JP2020044607A - Grinding machine - Google Patents

Abstract

To provide a grinding machine that can grind an eccentric part of a workpiece with a high degree of accuracy by suppressing influence of a mechanical assembling error.SOLUTION: A grinding machine 1 comprises a height error memorizing part 32 that registers a height error h showing amplitude of errors in a height direction between a rotary shaft center Wc and a grindstone shaft center Tc, and a profile calculating part 34 calculates profile data in which a movement position (an inter-center distance x) is corrected based on the height error h, so that working accuracy of an eccentric part Wa can be improved. Further, work time required for assembling the grinding machine 1 can be reduced since matching accuracy in the height position between the rotary shaft center Wc and the grindstone shaft center Tc is relaxed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a grinding machine.

  Conventionally, a crankshaft as a work is rotated around a rotation axis that coincides with the center of a journal, and a grindstone is relatively moved in a cutting direction with respect to the work according to the rotation angle to grind a crankpin eccentric from the rotation axis. A grinder is used.

  In a known grinding machine of this type, profile data that defines a moving position of a grindstone at a rotation angle of a rotation axis of a work (for example, an angular position every one degree) is calculated, and grinding is performed according to the profile data. (See, for example, Patent Document 1).

Japanese Patent No. 3821345

  In the profile data described above, the movement position of the grindstone in the cutting direction is calculated on the assumption that the rotational axis of the workpiece and the grindstone axis are in a horizontal positional relationship where the height positions coincide with each other. However, in actuality, since a mechanical assembly error of the grinding machine occurs, a horizontal positional relationship in which the rotation axis and the grinding wheel axis completely coincide with each other in the height direction is not obtained. For this reason, when grinding is performed based on profile data, there is a problem that the processing accuracy of the pin shape, that is, the roundness is reduced due to an error in the height position between the rotation axis and the grinding wheel axis. is there.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a grinding machine capable of grinding an eccentric portion of a work with high accuracy while suppressing the influence of a mechanical assembly error.

  The grinding machine according to the present invention is configured such that, for a work having an eccentric portion eccentric from the rotation axis, a profile calculation unit that calculates profile data defining a rotation angle of the rotation axis and a movement position of the grindstone, and according to the profile data. A control unit that controls the relative movement of the grindstone rotating about the grindstone axis in the cutting direction with respect to the work, and grinding the eccentric part of the work.

  Further, the grinding machine includes a height error amount registration unit that registers a height error amount indicating a magnitude of an error in a height direction between the rotation axis and the grinding wheel axis, and the profile calculation unit includes the height error. The profile data in which the movement position is corrected based on the amount is calculated.

  According to this configuration, since the moving position of the grindstone is corrected based on the height error amount indicating the magnitude of the error in the height direction between the rotation axis and the grindstone axis, the processing accuracy of the eccentric portion can be improved. it can. Further, since the requirement for the accuracy of matching the height position between the rotating shaft center and the grinding wheel shaft center is relaxed, the work time required for assembling the grinding machine can be reduced. Therefore, there is an effect that the eccentric portion of the work can be ground with high accuracy while suppressing the influence of the mechanical assembly error.

It is a top view showing the whole composition of the grinding machine concerning a 1st embodiment. It is a block diagram showing a CNC device concerning a 1st embodiment. It is explanatory drawing which shows the ideal positional relationship between a workpiece and a grindstone. It is explanatory drawing which shows the actual positional relationship between a workpiece and a grindstone. FIG. 4 is an explanatory diagram illustrating a positional relationship between a work and a grindstone and calculation of profile data. It is a block diagram showing a CNC device concerning a 2nd embodiment. FIG. 4 is an explanatory diagram illustrating a positional relationship between a work and a grindstone, and calculation of theoretical profile data and correction profile data.

  Hereinafter, embodiments of a grinding machine embodying the present invention will be described with reference to the drawings.

<First embodiment>
(1. Overall configuration of grinding machine 1)
The configuration of the grinding machine 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a plan view showing the overall configuration of the grinding machine 1 according to the first embodiment. The grinder 1 is a grinder for processing the work W. The work W is a shaft-shaped member and has an eccentric portion Wa. The eccentric portion Wa is a portion centered on an axis eccentric to the rotation axis of the workpiece W. In particular, the eccentric portion Wa has a cylindrical outer peripheral surface, and the center axis of the eccentric portion Wa is eccentric with respect to the rotation axis of the work.

  In the present embodiment, a crankshaft is taken as an example of the work W. However, the work W is not limited to the crankshaft. The workpiece W, which is a crankshaft, includes a crankpin as an eccentric portion Wa. In FIG. 1, for example, a crankshaft (work W) includes four crank pins (eccentric portions Wa). The axis of rotation of the crankshaft coincides with the center axis of the crank journal. The grinder 1 grinds the outer peripheral surface of the crankpin, which is the eccentric portion Wa, while rotating the work W about the C axis, which is the rotation axis.

  The grinding machine 1 exemplifies a grindstone traverse type. However, a table traverse type can also be applied to the grinding machine 1. The grinding machine 1 has a configuration in which only one disc-shaped grindstone 17 is provided, but a configuration in which two grindstones 17 are provided can also be applied.

  The grinding machine 1 includes a bed 11, a headstock 12, a chuck 13, a tailstock 14, a traverse base 15, a grindstone 16, a grindstone 17, a drive unit 20, and a CNC device 30.

  The bed 11 is fixed on the installation surface. On the upper surface of the bed 11, a guide rail 11a extending in the Z-axis direction is formed. On the upper surface of the bed 11, a ball screw 11b extending in a direction parallel to the Z-axis direction, and a Z-axis feed motor 11c that rotationally drives the ball screw 11b are provided.

  The headstock 12 functions as a support device that rotatably supports the work W. The headstock 12 is provided on the upper surface of the bed 11 on the near side in the X-axis direction and on one end side (front end side) in the Z-axis direction. The headstock 12 includes a spindle center 12a rotatable around the C axis, and a spindle motor 12b that drives the spindle center 12a to rotate. The spindle center 12a supports the center of one end of the work W.

  The chuck 13 is provided on an end face of the headstock 12, and is driven to rotate by a spindle motor 12b. The chuck 13 grips the outer peripheral surface of one end of the work W. That is, the chuck 13 rotates together with the spindle center 12a while rotatably supporting the work W.

  The tailstock 14 is located on the upper surface of the bed 11 at a position facing the headstock 12 in the Z-axis direction, that is, the near side in the X-axis direction (the lower side in FIG. 1) and the other end in the Z-axis direction ( 1 (left side in FIG. 1). The tailstock 14 includes a tailstock center 14a that supports the center of the other end of the work W. Note that the tailstock center 14a may be provided so as to rotate with the work W, or may be provided so as to slide on the work W without rotating.

  The traverse base 15 is provided on the guide rail 11a so as to be movable in the Z-axis direction. The traverse base 15 is fixed to a nut of the ball screw 11b, and moves in the Z-axis direction by driving a Z-axis feed motor 11c. On the upper surface of the traverse base 15, a guide rail 15a extending in the X-axis direction orthogonal to the Z-axis direction is formed. On the upper surface of the traverse base 15, a ball screw 15b extending in a direction parallel to the X-axis direction, and an X-axis feed motor 15c for rotating and driving the ball screw 15b are provided. The traverse base 15 may be driven by a linear motor instead of being driven by the ball screw 15b and the X-axis feed motor 15c in the X-axis direction.

  The grindstone table 16 is provided on the guide rail 15a of the traverse base 15 so as to be linearly movable in the X-axis direction which is the cutting direction of the grindstone 17 with respect to the work W. The wheel head 16 moves in the X-axis direction by the rotation of the X-axis feed motor 15c. The grindstone table 16 supports a disc-shaped grindstone 17 as a tool so as to be rotatable around the Z axis. The grindstone table 16 is provided with a cover 16a for covering the other parts while exposing the grinding part of the grindstone 17. Further, the grindstone table 16 includes a grindstone rotation motor 16b that drives the grindstone 17 to rotate.

  The drive unit 20 is a drive circuit that drives each of the above-described motors based on a control command from the CNC device 30. The drive unit 20 includes a motor drive circuit 21 for rotating a grindstone, a motor drive circuit 22 for X-axis feed, and a Z-axis feed And a main shaft motor drive circuit 24.

  The grindstone rotation motor drive circuit 21 rotates the grindstone rotation motor 16b to rotate the grindstone 17. The X-axis feed motor drive circuit 22 rotationally drives the X-axis feed motor 15c to move the grindstone table 16 in the X-axis direction, which is the cutting direction of the grindstone 17 with respect to the work W. The Z-axis feed motor drive circuit 23 rotates the Z-axis feed motor 11c to move the traverse base 15 in the Z-axis direction. The spindle motor drive circuit 24 drives the spindle motor 12b to rotate, and rotates the work W about the C axis together with the spindle center 12a.

(2. Configuration of CNC device 30)
Next, the configuration of the CNC device 30 will be described with reference to FIG. FIG. 2 is a block diagram illustrating the CNC device 30 according to the first embodiment. The CNC device 30 is a computer numerical control device that issues a control command to the drive unit 20, and as shown in FIG. 2, an NC program storage unit 31, a height error storage unit 32, various data storage units 33, a profile It comprises an arithmetic unit 34 and a control unit 35.

  The NC program storage unit 31 is a storage area for storing the NC program, and externally inputs and registers, that is, stores, the NC program for processing the work W. The NC program includes a code consisting of a single letter alphabet followed by a numeral, and includes a G code for processing the movement of the spindle, setting of the coordinate system, and the like as one of the codes. The G code includes a code G00 indicating fast-forward, a code G01 indicating processing feed, a G106 indicating profile calculation, and the like.

  The height error storage unit 32 is a storage area for registering, that is, storing a height error input from the outside. Here, the height error will be described with reference to FIGS. FIG. 3 shows an ideal positional relationship between the work W and the grindstone 17, and FIG. 4 shows an actual positional relationship between the work W and the grindstone 17.

  As shown in FIG. 3, in an ideal positional relationship, the rotational axis Wc of the work W and the grindstone axis Tc of the grindstone 17 have a horizontal positional relationship in which the height positions coincide. However, actually, due to a mechanical assembly error, as shown in FIG. 4, the rotational axis Wc of the workpiece W and the grindstone axis Tc of the grindstone 17 are displaced by about several tens of μm in the height position. That is common. In this specification, the deviation of the height position between the rotation axis Wc and the grinding wheel axis Tc is referred to as a height error. The height error is measured using a measuring device at the time of assembling and manufacturing the individual grinding machines 1, and the measured value is registered, that is, stored in the height error storage unit 32 as a height error unique to the grinding machine. The various data storage unit 33 is a storage area that stores various data used for processing control.

  The profile calculator 34 calculates profile data using the height error amount h based on the NC program. The profile data includes the rotation angle θ of the rotation axis Wc of the work W (for example, an angular position every one degree) and the movement position of the grindstone 17 corresponding to each rotation angle (the rotation axis Wc and the grinding wheel axis Tc). This is point cloud data that defines an inter-center distance x). Hereinafter, a method of calculating the distance between centers x in the profile calculation unit 34 will be described with reference to FIG. FIG. 5 is an explanatory diagram illustrating the positional relationship between the workpiece W and the grindstone 17 and the calculation of the profile data.

The radius (1/2 of the pin stroke) of the rotation trajectory of the crankpin axis which is the eccentric portion center Wac is L, the radius of the grindstone 17 (1/2 of the grindstone diameter) is R, and the crank which is the eccentric portion Wa. Assuming that the radius of the pin (直径 of the diameter of the pin) is h, the height error amount is h, and the rotation angle of the rotation axis Wc of the workpiece W is θ, the following relational expression is established geometrically.
α = tan ^-1 (h / x)
y ² = x ² + h ²
y ² + L ² -2Lycos (π−θ + α) = (r + R) ²

Then, the center distance x is calculated by the following equation derived from the above relational equation.
A = (r + R) ² − (L sin θ) ²
x = −Lcos θ + √A
In this manner, based on the geometric relationship between the workpiece W and the grinding wheel 17, the rotation angle theta ₀ axis of rotation Wc, theta _1, between heart against theta ₂ · · · distance x _0, x _1, x ₂ Can be obtained by calculation.
In this manner, profile data representing the center-to-center distances x ₀ , x ₁ , x ₂ ... With respect to the rotation angles θ ₀ , θ ₁ , θ ₂ .

  Then, the control unit 35 controls each drive circuit of the drive unit 20 based on the profile data. That is, the Z-axis feed motor drive circuit 23 rotates the Z-axis feed motor 11c to move the traverse base 15 in the Z-axis direction, so that the grindstone 17 faces the crankpin, which is the eccentric portion Wa. The spindle motor 12b is driven to rotate by the spindle motor drive circuit 24 to rotate the work W about the C axis together with the spindle center 12a. Further, the X-axis feed motor drive circuit 22 drives the X-axis feed motor 15c to rotate the X-axis feed motor 15c in the X-axis direction in accordance with the rotation angle of the spindle center 12a which is the rotation axis of the work W. . Then, the grindstone rotating motor drive circuit 21 rotates and drives the grindstone rotating motor 16b to rotate the grindstone 17, whereby the crankpin as the eccentric portion Wa is ground.

(3. Summary)
As described above, the grinding machine 1 includes the height error storage unit 32 that registers the height error amount h indicating the magnitude of the error in the height direction between the rotation axis Wc and the grinding wheel axis Tc, and the profile calculation unit 34 Calculates profile data in which the moving position (center-to-center distance x) is corrected based on the height error amount h, so that the processing accuracy of the eccentric portion Wa can be improved. Further, since the requirement for the accuracy of matching the height position between the rotation axis Wc and the grinding wheel axis Tc is relaxed, the working time required for assembling the grinding machine 1 can be reduced. Therefore, there is an effect that the eccentric portion Wa of the work W can be ground with high accuracy while suppressing the influence of the mechanical assembly error.

<Second embodiment>
Next, a grinding machine 1 according to a second embodiment will be described with reference to FIGS. Hereinafter, the description will focus on the differences from the first embodiment. FIG. 6 is a block diagram illustrating the CNC device 30 according to the second embodiment, and FIG. 7 is an explanatory diagram illustrating the positional relationship between the workpiece W and the grindstone 17 and the calculation of the theoretical profile data and the correction profile data. . The same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

  In the second embodiment, in addition to the above-described height error amount, profile calculation is performed using measurement error data obtained by measuring a test-ground workpiece W with a measuring device. Specifically, as shown in FIG. 6, the CNC device 30 of the grinding machine 1 according to the second embodiment includes an NC program storage unit 31, a height error storage unit 32, various data storage units 33, and a theoretical profile calculation. A measurement error storage unit 36 and a correction profile calculation unit 37 are provided in addition to the unit 34 and the control unit 35.

The measurement error storage unit 36 is a storage area for storing measurement error data obtained by measuring the test-ground workpiece W with the measuring device 40. That is, in the grinding of the crank pin, which is the eccentric portion Wa of the work W, in addition to the above-described mechanical assembly error, an error occurs in the moving amount of the grindstone due to the dynamic pressure of the coolant supplied to the grinding portion. This may affect the roundness of the crankpin, which is Wa. In the CNC device 30 of the present embodiment, the pin diameter of the crankpin, which is the eccentric portion Wa of the work W that has been trial-ground by the grinding machine 1, is measured by the measuring device 40, and the resulting measurement error data is stored in the measurement error storage unit. 36, that is, stored in advance. The measurement error data is data of the error Δr of the pin radius with respect to the rotation angle (pin angle) β of the center Wac of the eccentric part, and the errors r ₀ , r ₁ , and r _{2 with} respect to the pin angles β ₀ , β ₁ , β ₂ . consisting of r ₂ ··· of data.

  The theoretical profile calculation unit 34 calculates profile data using the height error amount h based on the NC program. The theoretical profile calculation unit 34 performs the same calculation as the profile calculation unit 34 in the first embodiment, and a detailed description is omitted.

The correction profile calculation unit 37 calculates correction profile data by correcting the theoretical profile data calculated by the theoretical profile calculation unit 34 based on the measurement error data stored in the measurement error storage unit 36. The outline of the calculation is that the data of the error Δr is converted into the correction amount of x, that is, the measurement error data representing the correction amounts Δx ₀ , Δx ₁ , Δx ₂ ... For the rotation angles θ ₀ , θ ₁ , θ _2. Are converted, and the theoretical profile data is corrected using the converted values. The center distances x ₀ −Δx ₀ , x ₁ −Δx ₁ , x ₂ −Δx ₂ ... With respect to the rotation angles θ ₀ , θ ₁ , θ _2. Create correction profile data representing

Specifically, the following calculation is performed. First, the target calculation angle β _{n is obtained} by the following equation.
When L ≧ 0.000001,
α _n = cos ⁻¹ [{L ² + (r + R) ² − (x ² + h ² )} / 2L (r + R)]
K ₂ = sin ^-1 [-h / {L + (r + R)}
K ₃ = sin ^-1 [-h / {L- (r + R)}
K ₃ > 0
... 0 ≦ θ _n <K ₃ → β _n = −α _n
... K ₃ ≦ θ _n <180−K ₂ → β _n = α _n
... 180−K ₂ ≦ θ _n ≦ 360 → β _n = 360−α _n
K ₃ ≦ 0
... 0 ≦ θ _n <180−K ₂ → β _n = α _n
... 180−K ₂ ≦ θ _n <360 + K ₃ → β _n = 360−α _n
... 360 + K ₃ ≤θ _n ≤360 → β _n = 360 + α _n
When L <0.000001, the following is performed to prevent division by 0.
β _n = tan ^-1 {h / (r + R)} + θ _n

Next, the corrected center distance x is calculated by the following equation. Note that rRevis is the rotation angle of the eccentric portion center Wac (corresponding to the rotation angle β in FIG. 7), and pGosa is the measurement error at the rotation angle rRevis (corresponding to the error Δr in FIG. 7).
C = {(r + R) -pGosa}
x = {L ² + C ² -2LCcos (rRevis) -h ² }
In this manner, based on the geometric relationship between the workpiece W and the grinding wheel 17, the rotation angle theta ₀ axis of rotation Wc, theta _1, between heart against theta ₂ · · · distance x _0, x _1, x ₂ .. Can be obtained by calculation.

  Then, the control unit 35 controls each drive circuit of the drive unit 20 based on the correction profile data. That is, the Z-axis feed motor drive circuit 23 rotates the Z-axis feed motor 11c to move the traverse base 15 in the Z-axis direction, so that the grindstone 17 faces the crankpin, which is the eccentric portion Wa. The spindle motor 12b is driven to rotate by the spindle motor drive circuit 24 to rotate the work W about the C axis together with the spindle center 12a. Further, the X-axis feed motor drive circuit 22 rotates the X-axis feed motor 15c according to the rotation angle of the spindle center 12a, which is the rotation axis of the workpiece W, to move the grindstone table 16 in the X-axis direction. . Then, the grindstone rotating motor drive circuit 21 rotates the grindstone rotating motor 16b to rotate the grindstone 17, whereby the crankpin as the eccentric portion Wa is ground.

  According to the grinding machine 1 of the present embodiment, in addition to the height error amount h, the theoretical profile data is obtained by using the measurement error data obtained by measuring the diameter of the eccentric portion Wa of the test-ground workpiece W with the measuring device. Is calculated. Therefore, in addition to the mechanical assembling error, the positional deviation of the grindstone 17 due to the dynamic pressure of the coolant and the like is corrected, and the effect that the processing accuracy of the eccentric portion Wa can be further improved.

<Modification>
The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the gist of the present invention. In the above embodiment, an example is shown in which the present invention is applied to a grinding machine for grinding a crankpin of a crankshaft, but the invention is not limited to this. For example, the present invention is also applicable to a cam grinder for grinding a camshaft. In short, the present invention can be applied to a grinding machine for grinding a work having an eccentric portion eccentric from the rotation axis.

W: Work, Wc: Rotation axis, Wa: Eccentric part, Wac: Eccentric part center, Tc: Grinding wheel axis, 1: Grinding machine, 17: Grinding stone, 32: Height error storage unit, 34: Profile calculation unit, theory Profile calculation unit, 35: control unit, 36: measurement error storage unit, 37: correction profile calculation unit

Claims (4)

A profile calculation unit configured to calculate profile data defining a rotation angle of the rotation axis and a movement position of the grinding wheel with respect to a work having an eccentric part eccentric from the rotation axis, and rotating around the grinding wheel axis according to the profile data. A control unit that performs control to relatively move the grindstone in the cutting direction with respect to the work, a grinding machine that grinds the eccentric part of the work,
A height error storage unit that stores a height error amount indicating a magnitude of an error in a height direction between the rotation axis and the grinding wheel axis,
The grinding machine, wherein the profile calculation unit calculates the profile data in which the movement position is corrected based on the height error amount. 2. The grinding machine according to claim 1, wherein the profile calculation unit calculates a center distance x between the rotation axis and the grinding wheel axis by the following equation. 3.
A = (r + R) ² − (L sin θ) ²
x = −Lcos θ + √A
Here, L is the radius of the rotation locus of the center of the eccentric portion, R is the radius of the grinding wheel, r is the radius of the eccentric portion, θ is the rotation angle of the rotation axis (0 ≦ θ ≦ 2π), and h is the height error. The value is a positive value when the wheel axis is above the ideal position, and a negative value when it is below the ideal position. A measurement error storage unit that stores measurement error data obtained by measuring the eccentric portion of the test-ground workpiece with a measuring device,
The profile calculation unit calculates a theoretical profile data in which the moving position is corrected based on the height error amount, and a corrected profile data in which the theoretical profile data is corrected based on the measurement error data. The grinding machine according to claim 1, further comprising a correction profile calculation unit that performs the correction profile calculation. 4. The grinding machine according to claim 3, wherein the correction profile calculator calculates a center distance x between the rotation axis and the grinding wheel axis based on the measurement error data using the following equation.
C = {(r + R) -pGosa}
x = {L ² + C ² -2LCcos (rRevis) -h ² }
Here, L is the radius of the rotation locus of the center of the eccentric part, R is the radius of the grinding wheel, r is the radius of the eccentric part, rRevis is the rotation angle of the center of the eccentric part, pGosa is the measurement error at the rotation angle rRevis, h Is the height error amount, where the value when the grinding wheel axis is above the ideal position is a positive value, and the value when it is below the ideal position is a negative value.

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