JPH0426984B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a grinding machine that improves grinding accuracy by limiting the amount of deflection of a workpiece during grinding within a certain range, and controls the optimum grinding speed. This invention relates to a wheel feed control device.

A conventional grinding wheel feed control device in a grinding machine controls the feed amount of the grinding wheel so that the grinding resistance is always constant. When the grinding resistance is constant, the amount of deflection of the workpiece changes depending on the rigidity of the workpiece. In other words, if the rigidity of the workpiece material is low, it will deflect significantly. A large amount of deflection causes cracks to occur, resulting in poor finished dimensional accuracy and reduced roundness. Therefore, it was necessary to change the setting value of the grinding resistance depending on the rigidity of the workpiece material. Determining this setting required a lot of experimentation,
It required intuition. Therefore, when setting grinding conditions, the grinding speed is generally slowed down to ensure safety.
In order to reduce the amount of deflection, the machining time was long, which resulted in poor machining efficiency.

On the other hand, in order to improve this drawback, a wheel feed control device is designed to keep the amount of deflection of the workpiece constant during grinding, whereas the above device keeps the grinding resistance constant. A device for controlling the feeding of is known. This device measures the outer diameter dimension X of the work material during grinding, and measures the final finished outer diameter dimension W of the work material.
Calculate the machining allowance (X-W) at that time from the relationship with The amount of deflection of the cutting material was calculated as 2Z=(X-W)-2Y. Then, the feed amount Y was controlled so that this deflection amount 2Z was always constant.

However, this method does not measure the position of the grinding surface of the grinding wheel, but rather the position of the feed of the wheel head to which the grinding wheel is fixed, so the position of the grinding surface cannot always be accurately measured. It was not something that would be done. In other words, the radius of the grinding wheel decreases during grinding, and the wheel head also undergoes thermal deformation, causing the position of the wheel on the wheel head to change slightly.Furthermore, the wear of the dresser and the amount of cut of the dresser decrease. , the position of the grinding surface of the wheel was not necessarily determined by the position of the wheel head due to an error with the wheel head correction amount.

Therefore, the amount of deflection of the workpiece measured by this method includes errors, making it impossible to accurately control the feed of the grinding wheel.

The present invention has been made in order to improve these conventional drawbacks, and is based on the data measured during grinding by means for detecting the outer diameter of the workpiece, and calculates the deflection during grinding. By calculating the amount,
The amount of deflection is measured with high accuracy, and the subsequent grinding speed is calculated from this amount of deflection.

That is, the present invention includes a diameter measuring means for measuring the diameter of a workpiece, and a rotationally driven wheel that supports the workpiece so as to be able to move forward and backward with respect to the workpiece. Therefore, the work material is ground by a wheel drive means, and the grinding process is divided into a first grinding process in which the material is ground at a first feed rate and a second grinding process in which the material is ground at a second feed rate. In the grinding wheel feed control device of the grinding machine, the feed rate is set to zero or close to zero within a set time so that the work material is not deflected between the first grinding process and the second grinding process. a deflection means that performs grinding at a slow speed; a radius r2 of the workpiece is inputted from the diameter measuring means before grinding by the deflection removing means; and a radius r2 of the workpiece is input from the diameter measuring means after grinding by the deflection removing means; Input the radius of the workpiece material r1, and then calculate the formula δr= from the depth of cut 2Δ of the grindstone per revolution of the workpiece material.
(r2-r1-Δ) to obtain the deflection amount δr of the work material; and second calculation means for setting the feed rate of the process.

Next, the principle of the present invention will be explained.

FIG. 1 shows a principle diagram of how the amount of deflection of a workpiece is measured by the apparatus of the present invention. The grinding wheel rotates around the central axis 03 and grinds the workpiece 1.
0 and grinds. If there is no deflection in the workpiece, the workpiece is a cylinder 12 centered on the axis 01.
It has an outer diameter as follows. However, due to the grinding force of the grinding wheel, the workpiece 10 is deflected and becomes 0.
It bends into a shape like a cylinder 14 centered on two axes.
The amount of deflection can be expressed by the distance δ between the axes 01 and 02. If the feeding of the grinding wheel is stopped in a state where this amount of deflection δr has occurred, the workpiece will generate an elastic force such that the 02 axis overlaps the 01 axis due to the spring back action proportional to the amount of deflection. Therefore, even if the feed speed of the grinding wheel is zero,
In order for the workpiece to press its own grinding surface into contact with the grinding wheel, the surface of the workpiece is ground so that ideally, the 02 axis overlaps the 01 axis,
It will be ground into the shape of a cylinder 16 having a cylinder radius r1.

Therefore, the radius r2 of the workpiece is measured at the time when the feed of the grinding wheel is stopped. Here, until the feeding of the grinding wheel is stopped, the workpiece moves in a spiral with the 02 axis as the center and the minimum radius is the distance from the point of contact between the workpiece and the grinding wheel to the 02 axis. It is ground into shape. (The depth of cut per revolution of the grinding wheel at this time is 2Δ.) Therefore, even if the feeding of the grinding wheel is stopped, the shape will not be a perfect circle centered on the 02 axis having the minimum radius. The non-circular portion of the workpiece is ground by one rotation of the workpiece, independent of the springback effect. Therefore, the part measured when the grinding wheel is stopped includes a non-circular part of 2Δ in the diameter direction, and when converted to per radius, it is calculated by subtracting Δ from radius r2 (r2 - Δ) is the minimum radius removed by this non-circular part, and this radius (r2
-∆) after a while after stopping the feed (at least enough time for most of the deflection to be ground)
The difference (r2−
r1−Δ) is equal to the amount of deflection δr mentioned above.

The device of the present invention applies the above principle. That is, in the first stage of grinding, the grinding wheel is fed at a constant speed, the feeding is stopped at a specific time, and the amount of deflection is calculated by measuring the amount of change in the outer diameter of the workpiece for a predetermined period of time. Measure. The feed speed of the grinding wheel is calculated according to the amount of deflection, that is, so that the amount of deflection during subsequent grinding is within a certain limit of deflection amount. Then, in the grinding after calculating the amount of deflection, the feed of the grinding wheel is controlled by the speed described above, and the grinding is continued until the fine grinding process is started. still,
To measure the amount of deflection, it is preferable to stop the feed of the grinding wheel, but in cases where the work material is highly rigid, even if the feed speed is reduced to a level where the amount of strain can be ignored. good.

Hereinafter, the present invention will be further explained in detail based on specific examples.

FIG. 2 is a block diagram showing the specific configuration of this embodiment.

The control device of the present invention mainly consists of a means for detecting the outer diameter of the workpiece, a control means, and a means for driving the grinding wheel. The outer diameter detection means of the workpiece includes a pair of contacts 40 that are in contact with the outer surface of the workpiece 10 at two points, and an actuating transformer 42 or other position detector that converts the amount of displacement into an electrical signal. It is becoming established. An electrical signal proportional to the outer diameter detected by the pair of contacts 40 is input to an input terminal of the control means 50. The control means 50 has a predetermined configuration as will be described later, and its output signal is outputted to a drive circuit 74 that drives the delivery of the grinding wheel. The drive circuit 74 is directly connected to the servo motor and is coupled to drive the servo motor in accordance with a control signal. Servo motor 32
is a nut 2 that rotates the feed screw 26 directly connected to the shaft of the servo motor and meshes with the feed screw 26.
Send out 4. Since the nut 24 is fixed to the grinding head 22, the rotating force of the feed screw 26 causes the grinding wheel to move linearly toward or away from the workpiece. The grinding wheel head 22 is slidably mounted on the intermediate base 30. The grinding wheel 2 is rotatably attached to the grinding head 22. On the other hand, the intermediate base 30 is fixed to the upper surface of the bed 28.
Further, an actuating transformer 42, which constitutes a part of the outer diameter detection means of the workpiece, is fixed to a support base 46 connected to the table 44 fixed to one end surface of the bed 28. And a pair of contacts 4
0 is supported so that it can be displaced in the radial direction of the workpiece 10.

Next, the control means 50 according to the gist of the present invention will be described.

The control means 50 has an amplifier 52 that inputs and amplifies the signal from the outer diameter detection means. Amplifier 52 amplifies the measurement signal and outputs it to comparison circuit 54 connected thereto. The comparator circuit 54 has a predetermined reference setting value set in advance, and when the measurement signal reaches this predetermined reference setting value, it outputs a position signal to that effect to the processing device 70. On the other hand, the position signal output from the comparator circuit 54 is input to a delay circuit 60 and gated to a sample and hold circuit 56. The sample and hold circuit 56 is configured to also input the measurement signal described above. Similarly, the sample and hold circuit 58 inputs the measurement signal and also uses the output signal of the delay circuit 60 as a gate input. Sample hold circuit 56,5
The measurement signal sampled and held by 8 is input to a subtraction circuit 64, and this subtraction circuit 64 constitutes a first calculation means for calculating the amount of deflection of the workpiece. . The output from the subtraction circuit 64 converts the measurement signal into a digital quantity via an AD converter 66, and inputs the converted signal to an arithmetic circuit 68. On the other hand, the arithmetic circuit 68 receives the time signal (α ₁ +α ₂ ) through the delay circuit 62 . and,
The arithmetic circuit 68 calculates the deflection using a predetermined method in synchronization with the time signal, and sends the value to the processing device 70.
Output to. The processing device 70 performs a predetermined calculation based on the information and sends a command pulse for sending out the grinding wheel to the deviation counter 72. The deviation counter 72 receives the output signal from the rotation amount detector 34 connected to the shaft of the servo motor 32 as a feedback input and subtracts the number of pulses. The value of the deviation counter 72 is proportional to the amount to be fed by the grinding wheel, and the grinding wheel is fed until the value becomes zero. Based on the value of the deviation counter 72, the drive circuit 74 sends out an output signal to rotate the servo motor at a predetermined speed to a predetermined position. A speed signal detected from a speed detector 36 directly connected to the shaft of the servo motor 32 is fed back to the drive circuit 74 to control the servo motor 32 at a constant speed.

The above is the specific configuration of the embodiment of the device of the present invention.

Next, the operation of the device of the present invention based on such a configuration will be described.

FIG. 3 is a cycle diagram when the grinding wheel is sent out using the control device of the present invention. P0 in the diagram
The point is when there is a space between the grinding surface of the grinding wheel and the workpiece, and the positional relationship is such that no grinding is being performed.
Move the grinding wheel a predetermined distance D from point P0 to P1
leading to. Immediately after P1, the grinding surface of the grinding wheel comes into contact with the workpiece and begins grinding. From P1, the workpiece is ground at a constant feed rate, leading to P2.
Here, P2 is the position when the measurement signal measured by the differential transformer 42 reaches a predetermined value, that is, AS1. When the comparator 54 sends its position signal (AS1 signal) to the processing device 70, the processing device 70 acts to stop the delivery of the grinding wheel. Then, the period during which transmission is stopped is P2
The time from the point to the P3 point is T1.

During this time, the workpiece is being ground for this predetermined period of time due to spring back, as described in the deflection measurement principle above. Therefore, the sample and hold circuit 56 first samples and holds the numerical value of the radius r2 of the workpiece at the time when P2 is reached.
On the other hand, the sample and hold circuit 58 samples and holds the radius r1 of the workpiece at a time after a delay time α1 slightly shorter than the time T1 after reaching P2. The two outputs of the sample and hold circuits 56 and 58 are then output to a subtraction circuit 64.
Therefore, the amount of deflection δr is calculated using the formula r2−r1−Δ. This value is the amount by which the workpiece was ground by its own spring back action while the grinding wheel stopped feeding. Then, the analog quantity representing this deflection amount δr is converted to an AD converter 66.
After converting into a digital quantity by
Output to. The arithmetic circuit 68 calculates the detected deflection amount δr
The ratio to the standard amount of deflection δs is calculated and multiplied by the proportionality constant K to obtain the deflection rate. This deflection rate is output to the processing device 70. and,
Here, according to the deflection rate, the feed speed of the grinding wheel is calculated so that the amount of deflection falls within a certain limit range. After a predetermined time T1 has elapsed, that is, at point P3, the grinding wheel is sent out according to its speed. And as a result, the grinding wheel has a speed of FM
You will be sent up to P4 points. Point P4 is when the value detected by the differential transformer becomes AS2, which is a preset value. After point P4, it is a fine grinding area where smoother grinding is performed. When the control means detects that the fine grinding region has been entered, the comparison circuit 54 sends an AS2 signal to the processing device 70. The processing device 70 detects this signal, calculates a fine grinding speed according to the deflection rate, and sends out the grinding wheel at the calculated fine grinding speed. As a result, you will reach P5 points. Point P5 is the point in time when the measured outer diameter of the workpiece detected from the pair of contacts 40 reaches AS3. When this point is reached, comparator circuit 54 transfers the AS3 signal to processing circuit 7.
0, and the processing circuit 70 detects the signal and stops feeding the grinding wheel for a predetermined period (T2). This waiting period is a time for taking up the slight amount of deflection that occurs during fine grinding. Then, after reaching the P6 point after T2 has elapsed, the grinding wheel is fast forwarded backwards and reaches the P7 point. In this way, one cycle of the grinding process is completed.

Next, the operation of the processing device 70 will be explained.

FIG. 4 is a flowchart showing the operation of the processing device 70. In step 102, a speed is set to feed the grinding wheel to a predetermined position. Then, in step 104, a pulse example having a predetermined number of pulses and pulse period is generated according to the position and velocity set in the previous step 102. In the next step 106, the previous step 1
In step 04, idle cutting feed is performed, and after the grinding wheel comes into contact with the workpiece in a straight line state, the first rough grinding feed rate (FR) is set. In the next step 108,
In the previous step 106, one unit of the grinding wheel is fed according to the set speed. In the next step 110, when the outer diameter dimension data of the workpiece reaches a predetermined value, the AS1 signal is input from the comparator circuit 54, but if that signal is input, the process moves to the next step 112. If the signal has not yet been input, the process returns to step 108 and repeats the grinding wheel feeding process. In step 112, grinding has progressed to a predetermined position, and the feeding of the grinding wheel is stopped for T1 seconds. Then, in the next step 114, since the deflection rate of the workpiece has been calculated during the stop period as described above, that data is input. In the next step 116, a second speed is set that is inversely proportional to the deflection rate.
Set as coarse grinding feed rate (FM). In step 118, the grinding wheel is fed per unit according to the speed set in step 116. If the AS2 signal is input in the next step 120, the feeding is stopped and the process proceeds to step 122. If the signal AS2 has not been input yet, the process returns to step 118 and control is performed to send out the grinding wheel one unit at a time. In step 122, since the preprocessing has been performed up to point P4 shown in FIG. 3, in step 122, the polishing feed rate FF, which changes in inverse proportion to the deflection rate A, is set. Note that FFR is the standard sharpening feed rate. Next, in step 124, feed control is similarly performed unit by unit according to the speed.
In step 126, if the AS3 signal is input, it means that the grinding has progressed to the predetermined point P5, so in step 128, the feeding is stopped for T2 seconds. On the other hand, if the AS3 signal is not input, since the P5 point has not yet been reached, the process returns to step 124 and performs feed control one unit at a time. By stopping the feed for T2 seconds in step 128, only a very small width is ground due to the spring back action of the workpiece. Then, when the P6 point is reached, fast forward backward processing is performed in step 130. In step 130, the retraction position and speed for fast forward and retraction processing are set. In the next step 132, pulses are generated according to the retreat distance and speed set in step 130. In this way, one grinding process is completed. In the embodiment described above, the subtraction circuit 64
The second calculation means for setting the feed rate inversely proportional to the amount of deflection outputted from the first calculation means as the feed rate for the second grinding process is composed of the calculation circuit 68 and step 116 in the processing device 70. Ru.

In the second grinding, if the workpiece is of the same type, grinding may be performed at an appropriate speed from the beginning based on the amount of deflection measured in the first grinding.

In the embodiments described above, part of the control means 50 is processed by an analog circuit, and part of it is processed by a digital circuit or a microprocessor. However, the processing in this embodiment requires an outer diameter measurement sensor, an AD converter that converts this analog signal into a digital quantity, a series of digital computer systems that input this signal, and a signal that is sent to a drive circuit according to this processed data. It can also be configured by using an output interface that sends out the .

In summary, the present invention temporarily stops grinding or slows down the grinding speed to a very low value at any specified time in the grinding stage, and during that time, the spring-back action of the workpiece material reduces the width of the workpiece to be ground. Detects the amount of deflection of the material. Then, using this actually measured amount of deflection, subsequent grinding is performed at a speed such that the amount of deflection falls within an appropriate range.

Therefore, according to the apparatus of the present invention, since the amount of deflection of the workpiece is directly determined from the sensor for measuring the outer diameter of the workpiece, the measurement of the amount of deflection is extremely accurate. or,
As described above, this control device controls the feed of the grinding wheel so that the amount of deflection is within a certain range, so optimal control is performed regardless of the rigidity of the workpiece. In addition, because the measurement accuracy of the amount of deflection is high,
The final machining accuracy is also high, and the detection speed is fast because the grinding wheel is sent out at the maximum speed within the allowable deflection limit.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of measuring the amount of deflection of a workpiece measured by the device of the present invention.
FIG. 2 is a specific configuration diagram of a control device showing a specific embodiment of the device of the present invention. FIG. 3 is a cycle diagram showing the feed control of the grinding wheel by the control device used in the same embodiment. FIG. 4 is a flowchart showing the processing of the processing apparatus used in the same example. 2... Grinding wheel, 10... Work material, 54... Comparison circuit, 56, 58... Sample hold circuit,
64... Subtraction circuit, 70... Processing device, 72...
Deviation counter, 74...drive circuit, 32...servo motor.

Claims (1)

[Scope of Claims] 1. A diameter measuring means for measuring the diameter of a workpiece, and a rotationally driven wheel are supported so as to be movable forward and backward relative to the workpiece, and a predetermined feed rate is set, and the wheel is rotated. A wheel drive means is provided for grinding the work material by a wheel, and the workpiece is divided into a first grinding process in which the material is ground at a first feed rate and a second grinding process in which the material is ground at a second feed rate. In a grinding wheel feed control device for a grinding machine that performs grinding, between the first grinding process and the second grinding process,
a deflection removing means that performs grinding by setting the feed rate to zero or a very low speed close to it within a set time such that the deflection of the workpiece is eliminated, and a diameter measuring means before grinding by the deflection removing means Input the radius r2 of the workpiece, input the radius r1 of the workpiece from the diameter measuring means after grinding by the deflection removing means, and further calculate the formula δr from the depth of cut 2Δ of the grinding wheel per revolution of the workpiece. = (r2−r1−
The first step is to calculate the amount of deflection δr of the workpiece material by calculating Δ).
and the deflection amount δr output from the first calculation means.
A grinding wheel feed control device for a grinding machine, comprising: second calculation means for setting a feed rate inversely proportional to as the feed rate for the second grinding process.