JPS6021143Y2 - Machine tool feed control device - Google Patents

Description

[Detailed Description of the Invention] Technical Field This invention relates to a feed control device for a machine tool that processes a workpiece by rotating a tool and reciprocating the tool relative to the workpiece.

Prior Art In machine tools such as drilling machines, the present applicant has developed an air drive device that reciprocates a main shaft cylinder that rotatably supports a main shaft carrying the tool in order to reciprocate the tool relative to a workpiece. An application was previously filed for a device equipped with a feed control device that controls the feed speed of the tool during forward movement to a constant speed by applying a constant load to the main shaft cylinder inside using a hydraulic circuit such as an oil cylinder and a throttle valve.

However, in the hydraulic circuit of the feed control device, if the temperature of the pressure oil rises and the viscosity of the pressure oil decreases, for example due to continuous operation for a long time, even if the throttle amount of the throttle valve is constant. As the viscosity of the pressure oil decreases, the flow rate of the pressure oil increases, and the load applied to the main shaft cylinder decreases.

Therefore, as the temperature of the pressure oil increases, the feed speed of the tool increases, and the time required for one machining cycle gradually becomes shorter as shown in FIG.

However, in machine tools that are equipped with a torque detection device that detects the load torque applied to the tool in order to prevent damage to the tool, the torque detection device usually detects the torque applied to the tool at a predetermined feed rate. Since the load torque is detected, accurate torque detection could not be performed due to the above-mentioned fluctuations in the feed rate.

Purpose This invention was made to solve the above problems, and the purpose is to always keep the tool feed rate constant even if the temperature of the pressure oil changes and the viscosity of the pressure oil fluctuates. To provide a feed control device for a machine tool which is capable of accurately detecting the load torque of a tool.

EXAMPLE Hereinafter, an example in which this invention is embodied in a drilling machine will be described based on the drawings.

In FIG. 2, a drive shaft 2 of a three-phase induction motor (hereinafter referred to as a main shaft motor) 1 is provided with a cylindrical body 3 at its tip.

The main shaft 4 has a drill 6 attached to its distal end via a chuck 5, and a spline shaft 7 fitted to the base end thereof so as to be movable only in the axial direction with the cylindrical body 3. The rotational force of the main shaft motor 1 is transmitted.

The main shaft cylinder 8 supports the main shaft 4 rotatably but immovably in the axial direction, has a piston 9 formed approximately at the center of its outer periphery, and has an engagement lever 10 attached to its base end.

The air cylinder 11 constituting the air drive device has the piston 9 inserted therein, and a first air cylinder chamber 11a and a second air cylinder chamber 11b are provided with the piston 9 as a boundary.

The electromagnetic switching valve 12 is switched and controlled by an electric control circuit to be described later, and when supplying air from the air pump 14 to the first air cylinder chamber 11a via the regulator 13 and discharging air from the second air cylinder chamber 11b, the piston 9, the main shaft cylinder 8 is moved forward, and conversely, when air is supplied from the air pump 14 to the second air cylinder chamber 11b and air from the first air cylinder chamber 11a is discharged, the main shaft cylinder 8 is moved backward.

Therefore, rotational force is applied to the drill 8 by the main shaft motor 1, and reciprocating motion is performed by switching the electromagnetic switching valve 12.

In this embodiment, forward movement is started from the position shown in FIG. 2 (hereinafter referred to as the original position), and when the drill 6 has moved forward to the finishing position of the workpiece, the engagement lever 10 is attached to the machine frame. The microswitch SW1 is turned on, and based on this on signal, a control circuit (to be described later) turns on the electromagnetic switching valve 1.
2 is switched so that it is moved back to the original position.

The oil cylinder 15 has a piston 16 provided with the engagement lever 10 that moves forward together with the main shaft cylinder 8, and a piston rod 17 that engages during the forward movement thereof, and a cylinder chamber filled with pressure oil 18. There is.

The piston 16 is moved forward by the engagement lever 10 when the engagement lever 10 starts moving forward from the original position and moves forward a predetermined distance and engages the piston rod 17.

The pressure oil 18 in the cylinder chamber is sent to an oil tank 20 via a flow rate regulating valve 19.

At this time, since the discharge amount of the pressure oil 18 discharged from the cylinder chamber is constant depending on the throttle amount of the flow rate regulating valve 19, the forward movement speed of the piston 16 is limited.

Therefore, after the main shaft cylinder 8 moves forward together with the main shaft 4 supporting the drill 6 and the engagement lever 10 engages with the piston rod 17, the forward movement of the main shaft cylinder 8 is prevented by the throttling action of the flow rate regulating valve 19. and its speed is set to the optimum speed for drilling holes.

A portion of the air supplied from the air pump 14 to the first air cylinder chamber 11a is supplied to the oil tank 20 via a check valve 21, so that the pressure inside the oil tank 20 is always below a certain value. I'm trying not to let it go down.

On the other hand, a variable throttle valve 22 and a check valve 23 are connected in parallel to the flow rate adjustment valve 19, and the variable throttle valve 22 is provided to finely adjust the flow rate of the pressure oil 18 discharged from the oil cylinder 15. Check valve 23
constitutes a bypass circuit when the pressure oil 18 flows from the oil tank 20 to the oil cylinder 15.

Therefore, the piston 16 of the oil cylinder 15 moves forward based on the engagement between the piston rod 17 and the engagement lever 10,
Flow rate adjustment valve 1 transfers pressure oil 18 in the cylinder chamber to oil tank 20
9.

On the contrary, the engagement lever 10 is connected to the microswitch SW1.
is turned on, the same lever 10 moves back and the piston rod 1
When the engagement with 7 is released, the pressure oil 18 in the oil tank 20 is supplied into the oil cylinder 15 via the check valve 23 because the tank 20 is at high pressure.
The piston 16 is moved back to return to its original state.

A step motor 24 serving as a flow rate regulating valve actuating device is controlled to rotate forward and backward by a predetermined amount by a control circuit described later, and has a pinion 25 attached to its drive shaft.

The rack 26 is engaged with the pinion 25 at one end thereof, and is reciprocated as the pinion 25 rotates.

The pinion 27 engages with the other end of the rack 26 and rotates forward and backward relative to the amount of reciprocating movement of the rack 26.
The amount of throttling of the flow rate regulating valve 19 is adjusted through the flow regulating valve 19.

Next, an electric control circuit for the drilling machine configured as described above will be explained.

In FIG. 3, a load torque detection device 31 is provided near the drive shaft 2 of the main shaft motor 1 as shown in FIG. 2, and is designed to detect the load torque applied to the drill 6. Electrical signal SG with a value proportional to the size
It is designed to output l.

A temperature sensor 32 as a temperature detection device is connected to the oil tank 2.
0, and the temperature of the pressure oil 18 (hereinafter referred to as oil temperature) T
, and outputs a detection signal SG2 having a value proportional to the level of the oil temperature T.

A control circuit 33 serving as a control device is configured to receive an electric signal SGi from the load torque detection device 31, a detection signal SG2 from the temperature sensor 32, and an ON signal from the microswitch SW1, and output the electric signal. S
When the value of Gl reaches a value preset in the control circuit 33, that is, when the load torque applied to the drill 6 reaches the maximum allowable load torque, and when the microswitch SW1 is turned on, that is, when the drill 6 When the drill moves forward to the machining end position, a drive signal SG3 is outputted to the electromagnetic switching valve 12 to cause the main shaft cylinder 8 to move back in order to immediately return the drill 6 to its original position.

Further, when the control circuit 33 inputs the detection signal SG2 from the temperature sensor 32, the control circuit 33 adjusts the flow rate regulating valve 19 according to the value of the detection signal SG2, that is, the oil temperature T, as shown in FIG.
The amount of restriction (hereinafter referred to as opening degree) of A drive control signal SG4 for movement is output.

In addition, in this embodiment, the opening degree of the flow rate regulating valve 19 with respect to the oil temperature T shown in FIG. In this case, the flow rate of the pressure oil 18 is set to a preset value so that the flow rate of the pressure oil 18 is always constant by adjusting the opening degree.

Next, the operation of the drilling machine configured as described above will be explained.

Now, when the flow rate regulating valve 19 is open at a certain predetermined oil temperature T and at an opening relative to the oil temperature T, the pressure oil 18
is discharged into the oil tank 20 at a constant rate via the flow rate adjustment valve 19 due to the forward movement of the piston 16, so that the main shaft cylinder 8, that is, the drill 6, moves forward toward the machining end position at the optimum feed rate. When machining work is being performed in a state where the oil temperature T increases, the viscosity of the pressure oil 18 decreases, and the discharge amount of the pressure oil 18 increases.

At this time, the control circuit 33 determines the opening degree of the flow rate regulating valve 19 with respect to the increased oil temperature T based on the detection signal SG2 output from the temperature sensor 32, and controls the step motor 24 to a predetermined value so that the opening degree is reached. A drive control signal SG4 is output to the motor 24 to cause the rotation in the reverse direction (in this case, forward rotation).

When the step motor 24 is rotated up and down a predetermined amount, the opening degree of the flow rate regulating valve 19 is reduced by a predetermined amount.

The discharge amount of the pressure oil 18 discharged into the oil tank 20 via the flow rate adjustment valve 19 is determined based on the increase in the oil temperature T.
The feed rate of the drill 6 is always maintained at the optimum speed even if the viscosity decreases.

In this way, in this embodiment, even if the temperature T of the pressure oil 18 changes during machining work and its viscosity fluctuates, the amount of pressure oil 18 discharged into the oil tank 20 via the flow rate adjustment valve 19 remains unchanged. Since the opening degree of the flow rate regulating valve 19 is automatically adjusted in response to changes in the temperature T of the pressure oil 18 so that the feed rate is always constant, the drill 6 always maintains a constant optimum feed rate.

Therefore, the load torque detection device 31 can accurately detect the load torque of the drill 6.

In addition, in the above embodiment, the temperature T of the pressure oil 18 is
Although the temperature of the pressure oil inside the oil cylinder 15 is detected, for example, the temperature of the pressure oil 18 inside the oil cylinder 15 or the pressure oil 18 flowing between the oil cylinder 15 and the oil tank 20 may be detected.

Further, in the above embodiments, the present invention was applied to a drilling machine, but it is also possible to apply the invention to a machine tool in which a tool moves back and forth, such as a broaching machine.

Furthermore, in the embodiment, the amount of rotation of the step motor 24 is controlled by the flow regulating valve 1 through the pinions 25, 27, the rack 26, etc.
9, the amount of rotation of the step motor 24 may be directly transmitted to the flow rate regulating valve 19.

Effects As detailed above, according to this invention, even if the temperature of the pressure oil flowing through the flow adjustment valve that controls the forward speed of the main shaft cylinder changes and its viscosity fluctuates, the pressure flowing through the flow adjustment valve The opening degree of the regulating valve is automatically adjusted in response to changes in the pressure oil temperature so that the oil flow rate can be varied according to the fluctuations in the viscosity. The feed rate of the tool does not fluctuate, and the load torque of the tool can be detected accurately.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the time required for one machining process with a machine tool relative to the temperature of pressure oil, Figure 2 is a mechanical diagram showing the mechanism of a drilling machine that embodies this invention, Figure 3 is an electrical block circuit diagram,
FIG. 4 is a diagram showing the opening degree of the flow rate regulating valve with respect to the temperature of pressure oil.

Claims (1)

[Claims for Utility Model Registration] 1. An air drive device (11, 12, etc.) for reciprocating the main spindle cylinder 8 that rotatably supports the main spindle 4 with respect to the workpiece, and a reciprocal movement of the main spindle cylinder 8. On the way, an oil cylinder 15 that can engage with a part of the main shaft cylinder 8 adjusts the amount of oil discharged from the oil cylinder 15 into the oil tank 20 as the main shaft cylinder 8 engages. a temperature detection device disposed in either the oil tank 20 or the oil cylinder 15 to generate a detection signal SG2 according to the temperature of the oil 18; 32, and an adjustment device (24, 33, etc.) for adjusting the discharge amount of the flow rate adjustment valve 19 according to the magnitude of the detection signal SG2 of the oil temperature detection device 32. 2 The adjustment device includes a flow rate adjustment valve operating device 24 for controlling the adjustment valve 19 to change the discharge amount, and a flow rate adjustment valve actuation device 24 for controlling the adjustment valve 19 to change the discharge amount, and a flow rate adjustment valve actuating device 24 for controlling the adjustment valve 19 to change the discharge amount, and a flow rate adjustment valve actuation device 24 for controlling the adjustment valve 19 to change the discharge amount, and The feed control device for a machine tool according to claim 1, characterized in that it comprises a control device 33 for controlling the actuating device 24.