JPS6218315B2 - - Google Patents

Description

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

The purpose of the present invention is to ventilate the air inside the grinding wheel guard and to prevent the grinding sparks generated during grinding by the coolant nozzle installed just before the grinding wheel enters the grinding wheel guard, and This prevents the high temperature air traveling along the grinding wheel from being sucked into the grinding wheel guard, thereby preventing changes in the atmospheric temperature inside the grinding wheel guard, thereby keeping the thermal expansion of the grinding wheel stable over a long period of time. , to improve the dimensional accuracy of the workpiece.

Generally, a CBN grinding wheel or a diamond grinding wheel (hereinafter simply referred to as a CBN grinding wheel) has a layer of hard abrasive grains made of cubic boron nitride on the outer peripheral surface of a base disc made of aluminum or cast material.
It is composed of degrees of formation. 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, as the workpiece is continuously ground, the thermal expansion of the grinding wheel gradually progresses, resulting in CBN
Since the grinding wheel has little wear due to grinding, the machining dimensions of the workpiece gradually tend to decrease. The main reason for this is that grinding sparks generated during grinding or heated air that circulates around the outer circumferential surface of the grinding wheel flow into the grinding wheel guard as the grinding wheel rotates, and as a result, the zero ambient temperature inside the grinding wheel guard gradually decreases. Experiments conducted by the present inventors have confirmed that this is due to the increase in temperature.

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 6th workpiece grinding, the temperature inside the guard increased by △T°,
As this temperature rises, the thermal expansion of the grinding wheel increases,
The workpiece is ground in a negative direction.

The present invention was made to solve these conventional problems, and it ventilates the air inside the grinding wheel guard and improves grinding speed by using a coolant nozzle installed just before the grinding wheel enters the grinding wheel guard. This prevents the inflow of sparks, thereby preventing temperature changes within the grinding wheel guard and stabilizing the thermal expansion of the grinding wheel.

Embodiments of the present invention will be described below based on the drawings. In FIG. 2, reference numeral 10 indicates the bed of the grinding machine. A grindstone head 12 is movably placed on this bed 10, and a whetstone shaft 13, which is belt-connected to a drive motor (not shown), rotates on this grindstone head 12. Bearing possible. At one end of the grinding wheel shaft 13, hard abrasive grains made of cubic boron nitride are fixed in a layer to the outer peripheral surface of a base disc 14 made of aluminum or cast metal.
A CBN grinding wheel 15 is attached, and this grinding wheel 15 is driven to rotate in the direction of the arrow by the drive motor. A whetstone guard 16 is fixed to the side surface of the whetstone head 12 and covers the whetstone wheel 15 with the part that contacts the workpiece W exposed.
A coolant nozzle 18 is installed above the pump 17 to supply the coolant sucked up by the pump 17 to the grinding point P, and a pump 17 is installed at a position immediately before the grinding wheel 15 enters the grinding wheel guard 16. A coolant nozzle 19 is attached that spouts the coolant sucked up by the grinding wheel 15 toward the outer peripheral surface of the grinding wheel 15. In addition, a suction port 20 is formed at the rear upper part of the grindstone guard 16, and this suction port 2
0 is connected to a suction pump 22 via a suction pipe 2.

In this configuration, the grindstone head 12 is advanced toward the workpiece W in the order of rapid feed and grinding feed by an unillustrated feeding device, and grinding is performed. During grinding, the air inside the grinding wheel guard 16 is affected by grinding heat, etc., but this air is constantly discharged to the outside of the grinding wheel guard 16 by the suction pump 22, and air in the atmosphere with less temperature change is used instead. The air flows through the upper opening 23 and the lower opening 24, and as a result, the ambient temperature inside the grinding wheel guard 16 is maintained at approximately the same temperature as the atmosphere, and thermal expansion of the grinding wheel 15 due to temperature changes is prevented.

On the other hand, grinding sparks generated during grinding due to the rotation of the grinding wheel 15 and the above-mentioned suction action, as well as high-temperature air floating in the vicinity of the grinding area, try to enter the grinding wheel guard 16 through the lower opening 24. Since a coolant nozzle 19 that injects coolant toward the outer peripheral surface of the grinding wheel is provided below, grinding sparks and high-temperature air are prevented from flowing in, and temperature changes within the grinding wheel guard 16 can be prevented. It's summery.

Incidentally, according to the present invention, the temperature inside the grinding wheel guard 16 only temporarily increases by a certain amount due to the grinding heat generated by grinding the workpiece W, as shown in the diagram in FIG. 3, and increases as the grinding process progresses. As a result, the thermal expansion of the grinding wheel 15 can be maintained stably over a long period of time, and the dimensional accuracy of the workpiece W caused by the thermal expansion of the grinding wheel 15 can be made uniform as shown in FIG. can be maintained.

The air inside the grinding wheel guard is sucked and released into the atmosphere to ventilate the air inside the grinding wheel guard, and at the same time, the air inside the grinding wheel guard is ventilated by the action of coolant jetted toward the outer peripheral surface of the grinding wheel from a coolant nozzle installed below the grinding point. Since it is designed to prevent grinding sparks and high-temperature air from flowing into the grinding wheel guard, it can be configured simply by adding an air suction means and a coolant nozzle to prevent the inside of the grinding wheel guard from flowing into the grinding wheel guard due to changes in the grinding process. Temperature changes can be prevented, and the dimensional accuracy of the workpiece can be maintained with uniformity and high precision.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the number of grinding wheels and the temperature inside the whetstone guard in the conventional method, Fig. 2 is a vertical sectional view of main parts showing an embodiment of the present invention, and Fig. 3 is a diagram showing the relationship between the number of grinding wheels and the whetstone guard in the present invention. FIG. 4 is a diagram showing the relationship between the internal temperature and the relationship between the number of grinding pieces and the dimensional change of the workpiece in the present invention. 10... Bed, 12... Grinding wheel head, 15... Grinding wheel, 16... Grinding wheel guard, 17... Coolant pump, 18, 19... Coolant nozzle, 20
...Suction port, 21...Suction pipe, 22...Suction pump.

Claims (1)

[Claims] 1 A grindstone stand movably placed on the bed,
A grinding wheel is rotatably supported on this grinding wheel head and has hard abrasive grains made of cubic boron nitride fixed in a layer on the outer circumferential surface of a metal disk, and the grinding wheel is exposed at the part that contacts the workpiece. A grinding wheel guard that covers the grinding wheel, a ventilation device that sucks air inside the grinding wheel guard and exhausts it to the outside through a suction port formed in the grinding wheel guard, and a ventilation device that is located above the grinding point and directed to the grinding point. A first coolant nozzle that supplies coolant, and a second coolant nozzle that is located below the grinding point and injects coolant toward the outer peripheral surface of the grinding wheel at a position immediately before the grinding wheel enters the grinding wheel guard. A thermal displacement prevention device for a grinding machine characterized by the following configuration.