Processing device

Abstract

To provide a processing device that can prevent contact error detection even when there is a change in an output level of a sensor for detecting contact between a tool and a tool contact object.SOLUTION: A gear grinding device 10 includes: a grindstone support unit 2 for supporting a grindstone 20; a workpiece processing unit 3 for supporting a tool contact object (workpiece or dress tool) contactable with and separable from the grindstone 20; an AE sensor 210 whose output level is changed due to contact between the grindstone 20 and the tool contact object; and a control section 4 for performing contact detection of the grindstone 20 and the tool contact object based on an output of the AE sensor 210. The control section 4 performs contact detection by comparing an output level of the AE sensor 210 with a contact threshold value, and changes a contact threshold value by comparing an output level of the AE sensor 210 when the grindstone 20 and the tool contact object are in a non-contact state with a plurality of determination threshold values.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a processing apparatus that performs NC (numerical control) processing. [Background technology]

[0002] NC machining is generally performed in processing equipment that processes machine parts, etc. In NC machining, a processing tool (hereinafter, tool) or an object that comes into contact with the tool (workpiece or dressing tool) is moved by a servo motor built into the processing equipment.

[0003] In NC machining, detection processing using a sensor is essential for its control. For example, Patent Document 1 discloses that an AE (Acoustic Emission) sensor is used to detect contact between a tool and a dressing tool. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-263440 A [Patent Document 2] JP 2020-199620 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is important to prevent false detection in contact detection by a sensor. For example, in contact detection in an AE sensor, the output waveform of the AE sensor is compared with a predetermined threshold, and contact is detected when the waveform level exceeds the threshold. However, when the AE sensor is used for a long time, the waveform level is expected to change when there is no contact due to aging of the sensor or the device mechanism, or changes in the surrounding environment. If the amount of change in the waveform level of the AE sensor becomes large, the possibility of false detection of contact (contact reaction without contact, non-contact reaction with contact) increases. If a false detection of contact occurs by the AE sensor, a phase shift occurs between the tool and the workpiece (or the dressing tool), making it impossible to perform high-precision machining. In addition, if the phase shift becomes too large, there is a risk of damage to the tool, device mechanism, etc.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a processing device that can prevent erroneous detection of contact even when there is a change in the output level of a sensor that detects contact between a tool and a tool contact object. [Means for solving the problem]

[0007] In order to solve the above problems, the processing apparatus of the present disclosure includes a tool support unit that supports a tool, a tool contact object support unit that supports a tool contact object that can be attached to and detached from the tool, a sensor whose output level changes upon contact between the tool and the tool contact object, and a control unit that detects contact between the tool and the tool contact object based on the output of the sensor, and the control unit detects contact by comparing the output level of the sensor with a contact threshold value, and changes the contact threshold value by comparing the output level of the sensor when the tool and the tool contact object are not in contact with a plurality of judgment threshold values.

[0008] According to the above configuration, the output level of the sensor when the tool and the tool contact object are not in contact with each other is compared with a plurality of judgment thresholds, and the contact threshold is changed according to the result, so that the contact threshold can be automatically set appropriately even if the output level of the sensor changes due to aging, etc. This makes it possible to prevent erroneous contact detection. Effect of the Invention

[0009] The machining apparatus of the present disclosure has the advantage of being able to automatically set the contact threshold value used for detecting contact between a tool and an object contacting the tool, thereby preventing erroneous detection of contact. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a gear grinding device as one embodiment of a processing device according to the present disclosure. [Diagram 2] 1 is a diagram showing a state in which a grinding wheel and a workpiece are engaged with each other during grinding of the workpiece; FIG. [Diagram 3] 11 is a diagram showing a meshing state between the grindstone and the dressing tool during dressing of the grindstone. FIG. [Figure 4] 4 is a cross-sectional view including a rotation axis of a grindstone in the grindstone support unit. FIG. [Diagram 5] FIG. 1 is a block diagram showing a control system for detecting contact using an AE sensor and resetting a contact threshold value. [Figure 6] 11 is a waveform diagram showing contact detection by an AE sensor. [Figure 7] FIG. 13 is a diagram showing an example of a screen that displays an output signal of an AE sensor when a contact is detected. [Figure 8] 13A and 13B are diagrams illustrating an example of switching of a screen that displays an output signal of an AE sensor when a contact is detected. [Figure 9] 13A and 13B are diagrams illustrating an example of switching of a screen that displays an output signal of an AE sensor when a contact is detected. [Figure 10] 13A and 13B are diagrams illustrating an example of switching of a screen that displays an output signal of an AE sensor when a contact is detected. [Figure 11]13A and 13B are diagrams illustrating an example of switching of a screen that displays an output signal of an AE sensor when a contact is detected. [Figure 12] 13 is a table showing switching conditions of the determination threshold value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the embodiment, a processing device according to the present disclosure is applied to a gear grinding device that performs grinding on a gear that is a workpiece (a piece of work).

[0012] Fig. 1 is a perspective view showing the main parts of a gear grinding device 10 according to this embodiment. For convenience of explanation, in this embodiment, the front-rear direction, left-right direction, and up-down direction are defined as shown in Fig. 1. Note that the specific configuration of the mechanism of the gear grinding device 10 is disclosed in, for example, Patent Document 2, but the mechanism of the gear grinding device 10 will be briefly described below.

[0013] The gear grinding device 10 grinds a workpiece W while rotating it synchronously with a grinding wheel 20, which is a tool, and includes a base 1, a grinding wheel support unit (tool support unit) 2 and a workpiece processing unit (tool contact object support 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 screw-shaped groove is formed on the outer circumferential surface of the grinding wheel 20.

[0014] 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 by the support column 31 so as to be freely rotatable. When grinding the workpiece W, the tailstock 32 is positioned above the spindle 30 by rotating the support column 31, and the workpiece W is supported so as to be sandwiched between the spindle 30 and the tailstock 32. The supported workpiece W can be rotated with the vertical direction as the rotation axis direction 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 meshing the grinding wheel 20 with the workpiece W and driving them synchronously.

[0015] The dressing device 33 is used when dressing the grinding wheel 20. The 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.

[0016] The grindstone support unit 2 can move in the left-right direction, and this movement allows the grindstone 20 to be attached to and detached from the workpiece W during grinding. Also, during dressing, the grindstone 20 can be attached to and detached from the dressing tool 331. Before grinding, contact detection between the grindstone 20 and the workpiece W as the grindstone 20 moves (detection of the state shown in FIG. 2) is required, and before dressing, contact detection between the grindstone 20 and the dressing tool 331 (detection of the state shown in FIG. 3) is required. That is, in this embodiment, the workpiece W or the dressing tool 331 is the tool contact object to be detected for contact detection.

[0017] Fig. 4 is a cross-sectional view including the rotation axis of the grindstone 20 in the grindstone support unit 2. As shown in Fig. 4, the grindstone support unit 2 is provided with an auto-balancer 21 that automatically corrects the balance of the grindstone 20 during rotation. In this embodiment, the auto-balancer 21 includes an AE sensor 210 (see Fig. 5) for detecting contact of the grindstone 20. The AE sensor 210 detects sound (elastic waves) generated when the grindstone 20 comes into contact with the workpiece W or the dressing tool 331, converts the sound into an electric signal, and outputs the signal.

[0018] Fig. 5 is a block diagram showing a control system for detecting contact using the AE sensor 210 and resetting the contact threshold value THc described later. As shown in Fig. 5, the gear grinding machine 10 has a control unit 4, which has a judgment unit 40, a threshold value setting unit 41, and a threshold value changing unit 42. The judgment unit 40 compares the output signal of the AE sensor 210 (AE waveform signal S1 described later) with a threshold value. The threshold value setting unit 41 stores the set threshold value. The threshold value changing unit 42 receives the threshold value judgment result by the judgment unit 40 and switches the threshold value set in the threshold value setting unit 41.

[0019] Fig. 6 is a diagram showing an example of a screen displaying an output signal of the AE sensor 210 when contact is detected. In Fig. 6, S1 is a waveform signal (AE waveform signal) output by the AE sensor 210, and THc is a contact threshold for detecting contact by comparing with the AE waveform signal S1. Basically, when there is no contact of the grindstone 20 (contact with the tool contact object), the waveform level of the AE waveform signal S1 is below the contact threshold THc, and when there is contact of the grindstone 20, the waveform level of the AE waveform signal S1 rises sharply and exceeds the contact threshold THc. When the AE waveform signal S1 exceeds the contact threshold THc, the control unit 4 detects contact between the grindstone 20 and the tool contact object.

[0020] Incidentally, the contact detection here is performed when the phase of the grinding wheel 20 and the tool contact object is matched before grinding or dressing is performed. In the gear grinding device 10, the phase is matched so that the workpiece W or the dressing tool 331 is properly meshed with the threaded groove of the grinding wheel 20 (as shown in FIG. 2 or FIG. 3) during grinding or dressing. This phase matching is performed while repeatedly bringing the grinding wheel 20 into contact with the tool contact object multiple times, and contact detection is performed at that time. Therefore, at the contact detection stage, when contact between the grinding wheel 20 and the tool contact object is detected, control is performed to move the grinding wheel 20 away from the tool contact object. As a result, the grinding wheel 20 becomes non-contact again, and the waveform level of the AE waveform signal S1 also drops to the non-contact state level.

[0021] In order to perform such contact detection accurately, it is necessary to set the contact threshold value THc appropriately for the AE waveform signal S1. However, in the AE waveform signal S1, the waveform level during non-contact may change due to aging of the AE sensor 210, changes in the surrounding environment, and the like. For example, if a change occurs such that the waveform level during non-contact decreases, the AE waveform signal S1 does not exceed the contact threshold value THc when the grinding wheel 20 is in contact, and there is a risk of false detection such as a non-contact reaction during contact. Conversely, if a change occurs such that the waveform level during non-contact increases, the AE waveform signal S1 exceeds the contact threshold value THc even when the grinding wheel 20 is not in contact, and there is a risk of false detection such as a contact reaction during non-contact.

[0022] Such erroneous detection can be prevented by resetting the contact threshold value in response to a change in the waveform level of the AE waveform signal S1. The gear grinding device 10 of the present disclosure can automatically reset the contact threshold value THc. A method for resetting the contact threshold value THc in the gear grinding device 10 will be described below.

[0023] In this embodiment, at the time when contact detection of the grindstone 20 is started, four judgment thresholds TH1 to TH4 (collectively referred to as judgment thresholds TH) are set in ascending order of level as shown in the left diagrams of Fig. 7 to Fig. 11. Of these, the judgment threshold TH3 corresponds to the above-mentioned contact threshold THc.

[0024] The left diagrams of Figures 7 to 11 are waveform diagrams in which the AE waveform signal S1 is measured for a predetermined period immediately after the start of contact detection. During this predetermined period, the grinding wheel 20 is moved in a direction approaching the tool contact object, but a non-contact state is maintained during the predetermined period. In other words, the AE waveform signal S1 in the left diagrams of Figures 7 to 11 is a waveform (non-contact waveform) in a state in which there is no contact between the grinding wheel 20 and the tool contact object.

[0025] The non-contact waveform of the AE waveform signal S1 is compared with a judgment threshold TH, and the judgment threshold TH is switched depending on the comparison result. That is, when the level of the non-contact waveform is low, the judgment threshold TH is switched to a low level, and when the level of the non-contact waveform is high, the judgment threshold TH is switched to a high level. Note that this switching of the judgment threshold TH always includes switching of the judgment threshold TH3 (i.e., the contact threshold THc).

[0026] Fig. 12 is a table showing the switching conditions of the determination threshold TH. In the table of Fig. 12, the numerical values ​​of the determination thresholds TH1 to TH4 are shown as a level ratio relative to the maximum level numerical value of the AE waveform signal S1, which is 100%, and the minimum level numerical value, which is 0%.

[0027] Taking contact detection during phase alignment between the grindstone 20 and the workpiece W as an example, the judgment threshold TH at the start of detection is set to the "workpiece reference load" in Fig. 12. That is, the numerical values ​​of the judgment thresholds TH1 to TH4 are set to 3%, 20%, 40%, and 60%, respectively. This setting state corresponds to the left diagrams of Figs. 7 to 11.

[0028] When the non-contact waveform of the AE waveform signal S1 is between the judgment thresholds TH1 and TH2, it is judged that the level of the non-contact waveform is low, and the judgment threshold TH is switched to the "work threshold (low)" in FIG. 12. That is, the numerical values ​​of the judgment thresholds TH1 to TH4 are switched to 0%, 35%, 40%, and 99%, respectively. This switching corresponds to the switching from the left diagram to the right diagram in FIG. 7. The judgment result at this time is output from the judgment unit 40 to the threshold change unit 42 as the threshold judgment result. Furthermore, the threshold change unit 42 changes the judgment threshold TH set in the threshold setting unit 41 in response to this threshold judgment result.

[0029] When the non-contact waveform of the AE waveform signal S1 is between the judgment thresholds TH2 and TH3, the level of the non-contact waveform is judged to be in an intermediate state, and the judgment threshold TH is switched to the "work threshold (medium)" in Fig. 12. That is, the numerical values ​​of the judgment thresholds TH1 to TH4 are switched to 0%, 50%, 55%, and 99%, respectively. This switching corresponds to the switching from the left diagram to the right diagram in Fig. 8.

[0030] When the non-contact waveform of the AE waveform signal S1 is between the judgment thresholds TH3 and TH4, the level of the non-contact waveform is judged to be high, and the judgment threshold TH is switched to the "work threshold (high)" in Fig. 12. That is, the numerical values ​​of the judgment thresholds TH1 to TH4 are switched to 0%, 70%, 75%, and 99%, respectively. This switching corresponds to the switching from the left diagram to the right diagram in Fig. 9.

[0031] Contact detection during phase alignment between the grinding wheel 20 and the dressing tool 331 is basically performed in the same manner as contact detection during grinding phase alignment. However, the numerical value of the judgment threshold TH may be the same or different between the contact detection during dress phase alignment and the contact detection during grinding phase alignment. In the example of FIG. 12, the numerical value of the judgment threshold TH3 is different in a comparison between "workpiece threshold (low)" to "workpiece threshold (high)" and "dressing threshold (low)" to "dressing threshold (high)". This is because the tool contact object with respect to the grinding wheel 20 is different between the contact detection during dress phase alignment and the contact detection during grinding phase alignment, and therefore there is a possibility that the increase in the AE waveform signal S1 during contact may differ. In other words, the value of the judgment threshold TH3 after switching the judgment threshold TH is preferably set according to the increase in the AE waveform signal S1 during contact.

[0032] When the judgment threshold TH is switched, contact detection is subsequently performed. In the right diagrams of Figs. 7 to 9, the AE waveform signal S1, whose waveform level has risen sharply due to contact with the grindstone 20, exceeds the judgment threshold TH3 (contact threshold THc) after the switch. In other words, appropriate contact judgment of the grindstone 20 is realized based on the judgment threshold TH3 after the switch. The judgment result at this time is output from the judgment unit 40 as a contact judgment result.

[0033] In this manner, in contact detection in the gear grinding device 10 of the present disclosure, the level of the non-contact waveform is determined by comparing the non-contact waveform of the AE waveform signal S1 with multiple judgment thresholds TH, and erroneous detection of contact can be prevented by appropriately setting the contact threshold THc in accordance with the level of the non-contact waveform.

[0034] The non-contact waveform of the AE waveform signal S1 may exceed the judgment threshold TH4 (left diagram in FIG. 10) or may fall below the judgment threshold TH1 (left diagram in FIG. 11). In these cases, there is a possibility of an abnormality other than a false contact detection (e.g., a broken wire or a malfunction of the AE sensor 210), and the contact detection process is terminated. In this case, when the contact detection process is terminated, control is performed to move the grinding wheel 20 away from the tool contact object.

[0035] Moreover, after the switching of the judgment threshold TH, contact detection is performed by comparing the AE waveform signal S1 with the judgment threshold TH3, so that only the judgment threshold TH3 may be changed by switching the judgment threshold TH. However, in the example of FIG. 12, not only the judgment threshold TH3 but also the judgment threshold TH2 are changed. This is to end the contact detection process by determining that incomplete contact has occurred when a state occurs during contact detection in which the waveform level of the AE waveform signal S1 exceeds the judgment threshold TH2 but does not exceed the judgment threshold TH3 for a predetermined period of time (for example, about 2 seconds). For example, when the dressing tool is deteriorated during dress phase adjustment, even if contact occurs between the grinding wheel 20 and the dressing tool, the AE waveform signal S1 may not rise sharply as shown in FIG. 6, and the waveform level of the AE waveform signal S1 may exceed the judgment threshold TH2 but not exceed the judgment threshold TH3.

[0036] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be determined based on the claims.

[0037] For example, in the above embodiment, a gear grinding machine is exemplified as the machining apparatus of the present disclosure, but the present invention is not particularly limited to the type of machining performed by the machining apparatus or the shape of the workpiece. That is, in an NC machine tool, in order to determine a reference position during machining of a workpiece, it is necessary to detect the contact start point between a tool and an object contacting the tool, and the present invention can be applied to the contact detection for this purpose. In addition, the type of sensor used for contact detection is not particularly limited, and a sensor other than an AE sensor may be used (as long as an appropriate sensor is selected depending on the type of machining).

[0038] In the above embodiment, the contact and separation between the tool and the tool contact object is caused by the movement of the tool, but the contact and separation between the tool and the tool contact object may be caused by the movement of the tool contact object, i.e., the contact and separation between the tool and the tool contact object may be caused by the relative movement of the tool with respect to the tool contact object. [Explanation of symbols]

[0039] 10 Gear grinding equipment (processing equipment) 1 Base 2 Grindstone support unit (tool support unit) 20 Grindstone (Tools) 21 Auto balancer 210 AE sensor 3 Workpiece handling unit (tool contact object support unit) 30 main axis 31 Support column 32 Tailstock 33 Dressing device 331 Dressing tools (tool contact objects) 4. Control Unit 40 Judgment section 41 Threshold setting unit 42 Threshold change unit W Workpiece (Tool contact object) S1 AE waveform signal THc Contact Threshold TH1~TH4 Judgment threshold

Claims

1. A tool support unit for supporting a tool; a tool contact object support unit for supporting a tool contact object capable of being brought into contact with and separated from the tool; a sensor whose output level changes upon contact between the tool and the tool contact object; a control unit that detects contact between the tool and the tool contact object based on an output of the sensor, The control unit detects contact by comparing the output level of the sensor with a contact threshold, and changes the contact threshold by comparing the output level of the sensor when the tool and the tool contacting object are not in contact with each other with multiple judgment thresholds.

2. The processing apparatus according to claim 1, A processing device characterized in that the tool contact object is a workpiece to be processed by the tool.

3. The processing apparatus according to claim 2, the workpiece is a gear, The processing device, characterized in that the tool is a grinding wheel for grinding the tooth surface of the gear.

4. The processing apparatus according to claim 1, The tool is a grinding wheel for performing a grinding process, The processing device, characterized in that the tool contact object is a dressing tool that performs dressing processing on the grinding wheel.

5. The processing apparatus according to claim 1, The tool is a grinding wheel for performing a grinding process, The processing device, wherein the sensor is an AE sensor.

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