JPS6218314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a grinding machine equipped with a CBN grinding wheel in which hard abrasive grains made of cubic boron nitride are fixed to the outer peripheral surface of a metal disk in a layered manner.

The purpose of the present invention is to control the temperature inside the grinding wheel guard, which increases during grinding, to a constant level, thereby keeping the thermal expansion of the grinding wheel stable over a long period of time, and improving the dimensional accuracy of the workpiece. .

A CBN grinding wheel is constructed by forming a hard abrasive grain layer of several millimeters of cubic boron nitride on the outer circumferential surface of a base disc made of aluminum or cast material. A grinding machine equipped with such a CBN grinding wheel has the advantage that the abrasive grains of the grinding wheel are hard and cause almost no wear, so that sufficient dimensional accuracy of the workpiece can be ensured even in so-called dead stop grinding.

By the way, when a workpiece is ground using a CBN grinding wheel, processing heat is transmitted to the metal disc of the grinding wheel, causing thermal expansion of the grinding wheel. The processing heat temperature transmitted to this grinding wheel increases rapidly as the grinding process begins.
Upon completion of the grinding process, the temperature rapidly decreases and returns to the original temperature. If the thermal expansion of the grinding wheel due to this processing heat is always constant, the dimensional accuracy of the workpiece being ground by the grinding wheel will also be maintained almost uniformly.
Does not cause any major problems.

However, when the workpiece is continuously ground, the thermal expansion of the grinding wheel gradually progresses, leading to a situation where the machined dimensions of the workpiece gradually become negative. The inventors' experiments have confirmed that the main reason for this is that the temperature inside the grindstone guard gradually increases as the grinding process progresses. In other words, when measuring the temperature inside the grinding wheel guard during continuous grinding, the temperature inside the grinding wheel guard gradually increases as shown in the diagram in Figure 1. Comparing with the sixth workpiece grinding, the temperature inside the guard increases by ΔT°, and as this temperature rises, the thermal expansion of the grinding wheel increases, causing the workpiece to be ground in a negative direction.

The present invention has been made in view of the above-mentioned conventional problems, and is designed to stabilize the thermal expansion of the grinding wheel by controlling the internal temperature of the grinding wheel guard to be constant.

Embodiments of the present invention will be described below based on the drawings.
In Fig. 2, 10 indicates the bed of the grinding machine,
A table 11 is slidably placed on the bed 10, and a headstock and a tailstock 12 (not shown) that support the workpiece W and rotate it are installed on the table 11. A whetstone head 13 is placed on the bed 10 so as to be movable in a direction intersecting the sliding direction of the table 11, and a whetstone shaft 14 is connected to the whetstone head 13 by a belt to a rotary drive motor (not shown).
is rotatably supported. At one end of the grinding wheel shaft 14 is a base disc 1 made of aluminum or cast metal.
A CBN grinding wheel 16 on which hard abrasive grains made of cubic boron nitride are fixed in layers is attached to the outer peripheral surface of the grinding wheel 5, and this grinding wheel 16 is driven to rotate in the direction of the arrow by the rotary drive motor. . A grindstone guard 17 that covers the grindstone wheel 16 is fixed to the side surface of the grindstone head 13, and a coolant nozzle 18 for supplying coolant to the grinding point is attached to the front surface of the grindstone guard 17.

Further, a temperature sensor 20 such as a thermocouple thermometer is attached to the whetstone guard 17 so as to face the inside of the whetstone guard 17 . This temperature sensor 20 is connected to the grinding wheel guard 1.
It is arranged at the rear of the whetstone guard 17 so as to measure the average temperature inside the whetstone guard 17, and outputs an output voltage according to the temperature inside the whetstone guard 17. Temperature sensor 20
The output of is added to the amplifier 21 for output amplification,
It is added to the signal generation circuit 22. This signal generating circuit 22 is adapted to output a control signal S1 in response to a predetermined voltage level, and a control valve to be described later is switched based on this control signal S1.

Further, a cooling air nozzle 23 is attached to the grindstone guard 17 toward the inner part of the grindstone guard 17, and this air nozzle 23 is connected to a pressurized air supply source 25 via an air pipe 24. A control valve 26 is provided in the air pipe line 24, and this control valve 2
6 opens the communication path based on the retraction signal S2 of the grindstone head 13 to connect the pressurized air supply source 25 and the air nozzle 23, and also opens the communication path based on the control signal S1 of the signal generation circuit 22. By closing, communication between the pressurized air supply source 25 and the air nozzle 23 is cut off.

Since the present invention is configured as described above,
When the workpiece W is supported between the headstock (not shown) and the tailstock 12 and rotated, the grinding wheel head 13 is advanced in rapid traverse, and just before the grinding wheel 16 collides with the workpiece W, it is in slow traverse. The workpiece W is plunge-cut grounded by the grinding wheel 16. Coolant is constantly supplied to the grinding point from the coolant nozzle 18.

When the grinding wheel head 13 is advanced to the dead stop position and the workpiece W is ground to a predetermined size, a grinding wheel head retreat signal S2 is output, and the grinding wheel head 13
is retreated to its original position. The control valve 26 is switched based on the retreat signal S2, and pressurized air is supplied from the pressurized air supply source 25 to the air nozzle and is ejected into the grindstone guard 17. As a result, the machining heat accumulated in the grindstone guard 17 due to the grinding process is discharged to the outside of the grindstone guard 17 along with air, and the inside of the guard 17 is cooled. When the inside of the guard 17 is cooled to a certain temperature, the signal generator 22 is activated based on the output from the temperature sensor 20, and the control signal S is activated.
Outputs 1. Based on this control signal S1, the control valve 26 is switched to its original position, and the air nozzle 23
Pressurized air is stopped from blowing out. Such a cooling effect inside the grindstone guard 17 by air is performed during non-grinding, and the inside of the guard 17, whose temperature has increased due to processing heat during the grinding process, is cooled to a constant temperature every time the grinding process is completed.

Therefore, as shown in the diagram in FIG. 3, the temperature inside the grindstone guard 17 only temporarily rises by a certain amount due to the processing heat generated by grinding the workpiece W, and does not rise as the grinding process progresses. As a result, the thermal expansion of the grinding wheel 16 can be stably maintained over a long period of time, and the workpiece W due to the thermal expansion of the grinding wheel 16 can be maintained stably for a long period of time.
It becomes possible to maintain uniform dimensional accuracy.

In the above embodiment, air is used to cool the inside of the grindstone guard 17, but a coolant may also be used.

As described above, in the present invention, the temperature inside the grinding wheel guard is controlled to be constant and the thermal expansion of the grinding wheel is always maintained stably, so that the temperature inside the grinding wheel guard gradually increases as the grinding process progresses. This feature eliminates the problem of increased thermal expansion of the grinding wheel, and maintains uniform dimensional accuracy of the workpiece over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the number of grinding wheels and the temperature inside the grinding wheel guard in the conventional method, Fig. 2 is a schematic diagram of a control device for a grinding machine showing an embodiment of the present invention, and Fig. 3 is a diagram showing the number of grinding wheels in the present invention. FIG. 3 is a diagram showing the relationship between the temperature and the temperature inside the grindstone guard. 10... bed, 11... table, 13...
Grinding wheel head, 16... Grinding wheel, 17... Grinding wheel guard,
20...Temperature sensor, 23...Air nozzle, 25
... Pressurized air supply source, 26 ... Control valve, W ... Workpiece.

Claims (1)

[Scope of Claims] 1. A grindstone stand placed movably on a bed,
a grinding wheel rotatably supported on the grinding wheel head and having hard abrasive grains made of cubic boron nitride fixed to the outer peripheral surface of a metal disk in a layered manner; a grinding wheel guard fixed to the grinding wheel head and covering the grinding wheel; This temperature control device is equipped with a temperature control device that controls cooling of the inside of the grinding wheel guard to a constant temperature every time the grinding process is completed.
A control device for a grinding machine comprising a temperature sensor that detects the temperature inside the grindstone guard and a cooling device that cools the inside of the grindstone guard so that the temperature inside the grindstone guard detected by the temperature sensor is constant. 2. The cooling device includes a cooling fluid nozzle opened in the grinding wheel guard, a fluid supply device that supplies cooling fluid to the fluid nozzle, and a non-contact fluid passage provided in a fluid passage connecting the fluid supply device and the fluid nozzle. Claim 1, comprising a control valve that is operated to open during grinding to communicate the fluid supply device and the fluid nozzle, and is operated to close based on the output of the temperature sensor to cut off communication between the fluid supply device and the fluid nozzle. A control device for a grinding machine as described in .