Processing apparatus

Abstract

To provide a processing apparatus capable of improving accuracy of dressing for shaping a tool for processing a workpiece.SOLUTION: A gear grinding apparatus 10 comprises: a grinding wheel 20 for processing a workpiece W; a dressing tool that can be relatively brought into contact with and separated from the grinding wheel 20 and that performs dressing to shape the grinding wheel 20 by cutting the grinding wheel 20 by a predetermined cutting amount from a dressing reference position; an AE sensor whose output level changes in accordance with contact between the grinding wheel 20 and the dressing tool; and a control unit that detects contact between the grinding wheel 20 and the dressing tool on the basis of an output of the AE sensor. The control unit, at a stage prior to performing the dressing, relatively brings the grinding wheel 20 and the dressing tool closer to each other, detects contact between the grinding wheel 20 and the dressing tool on the basis of the output of the AE sensor, and determines the dressing reference position on the basis of information on the detected contact position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a processing device, and more particularly to a measure for improving the accuracy of dressing in which a tool for processing a workpiece is shaped by a dressing tool. [Background technology]

[0002] For example, as disclosed in Patent Document 1, a processing device such as a gear grinding device is provided with a tool (e.g., a grinding wheel) for processing (grinding) a workpiece (e.g., a gear), and when the number of times the tool has processed the workpiece reaches a predetermined number of times, a dressing tool is used to shape the tool for dressing. By performing this dressing, the processing accuracy of the workpiece by the tool is maintained.

[0003] Specifically, in dressing in a gear grinding device, a cylindrical grinding wheel and a dressing tool having a rotation axis parallel to the rotation axis of the grinding wheel are opposed to each other so that they can be moved relatively close to each other, and the two are brought into contact from a reference position for starting dressing (for example, by bringing the grinding wheel closer to the dressing tool by a predetermined distance), so that the dressing tool cuts into the grinding wheel by a predetermined cutting depth to shape the grinding wheel.

[0004] Then, after dressing is completed, when grinding the gear with the grinding wheel, it is assumed that the outer diameter of the grinding wheel has become smaller by the amount of cut-in due to dressing, and the position of the grinding wheel is advanced toward the workpiece (gear) by the amount of cut-in (calculated amount) relative to the position before dressing (the grinding wheel is brought closer to the workpiece), and grinding of the workpiece begins. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-269815 [Patent Document 2] Japanese Patent Publication No. 2020-199620 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, dressing is performed every time a predetermined number of gear grinding processes are performed with a grinding wheel. However, during repeated gear grinding processes (between the previous dressing and the current dressing), the center distance between the grinding wheel and the dressing tool may change. This can be caused by thermal expansion of various parts of the processing equipment due to changes in the temperature of the machine body and cutting oil caused by changes in room temperature, or changes in the temperature of the cutting oil caused by heat emitted from the high-pressure coolant pump and grinding heat. Another example is the tilt of the unit's support column (commonly called a column) caused by the horizontality of the top surface of the base of the unit supporting the grinding wheel being affected by heat. For example, the center distance increases as the temperature of the equipment increases, and conversely, decreases as the temperature of the equipment decreases.

[0007] If the center distance between the grinding wheel and the dressing tool changes in this way, the reference position for the actual start of dressing will change from the calculated reference position, and the amount of cutting into the grinding wheel by the dressing tool may deviate from the target amount by that amount. In other words, the shape of the grinding wheel after forming (the finished diameter of the grinding wheel) may deviate from the calculated value. This deviation in the shape of the grinding wheel affects the amount of gear machining by the grinding wheel afterwards, leading to issues such as the gear's OBD (over ball diameter) deviating from the design value.

[0008] One solution to this problem is to measure the center distance using a touch probe or touch sensor and reflect the difference between this center distance and the previous value as a correction amount for the cutting depth during dressing. However, this requires a measuring device such as a touch probe or touch sensor, parts for installing it, a slide storage mechanism, etc., which can lead to various problems such as an increase in the cost of the entire device and increased operational restrictions on each part of the processing device to avoid contact with the newly added parts. Furthermore, since the actual processing point (the reference position for starting dressing) is not directly measured, there is a limit to how much the accuracy of dressing can be improved.

[0009] Such problems are not limited to gear grinding machines, but also occur in various processing machines, such as honing machines, that perform dressing to shape tools using a dressing tool.

[0010] Up until now, no proposals have been made regarding measures to improve the accuracy of dressing in response to changes in the axial distance between the tool and the dressing tool due to the influence of heat.

[0011] The present invention has been made in consideration of the above points, and its object is to provide a processing device that can improve the accuracy of dressing to shape a tool for processing a workpiece. [Means for solving the problem]

[0012] The solution of the present invention for achieving the above object comprises a tool for machining a workpiece, a dressing tool that is capable of moving relatively close to and away from the tool and that dresses the tool by cutting into the tool by a predetermined amount from a dressing reference position, thereby shaping the tool, a sensor whose output level changes depending on the contact between the tool and the dressing tool, and a control unit that detects contact between the tool and the dressing tool based on the output of the sensor, wherein the control unit brings the tool and the dressing tool closer to each other in a stage prior to performing the dressing, detects contact between the tool and the dressing tool based on the output of the sensor, and performs a reference position determination process that determines the dressing reference position based on information on the detected contact position.

[0013] With this specification, prior to dressing the tool, a dressing reference position is determined based on information about the contact position between the tool and the dressing tool, and the tool is cut into by the dressing tool by a predetermined depth of cut from the dressing reference position to form the tool. In other words, even if the distance between the tool and the dressing tool (such as the center distance) changes due to the influence of heat, the tool is cut into by the predetermined depth of cut using the dressing reference position determined based on information about the contact position between the tool and the dressing tool. Therefore, the tool can be cut into by the dressing tool by the targeted depth of cut without being affected by the change in distance. As a result, the shape of the tool after dressing (e.g., the finished diameter) can be appropriately obtained, and high machining accuracy of the workpiece using the tool can be maintained. [Effects of the Invention]

[0014] In the present invention, prior to the dressing stage in which the tool is shaped by the dressing tool, contact between the tool and the dressing tool is detected based on the output of a sensor, and the dressing reference position is determined based on the information on the detected contact position. This makes it possible to appropriately obtain the shape of the tool after dressing (for example, the finished diameter), and maintain high machining accuracy of the workpiece with the tool. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a gear grinding device according to an embodiment. [Figure 2] 10A and 10B are diagrams showing the engagement state between a grinding wheel and a workpiece during grinding of the workpiece; [Figure 3] 10A and 10B are diagrams showing a state of engagement between the grinding wheel and the dressing tool during dressing of the grinding wheel. [Figure 4] FIG. 2 is a cross-sectional view including a rotation axis of a grindstone in the grindstone support unit. [Figure 5] FIG. 2 is a block diagram showing a control system for performing dressing. [Figure 6] FIG. 10 is a diagram showing an AE waveform signal when the grinding wheel and the dressing tool come into contact with each other. [Figure 7] 5A and 5B are diagrams showing an example of an ideal AE waveform signal and an actual AE waveform signal during dressing. [Figure 8] FIG. 10 is a flowchart showing a control procedure during dressing in the embodiment. [Figure 9] FIG. 10 is a flowchart showing a control procedure during dressing in a modified example. [Figure 10] FIG. 10 is a view equivalent to FIG. 5 in a third modified example. [Figure 11] FIG. 10 is a view corresponding to FIG. 8 in a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. In the present embodiment, the present invention will be described as being applied to a gear grinding machine that grinds gears, which are workpieces.

[0017] -Outline of gear grinding equipment- Fig. 1 is a perspective view showing the main parts of a gear grinding machine 10 according to this embodiment. For convenience of explanation, the front-rear direction, left-right direction, and up-down direction are defined in this embodiment as shown in Fig. 1. The specific configuration of the mechanism of the gear grinding machine 10 is disclosed in, for example, Patent Document 2, but the mechanism of the gear grinding machine 10 will be briefly described below.

[0018] The gear grinding machine 10 grinds a workpiece W, which is an object to be machined, while rotating it synchronously with a grinding wheel 20, which is a tool, and includes a base 1, a grinding wheel support unit 2, and a workpiece processing unit 3, which are arranged on the base 1. The grinding wheel support unit 2 rotatably supports the grinding wheel 20. In FIG. 1, the rotation axis direction of the grinding wheel 20 is the front-rear direction. A thread-like groove is formed on the outer peripheral surface of the grinding wheel 20.

[0019] The workpiece processing unit 3 includes a spindle 30 and a support column 31, and a tailstock 32 and a dressing device 33 are integrally supported on the support column 31 so that they can freely rotate. When grinding a workpiece W, the support column 31 is rotated to position the tailstock 32 on the spindle 30, and the workpiece W is supported so that it is sandwiched between the spindle 30 and the tailstock 32. The supported workpiece W can be rotated with its rotation axis directed up and down by rotating the spindle 30. As shown in FIG. 2, the gear grinding device 10 can grind the tooth surface of the workpiece W by driving the grinding wheel 20 and the workpiece W in mesh with each other in synchronization with each other.

[0020] The dressing device 33 is used when dressing the grinding wheel 20. Dressing is performed to restore the sharpness of the thread-shaped groove of the grinding wheel 20 after continuously machining a predetermined number of workpieces W, and is performed by rotating the grinding wheel 20 while bringing a dressing tool 331 held by the dressing device 33 into contact with the grinding wheel 20, as shown in Fig. 3 .

[0021] The grinding wheel support unit 2 can move left and right, and during grinding, the rotating grinding wheel 20 is brought into contact with the workpiece W, thereby grinding the workpiece (gear) W. During dressing, the rotating grinding wheel 20 is brought into contact with the dressing tool 331, thereby shaping (dressing) the grinding wheel 20.

[0022] Here, we will briefly explain dressing and the grinding process of the workpiece W after dressing. In dressing, the grinding wheel 20 and the dressing tool 331 are opposed to each other so that they can move toward and away from each other, and they are brought into contact with each other from a reference position for starting dressing (the rotating grinding wheel 20 is brought closer to the dressing tool 331 by a predetermined distance), so that the dressing tool 331 cuts into the grinding wheel 20 by a predetermined cutting depth, thereby shaping the grinding wheel 20. At this time, because the grinding wheel 20 has a threaded groove, the grinding wheel support unit 2 slides the grinding wheel 20 in the front-to-rear direction so that the engagement between the grinding wheel 20 and the dressing tool 331 is maintained. In other words, by sliding the grinding wheel 20 in the front-to-rear direction, the relative position of the dressing tool 331 with respect to the grinding wheel 20 is moved from one end to the other in the direction along the rotation axis of the grinding wheel 20, and the entire grinding wheel 20 is cut into. In actual dressing, the dressing tool 331 cuts into the grinding wheel 20 multiple times, thereby forming the finished diameter of the grinding wheel 20 to a target diameter. For example, if the cut-in amount per cut-in operation is set to 5 μm and this cut-in operation is repeated 10 times, the finished diameter of the grinding wheel 20 will be reduced by 0.1 mm. After dressing is completed, when grinding the workpiece W (machining a gear) with the grinding wheel 20, it is assumed that the outer diameter of the grinding wheel 20 has been reduced by twice the cut-in amount due to dressing. The position of the grinding wheel 20 is advanced toward the workpiece W by the cut-in amount relative to its position before dressing (the grinding wheel support unit 2 is moved to the right), and grinding of the workpiece W is started.

[0023] 4 is a cross-sectional view including the rotation axis of the grinding wheel 20 in the grinding wheel support unit 2. As shown in FIG. 4, the grinding wheel support unit 2 is provided with an auto-balancer 21 that automatically corrects the balance of the grinding wheel 20 while it is rotating. In this embodiment, the auto-balancer 21 includes an AE sensor 210 (see FIG. 5) for detecting contact of the grinding wheel 20. The AE sensor 210 detects sound (elastic waves) generated when the grinding wheel 20 comes into contact with the workpiece W or the dressing tool 331, converts the sound into an electric signal, and outputs the electric signal.

[0024] As mentioned above, as grinding of the workpiece W is repeated, the temperature of the machine body may change due to changes in room temperature, etc., which may cause the center distance between the grinding wheel 20 and the dressing tool 331 to change. In the prior art, if the center distance between the grinding wheel 20 and the dressing tool 331 changes in this way, the reference position for starting dressing (dressing reference position) at the start of dressing would change from the calculated reference position, and the amount of cut into the grinding wheel 20 by the dressing tool 331 would deviate from the target amount by that amount, which could cause the shape of the grinding wheel 20 after shaping (finished diameter of the grinding wheel) to deviate from the calculated value. As a result, there was a possibility that the OBD of the gear would not be properly obtained.

[0025] In view of this, the present embodiment aims to improve the accuracy of dressing.

[0026] 5 is a block diagram showing a control system for performing dressing. As shown in Fig. 5, the gear grinding machine 10 has a control unit 4, which includes a normal dress waveform storage unit 41, a contact determination unit 42, a dressing control unit 43, a reference position coordinate adjustment unit 44, a dress waveform determination unit 45, a reference position determination process retry unit 46, and an alarm output unit 47.

[0027] The normal dressing waveform storage unit 41 stores in advance the AE waveform signal (shown by the solid line in FIG. 7, hereinafter referred to as the ideal AE waveform signal; the ideal AE waveform signal shown in FIG. 7 is a schematic illustration) that should be output from the AE sensor 210 when the dressing tool 331 is cutting into the grinding wheel 20 at an appropriate depth of cut. In other words, this ideal AE waveform signal is stored as a signal that can be used to determine that the dressing tool 331 is cutting into the grinding wheel 20 at an appropriate depth of cut if the AE waveform signal output from the AE sensor 210 during actual dressing is close to this ideal AE waveform signal.

[0028] The contact determination unit 42 is a functional unit that detects contact between the grinding wheel 20 and the rotating dressing tool 331 based on the AE waveform signal output from the AE sensor 210 when the grinding wheel 20 and the rotating dressing tool 331 are brought relatively close together while their phases are aligned prior to the dressing process.

[0029] 6 is a diagram showing an AE waveform signal when the grinding wheel 20 and the dressing tool 331 come into contact. In FIG. 6, S1 is the AE waveform signal output by the AE sensor 210, and THc is a contact threshold for detecting contact by comparing it with the AE waveform signal S1. Basically, when there is no contact between the grinding wheel 20 and the dressing tool 331, the waveform level (output level) of the AE waveform signal S1 is below the contact threshold THc. When there is contact between the grinding wheel 20 and the dressing tool 331, the waveform level of the AE waveform signal S1 rises sharply and exceeds the contact threshold THc. When the waveform level of the AE waveform signal S1 exceeds the contact threshold THc, the contact determination unit 42 determines that there is contact between the grinding wheel 20 and the dressing tool 331 at that time, and stores the coordinate position of the grinding wheel 20 at that time (for example, the coordinate position of the grinding wheel support unit 2 moving to the right).

[0030] The contact determination operation here is performed with the phase of the dressing tool 331 adjusted so that it meshes appropriately (as shown in FIG. 3) with the thread groove of the grinding wheel 20. The phase of the grinding wheel 20 and the dressing tool 331 is set so that the dressing tool 331 meshes with the thread groove of the grinding wheel 20 at the center in the direction along the rotation axis of the grinding wheel 20. That is, in the contact determination operation, the presence or absence of contact between the grinding wheel 20 and the dressing tool 331 is determined at approximately the same phase position every time.

[0031] The dressing control unit 43 is a functional unit that controls the above-mentioned dressing operation. As is well known, the dressing operation is controlled by controlling the phase alignment between the grinding wheel 20 and the dressing tool 331, controlling the rotation of the grinding wheel 20, controlling the forward movement of the grinding wheel 20, and controlling the sliding of the grinding wheel 20 in the front-rear direction.

[0032] The reference position coordinate adjustment unit 44 compares the coordinate position of the grinding wheel 20 at the time of contact (the time of contact between the grinding wheel 20 and the dressing tool 331) determined by the contact determination unit 42 (hereinafter referred to as the current contact coordinate position) with the dressing reference position used in the previous dressing (hereinafter referred to as the previous dressing reference position), and determines the current dressing reference position based on the comparison result.

[0033] Specifically, when the deviation between the previous dressing reference position and the current contact coordinate position is less than a predetermined threshold (e.g., 5 μm) (referred to in the present invention as a case where the deviation between the dressing reference position during the previous dressing and the contact position acquired by the current reference position determination process is less than a predetermined threshold), the previous dressing reference position is determined as the dressing reference position during the next dressing (next dressing reference position). For example, when the change in the axis distance due to the influence of heat is relatively small, the previous dressing reference position is determined as the next dressing reference position. On the other hand, when the deviation between the previous dressing reference position and the current contact coordinate position is equal to or greater than a predetermined threshold (e.g., 5 μm) (referred to in the present invention as a case where the deviation between the dressing reference position during the previous dressing and the contact position acquired by the current reference position determination process is equal to or greater than a predetermined threshold), the current contact coordinate position is determined as the dressing reference position during the next dressing (next dressing reference position). For example, if the change in the axis distance due to the influence of heat is relatively large, the current contact coordinate position will be determined as the next dressing reference position. Hereinafter, the process of determining the dressing reference position in this manner will be referred to as the reference position determination process (referred to in this invention as the reference position determination process that detects contact between the tool and the dressing tool based on the output of a sensor and determines the dressing reference position based on information on this detected contact position).

[0034] The dressing waveform determination unit 45 is a functional unit that, when dressing is started, cutting the grinding wheel 20 by a predetermined depth of cut from the next-dressing reference position determined by the reference position determination process, compares the AE waveform signal output from the AE sensor 210 (hereinafter referred to as the actual AE waveform signal) with the ideal AE waveform signal stored in the normal dressing waveform storage unit 41 (the AE waveform signal that should be output from the AE sensor 210 when the dressing tool 331 is cutting the grinding wheel 20 by an appropriate depth of cut), and determines whether they are similar. If the actual AE waveform signal and the ideal AE waveform signal are similar, it is determined that dressing is being performed normally. Conditions for determining that the actual AE waveform signal and the ideal AE waveform signal are not similar include, for example, when the waveform level of the actual AE waveform signal continues to be below a predetermined value (including when the waveform level is zero) or when the waveform level of the actual AE waveform signal exceeds a predetermined upper threshold. The actual AE waveform signal indicated by the dashed line in FIG. 7 indicates a case where its waveform level exceeds a predetermined upper threshold.

[0035] The reference position determination process retry unit 46 is a functional unit that executes the reference position determination process again when the dress waveform determination unit 45 determines that the actual AE waveform signal and the ideal AE waveform signal are not similar to each other during the first cutting operation in dressing. That is, the above-mentioned processes in the contact determination unit 42 and the reference position coordinate adjustment unit 44 are executed again, and then dressing is performed.

[0036] The alarm output unit 47 is a functional unit that outputs an alarm without re-executing the reference position determination process if, when the reference position determination process retry unit 46 executes the reference position determination process again, it is determined that the actual AE waveform signal and the ideal AE waveform signal do not approximate each other, and the number of such determinations reaches a predetermined value. This alarm may be displayed on a monitor screen provided in the gear grinding machine 10, or may be an audio warning.

[0037] The process of re-executing the reference position determination process or outputting an alarm when it is determined that the actual AE waveform signal and the ideal AE waveform signal are not similar to each other corresponds to the abnormality process of this invention (the process of stopping the dressing and re-executing the reference position determination process, and the process of stopping the dressing and issuing an alarm).

[0038] -Dressing treatment- Next, the procedure for the dressing process in the gear grinding machine 10 configured as described above will be described with reference to the flowchart of FIG.

[0039] When the grinding process of the workpiece W by the grinding wheel 20 reaches a predetermined number of times and the dressing process is started, first, in step ST1, the phases of the grinding wheel 20 and the dressing tool 331 are aligned. That is, by sliding the grinding wheel 20 in the forward and backward directions, the phases of the grinding wheel 20 and the dressing tool 331 are aligned so that the dressing tool 331 meshes with the thread-like groove of the grinding wheel 20 at the center in the direction along the rotation axis of the grinding wheel 20.

[0040] Thereafter, in step ST2, the grindstone 20 is moved forward toward the dressing tool 331 (the grindstone support unit 2 is moved rightward) while the dressing tool 331 is being rotated.

[0041] In step ST3, it is determined whether the waveform level of the AE waveform signal S1 output from the AE sensor 210 exceeds the contact threshold value THc. As described above, when the grinding wheel 20 and the dressing tool 331 come into contact, the waveform level of the AE waveform signal S1 exceeds the contact threshold value THc, and therefore it is possible to determine at this point that the grinding wheel 20 and the dressing tool 331 have come into contact. If the waveform level of the AE waveform signal S1 exceeds the contact threshold value THc, and the determination is YES in step ST3, the process proceeds to step ST4, and the coordinate position of the grinding wheel 20 at this point (the coordinate position of the grinding wheel support unit 2 in the left-right direction: the current contact coordinate position) is stored.

[0042] In step ST5, the current contact coordinate position stored in step ST4 is compared with the previous dressing reference position, and it is determined whether or not the deviation therebetween is equal to or greater than a predetermined threshold value A (for example, 5 μm).

[0043] If the determination in step ST5 is YES, the process proceeds to step ST6, where the current contact coordinate position is determined as the next dressing reference position. That is, the dressing reference position is updated (updated to the next dressing reference position), and the process proceeds to step ST7. On the other hand, if the determination in step ST5 is NO, the process proceeds to step ST7 without updating the dressing reference position (the previous dressing reference position is determined as the next dressing reference position: the next dressing reference position is not updated).

[0044] In step ST7, dressing is started. That is, the rotating grinding wheel 20 is moved closer to the dressing tool 331 by a predetermined distance from the dressing reference position (next dressing reference position), so that the dressing tool 331 cuts into the grinding wheel 20 by a predetermined cutting depth (for example, 5 μm), thereby shaping the grinding wheel 20.

[0045] In step ST8, during the first cutting operation in the dressing, it is determined whether the actual AE waveform signal obtained from the output of the AE sensor 210 is similar to the ideal AE waveform signal stored in the normal dress waveform storage unit 41.

[0046] If the actual AE waveform signal and the ideal AE waveform signal are close to each other (for example, the waveform level of the actual AE waveform signal remains at or below a predetermined value, or the waveform level of the actual AE waveform signal does not exceed a predetermined upper threshold), and the determination in step ST8 is YES, the process proceeds to step ST9, where dressing continues, and the cutting operation of the grinding wheel 20 by the dressing tool 331 is repeated a predetermined number of times, after which the dressing is terminated and the process moves on to grinding the next workpiece W. In other words, the position of the grinding wheel 20 is advanced toward the workpiece W by the dimension cut in by dressing relative to the position before dressing (the grinding wheel support unit 2 is moved to the right), and grinding of the workpiece W is started.

[0047] On the other hand, if the actual AE waveform signal and the ideal AE waveform signal are not similar (for example, the waveform level of the actual AE waveform signal continues to be below a predetermined value, or the waveform level of the actual AE waveform signal exceeds a predetermined upper threshold), and the result is NO in step ST8, the process proceeds to step ST10, and the retry counter is incremented by 1.

[0048] In step ST11, it is determined whether the count value of the retry counter has reached a predetermined value B (for example, 2). If the count value of the retry counter has not reached the predetermined value and the determination is NO, the process returns to step ST1 and the reference position determination process is performed again.

[0049] On the other hand, if the count value of the retry counter reaches the predetermined value B and the determination in step ST11 is YES, the process proceeds to step ST12, where the gear grinding machine 10 is stopped and an alarm is output by the alarm output unit 47. That is, an alarm is displayed on a monitor screen provided in the gear grinding machine 10, an audio warning is issued, or the like, to prompt the operator to perform maintenance to properly perform the reference position determination process.

[0050] -Effects of the embodiment- As described above, in this embodiment, even if the center distance between the grinding wheel 20 and the dressing tool 331 changes due to the influence of heat, the grinding wheel 20 is cut by a predetermined depth of cut using a position determined based on information about the contact position between the grinding wheel 20 and the dressing tool 331 as the dressing reference position. Therefore, the dressing tool 331 can cut the grinding wheel 20 by the targeted depth of cut without being affected by the change in center distance. As a result, the finished diameter of the grinding wheel 20 after dressing can be appropriately obtained, and the machining accuracy of the workpiece W by the grinding wheel 20 can be maintained at a high level. In other words, even in an environment other than a constant-temperature room, the finished diameter of the grinding wheel 20 after dressing can be appropriately obtained, and the machining accuracy of the workpiece W by the grinding wheel 20 can be maintained at a high level. Furthermore, since there is no need to measure the center distance using the touch probe or touch sensor described above, problems that would occur if a touch probe or touch sensor were provided (such as increased costs and increased operational limitations on each part of the machining device) can be avoided. Furthermore, since the cutting depth of the grinding wheel 20 can be adjusted appropriately, the grinding wheel 20 is not damaged due to excessive contact with the dressing tool 331.

[0051] Furthermore, in this embodiment, in the reference position determination process, the grinding wheel 20 and the dressing tool 331 are brought into contact with each other by phasing them together so that the dressing tool 331 meshes with the threaded groove of the grinding wheel 20 at the center in the direction along the rotation axis of the grinding wheel 20. In other words, the presence or absence of contact between the grinding wheel 20 and the dressing tool 331 is determined at approximately the same phase position each time. This makes it possible to obtain with high accuracy the coordinate position of the grinding wheel 20 when the grinding wheel 20 comes into contact with the dressing tool 331.

[0052] -Variation 1- Next, Modification 1 will be described. In the above-described embodiment, the reference position determination process is performed in a stage prior to each dressing. In this modification, instead, the reference position determination process is performed as needed.

[0053] Specifically, the reference position determination process is performed on the condition that the change in environmental temperature between the previous dressing and the next dressing is equal to or greater than a predetermined value. More specifically, changes in temperature in the room where the gear grinding machine 10 is installed, changes in cutting oil temperature, etc. are sensed, and the reference position determination process is performed on the condition that the temperature change is equal to or greater than a predetermined value.

[0054] Alternatively, the reference position determination process may be performed based on an index correlated with changes in environmental temperature. For example, if the gear grinding machine 10 has been stopped for a predetermined time or longer, the reference position determination process may be performed in a previous stage for a predetermined number of dressings since the gear grinding machine 10 was started. This takes into account the possibility that if the gear grinding machine 10 has been stopped for a predetermined time or longer, the temperature of the gear grinding machine 10 may change significantly after the gear grinding machine 10 is started, which may result in a large change in the center distance between the grinding wheel 20 and the dressing tool 331. The index correlated with changes in environmental temperature may also be time. For example, the temperature rises more rapidly per unit time in the morning than during the day, and the temperature drops more rapidly in the evening than during the day. Therefore, the reference position determination process may be performed only during these time periods.

[0055] -Variation 2- Next, a second modification will be described. In the embodiment described above, if the actual AE waveform signal and the ideal AE waveform signal do not approximate each other, the reference position determination process is repeated until the count value of the retry counter reaches a predetermined value B. However, the present invention is not limited to this. If the actual AE waveform signal and the ideal AE waveform signal do not approximate each other, the gear grinding machine 10 may be immediately stopped (without repeating the reference position determination process) and an alarm may be output by the alarm output unit 47. FIG. 9 is a flowchart showing the procedure for the dressing process in this case. In this flowchart, the same step numbers are used for steps that are the same as those in the flowchart of FIG. 8 described in the embodiment described above. As shown in FIG. 9, if the actual AE waveform signal and the ideal AE waveform signal do not approximate each other and the determination in step ST8 is NO, the process proceeds to step ST12, where the gear grinding machine 10 is stopped and an alarm is output by the alarm output unit 47. That is, an alarm may be displayed on a monitor screen provided in the gear grinding machine 10, an audio warning may be issued, or the like, to prompt the operator to perform maintenance to properly perform the reference position determination process.

[0056] -Variation 3- Next, Modification 3 will be described. In the above-described embodiment, if the deviation between the coordinate position (current contact coordinate position) of the grinding wheel 20 at the time of contact (the time of contact between the grinding wheel 20 and the dressing tool 331) determined by the contact determination unit 42 and the dressing reference position used in the previous dressing (previous dressing reference position) is equal to or greater than a predetermined threshold A (e.g., 5 μm), the current contact coordinate position is determined to be the next dressing reference position. In other words, the dressing reference position is updated and dressing is started. In this modification, instead of this, even if the deviation between the current contact coordinate position and the previous dressing reference position is equal to or greater than the predetermined threshold A, if the deviation is extremely large, it is determined that some kind of malfunction (such as a false detection due to a malfunction of the AE sensor 210 or a malfunction in the operating procedure) may have occurred, and the gear grinding machine 10 is stopped or an alarm is output. Furthermore, in this modification, whether dressing is being performed normally is not determined by determining whether the actual AE waveform signal and the ideal AE waveform signal are similar to each other. However, without being limited to this, in a case where the gear grinding device 10 is stopped or an alarm is output when the deviation between the current contact coordinate position and the previous dressing reference position is extremely large, when dressing is being performed, it may be determined whether the actual AE waveform signal and the ideal AE waveform signal are close to each other to determine whether dressing is being performed normally.

[0057] Fig. 10 is a block diagram showing a control system according to this modification. In Fig. 10, the same functional units as those in the block diagram of Fig. 5 according to the previously described embodiment are denoted by the same reference numerals. As shown in Fig. 10, in the control system according to this modification, the contact determination unit 42 functions to output alarm information to the alarm output unit 47 if contact between the grinding wheel 20 and the dressing tool 331 is detected based on the AE waveform signal output from the AE sensor 210 and the deviation between the previous dressing reference position and the current contact coordinate position exceeds a predetermined threshold value (e.g., 100 µm). The alarm output unit 47 then outputs the alarm information, as in the previously described embodiment, and displays an alarm on a monitor screen provided in the gear grinding machine 10, issues an audio warning, or the like.

[0058] Fig. 11 is a flowchart showing the procedure of the dressing process in this modified example. In this flowchart, the same steps as those in the flowchart of Fig. 8 in the above-described embodiment are assigned the same step numbers. As shown in Fig. 11, if the determination in step ST5 is YES, the process proceeds to step ST13, where the current contact coordinate position and the previous dressing reference position are compared, and it is determined whether the deviation therebetween is equal to or less than a predetermined threshold C (for example, 100 µm).

[0059] If the determination in step ST13 is YES, the process proceeds to step ST6, where the current contact coordinate position is determined as the next dressing reference position. On the other hand, if the determination in step ST13 is NO (the deviation between the current contact coordinate position and the previous dressing reference position is extremely large), the process proceeds to step ST12, where the gear grinding machine 10 is stopped and an alarm is output by the alarm output unit 47. Thereafter, the process returns to step ST1, and the reference position determination process is performed again.

[0060] In addition, if the deviation between the current contact coordinate position and the previous dressing reference position is less than a predetermined threshold A and a NO judgment is made in step ST5, and dressing is started in step ST7, or if the deviation between the current contact coordinate position and the previous dressing reference position is less than a predetermined threshold C and a YES judgment is made in step ST13, and dressing is started in step ST7 after the current contact coordinate position has been determined as the next dressing reference position in step ST6, dressing continues without performing the processing of step ST8 described above (a process of determining whether the actual AE waveform signal and the ideal AE waveform signal are close to each other), and the cutting operation of the grinding wheel 20 by the dressing tool 331 (cutting operation by a predetermined cutting amount) is repeated a predetermined number of times, and then dressing is terminated in step ST9 and processing moves on to grinding of the next workpiece W.

[0061] In these modified examples, as in the case of the above-described embodiment, the dressing tool 331 can cut into the grinding wheel 20 by the targeted cutting depth without being affected by changes in the center distance. As a result, the finished diameter of the grinding wheel 20 after dressing can be appropriately obtained, and the machining accuracy of the workpiece W by the grinding wheel 20 can be maintained at a high level. In particular, in modified example 3, if there is a possibility that some kind of malfunction has occurred, such as a false detection due to a malfunction of the AE sensor 210 or a malfunction in the operating procedure, it is possible to carry out a processing operation to address the problem.

[0062] -Other embodiments- The present invention is not limited to the above-described embodiment and each of the modifications, and all modifications and applications encompassed within the scope of the claims and equivalents thereto are possible.

[0063] For example, in the above embodiment and each of the above modifications, the present invention has been described as being applied to the gear grinding machine 10. However, the present invention is not limited to this, and can also be applied to various processing machines, such as a honing machine, that perform dressing to shape a tool using a dressing tool. [Industrial Applicability]

[0064] The present invention is applicable to a processing device that performs dressing by using a dressing tool to shape a grinding wheel for grinding a gear. [Explanation of symbols]

[0065] 10 Gear grinding equipment (processing equipment) 20 Grindstone (Tool) 210 AE sensor (sensor) 331 Dress Tool 4. Control Unit 41 Normal dress waveform memory section (memory section) double work

Claims

1. A tool for processing the workpiece; a dressing tool that is capable of being moved toward or away from the tool relatively and that dresses the tool by cutting into the tool by a predetermined cutting depth from a dressing reference position to form the tool; a sensor whose output level changes in response to contact between the tool and the dressing tool; a control unit that detects contact between the tool and the dressing tool based on an output of the sensor, The control unit, in a stage prior to performing the dressing, brings the tool and the dressing tool relatively close to each other, detects contact between the tool and the dressing tool based on the output of the sensor, and performs a reference position determination process to determine the dressing reference position based on information on the detected contact position.

2. 2. The processing device according to claim 1, The control unit If the deviation between the dressing reference position during the previous dressing and the contact position acquired by the current reference position determination process is less than a predetermined threshold, the dressing reference position during the previous dressing is determined as the dressing reference position during the next dressing, A processing apparatus characterized in that, when the deviation between the dressing reference position during the previous dressing and the contact position acquired by the current reference position determination process is equal to or greater than a predetermined threshold, the contact position acquired by the reference position determination process is determined to be the dressing reference position during the next dressing.

3. 3. The processing apparatus according to claim 1, The dressing is performed every time the workpiece is machined by the tool a predetermined number of times, The processing apparatus is characterized in that the control unit performs the reference position determination process in a preparatory stage each time the dressing is performed.

4. 3. The processing apparatus according to claim 1, The dressing is performed every time the workpiece is machined by the tool a predetermined number of times, The processing apparatus is characterized in that the control unit switches between performing and not performing the reference position determination process depending on the environmental temperature change or an index correlated with the environmental temperature change during the period between the previous dressing and the next dressing.

5. 3. The processing apparatus according to claim 1, a storage unit configured to store output information of the sensor during the dressing process on the assumption that the tool is formed with a predetermined depth of cut, The processing apparatus is characterized in that it compares the output information of the sensor acquired during the dressing with the stored output information of the sensor, and performs abnormality processing if the deviation between these pieces of output information is equal to or greater than a predetermined amount.

6. 6. The processing apparatus according to claim 5, The processing apparatus is characterized in that the abnormality processing is processing for stopping the dressing and performing the reference position determination processing again.

7. 6. The processing apparatus according to claim 5, The processing apparatus is characterized in that the abnormality processing is processing to stop the dressing and issue an alarm.

8. 3. The processing apparatus according to claim 1, the workpiece is a gear, The processing device is characterized in that the tool is a grinding wheel that rotates when grinding the tooth surface of the gear.

9. 9. The processing apparatus according to claim 8, The processing device is characterized in that, in the reference position determination process, the dressing tool is brought into contact with a central portion of the grinding wheel in a direction along the rotation axis of the grinding wheel, thereby obtaining information about the contact position.

10. 3. The processing apparatus according to claim 1, The processing device is characterized in that the sensor is an AE sensor.

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