JPS603551B2 - Workpiece rotation abnormality detection method and device - Google Patents

Description

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

Shoe type centerless grinding machine, that is, the two shoes align the workpiece in the vertical direction, and the driving puto adjusts the axial position, and at the same time, it gives rotation to the workpiece, and the workpiece and driving plate are aligned. For example, when producing a large number of circular workpieces on a production line in a shoe-type centerless grinding machine, which uses magnets to ensure that they are in close contact with each other, especially when producing at high efficiency,
Among the workpieces produced there, there may be a part of the circumference that has been ground flat.

This part sometimes suffers from grinding burns. In addition, many flat or wavy marks appear on the circumference of the workpiece, and if you look at these marks, you may find that grinding burns have occurred on the machine. 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 effect 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 being pushed to 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 in which a small piece of summer rust is applied to a workpiece, the workpiece is rotated together with the workpiece, and the rotation of this true key is detected by a non-contact sensor. , removal is troublesome, and this method cannot be used in mass production. The purpose of this invention is to reliably detect the rotational speed abnormality of a workpiece during grinding as described above from the essential phenomenon aspect. The present invention provides a method for detecting an abnormality in the rotational speed of a workpiece, and a detection device embodying the same, characterized in that the abnormality in the rotational speed of the workpiece is detected as an abnormal change in the magnitude of the tangential force.

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 the start of grinding, when the workpiece is only being rotated by the drive shaft, the force applied to the shoe is extremely small, but once grinding has started (see point A) and progresses at a constant cutting speed. , the grinding force of the whetstone increases sequentially, and the tangential and normal forces between the whetstone and the workpiece increase.Therefore, the tangential and normal forces applied to the shoe increase linearly, and eventually F
A point is reached and a certain depth of cut is completed at this point, after which there is a spark out, then the grinding wheel retreats and both the tangential and normal forces decrease rapidly. When the workpiece is properly ground, the tangential and normal forces acting on the shoe during grinding increase linearly, as shown in Figure 1. However, during various grinding experiments, the inventor I encountered the results shown in the figure.

Until the start of grinding at point A, the machine follows the same process as in Figure 1, and to a certain extent after the start of grinding, both the tangential force and the normal force increase almost 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 normal force in this darkness.

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 diameter surface of the workpiece is investigated, it is found that the workpiece is brazed by the work stop, has a flat part on the outer surface, or has an ave. A mark was found. Such abnormal rotational speed of the workpiece is caused by an increase in tangential force, which causes an abnormal rotational speed, or a case where the grindstone causes an abnormal rotational speed (high-speed rotation) of the workpiece, resulting in a sudden increase in tangential force and rotational speed abnormality. This may lead to speed abnormality (work stop).
It was confirmed that in order to detect abnormalities in the rotational speed of a workpiece as described above, it is sufficient to detect changes in the tangential force and normal force applied to the shoe, especially abnormal changes in the tangential force.

A device for detecting this change in tangential force will be described below. Reference numeral 1 denotes a grindstone for grinding a workpiece 2, and the workpiece 2 is rotated by a driving play (not shown).

3 is a shoe holder.A front shoe 4 and a rear shoe 5 are attached to this shoe holder 3.The front shoe 4 is provided with a shoe tip 6 so as to be in contact with the outer peripheral surface of the workpiece 2, and the rear shoe 5 is provided with a shoe tip 6. A shoe tip 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 gravity strain, or the like. In this embodiment, a piezoelectric load cell 7 is used as a front-layer amplifier for converting the electric charge corresponding to the magnitude of the tangential force detected by the piezoelectric load cell 7 into a voltage, that is, converting the electric charge into a voltage. , a charge amplifier 9 is provided,
A reset circuit 10 is connected to the charge amplifier 9 for transmitting a reset signal, and the charge amplifier 9 is further connected to an amplifier 11 for signal amplification. On the other hand, the material of the shoe tip, the material of the workpiece and the grinding speed,
A set voltage circuit 12 is provided which sets a predetermined magnitude of tangential force in consideration of grinding force, etc., and a circuit for comparing this set value with the signal value amplified by the front layer amplifier 11 is provided. This is circuit 13. In this device, a workpiece 2 is set on a shoe chip and begins to rotate by a driving plate of a drive shaft (not shown), and when a signal is sent from a reset circuit 10 to a charge amplifier 9,
The tangential force detected by the load cell 7 via the shoe chip 8 is converted into a voltage by the charge amplifier 9, this voltage is amplified by the amplifier 11, and enters the comparator circuit 13. In this comparison circuit 13, the signal from the load cell 7, that is, the tangential force, is compared with a preset tangential force value from the set voltage circuit 12. The tangential force setting value is determined experimentally based on the grinding speed, the rotational speed of the workpiece, the size of the workpiece, etc. If the comparison circuit 13 outputs a signal exceeding the tangential force setting value, it is determined that there has been a sudden change in the contact state with the workpiece shoe tip and that an abnormal rotation has occurred in the workpiece. If the signal from the comparison circuit is small compared to the tangential force setting value, no signal is generated, the workpiece rotates without any abnormality, and it is determined that the grinding is performed normally. In the embodiment shown below, the process of converting a signal from the load cell into a voltage by the charge amplifier 9 and amplifying this by the amplifier 11 is the same as that of the first device, so some illustrations are omitted.

Therefore, the block diagram of the charge amplifier 9 and subsequent parts will be explained here. 10 is a reset circuit, 14 is a delay circuit for sending a signal with a certain time difference, and 15 is an arithmetic circuit for calculating the signal passed through the delay circuit 14 and the signal from the amplifier 11.

A comparison circuit 16 is provided to compare the signal from the arithmetic circuit 15 with the signal from the set voltage circuit 17 whose magnification is set in advance. A timer 18 is connected to the logic circuit 19 and is provided to take out a signal based on the magnitude of the tangential force after a predetermined time has elapsed (actually about several seconds) after the start of grinding.

This device also has a reset circuit 1 like the first device.
0, a reset signal is sent to the charge amplifier 9,
The tangential force detected by a load cell (not shown) is
It is converted into a voltage by the charge amplifier 9, and this voltage signal is amplified by the amplifier 11 and enters the arithmetic circuit. On the other hand, the signal that has passed through the delay circuit 14, that is, the signal based on the magnitude of the tangential force delayed for a certain time, also enters the calculation circuit 15, and in this calculation circuit 15, a signal based on the reinforcement force that changes from time to time, A signal blocking the tangential force delayed for a certain time is calculated. This calculated value and the set value from the set voltage circuit are compared in the comparator circuit 16, and the signal from the comparator circuit 16 is input to the logic circuit 19. , depending on the magnitude of the signal value, is taken out as an output from the logic circuit 19. In other words, at the same time as grinding starts, no output signal is generated from the logic circuit even if there is a large change in the tangential force on the scale. Grinding is started, and after a certain set time elapses, a signal is taken out as an output based on the change in the tangential force. If a sudden change occurs in the tangential force, an output signal is sent from the logic circuit and an abnormal rotation speed of the workpiece is detected. Note that in the first and second embodiments described above, a low-pass filter is provided between the charge amplifier and the amplifier if necessary. Since the device of this invention is configured as described above, the grinding speed is slowed down to shorten the grinding cycle time, and even if an abnormality in the rotational speed of the workpiece occurs, it can be detected almost reliably. It is possible to improve the quality of the outer peripheral surface of the object, prevent the danger of converting a defective product into a non-defective product, and improve grinding efficiency.

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

[Brief explanation of the drawing]

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 is set in the shoe to the completion of grinding, which is the basis of this invention. 2 shows the case where no rotational speed abnormality occurs in the workpiece, FIG. 2 is a diagram showing the case in which the rotational speed abnormality occurs in the workpiece, and FIGS. 3 and 4 respectively show examples of the present invention. , FIG. 3 is a schematic diagram of the device including a block diagram;
FIG. 4 shows a block diagram with some parts of the device omitted. Explanation of symbols 1 is a grinding wheel, 2 is a workpiece, 3 is a shoe holder, 4 is a front shoe, 6 is a rear shoe, 6 is a shoe chip, 7 is a load cell, 8 is a shoe chip, 9 is a charge amplifier, 10 is a reset circuit, 12 is a shoe holder Setting circuit, 1
3 is a comparison circuit, 14 is a delay circuit, 15 is an arithmetic circuit, 16
is a comparison circuit, 17 is a setting voltage circuit, 18 is a timer, 1
9 is a logic circuit. Many figures, many two figures. S sardines illustration 4

Claims (1)

[Scope of Claims] 1. In a shoe-type centerless grinding machine equipped with a driving plate that rotates the workpiece by contacting one end surface of the workpiece, and a shoe that supports the outer circumferential surface of the workpiece, the grinding machine is used for grinding a workpiece. A method for detecting an abnormal rotational speed of a workpiece, comprising: detecting a tangential force acting on a shoe in the workpiece, and detecting an abnormal rotational speed of the workpiece as an abnormal change in the tangential force. 2. In a shoe-type centerless grinding machine equipped with a driving 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 magnitude of the tangential force acting on the shoe is determined. A force transducing element for detection, a preamplifier provided to convert the signal from the force transducing element into voltage, a reset circuit for transmitting a reset signal to the preamplifier, and a tangential force converter. A rotation speed abnormality detection device for a workpiece, comprising a set voltage circuit whose size is set in advance, and a comparison circuit that compares a set signal of the set voltage circuit with a signal from a preamplifier. 3 In a shoe-type centerless grinding machine equipped with a driving 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 magnitude of the tangential force acting on the shoe is determined. A force transducer for detection, a preamplifier provided to convert the signal from the force transducer into voltage, a reset circuit for sending a reset signal to the preamplifier, and a reset circuit for transmitting a reset signal to the preamplifier. A delay circuit for extracting a signal based on tangential force after a certain time delay, an arithmetic circuit for calculating a signal based on tangential force during grinding and a signal delayed by the delay circuit, and a magnification factor set in advance. A rotation speed abnormality detection device for a workpiece, comprising: a set voltage circuit; and a comparison circuit that compares a set signal of the set voltage circuit with a signal from the arithmetic circuit.