JP6089752B2 - Grinding machine and grinding method - Google Patents

Description

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

  When a workpiece is roughly ground with a grinding wheel, it is performed while supplying coolant to suppress heat generation. On the other hand, in finish grinding, the coolant supply amount is set to a small flow rate in order to obtain high accuracy. That is, when the coolant supply amount is changed, the coolant dynamic pressure changes. Therefore, in Patent Document 1, a back-off operation is performed in an unground state before switching the coolant from a large flow rate to a small flow rate. The back-off amount is a constant value. In addition, Patent Documents 2 and 3 disclose that the workpiece is ground by 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 backward grinding. Have been described.

JP 2011-31366 A JP 2011-93017 A JP 2011-140089 A

  Here, the cutting speed in finish grinding is much smaller than that in rough grinding. For this reason, if the back-off amount is excessively increased, the blank grinding state becomes longer when finish grinding is performed, which causes a longer grinding time. On the other hand, if the back-off amount is too small, the amount of bending of the work piece decreases with a decrease in the coolant dynamic pressure, which may cause a cut at the start of finish grinding. For this reason, it is required to set the back-off amount to an appropriate value.

  The present invention has been made in view of such circumstances. By determining the back-off amount according to the start time of the back-off operation, the grinding can be performed with high accuracy while reducing the grinding time. An object is to provide a board and a grinding method.

  Focusing on the fact that the workpiece deflection amount ε (θ) varies depending on the workpiece phase θ, the backoff amount is based on the workpiece deflection amount ε (θ2s) at the start T2s of the backoff operation. It was decided to decide.

(Grinder)
(Claim 1) The grinding machine according to the present means performs the first grinding with a large flow rate of the coolant, performs a back-off operation in an unground state following the first grinding, and performs the back-off operation. Subsequently, a grinding machine for performing second grinding with a small amount of supply of the coolant, wherein at least one of the rigidity K of the workpiece, the coolant dynamic pressure Fp, the grinding efficiency Z, and the grinding width is the workpiece. Therefore, the pressing force F (θ) in the cutting direction that the workpiece receives from the grinding wheel during the first grinding differs depending on the phase θ, and as a result, the first grinding When the bending amount ε (θ) of the workpiece due to the grinding resistance Fn and the coolant dynamic pressure Fp varies according to the phase θ, the phase θ2s of the workpiece at the start T2s of the back-off operation The amount of bending ε (θ2s) of the workpiece is acquired. Comprising the stage, means for determining a back-off amount on the basis of the amount of deflection epsilon (? 2s), in the back-off operation, and means for retracting the back-off amount.

Below, the preferable aspect of the grinding machine which concerns on this means is described.
(Claim 2) The means for determining the back-off amount includes the deflection amount ε (θ2s) in the phase θ2s of the workpiece or a value obtained by adding a constant value to the deflection amount ε (θ2s). It is good to use off amount.

  (Claim 3) The means for obtaining the amount of deflection is the amount of deflection ε (θ2s−θ2e) of the workpiece corresponding to each phase θ between the start time T2s and the end time T2e of the back-off operation. The means for calculating and the means for determining the back-off amount may be a maximum value ε_max of the deflection amount ε (θ2s−θ2e) or a value obtained by adding a constant value to the maximum value ε_max as the back-off amount. Good.

(Claim 4) It may be applied when the ground surface of the workpiece has a recess that is not ground.
(Claim 5) In the first grinding, the first forward grinding is performed in which the grinding wheel is relatively advanced to the workpiece, and the grinding wheel is moved backward from the workpiece following the first forward grinding. The back-off operation is performed to make the grinding wheel Fn zero, and in the back-off operation, the grinding wheel is further moved backward following the backward grinding while the grinding force Fn is kept zero, and the amount of bending of the workpiece is reduced. ε (θ2s) may be applied when the amount of bending of the workpiece by the coolant is εb (θ2s).

(Grinding method)
The present invention can be grasped as a grinding method in addition to the above-described grinding machine.
(Claim 6) The grinding method according to this means performs the first grinding with a large coolant supply amount, performs the back-off operation in an unground state following the first grinding, and performs the back-off operation. Subsequently, a grinding method for performing second grinding with the coolant supply amount being a small flow rate, wherein at least one of the rigidity K of the workpiece, the coolant dynamic pressure Fp, the grinding efficiency Z, and the grinding width is the workpiece. Therefore, the pressing force F (θ) in the cutting direction that the workpiece receives from the grinding wheel during the first grinding differs depending on the phase θ, and as a result, the first grinding When the bending amount ε (θ) of the workpiece due to the grinding resistance Fn and the coolant dynamic pressure Fp varies according to the phase θ, the phase θ2s of the workpiece at the start T2s of the back-off operation Obtain the amount of bending ε (θ2s) of the workpiece That comprises a step, a step of determining a back-off amount on the basis of the amount of deflection epsilon (? 2s), in the back-off operation, and a step of retracting the back-off amount.

(Claims 1 and 6) According to the present means, the back-off amount is determined on the basis of the deflection amount ε (θ2s) of the work piece at the start time T2s of the back-off operation. Thereby, even if the back-off amount is reduced, it is possible to prevent the incision from occurring at the start of the second grinding. Since the back-off amount can be reduced, the blank grinding state in the second grinding can be reduced, and as a result, the grinding time can be shortened.
Here, the grinding method according to the present means can similarly apply the other aspects related to the grinding machine described above, and have the same effects as the effects described below.

(Claim 2) Thereby, the back-off amount can be easily determined, and in this case, the above-described effect is surely obtained.
(Claim 3) Depending on the relationship between the speed of the back-off operation and the peripheral speed of the workpiece, when the maximum value ε_max is larger than the deflection amount ε (θ2s), the cutting is surely performed during the back-off operation. It can be prevented from occurring. As a result, the above-described effect is surely obtained.

  (Claim 4) When there is a recess in the grinding surface, it is important for high accuracy to make the coolant supply amount small in finish grinding. Therefore, in order to achieve high accuracy, it is necessary to switch the coolant supply amount from a large flow rate to a small flow rate. In this case, it becomes more effective by applying the above.

  (Claim 5) By performing the backward grinding, the shape accuracy of the workpiece can be increased at the end of the backward grinding. Then, by performing the back-off operation following the backward grinding, the back-off amount can be further reduced.

It is a top view of the grinding machine in the embodiment of the present 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 crankpin Wa and the grinding wheel 15 in the middle of the back-off operation of FIG. 3 (between T2s and T2e) are shown. The crankpin Wa and the grinding wheel 15 at the end T2e (= T3s) of the back-off operation in FIG. 3 are shown. It is a block diagram which shows the calculation procedure of deflection amount (epsilon) a ((theta)) by grinding resistance Fn in reverse grinding (T1s-T1e). It is a graph which shows the relationship between the grinding efficiency Zreal and the actual pressing force Freal of the cutting direction which the crankpin Wa receives from the grinding wheel 15. 3 is a graph showing a grinding point speed v (θ) corresponding to a rotational phase θ of a crankshaft W. 4 is a graph showing a theoretical grinding efficiency Zlogical (θ) corresponding to the rotational phase θ of the crankshaft W. 4 is a graph showing a grinding resistance Fn (θ) corresponding to a rotational phase θ of a crankshaft W. 6 is a graph showing the amount of bending εa (θ) of the crankpin Wa due to the grinding resistance Fn (θ) according to the rotational phase θ of the crankshaft W. It is a block diagram which shows the control procedure of the reverse grinding using bending amount (epsilon) a ((theta)) by grinding resistance Fn ((theta)). It is a graph which shows the 1st example regarding the position of the grinding wheel 15 during reverse control (T1s-T1e). It is a graph which shows the 2nd example regarding the position of the grinding wheel 15 during reverse control (T1s-T1e). 4 is a graph showing a coolant dynamic pressure Fp (θ) corresponding to a rotational phase θ of a crankshaft W. It is a block diagram which shows the control procedure of the back-off operation | movement using deflection amount (epsilon) b ((theta)) by coolant dynamic pressure Fp ((theta)). 6 is a graph showing a first example regarding the amount of bending εb (θ) of the crank pin Wa due to the coolant dynamic pressure Fp according to the rotational phase θ of the crankshaft W. It is a graph which shows the 1st example regarding the position of the grinding wheel 15 during back-off operation | movement (T2s-T2e). 7 is a graph showing a second example regarding the amount of bending εb (θ) of the crank pin Wa due to the coolant dynamic pressure Fp according to the rotational phase θ of the crankshaft W. It is a graph which shows the 2nd example regarding the position of the grinding wheel 15 during back-off operation | movement (T2s-T2e).

Embodiments to which a grinding machine and a grinding method according to the present invention are applied will be described below.
(1. Configuration of grinding machine)
A grinding wheel traverse type cylindrical grinder will be described as an example of the grinder of this embodiment. The workpiece to be processed by the grinding machine is exemplified by a crankshaft W, and the grinding portion is a crank pin (eccentric pin) 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.

  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.

  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 rotatably supported by a grinding wheel 15 and is provided with a coolant nozzle 19 (shown in FIG. 2A) 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 workpiece W. 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 workpiece 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 rotation phase θ of the crankshaft W (hereinafter referred to as phase θ) will be described. However, in FIGS. 2A to 2D, the crankshaft W is illustrated as not being bent and deformed. 2A to 2D, the coolant nozzle 19 and the grinding point P are illustrated.

  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 4E. Here, in FIGS. 4A to 4E, 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 4E, Ow and Or are deviated in a state where the crankshaft W is bent.

  In this embodiment, rough forward grinding process (first grinding, first forward grinding) → reverse grinding process (first grinding) → back-off operation → finish forward grinding process (second grinding, second forward grinding) → spark Execute in order of out process. In each grinding process, coolant is always supplied. Here, the coolant supply amount Q is set to a large flow rate Qmax during the rough forward grinding step and the reverse grinding step, and the coolant supply amount Q is set to a small flow rate Qmin during the finish forward grinding step and the spark-out step. To do. 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 grinding (rough forward grinding step) (T0s to T0e in FIG. 3). Further, at the time of rough grinding, the control device 18 controls the coolant supply amount Q supplied to the grinding point P to be a large flow rate Qmax.

  In the rough forward grinding process, as shown at T0s to T0e in the upper part of FIG. That is, in the rough forward grinding process, the grinding wheel 15 is relatively moved in the direction in which it is pressed against the crank pin Wa. Here, in the rough forward grinding process, in order to increase the grinding efficiency Z (amount of grinding per unit time unit width), the moving speed is increased as compared with the finish forward grinding process. 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 start time T0s of the rough forward grinding process of FIG. 3, as shown in FIG. 4A, the actual pin center Or is shifted from the temporary pin center Os by a deflection amount εb due to the coolant dynamic pressure Fp. 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 Fn increases until the time T0e at the end of the rough forward grinding process of FIG. That is, the sum of the coolant dynamic pressure Fp and the grinding resistance Fn acts on the pressing force F received by the crank pin Wa from the grinding wheel 15. Then, the deflection amount ε at the end time T0e is a total value of the deflection amount εa caused by the grinding resistance Fn and the deflection amount εb caused by the coolant dynamic pressure Fp, as shown in FIG. 4B.

  While rough grinding is performed, 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 advance grinding process is switched to the reverse grinding process. The reverse grinding is grinding performed by relatively moving the grinding wheel 15 in the direction in which the grinding wheel 15 is pulled away from the crank pin Wa (X-axis plus direction) to reduce the bending amount εa of the crank pin Wa due to the grinding resistance Fn.

  At the time T1s (= T0e) at the start 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 the reverse grinding process, 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 process, the target grinding resistance according to the phase of the crankpin Wa is determined and controlled so that the grinding resistance Fn becomes zero when the crankpin Wa is rotated once, for example. 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 Fn becomes zero, the bending amount ε of the crank pin Wa coincides with the bending amount εb due to the coolant dynamic pressure Fp.

  When the reverse grinding is finished, the back-off operation is performed in the non-grinding state with the grinding resistance Fn 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 end of the backward grinding so that the grinding wheel 15 is separated from the crank pin Wa as shown in FIG. 4D. During the back-off operation or at the time when the back-off operation is completed, the coolant supply amount Q is switched to the small flow rate Qmin. Then, as shown in FIG. 4E, the coolant dynamic pressure Fp becomes small, and the deflection amount εb due to the coolant dynamic pressure Fp also becomes small.

  After the back-off operation and after the coolant supply amount Q is switched to the small flow rate Qmin, a finishing advance process (T3s to T3e in FIG. 3) is performed. In the finish advancement process, the control device 18 starts the finish advance 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 advancement process, as shown in FIG. 3, it is slower than the moving speed (cutting speed) of the grinding wheel 15 in the rough advance grinding process. Therefore, it is possible to prevent grinding burn from occurring in the crankpin Wa in the finish advancement process. 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 process is switched to the spark out process. The spark-out is performed with the grinding wheel 15 in a state where the cutting depth with respect to the crank pin Wa is 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. Details of reverse grinding)
In the backward grinding (T1s to T1e in FIG. 3), the portion of the radius difference in the rough forward grinding process is scraped off while the grinding wheel 15 is moved backward. Here, when the crank pin Wa is ground, the rigidity K (θ), the coolant dynamic pressure Fp (θ), and the grinding efficiency Z (θ) of the crankshaft W differ according to the phase θ of the crankshaft W. Therefore, the amount of deflection εa (θ) due to the grinding resistance Fn (θ) changes according to the phase θ. Backward grinding is controlled using this deflection amount εa (θ).

  A calculation procedure of the deflection amount εa (θ) by the grinding resistance Fn (θ) will be described with reference to the block diagram of FIG. 5 and FIGS. First, the pressing force F in the cutting direction received by the crank pin Wa from the grinding wheel 15 is an added value of the grinding resistance Fn and the coolant dynamic pressure Fp as shown in the equation (1). Further, the grinding resistance Fn is represented by the following formula (2): grinding efficiency Z, sharpness coefficient α of the grinding wheel 15 and coefficient H corresponding to the grinding width (hereinafter referred to as “grinding width coefficient H”). 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 1]
F = Fn + Fp (1)
[Equation 2]
Fn = Z × α × H (2)

  Therefore, as shown in FIG. 5, during the rough forward grinding process, the actual grinding efficiency Zreal is acquired based on the actual cutting depth d (reference numeral 111 in FIG. 5), and the detection value of the force sensor 16 is set. Originally, the actual pressing force Freal is acquired (reference numeral 112 in FIG. 5). 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.

  From the relationship of equations (1) and (2), in FIG. 6, when the grinding efficiency Zreal is the horizontal axis and the pressing force F is the vertical axis, the slope is a product of the sharpness coefficient α and the grinding width coefficient H. That is, by obtaining the slope of FIG. 6 and dividing by the grinding width coefficient H, the sharpness coefficient α can be calculated. (Reference numeral 113 in FIG. 5). The sharpness coefficient α indicates the relationship between the pressing force F 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 in the rough forward grinding process.

  Here, as shown in FIGS. 2A to 2D, the grinding point P has a different distance from the rotation center O depending on the phase θ. Therefore, as shown in FIG. 7, the grinding point speed v (θ) changes according to the phase θ. This 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. 5).

  Subsequently, a theoretical grinding efficiency Zlogical (θ) is calculated using the grinding point velocity v (θ) (reference numeral 115 in FIG. 5). The grinding efficiency Z (θ) is expressed by the formula (3). In Formula (3), d is the cutting depth. γ is an influence due to the recess A. As shown in FIG. 8, the grinding efficiency Z (θ) varies according to the phase θ. In FIG. 8, the portion where the grinding efficiency Z (θ) suddenly decreases when the phase θ is around 180 ° is due to the influence γ of the recess A.

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

  The grinding resistance Fn (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. 5). Equation (4) is just a function of equation (2) for phase θ. As shown in FIG. 9, the grinding resistance Fn (θ) changes according to the phase θ.

[Equation 4]
Fn (θ) = Z (θ) × α × H (4)

  Subsequently, the rigidity K (θ) of the crank pin Wa portion is calculated from the shape of the crankshaft W (reference numeral 117 in FIG. 5). In this case, the stiffness K (θ) can be calculated based on an actual measurement value, or can be obtained by analysis. Using the grinding resistance Fn (θ) and the stiffness K (θ), the amount of bending εa (θ) of the crank pin Wa due to the grinding resistance Fn (θ) is calculated according to the equation (5) (reference numeral 118 in FIG. 5). The amount of deflection εa (θ) due to the grinding resistance Fn (θ) varies according to the phase θ as shown in FIG.

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

  Next, regarding the control of the reverse grinding using the bending amount εa (θ) by the grinding resistance Fn (θ), the first example will be described with reference to FIGS. Will be described with reference to FIG.

  First, the first example will be described. At the start T1s (shown in FIG. 1) of the reverse grinding, the phase θ1s of the crankshaft W is acquired. Since the relationship between the phase θ and the deflection amount εa (θ) due to the grinding resistance Fn (θ) is as shown in FIG. 10, the deflection amount at the phase θ1s is εa (θ1s). Therefore, the deflection amount εa (θ1s) can be acquired (reference numeral 121 in FIG. 11).

  Subsequently, a retraction amount in the reverse grinding is determined from the acquired deflection amount εa (θ1s) (reference numeral 122 in FIG. 11). In the first example, the bending amount εa (θ1s) is set as the retreat amount. The reverse amount is an amount to be retracted while the crankshaft W makes one revolution. However, although it is 1 rotation here, it is good also as multiple rotation. Further, during the backward grinding, as shown in FIG. 12, the grinding wheel 15 is moved at a constant speed until the deflection amount εa (θ1e) due to the grinding resistance Fn (θ) becomes zero at the end T1e of the backward grinding. Is controlled to move backward (reference numeral 123 in FIG. 11). According to the first example, since it is retracted at a constant speed, it can be easily controlled. Even in this case, sufficiently high accuracy can be achieved.

  A second example will be described. A deflection amount εa (θ1s−θ1e) due to the grinding resistance Fn (θ) corresponding to each phase θ is calculated from the start time T1s to the end time T1e of the reverse grinding (reference numeral 121 in FIG. 11). Subsequently, the deflection amount at the start time T1s is set to εa (θ1s) as the reverse amount during one rotation of the crankshaft W (reference numeral 122 in FIG. 11).

  Then, as shown in FIGS. 10 and 13, the grinding wheel from the deflection amount εa (θ1s) at the start T1s of the backward grinding until the deflection amount εa (θ1e) becomes zero at the end T1e of the backward grinding. 15 is moved backward while shifting so that the position 15 becomes a position corresponding to the deflection amount εa (θ1s−θ1e) (reference numeral 123 in FIG. 11). That is, by adding the difference Δε with the deflection amount εa (θ1s) in FIG. 10 to the reverse amount in FIG. 12 of the first example, the intermediate reverse amount is determined. According to the second example, the position of the grinding wheel 15 can be made higher with accuracy by shifting the position of the grinding wheel 15 while shifting the position so as to be in a position corresponding to the deflection amount εa (θ1s−θ1e).

  When the amount of bending ε (θ) of the crankpin Wa differs according to the phase θ of the crankpin Wa, the uncut amount after rough advance grinding depends on the amount of bending ε (θ). In particular, it depends on the bending amount εa (θ) due to the grinding resistance Fn. Therefore, as described above, the amount of reverse grinding is determined based on the amount of bending εa (θ1s) of the crank pin Wa due to the grinding resistance Fn at the start T1s of the reverse grinding. Thereby, it can grind with high precision by reverse grinding.

(5. Details of back-off operation)
In the back-off operation (T2s to T2e in FIG. 3), the grinding wheel 15 is further moved backward. The back-off operation is to prevent the grinding wheel 15 from cutting the crankpin Wa even when the coolant supply amount Q is switched from the large flow rate Qmax to the small flow rate Qmin. Here, in the back-off operation, the grinding resistance Fn does not act on the crankpin Wa, and the coolant dynamic pressure Fp acts. Therefore, the crankpin Wa is bent by the coolant dynamic pressure Fp.

  As described above, the rigidity K (θ) of the crankpin Wa varies depending on the phase θ. Further, the coolant dynamic pressure Fp (θ) also changes in accordance with the phase θ as shown in FIG. It can be seen that the coolant dynamic pressure Fp (θ) decreases as the distance from the coolant nozzle 19 increases, and is as shown in FIG. 14 according to FIGS. 2A to 2D. For example, when the phase θ is 90 °, the coolant dynamic pressure Fp is the smallest because the coolant nozzle 19 is farthest from the grinding point P.

  At this time, since the coolant dynamic pressure Fp (θ) varies depending on the phase θ, the deflection amount εb (θ) due to the coolant dynamic pressure Fp (θ) also varies depending on the phase θ. Therefore, the back-off operation is controlled using this deflection amount εb (θ).

Next, regarding the control of the back-off operation using the deflection amount εb (θ), the first example will be described with reference to FIGS. 15 to 17, and the second example will be described with reference to FIGS. 15 and 18 to 19. I will explain.
First, the first example will be described. At the start time T2s (shown in FIG. 3) of the back-off operation, the phase θ2s of the crankshaft W is acquired. The relationship between the phase θ and the deflection amount εb (θ) due to the coolant dynamic pressure Fp (θ) is as shown in FIG. Therefore, the deflection amount εb (θ2s) can be acquired (reference numeral 211 in FIG. 15).

  Subsequently, a back-off amount is determined from the acquired deflection amount εb (θ2s) (reference numeral 212 in FIG. 15). In the first example, a value (ε (θ2s) + δ) obtained by adding a constant value δ to the deflection amount εb (θ2s) at the phase θ2s is set as the backoff amount. The deflection amount εb (θ2s) itself can also be used as the backoff amount. The back-off speed is a predetermined fast feed speed.

  Then, control is performed so that the grinding wheel 15 is moved backward by rapid feed by the determined back-off amount (reference numeral 213 in FIG. 15). From the start time T2s to the end time T2e of the back-off operation, the position of the grinding wheel 15 is as shown in FIG.

  A second example will be described. As shown by hatching in FIG. 18, the amount of deflection εb (θ2s−θ2e) due to the coolant dynamic pressure Fp (θ) corresponding to each phase θ is calculated between the start time T2s and the end time T2e of the back-off operation. (Reference numeral 211 in FIG. 15). Then, a value (ε_max + δ) obtained by adding a constant value δ to the maximum value ε_max of the deflection amount εb (θ2s−θ2e) is set as the backoff amount. Note that the deflection amount ε_max itself can be used as the back-off amount. Then, control is performed so that the grinding wheel 15 is moved backward by rapid feed by the determined back-off amount (reference numeral 213 in FIG. 15). From the start time T2s to the end time T2e of the back-off operation, the position of the grinding wheel 15 is as shown in FIG.

  According to the above, the back-off amount is determined based on the deflection amount ε (θ2s) of the crank pin Wa at the start time T2s of the back-off operation. In particular, since the grinding resistance Fn is already zero at the start time T2s of the back-off operation, the back-off amount is determined based on the deflection amount εb (θ2s) due to the coolant dynamic pressure Fp at the start time T2s. Thereby, even if the back-off amount is reduced, it is possible to prevent the incision from occurring at T3s at the start of finish forward grinding. Since the back-off amount can be reduced as compared with the conventional case, the blank grinding state in finish forward grinding can be reduced, and as a result, the grinding time can be shortened.

In addition, when the first example is applied, the back-off amount can be easily determined, and in this case, the above-described effect is surely obtained.
On the other hand, when the second example is applied, depending on the relationship between the speed of the back-off operation and the peripheral speed of the crankpin Wa, when the maximum value εb_max is larger than the deflection amount εb (θ2s), the maximum back-off operation is performed. It is possible to ensure that no incision occurs inside. As a result, the above-described effect is surely obtained.

  In the above embodiment, the grinding width coefficient H has been described as being constant. However, even when the grinding width coefficient H is changed according to the phase θ, the deflection amount ε changes according to the phase θ. Also in this case, the above concept can be applied in the same manner, and the same effect can be obtained.

1: grinding machine, 15: grinding wheel, A: recess, P: grinding point, Q: coolant supply amount, Qmax: large flow rate, Qmin: small flow rate

Claims (6)

First grinding with a large flow rate of coolant is performed, a back-off operation is performed in an unground state following the first grinding, and a coolant flow rate is decreased after the back-off operation. A grinding machine that performs two grinding operations,
Since at least one of the rigidity K of the workpiece, the coolant dynamic pressure Fp, the grinding efficiency Z, and the grinding width differs according to the phase θ of the workpiece, the workpiece is a grindstone during the first grinding. The pressing force F (θ) in the cutting direction received from the vehicle varies depending on the phase θ, and as a result, the bending amount ε (θ) of the workpiece due to the grinding resistance Fn and the coolant dynamic pressure Fp during the first grinding. Is different depending on the phase θ,
Means for obtaining a deflection amount ε (θ2s) of the workpiece at a phase θ2s of the workpiece at the start time T2s of the back-off operation;
Means for determining a back-off amount based on the deflection amount ε (θ2s);
Means for retreating the back-off amount in the back-off operation;
A grinding machine comprising   The means for determining the back-off amount is the deflection amount ε (θ2s) in the phase θ2s of the workpiece, or a value obtained by adding a constant value to the deflection amount ε (θ2s) as the back-off amount. The grinding machine according to claim 1. The means for obtaining the amount of bending is
A means for calculating a deflection amount ε (θ2s−θ2e) of the workpiece according to each phase θ between the start time T2s and the end time T2e of the backoff operation;
The grinding according to claim 1, wherein the means for determining the back-off amount uses the maximum value ε_max of the deflection amount ε (θ2s-θ2e) or a value obtained by adding a constant value to the maximum value ε_max as the back-off amount. Board.   The grinding machine according to any one of claims 1 to 3, wherein the grinding surface of the workpiece has a recess that is not ground. In the first grinding, first forward grinding is performed in which the grinding wheel is relatively advanced to the workpiece, and following the first forward grinding, the grinding wheel is relatively retracted from the workpiece to reduce the grinding resistance Fn. Perform reverse grinding to zero,
In the back-off operation, the grinding wheel is further moved backward following the backward grinding while the grinding resistance Fn is set to zero.
The grinding machine according to any one of claims 1 to 4, wherein a deflection amount ε (θ2s) of the workpiece is a deflection amount εb (θ2s) of the workpiece due to the coolant. First grinding with a large flow rate of coolant is performed, a back-off operation is performed in an unground state following the first grinding, and a coolant flow rate is decreased after the back-off operation. A grinding method for performing two grindings,
Since at least one of the rigidity K of the workpiece, the coolant dynamic pressure Fp, the grinding efficiency Z, and the grinding width differs according to the phase θ of the workpiece, the workpiece is a grindstone during the first grinding. The pressing force F (θ) in the cutting direction received from the vehicle varies depending on the phase θ, and as a result, the bending amount ε (θ) of the workpiece due to the grinding resistance Fn and the coolant dynamic pressure Fp during the first grinding. Is different depending on the phase θ,
Obtaining a deflection amount ε (θ2s) of the workpiece at a phase θ2s of the workpiece at the start time T2s of the backoff operation;
Determining a backoff amount based on the deflection amount ε (θ2s);
Retreating the back-off amount in the back-off operation;
A grinding method comprising:

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