JPS6224232B2 - - 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 the grinding process, under constant conditions relative to room temperature, thereby keeping the thermal expansion of the grinding wheel at a constant ratio for each part of the grinding machine, and by controlling the temperature inside the grinding wheel guard, which increases as the grinding process progresses. The objective is to improve the dimensional accuracy of the

In general, a CBN grinding wheel is constructed by forming a layer of hard abrasive grains made 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 transferred to the metal disc of the grinding wheel, causing thermal expansion of the grinding wheel, which has a non-negligible effect on the dimensional accuracy of the workpiece. The main reason for this is that the temperature inside the grinding wheel guard gradually rises as the grinding process progresses, increasing the thermal expansion of the grinding wheel. That is, when measuring the temperature inside the grinding wheel guard during continuous grinding, the temperature inside the grinding wheel guard gradually increases as the number of grinding wheels (time) increases, as shown in the diagram in Figure 1. Between the grinding of the first workpiece and the sixth workpiece, the temperature inside the guard increases by △T°, and as this temperature rises, the thermal expansion of the grinding wheel also increases, resulting in a situation where the workpiece dimensions tend to be negative. invite.

The present invention has been made in view of the above-mentioned conventional problems, and is designed to manage the thermal expansion of the grinding wheel by controlling the internal temperature of the grinding wheel guard under a constant condition relative to room temperature.

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 this bed, and a workpiece W is supported on this table 11.
and a headstock and tailstock 12 (not shown) that are rotationally driven.
is installed. There is a whetstone head 1 on the front bed 10.
3 is placed so as to be movable forward and backward in a direction intersecting the sliding direction of the table 11, and a grindstone shaft 14, which is connected by a belt to a rotary drive motor (not shown), is rotatably supported on this grindstone head 13. A CBN grinding wheel 16 is attached to one end of the grinding wheel shaft 14, and the CBN grinding wheel 16 has hard abrasive grains made of cubic boron nitride fixed to the outer peripheral surface of a base disk 15 made of aluminum or cast metal in a layered manner. It is designed to be rotated in the direction of the arrow by a drive motor. Whetstone stand 13
A grindstone guard 17 that covers the grindstone wheel 16 is fixed to the side surface of the grinding wheel 16, and a coolant nozzle 18 for supplying coolant to the grinding point is attached to the front surface of the grindstone guard 17.

A first 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 first temperature sensor 20 is disposed 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. Further, a second temperature sensor 21 is provided to measure the temperature in the room where the grinding machine is installed, and the second temperature sensor 21 outputs an output voltage depending on the room temperature. The output of the first temperature sensor 20 is applied to an amplifier 22 for output amplification, and a comparator 23
is applied to one input terminal of Further, the output of the second temperature sensor 21 is applied to an amplifier 24 to amplify the output, and this amplified output is applied to a multiplier 25 where it is multiplied by a certain constant n and is applied to the other input terminal of the comparator 23. . Comparator 23 compares the two outputs and outputs control signal S1 if they match. That is, the comparator 23 outputs the control signal S1 when the temperature T2 inside the grindstone guard 17 reaches a certain ratio (nT1) with respect to the room temperature T1.

Further, the grindstone guard 17 is equipped with a cooling device that controls the temperature inside the guard 17 to be cooled to room temperature. This cooling device includes an air nozzle 27 opened toward the inner part of the grindstone guard 17, a pressurized air supply source 29 connected to the air nozzle 27 via an air pipe 28, and a pressurized air supply source 29 provided in the air pipe 28. The control valve 30 is comprised of a control valve 30 that is
The control valve 30 receives a retreat signal S for the grindstone head 13.
2, the communication path is opened to connect the pressurized air supply source 29 and the air nozzle 27,
It is also operated based on the control signal S1 of the comparator 23 to close the communication path and cut off communication between the pressurized air supply source 29 and the air nozzle 27.

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 driven to rotate, the grindstone head 13 is advanced in rapid traverse, and just before the grinding wheel 16 collides with the workpiece W, it is retarded. is converted to Thereafter, the workpiece W is traverse-ground by the grinding wheel 16 by the traverse movement of the table 11 and the intermittent cutting operations of the grindstone head 13. Coolant is constantly supplied to the grinding point by a 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 30 is switched based on the retreat signal S2, and pressurized air is supplied from the pressurized air supply source 29 to the air nozzle 27,
It is ejected into the grindstone guard 17. As a result, the machining heat trapped inside the grinding wheel guard 17 due to the grinding process is discharged to the outside of the grinding wheel guard 17 together with air.
The inside of the guard 17 is cooled. When the temperature T1 inside the guard 17 is cooled to a certain ratio (nT2) to the room temperature T2, the comparator 23 outputs the control signal S1. Based on this control signal S1, the control valve 30 is switched to its original position, and the ejection of pressurized air from the air nozzle 27 is stopped. Such a cooling effect inside the grinding wheel guard 17 by air is performed during non-grinding, and the temperature inside the guard 17, which has increased due to processing heat during processing, always maintains a constant relationship with the room temperature every time the grinding process is completed. is maintained.
Therefore, as shown in the diagram in FIG. 3, the temperature inside the grindstone guard 17 does not rise during the grinding process.
The thermal expansion of the grinding wheel 16 can be maintained in a constant relationship with the thermal expansion of each part of the grinding machine including the workpiece W, and the dimensional accuracy of the workpiece W can be improved.

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

Furthermore, in the above embodiment, the temperature inside the grinding wheel guard 17 was controlled to a constant ratio with respect to the room temperature, but it is also effective to control the temperature inside the grinding wheel guard 17 to a constant temperature difference with respect to the room temperature. It is true.

As described above, in the present invention, the temperature inside the grinding wheel guard is controlled under constant conditions relative to room temperature every time the grinding process is completed, so that the temperature inside the grinding wheel guard increases as the grinding process progresses. This solves the problem of the gradual increase in the thermal expansion of the grinding wheel, and also maintains the thermal expansion in a constant relationship with the thermal expansion of each part of the grinding machine, including the workpiece, making it possible to machine the workpiece dimensions uniformly and with high precision. There are characteristics that can be ensured.

[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 in a grinding machine showing an embodiment of the present invention, and FIG.
The figure is a diagram showing the relationship between the number of grinding wheels and the temperature inside the grindstone guard in the present invention. 10... bed, 11... table, 13...
Grinding wheel head, 16... Grinding wheel, 17... Grinding wheel guard,
20, 21... Temperature sensor, 23... Comparator, 2
7... Air nozzle, 29... Pressurized air supply source, 3
0...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; The temperature control device is equipped with a temperature control device that cools and controls the temperature inside the grindstone guard under constant conditions relative to room temperature every time the grinding process is completed, and this temperature control device includes a first temperature sensor that detects the temperature inside the grindstone guard. A control device for a grinding machine comprising: a second temperature sensor that detects room temperature; and a cooling device that cools the inside of the grindstone guard so as to maintain the internal temperature of the grindstone guard in a constant relationship with the room temperature. 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. A control valve 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 first temperature sensor to cut off communication between the fluid supply device and the fluid nozzle. A control device for a grinding machine according to scope 1.