JPH02124254A - Cylindrical grinder - Google Patents

Abstract

PURPOSE:To execute grinding with high roundness accuracy without causing any dent at an oil hole part even in case of a work having a small hole at one part of a cylindrical face of an oil hole, etc., by providing a synchronous control means controlling the grinding resistance variable means to have to reduce the grinding resistance on each preset specified rotating position by receiving a signal transmitted from a main shaft detecting means. CONSTITUTION:A rotation position detecting means 2 detecting the rotation position of a main shaft 1 is provided. A grinding resistance variable means 4 is controlled by a synchronous control means 3 in order to reduce the grinding resistance on each preset specified rotation position by receiving a signal from this rotation position detecting means 2. Consequently, the dent generated at the oil hole part provided on a work can be reduced and the roundness accuracy in grinding can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a cylindrical grinder, and particularly to a device suitable for application to a crankpin grinder.

"Conventional Technology" In conventional cylindrical grinders, the accuracy of the roundness of the ground surface of the workpiece has been ensured by stopping the grindstone head and performing spark-out grinding. There was no cylindrical grinder equipped with a means for periodically changing the grinding resistance, such as by slightly changing the feed amount of the grindstone head in synchronization with the rotation of the main shaft.

``N Problems to be Solved by the Invention'' However, the machined surface of a workpiece is not necessarily a -like cylindrical surface, and some have small holes such as oil holes on the cylindrical surface. When this type of workpiece is ground with a conventional cylindrical grinder and the roundness accuracy of the ground surface is examined, a minute dent of 2 to 3 microns is found in the oil hole area, as shown by the arrow in Figure 7. However, there is a problem that machining accuracy often deteriorates.

The present invention has been made to solve the above problems, and its purpose is to prevent dents from occurring in the oil holes even in workpieces such as oil and water that have small holes in a part of the cylindrical surface. First, it is an object of the present invention to provide a cylindrical grinder capable of grinding with high roundness accuracy.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a rotational position detection means 2 for detecting the rotational position of the main shaft 1, as shown in FIG.
, a grinding resistance variable means 4 for changing the grinding resistance, and a synchronizer for controlling the grinding resistance variable means to reduce the grinding resistance at each preset rotational position in response to a signal from the rotational position detection means 2. There is provided a cylindrical grinding machine characterized by comprising: a control means 3;

Here, the grinding resistance variable means 4 includes a means for changing the rotational speed of the main shaft, a means for changing the rotational speed of the grinding wheel, and a means for slightly changing the feed amount of the grinding wheel head.

There are means for changing the feed amount of the rest, means for slightly displacing the support base of the grinding wheel head or the rest feeder, and means for changing the compliance of the main shaft bearing or the grinding wheel shaft bearing.

"Operation" Figure 2 is a model diagram showing a cylindrical grinder. The grinding wheel G and the workpiece W are not supported by a completely rigid body, but by an elastic body having a finite value of compliance. Regarding the grinding wheel G, the compliance Cw s of the grinding wheel shaft including the grinding wheel bearing.

Compliance Ch of the ball screw * + Compliance Ca of the thrust bearing that supports the ball screw
The total compliance of k, the compliance of the feed support part such as the frame, C, is the total compliance of the grindstone feed system. Regarding the workpiece W, the compliance of the spindle including the spindle bearing C1, the compliance of the chuck C01, and the compliance of the workpiece itself Cwe
and, when using a rest, the compliance of the rest C,
Compliance is an integrated approach to compliance.

Grinding wheel G and workpiece W receive grinding resistance at the contact position,
Grinding is performed in a state of elastic displacement according to each total compliance.

On the other hand, it is known that the refinement component Fn of the grinding resistance is given by the following equation.

...(1) Here, Ko is a constant determined by the material of the workpiece W, B is the grinding width, ■ is the circumferential speed of the workpiece W, ■ is the circumferential speed of the grinding wheel G, S is the depth of cut, ε is a constant determined by the material of the workpiece, D is the diameter of the grinding wheel G, d is the diameter of the workpiece W, and ω is the average abrasive grain spacing.

Now, as shown in FIG. 3, when oil and water 6 are provided on the machined surface of the workpiece W, the grinding width B is reduced by the diameter of the oil and water 6 in the oil and water portion. When the grinding width B decreases, the grinding resistance Fn decreases according to equation (1). However, grinding wheel G
Since both the workpiece and the workpiece W are elastically supported, the cutting depth S changes to a position where the elastic force corresponding to each displacement and the grinding resistance Fn are balanced. It is thought that due to this effect, in the conventional device, the depth of cut increased in the oil/water area, causing a slight dent.

In the cylindrical grinder according to the present invention, the grinding resistance is reduced in synchronization with the rotation of the main shaft, corresponding to the reduction in the grinding width by the oil and water 6. Therefore, the grinding resistance is controlled in accordance with the change in the grinding width, so that the depth of cut does not change.

The grinding resistance variable means that changes the spindle rotation speed or the grindstone rotation speed cancels out the influence of the change in the grinding width B shown in equation (1) on the grinding resistance Fn by the change in the rotation speed, and keeps the grinding resistance constant. control.

Those that change the feed amount of the grinding wheel head or rest, or those that displace the support of the grinding wheel head or rest feeding part, change the amount of elastic displacement to change the elastic force and adjust the balanced grinding resistance Fn to the grinding width B. control to the specified value.

The device that changes the compliance of the main shaft bearing or the grindstone bearing controls the balanced grinding resistance Fn to a value corresponding to the grinding width B by changing the elastic force.

"Example" Embodiments of the present invention will be described with reference to the drawings.

FIG. 4 is a configuration diagram showing a cylindrical grinder according to the present invention.

This cylindrical grinder is a pin grinder for machining the engine crankshaft, and as shown in Fig. 5, the crankshaft 50
It is used for finishing the grinding parts 501 to 504 of 0. Oil/water 6 is provided in each of the bottle portions 501 to 504.

A table 11 is provided in front of a bed 10 of the grinding machine so as to be slidable in the left-right direction (Z-axis direction), and is moved via a feed screw 3 by a servo motor 12 attached to the side surface of the bed 10. A pair of headstocks 14 and 15 are arranged on the left and right sides of the table II. Each headstock 14.15
The main shaft 18. is equipped with an eccentric chuck device 16.17.
19 are mounted on a shaft, and are rotationally driven by main shaft motors 20 and 21 each consisting of a servo motor. Each spindle motor 2
Rotary encoders 22 and 23 are attached to 0 and 21,
The rotational position of the main shaft 18, 19 is detected.

The crankshaft of the engine, which is the workpiece W, has journal parts 505 and 506 at the ends of the shaft held by eccentric chucks 16 and 17 of the left and right main shafts 18 and 19, and a grinding process is carried out at the bin part 50.
It is driven to rotate around 1 as the center of rotation. The main shaft motor 21 on the right side follows the rotation of the main shaft motor 20 on the left side, and is driven in 021 rotation as if it were one shaft.

On the other hand, behind the bed 10, a grindstone head 25 is guided so as to be movable in a direction (X-axis direction) perpendicular to the rotational axis of the main shaft 18, and is driven by a servo motor 26 fixed to the surface of the bed 10 via a feed screw 27. It is designed to be moved. A grinding wheel G is mounted on the grinding wheel head 25 in parallel with the axis of the main shaft 18, and is rotationally driven by a grinding wheel drive motor 28.

In addition, at a position facing the grinding wheel G in front of the bed 10,
A rest device 30 is provided. The contact 31 of the rest device 30 is movable in the direction toward the grinding wheel G (X-axis direction), and is moved forward and backward by a servo motor 32.

The contact 31 of the rest device 30 is pressed against the grinding surface of the workpiece W to stop the workpiece from wobbling.

Each axis servo motor 12, 26, 32 and left and right main axis motors 20, 21 are connected to each servo motor drive rotation 41 to 45, and the numerical value l! lIIw device (NC device) 5
It is rotated according to the number of command pulses from 0.

The numerical control device 50 is a main C for controlling the grinding machine.
PU51. ROM 52 that stores a control program. N.C.
Equipped with RAM 5B for storing data, etc., and tape reader 6
1. CRT display 62, keyboard 63. operation!
! A signal from 1164 is input via interface 54. In addition, the main CPIJ51 has a main shaft 18.
Signals from rotary encoders 22, 23 for detecting the rotational position of 19 are input via an interface 55.

In addition to the main CPU 51, the numerical control device 50 includes a drive CPU 56 for servo control.
It is connected to the main CPU 51 via the RAM 57 . The drive CPυ 56 outputs command pulses to each servo motor drive circuit 41 to 45 via the pulse distribution circuit 58.

In this embodiment, as the grinding resistance variable means, the feed of the grindstone head 25 is slightly retracted during grinding. Therefore, in addition to the normal NC data area 531, the RAM 53 of the main CPU 51 has an area 532 in which synchronous rotation position data that provides the rotational position of the main shaft 18, 19 at which the grinding wheel head 25 starts retracting, and a wheel head An area 533 is provided in which synchronization l1M# data is provided, which provides the relationship between the feed amount ΔX for retracting the spindle 25 and the spindle rotation angle θ. These data are set from the keyboard 63.

The synchronous rotation position data 532 is the rotation angle θ from the phase reference position of the crankshaft, which is the workpiece W, to the edge of the oil water. Set by. The synchronization control data is set, for example, by giving the retreat amount ΔX of the grindstone head 25 using the following equation.

ΔX=Asin(r・θ・R/dh) (However, 0×θ
<d/R>...(2) Here, A is a constant, and θ is the synchronous rotation position θ. The rotation angle of the main shaft 18 from , R is the radius of the workpiece W bin portion 501, and dh is the diameter of the oil/water.

By superimposing the retreat amount ΔX calculated in this way on the feed amount X based on normal NC data and controlling the X-axis servo motor 26, the grinding resistance Fn shown in equation (1) is calculated.
is controlled to a value corresponding to the grinding width B to reduce dents in the oil/water portion.

FIG. 6 shows data showing the roundness of the pin portion 501 processed in this manner, and shows that the dents in the oil/water portion as seen in FIG. 7 can be almost eliminated.

In the embodiment described above, the X-axis servo motor 26 is controlled to slightly change the feed amount X of the grindstone head 25.
(2) A similar effect can be obtained by controlling the shaft servo motor 32 to unevenly change the feed amount of the rest 30 and by changing the pressing force of the contact 31.

It is also possible to synchronize the rotational speed of the main shafts 18 and 19 with the rotational position of the main shafts 18 and 19 and to slightly reduce the rotational speed at the armhole. It is also possible to increase the speed. However, since the rotational drive system of the grinding wheel G has extremely large inertia, this is not a good idea.

Furthermore, instead of controlling the servo motors 26 and 32 of the feed system, an actuator using a piezoelectric element or the like may be attached to the support base of the grinding wheel head 25 or the rest device 30 to displace the entire support base by a minute amount. It is possible.

Furthermore, a static pressure bearing is used for the bearing of the main shaft 18, 19 or the grinding wheel G, and the flow rate of the pressure oil supplied to the bearing is controlled by an electromagnetic control valve. It is also possible to control the pressure in the pocket of the hydrostatic bearing to vary the compliance of the bearing.

"Effects of the Invention" Since the present invention has the above-mentioned structure, it has the excellent effect of reducing the dents that occur in the armholes provided in the workpiece and improving the roundness accuracy of the grinding process. There is.

[Brief Description of the Drawings] Figure 1 is a diagram clearly showing the configuration of the present invention, Figure 2 is a model diagram showing the elastic displacement of a cylindrical grinder, Figure 3 is a perspective view showing the machined surface of a workpiece, Fig. 4 is a plan view showing the configuration of the pin grinder, Fig. 5 is a front view showing the workpiece, Fig. 6 is a drawing showing the roundness accuracy according to this embodiment, and Fig. 7 is a diagram showing the roundness accuracy in the conventional device. FIG. 3 is a diagram showing roundness accuracy. 18.19. ,,main axis, 20,21. ,, Rotary encoder (rotational position detection means), Wll, Workpiece, G, ,
, [Car, 25, , Grindhead, 26, , X-axis servo motor, 30, Rest device, 50,
. Numerical control device, 51, Main CPU, 53.
. , RAM, 532 , , synchronous rotation position data area,
533, , Synchronous control data area. Figure Figure Figure Figure

Claims (1)

[Claims] a rotational position detection means for detecting the rotational position of the spindle; a grinding resistance variable means for changing the grinding resistance; A cylindrical grinding machine comprising: synchronous control means for controlling the grinding resistance variable means.