JPS6156064B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a numerically controlled cam grinding machine that numerically processes a plurality of cams formed on a workpiece with different phases, and its purpose is to index the rotation of a workpiece. The purpose of this invention is to shorten the machining time of a workpiece by making it possible to machining cams with different phases continuously without having to perform the following steps.

Generally, a camshaft used in an internal combustion engine is provided with a large number of cams that have the same profile but differ only in phase. For this reason, in conventional numerically controlled cam grinding machines that grind camshafts, the workpiece is rotated each time machining of each cam is completed so that machining of the cams always starts from the same phase. For this purpose, cams can be machined using common profile data.

In this way, the storage area required to store profile data can be significantly reduced compared to the case where profile data is stored for each cam. However, when machining a camshaft using this method, Each time the process is completed, the camshaft must be rotated to determine the phase of the cam, which has the disadvantage of prolonging the machining time.

The present invention has been made in view of these conventional drawbacks, and each time the cam to be machined is changed, the position of the profile data readout start point is changed according to the phase of the cam to be machined next, and the next cam is changed. The present invention is characterized in that the position of the grindstone processing surface is corrected in accordance with the commanded lift amount of the grindstone processing surface at the processing start point of the cam.

Embodiments of the present invention will be described below based on the drawings. In Figure 1, 10 is the bed of the grinding machine, 11
is a work table placed on bed 10,
This work table 10 is moved by a motor 12 in the direction of the workpiece axis.

On this work table 11 is a servo motor 1.
A headstock 16 that supports a main shaft 15 rotated by a spindle 4, and a tailstock 18 that supports a tailstock center 17.
The main spindle 15 has a main spindle center 1 which clamps the workpiece W between it and the tailstock center 17.
9, and a phasing key 2 for phasing the workpiece W.
0 is provided. Further, an origin detector 21 for detecting the rotation origin (C-axis origin) of the spindle 15 is attached to the rear of the headstock 16, and as shown in FIG. center
The origin signal CZS is output at a phase angle that passes through OG.

The workpiece W is provided with four cams: a first intake cam I1, a first exhaust cam E1, a second intake cam I2, and a second exhaust cam E2. These cams I1
~E2, as shown in FIGS. 3a to 3d, have the same profile and differ only in phase.

On the other hand, behind the bed 11, a grindstone stand 24 that supports a grindstone G rotated by a motor 23 is placed so as to be movable in the X-axis direction perpendicular to the workpiece axis. It is starting to be moved. As a result, the machining surface of the grindstone G
Ga is cut into the workpiece W side along the X axis.

Next, four cams I1 to E formed on the workpiece W
A control device for automatically processing 2 will be explained.

Numeral 30 is a numerical control device that controls the rotation of the workpiece W and the feed of the grindstone head 24 by distributing pulses to the drive units 26 and 27 for driving the servo motors 14 and 25, and is composed of a computer. Also, 31
is an indexing control circuit that controls the rotation of the motor 12 to position the work table 11 and index the cams I1 to E2 to processing positions in order;
When the number of the cam to be machined next is output from 0,
The work table 11 is moved until the limit switch corresponding to the cam to be machined among the limit switches LS1 to LS4 is activated, and the designated cam is indexed to the machining position.

Note that 32 is a dog that is attached to the work table 11 and selectively operates the limit switches LS1 to LS4.

For example, in the state shown in FIG.
When a signal designating the indexing of the first exhaust cam E1 is output from
2 and turn the limit switch with dog 32.
When LS2 is activated, the motor 12 is stopped, thereby indexing the first exhaust cam E1 to a position facing the grindstone G.

The numerical control device 30 is connected to a tape reader TR for reading profile data programmed onto the paper tape T, and digital switches DS0 to DS7 for setting data necessary for processing. is read and data is set to digital switches DS0 to DS7.

The profile data programmed on the paper tape T is for each block as shown in Figure 4.
The amount of movement of the grinding wheel G while the cam rotates by a unit angle is programmed, and the first block has the amount per unit angle at the reference angular position where the center OB of the cam base is the grinding point, as shown in Figure 5. The amount of movement (usually zero) is programmed, and block 1
Thereafter, the amount of movement at the angular position where the cam has rotated counterclockwise by a predetermined amount from the reference angular position is programmed.

On the other hand, the digital switches DS0 to DS7 contain data on the rapid feed amount RO and total depth of cut RT of the grinding wheel G, the rapid feed speed FO of the grinding wheel G, and the depth of cut △R per unit angle rotation, as well as data on each cam I1 to E2. phase angle α1~α4
data is set. As the data for the phase angles α1 to α4, the deviation angles of the center OB of the base portion of each cam with respect to the center of the keyway are set as shown in FIGS. 3a to 3d. In addition, the unit angle is △ between the total cutting depth RT of the grindstone G and the cutting depth △R per unit angle rotation.
When θ is assumed, the data is set so that the relationship RT=(360/Δθ)×ΔR×n (n is a natural number) holds. As a result, the machining start point and the machining completion point coincide, as will be described later.

When the numerical control device 30 starts operating, it first performs a process for returning the main shaft 15 to its origin, as shown in the flowchart of FIG. That is, in step 10, the numerical control device 30 sends out positive or negative pulses to the drive unit 27 to rotate the main shaft 15 until the origin signal CZS is sent from the origin detector 21, and when the origin signal CZS is sent out. Stop dispensing pulses. As a result, the workpiece W
is indexed to the reference phase shown in FIG.

When the return to the origin of the spindle 15 is completed in this way, the numerical control device 30 sets the cam designation counter CDC to 1 in step 11, and then returns to step 1.
2, the indexing circuit 31 is commanded to index the cam. When the count value of the cam designation counter CDC is 1, a signal instructing indexing of the first intake cam I1 is given to the indexing control circuit 31, and the first intake cam I1 is indexed to the processing position. At this time, the first intake cam I1 is in the phase state shown in Fig. 3a, so if machining is started without indexing the rotation of the workpiece W, the grinding start point will be shifted clockwise by α1 from the center OB of the base part. Be in position. Therefore, in order to start machining the first intake cam I1 without rotationally indexing the workpiece W, it is necessary to shift the profile data reading start point by an amount corresponding to α1.

In addition, the rapid forward end position of the grinding wheel processing surface and the forward end position of the grinding wheel processing surface at the time of completion of processing are programmed based on the base circle, so if the grinding start point is shifted from the base part, the grinding wheel processing If the position of the surface is not corrected, not only will the grinding surface run into the cam surface at a rapid traverse speed, but it will also become impossible to obtain the desired finished dimensions.

Step 13 is a step for correcting the reading start point of the profile data and the position of the grinding surface, the details of which are shown in the flowchart of FIG. Steps 20 and 21 are preparation routines,
In step 20, the register R1 for storing the correction amount is reset to zero, and in step 21, the phase angle αn of the cam to be machined is read. In this case, the first intake cam I1
The phase angle α1 is read from the digital switch DS4.

Steps 22 to 27 are routines for changing the reading start point and calculating the corrected movement amount of the grinding surface, in which profile data is accumulated and the read counter ROC is repeatedly incremented. At the start of operation, the read counter ROC
Since the count value of block 0 has become zero, the profile data from block zero is read out in order and accumulated in register R1. When the data up to the α1-1 block has been accumulated, this is determined in step 27, the accumulation operation is stopped, and the process moves to step 28. At this time, the cumulative value of the profile data from block zero to block α1-1 is stored in the register R1, and this becomes the corrected movement amount of the grindstone processing surface. This corrected movement amount is equal to the commanded lift amount at the machining start point based on the base circle. In addition, due to this profile data accumulation operation, the count value of the read counter is corrected to α1-1, so that the profile data read position at the start of machining corresponds to the actual machining start point as described later. become.

Step 28 is a step for correcting the position of the grindstone processing surface Ga, and distributes positive or negative pulses to the X-axis according to the corrected movement amount stored in the register R1. Assuming that the commanded lift amount at the start of machining of the first intake cam I1 is l1 as shown in FIG. 9, the number of positive pulses corresponding to this l1 is
The grinding wheel processing surface Ga is retracted by l1 as shown in FIG.

When the position correction of the grindstone surface is completed in this way, this is determined in step 29, and the process returns to the main control routine shown in FIG. As a result, the grinding wheel G is rapidly advanced in step 14, and when this is completed, the process moves to step 15 and machining of the cam is started. The feed amount in the rapid traverse process is set so that it stops just before the grinding wheel processing surface Ga touches the base part at the rapid traverse forward end position.
Since Ga is moved back by l1, not only is the grinding wheel processing surface Ga prevented from hitting the cam surface during rapid traverse, but also the grinding wheel processing surface Ga is prevented even if profile data reading is started from an intermediate block. The cam can be moved forward and backward at the correct position, and the cam can be machined to the correct dimensions.

FIG. 8 shows an example of a control routine for performing a generating motion of the cam, and shows steps 30 to 3.
After performing the preparation process necessary for pulse distribution in step 2, the process moves to the pulse distribution routine from step 33 onwards. When proceeding to step 33, the read counter
The profile data Xn specified by ROC is read, but in step 32 of the preparation routine, the count value of the read counter ROC is incremented, and the count value becomes α1.
Therefore, the α1-th profile data is read out first.

When the reading of the profile data is completed, the depth of cut F per unit angle is added to the profile data Xn read in step 34, and the amount of movement Lg of the grindstone G while the cam rotates by a unit angle is determined. After this,
Proceeding to step 35, pulses are distributed simultaneously to the C-axis and the X-axis in order to rotate the cam by a unit angle and simultaneously move the grindstone G by the amount of movement Lg.

Then, when the pulse distribution is completed, step 3
7, the total depth of cut is determined in step 30 of the preparation routine.
RT subtracts the depth of cut per unit angle from the preset movement counter MVC, and the process proceeds to step 38.
Then, it is determined whether the count value of the movement amount counter MVC has reached zero.

If the value has reached zero, the process returns to the main control routine and stops the generating motion of the cam, but if it is not zero, the read counter ROC is incremented in step 39, and then the process returns to step 40 and 41. 3
3, pulse distribution is performed again in the same manner as in the previous case. By repeating such an operation, the grindstone G gradually makes a cut while repeating forward and backward movements, and the first intake cam I1 is machined into a desired shape.

Total depth of cut set on digital switch DS2
When the grindstone G is cut by RT, the movement counter
Since the count value of MVC becomes zero, this is determined in step 38, the control for cam creation is completed, and the process returns to the main control routine. As a result, the pulse distribution to the C-axis is stopped, and the rotation of the workpiece W is stopped. However, since the cutting of the grindstone G is programmed to be completed at the same position as the phase at the start of machining, when machining is completed. The phase of the first intake cam I1 at is the phase shown in FIG. 3a. Also, the count value of the read counter ROC after machining is completed is α1
becomes.

Returning to the main control routine, in step 16 the grinding wheel G is
is retreated to the retreat end at a rapid traverse speed, completing the machining of the first intake cam I1. When the cam machining operation is completed in this way, it is determined in step 17 whether all the cams have been machined, but in this case, only the first intake cam I1 has been machined, so the cam designation is performed in step 18. The counter CDC is incremented and the process returns to step 12.

As a result, the first exhaust cam E1 is indexed to the machining position, and the cam is machined after changing the profile data reading start point and correcting the position of the grinding surface, as in the case described above.

The phase angle of the first exhaust cam E1 is the first intake cam I
Since the phase angle α2 is larger than the phase angle α1 of
The profile data up to 1 is accumulated as the corrected movement amount of the grinding wheel machining surface, and the profile data reading start point is changed from α1 block to α2 block, and machining is started. 1st exhaust cam E
Since the machining start position of No. 1 is the base circular portion, the cumulative value of the profile data is a negative value of the command lift amount 1 at the machining completion point of the first intake cam I1.
Therefore, the grindstone G is advanced by l1, and the processing start position of the grindstone processing surface Ga is corrected to the correct position, and processing is performed.

When the machining of the first exhaust cam E1 is completed, the second intake cam I2 is subsequently indexed to a machining position and machining is performed. Phase angle α3 of second intake cam I2
is smaller than the phase angle α2 of the first exhaust cam E1, so the profile data from α2 to 3599 block and the profile data from 0 to α3 block are accumulated continuously to change the reading start position and change the grinding surface of the grinding wheel. A correction movement amount is calculated.
In this case, like the first exhaust cam E1, the base portion becomes the machining start point, so the cumulative value becomes zero and the position of the grindstone machining surface Ga is not corrected.

Subsequently, the second exhaust cam E2 is machined, but in this case as well, the base circle is the starting point for machining, so the position of the grinding wheel machining surface Ga is not corrected, and only the reading start point is the second exhaust cam E2. The position is changed according to the phase angle α4 of E2.

When the machining of the cam is completed in this way, the grindstone G and work table 11 are returned to their original positions, and the machining is completed.

In addition, if you program the finger cool lift amount of the grinding wheel machining surface at each rotation angle position of the cam as profile data, the profile data corresponding to the machining completion point of the previous cam and the machining start point of the next cam can be programmed. The corrected movement amount of the grinding wheel surface can be determined by simply determining the deviation of the corresponding profile data.

Furthermore, the present invention can be applied even when the intake cam and exhaust cam have different profiles. If only the finished diameter of the base circular portion differs, the feed amount during rapid traverse or grinding may be changed depending on the cam, and if the profiles are completely different, two sets of profile data may be stored. The profile data to be read may be changed depending on the cam to be processed.

As described above, in the present invention, prior to machining a cam, the reading start point of profile data is changed according to the position of the machining start point of the next cam to be machined, and Since the position of the grinding wheel machining surface is corrected according to the commanded lift amount, no matter where the machining start point of the next cam to be machined is, machining can be performed without having to index the rotation of the workpiece. This eliminates the need to index the rotation of the workpiece each time cam machining is completed, which was required in the past, and significantly reduces the machining time for workpieces such as camshafts that have multiple cams with the same profile but different phases. It has the advantage that it can be shortened to

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a schematic plan view of a grinding machine with an electric circuit diagram;
Figure 2 shows the reference phase of the workpiece, Figure 3 a~
d is a diagram showing the phase of each cam, FIG. 4 is a diagram of a program sheet showing profile data, and FIG. 5 is a diagram showing the program start position of profile data.
Figures 6 to 8 are flowcharts showing the operation of the numerical control device, Figure 9 is a diagram showing the commanded lift amount at the machining start point of the first intake cam I1, and Figure 10 is a diagram showing the movement locus of the grinding wheel machining surface. FIG. 10...Bed, 11...Slide table,
14, 25... Servo motor, 16... Headstock,
18...Tailstock, 24...Whetstone head, 26, 27...
...Drive unit, 30...Numerical control device,
31... Index control circuit, 22-27... Step for changing the reading start point of profile data and calculating the correction amount for the grinding wheel processing surface, 28... Step for correcting the position of the grinding wheel processing surface, DS0-DS7... ...Digital switch, G... Grindstone, TR... Tape reader, W... Workpiece.

Claims (1)

[Claims] 1 Rotate the workpiece at a predetermined speed and
One cam is machined in a numerically controlled cam grinding machine equipped with a control device that processes a cam formed on a workpiece into a desired shape by controlling the feed of the grinding wheel based on profile data stored in a storage device. an indexing means that indexes a cam with a different phase to a position facing the grinding surface by moving the work table in a direction parallel to the workpiece axis, and a new cam is machined by this indexing means. readout point changing means for changing the readout start point of profile data according to the machining start point of a new cam each time the cam is indexed to a new position; A numerically controlled cam grinding machine comprising: a position correction means for correcting the position of a grindstone processing surface according to a commanded lift amount of the grindstone processing surface at a processing start point.