JPH03184735A - Magnetic chuck device of grinder - Google Patents

Abstract

PURPOSE:To obtain the magnetic chuck device for a grinder whose displacement in the axial direction of a work attraction face accompanied by the temperature variation is extremely less, by making the chuck shaft center composed of the inner alloy of a low thermal expansion excellent in a magnetic characteristic. CONSTITUTION:Each machine part including a magnetic chuck device 1 is heated by the actuation of a grinder and a chuck shaft center 3 also rises in temperature mainly by current-flow. Owing to the shaft center 3 being composed of an inner alloy, however, the thermal expansion thereof is extremely less and the increase in the distance dimension L in the axial direction from the displacement in the axial direction of a work attraction face 5a, i.e., the center X in the axial direction of bearings 9, 9 up to the work attraction face 5a, is extremely less. The axial directional position of the work W supported by being attracted to the attraction face 5a receives no adverse effect by the thermal expansion in the axial direction of each machine part especially of the chuck shaft center 3. So a highly accurate grinding is executed, a finishing width dimension l in the axial direction with high accuracy is obtained, the stock removal is stabilized at all times as well and the reduction in the service life of a grinding wheel is also restrained.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an electromagnetic chuck device that is attached to the main shaft of a grinding machine, and more specifically, the invention relates to an electromagnetic chuck device that is attached to the main shaft of a grinding machine, and more specifically, the axial displacement of the workpiece suction surface due to temperature changes is small. The present invention relates to the structure of an electromagnetic chuck device.

(Prior Art) An electromagnetic chuck device is used to securely support a workpiece using magnetic attraction force. It is also used in grinding machines as it is an ideal device for simplifying workpiece attachment and removal work and saves labor because it can be controlled and the attachment and detachment of workpieces can be done efficiently with the operation of a switch.

In an electromagnetic chuck device used in a grinding machine, a chuck shaft core, which has an electromagnetic coil wound around the tip of the main shaft, is attached concentrically to the main shaft, and The structure is such that a magnetic workpiece is magnetically attracted and supported on the workpiece attraction surface.

(Problems to be Solved by Invention) However, grinding machines using conventional electromagnetic chuck devices have the following problems, and improvements have been desired.

(1) The heat generated in each part of the machine after the grinder starts increases the axial displacement of the workpiece suction surface, that is, the axial distance from the main shaft bearing (reference position) to the workpiece suction surface. , the axial position of the workpiece suctioned and supported by the workpiece suction surface changes.

Therefore, until the dimensional change in the distance dimension due to thermal displacement disappears and the distance dimension becomes stable, there will be considerable variation in the axial finished width dimension of the workpiece to be machined.

Therefore, apart from the case where the amount of change in the distance dimension is within the allowable range of the axial finished width dimension of the workpiece, processing of a workpiece that has a narrow tolerance range of the finished width dimension and requires high machining accuracy. In this case, machining work cannot be started until the above-mentioned distance dimension is stabilized, and it is also necessary to correct the machining dimension from the time the machine is started until the above-mentioned distance dimension is stabilized. (needs to be corrected), which caused a significant drop in machining efficiency.

Moreover, in recent years, in order to obtain high-quality products, higher precision has been required for the finished dimensions of products, and this combined with the above-mentioned decrease in processing efficiency, in the worst case, electromagnetic chuck equipment There are also situations where it becomes impossible to use the device itself.

(2) Furthermore, as the axial processing position of the workpiece changes, the grinding allowance also changes, which reduces the life of the grinding wheel and increases the number of times that dressing is required.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an electromagnetic chuck device for a grinding machine in which axial displacement of a workpiece suction surface due to temperature changes is extremely small.

(Means for Solving the Problems) In order to solve the above problems, the present inventors conducted various tests and research, and found that the main cause of the problems is largely dependent on the structure of the electromagnetic chuck device. We identified this problem and realized its improvement.

In other words, in conventional electromagnetic chuck devices, an iron core is used as the chuck axis, but thermal expansion of the iron core (mainly caused by temperature rise of the iron core due to energization of the electromagnetic coil) It was found that by minimizing this thermal expansion, it was possible to reduce the variation in the finished width dimension of the workpiece in the axial direction, and to develop its structure. succeeded in.

Therefore, in order to achieve the above object distantly, the electromagnetic chuck device of the present invention is characterized in that the chuck axis is made of a low thermal expansion alloy having excellent magnetic properties, and more preferably,
Invar alloy is used.

(Function) The chuck axis of the electromagnetic chuck device is made of a low thermal expansion alloy with excellent magnetic properties, such as invar alloy, which prevents the axial displacement of the workpiece suction surface due to temperature changes, that is, the main axis of the grinding machine. An increase in the axial distance from the bearing to the workpiece suction surface is suppressed.

(Example> Embodiments of the present invention will be described below with reference to the drawings.

An electromagnetic chuck device for a grinding machine according to the present invention is shown in FIG. 4 and a backing plate 5 as main parts.

7 is a shoe that rotatably supports the outer periphery of the workpiece (bearing inner ring) W.

The main shaft 2 is rotatably supported by a headstock 8 via bearings 9, 9, and is rotationally driven by a drive source (not shown). Reference numeral 10 denotes a bearing holder, which is mounted and fixed to the headstock 8 with mounting bolts 14 .

The chuck shaft core 3 is a cylindrical member made of a low thermal expansion alloy with excellent magnetic properties, and specifically made of an Invar alloy (thermal expansion coefficient: 1 x 104 to 3 x 10''s/°C). The chuck shaft core 3 has its centering recess 3a fitted into the centering protrusion 2a at the tip of the main shaft 2, and is fixed to the main shaft 2 by the mounting port 11... The chuck shaft core 3 is rotationally driven integrally with the main shaft 2.

The electromagnetic coil 4 is wound around the outer periphery of the chunk shaft core 3, and is disposed within the yoke portion 12, and is connected to a power source (not shown) via wiring such as a lead wire. Further, the yoke portion 12 is connected to the bearing retainer 1.
0, and is fixedly attached by mounting ports 1-13...

C. The king plate 5 is cup-shaped and made of a magnetic metal material with excellent wear resistance, and its tip surface 5a is a workpiece attraction surface 5a that attracts and supports the workpiece W.
The illustrated example has an annular suction surface corresponding to the workpiece W. The backing plate 5 is removably attached to the distal end surface 3b of the chuck shaft core 3 with attachment bolts 6.

In a grinding machine equipped with the electromagnetic chuck device 1 configured as described above, when the electromagnetic coil 4 of the electromagnetic chuck device 1 is energized, the backing plate 5 is moved through the chuck axis 3. Excited. As a result, the workpiece W has one end surface in the axial direction suctioned and supported by the workpiece suction surface 5a, and its outer diameter surface is slidably supported by the shoes 7 and centered. While the workpiece W is being rotated by the rotational drive of the main shaft 2, its outer circumferential surface (
The raceway surface) and the axial end surface Wa are ground by a grinding wheel (not shown). When the grinding of the workpiece W is completed, the magnetism of the workpiece attraction surface 5a is reversed by switch operation, and the workpiece W is removed from the workpiece attraction surface 5a and demagnetized as necessary. Processing is performed.

By the way, when the grinding machine is started, each part of the machine including the electromagnetic chuck device 1 generates heat, and the chuck axis 3 also generates heat.
The temperature rises mainly due to the above-mentioned energization. However, since the chuck shaft core 3 is made of an invar alloy, the amount of thermal expansion thereof is extremely small.
9 from the axial center X (reference position) to the workpiece suction surface 5
The crucible addition in the axial distance to a is extremely small.

Therefore, the axial position of the workpiece W suction-supported by the workpiece suction surface 5a is not adversely affected by the axial thermal expansion of each part of the machine, especially the chuck shaft core 3. Therefore, a highly accurate grinding process is performed, and a highly accurate finished axial width dimension l is obtained, and the grinding stock is always stable, and a decrease in the life of the grinding wheel is also suppressed.

Next, in order to investigate the temperature characteristics of the bearing chuck device according to the present invention, the results of a characteristic test performed in comparison with a conventional bearing chuck device will be explained.

Test device and test method: In the grinding machine shown in FIG. 1, an invar alloy core (thermal expansion coefficient: 1
~3 x 10'/"C) (device of the present invention), and when using an iron core (low carbon steel of about JIS standard 515C, coefficient of thermal expansion: 11 - 12 x 10 (7°C))
Regarding the conventional device), the amount of displacement λ of the axial distance L (see FIG. 1) due to the temperature change of each part of the machine after the grinder was started was measured.

The axial dimension of the electromagnetic chuck device 1 is Li2, and all other components including the backing plate 5 are made of the same material and have the same structure in both the conventional device and the device of the present invention.

Test results: The test results are shown in Figure 2, and as is clear from this figure,
The above-mentioned axial distance dimension becomes stable in about 2 hours after starting the grinding machine, and the displacement amount λ1 of the dimension in the device of the present invention is 13.5 μm, which is 25 μm of the displacement amount λ2 of the conventional device.
It was found that it was only about 1/2 (54%) compared to m.

Furthermore, from this test result, in both cases, when the energizing voltage to the electromagnetic coil 4, which is the main cause of the temperature rise of the chuck shaft core 3, is set so that the above displacement amount λ is the same amount, the device of the present invention is better. It is possible to obtain strong adsorption force (magnetic force). In other words, the device of the present invention and the conventional device have the minimum adsorption force that can withstand the same grinding force at the displacement λ1. In this case, if an attempt is made to suppress the displacement amount λ2 of the conventional device to λ1, the conventional device will not be able to obtain the necessary adsorption force.

The present invention is applicable not only to the shoe type grinder shown in the drawings (the main shaft 2 is in a horizontal state) but also to other grinding machines such as a surface grinder (the main shaft 2 is in a vertical state).

(Effects of the Invention) As detailed above, according to the present invention, the chuck shaft core, which is most likely to affect the axial displacement of the workpiece suction surface due to temperature changes, is made of a low thermal expansion alloy with excellent magnetic properties. Therefore, it is possible to provide an electromagnetic chuck device for a grinding machine that can exhibit excellent effects as listed below.

(1) Even if heat is generated in each part of the machine after the grinder starts, the amount of axial displacement of the workpiece suction surface, that is, the amount of increase in the distance from the main shaft bearing (reference position) to the workpiece suction surface is extremely small. The axial position of the workpiece suctioned and supported by the workpiece suction surface hardly changes, and the finished width dimension of the workpiece in the axial direction becomes uniform without variation.

Therefore, the amount of change in the above-mentioned distance dimension can always be kept within the permissible range even when machining a workpiece that has a narrow tolerance range for the finished width dimension and requires high machining accuracy. The work of correcting machining dimensions from the start of the grinding machine until the distance dimension is stabilized is also unnecessary or reduced, and machining efficiency can be greatly improved.

(2) Furthermore, the high and strict finishing tolerances required for modern products can be easily satisfied, and the range of its applicability is greatly expanded.

(3) Since the axial machining position of the workpiece does not change, the grinding stock can remain constant at all times, which greatly extends the life of the grinding wheel and significantly reduces the number of times dressing is required. can be reduced to

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view showing an electromagnetic chuck device for a shoe type grinder according to an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the amount of displacement in the axial distance dimension of the same electromagnetic chuck device due to a temperature change after the grinding machine is started, in comparison with that of a conventional electromagnetic chuck device. ■...Electromagnetic chuck device, 2...Main shaft, 3...Chuck shaft center, 4...Electromagnetic coil, 5...Backing plate, 5a...Workpiece suction surface, W...Workpiece thing,
L...Axial distance dimension

Claims (3)

[Claims] (1) A chuck shaft, which has an electromagnetic coil wound around it, is attached to the tip of the main shaft of the grinding machine so as to be concentric with the main shaft, and the workpiece is magnetically attached to the tip of the chuck shaft. 1. An electromagnetic chuck device for a grinding machine, which is provided with a suction surface for visually suctioning and supporting a workpiece, and wherein the chuck axis is made of a low thermal expansion alloy having excellent magnetic properties. (2) The electromagnetic chuck device for a grinding machine according to claim 1, wherein the low thermal expansion alloy is an invar alloy. (3) A backing plate made of a magnetic metal material with excellent wear resistance is provided at the tip of the chuck shaft, and the tip surface of the backing plate is the workpiece attraction surface. An electromagnetic chuck device for a grinding machine according to item 2.