Grinding machine

Abstract

To process workpieces with a high degree of freedom. [Solution] The grinding machine 10 processes the workpiece W by changing the first relative position between the rotating grinding wheel 11 and the fixed part to which the workpiece W is fixed, while supplying coolant between the rotating grinding wheel 11 and the workpiece W. The grinding machine 10 includes a signal detection unit and a contact position detection unit. The signal detection unit detects a detection signal whose signal value changes when the first relative position is changed in a direction along the workpiece surface, and the rotating grinding wheel 11 switches from a state in which it is not in contact with the workpiece surface with coolant in between to a state in which it is in contact with the workpiece surface. Based on the first relative position when the signal value changes, the contact position detection unit detects a contact position PT that is on the workpiece surface and where the rotating grinding wheel 11 is in contact with the workpiece W.

Description

Technical Field

[0001] The present invention relates to a grinding machine.

Background Art

[0002] Conventionally, a grinding machine that performs grinding processing is known (see Patent Document 1). The grinding machine described in Patent Document 1 includes a rotating grindstone, a table to which a workpiece is fixed, and a position changing device that changes the relative positions of the rotating grindstone and the table. In this grinding machine, the relative positions of the rotating grindstone and the table are changed in the direction along the workpiece processing surface through the operation of the position changing device, whereby the grinding processing of the workpiece by the rotating grindstone is executed.

[0003] Normally, such grinding processing of a workpiece by a rotating grindstone is performed in a state where coolant is supplied between the rotating grindstone and the workpiece processing surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above grinding machine, since the coolant is supplied between the rotating grindstone and the workpiece processing surface during processing, a coolant film (hereinafter referred to as a liquid film) is formed on the workpiece processing surface. Therefore, at the initial stage of processing start, the movement of the rotating grindstone toward the workpiece processing surface side is obstructed by the liquid film, which may cause the rotating grindstone to be temporarily lifted off the workpiece processing surface. Since such a phenomenon is a factor that reduces the processing accuracy of the workpiece by the grinding machine, there is a demand to grasp this phenomenon.

Means for Solving the Problems

[0006] A grinding machine for solving the above problems comprises a rotating grinding wheel, a fixing part for fixing a workpiece, a position changing device for changing the first relative position of the rotating grinding wheel and the fixing part, and a supply unit for supplying coolant between the rotating grinding wheel and the workpiece's machining surface, wherein the workpiece is machined by the rotating grinding wheel by changing the first relative position with the position changing device while the coolant is supplied by the supply unit, and the machine comprises a signal detection unit that detects a detection signal whose signal value changes when the rotating grinding wheel switches from a state in which it is not in contact with the machining surface with the coolant in between to a state in which it is in contact with the machining surface when the first relative position is changed in a direction along the machining surface, and a contact position detection unit that detects a position on the machining surface and where the rotating grinding wheel is in contact with the workpiece, based on the first relative position when the signal value has switched.

[0007] With the above configuration, the contact position where the rotating grinding wheel contacts the workpiece's machining surface can be detected. Based on this contact position, the unmachined portion of the workpiece's machining surface (hereinafter referred to as the unmachined portion) can be identified. This information about the unmachined portion can then be used for inspecting the workpiece (or product) or for changing machining conditions to improve machining accuracy. Thus, with the above configuration, the workpiece can be machined with a high degree of freedom by utilizing the contact position. [Effects of the Invention]

[0008] According to the present invention, workpiece processing can be performed with a high degree of freedom. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a side view of a grinding machine according to one embodiment. [Figure 2] Figure 2 is a block diagram showing the electrical circuit structure of the grinding machine. [Figure 3] Figure 3 is a plan view of the workpiece. [Figure 4]Figure 4 is a side cross-sectional view showing the structure of the first distance sensor, the second distance sensor, and their surroundings. [Figure 5] Figure 5 is a side cross-sectional view showing the structure of the first distance sensor, the second distance sensor, and their surroundings. [Figure 6] Figure 6 is a table showing an example of tabular data. [Figure 7] Figure 7 is a schematic diagram showing an example of image data. [Figure 8] Figure 8 is a schematic diagram showing an example of the relative positional relationship between the rotating grinding wheel and the workpiece during machining. [Figure 9] Figure 9 is a schematic diagram showing the relative positional relationship between the grinding wheel and the workpiece in the unprocessed area and the contact area, respectively. [Figure 10] Figure 10 is a flowchart showing the execution procedure for the shape data creation process. [Modes for carrying out the invention]

[0010] The following description of a grinding machine 10 according to one embodiment will be given with reference to Figures 1 to 10. As shown in Figure 1, the grinding machine 10 is a numerically controlled (NC) surface grinding device that processes the surface of the workpiece W into a flat surface using a rotating grinding wheel 11.

[0011] The rotating grinding wheel 11 is formed in a substantially disc shape. The rotating grinding wheel 11 is supported by the grinding wheel support part 12 in a rotatable state. More specifically, the rotating grinding wheel 11 is connected to the rotating shaft 111. The rotating shaft 111 is supported by the grinding wheel support part 12 in a rotatable state by an oil hydrostatic bearing. The rotating shaft 111 of the rotating grinding wheel 11 extends in the horizontal direction, more specifically in the left-right direction in Figure 1 (hereinafter referred to as the Z direction). In this embodiment, the Z direction corresponds to the third direction.

[0012] The rotating grinding wheel 11 and the grinding wheel support 12 are configured to be movable in the vertical direction (hereinafter referred to as the Y direction) and the Z direction relative to the base 13. In the grinding machine 10, the surface of the workpiece W is ground by rotating the grinding wheel 11 and bringing it into contact with the workpiece W.

[0013] The grinding machine 10 includes a table 14 serving as a fixing portion to which a workpiece W is fixed. The table 14 is configured to be movable relative to a base 13 in a direction orthogonal to the Y direction and the Z direction, specifically, in the depth direction in Figure 1 among horizontal directions (hereinafter referred to as the X direction). In the grinding machine 10, the workpiece W on the table 14 can be moved by moving the table 14 in the X direction. Thereby, the first relative position PA in the X direction between the rotating grinding wheel 11 and the workpiece W can be changed. In the present embodiment, the X direction corresponds to a second direction which is a direction for changing the first relative position PA of the table 14 and the rotating grinding wheel 11 during machining of the workpiece W.

[0014] In the grinding machine 10, the relative position in the X direction, the relative position in the Y direction, and the relative position in the Z direction between the rotating grinding wheel 11 and the workpiece W can be individually changed by moving the rotating grinding wheel 11 in the Y direction or the Z direction, or moving the table 14 in the X direction.

[0015] <Position changing device 20> As shown in Figure 1 and Figure 2, the grinding machine 10 includes a position changing device 20 that changes the first relative position PA of the rotating grinding wheel 11 and the table 14. The position changing device 20 changes the first relative position PA of the rotating grinding wheel 11 and the table 14 by changing the second relative position PM of the grinding wheel support portion 12 and the table 14. The position changing device 20 is constituted by an X-axis drive unit 21, a Y-axis drive unit 22, and a Z-axis drive unit 23.

[0016] The X-axis drive unit 21 is a device for moving the table 14 in the X direction relative to the base 13. The X-axis drive unit 21 includes a ball screw mechanism, a servo motor, and the like. Through operation control of the X-axis drive unit 21, the position of the table 14 in the X direction relative to the base 13 is controlled.

[0017] The Y-axis drive unit 22 is a device that moves the rotating grindstone 11, more specifically the grindstone support unit 12, in the Y direction relative to the base 13. The Y-axis drive unit 22 includes a ball screw mechanism, a servo motor, and the like. Through operation control of the Y-axis drive unit 22, the position of the grindstone support unit 12 in the Y direction relative to the base 13 is controlled. In the present embodiment, the Y direction corresponds to the first direction, which is the direction in which the rotating grindstone 11 is pressed against the machining surface of the workpiece W.

[0018] The Z-axis drive unit 23 is a device for moving the rotating grindstone 11, more specifically the grindstone support unit 12, in the Z direction relative to the base 13. The Z-axis drive unit 23 includes a ball screw mechanism, a servo motor, and the like. Through operation control of the Z-axis drive unit 23, the position of the grindstone support unit 12 in the Z direction relative to the base 13 is controlled.

[0019] The grinding machine 10 has a grindstone drive unit 24 for rotationally driving the rotating grindstone 11. The grindstone drive unit 24 has an electric motor 241 connected to the rotating shaft 111 of the rotating grindstone 11. In the operation control of the grindstone drive unit 24 (more specifically, the electric motor 241), the rotating grindstone 11 is basically rotated at a constant speed. The rotational speed of the rotating grindstone 11 is set to a speed matching the machining conditions, based on the machining conditions input to the grinding machine 10.

[0020] As shown in Figure 3, the machining surface of the workpiece W is divided into a plurality of machining regions (in the example shown in the figure, four machining regions AR1 to AR4) in the Z direction. Then, by sequentially performing the operation of grinding the machining surface by changing the second relative position PM of the grindstone support unit 12 and the table 14 in the X direction for the plurality of machining regions AR1 to AR4 while changing the second relative position PM in the Z direction, the entire surface of the workpiece W is machined.

[0021] <Supply Unit 25> The grinding machine 10 is equipped with a supply unit 25 for supplying coolant CL. The supply unit 25 supplies coolant CL between the rotating grinding wheel 11 and the machining surface of the workpiece W, more specifically, to the machining area where the workpiece W is being machined by the rotating grinding wheel 11, during machining of the workpiece W by the rotating grinding wheel 11. Specifically, the supply unit 25 has a nozzle 251 that discharges coolant CL toward the machining area. The supply unit 25 also includes a tank (not shown) for collecting and storing the coolant CL supplied to the machining area, and a pump (not shown) for pressurizing the coolant CL in the tank and sending it to the nozzle 251.

[0022] <Electronic control unit 30> As shown in Figure 2, the grinding machine 10 is equipped with an electronic control unit 30. The electronic control unit 30 performs various controls related to the operation of the grinding machine 10. A position change device 20, a grinding wheel drive unit 24, and a supply unit 25 are connected to the electronic control unit 30. The electronic control unit 30 has a processing unit (PU), ROM, RAM, a storage unit 31 for storing various programs and data, an operation input unit 32, and a display unit 33.

[0023] The memory unit 31 is composed of a non-volatile memory that allows for on-demand writing and reading, such as a hard disk drive or a solid-state drive. The memory unit 31 stores machining data, which is data used for machining the workpiece W, including setting values ​​for machining conditions and a machining program (so-called NC program) that defines the operating position of the table 14 and the operating position of the rotating grinding wheel 11 using coordinate values. Based on the machining data, the electronic control unit 30 performs numerical control for the grinding process by the grinding machine 10, specifically, it controls the operation of each drive unit 21 to 24. The electronic control unit 30 also controls the operation of the supply unit 25.

[0024] The operation input unit 32 is an input device such as a mouse, keyboard, touch panel, or buttons. In the grinding machine 10, the processing conditions for processing the workpiece W are input to the electronic control unit 30 through the operation of the operation input unit 32 by the operator. In this embodiment, the relationship between the input processing conditions and the control patterns of each drive unit 21 to 24 that are suitable for those processing conditions is determined in advance, and this relationship is stored in advance in the storage unit 31 of the electronic control unit 30. In the grinding machine 10, based on the processing conditions input to the electronic control unit 30 through the operation of the operation input unit 32, the control patterns of each drive unit 21 to 24 are set from the above relationship stored in the storage unit 31. This control pattern is stored in the storage unit 31 as processing operation information (processing program). The electronic control unit 30 controls the operation of each drive unit 21 to 24 by operating each drive unit 21 to 24 based on this processing program.

[0025] The display unit 33 has a display device such as a liquid crystal display or an organic EL display. The display unit 33 displays various information related to the processing of the workpiece W by the grinding machine 10, such as displaying shape data formed by the shape estimation unit 43, which will be described later.

[0026] The grinding machine 10 is equipped with various sensors for detecting its operating state. The detection signals from these sensors are received by the electronic control unit 30. The sensors include a rotational phase sensor 34, an acoustic emission (AE) sensor 37, a first distance sensor 35, and a second distance sensor 36.

[0027] As shown in Figure 1, the rotational phase sensor 34 is attached to the electric motor 241. The rotational phase sensor 34 detects the rotational phase of the rotation axis 111 of the grinding wheel 11 (specifically, the output shaft of the electric motor 241).

[0028] The AE sensor 37 is mounted on the table 14. In the grinding machine 10, when the rotating grinding wheel 11 contacts the machining surface of the workpiece W and the surface is ground, AE waves are emitted from the workpiece W. The AE sensor 37 detects these AE waves emitted from the workpiece W.

[0029] As shown in Figure 4, the first distance sensor 35 and the second distance sensor 36 are attached to the grinding wheel support 12. The first distance sensor 35 and the second distance sensor 36 are, for example, eddy current displacement sensors. The first distance sensor 35 and the second distance sensor 36 are installed to detect the gaps G1 and G2 between the inner surface of the bearing portion 121 of the grinding wheel support 12 and the outer surface of the rotation axis 111 of the rotating grinding wheel 11. Note that in Figure 4, the gaps G1 and G2 are shown exaggerated compared to the actual gaps for ease of understanding.

[0030] The electronic control unit 30 calculates and detects the amount of displacement of the rotating grinding wheel 11 relative to the grinding wheel support 12 in the first direction (hereinafter referred to as the first displacement amount D1) based on the gap G1 in the first direction (Y direction) detected by the first distance sensor 35. In this embodiment, the electronic control unit 30 and the first distance sensor 35 correspond to the first detection unit.

[0031] Furthermore, the electronic control unit 30 calculates and detects the amount of displacement of the rotating grinding wheel 11 relative to the grinding wheel support 12 in the second direction (hereinafter referred to as the second displacement amount D2) based on the gap G2 in the second direction (X direction) detected by the second distance sensor 36. In this embodiment, the second distance sensor 36 corresponds to the second detection unit.

[0032] As described above, the rotating shaft 111 of the rotating grinding wheel 11 is supported in a rotatable state by the grinding wheel support part 12 by an oil hydrostatic bearing. Specifically, the rotating shaft 111 of the rotating grinding wheel 11 is substantially cylindrical and is inserted through a bearing part 121 formed in the grinding wheel support part 12.

[0033] Here, as shown in Figure 5 as an example, it is difficult to make the cross-sectional shape of the rotating shaft 111 a perfect circle. Therefore, the gap G1 in the first direction detected by the first distance sensor 35 and the rotation phase sensor 34 when no processing is taking place, i.e., when no force is being applied to the rotating grinding wheel 11 from the workpiece W, and the gap G1 corresponding to each rotation phase of the rotating grinding wheel 11, are not constant. This variation in gap G1 becomes an error factor in detecting the first displacement amount D1. Similarly, the gap G2 in the second direction detected by the second distance sensor 36 and the rotation phase sensor 34 when no processing is taking place, and the gap G2 corresponding to each rotation phase of the rotating grinding wheel 11, are also not constant. And this variation in gap G2 becomes an error factor in detecting the second displacement amount D2.

[0034] In this embodiment, a value that serves as a reference for detecting the first displacement amount D1 is defined as the first reference position BG1, corresponding to each rotational phase of the rotating grinding wheel 11, or more specifically, the rotating shaft 111 connected to the rotating grinding wheel 11. Specifically, the first reference position BG1 is defined as a value corresponding to the gap G1 when the first displacement amount D1 becomes "0". In addition, a value that serves as a reference for detecting the second displacement amount D2 (specifically, a value corresponding to the gap G2 when the second displacement amount D2 becomes "0") is defined as the second reference position BG2, corresponding to each rotational phase of the rotating grinding wheel 11. The first reference position BG1 and the second reference position BG2 are stored in the storage unit 31 of the electronic control device 30.

[0035] As shown in Figure 2, the electronic control unit 30 includes a first reference position correction unit 41 and a second reference position correction unit 42 as functional units. <First reference position correction section 41> The first reference position correction unit 41 corrects the first reference position BG1 for detecting the first displacement amount D1 based on the gap G1 corresponding to each rotation phase of the rotating grinding wheel 11 detected by the first distance sensor 35 and the rotation phase sensor 34 when not processing. The first reference position BG1 is corrected as follows.

[0036] First, when the rotating grinding wheel 11 is being driven and not being machined, that is, when the rotating shaft 111 is not displaced in the first direction (Y direction) relative to the grinding wheel support 12, the first distance sensor 35 and the rotation phase sensor 34 detect the gap G1 corresponding to each rotation phase of the rotating shaft 111. Then, for each rotation phase, the gap G1 detected at this time is stored as the first reference position BG1. In this way, the first reference position BG1 corresponding to each rotation phase is corrected. This makes it possible to offset the first reference position BG1 corresponding to each rotation phase to match the shape of the rotating shaft 111. Therefore, by subtracting the first reference position BG1 corresponding to a given rotation phase from the gap G1 detected at that rotation phase, the first displacement amount D1 can be detected with high accuracy.

[0037] <Second reference position correction section 42> The second reference position correction unit 42 corrects the second reference position BG2 for detecting the second displacement amount D2 based on the gap G2 corresponding to each rotation phase of the rotating grinding wheel 11 detected by the second distance sensor 36 and the rotation phase sensor 34 when not processing. The second reference position BG2 is corrected as follows.

[0038] First, when the rotating grinding wheel 11 is being driven and not processing, that is, when the rotating shaft 111 is not displaced in the second direction (X direction) relative to the grinding wheel support 12, the second distance sensor 36 and the rotation phase sensor 34 detect the gap G2 corresponding to each rotation phase of the rotating shaft 111. Then, for each rotation phase, the gap G2 detected at this time is stored as the second reference position BG2. In this way, the second reference position BG2 corresponding to each rotation phase is corrected. This allows the second reference position BG2 corresponding to each rotation phase to be offset to match the shape of the rotating shaft 111. For example, in the example shown in Figure 5, the second reference position BG2 corresponding to this rotation phase can be offset by the amount indicated by "ΔBG" in the figure. Therefore, by subtracting the second reference position BG2 corresponding to a given rotation phase from the gap G2 detected at that rotation phase, the second displacement amount D2 can be detected with high accuracy.

[0039] <Contact position detection unit 44> As shown in Figure 2, the electronic control unit 30 includes a contact position detection unit 44 as a functional unit. The contact position detection unit 44 detects the position on the machining surface of the workpiece W, and the position where the rotating grinding wheel 11 contacts the workpiece W after machining of the workpiece W by the rotating grinding wheel 11 has begun (hereinafter referred to as the contact position PT).

[0040] In this embodiment, the first relative position PA of the rotating grinding wheel 11 and the table 14 when the intensity of the AE wave detected by the AE sensor 37 becomes equal to or greater than a predetermined value J is defined as the "detected relative position PAt". The position on the machining surface determined by the detected relative position PAt, and the position on the machining surface where the rotating grinding wheel 11 makes contact, is defined as the "detected position PD". At this time, the contact position detection unit 44 detects the detected position PD as the contact position PT.

[0041] Specifically, after the start of machining, when the intensity of the AE wave detected by the AE sensor 37 exceeds a predetermined value J, it is detected that the workpiece W has emitted an AE wave due to the rotating grinding wheel 11 contacting the machining surface of the workpiece W. By detecting the AE wave emitted by the workpiece W in this way, the contact timing at which the rotating grinding wheel 11 contacts the machining surface of the workpiece W after the start of machining can be determined. The first relative position PA at this contact timing can then be defined as the "detected relative position PAt".

[0042] In the grinding machine 10, the position where the rotary grinding wheel 11 contacts the workpiece W on the machined surface (the so-called machining point) can be determined by the first relative position PA (more specifically, the second relative position PM that determines the first relative position PA, the first displacement amount D1, and the second displacement amount D2). Therefore, the machining point at the contact timing, i.e., the contact position PT where the rotary grinding wheel 11 contacts the machined surface, can be determined and detected by the detected relative position PAt, more specifically, the second relative position PM, the first displacement amount D1, and the second displacement amount D2 at the contact timing. In this embodiment, the contact position PT is stored in the storage unit 31. Also in this embodiment, when the first relative position PA is changed in the X direction along the machined surface, the state in which the rotary grinding wheel 11 is not in contact with the machined surface with coolant CL in between is defined as the non-contact state, and the state in which the rotary grinding wheel 11 is in contact with the machined surface is defined as the contact state. In this embodiment, the AE sensor 37 corresponds to a signal detection unit that detects a detection signal whose signal value changes when it switches from a non-contact state to a contact state while the first relative position PA is changed in the X direction along the processing surface. In this embodiment, the intensity of the AE wave detected by the AE sensor 37 corresponds to the signal value.

[0043] <Shape estimation unit 43> As shown in Figure 2, the electronic control unit 30 includes a shape estimation unit 43 as a functional unit. The shape estimation unit 43 estimates the shape of the machined surface of the workpiece W based on the second relative position PM of the grinding wheel support unit 12 and the table 14, the first displacement amount D1, the second displacement amount D2, and the contact position PT. More specifically, the shape estimation unit 43 creates data (hereinafter referred to as shape data) that shows the shape of the machined surface of the workpiece W. The shape data is data that defines the relationship between the second relative position PM and the displacement position of the rotating grinding wheel 11 relative to the grinding wheel support unit 12 (positional displacement amount ΔPR, described later) which is determined by the first displacement amount D1 and the second displacement amount D2 at the second relative position PM. The shape data is data in which the above relationship is defined separately for multiple second relative positions PM.

[0044] In this embodiment, the shape data consists of "table data," an example of which is shown in Figure 6, and "image data," an example of which is shown in Figure 7. As shown in Figure 6, the table data is data that summarizes the relationship between the second relative position PM, the positional displacement amount ΔPR, and the actual position of the machined surface of the workpiece W (hereinafter referred to as the actual machined surface position PRT) in a table. As shown in Figure 7, the image data is data created by plotting the actual machined surface position PRT corresponding to each second relative position PM on a three-dimensional coordinate system. In this embodiment, the shape data (specifically, the table data and image data) created by the shape estimation unit 43 is stored in the storage unit 31 and output to the display unit 33 for display. According to this embodiment, the shape of the machined surface of the workpiece W can be confirmed in real time during the machining of the workpiece W using the table data and image data displayed on the display unit 33. Furthermore, based on the shape data stored in the storage unit 31, it is also possible to confirm the shape of the machined surface of the workpiece W at any timing after the workpiece W has been machined.

[0045] In this embodiment, the shape estimation unit 43 creates shape data based on the following considerations. Figure 8 shows an example of the relative positional relationship between the workpiece W fixed to the table 14 and the rotating grinding wheel 11. The solid line in Figure 8 shows the position of the rotating grinding wheel 11 when the third relative position PS between the rotating shaft 111 and the grinding wheel support part 12 is misaligned (first displacement D1 ≠ 0, second displacement D2 ≠ 0). The dashed line in Figure 8 shows the position of the rotating grinding wheel 11 when it is assumed that the third relative position PS between the rotating shaft 111 and the grinding wheel support part 12 is not misaligned (first displacement D1 = 0, and second displacement D2 = 0).

[0046] In this embodiment, during the machining of the workpiece W by the grinding machine 10, the second relative position PM of the grinding wheel support 12 and the table 14, the first displacement amount D1, and the second displacement amount D2 are detected at the same timing.

[0047] In this embodiment, the second relative position PM is determined by the relationship between the X-direction position of the table 14, the Y-direction position of the grinding wheel support 12, and the Z-direction position of the grinding wheel support 12. Therefore, as shown by the dashed line in Figure 8, this second relative position PM makes it possible to determine the machining point (hereinafter referred to as the basic machining point PRb) when the rotation axis 111 is not displaced in the Y-direction and X-direction relative to the grinding wheel support 12.

[0048] Furthermore, the first displacement D1 is the displacement of the rotating grinding wheel 11 in the Y direction, and is the displacement of the rotating grinding wheel 11 from the first reference position BG1 relative to the grinding wheel support 12. Therefore, as shown by arrow P1 in Figure 8, this first displacement D1 corresponds to the amount of deviation in the Y direction between the basic machining point PRb and the actual machining point (hereinafter referred to as the actual machining point PRr). Thus, this first displacement D1 makes it possible to determine the "amount of deviation in the Y direction" of the actual machining point PRr from the basic machining point PRb.

[0049] Furthermore, the second displacement D2 is the displacement of the rotating grinding wheel 11 in the X direction, and is the displacement of the rotating grinding wheel 11 from the second reference position BG2 relative to the grinding wheel support 12. Therefore, as shown by arrow P2 in Figure 8, this second displacement D2 corresponds to the amount of deviation in the X direction between the basic machining point PRb and the actual machining point PRr. Thus, this second displacement D2 makes it possible to determine the "amount of deviation in the X direction" of the actual machining point PRr from the basic machining point PRb.

[0050] Based on these considerations, in this embodiment, the position coordinates obtained by shifting the second relative position PM (specifically, the basic machining point PRb) in the Y direction by a first displacement amount D1 indicated by arrow P1 in Figure 8, and in the X direction by a second displacement amount D2 indicated by arrow P2 in Figure 8, are determined as the actual machining point PRr. Then, during the machining of the workpiece W, the actual machining point PRr is determined separately for each of the multiple second relative positions PM.

[0051] In this embodiment, the actual machining point PRr is basically defined as the actual machining surface position PRT. Then, data (shape data) is created that defines the relationship between the second relative position PM and the actual machining surface position PRT separately for multiple second relative positions PM. In this embodiment, the actual machining surface position PRT is one of the data that shows the relationship between the second relative position PM and the displacement amount ΔPR of the rotating grinding wheel 11 relative to the grinding wheel support 12, which is determined by the first displacement amount D1 and the second displacement amount D2 at the second relative position PM.

[0052] In this embodiment, the contact position PT is detected while the workpiece W is being machined by the rotating grinding wheel 11. Based on the contact position PT, the unmachined portion of the machined surface of the workpiece W is identified. Specifically, in each machining region AR1 to AR4, the region behind the detected contact position PT in the direction of travel of the rotating grinding wheel 11 becomes the "unmachined portion".

[0053] As shown in Figure 9, in the unmachined portion, the rotating grinding wheel 11 is sliding on the coolant film CL (hereinafter referred to as the liquid film), or to put it another way, it is floating above the machined surface of the workpiece W. At this time, the rotating grinding wheel 11 is not in contact with the machined surface of the workpiece W. Therefore, the actual machining point PRr, which is determined based on the second relative position PM, the first displacement D1, and the second displacement D2, is shifted in the Y direction (specifically upward) from the actual machined surface position by the thickness of the liquid film. Note that in Figure 9, the thickness of the liquid film is exaggerated compared to its actual thickness for ease of understanding.

[0054] In this embodiment, the actual machined surface position PRT corresponding to the unmachined portion in the shape data is offset towards the side closer to the workpiece W (downward) by the thickness of the liquid film. This allows for accurate determination of the actual machined surface position PRT corresponding to each part of the unmachined portion.

[0055] Specifically, first, the Y-direction position [Y0] of the actual machined surface position PRT at the contact position PT is determined. The Y-direction position [Y0] is determined as the Y-direction position of the actual machined surface position PRT when the rotating grinding wheel 11 contacts the machined surface, that is, when the thickness of the liquid film becomes "0". Then, the Y-direction position [Yr] of the actual machined surface position PRT in each part of the unmachined portion is replaced with the above Y-direction position [Y0].

[0056] In this embodiment, based on the above-described concept, a creation program for generating shape data based on the second relative position PM, the first displacement amount D1, the second displacement amount D2, and the contact position PT is pre-built. This creation program is stored in the storage unit 31. The shape estimation unit 43 creates the shape data by performing calculations based on this creation program.

[0057] <Shape data creation process> The following explains in detail the process of creating shape data (shape data creation process). Figure 10 shows the execution procedure for the shape data creation process. The series of processes shown in the flowchart of Figure 10 are executed by the electronic control device 30 as processes at predetermined intervals, provided that the workpiece W is being machined.

[0058] As shown in Figure 10, this process first determines whether either (Condition A) or (Condition B) is met (Step S11). (Condition A) This is the timing of the first execution of this process after the start of machining of workpiece W.

[0059] (Condition B) A specified period of time has elapsed since the last execution. If both (Condition A) and (Condition B) above are not met (Step S11: NO), the following processes (Steps S12 to S19) will not be executed.

[0060] On the other hand, if either (Condition A) or (Condition B) is met (Step S11: YES), the second relative position PM of the grinding wheel support 12 and the table 14 is captured (Step S12). In addition, the first displacement D1 is detected (Step S13), and the second displacement D2 is detected (Step S14).

[0061] Subsequently, shape data is created based on the second relative position PM, the first displacement amount D1, and the second displacement amount D2 (step S15). Specifically, in this process, the actual machined surface position PRT corresponding to the second relative position PM is determined based on the second relative position PM, the first displacement amount D1, and the second displacement amount D2. Then, the relationship between this actual machined surface position PRT, the second relative position PM, and the positional displacement amount ΔPR is added to the table data (see Figure 6), and the same actual machined surface position PRT is added to the image data (see Figure 7).

[0062] Subsequently, the AE sensor 37 detects the AE wave (step S16), and it is determined whether the intensity of the AE wave has reached or exceeded a predetermined value J at the current execution timing (step S17). In this embodiment, the intensity of the AE wave that allows for proper determination of contact between the rotating grinding wheel 11 and the machined surface of the workpiece W has been determined in advance based on the results of various experiments and simulations conducted by the inventors. The value corresponding to this AE wave intensity is stored in the electronic control device 30 as the predetermined value J.

[0063] Then, if the intensity of the AE wave exceeds a predetermined value J at the current execution timing (step S17: YES), the position coordinates of the machining point determined by the second relative position PM, the first displacement amount D1, and the second displacement amount D2 are detected as the contact position PT (step S18).

[0064] Subsequently, the unprocessed portion of the machined surface is identified based on the contact position PT, and the Y-direction position [Yr] of the actual machined surface position PRT in the unprocessed portion is replaced (corrected) with the Y-direction position [Y0] of the actual machined surface position PRT at the contact position PT (step S19).

[0065] If the process in step S17 is negative (step S17: NO), the processes in steps S18 and S19 will not be executed. Specifically, when the intensity of the AE wave is less than the default value J, or when the intensity of the AE wave remains at or above the default value J, the contact position PT will not be detected, and the correction of the actual machined surface position PRT of the unmachined portion will not be performed.

[0066] In this process, shape data is updated at predetermined intervals during the machining of the workpiece W based on the relationship between the second relative position PM and the positional displacement amount ΔPR (steps S11 to S15). Also, during the machining of the workpiece W, at the timing when the contact position PT is detected, the unmachined portion of the machined surface is identified, and the actual machined surface position PRT of the unmachined portion is offset by the thickness of the liquid film (steps S18 and S19). Through this series of processes, shape data (specifically, table data and image data) showing the shape of the entire machined surface of the workpiece W is created.

[0067] <Operation and Effects of This Embodiment> The operation and effects of this embodiment will be described below. (1) The grinding machine 10 supplies coolant CL between the rotating grinding wheel 11 and the workpiece W, and performs machining of the workpiece W by changing the first relative position PA between the rotating grinding wheel 11 and the table 14 on which the workpiece W is fixed in the X direction along the workpiece W. The contact position detection unit 44 detects the contact position PT, which is the position on the workpiece W's

[0068] With the above configuration, the contact position PT between the rotating grinding wheel 11 and the machined surface of the workpiece W can be detected. Based on this contact position PT, it is possible to identify the unmachined portion of the machined surface of the workpiece W. This information about the unmachined portion can then be used for inspecting the workpiece W (or product) or for changing the machining conditions to improve machining accuracy. Therefore, with the above configuration, the machining of the workpiece W can be performed with a high degree of freedom by utilizing the contact position PT.

[0069] (2) The grinding machine 10 is equipped with an AE sensor 37 that detects AE waves emitted by the workpiece W. The first relative position PA at which the intensity of the AE waves detected by the AE sensor 37 becomes equal to or greater than a predetermined value J is defined as the detected relative position PAt, and the position at which the rotating grinding wheel 11 makes contact on the machining surface determined by the detected relative position PAt is defined as the detected position PD. At this time, the contact position detection unit 44 detects the detected position PD as the contact position PT.

[0070] In the above configuration, when the rotating grinding wheel 11 contacts the machining surface of the workpiece W and grinds the surface, AE waves are emitted from the workpiece W. Therefore, by detecting these AE waves, the contact timing of when the rotating grinding wheel 11 contacts the machining surface of the workpiece W can be determined.

[0071] Furthermore, in the above configuration, the position where the rotary grinding wheel 11 contacts the workpiece W on the machined surface (the so-called machining point) can be determined by the first relative position PA (more specifically, the second relative position PM that determines the first relative position PA, the first displacement amount D1, and the second displacement amount D2). Therefore, the machining point at the contact timing, i.e., the contact position PT where the rotary grinding wheel 11 contacts the machined surface, can be determined and detected by the detected relative position PAt, more specifically, the second relative position PM, the first displacement amount D1, and the second displacement amount D2 at the contact timing.

[0072] As described above, with this configuration, the contact position PT at which the rotary grinding wheel 11 contacts the machined surface after the start of machining of the workpiece W can be detected based on the second relative position PM, first displacement amount D1, and second displacement amount D2 at the contact timing detected through the AE sensor 37.

[0073] (3) The grinding machine 10 includes a grinding wheel support section 12 that rotatably supports a rotating grinding wheel 11, and a position changing device 20 that changes the second relative position PM of the grinding wheel support section 12 and the table 14. The direction in which the rotating grinding wheel 11 is pressed against the machining surface of the workpiece W is defined as the first direction (Y direction), and the direction in which the second relative position PM is changed during machining of the workpiece W is defined as the second direction (X direction). The grinding machine 10 includes a first distance sensor 35, a second distance sensor 36, and a shape estimation unit 43. The first distance sensor 35 detects a first displacement amount D1 of the rotating grinding wheel 11 relative to the grinding wheel support section 12 in the first direction during machining of the workpiece W. The second distance sensor 36 detects a second displacement amount D2 of the rotating grinding wheel 11 relative to the grinding wheel support section 12 in the second direction during machining of the workpiece W. The shape estimation unit 43 estimates the shape of the machined surface of the workpiece W based on the second relative position PM, the first displacement amount D1, the second displacement amount D2, and the contact position PT.

[0074] The position coordinates of each part on the machined surface of the workpiece W are determined by the machining point during machining of the workpiece W. The machining point is basically determined by the second relative position PM between the grinding wheel support 12 and the table 14 (workpiece W). Furthermore, the third relative position PS between the grinding wheel support 12 and the rotating grinding wheel 11 during machining of the workpiece W is not constant and shifts slightly depending on the force that the rotating grinding wheel 11 receives from the workpiece W at the machining point. As the machining point shifts along with this shift in the third relative position PS, this effect becomes apparent in the shape of the machined surface of the workpiece W.

[0075] According to the above configuration, the basic position (the basic machining point PRb) for the position coordinates of each part on the machining surface of the workpiece W can be determined based on the second relative position PM of the grinding wheel support 12 and the table 14. Furthermore, the amount of displacement of the rotating grinding wheel 11 relative to the grinding wheel support 12 during machining of the workpiece W (specifically, the first displacement amount D1 and the second displacement amount D2) can be used as the positional deviation amount ΔPR from the basic machining point PRb. Therefore, according to the above configuration, by determining the position coordinates shifted by the positional deviation amount ΔPR (see arrow P3 in Figure 9) from the basic machining point PRb, the actual position coordinates (the actual machining surface position PRT) of each part on the machining surface of the workpiece W can be estimated. Based on this actual machining surface position PRT, shape data indicating the shape of the machining surface of the workpiece W can be created, and the shape of the machining surface of the workpiece W can be estimated and understood based on that shape data.

[0076] Furthermore, with the above configuration, it is possible to identify the unmachined portion of the workpiece W's machined surface based on the contact position PT. Then, the actual machined surface position PRT corresponding to the unmachined portion in the shape data can be offset towards the workpiece W by the thickness of the liquid film. Therefore, the actual machined surface position PRT corresponding to each part of the unmachined portion can be determined with high accuracy.

[0077] As described above, with this configuration, during the machining of the workpiece W by the grinding machine 10, the second relative position PM, the first displacement amount D1, the second displacement amount D2, and the contact position PT are obtained by the equipment provided by the grinding machine 10, thereby allowing the shape of the machined surface of the workpiece W to be estimated. Therefore, special operations such as temporarily stopping the machining of the workpiece W for inspection, temporarily removing the workpiece W (or product) from the grinding machine 10, or preparing separate inspection equipment are unnecessary, making product inspection easy to perform.

[0078] (4) When the direction perpendicular to the first and second directions is defined as the third direction (Z direction), the rotation axis 111 of the grinding wheel 11 extends in the third direction. The first distance sensor 35 is provided on the grinding wheel support 12 and detects the gap G1 between the rotation axis 111 and the grinding wheel support 12 in the first direction (Y direction) as the first displacement amount D1. The grinding machine 10 includes a rotation phase sensor 34 for detecting the rotation phase of the grinding wheel 11 and a first reference position correction unit 41. The first reference position correction unit 41 corrects the first reference position BG1 corresponding to each rotation phase of the grinding wheel 11 based on the gap G1 corresponding to each rotation phase of the grinding wheel 11 detected by the first distance sensor 35 and the rotation phase sensor 34 when not processing. The first reference position BG1 is a reference position for detecting the first displacement amount D1 and is a reference position determined in accordance with each rotation phase.

[0079] According to the above configuration, the first reference position BG1 corresponding to each rotation phase of the rotating grinding wheel 11 can be offset to match the shape of the rotating shaft 111. Therefore, the first distance sensor 35 can detect the first displacement amount D1 with high accuracy.

[0080] (5) The second distance sensor 36 is provided on the grinding wheel support 12 and detects the gap G2 in the second direction (X direction) between the rotating shaft 111 and the grinding wheel support 12 as the second displacement amount D2. The grinding machine 10 includes a rotation phase sensor 34 that detects the rotation phase of the rotating grinding wheel 11 and a second reference position correction unit 42. The second reference position correction unit 42 corrects the second reference position BG2 corresponding to each rotation phase of the rotating grinding wheel 11 based on the gap G2 corresponding to each rotation phase of the rotating grinding wheel 11 detected by the second distance sensor 36 and the rotation phase sensor 34 when not processing. The second reference position BG2 is the reference position for detecting the second displacement amount D2 and is the reference position corresponding to each rotation phase.

[0081] According to the above configuration, the second reference position BG2 corresponding to each rotation phase of the rotating grinding wheel 11 can be offset to match the shape of the rotating shaft 111. Therefore, the second displacement amount D2 can be detected with high accuracy by the second distance sensor 36.

[0082] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0083] The mounting positions of the first distance sensor 35 and the second distance sensor 36 in the grinding wheel support section 12 can be arbitrarily changed. Furthermore, the first distance sensor 35 and the second distance sensor 36 may be configured using sensors other than eddy current displacement sensors, such as proximity sensors. Essentially, it is sufficient that the first distance sensor 35 can detect the first displacement amount D1 of the rotating grinding wheel 11 relative to the grinding wheel support section 12 in a first direction, and that the second distance sensor 36 can detect the second displacement amount D2 of the rotating grinding wheel 11 relative to the grinding wheel support section 12 in a second direction.

[0084] The first distance sensor 35 and the second distance sensor 36 can be configured using pressure sensors. Here, the rotation axis 111 of the rotating grinding wheel 11 is supported by the grinding wheel support part 12 by an oil hydrostatic bearing. In this oil hydrostatic bearing, oil is filled in the gap between the outer surface of the rotation axis 111 of the rotating grinding wheel 11 and the inner surface of the bearing part 121 of the grinding wheel support part 12. Therefore, when the rotating grinding wheel 11 is displaced relative to the grinding wheel support part 12, the distance of the gap changes, and the hydraulic pressure in the part where the distance has changed changes. When the first distance sensor 35 and the second distance sensor 36 are configured using pressure sensors, the relationship between the distance of the gap and the hydraulic pressure can be obtained from the results of various experiments and simulations and stored in the memory unit 31 in advance. As a result, by detecting the hydraulic pressure with the pressure sensor, the distance of the gap, that is, the distance corresponding to the first displacement amount D1 and the second displacement amount D2, can be determined from the relationship based on the hydraulic pressure.

[0085] The timing for correcting the first reference position BG1 by the first reference position correction unit 41 and the timing for correcting the second reference position BG2 by the second reference position correction unit 42 can be set arbitrarily. For example, the correction by the first reference position correction unit 41 and the correction by the second reference position correction unit 42 can be performed only once when the grinding machine 10 is set up in the factory, or each time the workpiece W is processed.

[0086] • Correction of the first reference position BG1 may be performed by the first reference position correction unit 41, or by inputting the first reference position BG1 corresponding to each predetermined rotation phase through the operation of the operation input unit 32.

[0087] - The correction of the second reference position BG2 may be performed by the second reference position correction unit 42, or by inputting the second reference position BG2 corresponding to each predetermined rotation phase through the operation of the operation input unit 32.

[0088] - Either the first reference position correction unit 41 or the second reference position correction unit 42 can be omitted, or both can be omitted. Instead of the AE sensor 37, a vibration sensor that detects vibrations of the workpiece W (vibrations other than AE waves) or a sound sensor that detects sounds emitted at the machining point may be provided. In this case, for example, it is possible to determine that the rotating grinding wheel 11 has come into contact with the machining surface when the intensity of the vibration waves detected by the vibration sensor or sound sensor during machining of the workpiece W exceeds a predetermined value. Furthermore, it is not limited to determining whether the rotating grinding wheel 11 has come into contact with the machining surface based on the AE waves detected by the AE sensor 37, but can also be determined based on the load of the X-axis drive unit 21 (specifically, the servo motor) or based on the rotational speed of the rotating grinding wheel 11. For example, during machining of the workpiece W, it is possible to determine whether the rotating grinding wheel 11 has come into contact with the machining surface when the increase in the load of the X-axis drive unit 21 (specifically, the servo motor) per unit time exceeds a predetermined value. Alternatively, during machining of the workpiece W, it is possible to determine whether the rotating grinding wheel 11 has come into contact with the machining surface when the decrease in the rotational speed of the rotating grinding wheel 11 per unit time exceeds a predetermined value.

[0089] The shape data created by the shape estimation unit 43 can be arbitrarily modified, as long as it is data that can estimate the shape of the machined surface of the workpiece W. For shape data, for example, only one of tabular data or image data can be used. Furthermore, as tabular data, only the second relative position PM and positional displacement ΔPR may be summarized in a table, or only the actual machined surface position PRT at each part of the machined surface of the workpiece W may be summarized in a table, or the relationship between the basic machining point PRb and the actual machined surface position PRT may be summarized in a table. In addition, the shape data may include contact position PT. With this configuration, the unmachined portion of the machined surface of the workpiece W can be identified based on the contact position PT.

[0090] Furthermore, the shape data may include data indicating that a portion is unprocessed. With this configuration, it is possible to determine that the workpiece W (or product) is defective if there is an unprocessed portion, to change the processing conditions so that the unprocessed portion is eliminated, or to determine that the processing accuracy is low for the unprocessed portion of each part of the processed surface.

[0091] In addition, it is possible to use data that combines image data and tabular data as shape data. In this case, for example, when the cursor is placed over the image displayed on the display unit 33 (the image corresponding to the shape data), the position coordinates and positional displacement amount ΔPR (first displacement amount D1, second displacement amount D2) of that part may be displayed.

[0092] • In the shape estimation process, the step of offsetting the actual machined surface position PRT of the unmachined portion by the thickness of the liquid film (step S19 in Figure 10) may be omitted. • A machine learning model may be used to create shape data. For example, a machine learning model can be used that takes the second relative position PM, first displacement D1, second displacement D2, and contact position PT as input variables and outputs shape data showing the shape of the machined surface of the workpiece W. Alternatively, a machine learning model can be used that takes image data created through the shape data creation process as input variables and outputs final image data showing the shape of the machined surface of the workpiece W. In such cases, a supervised trained model that has been trained with correct answers provided to the training data can be used as the machine learning model.

[0093] The grinding machine 10 according to the above embodiment can also be applied to a grinding machine in which the rotation axis 111 of the rotating grinding wheel 11 extends in the Y direction. The grinding machine 10 according to the above embodiment can also be applied to grinding machines in which the rotation axis 111 of the rotating grinding wheel 11 is supported by a fluid bearing other than an oil hydrostatic bearing, such as a grinding machine in which the rotation axis 111 of the rotating grinding wheel 11 is supported by an air hydrostatic bearing.

[0094] The grinding machine 10 according to the above embodiment is not limited to a surface grinding machine, but can also be applied to a grinding machine that grinds the workpiece surface W into a curved surface. <Note> The above embodiment includes the configuration described in the following appendix.

[0095] [Note 1] A grinding machine comprising: a rotating grinding wheel; a fixing part for fixing a workpiece; a position changing device for changing the first relative position of the rotating grinding wheel and the fixing part; and a supply unit for supplying coolant between the rotating grinding wheel and the workpiece's machining surface, wherein the workpiece is machined by the rotating grinding wheel by changing the first relative position using the position changing device while the coolant is supplied by the supply unit, and the machine further comprising: a signal detection unit for detecting a detection signal whose signal value changes when the rotating grinding wheel switches from a state in which it is not in contact with the machining surface with the coolant in between to a state in which it is in contact with the machining surface when the first relative position is changed in a direction along the machining surface; and a contact position detection unit for detecting a position on the machining surface and where the rotating grinding wheel is in contact with the workpiece, based on the first relative position when the signal value has switched.

[0096] [Note 2] The grinding machine as described in [Appendix 1], wherein the signal detection unit is an AE sensor that detects AE waves emitted by the workpiece, the signal value is the intensity of the AE waves, the first relative position when the intensity of the AE waves detected by the AE sensor exceeds a predetermined value is defined as the detection relative position, and the position where the rotating grinding wheel makes contact on the machining surface determined by the detection relative position is defined as the detection position, the contact position detection unit detects the detection position as the contact position.

[0097] [Note 3] The grinding machine, as described in [Note 1] or [Note 2], comprises a grinding wheel support that rotatably supports the rotating grinding wheel, the position changing device changes the second relative position of the grinding wheel support and the fixed part, and the grinding machine comprises a first detection unit that detects a first displacement amount of the rotating grinding wheel with respect to the grinding wheel support in a first direction in which the rotating grinding wheel is pressed against the workpiece surface during processing of the workpiece, a second detection unit that detects a second displacement amount of the rotating grinding wheel with respect to the grinding wheel support in a second direction in which the second relative position is changed by the position changing device during processing of the workpiece, and a shape estimation unit that estimates the shape of the workpiece surface based on the second relative position, the first displacement amount, the second displacement amount, and the contact position.

[0098] [Note 4] When the direction perpendicular to the first and second directions is defined as the third direction, the rotation axis of the rotating grinding wheel extends in the third direction, the first detection unit is provided on the grinding wheel support and is a first distance sensor that detects the gap between the rotation axis and the grinding wheel support in the first direction as the first displacement amount, the grinding machine comprises a phase sensor that detects the rotation phase of the rotating grinding wheel, and a first reference position correction unit that is a first reference position for detecting the first displacement amount and corrects the first reference position corresponding to each rotation phase based on the gap corresponding to each rotation phase of the rotating grinding wheel detected by the first distance sensor and the phase sensor when not processing, the grinding machine as described in [Appendix 3].

[0099] [Note 5] When the direction perpendicular to the first and second directions is defined as the third direction, the rotation axis of the grinding wheel extends in the third direction, the second detection unit is provided on the grinding wheel support and is a second distance sensor that detects the gap between the rotation axis and the grinding wheel support in the second direction as the second displacement amount, the grinding machine comprises a phase sensor that detects the rotation phase of the grinding wheel, and a second reference position correction unit that is a second reference position for detecting the second displacement amount and corrects the second reference position corresponding to each rotation phase based on the gap corresponding to each rotation phase of the grinding wheel detected by the second distance sensor and the phase sensor when not processing, the grinding machine according to [Note 3] or [Note 4]. [Explanation of Symbols]

[0100] W...work D1...First displacement D2...Second displacement PA...First relative position PM...Second relative position PS...Third relative position 10… Grinding machine 11… Rotary grinding wheel 111... Rotation axis 12…Grinding wheel support section 121...Bearing part 13…Base 14... Table 20... Position change device 21...X-axis drive unit 22...Y-axis drive unit 23...Z-axis drive unit 24…Grinding wheel drive unit 241… Electric motor 25...Supply section 251…Nozzle 30…Electronic control unit 31...Storage section 32... Operation input section 33…Display section 34…Rotational phase sensor 35…First distance sensor 36…Second distance sensor 37…AE Sensor 41...First reference position correction section 42…Second reference position correction section 43...Shape estimation section 44... Contact position detection unit

Claims

1. A grinding machine comprising a rotating grinding wheel, a fixing part for which a workpiece is fixed, a position changing device for changing the first relative position of the rotating grinding wheel and the fixing part, and a supply unit for supplying coolant between the rotating grinding wheel and the machined surface of the workpiece, wherein the first relative position is changed by the position changing device while the coolant is supplied by the supply unit, and the workpiece is machined by the rotating grinding wheel, A signal detection unit that detects a detection signal whose signal value changes when the first relative position is changed in a direction along the machining surface, and the state in which the rotating grinding wheel is not in contact with the machining surface with the coolant in between changes from a state in which the rotating grinding wheel is in contact with the machining surface, A grinding machine comprising: a contact position detection unit that detects a position on the machining surface and a contact position where the rotating grinding wheel contacts the workpiece, based on the first relative position when the signal value changes.

2. The signal detection unit is an AE sensor that detects AE waves emitted by the workpiece. The aforementioned signal value is the intensity of the AE wave. When the intensity of the AE wave detected by the AE sensor becomes greater than or equal to a predetermined value, the first relative position is defined as the detected relative position, and the position on the machining surface determined by the detected relative position where the rotating grinding wheel makes contact is defined as the detection position, The contact position detection unit detects the detected position as the contact position. The grinding machine according to claim 1.

3. The rotating grinding wheel is supported by a grinding wheel support section, The position changing device changes the second relative position of the grinding wheel support and the fixing part. The aforementioned grinding machine, A first detection unit detects a first displacement amount of the rotating grinding wheel relative to the grinding wheel support in a first direction in which the rotating grinding wheel is pressed against the machining surface during the machining of the workpiece, During the machining of the workpiece, a second detection unit detects the second displacement amount of the rotating grinding wheel relative to the grinding wheel support in the second direction in which the second relative position is changed by the position changing device, The system includes a shape estimation unit that estimates the shape of the machined surface based on the second relative position, the first displacement, the second displacement, and the contact position. The grinding machine according to claim 1 or 2.

4. When the direction perpendicular to the first and second directions is defined as the third direction, The rotation axis of the aforementioned grinding wheel extends in the third direction, The first detection unit is provided on the grinding wheel support unit and is a first distance sensor that detects the gap between the rotation axis and the grinding wheel support unit in a first direction as the first displacement amount. The aforementioned grinding machine, A phase sensor for detecting the rotational phase of the rotating grinding wheel, The system includes a first reference position correction unit that corrects the first reference position corresponding to each rotation phase of the grinding wheel, which is a first reference position for detecting the first displacement amount, based on the gap corresponding to each rotation phase detected by the first distance sensor and the phase sensor when not processing, The grinding machine according to claim 3.

5. When the direction perpendicular to the first and second directions is defined as the third direction, The rotation axis of the aforementioned grinding wheel extends in the third direction, The second detection unit is provided on the grinding wheel support unit and is a second distance sensor that detects the gap between the rotation axis and the grinding wheel support unit in the second direction as the second displacement amount. The aforementioned grinding machine, A phase sensor for detecting the rotational phase of the rotating grinding wheel, The system includes a second reference position correction unit that corrects the second reference position corresponding to each rotation phase of the grinding wheel, which is a second reference position for detecting the second displacement amount, based on the gap corresponding to each rotation phase detected by the second distance sensor and the phase sensor when not processing, The grinding machine according to claim 3.

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