JP2002239901A - Method for grinding revolving workpiece - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for grinding a revolving workpiece capable of constantly improving roundness precision of a subject part to be ground when grinding work is stopped as the subject part measured by a measuring device has a target radius. SOLUTION: An operation expression for operating a distance X from a wheel spindle stock on a straight line connecting a revolution center O of the pin part to a revolution center P of the grinding wheel as wheel spindle stock control data X for machining is set as follows: X=L.cosθ+√[(Rg+Rp+Δx)2-L2.sin2θ] where L is a radius of revolution of a pin part 14a in a crank shaft 14, Rp is a target finished radius of the pin part, Rg is a radius of a grinding wheel, θ is a revolution angle of the pin part, and Δx is a grinding margin of the pin part 14a. In this expression, a center-to-center distance between a rotation center P of the grinding wheel and a center Op of the pin part is set as Rgp=Rg+Rp+Δx, and the grinding margin for every 360 deg. of the pin part is set constant. Therefore, when the revolution angle θ is changed in the range of 0-360 deg., the grinding margin is not changed, and by setting the number of times of revolution of the pin part as a multiple of an integer, roundness precision of the pin part can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for grinding a revolving work.

[0002]

2. Description of the Related Art A crankshaft used in an engine comprises a cylindrical pin portion and a journal portion connecting each pin portion. As a method of grinding the shaft, there is a method of clamping the journal portions at both ends of the shaft between the left and right headstocks to revolve the pin portion, and moving the grindstone back and forth to contact the rotating grindstone with the pin portion.

FIG. 6 is a diagram showing a positional relationship among a pin portion 14a of a crankshaft 14, a journal portion 14b connected to a main shaft, and a grinding wheel 18 during a grinding operation.
In FIG. 6, P is the rotation center of the grinding wheel 18, L is the revolution center O of the crankshaft 14 and the center O of the pin portion 14a.
The distance to p (revolution radius), θ is the revolving angle of the pin portion 14a with respect to the straight line OP, Rp is the radius of the pin portion 14a, Rg
Represents the whetstone radius. The pin portion 1 in a grinding completed state
Distance Xo between the center of revolution O of 4a and the center of rotation P of the grinding wheel
Is calculated based on the operation formula (a) created from the above-described elements.

Xo = L · cos θ + √ [(Rg + Rp) ² −L ² · sin ² θ] (a) This distance Xo is the finishing wheel head control data Xo of the pin portion 14a, and is shown in FIG. The waveform becomes as shown.

[0005] A pin 1
The distance X is calculated based on the calculation formula (b) obtained by adding the grinding allowance Δx of 4a. The distance X becomes the wheel head control data X for processing, and the pin portion is ground based on the wheel head control data X.

X = L · cos θ + √ [(Rg + Rp) ² −L ² · sin ² θ] + Δx (b) As shown in FIG. 8B, the grinding allowance Δx is set so as to gradually increase from zero. Then, the wheel head control data X has an operation waveform as shown in FIG. 8C in which the grinding allowance Δx is added to the finishing wheel head control data Xo.

[0007]

In the above-mentioned grinding method, the grinding margin Δx is gradually increased and adjusted in order to make the pin portion 14a a finished size. Even if the outer diameter of the pin portion 14a is measured by a sizing device due to a change in the grinding wheel radius Rg or thermal deformation of the grinding machine, the radius Rp may not be a perfect circular shape even if the radius Rp becomes the finishing target radius.

According to the above equation (b), since the grinding allowance Δx is added to the above equation (a) in the relational expression between the rotational position of the pin portion 14a and the position of the grinding wheel head, for example, when the revolution angle θ is 0 degree, The grinding margin is different between the time and the time when the angle is 90 degrees.
Could not secure roundness. That is, when the revolving angle θ is 0 degree, the cutting amount becomes Δx which is the same as the set grinding allowance Δx. However, when the revolving angle θ is 90 degrees, the cutting amount is equal to the rotation center P of the grinding wheel 18 as shown in FIG. Assuming that the inclination angle of the straight line connecting the center Op of the pin portion 14a is α, Δx ′ = Δx
× COSα. As a result, there is a problem that the shape of the pin portion 14a is not actually processed according to the finish data, but becomes elliptical, and the roundness accuracy of the pin portion is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to always grind the workpiece while the grinding operation is stopped with the radius of the grinded part measured by the sizing device being the target radius. An object of the present invention is to provide a method of grinding a revolving work that can ensure roundness of a workpiece.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 is a grinding wheel head which moves back and forth with respect to a cylindrical portion to be ground of a work revolved by a spindle of a headstock. A grinding wheel configured to contact a rotating grindstone supported on a surface to grind a portion to be ground, wherein a distance between a center of revolution (O) of the work and a center (Op) of the portion to be ground is defined as a radius of revolution (L). , The radius of the part to be ground (Rp), the center of rotation (P) of the grinding wheel, the radius of the grinding stone (Rg), the center of the part to be ground relative to the straight line connecting the center of revolution (O) and the center of rotation (P) (O
p) revolution angle (θ), grinding allowance (Δ) for the part to be ground (14a)
x), an arithmetic expression to be calculated as the wheel head control data (X) on the straight line between the orbital center (O) and the rotational center (P) is created by using each of the elements.
The wheel head control position is obtained by an arithmetic expression including (Rg + Rp + Δx) obtained by adding the grinding allowance (Δx) to the distance (Rgp = Rg + Rp) between the rotation center (P) of the grinding wheel and the center (Op) of the portion to be ground. The gist of the present invention is to grind a portion to be ground of a work.

According to a second aspect of the present invention, in the first aspect, an arithmetic expression for obtaining the wheel head control data is represented by X = L ·
cos θ + √ [(Rgp + Δx) ² −L ² · sin ² θ]
The gist is that

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the method of grinding a revolving work of the present invention is embodied in a crankshaft grinder will be described below with reference to FIGS.

FIG. 2 shows the right side of the grinding machine,
, A pair of headstocks 12 are provided at predetermined intervals in a direction orthogonal to the paper surface, and clamp mechanisms 13 are mounted on the spindles 12a of both headstocks 12, respectively. A crankshaft 14 serving as a workpiece clamped by the clamp mechanism 13 includes a plurality of pin portions 14a and a plurality of journal portions 14b connecting the respective pin portions at eccentric positions. The journals 14b at both ends of the crankshaft 14 are clamped by the clamp mechanism 13. The headstock 12 is provided with a servomotor 15 for rotating the spindle 12a.

A grindstone table 17 is mounted on a guide rail 16 laid on the bed 11 so as to be able to reciprocate in a front-rear direction (left-right direction in FIG. 2). A grindstone wheel 18 is rotatable by a motor 19 on the grindstone table 17. It is attached to. A servo motor 20 is fixed to the rear end of the bed 11, and when the ball screw 21 is rotated by the servo motor 20, the grindstone table 17 is moved back and forth via a ball nut (not shown).

The control device 22 for controlling the grinding machine has a control unit 23. The control unit 23 includes a driving circuit 24,
The motors 15, 19 and 20 are connected via 25 and 26.

The control unit 23 includes servo motors 15, 2
0 are connected to the encoders 27 and 28. A signal from one encoder 27 generates a pulse corresponding to the rotation angle of the main shaft 12a, that is, the revolution angle θ of the pin portion 14a. A signal from the other encoder 28 generates a pulse corresponding to the amount of movement of the grindstone table 17. A sizing device 29 is mounted on the grindstone table 17, and the crankshaft 1
The finished shape of the pin portion 14a, that is, the diameter of the pin portion 14a is measured stepwise in the circumferential direction.

The control unit 23 includes a central processing unit (CPU 30) for performing various determinations, arithmetic processing, and the like based on a preset grinding work program, and a preset grinding work program and fixed numerical data. An auxiliary storage device 31 for reading and a random access memory (RAM) 32 capable of writing and reading newly detected numerical data and the like are provided.

Although not shown in the control section 23,
A keyboard and a mouse for inputting various data and a grinding work program are connected, and a display for displaying input data and the like are connected.

Next, a method of grinding the pin portion 14a using the grinding machine configured as described above will be described. First, various elements required for an arithmetic expression used for grinding the pin portion 14a will be described with reference to the diagram of FIG.

In the reference numerals, O is the center of rotation of the main shaft 12a and the center of revolution of the pin portion 14a. P represents the rotation center of the grinding wheel 18, Op represents the center of the pin portion 14a, and X represents the grinding wheel head control position on the straight line between the two centers O and P, respectively. The distance X is calculated using an arithmetic expression of the wheel head control data X as described later, and based on this data, the servo motor 2
The numerical control of 0 is performed to move the grinding wheel 18 back and forth.

L is the distance between the centers O and Op, and represents the revolving radius of the pin portion 14a. Further, Rp is a target radius at the time of finishing (finishing) the pin portion 14a,
Rg represents the radius of the grindstone, and Rgp represents the distance between the centers P and Op. This distance Rgp is equal to the sum of the grinding wheel radius Rg and the finishing target radius Rp of the pin portion.

Rgp = Rg + Rp The radius constantly measured by the sizing device 29 during the grinding of the pin portion 14a uses the actually measured radius Rpx, but this symbol is not shown.

Θ is the angle of the pin portion 14 with respect to a straight line OP connecting the revolution center O of the pin portion 14a and the rotation center P of the grinding wheel 18.
represents the revolution angle of the center Op of a. Δx represents a grinding allowance at the time of grinding the outer peripheral surface of the pin portion 14a.

Here, the input setting operation of the arithmetic expression, various data, and the like in the control device 22 based on the various elements described above will be described. The revolution radius L of the pin portion 14a and the finish target radius Rp of the pin portion 14a are both recorded in the recording medium RAM 32 in advance as constants, not as measured values.

The revolution angle θ of the pin portion 14a is inputted from the encoder 27 of the servomotor 15 to the control unit 23. Since the pin portion 14a is ground by the grinding wheel 18 while revolving with the change of the revolution angle θ, the longitudinal movement of the grinding wheel table 17 is controlled by the numerical control of the servomotor 20 according to the change of the revolution angle θ. The distance X between the centers O and P for controlling the contact between the surface of the pin portion 14a and the surface of the grinding wheel 18 is controlled. Here, the pin 1
The radius of 4a and the radius of the grinding wheel 18 are set in advance. The formula for calculating the distance X is set in the auxiliary storage device 31 in advance as follows. That is, based on the distance Rgp between the centers Op and P obtained by adding the grinding wheel radius Rg to the finishing target radius Rp of the pin portion 14a, and the respective elements of the revolution radius L and the revolution angle θ, the grinding finish of the distance X is performed. Distance X in state
o, that is, the arithmetic expression (1) of the finishing wheel head control data Xo
Is set. The finishing wheel head control data Xo has a left-right symmetric waveform as shown in FIG.

Xo = L · cos θ + √ [(Rgp) ² −L ² · sin ² θ] (1) Next, in the case of processing in consideration of the grinding allowance Δx when actually grinding the pin portion 14a. Formula (2) for the wheel head control data X
Is set.

X = L · cos θ + √ [(Rgp + Δx) ² −L ² · sin ² θ] (2) The grinding allowance Δx is, as shown in FIG.
Each time the number of revolutions of 4a increases by an integral multiple (360 degrees), it gradually increases, and the grinding allowance during one revolution is constant.
For example, it is set to 3 to 10 μm. The entire grinding allowance Δx is set to, for example, 0.1 mm to 1.5 mm. Therefore,
As shown in FIG. 5C, the waveform of the wheel head control data X at the time of machining set by the arithmetic expression (2) is the pin portion 14a.
Have a bilaterally symmetric waveform for each integral multiple of the revolution. or,
Although the idle feed amount of the grindstone head 17 is not represented in the equation (2), it is set to, for example, 30 to 50 mm.

Next, a method of grinding the pin portion 14a of the crankshaft 14 using the grinding machine configured as described above will be described. As shown in FIG. 4, when the grinding of the pin portion is started, the radius Rpx of the pin portion is measured by the sizing device 29. The revolution angle θ of the pin portion 14a is detected by the encoder 27. Then, the grinding wheel head 1 is calculated based on the grinding wheel head control data X calculated based on the arithmetic expression (2).
The servo motor 20 of No. 7 is numerically controlled in synchronization with the main shaft 12a to grind the pin portion 14a.

According to the method of grinding a revolving work of the above embodiment, the following features can be obtained. In the above embodiment, the radius Rp of the pin portion 14a is added to the radius Rg of the grindstone, as shown in the arithmetic expression (2) (Rg + R
A grinding allowance Δx was added to p). For this reason,
If it is determined by the sizing device 29 that the radius of the pin portion 14a has reached the finished size, the pin portion 1a is not removed even if grinding is stopped.
The perfect circle is always maintained without being affected by the rotational position of 4a. That is, as shown in FIG. 5C, the waveform of the wheel head control data X calculated by the calculation formula (2) has a symmetrical shape with the revolution angle θ in units of 360 °. For this reason,
Even if the revolution angle θ of the pin 14a changes, the amount of grinding of the pin 14a does not change. Even when the grinding allowance Δx is half the grinding state, for example, by stopping the number of revolutions of the grinding wheel 18 at an integral multiple rotation, the radius Rpx of the pin portion 14a can be reduced to the finishing target radius Rp + grinding allowance Δ over the entire circumferential direction.
x / 2.

The above embodiment can be modified and embodied as follows. An arithmetic expression other than the arithmetic expression (2) including (Rg + Rp + Δx) obtained by adding the grinding allowance Δx to the distance (Rgp = Rg + Rp) between the rotation center P and the center Op of the pin portion 14a may be used.

(Technical Idea 1) In claim 1 or 2, the grinding allowance Δx is the revolving angle θ of the pin portion 14a (the portion to be ground).
The method of grinding a revolving work is such that is gradually increased in increments of an integral multiple revolution (360 degrees or an integral multiple thereof) and is constant during the integral multiple revolution.

In the technical idea 1, the calculation of the wheel head control data at the time of machining is performed accurately and quickly, and the roundness accuracy of the pin portion can be improved.

[0033]

As described above in detail, according to the present invention, the accuracy of the roundness of the part to be ground is always kept in a state where the part to be ground measured by the sizing device has the finishing target diameter and the grinding operation is stopped. Can be maintained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method of grinding a revolving pin portion of a grinding machine according to an embodiment of the present invention.

FIG. 2 is a right side view of the grinding machine.

FIG. 3 is a block circuit diagram showing a control device of the grinding machine.

FIG. 4 is a flowchart illustrating a grinding method.

FIG. 5 is a graph showing a relationship between a revolution angle and processing profile data.

FIG. 6 is a diagram showing a grinding method of a revolving pin portion of a conventional grinding machine.

FIG. 7 is a diagram illustrating a grinding amount when the revolution angle of the pin portion is 90 degrees.

FIG. 8 is a graph showing a relationship between a revolving angle of a conventional pin portion and processing profile data.

[Explanation of symbols]

θ: revolving angle, L: revolving radius, O: revolving center, P: rotating center of the grinding wheel, X: grinding wheel head control data, Op: center of the portion to be ground, Rg: radius of the grinding wheel, Rp: radius of the portion to be ground, 14a ...
Pin part as a part to be ground, Δx: grinding allowance.

Claims (2)

[Claims] 1. A grinding machine configured to contact a rotating grindstone supported by a grindstone table that moves back and forth with a cylindrical grinding portion of a work revolved by a spindle of a headstock to grind a grinding portion. In the above, the center of revolution (O) of the workpiece and the center (Op) of the portion to be ground.
Is the radius of revolution (L), the radius of the part to be ground (Rp),
The rotation center (P) of the grindstone, the radius (Rg) of the grindstone, the revolving angle (θ) of the center (Op) of the part to be ground with respect to a straight line connecting the center of rotation (O) and the center of rotation (P), the part to be ground (14a) )
If the grinding allowance (Δx) is used, an arithmetic expression to be calculated as the wheel head control data (X) on the straight line between the orbital center (O) and the rotation center (P) is created using the above-described elements, and this arithmetic operation is performed. In the equation, the wheel head control position is calculated by an arithmetic expression including (Rg + Rp + Δx) obtained by adding the grinding allowance (Δx) to the distance (Rgp = Rg + Rp) between the rotation center (P) of the grinding wheel and the center (Op) of the part to be ground. Grinding method for revolving work that grinds the part to be ground of the work. 2. An arithmetic expression for obtaining the wheel head control data (X) according to claim 1, wherein: X = L · cos θ + √ [(Rgp + Δx) ² −L ² · si
n ² θ].