JPH0546830Y2 - - Google Patents

Description

[Detailed description of the invention] A. Industrial application field This invention is connected to and separated from a hydraulic power source through a hydraulic joint, and the hydraulic pressure at the time of connection drives a clamper through a hydraulic cylinder to clamp a member to be clamped. The present invention relates to a hydraulic clamp circuit for clamping onto a fixed member.

B. Prior Art In this type of hydraulic clamp circuit, in order to maintain a clamping force of a predetermined value or more for a predetermined time when the clamp circuit is separated from the hydraulic power source, an accumulator is connected to the high pressure cylinder chamber side of the hydraulic cylinder.
Guarantees pressure drop due to leakage from various parts of the circuit.

C. Problems that the device aims to solve However, this hydraulic clamp circuit becomes a closed circuit when it is separated from the hydraulic source.
If pressure oil leaking from the high-pressure side within the circuit flows into a pipe connected to the low-pressure chamber side of the hydraulic cylinder, the pressure difference between the pressure on the high-pressure chamber side and the pressure on the low-pressure chamber side of the hydraulic cylinder gradually decreases, causing a problem in that the output of the hydraulic cylinder decreases and the clamping force becomes insufficient.

An object of the present invention is to provide a hydraulic clamp circuit that prevents the clamping force from decreasing due to internal leakage.

D. Means for Solving Problems The present invention provides a hydraulic clamp circuit that is connected to and separated from a hydraulic power source via a hydraulic joint, and that uses the hydraulic pressure at the time of connection to drive a hydraulic cylinder to clamp a member to be clamped to a fixed member. Applies to.

And the above-mentioned problem of reduced clamping force is
It is equipped with a high-pressure accumulator that communicates with the cylinder chamber of the hydraulic cylinder for clamping, which becomes a high-pressure chamber when clamping, and a low-pressure accumulator that communicates with the cylinder chamber of the hydraulic cylinder, which becomes a low-pressure chamber when clamping. This problem is solved by a hydraulic clamp circuit that maintains the output of the hydraulic cylinder above a predetermined value and maintains the clamping force.

E Effect Even if the pressure oil on the high pressure side leaks to the low pressure side, it is absorbed by the low pressure accumulator on the low pressure side, and the cylinder chamber pressure on the low pressure side is prevented from increasing. Therefore, even if there is an internal leak, the differential pressure between the high and low cylinder chambers in the hydraulic cylinder does not become as small as in the conventional case, and a clamping force greater than or equal to a predetermined value can be maintained for a predetermined period of time or longer.

F Example One example will be described with reference to FIGS. 1 and 2.

FIG. 2 shows a schematic plan view of a pallet changer for a machining center using the hydraulic clamp circuit according to this embodiment. In a machine tool, for example, a machining center 1, various cutting tools are exchangeably attached to a rotating main shaft 1a. This processing by machining center 1 is performed on table 1b in pit PT.
The work 2 is carried onto the table 1b while being mounted on the pallet 3, and is processed. The table 1b is movable along the rail 1c and can be rotated by a device not shown. Workpiece loading and unloading stations are provided on the left and right sides of the pit PT, and transfer devices 4 and 5 are provided on each of the workpiece loading and unloading stations, and the pallet 3 is transferred between the table 1b and the workpiece loading and unloading station.

A transfer device 4 installed at a workpiece loading/unloading station located on the left side of the figure carries a pallet 3 to a table 1b, where a workpiece 2 before processing is loaded onto the pallet 3. A transfer device 5 installed at the workpiece loading/unloading station on the right side carries out the pallet 3 from the table 1b, and moves the processed workpiece 2 together with the pallet 3 from the table 1b. That is, as shown by the arrow, the workpiece 2 is transferred together with the pallet 3 to the table 1b at the pallet loading/unloading position by the transfer device 4 on the left side.
The table 1b is carried in along the rail 1c.
The table 1b is moved to the workpiece machining position of the machining center 1 and machining is performed, and after the machining is completed, the table 1b is moved to the pallet carry-out/unload position and is carried out together with the pallet 3 by the transfer device 5 on the right side.

Here, the pallet (clamped member) 3 transferred onto the table (fixed member) 1b is moved by a clamper 3 driven by a hydraulic cylinder 38 shown in FIG.
It is clamped by 7A and 37B. table 1
b moves along the rail 1c between the workpiece loading/unloading position and the workpiece processing position, so in this embodiment, a clamping accumulator is provided on the table 1b, and the hydraulic power source is turned on when the table 1b is at the pallet loading/unloading position. The unit and the hydraulic clamp circuit 40 are connected via the coupling device 1d, and pressure oil is supplied to the accumulator to accumulate pressure, and the table 1b
When the machine is in the workpiece processing position, the hydraulic clamp circuit and the hydraulic power source unit are separated by the coupling device 1d, and the clamping force is maintained by the pressure oil accumulated in the accumulator.

FIG. 1 shows an overall diagram of the hydraulic circuit of the pallet changer. 30 indicates a hydraulic power source unit, which includes a variable displacement hydraulic pump 31 and three electromagnetic switching valves 32.
~34. The electromagnetic switching valve 34 has hydraulic joints (hereinafter simply referred to as joints) 25C, 25D and 12.
C and 12D, it is connected to the hydraulic clamp circuit 40 according to the present invention. In addition, the electromagnetic switching valve 3
3 is a positioning pin hydraulic cylinder 36A, 36B via joints 25A, 25B and 12A, 12B.
It is connected to the. Furthermore, the electromagnetic switching valve 32 is
It is connected to the joint driving hydraulic cylinder 23 via pipes 35A and 35BA.

Here, the joints 25A to 25D are provided on the hydraulic power source unit side, and the joints 12A to 12D are provided on the table 1b shown in FIG. 2. The joints 25 and 12 are engaged and disengaged by the expansion and contraction of the hydraulic cylinder 23 when the table 1b is at the above-mentioned pallet loading/unloading position.

The hydraulic clamp circuit 40 is connected to ten clamp hydraulic cylinders 38, a high pressure accumulator 39 connected to a rod chamber 38R which is a high pressure chamber of the hydraulic cylinders 38, and a bottom chamber 38B which is a low pressure chamber of the hydraulic cylinders 38. and a low-pressure accumulator 40. Clamp hydraulic cylinder 38
The pistons are provided with clampers 37A and 37B, respectively, and by pulling the clamper 37, the pallet 3 is clamped to the table 1b, and by pushing the clamper 37, the pallet 3 is released from the table 1b.

The three electromagnetic switching valves 32 to 34 are connected to a sequencer 50.
Switching is controlled by the sequencer 50, and the sequencer 50 includes:
A limit switch 51 for the coupling device, a limit switch 52 for the positioning pin, and a pressure switch 53 that detects the pressure in the high pressure chamber of the clamp hydraulic cylinder 38 are connected, and a sequencer 50 sequentially controls each actuator based on signals from each switch. Control.

First, the operation of each part during unloading of the pallet 3 will be explained.

After the machining center 1 finishes machining, the table 1b is moved to the pallet loading/unloading position. Next, the electromagnetic switching valve 32 is controlled by the sequencer 50.
The above-mentioned hydraulic cylinder 23 extends to engage the joints 25 and 12. When the joint is properly engaged, the limit switch 51 is turned on, and the sequencer 50 supplies a switching signal to the electromagnetic switching valve 34 to close the bottom chamber 38B of the clamping hydraulic cylinder 38.
The hydraulic pump 31 communicates with the rod chamber 38R and the tank. As a result, clampers 37A and 38B
The clamp on pallet 3 is released. Next, the transfer device 5 is moved to the table 1b side and engaged with the pallet 3, and then the sequencer 50 switches the electromagnetic switching valve 33 to drive the positioning pin hydraulic cylinder 36 to remove the positioning pin from the pallet 3 and transfer it. The pallet 3 is carried out by the loading device 5 to the work loading/unloading station on the right side.

Next, the operation of each part when the pallet 3 is carried in will be explained.

The pallet 3 is carried onto the table 1b by the transfer device 4. Next, the electromagnetic switching valve 33 is switched under the control of the sequencer 50, the positioning pin hydraulic cylinder 36 is extended, and the positioning pin is inserted into the hole in the pallet 3. Thereafter, the engagement between the pallet 3 and the transfer device 4 is released, and the transfer device 4 is returned to the work loading/unloading station. Further, the electromagnetic switching valve 34 is switched under the control of the sequencer 50 to connect the rod chamber 38R of the clamping hydraulic cylinder 38 to the hydraulic pump 31 and the bottom chamber 38B to the tank. As a result, hydraulic pressure is accumulated in the high-pressure accumulator 39, the hydraulic cylinder 38 is contracted, and the pallet 3 is clamped to the table 1b by the clamper 37. At this time, the hydraulic clamp circuit 40
When the pressure on the high pressure side of the hydraulic cylinder 23 exceeds a predetermined value, the pressure switch 53 is turned on, and the sequencer 50 switches the electromagnetic switching valve 32 to contract the hydraulic cylinder 23 and separate the joints 12 and 25.

Although the hydraulic clamp circuit 40 is separated from the hydraulic pressure source by the separation of the joints 12 and 25, a predetermined clamping force is maintained by the hydraulic pressure accumulated in the high pressure accumulator 39. In addition, even if an internal leak occurs over time and pressure oil from the high pressure side flows to the low pressure side,
An accumulator 40 set to a low pressure is disposed on the low pressure side to prevent pressure from increasing on the low pressure side. For this reason, the clamp hydraulic cylinder 38
The differential pressure between the rod chamber 38R and the bottom chamber 38B does not change over a predetermined period of time, and a clamping force greater than or equal to a predetermined value can be maintained for a predetermined period of time.

Although the above description has been made regarding a pallet changer, the present invention can also be applied to clamp circuits of various other devices. Further, the number of clamping hydraulic cylinders is not limited to ten, and although the pallet 3 is clamped and unclamped by pushing and pulling the clamper 37, it is not necessary to use such a clamping structure.

G. Effect of the invention According to the invention, a high-pressure accumulator and a low-pressure accumulator are connected to both the high and low cylinder chambers of the clamping hydraulic cylinder, so even if pressure oil on the high-pressure side leaks to the low-pressure side, the pressure The oil is absorbed into the low-pressure accumulator on the low-pressure side, and the pressure in the cylinder chamber on the low-pressure side is prevented from increasing. Therefore, even if there is an internal leak, the differential pressure between the high and low cylinder chambers in the hydraulic cylinder does not become as small as in the conventional case, and a clamping force greater than or equal to a predetermined value can be maintained for a predetermined period of time or longer.

[Brief explanation of the drawing]

1 and 2 illustrate an embodiment in which the hydraulic clamp circuit according to the present invention is applied to a pallet changer, and FIG. 1 is a hydraulic circuit diagram of the pallet changer. FIG. 2 is a plan view illustrating the pallet changer. 12A-12B...Joint, 23...Hydraulic cylinder, 25A-25D...Joint, 30...Hydraulic power source unit, 31...Hydraulic pump, 32-34...Solenoid switching valve, 37A, 37B...Clamper, 38
... Hydraulic cylinder, 39 ... High pressure accumulator, 40 ... Low pressure accumulator, 50 ... Sequencer, 51, 52 ... Limit switch, 53
...Pressure switch.

Claims (1)

[Scope of Claim for Utility Model Registration] A hydraulic clamping circuit that is connected to and separated from a hydraulic power source via a hydraulic joint, and drives a hydraulic cylinder by the hydraulic pressure at the time of connection to clamp a member to be clamped to a fixed member, comprising: a clamp; A high-pressure accumulator that communicates with a cylinder chamber of the hydraulic cylinder that becomes a high-pressure chamber when clamping, and a low-pressure accumulator that communicates with a cylinder chamber of the hydraulic cylinder that becomes a low-pressure chamber when clamping. A hydraulic clamp circuit characterized in that the output of the hydraulic cylinder is kept above a predetermined value to maintain clamping force.