JP2892407B2 - Cam grinding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application field] The present invention stores one or more intermediate shape data in addition to the final shape data of a cam, and performs a numerically controlled grinding process on a work according to these data. It relates to a cam grinding method.

2. Description of the Related Art A method of grinding a cam using a grindstone made of hard material such as cubic boron nitride using numerical control data programmed in advance has been widely performed.

In this case, in order to shorten the processing time of the cam, for example, after performing rough grinding by rotating the work at a predetermined rotation speed, the work is rotated at a speed higher than the rotation speed to finish grinding and finish grinding. A method of performing spark-out grinding (see Japanese Patent Publication No. 60-10865), a method in which the work and the grindstone are relatively displaced along with the cam shape data, and the work (Japanese Patent Application Laid-Open No. 54-68)
No. 589) has been proposed.

[Problems to be Solved by the Invention] However, as shown in FIG. 5, the substantially planar cam side portions 8a and 8b are provided between the top circular portion 4 and the base circular portion 4 where the cam 2 is a perfect circular portion. To have a cylindrical material S
When the cam 2 is processed by the above-described conventional technique while rotating the wheel, the grinding speed of the grinding wheel becomes remarkable because the peripheral speed of the cam side portions 8a and 8b is particularly large. Accordingly, the rotational speed of the material S in the base circle portion 4 is considerably reduced (substantially at a speed ratio of approximately 1/16) with respect to the rotational speed of the material S in the cam side portions 8a and 8b so that the cam 2 is processed. (See Japanese Patent Publication No. 60-14668), however, it is difficult to reduce the machining time of the entire cam 2 at a stroke.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cam grinding method capable of reducing the wear of a grindstone as much as possible and efficiently performing a working operation of the entire cam.

Means for Solving the Problems In order to solve the above problems, the present invention provides a cam grinding method for processing a cam having a cam side portion between a base circle portion which is a perfect circle portion and a top portion. A step of storing final shape data corresponding to a desired cam shape and one or more intermediate shape data different from the final shape data; and performing rough grinding on the workpiece along the intermediate shape data. A process of processing a portion corresponding to the cam side portion of the workpiece into a shape that curves outward from the cam side portion of the final shape; and changing the intermediate shape data to the final shape data to finish the workpiece. Performing a grinding process.

[Operation] In the cam grinding method according to the present invention, after rough grinding is performed along the intermediate shape data, finish grinding is performed according to the final shape data, so that the portion corresponding to the cam side portion and the base circle portion are processed. The speed ratio with respect to the part to be ground can be made relatively small, and wear of the grindstone can be prevented as much as possible, so that high-precision cam grinding is performed.

Examples Next, examples of the cam grinding method according to the present invention will be described with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a grinding apparatus for performing the cam grinding method according to the present embodiment. This grinding machine
The moving table 12 constituting the unit 10 can move forward and backward in the arrow Z direction via a ball screw (not shown) connected to the servomotor 14. A main shaft 18 and a support base 20, which are rotationally driven in the direction of arrow C by the servo motor 16, are arranged on the moving table 12 so as to face each other, and the work W is held at both ends by the support shaft 18 and the support base 20.

The grindstone base 22 is movable back and forth in the direction of arrow X via a servomotor 24, and a disc-shaped grindstone 28 rotationally driven by a motor 26 is disposed on the grindstone base 22. This whetstone 28
Substantially cubic boron nitride abrasive grains are included.

Each servomotor 14, 16 and 24 has an encoder 32
a, 32b and 32c are connected and this encoder 32a
To 32c are input to the comparison circuits 34a to 34c. In the comparison circuits 34a to 34c, the speed and the position of the work W in the Z direction based on the signal input from the encoder 32a, and the speed and the angular position of the work W in the direction of the arrow C by the signal from the encoder 32b are changed from the encoder 32c. , The speed and the position of the grinding wheel 28 in the direction of the arrow X are calculated. As a result, the comparison circuits 34a to 34c drive and control the servo motors 14, 16, and 24, and input and output signals to and from the control circuit 36.

The control circuit 36 outputs a signal between the CPU 38 that performs substantial arithmetic processing, a ROM 40 that stores a predetermined program and the like, a RAM 42 that temporarily stores data, and an external device. It has an I / O port 44 for inputting.

The ROM 40 includes cam profile data D1 relating to the radius of the base circle portion 4 of the cam 2, the angles of the cam side portions 8a and 8b, the machining position, and the like shown in FIG.
Processing means data D2 such as a minimum setting unit and origin coordinates, and processing condition data D3 such as the shape of the workpiece W, final shape data of the cam 2, and one or more intermediate shape data are stored in advance.

The data D3 will be described in detail with reference to FIG. 2. In FIG. 2, a work W indicated by a two-dot chain line is formed into a shape substantially similar to the cam 2 by casting, and the final shape of the cam 2 is shown.
The final shape data corresponding to the FS is stored. An intermediate shape MS is set between the final shape FS and the outer peripheral shape of the work W, and this is stored as intermediate shape data. In the intermediate shape MS, a portion corresponding to the base circular portion 4 and the top portion 6 of the cam 2 has substantially the same shape, while a portion corresponding to the cam side portions 8a and 8b has an outwardly curved thick portion 50.
a and 50b are provided.

It should be noted that another intermediate shape may be added between the final shape FS and the intermediate shape MS and / or between the intermediate shape MS and the outer peripheral shape of the workpiece W. In this case, the intermediate shape corresponds to the cam side portions 8a and 8b. Select the part to be curved outward.

The grinding apparatus for carrying out the cam grinding method according to the present embodiment is configured as described above. Next, the operation thereof will be described below with reference to the flowchart shown in FIG.

First, after reading each data D1, D2 and D3 stored in the ROM 40 in advance (STP1), the drive signals Sa are sent to the comparison circuits 34b and 34c based on the intermediate shape data of the intermediate shape MS.
1. Send S'a1 (STP2). These drive signals Sa1, S '
The comparison circuits 34b and 34c drive and control the servo motors 16 and 24 via a1, and the grindstones are rotationally driven under the action of the motor 26.
According to 28, the workpiece W is roughly ground under the conditions shown in Pattern 1 (see FIG. 4A).

That is, in the present embodiment, the thick portion 50 that curves outwardly is provided at a portion corresponding to the desired cam side portions 8a and 8b of the cam 2.
Since the rough grinding is performed along the intermediate shape MS provided with a and 50b, the peripheral speed does not differ so much between the thick portions 50a and 50b and the portion corresponding to the base circular portion 4. For this reason, the rotation speed N1 during the grinding of the thick portions 50a and 50b is substantially changed to the rotation speed during the grinding of the portions corresponding to the base circular portion 4 and the top portion 6.
Even if the speed ratio of the value divided by N2 is controlled to about 1/2 to 1/3, the grinding resistance at the thick portions 50a and 50b does not increase. As a result, it is possible to prevent wear of the grindstone 28 as much as possible, and to obtain an effect that the number of times of truing is reduced and an efficient grinding work can be performed.

Based on the signal Sc relating to the angular position of the work W input from the comparison circuit 34b and the signal S'c relating to the position of the grindstone 28 in the direction of the arrow X input from the comparison circuit 34c.
Is detected as an intermediate shape MS (STP3, ST
P4).

After the workpiece W has the intermediate shape MS, the control circuit 36 sends the drive signals Sa2,
S'a2 is transmitted (STEP5). Therefore, pattern 2
The work W is subjected to finish grinding and spark-out grinding along the line (see FIG. 4B). Here, the speed ratio of a value obtained by dividing the rotation speed N3 at the time of grinding the thick portions 50a and 50b by the rotation speed N4 at the time of grinding the portions corresponding to the base circular portion 4 and the top portion 6 is from 1/4. It is controlled to be about 1/6.

That is, since the intermediate shape MS is provided with thickened portions 50a, 50b that are curved outward at portions corresponding to the cam side portions 8a, 8b, the rough shape is required to reliably remove the thickened portions 50a, 50b. The speed ratio is set higher than during grinding.
At this time, rough grinding, finish grinding and spark-out grinding are performed by the same grindstone 28. However, in order to significantly reduce the wear of the grindstone 28 during the rough grinding, the finish grinding along the pattern 2 is performed. Machining and spark-out grinding are performed in a short time and with high precision.

After the work W has the final shape FS (STP6, STP7), the grindstone 28 is separated from the side surface of the work W after processing. If all the cams 2 of the work W have not been processed, the control circuit 36 sends a drive signal Sb to the comparison circuit 34a (STP
8, STP9). For this reason, after the servo motor 14 is driven and the moving table 12 moves in the direction of the arrow Z and the next processing portion of the work W reaches the position corresponding to the grindstone 28, the operation from step 2 is performed sequentially.

[Effects of the Invention] As described above, the cam grinding method according to the present invention has the following effects and advantages.

Since the work is roughly ground based on one or more intermediate shape data in addition to the final shape data corresponding to the desired cam shape, the grinding speed ratio at each part of the work can be made as small as possible. Therefore, the efficiency of the entire grinding operation can be improved, and the wear of the grindstone can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a grinding apparatus for performing a cam grinding method according to the present invention, FIG. 2 is an explanatory view of the cam grinding method, FIG. 3 is a flowchart of the cam grinding method, and FIG. FIG. 5 is an explanatory diagram of a grinding process and a finish grinding process. FIG. 5 is an explanatory diagram of each part of a general cam. 2 ... Cam, 4 ... Base circle part 6 ... Top part 8a, 8b ... Cam side part 10 ... Grinding device 14, 16, 24 ... Servo motor 28 ... Whetstone 32a-32c ... Encoder 34a-34c …… Comparison circuit 36 …… Control circuit, W …… Work

Claims (2)

(57) [Claims] 1. A cam grinding method for machining a cam having a cam side portion between a base circle portion and a top portion, which is a perfect circle portion, comprising: a final shape data corresponding to a desired cam shape; A step of storing one or more intermediate shape data different from the final shape data, and performing a rough grinding process on the work along the intermediate shape data to form a portion corresponding to the cam side portion of the work into a final shape. A process of machining the workpiece into a shape that curves outward from the cam side portion, and a step of performing finish grinding on the workpiece by changing the intermediate shape data to the final shape data. . 2. The method according to claim 1, wherein the change from the intermediate shape data to the final shape data is performed on the base circle portion.