JPH0618753Y2 - Hydraulic circuit - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a hydraulic circuit applied to a machine tool such as an NC milling machine with few hydraulic drive devices, and particularly to a hydraulic circuit used for changing the spindle speed of the machine tool. Regarding

[Conventional technology]

Unlike a machining center, it is not necessary to use a lot of hydraulically driven equipment in an NC milling machine, but due to the current state of automation and labor saving of machine tools, even in NC milling machines, only the spindle speed switching must be automated. However, for that purpose, a high-pressure hydraulic circuit using a hydraulic cylinder or the like is required.

FIG. 2 shows a conventional spindle switching hydraulic circuit. In the figure, 1 is a spindle head of an NC milling machine, 2 is a hydraulic cylinder for spindle speed switching mounted on the spindle head 1,
This hydraulic cylinder 2 has 4 ports on the rod and head side.
The ports A and B of the position switching type solenoid valve 3 are connected to each other, the discharge side of the variable discharge type high pressure pump 4 is connected to the port P of the solenoid valve 3, and the port R is connected to the tank 5. . The suction side of the high-pressure pump 4 is connected to the tank 5. 6 is a constant discharge type low pressure pump for supplying lubricating oil to gears, bearings, etc. inside the spindle head, the discharge side of which is connected to the spindle head 1 through an oil supply pipe 7 and the suction side is connected to a lubricating oil tank 8. Has been done. Reference numeral 8a is a lubricating oil return pipe that connects the spindle head 1 and the tank 8.

In the conventional hydraulic circuit configured as described above, when the low pressure pump 6 is driven, the lubricating oil in the tank 8 is supplied to the main spindle head 1 through the low pressure pump 6 and the oil supply pipe 7, and the internal gear And lubricate the bearings of the main shaft.

On the other hand, when the solenoid valve 3 is switched to the left-side offset position OP1 shown in FIG. 2 while the high-pressure pump 4 is activated, the discharge operating oil from the high-pressure pump 4 is discharged from the port P of the solenoid valve 3 → It is supplied to the rod side chamber of the hydraulic cylinder 2 through the port,
Is moved backward in the direction of arrow X1 to switch the spindle speed to the high speed side. Then, this speed switching state is maintained by the hydraulic pressure supplied from the high-pressure pump 4. When the solenoid valve 3 is switched to the offset position OP2 shown on the right side in FIG. 2, the high-pressure pump 4 discharges oil from the hydraulic cylinder 2.
Is supplied to the head side chamber, and the hydraulic cylinder 2 is moved forward to switch the spindle speed to the low speed side.

The high-pressure pump 4 generates a high pressure only when the hydraulic cylinder 2 is operated, and after the hydraulic cylinder 2 reaches the retreat end or the forward end, the pump and the operation are performed so that the position can be maintained. It is designed to prevent heating of oil.

[Problems to be solved by the invention]

In the conventional hydraulic circuit as described above, the hydraulic circuit for high pressure and the lubricating circuit for low pressure must be separately provided for two systems, which complicates the piping path, requires two tanks, and is expensive. Since a variable discharge pump is required and the high-pressure pump needs to be constantly operated, there is a problem that the operating cost of the hydraulic circuit increases.

[Purpose of device]

The present invention has been made to solve the above-mentioned problems. The high-pressure hydraulic circuit and the low-pressure lubrication circuit supplied to the spindle head are integrated into one system to simplify the piping path and to make the expensive variable An object is to provide a low-cost and efficient hydraulic circuit that does not require a discharge pump.

[Means for solving problems]

The hydraulic circuit according to the present invention includes a hydraulic cylinder for switching the spindle speed of a machine tool, a constant discharge type low pressure pump connected to the hydraulic cylinder via a solenoid valve for switching the forward / backward movement, and a high pressure pump for the high pressure pump. A constant discharge type low pressure pump that is connected in series between the suction side and the oil tank and is constantly operated, and that functions to supply lubricating oil to the inside of the spindle head, and the main cylinder speed can be switched by the hydraulic cylinder. And a means for controlling the stop of the high-pressure pump by detecting the end.

[Operation of the Invention] In the present invention, when switching the spindle speed, the high pressure pump is operated to supply the high pressure hydraulic oil to the hydraulic cylinder,
When the completion of the switching of the spindle speed by this hydraulic cylinder is detected by means such as a limit switch, the operation of the high pressure pump is stopped, and the spindle speed switching position is set by the operating oil pressure supplied from the low pressure pump which is constantly operated. Hold. Therefore, according to the present invention, a hydraulic circuit for high pressure and low pressure for supplying pressure oil to the spindle head can be formed by one system,
The piping route and the oil tank can be shared, and it is possible to provide an efficient hydraulic circuit that is inexpensive and generates little heat.

[Example of device]

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a hydraulic circuit diagram showing an example in which the present invention is applied to spindle speed switching of a vertical NC milling machine and lubrication of a spindle head. The spindle head 1 is provided with a hydraulic cylinder 2 for switching the spindle speed. There is. The rod side and head side of the hydraulic cylinder 2 are 4 ports 3 position switching type solenoid valve 3
Of the solenoid valve 3 is connected to the discharge side of a constant discharge type high-pressure pump 10 via a check valve 9 which is opened by the pump discharge pressure. The port R of the solenoid valve 3 is connected to a strainer 13 of a tank 12 that also serves as lubricating oil and hydraulic oil via a pipe line 11. On the suction side of the high pressure pump 10, a constant discharge type low pressure pump 1 is provided through a check valve 14 that opens at the pump discharge pressure.
The discharge side of 5 is connected, and the suction side of the low-pressure pump 15 is connected to the inside of the tank 12 via a strainer 13.
Further, the discharge side of the low pressure pump 15 is connected to the spindle head 1 by a supply pipe 7 via a throttle valve 16, and a part of the discharge oil from the low pressure pump 15 is supplied to the inside of the spindle head 1 as lubricating oil. It is like this. LS1 is a limit switch for detecting the backward end of the hydraulic cylinder 2 and LS2 is a limit switch for detecting the forward end of the hydraulic cylinder 2.

The high-pressure pump 10 and the low-pressure pump 15 respectively have relief valves 10a and 15a that use the discharge pressure as a pilot operating pressure.

Next, the operation of this embodiment configured as described above will be described.

First, when it is not necessary to change the spindle speed, the high pressure pump 1
0 is stopped, and the low pressure pump 15 is constantly operating. Therefore, the low-pressure pump 15 is constantly operated so that the hydraulic oil in the oil tank 12 is sucked up through the strainer 13 and the oil discharged to the discharge side is 2
One of them is supplied to the inside of the spindle head 1 through the throttle valve 16 and the pipe 7 as lubricating oil for gears, bearings, etc., and the other is checked valve 14 → high pressure pump 10 at rest → check valve 9 → It is supplied to the rod side chamber of the hydraulic cylinder 2 through the solenoid valve 3 and holds the hydraulic cylinder 2 at the retracted end. This is a low pressure pump 1
The constant operation of 5 constantly applies pressure to the hydraulic cylinder 2 to replenish the oil leak inside the hydraulic cylinder 2,
This is done by ensuring that the retracted position is maintained. In order to maintain the position of the hydraulic cylinder 2, the pressure and flow rate of the low pressure pump 15 are sufficient.

In general, oil leakage is a phenomenon that cannot be basically avoided when handling hydraulic equipment, and in this embodiment as well, the oil supplied to the hydraulic cylinder 2 by the high-pressure pump 10 is not in the hydraulic circuit shown in the drawing. Although it is reversely stopped by the check valve 9, there is actually internal leakage of the seal portion of the hydraulic cylinder 2, the solenoid valve 3, the check valve 9, etc., so even after the high pressure pump 10 is stopped, ,
It is necessary to pressurize the hydraulic cylinder 2. The low-pressure pump 15 is used as this pressurizing function. When the hydraulic cylinder 2 is held at the backward end, the main shaft speed is switched to the high speed side, and the high pressure pump 10 is stopped and controlled by the limit switch LS1 that detects the backward end.
The check valves 9 and 14 prevent the oil from flowing backward due to external factors or the activation of the high pressure pump 10.

Next, the case of switching the spindle speed will be described.

In this case, first, when a low speed switching button (not shown) provided on the operation panel of the NC milling machine is pressed, the solenoid valve 3 is switched to the offset position OP2 side and the high pressure pump 10 is started. As a result, most of the oil discharged from the low pressure pump 15 is sucked to the high pressure pump 10 side through the check valve 14,
It becomes high-pressure hydraulic fluid, and the hydraulic cylinder 2 passes through the offset position OP2 of the check valve 9 and the solenoid valve 3.
Is supplied to the head side chamber. This allows the hydraulic cylinder 2
Moves forward to switch the spindle speed of the spindle head 1 to the low speed side. At this time, the oil in the rod side chamber is returned to the suction side of the low pressure pump 15 through the solenoid valve 3 and the passage 11.

When the hydraulic cylinder 3 reaches the forward end, the limit switch LS2 operates to stop and control the high pressure pump 10. Then, the hydraulic cylinder 2 is held by the operating hydraulic pressure supplied from the low-pressure pump 15 in the forward end position, that is, in the state where the spindle speed is switched to the low speed side.

Similarly, when switching from the above-mentioned main spindle low speed switching state to the high speed side, a solenoid valve 3 is pushed to an offset position PO1 shown in FIG. 1 by pressing a high speed switching button (not shown) on an operation panel (not shown). At the same time, the high-pressure pump 10 is activated to supply high-pressure hydraulic oil to the rod-side chamber of the hydraulic cylinder 2, and the hydraulic cylinder 2 is moved backward to switch the spindle speed of the spindle head 1 to the high speed side. Then, when the hydraulic cylinder 2 reaches the retracted end and the limit switch LS1 operates, the high speed pump 10 stops.

As described above, in this embodiment, the high-pressure pump 10 can satisfy the operating conditions of the high-pressure hydraulic circuit necessary for the spindle speed switching only when the hydraulic cylinder 2 for spindle speed switching is operated. Since the high-pressure pump 10 does not operate except when the spindle speed is changed, heat inflow from the pump to the machine body can be suppressed as much as possible, and overheating of the machine and deterioration of hydraulic oil can be prevented, and for internal lubrication of the spindle. Circuit and the high-pressure circuit for spindle speed switching can be integrated into one system, which allows the piping circuit and oil tank to be shared, and the expensive variable discharge pump can be replaced with a constant discharge pump. The cost of the hydraulic circuit can be reduced.

The low-pressure pump 15 according to the present invention is not limited to the one for lubricating the inside of the spindle head as in the above embodiment, but may be any pump that satisfies the operating conditions of the present invention. Further, the present invention is not limited to the case of being applied to the spindle speed switching of the NC milling machine.

[Effect of device]

As described above, according to the present invention, the discharge side of the high-pressure pump is connected to the main cylinder speed switching hydraulic cylinder of the machine tool through the solenoid valve for switching the forward / backward movement, and the suction side of the high-pressure pump is connected. Means for connecting in series a low-pressure pump which functions between the oil tank and the oil tank and which functions for supplying lubricating oil, and for detecting the completion of the switching of the spindle speed by the hydraulic cylinder to control the stop of the high-pressure pump By this, the high pressure pump is operated only during the spindle speed switching operation so that the operating conditions of the spindle speed switching circuit can be satisfied, so that the high pressure and low pressure circuits can be integrated into one system, and the piping path and oil There is an effect that the tank can be shared, the hydraulic circuit can be simplified and the cost can be reduced, and further, heat inflow from the pump to the machine body and deterioration of oil can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a hydraulic circuit of the present invention, and FIG. 2 is a diagram showing a conventional hydraulic circuit. 1 ... Spindle head, 2 ... Hydraulic cylinder, 3 ... Solenoid valve, 9, 14 ... Check valve, 10 ... High pressure pump, 15 ... Low pressure pump.

Claims (1)

[Scope of utility model registration request] 1. A hydraulic cylinder for switching the spindle speed of a machine tool, and a constant discharge type high-pressure pump connected to the hydraulic cylinder via a solenoid valve for switching its forward / backward movement.
A constant discharge type low pressure pump that is connected in series between the suction side of this high pressure pump and the oil tank and is always operated, and that functions to supply lubricating oil to the inside of the main spindle head, and the main spindle by the above hydraulic cylinder. A hydraulic circuit comprising means for detecting the end of speed switching and stopping and controlling the high-pressure pump.