JPS603550B2 - Workpiece rotation abnormality detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting an abnormal rotational speed of a workpiece being ground in a shoe type centerless grinding machine, and a detection method thereof.

A shoe type centerless grinder, in other words, the two shoes are used to level the workpiece in the crosswise direction, and the driver plate determines the position in the crosswise direction, and at the same time this gives rotation to the workpiece, and the workpiece and driver plate are For example, when producing a large number of circular workpieces on a production lie in a shoe-type centerless grinding machine that uses magnets to achieve close contact, especially when producing at high efficiency, Among workpieces that have been ground, there may be a part of the workpiece that has been ground flat on one side.

This part sometimes suffers from grinding burns. Additionally, many flat or wavy marks may appear on the circumference of the workpiece, and if you look at these marks, you may find that grinding burns have also occurred. As mentioned above, it is extremely rare for a part of a circular workpiece to be ground flat, resulting in grinding or scratches, but it can have a fatal impact on the performance of the product.
For example, if a flat portion occurs on the outer circumferential surface during grinding of a bearing ring, it is a defective bearing ring and must be removed, and the occurrence of such defective products should be completely eliminated.

On the other hand, efficiency is in the process of reaching its limits, and as that happens, the frequency of its occurrence is bound to increase. The above phenomenon often occurs when the rotational speed of the workpiece is abnormal during grinding.There is a method to detect this rotational speed abnormality by directly detecting the rotation of the workpiece, but it is not possible to do so in a laboratory. For example, there is a method of attaching a small coin to the workpiece, rotating it together with the workpiece, and detecting the rotation of this true mirror using a non-contact sensor. It is troublesome to remove and is not a method that can be used in mass production. The purpose of this invention is to reliably detect abnormalities in the rotational speed of a workpiece during grinding as described above from the viewpoint of the essential phenomena. A method for detecting abnormal rotation speed of a workpiece, which is characterized in that the detected friction coefficient is compared with a predetermined set value of the friction coefficient, and an abnormal rotation of the workpiece is detected as an abnormality in the friction coefficient based on the magnitude relationship. This is a concrete detection device.

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows the force applied to the shoe during outer diameter grinding of a workpiece in a shoe-type centerless grinder, extracted as normal force and tangential force from before the start of grinding to completion of grinding and when the grinding wheel is retracted. This shows a case where the workpiece has been successfully ground. Immediately before grinding starts because the workpiece is only being rotated by the drive shaft, the force applied to the shoe is very small, but once grinding has started (see point A) and the grinding progresses at a constant cutting speed, The grinding force of the grinding wheel increases sequentially, the tangential force and normal force between the grinding wheel and the workpiece increase, and therefore the tangential force and normal force applied to the shoe increase linearly and eventually reach point F, at which point After completing a certain amount of cut, the spark out occurs, and then the grinding wheel retreats, and both the tangential force and the normal force decrease rapidly. When a workpiece is properly ground, the tangential and normal forces acting on the shoe during grinding increase almost linearly as shown in Figure 1, but during various grinding experiments, the inventor found that I encountered a result like the one shown.

Until the start of grinding at point A, the process is similar to that shown in Figure 1, and to a certain extent after the start of grinding, both the tangential force and the normal force increase linearly with the passage of time, but when they reach point B, The tangential force increases rapidly, and as the normal force increases, the increase in tangential force becomes larger over time. (See point C)
However, there is almost no sudden increase in the normal force during this period.

As the grinding continues in this state, the magnitude of the tangential force increases until the work stops completely at point D. When the diagram shown in Fig. 2 is obtained, each time the outer ridge of the workpiece is investigated, it is found that the workpiece has glazing due to the work stop, a flat part on the outer ridge, or a wave. A mark was found. In order to detect abnormalities in the rotational speed of the workpiece, it is necessary to detect changes in the tangential force and normal force applied to the shoe, especially changes in which the tangential force increases rapidly. It was concluded that it is best to detect the change in the coefficient of friction with the workpiece (see Figure 3), that is, the value obtained by dividing the tangential force by the normal force.

The magnitude of the friction coefficient, as shown in Fig. 3, remains approximately constant when the workpiece rotates normally during grinding, and shows almost no change until the grinding is complete. If an abnormal rotation speed of the workpiece occurs during the process, the value increases rapidly.

Such an abnormal rotation speed of the workpiece is caused by a local sticking phenomenon between the shoe and the workpiece, which increases the coefficient of friction, resulting in an abnormal rotational speed, or when the grindstone causes an abnormal rotational speed of the workpiece. (high-speed rotation) occurs, resulting in an increase in the coefficient of friction,
It is conceivable that the rotation speed may become abnormal.

A device for detecting this friction coefficient will be described below.
1 is a grindstone for grinding a workpiece 2, and the workpiece 2 is rotated by a drying plate (not shown).

3 is a shoe holder, a front shoe 4 and a rear shoe 5 are attached to the shoe holder 3, a shoe tip 6 is provided on the front shoe 4 so as to be in contact with the outer peripheral surface of the workpiece 2, and a shoe tip 6 is provided on the rear shoe 5. A shoot chip 8 is attached via a force transducing element 7.

The force transducing element 7 is a detector for detecting the force applied to the shoe via the shoe tip, and may be a load cell, a strain gauge, a gauge using magnetostriction, or the like. In this embodiment, a piezoelectric load cell is used, and this piezoelectric load cell can detect forces in three directions. A charge amplifier 9 and a charge amplifier 10 are used as front-layer amplifiers to convert charges corresponding to the magnitude of the tangential force and normal force captured by the piezoelectric load cell 7 into voltages, that is, to convert charges into voltages. A reset circuit 11 is connected to each charge amplifier for transmitting a reset signal, and amplifiers 12 and 13 are connected to each charge amplifier for signal amplification.
This amplifier includes an arithmetic circuit 14 for dividing a signal based on the magnitude of the tangential force by a signal based on the magnitude of the normal force.
is connected. In addition, a set voltage circuit 15 is provided which sets a predetermined friction coefficient in consideration of the material of the shoe chip, the material of the workpiece, the grinding speed, etc., and is used to compare this set value with the signal value from the calculation circuit 14. This circuit is the comparison circuit 16. Note that a low-pass filter is provided between the charge amplifier and the amplifier if necessary. In this device, a workpiece 2 is set on a shoe chip, and a reset signal is sent from a reset circuit 11 to each charge amplifier 9, 10.
'When this is transmitted, the load cell 7 is sent via the shoe tip 8.
The tangential force detected by the charge amplifier 9 is converted into a voltage by the charge amplifier 9, this voltage is amplified by the amplifier 12, and then input to the arithmetic circuit 14. On the other hand, the normal force detected by the load cell 7 is converted into a voltage by a charge amplifier 10, amplified by an amplifier 13, and then arithmetic circuit 14.
Then, division is performed in step (b), and further, in the comparison circuit 16, it is compared with the friction coefficient setting value from the preset setting voltage circuit 15. If this comparison circuit outputs a signal exceeding the friction coefficient setting value, it is determined that there has been a sudden change in the contact state between the workpiece and the shoe tip, and that an abnormal rotation speed has occurred in the workpiece.

If the signal from the comparison circuit is small compared to the friction coefficient set value, it is determined that no signal is generated, the workpiece rotates without any abnormality, and the grinding is performed normally. Since the device of the present invention is configured as described above, the grinding speed is slowed down to shorten the grinding cycle time, and even if an abnormal rotation speed of the workpiece occurs, it can be reliably detected. This prevents the risk of using a product with inferior quality on the outer peripheral surface as a good product, and it is possible to increase the grinding efficiency.

In addition, since it is possible to detect subtle rotational malfunctions of the workpiece, the quality of the outer peripheral surface of the workpiece is reliably improved, and workpieces of stable quality can always be obtained.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams that detect changes in the tangential force and normal force applied to the shoe from the time the workpiece, which is the basis of this invention, is set on the shoe until the completion of grinding.
Figure 1 shows the case where no rotational speed abnormality occurs in the workpiece, Figure 2 shows the case where the rotational speed abnormality occurs in the workpiece, and Figure 3 shows the graph after the workpiece is set in the shoe. FIG. 4 is a diagram showing changes in the coefficient of friction between the workpiece and the shoe until the grinding is completed. FIG. 4 is a schematic diagram including a block diagram showing an embodiment of the present invention. Explanation of symbols 1 is a grinding wheel, 2 is a workpiece, 3 is a shoe holder, 4 is a front shoe, 5 is a rear shoe, 6 is a shoe tip, 7 is a piezoelectric load cell, 8 is a shoe chip, 9
is a charge amplifier, 10 is a charge amplifier, 11 is a reset circuit, 14 is an arithmetic circuit, 15 is a setting voltage circuit, 16
is a comparison circuit. Tsutomu 1 Zuta 2 Ticket 3t2 Tsutomu 4 Momi

Claims (1)

[Scope of Claims] 1. A shoe-type centerless grinding machine equipped with a drying plate that rotates the workpiece by contacting one end surface of the workpiece, and a shoe that supports the outer peripheral surface of the workpiece. The normal force and tangential force acting on the shoe inside are detected, the friction coefficient between the workpiece and the shoe is detected as the tangential force divided by the normal force, and the obtained friction coefficient is set as the set value. A method for detecting an abnormal rotational speed of a workpiece, characterized in that an abnormality in the rotational speed of a workpiece is detected as an abnormality in the coefficient of friction based on the magnitude relationship. 2 In a shoe-type centerless grinding machine equipped with a drying plate that rotates the workpiece by contacting one end surface of the workpiece, and a shoe that supports the outer peripheral surface of the workpiece, the normal force and tangential force acting on the shoe are A force transducer element for detecting the magnitude of force, a preamplifier provided individually to convert each signal from the force transducer element into voltage, and a reset signal sent to each preamplifier. a reset circuit for dividing the signal based on the magnitude of the tangential force by a signal based on the magnitude of the normal force, a setting voltage circuit for presetting the magnitude of the friction coefficient, and a setting voltage circuit for presetting the magnitude of the friction coefficient. A rotation speed abnormality detection device for a workpiece, comprising a comparison circuit that compares a setting signal of a voltage circuit and a signal from the arithmetic circuit.