JPH075933A - Liquid pressure controller - Google Patents

Abstract

PURPOSE:To provide a liquid pressure controller which can reduce the power loss. CONSTITUTION:This controller is provided with an acting chamber 7 of a liquid pressure cylinder 14, a pressure chamber 48 of a control cylinder 49 to be moved back and forth by a piston member 46 having a diameter smaller than a piston 1 of the cylinder 14 and communicated to the chamber 7 through a pressure flow path 57, a transfer mechanism 29 moving the piston 1 in the axial direction, and a screw mechanism 56 transferring the member 46 of the cylinder 49 in the axial direction. The path 57 is provided with a valve device 38 which controls the flowing direction of an acting fluid between a tank 3 and the chamber 7. Then, the member 46 of the cylinder 49 is transferred by the drive of the mechanism 56 and the pressure is controlled in the chamber 7 which is linked to the chamber 48.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for controlling the pressure of working liquid supplied to a hydraulic cylinder.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic pressure control device for a hydraulic cylinder for producing constant pressurization for clamping, for example, FIG.
There is a configuration shown in. This is a tank 61 that stores a working liquid and a tank 61 that is driven by an electric motor 62.
A hydraulic pump 63 that discharges the hydraulic fluid stored in the hydraulic cylinder 63, an electromagnetic switching valve 66 that is supplied with the hydraulic fluid discharged by the hydraulic pump 63 and that controls the movement direction of the piston 65 of the hydraulic cylinder 64, The hydraulic fluid is guided to the hydraulic cylinder 64 by the switching control of the switching valve 66, and
A first load flow path 67 for returning the working fluid of FIG.
The second load flow path 68, the supply flow path 69 for supplying the working liquid discharged from the hydraulic pump 63 to the electromagnetic switching valve 66, and the working liquid flowing from the hydraulic cylinder 64 into the electromagnetic switching valve 66 are returned to the tank 61. And a low-pressure flow path 70. And
A proportional electromagnetic relief valve 72 that sets the pressure of the working liquid discharged from the hydraulic pump 63 in proportion to the magnitude of the solenoid drive current supplied from the power supply line 71 is connected to the supply passage 69. Have Reference numeral 73 is a return flow path included in the proportional electromagnetic relief valve 72. A pressure sensor 74 for detecting the pressure of the working liquid acting on the piston 65 of the hydraulic cylinder 64 is connected to the second load passage 68. Reference numeral 75 is a signal line for outputting the pressure of the working liquid detected by the pressure sensor 74 as an electric signal. FIG. 4 shows a state in which the hydraulic cylinder is inactive.

When the electromagnetic switching valve 66 is switched from this state, the supply passage 69 communicates with the second load passage 68 and the low pressure passage 70 communicates with the first load passage 67. Therefore, the working liquid flows into the hydraulic cylinder 64, and the set pressure set by the proportional electromagnetic relief valve 72 can be obtained in the piston 65. The set pressure can be changed by adjusting the magnitude of the solenoid drive current supplied to the proportional electromagnetic relief valve 72 from the power supply line 71.

[0004]

However, in order to obtain the set pressure, the proportional electromagnetic relief valve 72 is connected to the hydraulic pump 63.
The working liquid from the
Since it is returned to the tank 61 from 3 to obtain the set pressure, there is a problem that the power loss is large.

An object of the present invention is to solve the above problems, and an object thereof is to provide a hydraulic control device capable of reducing power loss.

[0006]

Therefore, according to the present invention, a piston, a hydraulic cylinder forming a working chamber with an insertion hole through which the piston is inserted, and a piston member communicating with the working chamber and having a diameter smaller than that of the piston are provided. An adjusting cylinder having an advancing / retreating pressure chamber is provided, and a feed mechanism for moving the piston of this hydraulic cylinder in the axial direction is provided, and the piston member of the adjusting cylinder and the electric motor capable of forward and reverse rotation are connected to each other. Is connected via a screw mechanism for converting the piston member into an axial movement, and a passage connecting the working chamber of the hydraulic cylinder and the tank storing the working fluid is provided. A valve device is provided to allow the working fluid to flow in and out between the working chambers and to prevent the working fluid from flowing out of the working chamber to the tank.

[0007]

According to the structure of the present invention, after the piston of the hydraulic cylinder is moved by the feed mechanism by the required amount, the valve device prevents the working liquid from flowing out of the working chamber into the tank. And moving the piston member to generate a pressure for pressing the piston member in the working chamber. Since the pressure in the working chamber is controlled by adjusting the movement amount of the piston member, it is not necessary to circulate the pressure to the relief valve for obtaining the set pressure as in the conventional example, and the power loss can be reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 1 to 3, reference numeral 1 denotes a piston, which is integrally formed with a piston rod 2 projecting outward and provided with a large diameter hole 3 and a small diameter small hole 4 following it in the axial direction,
It is slidably provided in an insertion hole 6 formed by opening one side of the main body member 5 formed in a rectangular parallelepiped shape. The piston 1 and the insertion hole 6 form a working chamber 7. Reference numeral 8 is a threaded portion of the piston rod 2. A lid member 9 is slidably fitted on the piston rod 2 and fixed to the body member 5 with a bolt (not shown) to seal the opening of the body member 5. The vacant chamber 1 is formed by the piston 1 and the lid member 9.
Forming 0. 11 is a seal member included in the lid member,
Reference numeral 12 is an O-ring provided in the lid member 9, and the vacant chamber 10 is liquid-tightly provided to the outside. A seal member 13 is provided by being externally fitted into a groove provided on the outer circumference of the piston 1, and the working chamber 7 and the empty chamber 10 are provided in a liquid-tight manner. The hydraulic cylinder 14 formed in this manner can be attached to a work machine (not shown) with a flange portion 15 of the main body member 5 using a bolt 16.

A rod-shaped screw shaft 17 has a spiral ball groove 18 formed on one outer peripheral surface thereof. 19 is collar part 2
The nut member having 0 has a spiral ball groove 21 corresponding to the ball groove 18 of the screw shaft 17 on the inner peripheral surface thereof. The ball groove 1 formed on the outer peripheral surface of the screw shaft 17
8 and a ball groove 21 formed on the inner peripheral surface of the nut member 19 with a ball 22 interposed therebetween and the screw shaft 17 and the nut member 1
9 is provided by screwing, and the nut member 19 is provided so as to be movable in the axial direction by the rotation of the screw shaft 17. Between the ball 22 and the ball groove 18 of the screw shaft 17, and between the ball 22
And a ball groove 21 of the nut member 19, there is a screwing play in which the screw shaft 17 and the nut member 19 relatively move in the axial direction. L ₁ + L ₂ is the amount of play. The feed screw 23 formed of a ball screw having the above-described structure inserts one of the screw shafts 17 into the small-diameter hole 4 formed in the piston 1 and inserts the nut member 19 that is screwed into the screw shaft 17 into the large-diameter hole 3. The nut member 19 is fitted and fixed to the piston 1 with a bolt, and the other side of the screw shaft 17 is provided so as to protrude through the hole 24 that is bored outward from the working chamber 7 of the hydraulic cylinder 14. , A bearing 25 at the end of the hydraulic cylinder 14.
It is supported by. Reference numeral 26 denotes a DC motor (hereinafter referred to as an electric motor), a drive shaft 27 of which is connected to a screw shaft 17 of a feed screw 23, and a side plate member 28 provided on the hydraulic cylinder 14.
It is fixed with bolts. The hydraulic cylinder 1 is connected to the electric motor 26 and the feed screw 23 connected to the electric motor 26.
A feed mechanism 29 for slidably driving the piston 1 of No. 4 into the insertion hole 6 is configured. Reference numeral 30 denotes a load flow path, which is provided inside the main body member 5 and opens into the working chamber 7 of the hydraulic cylinder 14. Reference numeral 31 denotes a supply flow path, which is provided inside the main body member 5 and opens on the lower surface of the main body member 5. Reference numeral 32 denotes a low-pressure flow path, which is provided in the main body member 5 and opens to the empty chamber 10 of the hydraulic cylinder 14 and to the lower surface of the main body member 5.

33 is a tank for storing the working liquid 35,
It is fixed to the lower surface of the main body member 5. 34 is a working liquid 35
Is connected to the supply flow path 31 on the lower surface of the main body member 5 and is suspended in the working liquid 35.
Reference numeral 36 denotes a return pipe, which is provided on the lower surface of the main body member 5 for the low pressure passage 32.
And is provided so as to hang down in the working liquid 35. 37
Is a strainer, which is fixed to the suction pipe 34.

Reference numeral 38 denotes an electromagnetic switching valve forming a valve device, which is a two-port two-position type equipped with a check valve 39. The input port 40 thereof is connected to the supply flow passage 31 and the output port 41 is connected. It is fixed to the upper surface of the main body member 5 in communication with the load passage 30. Reference numeral 42 denotes a solenoid fixedly mounted on the electromagnetic switching valve 38, which controls switching of the electromagnetic switching valve 38 based on a solenoid drive current supplied from a power supply line 43. Further, the electromagnetic switching valve 38 flows only from the supply passage 31 to the load passage 30 by the check valve 39 in the operating position obtained by energizing the solenoid 42 through the supply passage 31 and the load passage 30 at the normal position. It is operated so that it can be switched.

Reference numeral 44 denotes a drive member formed in an L shape, and one side thereof has an insertion hole 4 provided in the main body member 5 of the hydraulic cylinder 14.
5, a piston member 46 that slides in a liquid-tight manner is installed, and on the other side, a nut member 47 having an internal thread formed on the inner peripheral surface is installed. The piston member 46 has a significantly smaller diameter than the piston 1. 48 is the insertion hole 45 and the piston member 4
A pressure chamber formed by 6 and 6. The insertion hole 45 and the piston member 46 form an adjustment cylinder 49. Reference numeral 50 denotes a rod-shaped male screw member having an outer peripheral surface formed with a male screw, which is rotatably fitted into a bush 52 of an attachment member 51 having one end projecting outward from the side plate member 28 and the other end being hydraulically pressed. A bearing 53 provided by being fitted into the side plate member 28 of the cylinder 14 is pivotally supported. An electric motor 54 has a drive shaft 55 connected to the male screw member 50 and is fixed to the side plate member 28. The nut 47 is a male screw member 5
It is provided by being screwed to 0, and the leftward end of the drive member 44 is regulated. The male screw member 50 and the nut 47 form a screw mechanism 56. Reference numeral 57 denotes a pressing flow path, which is provided in the main body member 5 of the hydraulic cylinder 14 and opens to the pressure chamber 48 and the working chamber 7 of the hydraulic cylinder 14. Reference numeral 58 is a pressure sensor connected to the load flow path 30 and includes a motor 5
No. 4 is configured to be normally or reversely rotated or stopped by feedback control so that the pressure detected by the pressure sensor 58 is maintained at a predetermined value.

Next, the operation of this structure will be described. It is assumed that the piston 1, the piston member 46, and the drive member 44 are initially on the right end side in FIG. 1, and the electromagnetic switching valve 38 is in the normal position. Drives the electric motor 26 of the feeding mechanism 29,
The feed screw 23 drives the piston 1 in the insertion hole 6 of the hydraulic cylinder 14 to the left in FIG. 1, and a clamp member (not shown) connected to the screw portion 8 of the piston rod 2 formed integrally with the piston 1 is used. Clamp the work. Then, based on the load with which the clamp member clamps the workpiece, the current supplied to the electric motor 26 gradually increases, and when the current reaches a predetermined value, the electric current supplied to the electric motor 26 is cut off.
The electric motor 26 is stopped. At this time, as shown in FIG. 3, the ball 22 is in contact with the right end of the ball groove 18 and the left end of the ball groove 21.

While the piston 1 is driven through the insertion hole 6, a negative pressure is generated in the working chamber 7 of the hydraulic cylinder 14 as the volume of the working chamber 7 increases, and the electromagnetic switching valve 38 is in the normal position. Therefore, due to the pressure difference between the working chamber 7 and the tank 33 based on this negative pressure, the working liquid 35 stored in the tank 33 is stored.
Circulates through the supply channel 31 and flows from the load channel 30 into the working chamber 7.
Flow into the pressure chamber 48 from the pressing channel 57. The working liquid 35 flows in until the pressure in the working chamber 7 becomes substantially the same as the pressure in the tank 33, and the working liquid 7 is filled in the working liquid 7. The pressure at this time is detected by the pressure sensor 58, and the pressure in the working chamber 7 is
When the pressure becomes equal to the internal pressure, the solenoid 4 of the electromagnetic switching valve 38
A drive current is passed through the solenoid valve 2 to switch the electromagnetic switching valve 38 to the operating position so that the check valve 39 prevents the working liquid 35 filled in the working chamber 7 from flowing back to the tank 33.

Then, based on the pressure detection by the pressure sensor 58, the drive of the electric motor 54 is started under the feedback control. That is, since the inside of the working chamber 7 has the same atmospheric pressure as the tank 33, the electric motor 54 is rotated in one direction to move the piston member 46 to the left in FIG. As a result, the piston member 46 that is liquid-tightly inserted in the pressure chamber 48 is inserted.
1 to the left in FIG. 1 to drive the hydraulic liquid 3 in the pressure chamber 48.
Compress 5. The compressed working liquid 35 acts on the working chamber 7 from the pressing channel 57. Therefore, the pressure in the working chamber 7 rises and pushes the piston 1 to the left in FIG. The nut member 19 fixedly provided on the piston 1 has a play (L) between the ball groove 21 formed on the inner peripheral surface thereof and the ball 22 screwed into the ball groove 21.
₁ + L ₂ ), the piston 1 moves slightly to the left in FIG. 1 within this play. Since the pressure in the working chamber 7 is detected by the pressure sensor 58,
When this reaches a predetermined pressure, the electric motor 54 is stopped.
As a result, a predetermined pressure in the working chamber 7 acts on the piston 1, so that the piston rod 2 is pressed with a predetermined force, and the clamp member connected to the piston rod clamps the work with a predetermined force.

When the clamping force becomes larger than a predetermined force due to a change in the posture of the work during the machining of the work, the pressure in the working chamber 7 increases above the predetermined pressure, and when the clamping force becomes smaller, the pressure in the working chamber 7 exceeds the predetermined pressure. Decrease. Since this pressure change is detected by the pressure sensor 58, when the pressure increases, the piston member 46 is moved to the right in FIG.
8 to increase the volume, and in the case of pressure reduction, to move the piston member 46 to the left to decrease the volume of the pressure chamber 48, the electric motor 54 is rotationally driven in one or the other direction to move the action chamber. The inside of 7 is maintained at a predetermined pressure. As a result, the clamping force is maintained at a predetermined force without becoming too large during deformation of the workpiece and causing deformation of the workpiece, or becoming too small to make the clamping force insufficient. When the work machining is completed, the electromagnetic switching valve 38 is set to the normal position, and the driving of the electric motor 54 under the feedback control is completed. Then, the piston 1 and the piston member 46 are returned to the initial position on the right end side by the electric motors 26 and 54. At this time, the working liquid from the working chamber 7 is returned to the tank 33 through the electromagnetic switching valve 38, and to the empty chamber 10. Three
The working liquid from 3 flows in.

In the above operation, the piston 1 hardly moves during the pressure control of the working chamber 7 by the electric motor 54,
Since the piston member 46 has a small amount of movement even if it has moved, the amount of flow in and out of the piston member 46 is also small, and a large amount of power is not required to drive the electric motor 54.
Unlike the conventional hydraulic pump, there is no need to deal with an increase in oil temperature, and the configuration is simple and inexpensive. Further, the electric motors 26, 54, the tank 33, and other parts are integrally connected to the main body member 5, and the piston member 46 has a smaller diameter than the piston of the hydraulic cylinder 14, and the shaft is driven by the electric motor 54 via a screw mechanism. Since the motor 54 is moved in the direction, a small torque motor can be used for the electric motor 54, and the entire apparatus can be downsized. Further, since the electric motor 54 is driven by feedback control, the pressure to the working chamber 7 can be accurately controlled.

Although the electric motor and the ball screw are used as the feed mechanism in the embodiment, the piston may be directly driven by using the air cylinder, and the on-off valve may be used as the valve device. Further, although the DC motor is used for the reference numeral 26, it may be replaced with a stepping motor, and the stepping motor is stopped before the clamp member clamps the work by supplying a predetermined number of pulses to the stepping motor. After that, the electric motor 54 may be driven to clamp the work, and the pressure of the clamp may be controlled.

[0019]

As described above, according to the present invention, a pressure is generated by the movement of the piston member of the adjusting cylinder with respect to the working liquid in the working chamber of the hydraulic cylinder which is prevented from flowing into the tank. Therefore, it is not necessary to supply more hydraulic fluid than the hydraulic cylinder consumes, and power loss can be reduced. Also, the piston member of the adjusting cylinder has a smaller diameter than the piston of the hydraulic cylinder, and converts the rotational output of the electric motor into the axial moving force of the piston member, so the electric motor may be a small one with a small torque. It can be a controller.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a hydraulic control device showing an embodiment of the present invention.

FIG. 2 is a block diagram of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of a feed screw included in a feed mechanism.

FIG. 4 is a block diagram of a conventional hydraulic control device.

[Explanation of symbols]

 1 Piston 6 Insertion Hole 7 Working Chamber 14 Hydraulic Cylinder 29 Feed Mechanism 33 Tank 38 Valve Device 48 Pressure Chamber 49 Adjustment Cylinder 54 Electric Motor 56 Screw Mechanism

Claims (1)

[Claims] 1. A hydraulic cylinder which forms a working chamber with a piston and an insertion hole into which the piston is inserted, and an adjusting cylinder which has a pressure chamber which communicates with the working chamber and in which a piston member having a diameter smaller than that of the piston advances and retreats. And a feed mechanism for moving the piston of the hydraulic cylinder in the axial direction are provided, and the piston member of the adjusting cylinder and the electric motor capable of forward and reverse rotation are converted into the axial movement of the piston member by the rotational output of the electric motor. A passage connecting the working chamber of the hydraulic cylinder and the tank for storing the working fluid is provided through the screw mechanism.In this passage, the working fluid can be let in and out between the tank and the working chamber, A fluid pressure control device comprising a valve device for blocking outflow of hydraulic fluid from a chamber to a tank.