JP2014226741A - Grinder, and grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinder and a grinding method capable of making the roundness highly accurate in retraction grinding.SOLUTION: There is performed a forward movement grinding, in which an abrasive wheel 15 is relatively moved forward to a workpiece Wa, and, subsequently of the forward movement grinding, there is performed a backward movement grinding, in which the abrasive wheel 15 is relatively moved backward from the workpiece Wa. The depression quantity εb(θ) of the workpiece Wa in the retraction grinding according to the phase (θ) of the workpiece Wa is estimated, and the retraction grinding is performed on the basis of the depression quantity εb(θ) in the estimated retraction grinding.

Description

  The present invention relates to a grinding machine and a grinding method.

  In Japanese Patent Laid-Open No. 2000-218479 (Patent Document 1), in cylindrical grinding, the roundness of a workpiece is measured, a correction amount is created based on the roundness error, and the correction amount is corrected. Grinding is described. Further, when the crankpin is ground, the amount of bending of the crankpin changes due to the rigidity of the crankpin being different depending on the rotational phase of the crank journal.

  Therefore, Japanese Patent Application Laid-Open No. 2000-107902 (Patent Document 2) and Japanese Patent Application Laid-Open No. 11-90800 (Patent Document 3) disclose a correction amount based on the amount of deflection caused by the rigidity of the crankpin depending on the rotational phase. And grinding while correcting with the correction amount. Thereby, the roundness of a crankpin can be made highly accurate.

  Also, as a method of grinding a workpiece, Japanese Patent Application Laid-Open No. 2011-093017 discloses performing reverse grinding in which grinding is performed while the grinding wheel is moved backward with respect to the workpiece after rough grinding, and finish grinding is performed after reverse grinding. Gazette (patent document 4) and JP 2011-140089 (patent document 5).

JP 2000-218479 A JP 2000-107902 A JP-A-11-90800 JP 2011-093017 A JP 2011-140089 A

  Also in the reverse grinding, if the roundness of the workpiece can be made highly accurate, it becomes possible to obtain a highly accurate workpiece while reducing the grinding time. Here, in the rough grinding in which the grinding wheel is advanced, the cutting amount is made constant in the steady state. On the other hand, in the reverse grinding, the workpiece is ground while the grinding wheel is moved backward, so that the cutting amount gradually changes. Due to the difference in the depth of cut, the amount of deflection in reverse grinding differs from the amount of deflection in rough grinding. Therefore, the correction methods described in Patent Documents 2 and 3 cannot be applied as they are when performing backward grinding. That is, it is not easy to make the roundness highly accurate in the reverse grinding.

  This invention is made | formed in view of such a situation, and it aims at providing the grinding machine and grinding method which can make roundness highly accurate in reverse grinding.

(Grinder)
(Claim 1) A grinding machine according to the present means performs forward grinding for relatively advancing the grinding wheel toward the workpiece, and relatively retracts the grinding wheel from the workpiece following the forward grinding. A grinding machine for performing reverse grinding, wherein a deflection amount εb (θ) of the workpiece in the backward grinding according to the phase θ of the workpiece is estimated, and the deflection amount εb (θ) in the backward grinding is calculated. Based on this, the backward grinding is performed.

Below, the preferable aspect of the grinding machine which concerns on this means is described.
(Claim 2) Preferably, the deflection amount εb (θ) in the backward grinding is equal to the deflection amount εa (θ) of the workpiece in the forward grinding according to the phase θ of the workpiece, and the forward grinding. Is estimated on the basis of the grinding resistance Fna (θ0e) at the phase θ0e at the end of and the target cutting amount d (θ) from the start to the end of the backward grinding.

(Claim 3) Preferably, the grinding machine controls a position of the grinding wheel with respect to the workpiece based on a position command value in the forward grinding, and in the backward grinding. A basic retraction amount ΔX _master (θ) as a position command value, a deflection amount εa (θ) of the workpiece in the forward grinding according to the phase θ of the workpiece, and a deflection amount εb (θ in the backward grinding ) difference based on the [Delta] [epsilon] _ab (theta) between the in the retraction grinding control unit for controlling the position of said grinding wheel relative to the workpiece, the deflection in the forward grinding during the forward grinding amount .epsilon.a (theta) Correcting the control by the forward grinding control unit based on, and a correction unit for correcting the control by the backward grinding control unit based on the deflection amount εa (θ) in the forward grinding during the backward grinding, Prepare.

(Claim 4) Preferably, the grinding machine controls a position of the grinding wheel relative to the workpiece based on a position command value in the forward grinding, and in the backward grinding. Based on a basic retraction amount ΔX _master (θ) as a position command value, a reverse grinding control unit that controls the position of the grinding wheel with respect to the workpiece, and according to the phase θ of the workpiece during the forward grinding Further, a correction for the control by the forward grinding control unit is performed based on the deflection amount εa (θ) of the workpiece in the forward grinding, and based on the deflection amount εb (θ) in the backward grinding during the backward grinding. And a correction unit for correcting the control by the backward grinding control unit.

(Grinding method)
The present invention can be grasped as a grinding method in addition to the above-described grinding machine.
(Claim 5) The grinding method according to the present means performs forward grinding for relatively advancing the grinding wheel toward the workpiece, and relatively retracts the grinding wheel from the workpiece following the forward grinding. A grinding method for performing reverse grinding, wherein a deflection amount εb (θ) of the workpiece in the backward grinding according to the phase θ of the workpiece is estimated, and the deflection amount εb (θ) in the backward grinding is calculated. Based on this, the backward grinding is performed.

  (Claims 1 and 5) According to this means, the backward grinding is performed based on the deflection amount εb (θ) in the backward grinding. Therefore, the roundness of the workpiece in the reverse grinding can be made highly accurate. Here, the reverse grinding is performed while the workpiece is rotated once or several times. For this reason, it is not easy to obtain the amount of deflection εb (θ) in the reverse grinding during the backward grinding. Therefore, the amount of deflection εb (θ) in the backward grinding is estimated. That is, the backward grinding is performed based on the estimated deflection amount εb (θ) in the backward grinding.

  (Claim 2) Here, the present inventors have found that the amount of deflection εa (θ) in forward grinding is different from the amount of deflection εb (θ) in backward grinding, but there is a correlation between them. Therefore, the deflection amount εb (θ) in the backward grinding can be estimated based on the deflection amount εa (θ) in the forward grinding.

  Further, the deflection amount εa (θ) in forward grinding can be acquired during forward grinding. Therefore, the deflection amount εb (θ) in the backward grinding can be reliably obtained by estimating based on the deflection amount εa (θ) in the forward grinding.

  Further, in the reverse grinding, the cutting amount is gradually decreased during that time. The amount of deflection εb (θ) in the reverse grinding changes in accordance with the depth of cut. That is, the deflection amount εb (θ) in the reverse grinding depends on the cutting amount. Therefore, the amount of bending εb (θ) in the reverse grinding is not limited to the amount of bending εa (θ) in the forward grinding, the grinding resistance Fnb (θ0e) at the phase θ0e at the end of the forward grinding and the target cutting amount d in the backward grinding. By using (θ), it can be reliably estimated.

(Claim 3) The correction by the correction unit in the backward grinding is performed based on the deflection amount εa (θ) in the forward grinding as in the forward grinding. Therefore, the correction process by the correction unit can be the same process in the backward grinding and the forward grinding. However, if the above correction is performed in the reverse grinding, an excessive correction is performed. Accordingly, the reverse grinding control unit performs position control in consideration of the deflection amount difference Δε _ab (θ) in addition to the basic reverse amount ΔX _master (θ). By doing so, the workpiece can be surely made to have a high accuracy roundness in the backward grinding.

(Claim 4) Unlike the forward grinding, the correction by the correction unit in the backward grinding is performed based on the deflection amount εb (θ) in the backward grinding. By doing in this way, in backward grinding, a work can be surely made into highly accurate roundness. In this case, the reverse grinding control unit performs control based on the basic reverse amount ΔX _master (θ).

It is a top view of the grinding machine 1 in embodiment of this invention. When the phase θ of the crankshaft W is 0 °, it is a diagram showing the positional relationship between the rotation center O of the crankshaft W, the pin center Ow of the crankpin Wa, and the grinding wheel 15. However, it is illustrated that the crankshaft W is not bent. When the phase θ of the crankshaft W is 90 °, it is a diagram showing the positional relationship between the rotation center O of the crankshaft W, the pin center Ow of the crankpin Wa, and the grinding wheel 15. When the phase θ of the crankshaft W is 180 °, it is a diagram showing the positional relationship between the rotation center O of the crankshaft W, the pin center Ow of the crankpin Wa, and the grinding wheel 15. When the phase θ of the crankshaft W is 270 °, it is a diagram showing the positional relationship between the rotation center O of the crankshaft W, the pin center Ow of the crankpin Wa, and the grinding wheel 15. In the upper part, the X axis position of the grinding wheel 15, the outer diameter Dt of the crankshaft W, and in the lower part, a graph showing changes over time in the coolant supply amount Q. The crankpin Wa and the grinding wheel 15 at the start time T0s of the rough forward grinding in FIG. 3 are shown. The crankpin Wa and the grinding wheel 15 at the time T1s (= T0e) at the start of backward grinding in FIG. 3 are shown. The crankpin Wa and the grinding wheel 15 at the end T1e (= the start time T2s of the back-off operation) in FIG. 3 are shown. The functional block block diagram of the grinding machine 1 in this embodiment is shown. It is a flowchart which shows the correction process by the correction | amendment part 182 in 1st embodiment. FIG. 10 is a block diagram illustrating a procedure for calculating a first correction amount D1 (θ) by a correction unit 182. The relationship between the grinding efficiency Zreal and the actual pressing force Freal in the cutting direction that the crank pin Wa receives from the grinding wheel 15 is shown. The grinding point speed v (θ) corresponding to the rotational phase θ of the crankshaft W is shown. A theoretical grinding efficiency Zlogical (θ) corresponding to the rotational phase θ of the crankshaft W is shown. The pressing force Fa (θ) in the cutting direction received by the crank pin from the grinding wheel, the grinding resistance Fna (θ), and the coolant dynamic pressure Fp (θ) according to the rotational phase θ of the crankshaft W are shown. A deflection amount εa (θ) is shown in accordance with the rotational phase θ of the crankshaft W. A first correction amount D1 (θ) corresponding to the rotational phase θ of the crankshaft W is shown. It is a flowchart which shows the calculation procedure of the 2nd correction amount D2 by the correction | amendment part 182 in 1st embodiment. It is a block diagram which shows the calculation procedure of reverse | retreat amount (DELTA) X by the basic grinding control part 181 as a backward grinding control part in 1st embodiment. The target cutting amount d (θ) from the start to the end of the reverse grinding is shown. The grinding resistance Fnb (θ) in reverse grinding and the grinding resistance Fna (θ) in rough forward grinding are shown. The coolant dynamic pressure Fp (θ) in the reverse grinding is shown. The pressing force Fb (θ) in backward grinding and the pressing force Fa (θ) in rough forward grinding are shown. A total deflection amount εb (θ) in reverse grinding, a deflection amount εna (θ) due to grinding resistance in rough forward grinding, and a total deflection amount εa (θ) are shown. A deflection amount difference Δε _ab (θ) is shown. In the first embodiment, a basic retraction amount ΔX _master (θ) and a retraction amount ΔX in reverse grinding are shown. It is a flowchart which shows the process by the basic grinding control part 181 as a backward grinding control part in 2nd embodiment. In the second embodiment, a basic retraction amount ΔX _master (θ) in reverse grinding is shown. It is a flowchart which shows the correction process by the correction | amendment part 182 in 2nd embodiment. A third correction amount D3 (θ) corresponding to the rotational phase θ of the crankshaft W in the reverse grinding is shown.

Embodiments to which a grinding machine and a grinding method according to the present invention are applied will be described below.
<First embodiment>
(1. Configuration of grinding machine)
A grinding wheel traverse type cylindrical grinder will be described as an example of the grinder of this embodiment. However, for example, a table traverse type grinding machine can be applied to the grinding machine according to the present invention. Further, the workpiece to be processed by the grinding machine is exemplified by the crankshaft W, and the grinding portion is a crank pin (eccentric cylindrical portion) Wa. Further, a recess A (shown in FIG. 2C) such as an oil hole is formed in the crank pin Wa which is a grinding surface of the workpiece. For example, the oil hole is formed to penetrate in the radial direction. Note that the workpiece is not limited to the crankshaft, and any workpiece having a different amount of deflection according to the phase θ can be applied.

  The grinding machine will be described with reference to FIG. The grinding machine 1 is configured as follows. A bed 11 is fixed on the floor, and a main shaft 12 and a tailstock device 13 that support the crankshaft W at both ends in a rotatable manner are attached to the bed 11. The crankshaft W is supported by the main shaft 12 and the tailstock device 13 so as to rotate around the journal. That is, the crank pin Wa which is a grinding part has a circular shape centered on a position eccentric from the rotation center. The main shaft 12 is driven by a drive motor 12a, and the phase θ of the main shaft 12 is detected by a rotation detector 12b.

  Furthermore, on the bed 11, a grindstone base 14 that is movable in the Z-axis direction and the X-axis direction is provided. The grinding wheel base 14 is driven in the X-axis direction by the drive motor 14a, and the position detector 14b in the X-axis direction of the grinding wheel base 14 detects the position of the grinding wheel base 14 in the X direction. The position detector 14b is a rotation detector or a linear scale. The grinding wheel base 14 is rotatably supported by a grinding wheel 15 and is provided with a coolant nozzle 19 (shown in FIGS. 2A to 2D) for supplying coolant toward a grinding point.

  Further, the main shaft 12 is provided with a force sensor 16 that measures a force (a pressing force in the cutting direction) F of the X-axis direction component applied to the main shaft 12. Further, the bed 11 is provided with a sizing device 17 for measuring the diameter of the crankpin Wa. Further, the grinding machine 1 is provided with a control device 18 that rotates the spindle 12 and the grinding wheel 15 and controls the position of the grinding wheel 15 with respect to the crankshaft W.

(2. Explanation of position of crank pin and grinding wheel)
As described above, the crank pin Wa, which is a grinding part, has a circular shape centered on a position eccentric from the rotation center. 2A to 2D, the rotation center O of the crankshaft W and the position of the pin center Ow corresponding to the phase θ of the crankshaft W will be described. However, in FIGS. 2A to 2D, the crankshaft W is illustrated as not being bent and deformed. Moreover, in FIG. 2A-FIG. 2D, the coolant nozzle 19 and the grinding point P are illustrated. The coolant nozzle 19 is provided above the grinding point P in the grinding wheel base 14.

  When the phase θ is 0 °, the pin center Ow is located on the opposite side of the grinding wheel 15 with respect to the rotation center O (the cutting direction by the grinding wheel 15), as shown in FIG. 2A. The coolant is supplied from the upper side of the grinding wheel 15 toward the grinding point P. When the phase θ is 90 °, the pin center Ow is positioned below the rotation center O as shown in FIG. 2B. When the phase θ is 180 °, as shown in FIG. 2C, the pin center Ow is located on the grinding wheel 15 side (anti-cutting direction) with respect to the rotation center O. When the phase θ is 270 °, the pin center Ow is located above the rotation center O as shown in FIG. 2D.

(3. Outline of grinding method)
Next, an outline of the grinding method in the present embodiment will be described with reference to FIGS. 3 and 4A to 4C. Here, in FIGS. 4A to 4C, Os is a pin center Ow (referred to as a temporary pin center) when it is assumed that the crankshaft W is not bent. Or is an actual pin center Ow (referred to as an actual pin center). That is, as shown in FIGS. 4A to 4C, Os and Or are deviated in a state where the crankshaft W is bent.

  In this embodiment, rough forward grinding → reverse grinding → back-off operation → finish forward grinding → spark out. In each grinding process, coolant is always supplied. Here, the coolant supply amount Q is set to a large flow rate Qmax during rough forward grinding and reverse grinding, and the coolant supply amount Q is set to a small flow rate Qmin during finish forward grinding and spark-out. This will be described in detail below.

  First, the control device 18 advances the grinding wheel 15 in the X-axis direction with respect to the crankshaft W to start rough forward grinding (T0s to T0e in FIG. 3). In rough forward grinding, as indicated by T0s to T0e in the upper stage of FIG. 3, the grinding wheel 15 moves forward at a constant speed in the minus direction of the X axis (cutting direction). That is, in rough forward grinding, the grinding wheel 15 is relatively moved in the direction of pressing against the crank pin Wa. Here, in the rough forward grinding, in order to increase the grinding efficiency Z (the amount of grinding per unit time unit width), the moving speed is increased as compared with the finish forward grinding. That is, the time change of the X-axis position of the grinding wheel 15 from T0s to T0e in FIG. 3 is large.

  Then, at the time T0s at the start of rough forward grinding in FIG. 3, as shown in FIG. 4A, the actual pin center Or is displaced from the temporary pin center Os by a deflection amount εp (θ0s) due to the coolant dynamic pressure Fp (θ0s). ing. When the grinding wheel 15 is pressed against the crank pin Wa from this state, the crank pin Wa is ground while the crank pin Wa is further bent. The grinding resistance Fna (θ) increases until the time T0e at the end of rough forward grinding in FIG. That is, the sum of the coolant dynamic pressure Fp (θ) and the grinding resistance Fna (θ) acts on the pressing force Fa (θ) received by the crank pin Wa from the grinding wheel 15.

  As shown in FIG. 4B, the total deflection amount εa (θ0e) at the end time T0e is calculated as follows. And the total value. As described above, in the rough forward grinding, the rough forward grinding is performed based on the total deflection amount εa (θ) of the crankpin Wa in the rough forward grinding according to the phase θ of the crankpin Wa.

  While performing rough forward grinding, it is determined whether or not the outer diameter Dt of the crank pin Wa measured by the sizing device 17 has reached a preset value Dth. When the outer diameter Dt of the crank pin Wa reaches the set value Dth, the rough forward grinding is switched to the backward grinding. The reverse grinding is a grinding performed while the grinding wheel 15 is relatively moved in the direction away from the crank pin Wa (X-axis plus direction) to reduce the bending amount εna (θ) of the crank pin Wa due to the grinding resistance Fna (θ). It is.

  At the start T1s (= T0e) of the reverse grinding, as shown in FIG. 4B, the radius of the outer peripheral surface of the crankpin Wa varies depending on the phase of the crankpin Wa. This is because the crank pin Wa is rotated while moving the grinding wheel 15 forward. The difference in the radius of the outer peripheral surface of the crankpin Wa has a substantially linear relationship with the phase of the crankpin Wa. Therefore, in reverse grinding, the grinding wheel 15 is retracted, and the portion is scraped so as to eliminate the radius difference according to the phase.

  Specifically, in the reverse grinding, when the crank pin Wa is rotated, for example, once, the grinding resistance Fnb (θ) is set to zero. That is, at the end T1e of the backward grinding, the amount of cutting with respect to the crankpin Wa by the grinding wheel 15 is controlled to be zero. Note that the back grinding may be performed for two or more turns of the crank pin Wa. At the end T1e of the backward grinding, as shown in FIG. 4C, the radius difference between the outer peripheral surfaces of the crank pins Wa is eliminated. At this time, since the grinding resistance Fnb (θ1e) becomes zero, the deflection amount εb (θ1e) of the crank pin Wa coincides with the deflection amount εp (θ1e) due to the coolant dynamic pressure Fp (θ1e).

  Here, in the backward grinding, the crankpin Wa in the backward grinding according to the phase θ of the crankpin Wa based on the deflection amount εa (θ) of the crankpin Wa in the rough forward grinding according to the phase θ of the crankpin Wa. The bending amount εb (θ) is estimated, and the backward grinding is performed based on the estimated bending amount εb (θ) in the backward grinding.

  When the reverse grinding is finished, the back-off operation is performed in the non-grinding state with the grinding resistance Fnb (θ) being zero (T2s to T2e in FIG. 3). The back-off operation is an operation in which the grinding wheel 15 is further moved backward from the time T1e at the end of the backward grinding so that the grinding wheel 15 is separated from the crank pin Wa. During the back-off operation or at the time T2e when the back-off operation is finished, the coolant supply amount Q is switched to the small flow rate Qmin.

  After the back-off operation and after the coolant supply amount Q is switched to the small flow rate Qmin, finish forward grinding (T3s to T3e in FIG. 3) is performed. In the finish forward grinding, the control device 18 starts the finish forward grinding by moving the grinding wheel 15 forward (moving in the X axis minus direction) with respect to the crank pin Wa. In the finish forward grinding, as shown in FIG. 3, it is slower than the moving speed (cutting speed) of the grinding wheel 15 in the rough forward grinding. Therefore, in finish forward grinding, it is possible to prevent grinding burn on the crankpin Wa. Furthermore, by setting the coolant supply amount Q to a small flow rate Qmin, adverse effects on the grinding accuracy due to the recess A such as an oil hole can be suppressed.

  During the finish forward grinding, when the outer diameter Dt of the crankpin Wa measured by the sizing device 17 reaches the finish diameter Df, the finish forward grinding is switched to the spark out. The spark-out is performed with the cutting amount with respect to the crankpin Wa by the grinding wheel 15 being zero. That is, in the spark-out, the remaining grinding is ground in the finish forward grinding. Then, this spark-out is performed for the number of rotations of the crankpin Wa set in advance. In FIG. 3, it is T4s-T4e.

(4. Functional block configuration of grinding machine)
Next, the functional block configuration of the grinding machine will be described with reference to FIG. As shown in FIG. 5, the control device 18 includes a basic grinding control unit 181 and a correction unit 182. The basic grinding control unit 181 includes a rough forward grinding control unit, a reverse grinding control unit, a finish forward grinding control unit, a back control unit that perform basic control in each of rough forward grinding, reverse grinding, finish forward grinding, back-off operation, and spark-out. It functions as an off control unit and a spark out control unit.

  The basic grinding control unit 181 drives a drive motor 14a as a drive device for driving the grinding wheel base 14 based on the position command value based on the NC data and the detection value by the position detector 14b of the grinding wheel base 14. Then, the basic grinding control unit 181 performs process switching when the outer diameter Dt of the crank pin Wa measured by the sizing device 17 reaches a specified value.

In the present embodiment, the basic grinding control unit 181 as each control unit controls the position of the grindstone table 14 with respect to the crankpin Wa based on the position command value in each step when grinding in each step. However, the basic grinding control unit 181 as the reverse grinding control unit considers the deflection amount εb (θ) in the backward grinding in addition to the basic backward amount ΔX _master (θ) as the position command value in the backward grinding. The position of the base 14 is controlled. The processing by the reverse grinding control unit will be described in detail below.

  The correction unit 182 performs correction processing for the basic control by the basic grinding control unit 181. Therefore, the drive motor 14 a as a drive device is driven based on the correction value by the correction unit 182 in addition to the control command value by the basic grinding control unit 181. The correction unit 182 performs correction processing in rough forward grinding, reverse grinding, and finish forward grinding. Similarly to the basic grinding control unit 181, the correction unit 182 switches correction processing when the outer diameter Dt of the crank pin Wa measured by the sizing device 17 reaches a specified value.

(5. Correction processing)
The correction process by the correction unit 182 shown in FIG. 5 will be described with reference to the flowchart of FIG. When the rough forward grinding is started (S11: Y), the correction unit 182 performs correction by the first correction amount D1 (θ) and the second correction amount D2 (θ) with respect to the control by the basic grinding control unit 181. Perform (S12). At this time, the basic grinding control unit 181 as the rough advance grinding control unit controls the position of the grindstone base 14 based on the position command value in the rough advance grinding.

  Here, the first correction amount D1 (θ) is a correction amount calculated from the deflection amount εa (θ) of the crank pin Wa corresponding to the pressing force Fa (θ) by rough forward grinding. The second correction amount D2 (θ) is a correction amount calculated from the roundness error obtained by roundness measurement. Details of the first and second correction amounts D1 (θ) and D2 (θ) will be described later.

  Then, the correction in the rough forward grinding is performed until the rough forward grinding is finished (S13: N). When the rough forward grinding is finished, the backward grinding is started as shown in FIG. When the rough forward grinding is completed (S13: Y), the correction unit 182 performs correction using the first correction amount D1 (θ) and the second correction amount D2 (θ) used in the rough forward grinding ( S14). Here, in the reverse grinding, the correction unit 182 does not perform the correction by the bending amount εb (θ) of the crankpin Wa in the backward grinding, but corrects by the bending amount εa (θ) of the crankpin Wa in the rough forward grinding. Do.

  At this time, the basic grinding control unit 181 as the backward grinding control unit controls the position of the grindstone table 14 based on the position command value in the backward grinding and the deflection amount εb (θ) of the crank pin Wa in the backward grinding.

  The correction in the backward grinding is performed until the backward grinding is finished (S15: N). When the backward grinding is finished, as shown in FIG. 3, back-off is started, and then finish forward grinding is started. When the backward grinding is finished (S15: Y) and the finish forward grinding is further started (S16: Y), the correction unit 182 performs correction by the second correction amount D2 (θ) (S17). Correction in finish forward grinding is performed until finish forward grinding is completed (S18: N). Here, since the grinding resistance is generally smaller during finish forward grinding than during rough forward grinding, the correction amount is also different. Therefore, the correction unit 182 does not perform correction using the first correction amount D1 (θ) when performing finish grinding. Then, when finish forward grinding is finished (S18: Y), the correction unit 182 finishes the correction process.

(6. Calculation of first correction amount D1 (θ))
Next, a procedure for calculating the first correction amount D1 (θ) by the correction unit 182 will be described with reference to FIGS. Here, in the rough forward grinding, the crank pin Wa is bent and deformed in the cutting direction (left direction in FIGS. 2A to 2D) by the pressing force Fa (θ) in the cutting direction received from the grinding wheel 15. Here, the pressing force Fa (θ) in the rough forward grinding is a total value of the grinding resistance Fna (θ) and the coolant dynamic pressure Fp (θ) as shown in the equation (1). That is, the amount of bending εa (θ) of the crank pin Wa is the amount of bending due to the pressing force Fa (θ).

[Equation 1]
Fa (θ) = Fna (θ) + Fp (θ) (1)

  The first correction amount D1 (θ) is determined based on the deflection amount εa (θ). Here, the amount of deflection εa (θ) varies depending on the phase θ of the crankshaft W. For this reason, the first correction amount D1 (θ) is set to a different value according to the phase θ of the crankshaft W.

  First, a grinding resistance Fna (θ) in rough forward grinding is calculated. The grinding resistance Fna (θ), as shown in Equation (2), is a grinding efficiency Z, a sharpness coefficient α of the grinding wheel 15, and a coefficient H corresponding to the grinding width (hereinafter referred to as “grinding width coefficient H”). It is represented by multiplication. The grinding width coefficient H represents, for example, a ratio when the minimum width is 1. That is, H is 1 when the grinding width is the same over the entire circumference.

[Equation 2]
Fna = Z × α × H (2)

  Therefore, as shown in FIG. 7, during rough forward grinding, the actual grinding efficiency Zreal is acquired based on the actual cutting depth d (reference numeral 111 in FIG. 7), and the detection value of the force sensor 16 is based on The actual pressing force Freal is acquired (reference numeral 112 in FIG. 7). Further, the grinding width coefficient H can be derived from the shapes of the crank pin Wa and the grinding wheel 15. The cutting depth d can be derived from the grinding conditions. Note that the cutting depth d may be obtained by calculation using a signal from the sizing device 17.

  As shown in FIG. 8, points in a plurality of cases are plotted with the grinding efficiency Zreal as the horizontal axis and the pressing force Freal as the vertical axis. In this case, the slope of the least square approximation line of the point group is a product of the sharpness coefficient α and the grinding width coefficient H from the relationship of the expressions (1) and (2). That is, the sharpness coefficient α can be calculated by obtaining the slope of the approximate straight line in FIG. 8 and dividing by the grinding width coefficient H (reference numeral 113 in FIG. 7).

  The sharpness coefficient α indicates the relationship between the pressing force Fa in the cutting direction to the crank pin Wa by the grinding wheel 15 and the grinding efficiency Z. The sharpness coefficient α varies depending on the state of the abrasive grains of the grinding wheel 15. Therefore, when many crankshafts W are ground, the sharpness coefficient α is updated by appropriately measuring by rough forward grinding.

  Here, as shown in FIGS. 2A to 2D, the distance from the rotation center O to the grinding point P varies depending on the phase θ. Therefore, as shown in FIG. 9, the grinding point speed v (θ) changes according to the phase θ. For example, when the phase θ is 180 °, the grinding point P is farthest from the rotation center O as shown in FIG. 2C, and the grinding point velocity v (180 °) is the largest value as shown in FIG. Become. In this way, the grinding point speed v (θ) can be calculated geometrically from the shape of the crankshaft W and the grinding conditions (reference numeral 114 in FIG. 7).

  Subsequently, a theoretical grinding efficiency Zlogical (θ) is calculated using the grinding point velocity v (θ) (reference numeral 115 in FIG. 7). The grinding efficiency Zlogical (θ) can be obtained by multiplying the grinding point speed v (θ) and the cutting depth d as shown in the equation (3). However, Equation (3) takes into account the influence γ (θ) due to the recess A. As shown in FIG. 10, the grinding efficiency Zlogical (θ) varies according to the phase θ. In FIG. 10, the portion where the grinding efficiency Zlogical (θ) suddenly decreases when the phase θ is around 180 ° is due to the influence γ (θ) of the recess A.

[Equation 3]
Zlogical (θ) = d × v (θ) + γ (θ) (3)

  Next, the grinding resistance Fna (θ) is calculated according to the equation (4) from the sharpness factor α, the theoretical grinding efficiency Zlogical (θ), and the grinding width factor H (reference numeral 116 in FIG. 7). Equation (4) corresponds to a function of Fna and Z in equation (2) as a function of phase θ. The grinding resistance Fna (θ) changes according to the phase θ as shown by a two-dot chain line in FIG.

[Equation 4]
Fna (θ) = Zlogical (θ) × α × H (4)

  Subsequently, the coolant dynamic pressure Fp (θ) is calculated (reference numeral 117 in FIG. 7). The coolant dynamic pressure Fp (θ) corresponds to a state where the grinding resistance Fna (θ) is zero, that is, an actual pressing force Freal (θ) at the time of sparking out. That is, the coolant dynamic pressure Fp (θ) may be acquired at the time of sparking performed after finish forward grinding, or the spark dynamic is performed immediately before starting rough forward grinding, and at this time the coolant dynamic pressure Fp ( θ) may be acquired. The coolant dynamic pressure Fp (θ) varies depending on the phase θ as shown by the broken line in FIG.

  Here, as shown in FIGS. 2A to 2D, when the phase θ is different, the grinding point P is different from the position of the coolant nozzle 19. Therefore, the amount of coolant supplied varies depending on the phase θ. As a result, the coolant dynamic pressure Fp (θ) varies depending on the phase θ. For example, as shown by the broken lines in FIG. 2B and FIG. 11, the coolant dynamic pressure Fp (90 °) when the phase θ is 90 ° is the smallest. On the other hand, as shown by the broken lines in FIG. 2D and FIG. 11, the coolant dynamic pressure Fp (θ) when the phase θ is 270 ° is the largest. Further, when the phase θ is 180 °, the coolant dynamic pressure Fp (180 °) is smaller than the front and rear phases due to the influence of the recess A.

  Since the grinding resistance Fna (θ) and the coolant dynamic pressure Fp (θ) can be obtained, the pressing force Fa (θ) that is the sum of these is calculated from the equation (1) (reference numeral 118 in FIG. 7). That is, as shown by the thick solid line in FIG. From FIG. 11, the phase θ is the largest around 250 °, and the smallest around 70 °. Further, when the phase θ is around 180 °, it is lowered due to the influence of the recess A.

  Subsequently, as shown in FIG. 7, the rigidity K (θ) in the cutting direction at the crank pin Wa portion is calculated from the shape of the crankshaft W (reference numeral 119 in FIG. 7). In this case, the stiffness K (θ) can be calculated based on an actual measurement value, or can be obtained by structural analysis. The rigidity K (θ) of the crankpin Wa also varies depending on the phase θ.

  Then, using the pressing force Fa (θ) and the stiffness K (θ), the amount of bending εa (θ) of the crank pin Wa due to the pressing force Fa (θ) (hereinafter referred to as the total amount of bending) is expressed according to the equation (5). Calculate (reference numeral 120 in FIG. 7). That is, the total deflection amount εa (θ) is obtained by dividing the pressing force Fa (θ) by the stiffness K (θ). As shown in FIG. 12, the total deflection amount εa (θ) due to the pressing force Fa (θ) varies according to the phase θ.

[Equation 5]
εa (θ) = Fa (θ) / K (θ) (5)

  Further, when the total deflection amount εa (θ) varies depending on the phase θ, there is a possibility that a roundness error of the crankpin Wa may occur. Therefore, a first correction amount D1 (θ) for calculating the roundness error due to the total deflection amount εa (θ) to zero is calculated (reference numeral 121 in FIG. 7). That is, the first correction amount D1 (θ) is determined so that the difference of the total deflection amount εa (θ) for each phase θ is zero. Here, the first correction amount D1 (θ) is set as shown in FIG.

  In rough forward grinding, the correction unit 182 corrects the first correction amount D1 (θ) determined in this way, so that the coolant dynamic pressure Fp (θ) and the grinding efficiency Z (θ) correspond to the phase θ. Grinding errors due to differences between the two can be reduced. That is, the roundness of the crankpin Wa can be made highly accurate when the rough forward grinding is finished.

(7. Calculation of second correction amount D2 (θ))
Next, the procedure for calculating the second correction amount D2 (θ) will be described with reference to the flowchart of FIG. As described above, the correction using the second correction amount D2 (θ) is performed in the rough forward grinding, the backward grinding, and the finish forward grinding.

  For the second correction amount D2 (θ), the roundness of the crankpin Wa that has actually been ground is measured (S21), and the roundness error is acquired. A second correction amount D2 (θ) that makes this roundness error zero is calculated (S22). Using the calculated second correction amount D2 (θ), the roundness of the crankpin Wa in the rough forward grinding and the finish forward grinding is more accurately corrected by performing the correction when the crankpin Wa is ground next time. Can be.

(8. Basic control by the reverse grinding controller)
Next, basic control by the basic grinding control unit 181 as the reverse grinding control unit in the reverse grinding will be described with reference to FIGS. 15 to 22. As described above, the basic grinding control unit 181 as the backward grinding control unit considers the total deflection amount εb (θ) in the backward grinding in addition to the basic backward amount ΔX _master (θ) as the position command value in the backward grinding. Then, the position of the grinding wheel base 14 is controlled.

  Accordingly, the basic grinding control unit 181 as the backward grinding control unit calculates the backward amount ΔX (θ) at each phase θ as follows. First, the basic grinding control unit 181 acquires the target cutting amount d (θ) corresponding to the phase θ from the start to the end of the reverse grinding (reference numeral 211 in FIG. 15). As shown in FIG. 16, the target cutting amount d (θ) is the cutting amount at the phase θ1e at the end of the backward grinding when the cutting amount d at the phase θ1s at the start of the backward grinding is 100%. d is 0%, and decreases linearly with respect to the phase θ from the start to the end. This is because, as described with reference to FIG. 4B, the difference in the radius of the outer peripheral surface of the crankpin Wa is substantially linear with respect to the phase of the crankpin Wa at the start T1s of the reverse grinding. is there.

  Further, the basic grinding control unit 181 acquires a grinding resistance Fna (θ) in rough forward grinding (reference numeral 212 in FIG. 15). The grinding resistance Fna (θ) has already been calculated at 116 in FIG. 7 in rough forward grinding. This grinding resistance Fna (θ) behaves as shown by a thin line in FIG.

  Subsequently, the basic grinding control unit 181 estimates the grinding resistance Fnb (θ) in the reverse grinding based on the target cutting amount d (θ) and the grinding resistance Fna (θ) in the rough forward grinding (reference numeral in FIG. 15). 213). Here, as shown in FIG. 17, it is assumed that the backward grinding ends from the phase θ1s at the start to the phase θ1e when the crankshaft W makes one rotation. In this case, the grinding resistance Fnb (θ) in the reverse grinding is the target depth of cut with respect to the grinding resistance Fna (θ) in the rough forward grinding during the phase θ1s to θ1e as shown by the thick line in FIG. It decreases at a rate according to d (θ). In FIG. 17, the phase θ1s for starting the reverse grinding is about 50 °, but the start phase θ1s is the phase when the outer diameter Dt of the crankpin Wa reaches Dth as shown in FIG. It becomes.

  Subsequently, the basic grinding control unit 181 acquires the coolant dynamic pressure Fp (θ) (reference numeral 214 in FIG. 15). The coolant dynamic pressure Fp (θ) has already been calculated at reference numeral 117 in FIG. 7 in the rough forward grinding. The coolant dynamic pressure Fp (θ) behaves as shown in FIG. 18 during the phase θ1s to θ1e.

  Subsequently, the basic grinding control unit 181 estimates the sum of the grinding resistance Fnb (θ) and the coolant dynamic pressure Fp (θ) in the backward grinding as the pressing force Fb (θ) in the backward grinding (reference numeral 215 in FIG. 15). ). The pressing force Fb (θ) in the backward grinding behaves as shown by a thick line in FIG. In FIG. 19, the pressing force Fa (θ) in the rough forward grinding is shown by a thin line. As shown in FIG. 19, the pressing force Fb (θ) decreases according to the decrease in the grinding resistance Fnb (θ).

  Then, using the pressing force Fb (θ) and the rigidity K (θ), the total deflection amount εb (θ) of the crank pin Wa due to the pressing force Fb (θ) is estimated according to the equation (6) (reference numeral 216 in FIG. 15). ). That is, the total deflection amount εb (θ) is obtained by dividing the pressing force Fb (θ) by the rigidity K (θ). The total deflection amount εb (θ) due to the pressing force Fb (θ) changes according to the phase θ, as shown by the thick solid line in FIG.

[Equation 6]
εb (θ) = Fb (θ) / K (θ) (6)

  Further, the basic grinding control unit 181 acquires the total deflection amount εa (θ) in the rough forward grinding (reference numeral 217 in FIG. 15). This total deflection amount εa (θ) has already been calculated at reference numeral 120 in FIG. 7 in rough forward grinding. This total deflection amount εa (θ) behaves as shown by the thin line in FIG.

  Further, the bending amount εna (θ0e) due to the grinding resistance Fna (θ0e) at the end T0e of the rough forward grinding is calculated (reference numeral 218 in FIG. 15). By dividing the grinding resistance Fna (θ) in the rough forward grinding acquired by reference numeral 212 in FIG. 15 by the rigidity K (θ), a deflection amount εna (θ) due to the grinding resistance Fna (θ) can be obtained. . Then, the amount of deflection εna (θ0e) due to the grinding resistance Fna (θ0e) at the phase θ0e is calculated.

  Here, the amount of deflection εna (θ) due to the grinding resistance Fna (θ) behaves as shown by a thin two-dot chain line in FIG. That is, the deflection amount of the phase θ0e in this behavior (thin two-dot chain line) is εna (θ0e). This deflection amount εna (θ0e) is the same as the deflection amount εnb (θ1s) due to the grinding resistance Fnb (θ1s) in the phase θ1s at the start of the backward grinding. That is, the deflection amount εna (θ0e) can also be calculated as the deflection amount εnb (θ1s) due to the grinding resistance Fnb (θ1s) in the backward grinding.

Subsequently, the basic grinding control unit 181 calculates a difference Δε _ab (θ) between the total deflection amount εa (θ) in the rough forward grinding and the total deflection amount εb (θ) in the reverse grinding according to the equation (7) ( Reference numeral 219 in FIG. This deflection difference Δε _ab (θ) behaves as shown in FIG.

[Equation 7]
Δε _ab (θ) = εa (θ) −εb (θ) (7)

Subsequently, based on the deflection amount εna (θ0e) due to the grinding resistance Fna (θ0e) at the end of rough forward grinding T0e, a basic retraction amount ΔX _master (θ) as a position command value in the reverse grinding is calculated (FIG. 15). 220). As shown by a two-dot chain line in FIG. 22, the basic retraction amount ΔX _master (θ) is set to zero in the phase θ1s at the start of reverse grinding, and the deflection amount εna (θ0e) (in FIG. 20) in the phase θ1e at the end. It increases linearly as shown.

Subsequently, a retraction amount ΔX (θ) in the reverse grinding is calculated by adding the total deflection amount Δε _ab (θ) to the basic retraction amount ΔX _master (θ) (reference numeral 221 in FIG. 15). The calculated retraction amount ΔX (θ) behaves as shown by the thick solid line in FIG. Then, the basic grinding control unit 181 drives the drive motor 14a as a drive device based on the calculated retraction amount ΔX (θ). That is, the drive motor 14a is driven based on the reverse amount ΔX (θ) and the first correction amount D1 (θ), so that the reverse grinding is performed on the crank pin Wa.

(9. Summary)
As described above, the grinding machine performs reverse grinding in consideration of the difference Δε _ab (θ) between the total deflection amount εa (θ) in rough forward grinding and the total deflection amount εb (θ) in reverse grinding. ing. That is, the grinding machine performs the backward grinding in consideration of the total deflection amount εb (θ) in the backward grinding. Therefore, the roundness of the crank pin Wa in the reverse grinding can be made highly accurate. Here, the reverse grinding is performed while the crankshaft W is rotated once or several times. Therefore, it is not easy to obtain the total deflection amount εb (θ) in the backward grinding during the backward grinding.

  Therefore, as described above, the total deflection amount εb (θ) in the backward grinding is estimated based on the total deflection amount εa (θ) in the rough forward grinding. Here, as shown in FIG. 20, the total deflection amount εa (θ) in rough forward grinding is different from the total deflection amount εb (θ) in reverse grinding, but it has been described with reference to FIGS. Thus, it can be seen that there is a correlation between the two. Therefore, the total deflection amount εb (θ) in the reverse grinding can be estimated based on the total deflection amount εa (θ) in the rough forward grinding.

  Further, the total deflection amount εa (θ) in the rough forward grinding can be obtained from the grinding force Fa (θ) acquired during the rough forward grinding (reference numeral 120 in FIG. 7). Therefore, the total deflection amount εb (θ) in the reverse grinding can be reliably obtained by estimating based on the total deflection amount εa (θ) in the rough forward grinding.

  Further, in the reverse grinding, as shown in FIG. 16, the cutting amount is gradually decreased during that time. The total deflection amount εb (θ) in the reverse grinding changes in accordance with the depth of cut. That is, the total deflection amount εb (θ) in the reverse grinding depends on the cutting amount. Here, the cutting amount is determined by the target cutting amount d (θ) and the deflection amount εnb (θ1s) due to the grinding resistance Fnb (θ1s) at the phase θ1s at the start of the backward grinding.

  Therefore, the total deflection amount εb (θ) in the reverse grinding is not limited to the total deflection amount εa (θ) in the forward grinding, the grinding resistance Fna (θ0e) in the phase θ0e at the end of the forward grinding and the target cutting in the backward grinding. By using the quantity d (θ), it can be reliably estimated. The grinding resistance Fnb (θ1s) at the phase θ1s at the start of the reverse grinding and the grinding resistance Fna (θ0e) at the phase θ0e at the end of the rough forward grinding are the same.

  Further, the correction by the correction unit 182 in the backward grinding is performed based on the total deflection amount εa (θ) in the rough forward grinding as in the rough forward grinding. Therefore, the correction process by the correction unit 182 can be the same process in the backward grinding and the rough forward grinding.

However, in the backward grinding, if the correction based on the total deflection amount εa (θ) in the rough forward grinding is performed, an excessive correction is performed. Therefore, the basic grinding control unit 181 as the backward grinding control unit performs position control in consideration of the deflection amount difference Δε _ab (θ) in addition to the basic backward amount ΔX _master (θ) as the position command value. By doing in this way, in the reverse grinding, the crank pin Wa can be made with high accuracy roundness.

<Second embodiment>
Next, a second embodiment will be described. This embodiment differs from the above embodiment in the processing of the control device 18 in the reverse grinding. The processing of the basic grinding control unit 181 as the backward grinding control unit is performed as shown in FIG.

First, a deflection amount εna (θ0e) due to the grinding resistance Fna (θ0e) at the phase θ0e at the end of rough forward grinding is calculated (S41). This deflection amount εna (θ0e) is calculated by reference numeral 219 in FIG. 15 in the above embodiment. Subsequently, based on the deflection amount εna (θ0e) and the target cutting amount d (θ) shown in FIG. 16, a basic retraction amount ΔX _master (θ) as a position command value in reverse grinding is calculated (S42). ). This basic retraction amount ΔX _master (θ) behaves as shown in FIG. Then, the basic grinding control unit 181 as the backward grinding control unit drives the drive motor 14a as the driving device based on the basic backward amount ΔX _master (θ).

  The correction unit 182 performs the process shown in FIG. 25 in the backward grinding. 25, S51 to S53 and S55 to S58 are the same processes as S11 to S13 and S15 to S18 in FIG. That is, S54 in FIG. 25 is different from S14 in FIG.

  When the rough forward grinding is finished (S53: Y), the correction unit 182 performs the third correction instead of the first correction amount D1 (θ) and the second correction amount D2 (θ) used in the rough forward grinding. Correction is performed using the amount D3 (θ) and the second correction amount D2 (θ) (S54). The third correction amount D3 (θ) is a correction amount calculated from the total deflection amount εb (θ) of the crank pin Wa according to the pressing force Fb (θ) by the backward grinding.

  In the above embodiment, the first correction amount D1 (θ) is calculated based on the total deflection amount εa (θ) (shown in FIG. 12) in rough forward grinding. Specifically, the first correction amount D1 (θ) is determined so that the difference of the total deflection amount εa (θ) in the rough forward grinding for each phase θ is zero. Here, as shown in FIG. 13, the first correction amount D1 (θ) has a relationship obtained by vertically inverting the total deflection amount εa (θ) shown in FIG.

  The third correction amount D3 (θ) in the present embodiment is set to have a relationship obtained by vertically inverting the total deflection amount εb (θ) in the backward grinding. Here, the total deflection amount εb (θ) in the backward grinding is calculated by reference numeral 216 in FIG. 15 and has the behavior shown by the thick solid line in FIG. Therefore, as indicated by a thick solid line in FIG. 26, the third correction amount D3 (θ) is set so that the total deflection amount εb (θ) shown in FIG.

  Further, the correction unit 182 performs correction in reverse grinding following correction in rough forward grinding. Therefore, the correction unit 182 sets the same correction value at the moment when the grinding process is switched. That is, in the phase θ1s (= θ0e) to be switched, the first correction amount D1 (θ0e) and the third correction amount D3 (θ1s) in the rough forward grinding shown by the thin solid line in FIG. By doing in this way, it can prevent that a correction value changes suddenly, when the correction process by the correction | amendment part 182 switches in connection with a grinding process switching.

As described above, the correction by the correction unit 182 in the backward grinding is performed based on the total deflection amount εb (θ) in the backward grinding, unlike the correction by the correction unit 182 in the rough forward grinding. By doing in this way, in the backward grinding, the crankpin Wa can be surely made to have a highly accurate roundness. In this case, the basic grinding control unit 181 as the back grinding control unit performs control based on the basic retraction amount ΔX _master (θ).

DESCRIPTION OF SYMBOLS 1: Grinding machine, 12: Main shaft, 12a: Drive motor, 12b: Rotation detector, 14: Grinding wheel base, 14a: Drive motor, 15: Grinding wheel, 18: Control device, 181: Basic grinding control part (forward grinding control) Part, reverse grinding control part), 182: correction part, 216: means for estimating the deflection amount εb (θ), d (θ): target cutting depth, D1 (θ): first correction amount, D3 (θ) : Third correction amount, Fna (θ): grinding resistance in rough forward grinding, Fnb (θ): grinding resistance in backward grinding, P: grinding point, W: crankshaft, Wa: crankpin, ΔX (θ): Retraction amount, ΔX _master (θ): Basic retraction amount, Δε _ab (θ): Deflection amount difference, εa (θ): Deflection amount in forward grinding, εb (θ): Deflection amount in backward grinding, θ0e: Rough forward grinding , Phase at the end of θ, θ1s: phase at the start of reverse grinding, θ1e: phase at the end of reverse grinding

Claims (5)

A grinding machine that performs forward grinding to relatively advance the grinding wheel toward the workpiece, and performs backward grinding to relatively retract the grinding wheel from the workpiece following the forward grinding,
Estimating the amount of bending εb (θ) of the workpiece in the backward grinding according to the phase θ of the workpiece,
A grinding machine that performs the backward grinding based on a deflection amount εb (θ) in the backward grinding.   The amount of bending εb (θ) in the backward grinding is the amount of bending εa (θ) of the workpiece in the forward grinding according to the phase θ of the workpiece and the grinding in the phase θ0e at the end of the forward grinding. The grinding machine according to claim 1, wherein the grinding machine is estimated based on a resistance Fna (θ0e) and a target cutting amount d (θ) from the start to the end of the backward grinding. The grinding machine
A forward grinding control unit for controlling the position of the grinding wheel with respect to the workpiece based on a position command value during the forward grinding;
The basic retraction amount ΔX _master (θ) as a position command value in the reverse grinding, the deflection amount εa (θ) of the workpiece in the forward grinding according to the phase θ of the workpiece, and the reverse grinding A reverse grinding control unit that controls the position of the grinding wheel with respect to the workpiece, based on a difference Δε _ab (θ) with a deflection amount εb (θ) at
In the forward grinding, correction for the control by the forward grinding control unit is performed based on the deflection amount εa (θ) in the forward grinding, and based on the deflection amount εa (θ) in the forward grinding in the backward grinding. A correction unit for correcting the control by the backward grinding control unit,
The grinding machine according to claim 1, comprising: The grinding machine
A forward grinding control unit for controlling the position of the grinding wheel with respect to the workpiece based on a position command value during the forward grinding;
A reverse grinding control unit for controlling the position of the grinding wheel with respect to the workpiece based on a basic retraction amount ΔX _master (θ) as a position command value during the reverse grinding;
In the forward grinding, correction for control by the forward grinding control unit is performed based on a deflection amount εa (θ) of the workpiece in the forward grinding according to the phase θ of the workpiece, and the backward grinding is performed. A correction unit that corrects the control by the reverse grinding control unit based on the deflection amount εb (θ) in the reverse grinding at the time of,
The grinding machine according to claim 1, comprising: A grinding method for performing forward grinding for relatively advancing the grinding wheel toward the workpiece, and performing backward grinding for relatively retracting the grinding wheel from the workpiece following the forward grinding,
Estimating the amount of bending εb (θ) of the workpiece in the backward grinding according to the phase θ of the workpiece,
A grinding method in which the backward grinding is performed based on a deflection amount εb (θ) in the backward grinding.

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