JP2005014171A - Grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grinding method capable of easily grinding an outside surface of a workpiece in a three-dimensional shape, by keeping the service life of a grinding wheel long. <P>SOLUTION: This grinding method grinds the outside surface of a three-dimensional cam W1 in a three-dimensional shape, by relatively moving the rotatingly driven grinding wheel G for forming a grinding action surface in a curved surface shape, in the rotational axis W2 direction of the three-dimensional cam W1 and the direction orthogonal to the rotational axis W2, to the rotatingly driven three-dimensional cam W1. The center of a spherical surface shape G1 of the grinding wheel G exists on the rotational axis G3 of the grinding wheel G. The rotational axis G3 of the grinding wheel G is inclined to the rotational axis W2 of a camshaft W. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grinding method for grinding a workpiece into a three-dimensional shape.
[0002]
[Prior art]
As a technique for grinding a workpiece into a three-dimensional shape, the applicant of the present application has proposed a grinding method for grinding a workpiece into a three-dimensional shape by plunge grinding as disclosed in Patent Document 1. In the cam grinding machine mainly disclosed in Patent Document 1, an axis orthogonal to the Z-X plane, a so-called “B-axis” is provided on a slide body that moves in the X-axis direction orthogonal to the Z-axis direction that is the moving direction of the table. A horizontal revolving body that revolves as an axis is provided, and an axial head that revolves around an axis orthogonal to the B axis, the so-called “A axis”, is provided on the horizontal revolving body. Here, the shaft head is to rotatably support the grinding wheel. Then, using this cam grinder, the work side movement is C-axis rotation and Z-axis movement biaxial movement, and the grinding wheel side movement is X-axis movement, B-axis turning, and A-axis turning three-axis movement. This is a grinding method for plunge grinding of the profile surface of a three-dimensional cam.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-746
[Problems to be solved by the invention]
However, the above prior art has the following disadvantages. In the grinding machine shown in Patent Document 1, when grinding the outer surface of a workpiece into a three-dimensional shape, the grinding wheel is moved with respect to the workpiece by X-axis movement, B-axis rotation, and A-axis rotation to perform plunge grinding. It had to be controlled and ground by three-axis movement. Compared to general cylindrical grinders, etc., there are many control axes on the grinding wheel side, and the mechanical configuration of the cam grinder becomes complicated, so problems such as poor convenience and high cost was there.
[0005]
By the way, it is conceivable to grind the workpiece into a three-dimensional shape by traverse grinding instead of plunge grinding. However, in traverse grinding, the part that contacts the outer surface of the workpiece is concentrated in one place on the grinding surface of the grinding wheel, so the reduction of the grinding wheel is concentrated in one place, the number of truing increases, and the life of the grinding wheel is shortened. The problem occurs. In addition, the calculation process for controlling the position of the grindstone becomes complicated, and the amount of control data becomes enormous, resulting in a problem that the burden on the control device increases.
[0006]
Therefore, in view of the above circumstances, an object of the present invention is to provide a grinding method that can keep the life of a grindstone long and can easily grind the outer surface of a workpiece into a three-dimensional shape.
[0007]
[Means for Solving the Problems]
In the grinding method according to the first aspect of the present invention, a grinding wheel having a curved working surface formed into a curved surface shape and a rotationally driven grindstone with respect to the rotationally driven workpiece, the rotational axis direction and rotational axis of the workpiece are The outer surface of the workpiece is ground into a three-dimensional shape by relatively moving in the orthogonal direction.
[0008]
Here, the three-dimensional shape is a shape whose cross-sectional shape changes according to the position in the rotation axis direction, and examples thereof include a three-dimensional cam. The three-dimensional cam is used for the purpose of improving the performance of an internal combustion engine, for example, and has a base circle formed in the same arc shape at any position in the rotation axis direction and a lift amount for each angle phase. The lift portion is formed so as to change and the amount of change in the lift amount differs depending on the position in the rotation axis direction.
[0009]
Therefore, according to the grinding method of the first aspect of the invention, the grindstone is moved relative to the workpiece in the direction of the rotation axis of the workpiece and in the direction perpendicular to the rotation axis, while the grinding surface of the grindstone of the workpiece is The outer surface is ground spirally to create a three-dimensional shape. At this time, grinding may be performed by controlling the rotation of the workpiece and the relative movement of the workpiece with respect to the workpiece of the grindstone in the direction of the rotation axis and the direction orthogonal to the rotation axis. Since there is no need to control a large number of five control axes such as the axis, the Z axis, the X axis, the B axis, and the A axis, the convenience is improved. Moreover, since the control axis of the grindstone can be reduced, the mechanical configuration on the grindstone side can be simplified. In addition, since the grinding surface of the grindstone is formed in a curved shape, the grinding surface of the grindstone and the outer surface of the workpiece are in contact with each other in a state close to point contact, and the contact location is on the grinding surface of the grindstone. It will change according to the rotation angle of the workpiece. For this reason, since the part which contacts the outer surface of a workpiece does not concentrate on one place in the grinding action surface of a grindstone, it becomes possible to extend the life of a grindstone by reducing the frequency | count of truing of a grindstone.
[0010]
A grinding method according to a second aspect of the present invention is the grinding method according to the first aspect, wherein the curved surface shape of the grindstone is a spherical shape, and the center of the spherical shape exists on the rotation axis of the grindstone. is there.
[0011]
Therefore, according to the grinding method of the invention of claim 2, in addition to the operation of the grinding method of the invention of claim 1, the grinding action surface of the grindstone is formed in a spherical shape, and the center of the spherical shape is on the rotation axis of the grindstone. Therefore, if the reference point for determining the position of the grinding wheel is the center of the spherical shape, the distance from the grinding action point to the reference point no matter which part of the grinding work surface of the grinding wheel contacts the outer surface of the workpiece Is always constant. For this reason, the calculation process for determining the position of the grindstone in a series of machining operations is facilitated. In addition, since the contact point between the workpiece and the grindstone is determined as one point in the direction of the rotation axis of the workpiece, calculation processing for determining the position of the grindstone in a series of machining operations is facilitated.
[0012]
A grinding method according to a third aspect of the present invention is the grinding method according to the first or second aspect, wherein the rotational axis of the grindstone is inclined with respect to the rotational axis of the workpiece.
[0013]
When the rotation axis of the grindstone is made parallel to the rotation axis of the workpiece, the diameter of the grindstone must be increased so that the shaft head that supports the grindstone does not interfere with the workpiece or the member that supports the workpiece. On the other hand, according to the grinding method of the invention of claim 3, in the grinding method of claim 1 or claim 2, even if a grindstone having a small diameter is used, the shaft head that supports the grindstone has a workpiece or a work piece. It becomes difficult to interfere with a member that supports an object, and it is possible to avoid the occurrence of the above-described problems.
[0014]
In recent years, a three-dimensional cam having a recess in the contour curve has been provided for the purpose of improving the performance of the internal combustion engine. When grinding such a three-dimensional cam, a portion where the diameter of the grindstone is larger than the depression cannot be ground. In the grinding method according to the third aspect of the present invention, even when such a three-dimensional cam is ground, it is possible to grind using a grindstone smaller than the recess.
[0015]
Further, especially when the curved surface shape of the grindstone is a spherical shape as in the grinding method of the invention of claim 2, the center of the spherical shape exists on the rotation axis of the grindstone, so the inclination angle of the rotation axis is changed. However, since the grinding point calculation process is the same, there is no need to recalculate, and the grinding method of the invention of claim 3 is particularly effective.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a grinding method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view schematically illustrating a configuration of a grinding machine used in a grinding method according to an embodiment of the present invention. FIG. 2 is a side view showing a three-dimensional cam of a camshaft. FIG. 3 is a front view, and FIG. 3 is an explanatory diagram for explaining a state where (a) the grindstone grinds a base circle portion of the three-dimensional cam, and (b) an explanation for explaining a state where the grindstone grinds the lift portion of the three-dimensional cam. FIG.
[0017]
First, the grinding machine 1 used in the grinding method of this embodiment will be described. As shown in FIG. 1, the grinding machine 1 mainly includes a bed 10, a grindstone table 20 and a table 30 installed on the upper surface of the bed 10, and a CNC device 40 that controls a series of operations related to grinding. ing. In this embodiment, a case where a camshaft W having a three-dimensional cam is ground will be described as an example. The coordinate system of the grinding machine 1 has two linear axes X and Z and a rotation axis C. The Z-axis is a linear axis in the axial direction of the main shaft 31 that rotates and supports one end of the camshaft W, and the X-axis is a linear axis that is horizontal and orthogonal to the Z-axis. The C axis is a rotation axis around the axis of the main shaft 31.
[0018]
The bed 10 constitutes a base portion of the grinding machine 1, and includes a guide surface 11 and a feed screw 12 for moving the grindstone table 20 in the X-axis direction, and a guide surface 13 for moving the table 30 in the Z-axis direction. And a feed screw 14. Further, on the side surface of the bed 10, there is a servo motor controlled by a CNC device 40 which will be described later, and a grinding wheel base moving motor 15 that rotationally drives the feed screw 12, and indirectly from the rotation amount of the grinding wheel base moving motor 15. An encoder 16 that detects the position of the grinding wheel platform 20 in the X-axis direction, a servo motor controlled by the CNC device 40, a table moving motor 17 that rotationally drives the feed screw 14, and a rotation amount of the table moving motor 17 An encoder 18 that indirectly detects the position of the table 30 in the Z-axis direction is provided. The encoders 16 and 18 feed back a pulse signal proportional to the rotation amounts of the grindstone table moving motor 15 and the table moving motor 17 to the grindstone table moving motor driving circuit 50 and the table moving motor driving circuit 51 described later.
[0019]
The grindstone base 20 includes a grindstone G, a grindstone shaft 21 that supports the grindstone G and is inclined with respect to the Z axis, a shaft head 24 that supports the grindstone shaft, a drive transmission device 22 such as a pulley and a belt, A grindstone rotation motor 23 that is controlled by the CNC device 40 and rotates the grindstone shaft 21 via the drive transmission device 22 is mainly provided. In addition, although not shown, a cover that covers substantially the entire grindstone G for safety, a nozzle that applies a grinding liquid to the grinding action point of the grindstone G, and the like are also provided. Further, the grindstone table 20 is installed on the guide surface 11 of the bed 10 so as to be movable in the X-axis direction, and its position and moving speed are precisely controlled by the CNC device 40. In addition, since the rotational speed of the grindstone G during grinding is very high, the bearing (not shown) of the grindstone shaft 21 is a precision bearing such as a non-circular plain bearing, a segment bearing, a hydrostatic bearing, or a microsphere bearing. Is used. The reason why the grindstone shaft 21 is inclined is to prevent interference between the movement of the grindstone table 20 in the X-axis direction and the movement of the table in the Z-axis direction during grinding.
[0020]
The grindstone G has a spherical shape G1, and the center G2 (see FIG. 3A) of the spherical shape G1 exists on the rotation axis G3 of the grindstone G. The grindstone G is composed of three elements: abrasive grains corresponding to a cutting edge of a tool, a binder that holds the abrasive grains, and pores that function as a chip pocket for temporarily storing chips. In addition, the characteristics of the grindstone G are five factors: the type of abrasive grains, the particle size indicating the size of the abrasive grains, the type of binder, the degree of bonding indicating the strength of the binder, and the volume ratio (abrasive ratio) of the abrasive grains. It is controlled and needs to be selected as appropriate according to the workpiece to be ground. Examples of the abrasive grains include alumina oxide, silicon carbide, diamond, and CNB. Examples of the binder include vitrified, resinoid, silicate, shellac, rubber, metal bond, and the like.
[0021]
The table 30 includes a head stock 32 on one end side and a tailstock 33 on the other end side, and supports the camshaft W. The table 30 is installed on the guide surface 13 of the bed 10 so as to be movable in the Z-axis direction, and its position and moving speed are precisely controlled by the CNC device 40.
[0022]
The headstock 32 is a main shaft 31 that supports one end of the camshaft W, a servo motor controlled by the CNC device 40, a main shaft rotating motor 34 that rotates the main shaft 31, and the amount of rotation of the main shaft rotating motor 34. An encoder 35 that indirectly detects the rotation angle of the main shaft 31 is mainly provided. A chuck is provided at the spindle end of the spindle 31 to grip the camshaft W and to transmit the rotation of the spindle 31 to the camshaft W. The encoder 35 feeds back a pulse signal proportional to the amount of rotation of the spindle rotating motor 34 to a spindle rotating motor control circuit 53 described later.
[0023]
The tailstock 33 mainly includes a tailstock shaft 36 that supports one end of the camshaft W and can move in the Z-axis direction, and a spring (not shown) that pushes the tailstock shaft 36 in the direction of the headstock 32. It is fixed on the table 30 with screws according to the length of the workpiece.
[0024]
The CNC device 40 includes a CPU 41 including a logic / arithmetic unit and a control unit, a memory 42 for storing programs and data used by the CPU 41, a bus 43 for transferring data and control signals, a bus 43, and each device. An interface 44 that mediates between them, an input device 45 such as a keyboard and a mouse, and an output device 46 such as a display are provided. The memory 42 includes a machining operation program 47 for controlling a series of operations related to grinding, rotation angle data of the camshaft W, distance data between the camshaft W and the grindstone G correlated with the rotation angle data of the camshaft W, Control data 48 necessary for a series of machining operations such as movement speed data of the table 30 is stored.
[0025]
Further, a grindstone table moving motor driving circuit 50, a table moving motor driving circuit 51, a grindstone rotating motor driving circuit 52, and a spindle rotating motor driving circuit 53 are connected to the interface 44 of the CNC device. The wheel head moving motor driving circuit 50, the table moving motor driving circuit 51, the wheel rotating motor driving circuit 52, and the spindle rotating motor driving circuit 53 receive a command signal from the CPU 41 and input the wheel head moving motor 15 and the table moving motor 17. These are circuits for driving the grindstone rotating motor 23 and the spindle rotating motor 34, respectively. The grindstone head moving motor driving circuit 50, the table moving motor driving circuit 51, and the spindle rotating motor driving circuit 53 automatically receive a command value from the CPU 41 and feedback signals (feedback values) from the encoders 16, 18, and 35. As compared with the above, the feedback signal is corrected so as to approach the target value, and the grindstone table moving motor 15, the table moving motor 17, and the spindle rotating motor 34 are respectively controlled.
[0026]
Here, the camshaft W will be described. The camshaft W has a three-dimensional cam W1 for operating an intake / exhaust valve of the engine. As shown in FIGS. 2A and 2B, the three-dimensional cam W1 includes a base circle W3 formed in the same arc shape at any position in the rotation axis W2 direction of the camshaft W, and each angular phase. Further, the lift amount is changed, and the lift amount W4 is formed so that the change amount of the lift amount differs depending on the position in the direction of the rotation axis W2.
[0027]
Next, the grinding method of this embodiment will be described. In the grinding method of the present embodiment, the three-dimensional cam W1 of the camshaft W is ground using the above-described grinding machine 1. The CNC device 40 of the grinding machine 1 performs grinding by mainly controlling the grindstone table moving motor 15, the table moving motor 17, the grindstone rotating motor 23, and the spindle rotating motor 34 based on the commands of the machining operation program 47 and the control data 48. Execute. Specifically, the CNC device 40 controls the grindstone rotation motor 23 to rotate the grindstone G at a high speed, and also controls the table moving motor 17 so that the three-dimensional cam W1 is suitable for machining on the Z axis. The table 30 is moved so as to be arranged at the initial position. Further, the CNC device 40 controls the table moving motor 17 based on the control data 48 to move the three-dimensional cam W1 on the Z axis at a constant speed, and the spindle rotating motor 34 and the grindstone moving motor 15 are moved. Control is performed synchronously, and the grindstone base 20 is moved on the X axis in accordance with the rotation angle of the camshaft W to grind the outer surface of the three-dimensional cam W1.
[0028]
The synchronous control of the spindle rotating motor 34 and the grindstone moving motor 15 will be described in detail. During grinding of the base circle W3, as shown in FIG. 3A, the distance between the center G2 of the grindstone G and the rotation axis W2 of the camshaft W is kept constant in consideration of the cutting amount. . Further, while the lift portion W4 is being ground, the lift amount of the lift portion W4 changes for each angle phase as shown in FIG. Grind while moving back and forth in the direction.
[0029]
Since the grinding surface of the grindstone G is formed in the spherical shape G1, it contacts the outer surface of the three-dimensional cam W1 in a state close to point contact, and the camshaft W rotates around the C axis in the Z axis direction. Since it is sent at a constant speed, the grindstone G grinds the outer surface of the three-dimensional cam W1 in a spiral shape. At this time, as shown by the hatched portions in FIGS. 3A and 3B, in the spherical shape G1 that is the grinding action surface of the grindstone G, the contact point with the three-dimensional cam W1 is the camshaft W. It will change according to the rotation angle. For this reason, in the spherical shape G1 that is the grinding action surface of the grindstone G, the portion that comes into contact with the outer surface of the three-dimensional cam W1 does not concentrate in one place. It can be stretched.
[0030]
As described above, in the grinding method of the above embodiment, the rotation of the camshaft W around the C axis, the movement of the camshaft W in the Z-axis direction, and the movement of the grindstone G in the X-axis direction are controlled synchronously. That's fine. For this reason, it is not necessary to control a large number of five control axes such as the C axis, the Z axis, the X axis, the B axis, and the A axis in synchronization with the prior art, so that the convenience is improved.
[0031]
Moreover, in the grinding method of the said embodiment, the grinding action surface of the grindstone G is the spherical shape G1, and the center G2 of the spherical shape G1 exists on the rotation axis G3 of the grindstone G. For this reason, if the reference point for determining the position of the grindstone G is the center G2 of the spherical shape G1, no matter which part of the spherical shape G1, which is the grinding action surface of the grindstone G, contacts the outer surface of the three-dimensional cam W1. The distance from the grinding point to the reference point is always constant. For this reason, the calculation process for determining the position of the grindstone G in a series of processing operations is facilitated. Therefore, the processing burden on the CNC device 40 can be reduced.
[0032]
In the grinding method of the above embodiment, the rotation axis G3 of the grindstone G is provided to be inclined with respect to the rotation axis W2 of the camshaft W. For this reason, the shaft head 24 is less likely to interfere with the camshaft W, the headstock 32 and the tailstock 33 of the table 30. Further, even if the inclination angle between the rotation axis W2 of the camshaft W and the rotation axis G3 of the grindstone G is changed, the distance from the center G to the grinding action point is constant, so that the grinding action point calculation process is the same. Therefore, it is not necessary to recalculate, and simplicity can be improved.
[0033]
The present invention has been described with reference to the preferred embodiment. However, the present invention is not limited to this embodiment, and various modifications can be made without departing from the spirit of the present invention as described below. Improvements and design changes are possible.
[0034]
That is, in the grinding machine 1 used in the grinding method of the above embodiment, the grindstone shaft 21 is provided so as to be inclined with respect to the Z axis. However, the present invention is not particularly limited thereto. The inclination angle of the shaft head 24 with respect to 20 may be adjustable. Thereby, in the spherical shape G1 of the grindstone G, the contact point with the outer surface of the three-dimensional cam W1 can be changed in a wider range, and the life of the grindstone G can be extended. Further, the table 30 may be provided so as to be pivotable by a central pivot, and the contact point with the outer surface of the three-dimensional cam W1 in the spherical shape G1 of the grindstone G may be changed.
[0035]
Moreover, in the grinding method of the said embodiment, although the three-dimensional cam W1 of the camshaft W was shown as grinding object, things other than a camshaft may be sufficient.
[0036]
【The invention's effect】
As described above, the grinding method according to the first aspect of the present invention can grind more easily than the prior art. Moreover, the lifetime of a grindstone can be extended.
[0037]
In addition to the effect of the grinding method of the first aspect of the invention, the grinding method of the second aspect of the invention can easily position the grindstone.
[0038]
In addition to the effect of the grinding method of the first or second aspect of the invention, the grinding method of the third aspect of the invention can prevent interference even if a grindstone having a small diameter is used.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram schematically illustrating a grinding machine used in a grinding method according to an embodiment of the present invention.
2A is a side view and FIG. 2B is a front view showing a three-dimensional cam of a camshaft. FIG.
FIGS. 3A and 3B are explanatory diagrams for explaining a state in which the grindstone grinds the base circle portion of the three-dimensional cam, and FIG. 3B is an explanatory diagram for explaining a state in which the grindstone grinds the lift portion of the three-dimensional cam.
[Explanation of symbols]
1 Grinding machine G Grinding wheel G1 Spherical shape G2 Center G3 Rotating axis W Camshaft (workpiece)
W1 3D cam (3D shape)
W2 axis of rotation

Claims (3)

A grinding wheel having a grinding surface formed into a curved surface and rotated is moved relative to the rotationally driven workpiece in the direction of the rotation axis of the workpiece and the direction perpendicular to the rotation axis, A grinding method characterized by grinding an outer surface of the workpiece into a three-dimensional shape. 2. The grinding method according to claim 1, wherein the curved surface shape of the grindstone is a spherical shape, and the center of the spherical shape exists on the rotation axis of the grindstone. The grinding method according to claim 1 or 2, wherein a rotation axis of the grindstone is inclined with respect to a rotation axis of the workpiece.

Images