JPH04289007A - Chuck pressure control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chuck pressure control device for controlling the gripping force of a chuck in a machine tool in which a chuck for gripping a workpiece is opened and closed by a rotary hydraulic cylinder.

0002

[Prior Art] Conventionally, there is a machine tool that grips a workpiece with a chuck, as shown in Fig. 3.
JP-A-62-136302). This machine tool has a main shaft 33 equipped with a chuck 31 at one end and a rotary hydraulic cylinder 32 at the other end, rotatably supported on a stand 34, and a supply/discharge port provided in a sleeve 35 of the rotary hydraulic cylinder 32. The chuck 31 is opened and closed by alternately supplying hydraulic oil to 35a and 35b. Then, with the chuck 31 closed and the workpiece 36 gripped by the claws 31a, the motor 37 is driven to rotate the main shaft 33 and the workpiece 36 is processed. The gripping force of the chuck 31 is the main shaft 3
When the rotation speed of 3 increases, it decreases due to the centrifugal force. Figure 4
shows the relationship between rotational speed and gripping force using an 8-inch chuck and a 15-inch chuck as examples. As the rotation speed increases, the gripping force decreases, and as a result, the workpiece 3
6 may fall off from the claw 31a of the chuck 31. Therefore, as shown in FIG.
By adding a current value proportional to the rotation speed setting signal to the current value generated when the main shaft 33 is stopped and emitting it from the rotation speed setting device 41 that sets the rotation speed of 7 to the electromagnetic proportional pressure reducing valve 38, Hydraulic oil is supplied at a pressure that corresponds to the number of rotations, and the gripping force of the chuck 31 is corrected to a value commensurate with the change in the number of rotations, thereby preventing the workpiece 36 from falling off from the chuck 31. .

0003

However, in the conventional method described above, the pressure characteristics of the electromagnetic proportional pressure reducing valve 38 with respect to the supplied current have hysteresis as shown in FIG. It is not possible to accurately correct the gripping force of the chuck, and there is a problem that the workpiece may fall off the chuck due to a decrease in the gripping force of the chuck, or the workpiece may be damaged due to an excessive gripping force of the chuck. Therefore,
An object of the present invention is to provide a chuck pressure control device that can accurately compensate for changes in chuck gripping force (hereinafter referred to as chuck pressure) due to rotational speed, and can reliably prevent workpieces from falling off or being damaged. There is a particular thing.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a rotary hydraulic cylinder 2 for gripping a workpiece and for opening and closing a chuck 1 attached to one end of a main shaft, and 2 and the hydraulic power source 20, an electromagnetic proportional control valve 3 that controls the pressure of the rotary hydraulic cylinder 2, a pressure detection means 4 that detects the output pressure of the electromagnetic proportional control valve 3, A pressure setting means 5 outputs a pressure command signal corresponding to the rotation speed of the main shaft, and the electromagnetic proportional type It is characterized by comprising a feedback control means 10 for controlling the electromagnetic proportional control valve 3 so that the output pressure of the control valve 3 becomes the pressure represented by the pressure command signal. Further, in the present invention, it is preferable that the pressure detection means 4 is provided at the inlet of the rotary hydraulic cylinder 2 or at a pipe immediately before the rotary hydraulic cylinder 2.

[0005]

[Operation] In the above structure, the pressure setting means 5 outputs a pressure command signal corresponding to the rotation speed of the main shaft, and the feedback control means 10 outputs the pressure command signal output from the pressure setting means 5 and the pressure detection means. Based on the output pressure of the electromagnetic proportional control valve 3 (hereinafter abbreviated as proportional control valve) detected by 4, the proportional Control valve 3. In this way, since the proportional control valve 3 is used and the output pressure of the proportional control valve 3 is feedback-controlled, the output pressure can be controlled with good linearity without hysteresis characteristics with respect to the rotational speed of the main shaft. Therefore, it is possible to reliably prevent the workpiece from falling from the chuck 1 due to the weakening of the gripping force of the chuck 1 due to centrifugal force, or damage to the workpiece due to the gripping force of the chuck 1 being too strong. The pressure detection means 4
is provided near the proportional control valve 3, the pressure inside the rotary hydraulic cylinder 2 is lower than the pressure detected by the pressure detecting means 4 due to pressure loss due to the piping from the proportional control valve 3 to the rotary hydraulic cylinder 2. Become. Therefore, when the rotary hydraulic cylinder 2 is operated by pressure control to close the chuck 1, the pressure inside the rotary hydraulic cylinder 2 becomes lower than the control pressure, so that the operating speed of the rotary hydraulic cylinder 2 is lowered to the target speed. , and the time it takes to close the chuck 1 becomes longer. When the pressure detecting means 4 is provided at the inlet of the rotary hydraulic cylinder 2 or in a pipe immediately before the rotary hydraulic cylinder 2, the pressure detected by the pressure detecting means 4 becomes approximately equal to the pressure inside the rotary hydraulic cylinder 2, and the rotary hydraulic cylinder 2 can be operated at the target speed, and chuck 1 can be operated at the target speed.
The closing time can be shortened.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments. FIG. 1 is a circuit diagram of a chuck pressure control device according to the present invention. This chuck pressure control device includes a 4-port 3-position proportional control valve 3 that has a function of switching the supply direction of hydraulic oil supplied to a rotary hydraulic cylinder 2 that opens and closes a chuck 1, and an output pressure of this proportional control valve 3. a pressure sensor 4 that detects and converts it into a voltage signal, and a pressure setting circuit that creates and outputs a pressure command signal based on the set rotation speed of the main shaft (not shown) to which the chuck 1 and rotary hydraulic cylinder 2 are attached. 5, a compensation circuit 6, a changeover switch 7, a voltage-current conversion circuit 8, a changeover switch 9, and a subtraction circuit 10 as feedback control means. In the chuck 1, when the piston rod 12 of the rotary hydraulic cylinder 2 moves to the right, the wedge plunger 13 moves accordingly.
By this wedge plunger 13, the master jaw 1
4 is pushed in the centrifugal direction, and the claw 15 moves in the centrifugal direction to release the workpiece (not shown). Conversely, when the piston rod 12 moves to the left, the wedge plunger 13 moves to the left, the master jaw 14 moves inward, and the claws 15 move inward to grip the workpiece. When the first solenoid 3a is energized, the proportional control valve 3 supplies hydraulic oil from the hydraulic pump 20 to the cylinder chamber 2b, and the piston rod 1
2 to the left and the second solenoid 3b is excited, the hydraulic oil from the hydraulic pump 20 is transferred to the cylinder chamber 2a.
to move the piston rod 12 to the right. The first solenoid 3a is adapted to adjust the opening degree of the valve depending on the magnitude of the flowing current. Therefore, by controlling the current flowing through the first solenoid 3a, the flow rate and pressure supplied to the cylinder chamber 2b can be controlled.
Thereby, the operating speed and gripping force of the chuck 1 can be controlled. The second solenoid 3b of this proportional control valve 3 has
A control current is supplied from the power source via a switch 30 operated by a solenoid switching signal from the signal output circuit 11. The changeover switch 7 is supplied with a valve opening command signal and a pressure control/flow control switching signal from the signal output circuit 11. Then, when the pressure control/flow rate control switching signal becomes high (H), it switches to the compensation circuit 6 side and goes low (
When it becomes L), it switches to the valve opening command signal side. The changeover switch 9 receives a control stop signal from the signal output circuit 11, opens when the control stop signal becomes high (H), and closes when it becomes low (L). Now, when the chuck 1 is closed to grasp the workpiece from the open state, the signal output circuit 1
1 to low (L) to close the changeover switch 9, and output a low (L) signal as the pressure control/flow rate control changeover signal, the changeover switch 7
is switched to the valve opening command signal side and provides a valve opening command signal. Then, a current corresponding to this valve opening command signal is applied to the first solenoid 3a by the voltage-current conversion circuit 8, the proportional control valve 3 becomes the commanded opening, and the piston 18 adjusts to the flow rate at that opening. The chuck 1 grasps the work by being pushed to the left at a corresponding speed. next,
In order to process the work gripped by this chuck 1,
While rotating the main shaft at the set rotation speed, the changeover switch 7 is switched to the compensation circuit 6 side by setting the pressure control/flow rate control switching signal to high (H), and the pressure control circuit 5 outputs a signal corresponding to the set rotation speed. Outputs pressure command signal. Then, the subtraction circuit 10 converts the pressure command signal and the pressure sensor 4
The difference between the signal and the signal is calculated and the result is output to the compensation circuit 6. This compensation circuit 6 is composed of an integral circuit or the like, and changes the output voltage signal so that the output pressure of the proportional control valve 3 becomes the pressure represented by the pressure command signal. This output voltage is converted into a current by the voltage-current conversion circuit 8 and applied to the first solenoid 3a. Therefore, the output pressure of the proportional control valve 3 becomes the pressure represented by the pressure command signal, and moreover, feedback control provides a characteristic with good linearity without hysteresis as shown in FIG. 2. Therefore, the gripping force of chuck 1 is also accurately corrected according to the set rotation speed, and centrifugal force can weaken the gripping force of chuck 1 and cause the workpiece to drop, or the gripping force of chuck 1 can become too large and damage the workpiece. There's nothing to do. To open the chuck 1, first set the control stop signal to high (H) and open the changeover switch 9, then set the solenoid switching signal to high (H) and close the switch 30, supplying current to the second solenoid 3b. do. Then, the supply direction of hydraulic oil is switched, hydraulic oil is supplied to the cylinder chamber 2a, the piston rod 12 moves to the right, and the chuck 1 opens. Note that while the chuck 1 grasps the workpiece, the power to the proportional control valve 3 is turned off.
or when the hydraulic pump 20 stops, the piston 18
remains stopped at that position, and therefore chuck 1
can maintain the state in which the workpiece is held and prevent the workpiece from falling from the chuck 1. In the above embodiment, the pressure setting circuit (5) is used as a pressure setting means to create and output a pressure command signal based on the set rotation speed of the spindle. It is also possible to use a pressure setting circuit that sets the pressure to a value corresponding to
The pressure setting circuit is not limited to the above pressure setting circuit. Furthermore, in the above embodiment, when the chuck 1 is closed, the rotary hydraulic cylinder 2 is operated by controlling the flow rate based on the valve opening command signal from the signal output circuit 11, but the pressure command from the pressure setting circuit 5 The rotary hydraulic cylinder may be operated by pressure control using a signal. In this case, if the pressure sensor 4 is installed near the proportional control valve 3, the pressure inside the rotary hydraulic cylinder will be detected by the pressure sensor 4 due to the pressure loss caused by the piping from the proportional control valve 3 to the rotary hydraulic cylinder 2. Because the pressure is lower than that of
The pressure in the rotary hydraulic cylinder 2 becomes lower than the control pressure, the operating speed of the piston rod 12 becomes slower than the target speed, and the time for closing the chuck 1 becomes longer. Therefore,
As shown in FIG. 6, a pressure sensor 4 is provided at the inlet of the rotary hydraulic cylinder 2 or at the piping immediately before the rotary hydraulic cylinder 2, and the pressure within the cylinder chamber 2b is made equal to the control pressure, and the chuck 1 is closed for a period of time. shorten. FIG. 7 shows the change in pressure at each point in the circuit. Here, ■ is a chuck-on signal, which corresponds to a signal that closes the changeover switch 9 when the changeover switch 7 is closed. ■
is the detected pressure of the pressure sensor 4, that is, the control pressure. (2) is the discharge pressure of the hydraulic pump 20, and (2) is the pressure on the return side of the rotary hydraulic cylinder 2. Also, ■ is the pressure in the cylinder chamber 2b of the rotary hydraulic cylinder, ■-1 is the pressure sensor 4 installed near the proportional control valve 3, and ■-2 is the pressure sensor 4 installed at the inlet of the rotary hydraulic cylinder 2 or Rotating hydraulic cylinder 2
This is the case when it is installed in the piping just before the. That is, when the chuck-on signal (2) becomes low and pressure control is started, the pressure detected by the pressure sensor (2) immediately becomes the control pressure, and this pressure is maintained even after the cylinder has stopped (the chuck has been closed). When the pressure sensor 4 is installed near the proportional control valve 3, the pressure in the cylinder chamber 2b is lower than the above control pressure by the piping loss while the cylinder is operating, as shown in ■-1. The control pressure is reached after the cylinder stops. Therefore, as described above, the time required to close the chuck 1 becomes longer. on the other hand,
When the pressure sensor 4 is installed at the inlet of the rotary hydraulic cylinder 2 or at the piping immediately before the rotary hydraulic cylinder 2, the pressure in the cylinder chamber 2b quickly reaches the control pressure as shown in ■-2, and the control pressure is used to control the cylinder pressure. works. Therefore, the chuck 1 can be closed in a short time.

[0007]

As is clear from the above, the chuck pressure control device of the present invention is provided between a rotary hydraulic cylinder for opening and closing the chuck and a hydraulic power source, and the chuck pressure control device is provided between a rotary hydraulic cylinder for opening and closing the chuck and a hydraulic power source, and the chuck pressure control device is provided between a rotary hydraulic cylinder for opening and closing the chuck and a hydraulic power source, and that an electromagnetic proportional control valve for switching, a pressure detection means for detecting the output pressure of the electromagnetic proportional control valve, a pressure setting means for outputting a pressure command signal corresponding to the rotation speed of the main shaft, and this pressure setting means. Control the electromagnetic proportional control valve so that the output pressure of the electromagnetic proportional control valve becomes the pressure indicated by the pressure command signal based on the pressure command signal output from the pressure command signal and the output pressure detected by the pressure detection means. Since the output pressure of the electromagnetic proportional control valve has no hysteresis with respect to the rotation speed of the main shaft and can be controlled with good linearity, the gripping force of the chuck can be controlled according to the rotation speed. It can be accurately corrected according to the situation, and it is possible to reliably prevent the workpiece from falling off the chuck due to the chuck's gripping force weakening due to centrifugal force, or the workpiece being damaged due to the chuck's gripping force being too strong. In addition, by providing the above-mentioned pressure detection means at the inlet of the rotary hydraulic cylinder or at the piping immediately before the rotary hydraulic cylinder, when the rotary hydraulic cylinder is operated by pressure control to close the chuck, the pressure inside the rotary hydraulic cylinder can be adjusted to the control pressure. Therefore, the operating speed of the rotary hydraulic cylinder can be increased and the chuck closing time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between pressure command voltage and pressure in the above embodiment.

FIG. 3 is a hydraulic circuit diagram showing a conventional example.

FIG. 4 is a diagram showing the relationship between chuck gripping force and rotation speed.

FIG. 5 is a diagram showing the relationship between solenoid supply current and pressure in the conventional example.

FIG. 6 is a hydraulic circuit diagram in the case where the pressure sensor is provided near the rotary hydraulic cylinder in the above embodiment.

FIG. 7 is a diagram showing the pressure at each part when the chuck is closed by pressure control in the above embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Chuck, 2... Rotating hydraulic cylinder, 3... Electromagnetic proportional control valve, 4... Pressure sensor, 5... Pressure setting circuit, 6... Compensation circuit, 7, 9... Changeover switch, 8... Voltage current converter, 1
0...Subtraction circuit, 11...Signal output circuit, 20...Hydraulic pump.

Claims (2)

[Claims] Claim 1: A rotary hydraulic cylinder (2) for grasping a workpiece and for opening and closing a chuck (1) attached to one end of the main shaft, and a connection between the rotary hydraulic cylinder (2) and a hydraulic power source (20). The rotary hydraulic cylinder (
2) an electromagnetic proportional control valve (3) for controlling the pressure; a pressure detection means (4) for detecting the output pressure of the electromagnetic proportional control valve (3); and a pressure command corresponding to the rotation speed of the main shaft. A pressure setting means (5) for outputting a signal, and a pressure setting means (5) for outputting a signal.
5) and the pressure command signal output from the pressure detection means (
4) Feedback control means for controlling the electromagnetic proportional control valve (3) based on the detected output pressure so that the output pressure of the electromagnetic proportional control valve (3) becomes the pressure indicated by the pressure command signal. (10) A chuck pressure control device characterized by comprising: 2. The pressure detecting means (4) is provided at the inlet of the rotary hydraulic cylinder (2) or in a pipe immediately before the rotary hydraulic cylinder (2). Chuck pressure control device.