Honing method

Abstract

To restrain wear of a grindstone when performing honing processing.SOLUTION: A honing processing method includes a first step of determining a unit feed quantity based on a surface roughness of an inner peripheral surface of a workpiece and projection heights of abrasive grains on a grindstone used by being attached to a honing head, and a second step of processing the workpiece by starting rotation of the grindstone from a state where the grindstone and the workpiece are not in contact with each other, and gradually increasing a radius of rotation of the grindstone for each unit feed quantity in response to a change in grinding resistance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a honing method. [Background technology]

[0002] Generally, in a cylinder block to be mounted on a vehicle, the inner peripheral surface of the bore is honed during manufacturing or restoration. As described in Patent Document 1, in the honing process, the honing head rotates while the grinding stone provided on the honing head is expanded radially and pressed against the inner peripheral surface of the bore, thereby grinding the inner peripheral surface of the bore. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-175574 Summary of the Invention [Problem to be solved by the invention]

[0004] In a typical honing process, the cylinder head is expanded at a constant speed until the grinding resistance exceeds a threshold value, confirming contact between the grinding wheel and the bore. However, when machining a bore whose inner circumferential surface has become highly uneven due to aging or other factors, localized contact between the grinding wheel and the bore can occur. In this case, excessive load is applied to the grinding wheel, causing abrasive grains to fall off locally, which can result in significant wear of the grinding wheel. Furthermore, this problem is not limited to bore sections, but is common to all honing processes that grind surfaces with high surface roughness. [Means for solving the problem]

[0005] The technology of the present disclosure can be realized in the following forms. [Feature 1] A honing method, An acquisition step of acquiring the surface roughness of the inner peripheral surface of the workpiece and the protruding height of the abrasive grains of the grinding stone attached to the honing head; Surface roughness and The aforementioned and a second step of starting rotation of the grinding wheel from a state in which the grinding wheel and the workpiece are not in contact with each other, and gradually expanding the rotation radius of the grinding wheel for each unit feed amount in accordance with changes in grinding resistance to process the workpiece, wherein the first step includes a step of determining, as the unit feed amount, a feed amount smaller than the protrusion height when the surface roughness is greater than the protrusion height, and determining, as the unit feed amount, a feed amount equal to the protrusion height when the surface roughness is equal to or less than the protrusion height.

[0006] (1) According to one aspect of the present disclosure, there is provided a honing method comprising: a first step of determining a unit feed rate based on the surface roughness of the inner peripheral surface of a workpiece and the protruding height of abrasive grains in a grinding wheel attached to a honing head; and a second step of starting rotation of the grinding wheel from a state in which the grinding wheel and the workpiece are not in contact with each other, and gradually expanding the rotation radius of the grinding wheel for each unit feed rate in response to changes in grinding resistance, thereby machining the workpiece. According to this form of honing method, the radius of rotation of the grinding wheel is gradually expanded for each unit feed amount, so that the convex portion on the inner peripheral surface of the bore portion can be gradually ground away, thereby preventing excessive localized grinding resistance and suppressing wear on the grinding wheel. (2) In the above embodiment, the second step may include the step of expanding the rotation radius by the unit feed amount each time the grinding resistance decreases by a predetermined displacement width. According to this form of honing method, the rotation radius of the grinding wheel is expanded by the unit feed amount each time the grinding resistance decreases by a predetermined displacement amount, thereby preventing a sudden increase in grinding resistance and further reducing wear on the grinding wheel. (3) In the above embodiment, the first step may include a step of determining a feed amount smaller than the protrusion height as the unit feed amount when the surface roughness is greater than the protrusion height, and determining a feed amount equal to the protrusion height as the unit feed amount when the surface roughness is equal to or less than the protrusion height. According to this honing method, when the surface roughness of the workpiece is greater than the protruding height of the abrasive grains, the unit feed rate is set to a rate smaller than the protruding height of the abrasive grains, thereby reducing grinding resistance and suppressing wear on the grinding stone.On the other hand, when the surface roughness of the workpiece is equal to or smaller than the protruding height of the abrasive grains, the unit feed rate is set to a rate equal to the protruding height of the abrasive grains, thereby suppressing a decrease in grinding efficiency. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a honing device according to an embodiment of the present invention; [Figure 2] 10 is a flowchart showing the procedure of the first half of a honing process. [Figure 3] 10 is a flowchart showing the procedure of the latter half of the honing process. [Figure 4] 10 is a flowchart showing the procedure of a fixed amount expansion process. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Implementation: A1.Device configuration: 1 is an explanatory diagram showing the schematic configuration of a honing device 1000 of this embodiment. Honing device 1000 includes a honing head 100, a drive unit 200, and a control unit 300. Honing device 1000 grinds the inner peripheral surface of bore portion Wb by moving honing head 100 up and down while rotating it, with honing head 100 in contact with the inner peripheral surface of bore portion Wb of cylinder block W.

[0009] The honing head 100 includes a grinding unit 110 and a rod 120. The grinding unit 110 includes a head body 111 and multiple grinding stones 112. The head body 111 has a cylindrical shape, and multiple grinding stones 112 are provided on its outer periphery at equal intervals along the periphery. The head body 111 has a grinding stone extension mechanism (not shown) that allows the grinding stones 112 to protrude from the outer periphery of the head body 111, thereby expanding the rotation radius of the grinding stones 112 during grinding. In this embodiment, the operator adjusts the amount of protrusion of the grinding stones 112 by adjusting the amount of rotation of a ball screw (not shown) provided in the main body of the honing device 1000.

[0010] The rod 120 is a cylindrical member, and is connected at one end to the grinding part 110 so that the central axis of the rod 120 and the central axis of the grinding part 110 coincide with each other.

[0011] The drive unit 200 has a grindstone rotation unit 210 that rotates around a rotation axis C. The other end of the rod 120 is attached to the grindstone rotation unit 210 so that it can rotate relative to the drive unit 200 and so that the central axis of the rod 120 coincides with the rotation axis C. The grindstone rotation unit 210 rotates the rod 120 around the rotation axis C, thereby rotating the grinding unit 110. The drive unit 200 is configured to be movable in the up and down direction along the main body of the honing device 1000. The drive unit 200 moves in the up and down direction, thereby moving the grinding unit 110 and the rod 120 in the up and down direction.

[0012] The control unit 300 is configured by a computer having a CPU and memory. The CPU of the control unit 300 executes a honing processing program stored in advance in the memory, thereby controlling the rotation and vertical movement of the drive unit 200 and executing the honing processing step described below.

[0013] A2.Honing process: The honing process of this embodiment is performed to hone the inner peripheral surface of the bore portion Wb, the surface roughness of which has increased due to aging or the like, to a predetermined surface roughness. Figure 2 is a flowchart showing the procedure for the first half of the honing process. Figure 3 is a flowchart showing the procedure for the second half of the honing process.

[0014] 2, the worker measures the surface roughness of the inner peripheral surface of the bore portion Wb and estimates the height Hp of the protrusions on the surface of the inner peripheral surface. In this embodiment, the worker performs the surface roughness measurement using a stylus-type surface roughness measuring instrument.

[0015] In step S120, the operator checks the protruding height Ha of the abrasive grains from the surface of the grindstone. The protruding height Ha of the abrasive grains is estimated from the specifications of the grindstone, such as the grain size of the abrasive grains.

[0016] In step S130, the worker determines a unit feed amount Fp, which is the amount of expansion of the radius of rotation of the grinding wheel 112 per rotation. In this embodiment, if the protrusion height Hp is greater than the abrasive grain protrusion height Ha, the worker determines half of the abrasive grain protrusion height Ha as the unit feed amount Fp. Also, if the protrusion height Hp is equal to or less than the abrasive grain protrusion height Ha, the worker determines the abrasive grain protrusion height Ha as the unit feed amount Fp. This step corresponds to the "first process" in this disclosure.

[0017] In step S140, the worker determines a specified number of extensions Nf, which is the number of times N the rotation radius of the grindstone 112 needs to be extended in order to remove the protrusion with the protrusion height Hp. The worker determines the specified number of extensions Nf based on the protrusion height Hp and the unit feed amount Fp. Specifically, for example, if the value obtained by dividing the protrusion height Hp by the unit feed amount Fp is 5.2, the worker determines the specified number of extensions Nf to be 6.

[0018] In step S150, the operator sets the rotation speed of the grindstone rotation unit 210 and the expansion speed at which the rotation radius of the grindstone 112 is expanded by a fixed amount. The rotation speed and the expansion speed are determined by a known method depending on the material of the grindstone 112 and the workpiece to be processed.

[0019] In step S160, the worker operates the honing device 1000 to move the grinding part 110 into the bore part Wb, which is the processing position.

[0020] In step S170, the worker expands the grinding wheel 112 to contact the inner circumferential surface of the bore portion Wb, and then retracts the expanded grinding wheel 112 a predetermined distance. In this embodiment, the worker expands the grinding wheel 112 by rotating the ball screw described above, and the point at which the expansion stops is the point of contact with the bore portion Wb.

[0021] In step S180, the operator activates the torque sensor of the honing device 1000 and starts collecting grinding load data. In this embodiment, the honing device 1000 detects voltage changes of the motor that rotates the grindstone rotation part 210 as torque changes using the torque sensor, and records the changes in the grinding load.

[0022] In step S190, the operator operates the honing device 1000 to start discharging the coolant and rotating the grinding wheel 112. In this embodiment, a water-soluble cutting oil is used as the coolant. The rotation speed of the grinding wheel 112 is determined according to the size of the inner diameter of the bore portion Wb, the specifications of the grinding wheel 112 to be used, and the like.

[0023] In step S200, the operator performs a fixed-quantity expansion step. The fixed-quantity expansion step corresponds to the "second step" in this disclosure. Figure 4 is a flowchart showing the procedure of the fixed-quantity expansion step.

[0024] In step S210, the operator sets the current number of extensions N to 0 and starts counting the number of extensions N.

[0025] In step S220, the operator operates the honing device 1000 to expand the expansion radius of the grindstone 112 by the unit feed amount Fp, and increments the expansion count N by 1 (step S230).

[0026] If the extension count N is less than the specified extension count Nf (step S240: Yes), the operator waits until the grinding resistance decreases by a predetermined displacement amount (step S250: No). The "predetermined displacement amount" is set to a value that is determined in advance by experiment or simulation as the amount of reduction in grinding resistance when the protrusion is ground to a predetermined height.

[0027] If the grinding resistance has decreased by a predetermined displacement amount (step S250: Yes), the operator executes step S220 again. The operator repeats steps S220 to S250 until the number of extensions N reaches the specified number of extensions Nf. If the number of extensions N reaches the specified number of extensions Nf (step S240: No), the operator ends the fixed quantity extension process.

[0028] After the quantitative expansion step is completed, in step S310 of FIG. 2, the operator ends the collection of grinding resistance data.

[0029] In step S320, the operator records the expansion end position of the grinding wheel 112 at the end of the fixed amount expansion process.

[0030] In step S330 of FIG. 3, the operator operates the honing device 1000 to stop the grindstone rotation and the coolant, contract the expanded grindstone 112, and retract the grinding portion 110 from the bore portion Wb.

[0031] In step S340, the operator visually checks the machined surface of the bore portion Wb and determines whether the visual check results are good (step S350). The operator determines that the machined surface is good if the operator visually checks that the machined surface is free of irregularities or if a uniform crosshatch is formed on the machined surface.

[0032] If the visual inspection results are good (step S350: Yes), the worker measures the surface roughness of the machined surface of the bore portion Wb (step S360) and determines whether the surface roughness is below a preset threshold value (step S370).

[0033] If the visual inspection result is not good (step S350: No), or if the surface roughness of the machined surface of the bore portion Wb is greater than the threshold value (step S370: No), the operator determines that additional honing is necessary and re-determines the specified number of expansion times Nf (step S352).

[0034] In step S362, the worker operates the honing device 1000 to move the grinding part 110 back into the bore part Wb, which is the processing position.

[0035] In step S372, the operator operates honing device 1000 to expand the rotation radius of grinding wheel 112 to the expansion end position at the end of the previous processing, which was recorded in step S320. Then, the operator executes step S180 again. The operator repeats steps S180 to S370 until the surface roughness of the processed surface of bore portion Wb becomes equal to or less than the threshold value in step S370. If the surface roughness of the processed surface of bore portion Wb is equal to or less than the predetermined threshold value (step S370: Yes), the operator ends the honing process.

[0036] According to the honing method described above, the radius of rotation of the grinding wheel 112 is gradually increased for each unit feed amount Fp, thereby gradually grinding the convex portion on the inner peripheral surface of the bore portion Wb, thereby preventing excessive localized grinding resistance and suppressing wear on the grinding wheel 112.

[0037] In addition, the operator expands the rotation radius of the grinding wheel 112 by the unit feed amount Fp each time the grinding resistance decreases by a predetermined displacement amount, thereby preventing a sudden increase in grinding resistance and further reducing wear on the grinding wheel 112.

[0038] Furthermore, when the surface roughness of the workpiece is greater than the abrasive grain protrusion height Ha, the operator sets the unit feed amount Fp to a feed amount smaller than the abrasive grain protrusion height Ha, thereby further reducing the load on the grinding wheel 112 and further suppressing wear on the grinding wheel 112. On the other hand, when the surface roughness of the workpiece is equal to or smaller than the abrasive grain protrusion height Ha, the operator sets the unit feed amount Fp to a feed amount equal to the abrasive grain protrusion height Ha, thereby suppressing a decrease in grinding efficiency.

[0039] B. Other Embodiments (B1) In the above embodiment, the honing process is performed to adjust the inner circumferential surface of the bore portion Wb, which has become rough due to aging or the like, to a predetermined surface roughness by honing. However, the present disclosure is not limited to this. The honing process may be performed during the manufacture of the cylinder block W.

[0040] (B2) In the above embodiment, when the protrusion height Hp is greater than the abrasive grain protrusion height Ha, the operator determines the unit feed rate Fp to be half of the abrasive grain protrusion height Ha, but the present disclosure is not limited to this. When the protrusion height Hp is greater than the abrasive grain protrusion height Ha, the operator may set the unit feed rate Fp to any feed rate smaller than the abrasive grain protrusion height Ha. For example, the operator may set the unit feed rate Fp to be 1 / 3 of the abrasive grain protrusion height Ha.

[0041] (B3) In the above embodiment, the honing device 1000 executes the above-described fixed-quantity expansion process in response to an operator's operation, but the present disclosure is not limited to this. The honing device 1000 may execute the fixed-quantity expansion process automatically by executing a program pre-stored in the control unit 300. With this configuration, the operator's operation in the fixed-quantity expansion process is not required, thereby suppressing a decrease in production efficiency.

[0042] (B4) In the above embodiment, the operator extends the rotation radius of the grinding wheel 112 every time the grinding resistance decreases by a predetermined displacement amount, but the present disclosure is not limited to this. The operator may extend the rotation radius of the grinding wheel 112 every time a predetermined time elapses.

[0043] (B5) In the above embodiment, when the surface roughness of the workpiece is greater than the abrasive grain protrusion height Ha, the operator determines a feed rate smaller than the abrasive grain protrusion height Ha as the unit feed rate Fp, and when the surface roughness is equal to or less than the abrasive grain protrusion height Ha, the operator determines a feed rate equal to the abrasive grain protrusion height Ha as the unit feed rate Fp, but the present disclosure is not limited to this. When the surface roughness of the workpiece is greater than the abrasive grain protrusion height Ha, the operator may determine a feed rate equal to the abrasive grain protrusion height Ha as the unit feed rate Fp, and when the surface roughness is equal to or less than the abrasive grain protrusion height Ha, the operator may determine a feed rate greater than the abrasive grain protrusion height Ha as the unit feed rate Fp.

[0044] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0045] 100... Honing head, 110... Grinding part, 111... Head body, 112... Grinding stone, 120... Rod, 200... Drive part, 210... Grinding stone rotating part, 300... Control part, 1000... Honing device, C... Rotating shaft, Fp... Unit feed amount, Ha... Abrasive grain protrusion height, Hp... Protrusion height, N... Number of expansions, Nf... Specified number of expansions, W... Cylinder block, Wb... Bore part

Claims

1. A honing method, comprising: an acquiring step of acquiring the surface roughness of the inner peripheral surface of the workpiece and the protruding height of abrasive grains in a grinding stone attached to a honing head; a first step of determining a unit feed amount based on the surface roughness and the protrusion height; a second step of starting rotation of the grinding wheel from a state where the grinding wheel and the workpiece are not in contact with each other, and gradually expanding the rotation radius of the grinding wheel for each unit feed amount in response to a change in grinding resistance, thereby processing the workpiece; Equipped with the first step includes a step of determining, as the unit feed amount, a feed amount smaller than the protrusion height when the surface roughness is greater than the protrusion height, and determining, as the unit feed amount, a feed amount equal to the protrusion height when the surface roughness is equal to or less than the protrusion height, Honing method.

2. The honing method according to claim 1, the second step includes a step of expanding the rotation radius by the unit feed amount every time the grinding resistance decreases by a predetermined displacement width. Honing method.

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