JPS6010865B2 - Cam grinding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cam grinding method for grinding a cam of a workpiece such as a camshaft using a grinding wheel whose abrasive grains are made of a hard material such as cubic crystal nitride, and its purpose is to The object of the present invention is to shorten the machining time of the cam without reducing the cam blowfill accuracy and machining surface accuracy.

Recently, grinding wheels with low grinding resistance that use hard materials such as cubic nitride grains as abrasive grains have been developed, making it possible to machine workpieces at several times the feed rate compared to conventional grinding wheels.

However, if the workpiece is rotated at the same speed as when machining with a conventional grinding wheel, for example 60 revolutions per minute, excessive force is applied to the abrasive grains. It has been confirmed through experiments that the grinding wheel falls off severely and significantly shortens the life of the grinding wheel.

In order to prevent such abrasive grains from falling off, the grinding speed per abrasive grain can be reduced by reducing the feed speed of the grinding wheel or by reducing the rotation speed of the workpiece to a low level, for example, around 30 revolutions per minute. However, if the feed speed of the grinding wheel is reduced, the machining time of the workpiece will become longer, and grinding wheels with abrasive grains made of hard materials such as cubic shelmetide nitrides have low grinding resistance. Due to the small size of the workpiece, a method of reducing the rotational speed of the workpiece to about 30 revolutions per minute has been adopted because it does not cause competition between the workpieces even if the rotational speed of the workpiece is lowered.

However, if rough grinding is performed by rotating the workpiece at approximately 30 revolutions per minute, and then spark-out grinding or mill grinding is performed while the workpiece is rotating at the same speed, feed grinding is required due to the slow rotation speed of the workpiece. It takes a longer time to grind away the uncut parts that are left over from time to time than when machining with a conventional grinding wheel. In particular, when a large amount of uncut material is left on only a part of the machining surface (the side part of the cam), such as on a camshaft, the time required for spark-out grinding or fine grinding becomes significantly longer, and the workpiece is This method had the disadvantage that processing time could not be shortened. The present invention has been made to eliminate such drawbacks, and during fine grinding where the feed rate of the grinding wheel is low or during spark-out grinding where the feed rate is zero, the rotational speed of the workpiece is made higher than during rough grinding. It is characterized by cutting off uncut parts in a short time.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, reference numeral 1 denotes a bed, and a grindstone head 2 is mounted on the bed 1 so that it can move forward and backward toward the workpiece W. This grinding wheel head 2 rotatably supports a grinding wheel 20 in which abrasive grains made of a hard material such as cubic crystal nitride are bonded to the outer peripheral surface of a metal disk in a layered manner by bonding with resin or the like.
This grinding wheel is rotated by a motor 21 fixed on the grinding wheel head 2 via a pulley and a belt. On the other hand, as shown in FIG. 2, a feed screw shaft 23 is rotatably mounted on the bed, and a feed nut 24 fixed to the grindstone head 2 is screwed onto the feed screw shaft 23. This feed screw shaft 23 is connected to a servo motor 25 fixed to the bed 1.
The grindstone head 2 is moved forward and backward toward the workpiece W. A table 3 is movably placed on the bed 1 in a direction perpendicular to the direction of movement of the grindstone head 2, and is moved laterally using hydraulic cylinders provided at the bottom of the bed. A rocking table 31 is swingably supported on this table 3, and on the left side of this rocking table 31 are four mask cams M.
, ~M4 are rotatably supported on a main shaft 32 to which iron is attached. A workpiece W having four machining points C, -C4 corresponding to each master cam M, -M is placed between the center of the main spindle 32 and the tailstock 33 placed on the right end of the rocking table 31. The rotation is transmitted from the main shaft 32. Furthermore, the left end of the main shaft 32 is connected to a servo motor 34.
and a speed detector 35, and the main shaft 32 is rotated by a servo motor 34. And this main shaft 3
The rotational speed of 2 is detected by the speed detector 35. 3
6 is a headstock fixed on the table 3, and this headstock 3
6 has Mastercam M. A holder 38 that freely rotatably holds the follower roller 37 facing M4 is mounted so as to be movable in the direction of the main shaft axis.

The follower roller 37 is indexed to the front surface of the master cam corresponding to the machining location to be ground by an indexing mechanism (not shown) each time each machining location C, to C4 of the workpiece W is indexed to the grinding position. It has become. On the other hand, a protruding arm 31a is provided on the side surface of the rocking table 31 as shown in FIG.
A spring is tensioned between the oscillator 31 and the oscillator 31 to apply rotational force to the rocking table 31 in order to press the master cams M, to M4 against the follower rollers. Further, an arm 39 for attaching a limit switch is fixed to the holder 38 that holds the follower roller 37, and a limit switch LS5 is provided at the tip of the arm 39 to detect the rotation of the master cams M, to M4. ing.

Then, when the base circular portions of the master cams M, ~M4 come into contact with the follower roller 37, and the base portions of the machining locations C, ~C4 of the workpiece W are machined by the grinding wheel 201, the limit switch LS5 is activated by the master cams M, ~M4. It is pressed by the top of M4 and outputs a rotation signal RS. Next, a control circuit for automatically grinding each processing location C, to C4 of the workpiece W will be explained.

In FIG. 1, 4 gives a signal to a hydraulic circuit (not shown);
A table positioning circuit that indexes the table 3. When this table positioning circuit 4 receives a positioning command TPC along with a processing location number from the automatic processing circuit 5, it engages the dog D and take mitt switches LSI to LS4. As a result, the specified processing location is indexed to the front surface of the grinding wheel 20. Then, when the indexing is completed, the positioning completion signal TPF
Output. The automatic machining circuit 5 is a circuit for automatically grinding the machining points C, to C4, and when the start switch is pressed, it issues the machining point number C and a positioning command TP.
When the positioning completion signal TPF is given from the table positioning circuit 4, the grinding start signal GS is outputted to the feed control circuit 61.

Then, the grinding of the processing location C is completed, and the feed control circuit 6
When the grinding completion signal GF is given, a positioning command TPC is output together with the next machining location number C2, and four machining locations C, to C4 are sequentially machined. The feed control circuit 6 is a stored program type digital feed control circuit.
The grindstone head 2 is moved forward and backward in cycles according to various programs. When the grinding start signal CS is applied to the feed control circuit 6, the grinding cycle program is read out and executed. In this grinding cycle, after the grinding wheel head 2 is cut in the direction of the workpiece W by a distance corresponding to the amount of grinding at a preset rough grinding speed, a rough grinding completion signal FGF is output, and a counter described later is output. When the second spark-out completion signal SSOF is given from 80, the grinding wheel 2 is returned to the original position at a rapid forwarding speed. Then, when the grinding wheel 2 is returned to its original position, it outputs a grinding completion signal GF. The circuit constituted by the counter 70 and the setting device 71 is
The counter 70 is supplied with a rough grinding completion signal FGF from the feed control circuit 6. Then, counting of the rotation signal RS sent from the limit switch LS5 is started, and when the counted value becomes equal to the number set in the setting device 71, a count-up signal is output.

This count-up signal is applied to the counter 801 and is also applied to the servo motor control circuit 9, which will be described later, as a first spark-out completion signal FSOF. Note that the setting device 71 is set to the number of revolutions of the workpiece W, for example, 4, which is necessary to reduce the uncut portion generated during rough grinding to a permissible value or less by the first spark-out grinding. Further, a circuit constituted by a counter 80 and a setter 81 is used to determine the time for performing spark-out grinding (hereinafter referred to as second spark-out grinding) by rotating at a lower speed than during rough grinding. When the count-up signal is given, it starts counting the rotation signal RS, and when the count value becomes equal to the number set in the setter 81, it outputs the count-up signal.

This count-up signal is then given to the servo motor control circuit 9 and the feed control circuit 6 as a second spark-out completion signal SSOF. The setting device 81 is set to the number of rotations of the workpiece W, for example, 1 to 2, which is necessary to bring the machined surface accuracy of each machined location C, to C4 within the standard after the first spark-out grinding is completed. Ru.
When the number of revolutions of the workpiece is 1, it is not necessary to provide the counter 80 and the setting device 81, and one flip-flop can be used instead. The servo motor control circuit 9 is a circuit that changes the rotation speed of the workpiece W according to each grinding state, and when the grinding start signal GS is output from the automatic machining circuit 5 and rough grinding is started, the servo motor 34 is started. When the servo motor 3 is rotated at a medium speed, the rough grinding completion signal FGF is output from the feed control circuit 6, and the first spark-out grinding is started.
Rotate 4 at high speed.

Then, when the first spark-out grinding completion signal FSOF is output from the counter 70 and the second spark-out grinding is started, the servo motor 34 is rotated at a low speed, and the second spark-out completion signal SSOF is output from the counter 80. When the grinding is completed, the rotation of the servo motor 34 is stopped. This servo motor control circuit 9
The specific circuit has a configuration as shown in FIG. 3, and includes the grinding start signal CS, rough grinding completion signal FGF,
The spark-out completion signal FSOF is applied to set terminals S of flip-flops FF, -FF3, respectively.

Further, the second spark-out completion signal SSOF is applied to all the glue set terminals R of the flip-flops FF, -FF3. The output terminals Q of these flip-flops are input terminals 1 and 1 of the binary IQ Hayabusa decoder 91, respectively.
2 and 4, and when the grinding start signal CS is given and only the flip-flop FF is set,
A signal is output from the output terminal 1 of the decoder, and when the rough grinding completion signal FGF is given and the flip-flop FF2 is also set, a signal is output from the output terminal 3 of the decoder 91. In addition, the first spark out completion signal FSO
When F is given and all flip-flops FF, ~FF3 are set, a signal is output from the output terminal 7,
When the second spark-out completion signal SSOF is applied and all flip-flops FF, -FF3 are reset, the output of signals from the output terminals 1, 3, and 7 is stopped. VR, , VR2, and VR3 are variable resistors that set the rotational speed of the workpiece W in each grinding state, and the variable resistor VR
, is the rotational speed of the servo motor 34 during rough grinding,
That is, a speed command voltage VM corresponding to the rotational speed of the workpiece W during rough grinding, for example, 30 revolutions per minute, is set. Further, the variable resistor VR2 has a speed command voltage higher than the voltage set in the variable resistor VR, for example, a speed odd command voltage V corresponding to 60 revolutions per minute.
H is set, and variable resistor VR3 is set to variable resistor VR,
For example, a speed command voltage VL corresponding to 20 revolutions per minute is set. Then, the speed command voltages VM, VH, and VL set to these variable resistors VR, ~VR3 are applied to the gates ○, , , respectively.
The signal is supplied to the arithmetic unit 92 via G2 and G3. On the other hand, since the signals output from the output terminals 1, 3, and 7 of the decoder 91 are applied to these gates ○ and ~G3, respectively, the grinding start signal CS is applied to the servo motor control circuit 9. When the signal FGF is applied to the servo motor control circuit 9, the gate G2 is opened and the speed command voltage VH is applied to the calculation unit 92.
is given to the arithmetic unit 92. When the first spark-out completion signal FSOF is applied to the servo motor control circuit 9, the gate 3 is opened and the speed command voltage VL is applied to the calculator 92. Furthermore, when the second spark-out completion signal SSOF is applied to the servo motor control circuit 9, none of the gates is opened, and the speed command voltage is no longer applied to the calculator 92. This arithmetic unit 92 has a speed command voltage VM given through the gate G, ~○3,
It calculates the deviation between VH, VL and the speed feedback voltage F fluctuation output from the speed detector 35 connected to the servo motor 34, and this deviation is given to the calculation unit 93 via the amplifier A. It looks like this.

Further, the arithmetic unit 93 calculates the deviation between the given deviation signal and the current feedback voltage detected by the resistor RC, and this calculated deviation is sent to the driving device 9 through an amplifier.
It is designed to be given to 4. This drive circuit 94 changes, for example, the firing phase angle of the thyristor based on the applied deviation signal, controls the voltage applied to the servo motor 34, and controls the rotational speed of the servo motor. Therefore, when the speed command voltages VM, VH, VL are applied to the calculator 92, the servo motor 34 starts rotating, and the rotation speed deviates from the set speed, causing the speed command voltages VM, VL to start rotating.
If a deviation occurs between H, VL and the eastern feedback voltage F, this deviation is amplified by amplifiers A, A2,
The servo motor 34 is pulled back to the set speed. As a result, the servo motor 34 rotates accurately at a speed selected from among the speeds set in the variable resistors VR, to VR3.
Next, the operation of this embodiment with the above configuration will be explained.

Now, when the start switch of the automatic machining circuit 5 is pressed while the workpiece W is held between the center of the spindle 32 and the center of the tailstock 33, the automatic machining circuit 5 sends the machining location number 1 and A positioning command TPC is output and given to the table positioning circuit 4. This results in table 3
is indexed to the position shown in FIG. When the indexing of the table 3 is completed in this way, a positioning completion signal TPF is given to the automatic processing circuit 5, and the automatic processing circuit 5 outputs a grinding start signal OS. As described above, this grinding start signal GS is given to the feed control circuit 6 and the servo motor control circuit 9, and when the grinding start signal GS is given to the servo motor control circuit 9, the flip-flop FF is set. , a signal is output from the output terminal 1 of the decoder 91. Decoder 9
When a signal is output from the output terminal 1 of 1, the gate G is opened, so the speed command voltage VM set in the variable resistor VR is given to the calculator 92, and the servo motor 34 receives the speed command voltage VM. Rotates at a speed corresponding to As a result, the workpiece W is rotated at a medium speed of 30 revolutions per minute, as shown in FIG. On the other hand, when the grinding start signal GS is given to the feed control circuit 6, the grinding cycle starts. In order to read out the grinding wheel 2, the grinding wheel 2 is advanced at a relatively high preset infeed rate, for example 8 willows per minute. As a result, the processing location C is ground by the grinding wheel 20' while following the profile of the master cam M. At this time, the grinding wheel 20 cuts at a relatively high speed, but since the rotational speed of the workpiece W is as low as 30 revolutions per minute, the amount of grinding per abrasive grain is small, and unreasonable force is applied to the abrasive grain. It will not fall off. Then, when the grinding wheel 2 is advanced by a preset distance and the processing location C is ground to a predetermined dimension, the advancement of the grinding wheel 2 is stopped, and the rough grinding completion signal FGF is output from the feed control circuit 6. and the first spark-out grinding is started.

This rough grinding completion signal FGF is given to the counter 70 and the servo motor control circuit 9, and when the rough grinding completion signal FGF is given to the servo motor control circuit 9, flip-flop FF2 is also set. As a result, a signal is output from the output terminal 3 of the decoder 91, so that the gate G2 is opened instead of the gate S. When the gate ○2 is opened, the speed command voltage VH set in the variable resistor VR2 is applied to the arithmetic unit 92, and the servo motor 34 is rotated at a speed according to the speed command voltage VH. As a result, the workpiece W is rotated at a speed of 60 revolutions per minute as shown in FIG. 4, and the uncut parts left during rough grinding are ground away in a short time. In this case, the rotational speed of the workpiece is a long 60 revolutions per minute, but since the depth of cut of the grinding wheel 20 is zero, the amount of grinding per abrasive grain does not increase, and no abrasive grains fall off. do not have. On the other hand, when the counter 70 receives the rough grinding completion signal FGF from the feed control circuit 6, it counts the rotational speed RS that is generated every time the master cam M, rotates once, and the counted value is equal to 4 set in the setting device 71. Since the count-up signal is sent out when the workpiece W rotates four times after the first spark-out grinding starts as described above, the counter 7
A count up signal is output from 0.

As described above, this count-up signal is sent to the servo motor control circuit 9 as the first spark-out completion signal FSOF.
Therefore, when the counter 70 counts up, flip-flop FF3 is set. As a result, a signal is output from the output terminal 7 of the decoder 91, so that the gate G3 is opened instead of the gate G2, and the speed command voltage VL set in the variable resistor VR3 is applied to the calculator 92. As a result, the workpiece W is rotated at a slow speed of 20 revolutions per minute, and the second spark-out grinding is performed. When the second spark-out grinding is performed, the roughness of the machined surface caused by the first spark-out is removed, and the precision of the machined surface becomes within the standard. Further, the counter 80 counts the rotation signal RS when the second spark-out grinding for which the counter 70 has counted up is started, and when the counted value reaches the number of times set in the setting device 81, for example, 2, the counter 80 counts up. Since a signal is output, when the second spark-out grinding is started and the workpiece rotates twice, the counter 80 outputs a count-up signal.

When the count-up signal is output from this counter 80, the second spark-out completion signal SSOF is given to the servo motor control circuit 9, so that the flip-flop FF
, ~FF3 are all reset.

As a result, no signals are output from the output terminals 1, 3, and 7 of the decoder 91, and the gate G3 is closed. Therefore, the calculation unit 92 has speed command voltages VM, VH, VL.
is no longer applied, and the rotation of the servo motor 34 is stopped. At the same time, the second spark-out completion signal SSOF is also given to the feed control circuit 6, so that
The grindstone head 2 is returned to its original position at a rapid traverse speed. When the grinding of the processing location C is completed in the manner described above, the feed control circuit 6 outputs the grinding completion signal GF. As a result, the automatic machining circuit 5 outputs the positioning command TPC along with the next machining location number 2, and the machining locations C2 to C4 are sequentially machined. As described above, in this embodiment, after the rough grinding is completed, spark-out grinding is performed by increasing the rotational speed of the workpiece compared to the rough grinding, and furthermore, after the spark-out grinding is completed, the workpiece is Spark-out grinding is performed by lowering the rotational speed of the grinder than during rough grinding, but the present invention can be applied to grinding cycles other than those of the above-described embodiments. Figures 5 and 6 show an example.
In the grinding cycle shown in the figure, rough grinding is performed while the workpiece is rotated at a medium speed, and after this rough grinding is completed, spark-out grinding is performed while the workpiece is rotated at a higher speed than during rough grinding. After the grinding is completed, fine grinding and spark out are performed. Therefore, in this case, the uncut parts left during rough grinding are ground in a short time by the spark-out grinding that follows rough grinding.
The time for grinding can be significantly reduced. In addition, in the grinding cycle shown in Figure 6, the rotation speed of the workpiece is increased during fine grinding when the grinding wheel feeds slowly, so the time for fine grinding can be shortened in this case as well. be able to.

As described above, in the cam grinding method of the present invention, the rotational speed of the workpiece is made higher than during rough grinding during fine grinding where the feed rate of the grinding wheel is low or during spark-out grinding where the feed rate is zero. Since the grinding is performed using a grinding method, the time required for chamfer grinding or spark-out grinding can be shortened without deteriorating the cam profile accuracy and machined surface accuracy, which has the advantage of shortening the total machining time of the workpiece.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cam grinding device according to the present invention, FIG. 2 is an enlarged partial cross-sectional view of FIG. 1 viewed from the 0 direction, and FIG. FIG. 4 is a diagram showing a grinding cycle of the cam grinding device shown in FIG. 1, FIG. 5 is a second embodiment of the grinding cycle according to the present invention, and FIG. 6 is a third embodiment thereof. This is an example. 1...Bed, 2...Whetstone stand, 3...
Taffle, 6...Feed control circuit, 9...Servo motor control circuit, 20...Grinding wheel, 25, 34...
... Servo motor, 31 ... Rocking table, 32
...Main shaft, 35...Speed detector, 37
...Fuoro roller, 70, 80... Force counter, 91... Decoder, 92, 93... Arithmetic unit, 94
......Driver, A,,A2...Amplifier, C
, ~C4... Machining location, FF, ~FF3...
・Flip-flop, G, ~G3...Gate, VR
,~VR3...Variable resistor, W...Workpiece. Figure 1, Figure 2, Figure 3, Figure 4, Figure ○, Figure ○.

Claims (1)

[Claims] 1. A main shaft rotatably supported on a rocking table is rotated by a drive device, and a master cam fitted on the main shaft is brought into pressure contact with a follower roller. In a cam grinding method, a cam of the workpiece is ground by swinging it according to the profile of the workpiece and sending a grinding wheel having abrasive grains of a hard material such as cubic boron nitride to the workpiece attached to the main shaft, The workpiece is rotated at a predetermined rotational speed and the grinding wheel is fed at a predetermined feed rate to roughly grind the cam of the workpiece, and then the workpiece is rotated at a speed faster than the rotational speed. . A cam grinding method, characterized in that the cam of the workpiece is machined by feeding the grinding wheel at a speed equal to or lower than the feeding speed, or by cutting the cam of the workpiece at zero feeding.