JP4366337B2 - Method for grinding a cam having a three-dimensional curved surface - Google Patents

Description

  The present invention relates to a method for grinding a cam having a three-dimensional curved surface.

  Generally, a cam formed on a camshaft used for an intake valve mechanism or an exhaust valve mechanism of an automobile engine is formed by a base circle portion, a lift portion, and a cam top portion, and the lift in the direction of the central axis of the camshaft. The cross-sectional shapes of the part and the cam top part are the same in every part. Instead of this camshaft, the cam has a three-dimensional curved surface in which the sectional shapes of the cam lift and cam top continuously change in the direction of the central axis in order to improve characteristics such as fuel efficiency and output of the engine. A shaft was used.

In the former camshaft cam grinding method, the camshaft mounted on the main shaft device is rotated, and one cam of this camshaft is controlled to move in the direction of the central axis based on one profile data created in advance. The first grinding is performed with the grindstone, and then the grindstone is relatively moved in the direction of the central axis, the next grinding is performed with the same profile data, and this operation can be sequentially repeated. However, in the cam grinding of the latter camshaft, since the lift part and the cam top part continuously change in the central axis direction, each of them corresponds to a curved surface shape of a large number of virtual cross sections orthogonal to the central axis direction. For example, 200 different profile data are created, and the many profile data are sequentially used to grind the cam in the central axis direction intermittently. In addition, a method has also been proposed in which the camshaft is rotated and moved in the direction of the central axis thereof, and the grinding stone is spirally brought into contact with the three-dimensional curved surface of the cam to perform grinding. (See paragraph number 0029 of Patent Document 1)
Japanese Patent Laid-Open No. 2005-14171

  However, the former grinding method of the three-dimensional cam is that once the cam is ground with one profile data, the grindstone is retracted from the cam and the grindstone is moved to the next grinding work position in the direction of the center axis of the camshaft. During this time, the profile data is replaced with the next profile data, and the cam is ground. Therefore, there is a problem that the efficiency of the grinding work is lowered.

  Further, the latter grinding method of the three-dimensional cam grinds with a grindstone spirally contacting the outer surface of the cam, so that grinding work can be continuously performed with one profile data. Since very troublesome spiral profile data has to be created, the creation time becomes long, and there is a problem that the cost of creating software cannot be reduced. In addition, the latter grinding method has a problem that it is difficult to partially correct the profile data because the profile data is continuously created so as to be spirally ground.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a cam grinding method having a three-dimensional curved surface that can solve the above-mentioned conventional problems, can easily create profile data, and can improve the efficiency of grinding work. There is to do.

In order to solve the above-mentioned problems, the invention according to claim 1 rotates a cam having a base circle portion and a three-dimensional curved surface, and is driven to rotate with respect to the cam using a plurality of profile data sequentially. the grinding wheel are relatively moved in a direction perpendicular to the center axis of the cam, in the grinding method for grinding by dividing the base circle portion and a three-dimensional curved surface of the cam into a plurality of times, the base circle portion of the cam and the current profile data no line grinding of a three-dimensional curved surface, during the grinding process of the base circle portion, with replacing the current profile data to the next profile data, also during the grinding process of the base circle portion, the grinding wheel the next base circle parts and are moved relative to the corresponding position with the base circle portion of the grinding scheduled position for grinding the three-dimensional curved surface, of the cam by the next profile data And gist to carry out grinding over the scan circle portion and the three-dimensional curved surface continuously.

The gist of the invention of claim 2 is that, in claim 1, the base circle portion of the cam is ground by a straight portion of a grindstone, and the three-dimensional curved surface is ground by an arc portion of the grindstone.
The invention described in claim 3 is the invention according to claim 2, wherein each profile data is created in consideration of the movement of the machining point of the arc portion of the grindstone with respect to the three-dimensional curved surface of the cam. And

  The gist of a fourth aspect of the present invention is that, in the second or third aspect, the grindstone has a straight portion at the center and arc portions on both the left and right sides of the straight portion.

  According to the present invention, during the process of grinding the base circle portion of the cam, the current profile data is replaced with the next profile data, and the grindstone is relatively moved to the next grinding position to grind the outer surface of the cam. Was performed continuously. For this reason, the profile data can be easily created and the efficiency of the grinding operation can be improved.

Hereinafter, an embodiment of a method for grinding a cam having a three-dimensional curved surface embodying the present invention will be described with reference to FIGS.
As shown in FIG. 2, a Z-axis guide rail 12 is laid on the base 11 of the cam grinding machine. A workpiece support 13 is attached to the Z-axis guide rail 12 by a Z-axis drive motor 14 and a ball screw nut (not shown). It is supported so as to be able to reciprocate in the Z-axis direction. A spindle stock 15 is disposed on the work support 13 and includes a spindle 16 and a spindle motor 17 for rotating the spindle 16. A holder 18 is disposed on the work support 13 such that the distance between the holder 18 and the main shaft 16 can be adjusted, and a support shaft 19 is provided on the center axis so as to face the main shaft 16.

  A camshaft 20 is detachably mounted between the main shaft 16 of the main shaft base 15 and the support shaft 19 of the holder 18 so that the axis extends along the Z-axis direction that is the moving direction of the work support base 13. ing. The camshaft 20 includes a linear rod 21 and a plurality of cams 22 fitted and fixed to the outer periphery of the rod 21 at a predetermined pitch. When the main shaft motor 17 is rotated in the mounted state of the camshaft 20, the camshaft 20 is rotated in one direction (see the arrow in FIG. 4) about its own central axis O.

  In this embodiment, as shown in FIGS. 3 and 4, the cam surface of the cam 22 extends from a semi-cylindrical base circle 22 a centered on the central axis O and from both ends of the base circle 22 a. A pair of lift portions 22b and a cam top portion 22c located on the opposite side of the base circle portion 22a via the lift portion 22b are provided. As shown in FIG. 3, the lift portion 22 b and the cam top portion 22 c are formed in a three-dimensional curved surface whose distance from the central axis O continuously changes with respect to the central axis O direction of the camshaft 20.

  As shown in FIG. 2, an X-axis guide rail 23 is laid on the base 11, and a grindstone base 24 is placed on the X-axis guide rail 23 by an X-axis drive motor 25 and a ball screw 26. It is supported so that it can reciprocate in the X-axis direction orthogonal to the (Z-axis) direction.

  A rotating grindstone 28 is rotatably supported on the grindstone base 24 via a rotating shaft 27, and the rotational movement of a grindstone motor 29 is transmitted to the rotating grindstone 28 via a belt drive mechanism 30. To be rotated. The shape of the outer peripheral surface of the rotating grindstone 28 is formed by a linear straight portion 28a and an arcuate circular arc portion 28b when viewed from a direction orthogonal to the central axis O ′ as shown in FIG. Yes.

  As shown in FIG. 2, the Z-axis drive motor 14, the main shaft motor 17 and the X-axis drive motor 25 are provided with encoders 31, 32 and 33 for detecting respective rotation angles.

Next, a control system for the cam grinding apparatus will be described with reference to FIG.
As shown in FIG. 5, the control device 41 is provided with a CPU (Central Processing Unit) 42, a ROM (Read Only Memory) 43, and a RAM (Random Access Memory) 44 for performing various arithmetic processes. . The CPU 42 constitutes a control means for controlling the operation of the entire cam grinding machine. The ROM 43 stores a program for controlling the operation of the entire cam grinding machine. The RAM 44 constitutes storage means for temporarily storing various data for executing the grinding operation. The CPU 42, ROM 43 and RAM 44 are connected to the Z-axis drive motor 14, the spindle motor 17 and the X-axis drive motor 25 via a bus 45 for transferring control signals, an interface 46 and a drive circuit (not shown). Signals from the encoders 31, 32, 33 are input to the control device 41. Note that an input device 48 such as a keyboard and a mouse and an output device 49 such as a display and a printer are connected to the bus 45 via an interface 47.

  The RAM 44 includes a large number (for example, 200 in this embodiment, for grinding the base circle portion 22a, the three-dimensional curved lift portion 22b, and the cam top portion 22c of the cam 22; Profile data D1 to D15 of 15th profile data D1 to D15) is stored in advance as position data of the grinding wheel base 24 with respect to the rotation index angle of the main shaft 16. Of the first to fifteenth profile data D1 to D15, the profile data for grinding the base circle portion 22a are all the same data. The profile data for grinding the lift portion 22b and the cam top portion 22c are all different data. Each profile data includes the lift data for each rotation angle from the central axis O of the cam 22 to the outer peripheral surface, the radius of the rotation wheel 28 and the cutting amount of the rotation wheel 28 for each rotation angle of the cam 22 as factors. It is created as data representing the position in the X-axis direction.

  Each of the profile data D1 to D15 is created based on a virtual cross section where a virtual plane S orthogonal to the central axis O of the cam 22 and the outer surface of the cam 22 intersect as shown in FIG. At this time, the arc part 28b of the rotating grindstone 28 for grinding the lift part 22b and the cam top part 22c having a three-dimensional curved surface has a constant radius of curvature, and is tangent in the axial direction passing through the machining point P of the cam top part 22c. The gradient α of L changes for each processing point P. For this reason, the position of the processing point P at which the arc portion 28b of the rotating grindstone 28 contacts the lift portion 22b or the cam top portion 22c also changes. The profile data D1 to D15 are created in consideration of the displacement (movement) of the processing point P.

Next, functions of the control device 41 will be described.
In the control device 41, since the first to fifteenth profile data D1 to D15 of the base circle portion 22a of the cam 22 are all the same data, the first grinding schedule of the cam 22 is based on the first profile data D1. During the surface grinding operation, the first profile data D1 is replaced with the second profile data D2 during the grinding operation of the base circle 22a. Further, in synchronization with the replacement operation, the control device 41 moves the workpiece support base 13 from the first grinding position to the second grinding position from the first grinding position during the grinding operation of the base circle portion 22a. It has the function of moving by one pitch in the direction.

Next, the operation of the cam grinding apparatus configured as described above will be described.
As shown in FIG. 2, in the state where the rotating grindstone 28 is disposed opposite to one cam 22 on the camshaft 20, the rotating grindstone 28 is rotated at a high speed in one direction, and the camshaft 20 is rotated in one direction. The In this state, the rotating grindstone 28 approaches the camshaft 20 from a position away from the camshaft 20 and comes into contact with the camshaft 20.

  The grinding operation of the cam 22 will be described with reference to FIG. 1. In step S1, the first profile data D1 is read from the RAM 44, and in step S2, the first grinding planned surface of the cam 22 is determined based on the first profile data D1. The base circle portion 22a, the lift portion 22b, and the cam top portion 22c are ground. In step S3, the first profile data D1 is replaced with the second profile data D2 during the grinding of the base circle 22a of the first grinding planned surface of the cam 22. In step S4, the camshaft 20 is moved in the Z-axis direction during grinding of the base circle portion 22a on the first grinding planned surface, and the rotating grindstone 28 corresponds to the base circle portion 22a on the second grinding scheduled surface of the cam 22. . In step S5, the base circular portion 22a, the lift portion 22b, and the cam top portion 22c of the second scheduled grinding surface of the cam 22 are ground. In step S6, the second profile data D2 is replaced with the third profile data D3 during grinding of the base circle 22a of the second grinding planned surface of the cam 22. In step S7, the camshaft 20 is moved in the Z-axis direction during grinding of the base circle portion 22a of the second grinding planned surface, and the rotating grindstone 28 corresponds to the base circle portion 22a of the third grinding planned surface of the cam 22. .

  The above operations are sequentially performed sequentially, and the outer periphery of the cam 22 is ground into a required shape. Further, the grinding with respect to the cam 22 reduces the cutting amount (grinding allowance) of the rotating grindstone 28 with respect to the outer periphery of the cam 22 and performs a plurality of grinding steps in the order of rough grinding → medium finish grinding → finish grinding → spark out. After that. Through this grinding process, a predetermined three-dimensional cam 22 having a non-circular shape as shown in FIGS. 3 and 4 is formed on the outer periphery of the cam 22.

FIGS. 7 and 8 schematically show how the first to fifteenth profile data D1 to D15 are replaced in the base circle portion 22a.
According to the method for grinding a cam having a three-dimensional curved surface in the above embodiment, the following effects can be obtained.

  (1) In the above embodiment, when the outer surface of the cam 22 is ground using a plurality of profile data for grinding the base circle 22a, the lift 22b and the cam top 22c of the cam 22, the base circle During the grinding of the portion 22a, the current profile data is replaced with the next profile data, and the cam 22 is moved from the current grinding position to the next planned grinding position. For this reason, it is not necessary to approach and separate the rotating grindstone 28 from the camshaft 20 for each grinding operation according to each profile data, and the efficiency of the grinding operation can be greatly improved.

  (2) In the above-described embodiment, the plurality of profile data are created independently of each other rather than the profile data for grinding the cam 22 in a spiral shape, so that partial correction of the profile data can be easily performed.

  (3) In the above embodiment, since the linear portion 28a and the arc portion 28b are formed on the rotary grindstone 28, the base circle portion 22a of the cam 22 is ground using the linear portion 28a, and the lift portion is used using the arc portion 28b. 22b and the cam top part 22c can be ground, the processing accuracy of the grinding surface of the cam can be improved, and the wear amount of the rotating grindstone 28 can be suppressed.

In addition, you may change the said embodiment as follows.
As shown in FIG. 9, arc portions 28b may be formed on the left and right sides of the linear portion 28a of the rotating grindstone 28, and the three-dimensional curved surface of the cam 22 where the gradient α is reversed with respect to the central axis O may be ground. .

  As shown in FIG. 10, the cam 22 may be ground by forming only the semicircular arc portion 28 b on the rotating grindstone 28. In this case, the center part in the left-right direction of the arc part 28b is used to grind the base circle part 22a.

The workpiece support base 13 may be omitted, the headstock 15 may be mounted at a predetermined position on the base 11, and the grindstone base 24 may be moved in the Z-axis direction.
A grinding device that grinds the outer surface of the cam 22 by moving the grindstone 28 that is rotationally driven with respect to the cam 22 in a direction perpendicular to the central axis O of the cam 22 may be used.

The flowchart of the grinding method of the cam which has a three-dimensional curved surface of this invention. The top view of a cam grinder. The enlarged front view of a cam. FIG. 4 is a right side view of the cam of FIG. 3. The block circuit diagram of the control system of a cam grinder. The front view which shows the relationship between a cam and a rotating grindstone. The front view which shows the grinding operation of a cam. The bottom view of the cam of FIG. The front view of the cam and rotary grindstone which show another example of this invention. The front view of the rotary grindstone which shows another example of this invention.

Explanation of symbols

  O ... center axis, P ... machining point, D1 to D15 ... profile data, 22 ... cam, 22a ... base circle, 28 ... grindstone, 28a ... linear part, 28b ... arc part.

Claims (4)

While rotating the base circle and the cam having a three-dimensional curved surface, the grindstone that is rotationally driven with respect to the cam is sequentially moved in a direction perpendicular to the central axis of the cam by using a plurality of profile data in order. In the grinding method of grinding the base circle and the three-dimensional curved surface in a plurality of times ,
No line grinding of the base circle portion and a three-dimensional curved surface of the cam by the current profile data, during the grinding process of the base circle portion, with replacing the current profile data to the next profile data, also of the base circle portion During the grinding process, the grindstone is relatively moved to a position corresponding to the base circle portion of the next base circle portion and a three-dimensional curved surface to be ground, and the base circle of the cam is determined by the next profile data. Grinding a cam having a three-dimensional curved surface characterized by continuously grinding the part and the three-dimensional curved surface . 2. The method of grinding a cam having a three-dimensional curved surface according to claim 1, wherein the base circle portion of the cam is ground by a straight portion of a grindstone, and the three-dimensional curved surface is ground by an arc portion of the grindstone. The profile data according to claim 2, wherein each profile data is created in consideration of movement of a machining point of a circular arc portion of a grindstone with respect to the three-dimensional curved surface of the cam. Grinding method. 4. The method for grinding a cam having a three-dimensional curved surface according to claim 2, wherein the grindstone has a linear portion at the center and arc portions on both the left and right sides of the linear portion.

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