylinder 102 so that the pressure decreases when the pressure is overcome, increases when the pressure is lost, and keeps constant when the pressure is balanced. Therefore, according to such a configuration, since the set pressure of the constant horsepower control valve 104 is changed by the pilot pressure from the remote control valve 108, a constant horsepower characteristic can be obtained even when the pilot pressure is constant, and a constant load can be obtained. Even in this state, an arbitrary motor rotation speed can be obtained by operating the lever.

[0004]

However, in the above-mentioned conventional technology, there are the following problems to be improved.

[0005] That is, in the prior art, the constant horsepower control valve 104 has three positions, and these three positions are:
As described above, the position is determined by opposing the sum of the spring 106 and the motor drive pressure to the pilot pressure for operating the switching valve 112 (see FIG. 4) at both ends of the constant horsepower control valve 104, respectively. Therefore, for example, when the switching valve 112 is half-operated at the intermediate position and held at this position,
The following difficulties arise. That is, in this case, the pilot pressure acting on the constant horsepower control valve 104 is equal to the switching valve 1
Since the constant pressure is the same as when operating the motor 12, the motor drive pressure for balancing the constant horsepower control valve 104 against this pilot pressure is also a pressure at only one point. However , when a load is driven by a hydraulic motor, the driving pressure of the load varies largely due to inertia of the load, acceleration, deceleration, or an external force acting on the load, even if the load is the same. Therefore,
Under such conditions, it is extremely difficult or practically impossible to maintain the constant horsepower control valve 104 in a balanced position, and therefore control of the motor volume, that is, maintaining the driving speed at a constant speed may be extremely unstable. There is.

Further, in the above-mentioned technique, even when it is desired to drive a light load by a half-operation, the motor capacity is always set to a minimum capacity when the horsepower is equal to or less than a specified horsepower. There is also a risk of being driven by. Further, even when a relatively heavy load is to be driven at a medium speed, the motor capacity is set and held at the maximum capacity once the specified horsepower is exceeded, so that the load cannot be driven at an intermediate capacity of the motor, that is, at a medium speed. And so on.

[0007] Therefore, an object of the present invention is to reduce the motor load.
When relatively small, use a variable displacement motor as a pilot valve.
The motor can be driven steplessly at a speed corresponding to the operation amount of
When the load is relatively large, change the drive speed of the variable displacement motor.
Oil that can be automatically adjusted according to the size of the load
Another object of the present invention is to provide a pressure driving circuit .

[0008]

SUMMARY OF THE INVENTION A hydraulic drive circuit according to the present invention is provided.
The path is provided for a hydraulic pump, a variable displacement motor driven by pressure oil from the hydraulic pump, and the variable displacement motor .
A switching valve for switching the flow direction of the sheet is the pressure oil, the switching
In a hydraulic drive circuit including a pilot valve for piloting a change valve, the volume of the variable displacement motor is controlled.
The means for controlling is a volume control cylinder and this volume control series.
A server for controlling the volume of the variable displacement motor through a
Boss spool and one end of this servo spool with the switching valve
Servo piston for applying motor drive pressure from
The other end of the servo spool facing the servo piston
And a cylinder disposed on the side
-A piston rod protruding toward the boss pool
Pressure for urging the piston rod of the
A compression spring and the pilot pressure introduced into the cylinder.
Step having a step for defining a step cylinder oil chamber
Piston with the stepped piston in cooperation with the stepped piston.
A retainer that regulates the amount of movement of the compression rod, and the compression spring
With a biasing force greater than the biasing force of
Attach the retainer in the direction opposite to the biasing direction of the piston rod.
And a biasing member for biasing .

In this case, the hydraulic pump can be configured to perform constant horsepower control.

[0010]

According to the hydraulic drive circuit of the present invention, the servo
The motor drive pressure acting on the stone is based on the urging force of the compression spring.
When small, the position of the servo spool is
The model that is determined only by the size and acts on the servo piston
When the motor drive pressure is greater than the biasing force of the compression spring,
The position of the boss spool is determined only by the magnitude of the motor drive pressure.
Round . Therefore, it is variable when the motor load is relatively small.
Speed of displacement motor corresponding to pilot valve operation amount
And can be driven steplessly when the motor load is relatively large.
Automatically changes the drive speed of the variable displacement motor in accordance with the size of the load.
Can be adjusted dynamically .

[0011]

Next, an embodiment of a hydraulic drive circuit according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, first, the hydraulic pressure of the present invention is shown.
The basic configuration of the drive circuit will be briefly described. In this embodiment, the hydraulic circuit includes a hydraulic pump 16 and the hydraulic pump 16.
Variable displacement motor 10 driven by pressure oil from
And the flow of the pressure oil supplied to the variable displacement motor 10.
A variable displacement motor 10 having a switching valve 20 for switching the direction and a pilot valve 24 for operating the switching valve 20 via a secondary pilot pressure from a pilot pump 22.
Is the volume, ie the displacement volume per revolution
It is configured to be controlled by the control device 12 .

[0013] The volume control device 12, the volume control valve 28
And a volume control cylinder 26. The volume control cylinder 26 includes a head chamber 26a, a rod chamber 26b, and a rod 26c disposed therebetween. When the rod 26c moves left in FIG. 1, the motor capacity decreases, and when the rod 26c moves right, the motor capacity increases. It is configured as follows. Further, the volume control valve 28 is connected to the volume control cylinder 2.
6 to control the volume of the variable displacement motor 10
A servo spool 32 slidable in the leave 32a;
From the switching valve 20 to the left end 30a of the servo spool 32
Motor drive pressure via shuttle valve 56 and line 58
Servo piston 30 to act and this servo piston
30 and is disposed on the other end side of the servo spool 32.
Cylinder 35 and the servo
A piston rod 37 projecting toward the
For urging the piston rod 37 of the motor toward the servo spool.
Pilot pressure is introduced into the compression spring 36 and the cylinder 35.
Has a step for defining a step cylinder chamber 44 to be formed
Stepped piston 40 and in cooperation with this stepped piston 40
Retainer 38 for restricting displacement of piston rod 37
And fix the retainer 38 and the stepped piston 40
Urging member for urging in the direction opposite to the urging direction of the connecting rod 37
And the force of the spring 34 is set to be greater than the force of the spring 36. And the cylinder
Pilot pressure from the pilot valve 24 is supplied to the stepped cylinder oil chamber 44 formed by the stepped piston 35 and the stepped piston 40 via the line 46, the shuttle valve 48, and the line 50, and the left end 30 a of the servo piston 30 and the rod chamber 26b of the volume control cylinder 26, the pressure oil (motor drive pressure) line 52 from the hydraulic pump 16, switching valve 20, line 54, the shuttle valve 56 is supplied via line 68, further wherein the line The motor drive pressure in 58 causes the operation of the servo spool 32 to control the tank 18 via the line 60 or the head chamber 26 a or the line 62.
It is configured to be exhausted . The state of the volume control device 12 shown is that the servo spool 32 is at the right end position, whereby the motor driving pressure in the line 58 is connected to the rod chamber 26b, and the head chamber 26a is After passing through the spool 32 and the line 62
To the tank 18 and thus the rod 26c
Shows the state at the right-hand end position via the motor driving pressure in the rod chamber 26b, that is, the state in which the capacity of the variable displacement motor 10 is maintained at the maximum value. Note that the above
Sleeve 32a slidably holding pool 32
Is integrally connected to the upper end of the rod 26c.
The spool 26 and the slot by the left and right movement of the rod 26c.
The relative position of the probe 32a changes.

In such a configuration, the pilot valve
The operating lever 24a of the probe 24 within the <br/> when in the neutral position shown, the stepped portion cylinder oil chamber 44 because the pilot pressure is not applied (line 46 is connected to the tank
) , The stepped piston 40 and the retainer 38 are positioned as shown.
It is in the place. At this time, the volume control cylinder 26 is locked.
The gate 26c is controlled by the motor driving pressure in the line 58 as described above.
At the right end of the line, thereby
The volume is kept at the maximum value .

From this state, the pilot valve 24 is operated.
And <br/> for tilting the lever 24a for example shown in the arrow direction, a pilot pressure corresponding to the operating amount of the operating lever 24a
It is supplied via line 46 to the switching valve 20, whereby it is switched off.
The spool 20a of the switching valve 20 moves to the left in the figure . Soshi
As a result, the spool 20a of the switching valve 20 moves to the left in the drawing.
And the hydraulic oil (motor drive pressure) from the hydraulic pump 16
Motor 52, a switching valve 20, and a variable displacement motor via a line 54.
10, and the line 52, the switching valve 20,
Via line 54, shuttle valve 56 and line 58
Acts on the left end of the piston 30 in the figure . Also Pyro
Operating lever 24a of the cut valve 24 in the direction of the arrow shown in the figure.
When the tilt operation is performed, the power corresponding to the operation amount of the operation lever 24a is adjusted.
The pilot pressure is changed through the shuttle valve 48 and line 50
The oil is supplied to the Linda oil chamber 44, whereby the spring 34 contracts.
And the stepped piston 40 moves into the stepped cylinder oil chamber 44.
It moves to the left in the figure according to the supplied pilot pressure.
When the stepped piston 40 moves to the left in the figure, the stepped
The attached piston 40 is separated from the retainer 38, and this separation
As a result, the spring 36 is released from the restraint of the spring 34, and the spring 3
6 causes the retainer 38 to move the stepped piston 40
While moving to the left in the figure by the movement amount,
The spring force is applied to the servo spool 32 via the piston rod 37.
Acts on the right end of the figure . At this time, the servo piston 30
Is smaller than the spring force of the spring 36.
If the motor load is relatively small,
The resilience of the spring 36 overcomes the motor drive pressure,
The piston rod 37 and the servo spool 32 are
It moves leftward in the figure by the amount of movement of the screw 38. And pis
Ton rod 37 and servo spool 32 to the left in the figure
When moved, the servo spool 32 and the sleeve 32a
As a result of the relative position being shifted, the oil chamber 2 of the volume control cylinder 26 is
6a communicates with the line 58 via the line 60 and the oil chamber 2
Motor drive pressure is supplied to 6a. Here, the oil chamber 26a
Has a larger cross-sectional area in the radial direction than that of the oil chamber 26b.
When the motor drive pressure is supplied to the oil chamber 26a,
The rod 26c of the volume control cylinder 26 is
And move to the left in the figure. And volume control syringe
When the rod 26c of the damper 26 moves to the left in the figure, the variable volume
The capacity of the motor 10 is reduced,
The drive speed of the pilot valve
It rises steplessly . FIG. 2 shows this characteristic of the motor 10.
Is shown as the relationship between the volume v and the rotation speed n of the pilot pressure Pp. Note that the volume control cylinder 26
Rod 26c is servo spool integrated with sleeve 32a
When moving by the amount moved by 32, the line 60 and the line
The communication with the rod 26c is thereby interrupted.
Is stopped, the driving speed of the variable displacement motor 10 is reduced.
The degree is kept constant .

Further , when the variable displacement motor 10 operates at a speed other than the lowest speed,
Motor drive pressure changes when driving at speed
When the spring force exceeds the spring force of the spring 36, the spring 3
Servos up to the position where the spring force of 6 is balanced with the motor drive pressure.
Pool 32 and piston rod 37 move rightward in the figure
I do. Then, the servo spool 32 and the piston lock
When line 37 moves to the right in the figure, line 60 changes to tank 1
8 communicates with the oil chamber of the volume control cylinder 26.
26a becomes the tank pressure. At this time, the volume control cylinder
The motor driving pressure is supplied to the oil chamber 26b through the line 58 to the oil chamber 26b.
Is supplied, the pressure between the oil chamber 26a and the oil chamber 26b is increased.
The rod 26c of the volume control cylinder 26 and
The sleeve 32a increases the capacity of the variable displacement motor 10,
Follow the servo spool 32 in the direction
And thereby the driving speed of the variable displacement motor 10 is reduced.
The speed is automatically reduced according to the load . FIG. 3 shows this characteristic as a relationship between the volume v of the motor 10 and the rotational speed n with respect to the motor driving pressure Pd. The lock
Of the servo spool 32
After moving to the right in the figure by the moved amount, the oil chamber 26a and the oil
The pressure difference between the chamber 26b and the rod 26c and the sleeve
When 32a tries to move further to the right in the figure, the servo
The relative position between the spool 32 and the sleeve 32a may shift.
The line 60 communicates with the line 58 and the oil chamber 26
a and the oil chamber 26b have the same pressure.
As long as 2 does not move to the right in the figure, the rod 26c and
The probe 32a does not move to the right in the figure any more .

The hydraulic drive according to one embodiment of the present invention described above.
In the circuit, the motor drive pressure acting on the servo piston 30
Is smaller than the biasing force of the compression spring 36,
Since the position of the rule 32 is determined by the magnitude of the pilot pressure,
When the motor load is relatively small, the variable displacement motor 10
Stepless at a speed corresponding to the amount of operation of the pilot valve 24
Can be driven. Also, the servo piston 30
The acting motor driving pressure is larger than the urging force of the compression spring 36.
When the servo spool 32 is
Because it is determined by the size, when the motor load is relatively large
The driving speed of the variable displacement motor 10 depends on the magnitude of the load.
Can be adjusted automatically. Therefore, the conventional
Variable capacity when the motor load is relatively small, as in technology
The motor is driven at high speed against the will of the operator,
Alternatively, the drive speed of the variable displacement motor
Does not suddenly switch from medium speed to low speed
Therefore, the operability and safety of construction machinery can be improved.
I can . The preferred embodiment of the device of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and it is needless to say that various design changes can be made without departing from the spirit of the present invention. . For example, each element constituting the priority selecting means can be appropriately set according to the application.

[0018]

As described above, the hydraulic pressure according to the present invention is
According to the drive circuit, when the motor load is relatively small
Variable displacement motors now support pilot valve operation
It can be driven steplessly at speed, and if the motor load is relatively large
Depending driving speed of Kiniwa variable displacement motor to the magnitude of the load
Can be adjusted automatically .

In the present invention, the hydraulic pump can be configured to perform constant horsepower control. However, with such a configuration, the motor drive horsepower is regulated even in the case of a high load, so that the safety described above is reduced. It can be further improved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of a hydraulic drive circuit according to the present invention.

FIG. 2 shows a motor load in the hydraulic drive circuit shown in FIG.
FIG. 7 is a diagram showing the drive characteristics of a variable displacement motor when is relatively small .

FIG. 3 shows a motor load in the hydraulic drive circuit shown in FIG.
FIG. 9 is a diagram showing the drive characteristics of a variable displacement motor when is relatively large .

FIG. 4 is a hydraulic circuit diagram showing a conventional example .

[Explanation of symbols]

 Reference Signs List 12 Volume control device 14 Variable displacement motor 16 Hydraulic pump 18 Tank 20 Switching valve 22 Pilot pump 24 Pilot valve 26 Volume control cylinder 26a Head chamber 26b Rod chamber 26c Rod 28 Volume control valve 30 Servo piston 30a Servo piston left end 32 Servo spool 34 , 36 spring 38 retainer 40 stepped piston 44 stepped cylinder oil chamber 48, 56 shuttle valve 46, 50, 52, 54, 58, 60, 62 line

Claims (2)

(57) [Claims] 1. A hydraulic pump, a variable displacement motor driven by pressure oil from the hydraulic pump, a switching valve for switching a flow direction of pressure oil supplied to the variable displacement motor , and a pilot operation of the switching valve in the hydraulic drive circuit and a pilot valve which, the means for controlling the volume of the variable displacement motor, volume control
A cylinder and the variable volume cylinder through the volume control cylinder.
Servo spool that controls the volume of the motor
The motor drive pressure from the switching valve is applied to one end of the boss spool.
Servo piston to be used and facing this servo piston
And a cylinder disposed on the other end of the servo spool
From inside this cylinder toward the servo spool.
And the piston rod
A compression spring biasing the servo spool side and the cylinder
The stepped cylinder oil chamber in which the pilot pressure is introduced
A stepped piston having a step portion for defining
Restricts the movement of the piston rod in cooperation with the piston
And a bias greater than the biasing force of the compression spring.
Force the stepped piston and retainer into the piston
Hydraulic drive circuit, characterized in that consisted the biasing direction of the head and urging member for urging the opposite direction. 2. The hydraulic drive circuit according to claim 1, wherein the hydraulic pump performs constant horsepower control.