Machine tool and control method for a machine tool

Abstract

A machine tool and a control method of a machine tool. A machine tool (100) is provided with: a spindle (13) that rotates a grinding wheel that grinds a workpiece (W); a control device (500) that controls a rotational speed of the spindle; and a sensor that outputs a first signal to the control device when a diameter of the grinding wheel is below a threshold value decided in advance, and outputs a second signal to the control device when the diameter of the grinding wheel is greater than the threshold value. The control device sets an upper limit value of the rotational speed to a first upper limit value in a case where the first signal is received from the sensor, and controls the rotational speed so as not to exceed the first upper limit value. The control device sets the upper limit value of the rotational speed to a second upper limit value that is slower than the first upper limit value in a case where the second signal is received from the sensor, and controls the rotational speed so as not to exceed the second upper limit value. The greater the diameter of the grinding wheel, the slower the allowable rotational speed of the grinding wheel. The first upper limit value is a value below the allowable rotational speed when the diameter of the grinding wheel is the threshold value.

Description

Technical Field

[0001] This disclosure relates to machine tools and methods for controlling machine tools. Background Technology

[0002] Conventionally, as shown in Japanese Patent No. 7635356, grinding wheels are used in machine tools for grinding workpieces. Specifically, the grinding wheel is mounted on the tool spindle and rotates with the rotation of the tool spindle. By bringing the grinding wheel into contact with the workpiece while it is rotating, the workpiece is ground. Summary of the Invention

[0003] Currently, machine tool users need to manually input the grinding wheel's rotational speed to be below the maximum circumferential speed of the grinding wheel, which is predetermined based on the wheel's size or model. However, the aforementioned grinding wheel rotational speed is the maximum permissible circumferential speed of the grinding wheel specified by the grinding wheel manufacturer (hereinafter referred to as "maximum operating circumferential speed"), and is not necessarily within the maximum permissible speed determined by the machine manufacturer (hereinafter referred to as "permissible rotational speed").

[0004] This disclosure provides a machine tool and a method for controlling the machine tool to automatically control the rotational speed of the grinding wheel to below the permissible rotational speed.

[0005] According to a technical solution of this disclosure, a machine tool includes: a spindle that rotates a grinding wheel for grinding a workpiece; a control device that controls the rotational speed of the spindle; and a sensor that outputs a first signal to the control device when the diameter of the grinding wheel is below a predetermined threshold, and outputs a second signal different from the first signal to the control device when the diameter of the grinding wheel is greater than the threshold. Upon receiving the first signal from the sensor, the control device sets an upper limit of the rotational speed to the first upper limit value and controls the rotational speed to not exceed the first upper limit value. Upon receiving the second signal from the sensor, the control device sets the upper limit of the rotational speed to a second upper limit value that is slower than the first upper limit value and controls the rotational speed to not exceed the second upper limit value. The larger the diameter of the grinding wheel, the slower the permissible rotational speed of the grinding wheel. The first upper limit value is a value below the permissible rotational speed when the diameter of the grinding wheel is the threshold value.

[0006] According to another technical solution of this disclosure, a machine tool control method includes the following steps: a step of controlling the rotational speed of a spindle that rotates a grinding wheel on a workpiece; a step of a sensor outputting a first signal to the control device when the diameter of the grinding wheel is below a predetermined threshold; and a step of the sensor outputting a second signal different from the first signal to the control device when the diameter of the grinding wheel is greater than the threshold. The step of controlling the rotational speed includes the following steps:

[0007] The control device comprises the steps of setting an upper limit for the rotational speed to a first upper limit value based on the sensor's output of a first signal, and controlling the rotational speed to ensure it does not exceed the first upper limit value; and the control device further comprises the steps of setting an upper limit for the rotational speed to a second upper limit value, which is slower than the first upper limit value, based on the sensor's output of a second signal, and controlling the rotational speed to ensure it does not exceed the second upper limit value. The larger the diameter of the grinding wheel, the slower its permissible rotational speed. The first upper limit value is a value below the permissible rotational speed when the grinding wheel's diameter is a threshold value.

[0008] The above and other objects, features, aspects and advantages of the present invention should become apparent from the following detailed description of the invention as understood in conjunction with the accompanying drawings. Attached Figure Description

[0009] Figure 1 It is a 3D view of the machine tool.

[0010] Figure 2 It is a diagram illustrating the internal space of a machine tool.

[0011] Figure 3 It is a three-dimensional view of the grinding wheel, tool holder, and tool sleeve at the tool's standby position.

[0012] Figure 4 This is a diagram illustrating the sensing of the grinding wheel's diameter.

[0013] Figure 5 It is a diagram used to illustrate the permissible rotational speed and the upper limit of the rotational speed corresponding to the diameter of the grinding wheel.

[0014] Figure 6 It is a block diagram used to illustrate the functional structure of the control device.

[0015] Figure 7 It is a flowchart used to illustrate the processing flow in the control device.

[0016] Figure 8 This is a diagram illustrating the sensing of the grinding wheel's diameter.

[0017] Figure 9 Viewed from the +Z axis direction Figure 8 A diagram of a grinding wheel. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same reference numerals are used to denote the same parts and components. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0019] (A. Overview of the machine tool)

[0020] Figure 1This is a perspective view of the machine tool according to this embodiment. (As shown...) Figure 1 As shown in this specification, the axis that is parallel to the left-right direction (width direction) of the machine tool 100 and extends horizontally is called the "Z-axis", the axis that is parallel to the front-back direction (depth direction) of the machine tool 100 and extends horizontally is called the "Y-axis", and the axis that extends vertically is called the "X-axis".

[0021] In detail, will Figure 1 The right direction in the equation is called the "+Z-axis direction", and the left direction is called the "-Z-axis direction". Figure 1 The direction closest to the paper in the diagram is called the "+Y-axis direction," and the direction of depth is called the "-Y-axis direction." The +Y-axis direction corresponds to the front of the machine, and the -Y-axis direction corresponds to the rear of the machine. The upward direction is called the "+X-axis direction," and the downward direction is called the "-X-axis direction."

[0022] In this example, machine tool 100 is a multi-functional machining center. Machine tool 100 includes a column 11, a housing 12, a tool spindle 13, a workpiece spindle 14, a casing 20, a door 30, an operating device 150, and a tool post (not shown). Furthermore, machine tool 100 is not limited to a multi-functional machining center.

[0023] The column 11 is mounted on the housing 20. The column 11 is movable relative to the housing 20 in the Z direction. The column 11 is mounted on the wall of the housing 20 on the -Y axis side.

[0024] The housing 12 is mounted on the column 11. The housing 12 is movable relative to the column 11 along the X-axis. A tool spindle 13 is mounted on the housing 12. The tool spindle 13 is mounted on the side of the housing 12 opposite to the column 11. The housing 12 allows the tool spindle 13 to rotate about an axis 901 (refer to the Y-axis), referred to as the "B-axis". Figure 2 Rotate.

[0025] The tool spindle 13 holds the tool and rotates it. Figure 1 In the example shown, a grinding wheel 41 is illustrated. The position and orientation of the tool spindle 13 can be changed via the column 11 and the housing 12. The workpiece spindle 14 holds the workpiece W and rotates the workpiece W.

[0026] Furthermore, the column 11, housing 12, tool spindle 13, and workpiece spindle 14 are controlled by the control device 500 described later. Figure 4 )control.

[0027] Door 30 is capable of sliding relative to housing 20 in the Z direction. Door 30 has a splash guard 31. The splash guard 31 is transparent, allowing the user of machine tool 100 to visually inspect the machining area. The splash guard 31 is made of acrylic resin. Specifically, the splash guard 31 is formed of polycarbonate.

[0028] The operating device 150 has touch screens 151 and 152. The operating device 150 accepts user input via the touch screens 151 and 152. The operating device 150 displays various information on the touch screens 151 and 152. In addition, each touch screen 151 and 152 has a display and a touch panel.

[0029] Figure 2 This is a diagram illustrating the internal space of machine tool 100. (For example...) Figure 2 As shown, the machine tool 100 has region R1 and region R2.

[0030] First, let's explain area R1. Area R1 is the area where the workpiece is machined (including grinding) (machining area, working area). Area R2 is the area outside the machining area. In area R2, the tool mounted on the tool spindle 13 is replaced.

[0031] Region R1 is composed of sidewalls 21, 22, 23, a bottom portion 24, a top portion (not shown), and a door 30. Sidewall 21 separates region R1 from region R2. A door (not shown) is provided in sidewall 21 that can be opened and closed. This door is opened when changing the tool mounted on the tool spindle 13. Furthermore, the tool is mounted on the tool spindle 13 via a tool holder.

[0032] With the door open, the tool spindle 13 (specifically, a portion of the top side) moves along the Z-axis between regions R1 and R2, as indicated by arrow P. During tool changes, the tool spindle 13 initially moves in the -Z direction, and then moves in the +Z direction after the tool change. The door closes when the tool change is complete.

[0033] Side wall portion 22 is opposite to side wall portion 21 on the side opposite to region R2. A column 11 is provided on side wall portion 23. Top surface portion 24 is opposite to bottom surface portion 24. Side wall portions 21, 22, 23, bottom surface portion 24, top surface portion (not shown), and door 30 form a so-called "grinding wheel guard".

[0034] The side walls 21, 22, 23, bottom section 24, and top section are formed of steel plate. The parts of the door 30, except for the splash guard 31, are also formed of steel plate. In this example, the thickness of these steel plates and the splash guard 31 is referenced to the actual thickness values ​​of the structure.

[0035] Next, area R2 will be described. Area R2 is equipped with a tool magazine 51, a tool transport device 52, and an automatic tool changer (ATC) 53. The automatic tool changer 53 has an ATC arm 531.

[0036] The tool magazine 51 houses various cutting tools along with tool holders and tool sleeves. The tool magazine 51 has multiple tool sleeve holders M1, M2, M3, M4, M5, ... Various cutting tools are stored together with the tool holders and tool sleeves in the tool sleeve holders M1, M2, M3, M4, M5, ... Specifically, each cutting tool is held in a tool holder. In the tool magazine 51, the tool holders are housed in tool sleeves. Tool sleeves are devices for conveying cutting tools and tool holders.

[0037] Tool magazine 51 is used to send the specified tool to the tool transport position. Figure 2 The tool magazine 51 is a ring-shaped conveyor (for holding the tool holder M3). The tool magazine 51 has a shape extending along the X-axis direction (vertical direction). Figure 2 The upper curved portion of the tool magazine 51 is shown in the diagram. The tool holders M1, M2, M3, M4, and M5 are capable of rotating 180 degrees about axis 902. The tool holders M1, M2, M3, M4, and M5 are also capable of moving along the X direction.

[0038] The tool delivery device 52 transports a tool (e.g., grinding wheel 41) from the tool delivery position in the tool magazine 51 to the tool standby position. Specifically, the tool delivery device 52 transports the tool (grinding wheel 41 in this example) and the tool holder 42 to the tool standby position by holding the tool holder 43. Figure 2 In the image, the positions of the grinding wheel 41 and the tool holder 42, indicated by solid lines, represent the "tool standby position".

[0039] The ATC arm 531 holds the tool retainer 42. Specifically, this refers to the portion of the ATC arm 531 tool retainer 42 that protrudes from the tool sleeve 43. More specifically, this refers to the front end 422 of the ATC arm 531 tool retainer. Figure 4 ).

[0040] The ATC arm 531 replaces the tool mounted on the tool spindle 13 by holding a tool holder (in this example, a tool holder 42 with a grinding wheel 41 mounted) at one end and a tool holder with a used tool (e.g., a cutting tool) at the other end.

[0041] In detail, as indicated by arrow Q, the ATC arm 531 can move along the Z-axis. The ATC arm 531 can rotate about axis 903. The tool changing operation is described below.

[0042] ATC arm 531 pulls the grinding wheel 41 and tool holder 42 out of the tool holder 43 by moving in the -Z axis direction. At the same time, ATC arm 531 pulls the tool holder mounted on the tool spindle 13 out of the tool spindle 13 together with the tool.

[0043] The ATC arm 531, by rotating about axis 903, transports the grinding wheel 41 and tool holder 42 from the tool standby position to the tool change position. Conversely, the ATC arm 531, by rotating about axis 903 in this way, transports the tool and tool holder pulled from the tool spindle 13 from the tool change position to the tool standby position. Furthermore, Figure 2 The positions of the grinding wheel 41 and the tool holder 42, indicated by the dashed lines, are the tool change positions.

[0044] Next, the ATC arm 531 moves in the +Z axis direction, thereby mounting the grinding wheel 41 and the tool holder 42 onto the tool spindle 13. Through this movement, the ATC arm 531 stores the tool and tool holder pulled from the tool spindle 13 in the tool holder 43 remaining in the tool standby position. Furthermore, the tool and tool holder stored in the tool holder 43 are transported by the tool transport device 52 to the tool holder holder in the tool magazine 51.

[0045] In addition, the tool magazine 51, the tool transport device 52, and the automatic tool changer 53 are controlled by the control device 500.

[0046] (B. Grinding wheel)

[0047] Figure 3 This is a perspective view of the grinding wheel 41, tool holder 42, and tool sleeve 43 at the tool's standby position. Figure 3 As shown, the grinding wheel 41 is held in the tool holder 42. The tool holder 42 is housed in the tool sleeve 43. Specifically, the rear end 421 of the tool holder 42 ( Figure 4 The blade sheath 43 is stored in the tool holder 43. The tool sheath 43 is fixed to the fixing fixture 90. In this state, the ATC arm 531 ( Figure 2 Only the grinding wheel 41 and the tool holder 42 in the grinding wheel 41, the tool holder 42 and the tool sleeve 43 are transported from the tool standby position to the tool change position.

[0048] The grinding wheel 41 includes a body portion 411 and a shank portion 412. The body portion 411 is mounted on the shank portion 412. The shank portion 412 extends axially about an axis 904. The shank portion 412 has an end portion 4122 on the side of the body portion 411 and an end portion 4121 on the side of the tool holder 42. Figure 4 ).

[0049] The grinding wheel 41 is held in the tool holder 42. More specifically, the shank 412 is held in the tool holder 42. More specifically, the end portion 4121 is held in the tool holder 42. In region R1, with the grinding wheel 41 held in the tool spindle 13 by the tool holder 42, the tool holder 42 rotates. As a result, the shank 412 rotates about axis 904. Furthermore, due to the rotation of the shank 412, the main body 411 also rotates.

[0050] The main body 411 has an outer peripheral surface 4111 that contacts the workpiece W during grinding, and surfaces 4112 and 4113 that are continuous with the outer peripheral surface 4111 and extend radially along the grinding wheel 41 (specifically, the main body 411). In this example, surfaces 4112 and 4113 are annular. The workpiece W is ground while the main body 411 is rotating. Specifically, the workpiece W is ground by rotating the main body 411 while the outer peripheral surface 4111 is in contact with the workpiece W.

[0051] In the tool standby position, the grinding wheel 41 is positioned with its axis 904 parallel to the Z-axis direction. In the tool standby position, the normal directions of surfaces 4112 and 4113 are parallel to the Z-axis direction.

[0052] (C. Sensing)

[0053] Figure 4 This is a diagram illustrating the sensing of the diameter of the grinding wheel 41. Figure 4 This is a side view of the grinding wheel 41, tool holder 42, and tool sleeve 43. The diameter of the grinding wheel 41 is sensed when the grinding wheel 41 is in the tool standby position through which all tools have passed.

[0054] like Figure 4 As shown, the machine tool 100 includes a control unit 500 and a sensor 70. The control unit 500 includes a numerical control unit (not shown), a PLC, a servo control unit, a communication unit, and a data storage unit. The machining program (NC program) is stored in the data storage unit.

[0055] Sensor 70 projects a laser beam onto the grinding wheel 41, which is being fed to the tool standby position. Sensor 70 is a transmission type sensor. Sensor 70 is used to determine whether the diameter of the grinding wheel 41 (hereinafter also referred to as "diameter D") is within any of three numerical ranges defined by two thresholds (100 mm and 130 mm in this example). In this example, the three numerical ranges are "D > 130 mm", "130 mm ≥ D > 100 mm", and "100 mm ≥ D".

[0056] Sensor 70 includes a first sensor 71 and a second sensor 72. The first sensor 71 has a projector 711 and a receiver 712. The second sensor 72 has a projector 721 and a receiver 722. When viewed from the receiver 712 and 722 side, the second sensor 72 is located on the side closer to the axis (rotation axis) 904 of the grinding wheel 41 than the first sensor 71.

[0057] In this example, projectors 711 and 721 are positioned below the tool holder 43. Projectors 711 and 721 can also be positioned below the tool holder 42. Projectors 711 and 721 can also be positioned below the shank 412. The placement of projectors 711 and 721 is not limited to below the tool holder 43, tool holder 42, or shank 412; they can be positioned around the tool holder 43, tool holder 42, or shank 412 (e.g., above, in the +Y axis direction, or in the -Y axis direction).

[0058] Projectors 711 and 721 project laser light in the Z-axis direction. Projectors 711 and 721 also project laser light in a direction parallel to axis 904. Receiver 712 is positioned to receive the laser light projected from projector 711. Receiver 722 is positioned to receive the laser light projected from projector 721. Receivers 712 and 722 are connected to control device 500.

[0059] In this example, when the light receiver 712 receives the laser light projected from the projector 711, it sends a predetermined signal (hereinafter also referred to as "signal #1") to the control device 500. For example, the light receiver 712 sends an electrical signal with a voltage of a first voltage V1 to the control device 500. When the laser light projected from the projector 711 is blocked by the grinding wheel 41 and cannot be received, the light receiver 712 sends a different signal than signal #1 (hereinafter also referred to as "signal #2") to the control device 500. For example, the light receiver 712 sends an electrical signal with a voltage of a second voltage V2 to the control device 500.

[0060] When receiver 722 receives laser light projected from transmitter 721, it sends the same signal as signal #1 (hereinafter also referred to as "signal #3") to control device 500. When laser light projected from transmitter 721 is blocked by grinding wheel 41 and cannot be received, receiver 722 sends the same signal as signal #2 (hereinafter also referred to as "signal #4") to control device 500. Control device 500 distinguishes and manages signals from receiver 712 and signals from receiver 722.

[0061] The first sensor 71 (specifically, the projector 711 and the receiver 712) is configured such that the receiver 712 cannot receive the position of the laser beam projected from the projector 711 when the diameter (outer diameter) D of the grinding wheel 41 is greater than 130 mm.

[0062] The second sensor 72 (specifically, the projector 721 and the receiver 722) is configured such that the receiver 722 cannot receive the position of the laser beam projected from the projector 721 when the diameter D of the grinding wheel 41 is greater than 100 mm.

[0063] When the control device 500 receives signal #1 from the light receiver 712 and signal #3 from the light receiver 722, it determines that the diameter D of the grinding wheel 41 is 100 mm or less. That is, when both the light receiver 712 and the light receiver 722 receive laser light, the control device 500 determines that the diameter D of the grinding wheel 41 is 100 mm or less. Alternatively, when the control device 500 receives signal #3 from the light receiver 722, it determines that the diameter D of the grinding wheel 41 is 100 mm or less, regardless of the type of signal sent from the light receiver 712.

[0064] When the control device 500 receives signal #1 from the light receiver 712 and signal #4 from the light receiver 722 ( Figure 4 Under the condition that the diameter D of the grinding wheel 41 is greater than 100mm and less than 130mm, it is determined that... Figure 4 As shown in the status, when the control device 500 receives both signal #1 and signal #4, the control device 500 determines that the diameter D of the grinding wheel 41 is greater than 100mm and less than 130mm.

[0065] When the control device 500 receives signal #2 from the photodetector 712 and signal #4 from the photodetector 722, it determines that the diameter D of the grinding wheel 41 is greater than 130 mm. In the machine tool 100, there is a structure that prevents automatic replacement of grinding wheels with a diameter D greater than 130 mm in area R2. Therefore, the control device 500 causes the operating device 150 to display an error (warning). Alternatively, when the control device 500 receives signal #2 from the photodetector 712, it may determine that the diameter D of the grinding wheel 41 is greater than 130 mm regardless of the type of signal sent from the photodetector 722.

[0066] Alternatively, the configuration of the projector 711 and the receiver 712 can be reversed. Similarly, the configuration of the projector 721 and the receiver 722 can be reversed.

[0067] (D. Control of the rotational speed of the grinding wheel)

[0068] (d1: Permissible rotational speed)

[0069] In this example, the rotational speed of the tool spindle 13 is expressed as revolutions per minute (rpm). For ease of explanation, the maximum rotational speed of the tool spindle 13 will be set to 20,000 rpm. Regarding the grinding wheel, requirements are specified in JIS (Japanese Industrial Standards) (JIS B 6033:2018). The permissible rotational speed of a grinding wheel that meets these requirements will be explained below. The permissible rotational speed depends on the diameter of the grinding wheel, as detailed later.

[0070] In JIS B 6033:2018 (hereinafter referred to as "JIS"), the required thickness t of the steel plate is specified. p The translational kinetic energy E of the grinding wheel fragments trans Defined as shown in equations (1) and (2) below.

[0071] t p =0.4×E trans 0.37 … (1)

[0072] E trans =0.051×m×(1-Q 3 ) 2 / (1-Q 2 ) 2 ×ν 2 … (2)

[0073] Additionally, m represents the mass of the grinding wheel [kg]. Q represents the diameter ratio [-]. ν represents the operating circumferential speed of the grinding wheel [m / sec].

[0074] According to JIS, when the diameter of the grinding wheel is 508 mm or less, Q is defined as 0.2 (with the maximum usable tool diameter set to φ130 mm). If this value is used, the formula for ν can be simplified as shown in equation (3) below.

[0075] ν 2 ≒(t p / 0.4) 1 / 0.37 / (0.054457×m) … (3)

[0076] steel plate thickness t p Defined by the machine. Therefore, the usable circumferential speed (with a fixed plate thickness) ν can be defined by the mass m of the grinding wheel.

[0077] JIS (Junior Standards) mandates monitoring the spindle speed after deceleration. It specifies that this "speed after deceleration" must be set as a mechanical parameter. In machine tools, particularly in CNC (Computer Numerical Control) systems, the value of the aforementioned mass m needs to be calculated when rotational speed is limited. JIS defines a cylindrical grinding wheel, assuming the inner diameter is the grinding wheel diameter × 0.2 (Q) for calculation. Furthermore, the density ρ of the grinding wheel is defined as 2.4 g / cm³. 3 Therefore, in order to calculate the mass m, it is necessary to calculate the volume of the grinding wheel.

[0078] The grinding wheel (more specifically, the main body) is cylindrical. If the diameter of the grinding wheel is set as D and the thickness of the grinding wheel is set as H, then the volume V of the grinding wheel is expressed by the following formula (4).

[0079] V = π × {(D / 2)} 2 -(D×0.2 / 2) 2}×H … (4)

[0080] Calculate the mass m corresponding to the diameter D of the grinding wheel, and define ν with mass m as described above, thereby calculating the permissible rotational speed S. The permissible rotational speed S is expressed, for example, by the following equation (5).

[0081] S = ν × 60 × 1000 / (π × D)

[0082] =6,974,310 × (1 / m) 1 / 2 / (π×D) … (5)

[0083] This allows the rotational speed S to be a function of the grinding wheel's diameter D. If the grinding wheel's thickness H is determined, then the mass m is also determined. Hereinafter, the thickness of grinding wheel 41 is set to 65 mm. Furthermore, this thickness is provided as an example.

[0084] (d2: Setting the upper limit and controlling the rotation speed)

[0085] Figure 5 This is a diagram illustrating the permissible rotational speed S and the upper limit of the rotational speed corresponding to the diameter D of the grinding wheel 41. For example... Figure 5 As shown, the larger the diameter D of the grinding wheel 41, the slower the permissible rotational speed S. Furthermore, in the region where the diameter D of the grinding wheel 41 is less than 95 mm, the permissible rotational speed S exceeds 22,000 / min, and is therefore not shown in the figure.

[0086] As described above, the maximum rotational speed of the tool spindle 13 is 20,000 rpm. The maximum diameter of the grinding wheel 41 that can be replaced via the ATC arm 531 is 130 mm.

[0087] According to equation (5), the permissible rotational speed S of the grinding wheel 41 when the diameter D is 100 mm is 20,418 / min. Thus, the permissible rotational speed S of the grinding wheel 41 when the diameter D is 100 mm is faster than the maximum rotational speed (20,000 / min) of the tool spindle 13. Similarly, the permissible rotational speed S of the grinding wheel 41 when the diameter D is 130 mm is at least faster than 12,000 / min.

[0088] Therefore, in this example, when the diameter D of the grinding wheel 41 is 100 mm or less, the control device 500 sets the upper limit of the rotational speed of the tool spindle 13 to 20,000 / min. When the diameter D of the grinding wheel 41 is greater than 100 mm but less than 130 mm, the control device 500 sets the upper limit of the rotational speed of the tool spindle 13 to 12,000 / min.

[0089] The control device 500 determines whether the diameter D of the grinding wheel 41 is 100 mm or less based on the output from the second sensor 72. The control device 500 determines whether the diameter D of the grinding wheel 41 is 130 mm or less based on the output from the first sensor 71. In detail, in this example, the control device 500 determines whether the diameter D of the grinding wheel 41 is included in any of the above three numerical ranges based on the combination of the outputs from the first sensor 71 and the second sensor 72.

[0090] Thus, the relationship between the diameter D of the grinding wheel 41 and the upper limit U of the rotational speed of the tool spindle 13 is expressed by the following equations (6) and (7).

[0091] U=20,000 / min (D≤100mm) … (6)

[0092] U=12,000 / min (100mm<D≤130mm) … (7)

[0093] Based on signals from sensors 70 (specifically, first sensor 71 and second sensor 72), control device 500 controls the rotational speed of the tool spindle 13 to be below a permissible rotational speed S determined by the diameter D of the grinding wheel 41. Specifically, based on these signals, control device 500 sets an upper limit U for the permissible rotational speed S. Control device 500 controls the rotational speed of the tool spindle 13 to ensure it does not exceed the upper limit U.

[0094] In this example, when the diameter D of the grinding wheel 41 is 100 mm or less, the control device 500 sets the upper limit value U to the maximum rotational speed of the tool spindle 13 (20,000 / min). When the diameter D of the grinding wheel 41 is greater than 100 mm (in this example, and the diameter of the grinding wheel 41 is 130 mm or less), the control device 500 sets the upper limit value U to a predetermined value less than the maximum rotational speed (12,000 / min). Furthermore, the above-mentioned upper limit value U is an example and is not limited to it.

[0095] (d3: Functional structure)

[0096] Figure 6 This is a block diagram primarily used to illustrate the functional structure of the control device 500. For example... Figure 6 As shown, the control device 500 includes a rotation speed control unit 510. The rotation speed control unit 510 has a grinding wheel diameter determination unit 511 and an upper limit setting unit 512.

[0097] The rotational speed control unit 510 controls the rotational speed of the tool spindle 13. The grinding wheel diameter determination unit 511 determines the diameter D of the grinding wheel 41 based on the output from the sensors 70 (in this example, the first sensor 71 and the second sensor 72). In this example, the grinding wheel diameter determination unit 511 determines whether the diameter D of the grinding wheel is less than 100 mm, greater than 100 mm but less than 130 mm, or greater than 130 mm. The grinding wheel diameter determination unit 511 determines a range of values ​​including the diameter D of the grinding wheel 41 from three possible ranges.

[0098] The upper limit setting unit 512 sets an upper limit value U corresponding to the diameter D of the grinding wheel 41. In this example, the upper limit setting unit 512 sets the upper limit value U to either 20,000 / min or 12,000 / min. The rotation speed control unit 510 controls the rotation speed of the tool spindle 13 so that the rotation speed of the tool spindle 13 does not exceed the aforementioned upper limit value U.

[0099] (d4: Control structure)

[0100] Figure 7 This is a flowchart illustrating the processing flow within the control device 500. For example... Figure 7 As shown, in step S1, the control device 500 determines whether the photodetector 712 of the first sensor 71 has received laser light. Specifically, the control device 500 determines which of the received signals, #1 and #2, is being received.

[0101] If it is determined that the light receiver 712 has not received laser light (no in step S1), the control device 500 causes the operation device 150 to display a predetermined error in step S5. Specifically, the control device 500 initiates step S5 upon receiving signal #2 from the light receiver 712.

[0102] If it is determined that the photodetector 712 has received laser light (yes in step S1), the control device 500 determines in step S2 whether the photodetector 722 of the second sensor 72 has received laser light. Specifically, when the control device 500 receives signal #1 from the photodetector 712, it causes the process to proceed to step S2.

[0103] If it is determined that the photodetector 722 has received laser light (yes in step S2), the control device 500 sets the upper limit value U of the rotational speed of the grinding wheel 41 to 20,000 / min in step S3. Specifically, the control device 500 proceeds to step S3 when it receives signal #3 from the photodetector 722 in addition to signal #1. Thus, when the control device 500 receives both signal #1 and signal #3 simultaneously, it sets the upper limit value U to 20,000 / min. In this case, the control device 500 controls the rotational speed of the tool spindle 13 so that the rotational speed of the tool spindle 13 does not exceed the aforementioned 20,000 / min.

[0104] If it is determined that the photodetector 722 has not received laser light (no in step S2), the control device 500 sets the upper limit value U of the rotational speed of the grinding wheel 41 to 12,000 / min in step S4. Specifically, the control device 500 proceeds to step S4 when it receives signal #4 from the photodetector 722 in addition to signal #1. Thus, the control device 500 sets the upper limit value U to 12,000 / min when it receives both signal #1 and signal #4 simultaneously. In this case, the control device 500 controls the rotational speed of the tool spindle 13 so that the rotational speed of the tool spindle 13 does not exceed the aforementioned 12,000 / min.

[0105] Thus, the control device 500 performs different controls based on the combination of outputs from the first sensor 71 and the second sensor 72. Alternatively, when the control device 500 receives signal #3 from the second sensor 72, it may set the upper limit value U to 20,000 / min regardless of the type of signal sent from the first sensor 71.

[0106] <Summary>

[0107] (1) The machine tool 100 includes: a tool spindle 13 that rotates the grinding wheel 41 for grinding the workpiece W; a control device 500 that controls the rotational speed of the tool spindle 13; and a sensor 70. The sensor 70 includes: a first sensor 71 that outputs signal #1 to the control device 500 when the diameter D of the grinding wheel 41 is less than 130 mm, and outputs signal #2 to the control device 500 when the diameter D of the grinding wheel 41 is greater than 130 mm; and a second sensor 72 that outputs signal #3 to the control device 500 when the diameter D of the grinding wheel 41 is less than 100 mm, and outputs signal #4 to the control device 500 when the diameter D of the grinding wheel 41 is greater than 100 mm.

[0108] Thus, the machine tool 100 is equipped with the following sensors 70: (i) outputting signals #2 and #4 to the control device 500 when the diameter D of the grinding wheel 41 is greater than 130 mm, (ii) outputting signals #1 and #4 to the control device 500 when the diameter D of the grinding wheel 41 is less than 130 mm but greater than 100 mm, and (iii) outputting signals #1 and #3 to the control device 500 when the diameter D of the grinding wheel 41 is less than 100 mm.

[0109] When the control device 500 receives signals #1 and #3 from the sensor 70, it sets the upper limit value U of the rotational speed of the tool spindle 13 to 20,000 / min (the first upper limit value) and controls the rotational speed of the tool spindle 13 to not exceed 20,000 / min.

[0110] When the control device 500 receives signals #1 and #4 from the sensor 70, it sets the upper limit value U of the rotational speed of the tool spindle 13 to 12,000 / min (the second upper limit value) and controls the rotational speed of the tool spindle 13 to not exceed 12,000 / min.

[0111] The larger the diameter D of the grinding wheel 41, the slower the permissible rotational speed S of the grinding wheel 41. A rotational speed of 20,000 / min (the first upper limit) is a value below the permissible rotational speed S when the diameter D of the grinding wheel 41 is 100mm. A rotational speed of 12,000 / min (the second upper limit) is a value below the permissible rotational speed S when the diameter D of the grinding wheel 41 is the maximum diameter of the grinding wheel 41 that can be replaced by the automatic tool changer 53 (130mm in this example).

[0112] With this structure, the rotational speed of the grinding wheel 41 can be automatically controlled to a permissible rotational speed S determined by the diameter D of the grinding wheel 41.

[0113] Furthermore, in this example, the combination of signal #1 and signal #3 corresponds to the "first signal" in this disclosure, and the combination of signal #1 and signal #4 corresponds to the "second signal" in this disclosure.

[0114] (2) The grinding wheel 41 includes: a shank 412 that extends axially about a predetermined axis 904 and rotates about the predetermined axis 904; and a body 411 that is mounted on the shank 412 and grinds the workpiece W. The sensor 70 projects a laser beam onto the body 411 parallel to the predetermined axis 904. With this structure, the control device 500 can obtain different signals when the diameter D of the grinding wheel 41 is less than 100 mm, greater than 100 mm but less than 130 mm, and greater than 130 mm.

[0115] (3) The machine tool 100 also includes: an automatic tool changer 53; a tool magazine 51 capable of storing the grinding wheel 41; and a tool transport device 52 that transports the grinding wheel 41 from the tool magazine 51 to the tool standby position of the automatic tool changer 53. The sensor 70 projects a laser onto the grinding wheel 41 that has been transported to the tool standby position.

[0116] With this structure, the diameter D of the grinding wheel 41 can be measured while the tool is in standby position. Specifically, it can be determined which of the three numerical ranges the diameter D falls within. Therefore, it is not necessary to allocate time solely for measuring the diameter D of the grinding wheel 41. Thus, compared to measuring the diameter of the grinding wheel 41 after it has moved to the area R1 where the workpiece W is being machined, the preparation time required for machining the workpiece W can be shortened.

[0117] (4) The main body 411 has an outer peripheral surface 4111 that contacts the workpiece W when grinding the workpiece W, and surfaces 4112 and 4113 that are continuous with the outer peripheral surface 4111 and extend radially along the grinding wheel 41. The sensor 70 projects a laser toward the surface 4113.

[0118] Depending on the type of grinding wheel 41, the Z-axis position of the main body 411 at the tool standby position may vary. Therefore, when projecting a laser onto the outer peripheral surface 4111, it is necessary to install multiple sensors in the Z-axis direction, or to enable the sensors to move in the Z-axis direction. In the machine tool 100, by configuring a structure that projects the laser toward the surface 4113, the sensor device structure can be simplified compared to a structure that projects the laser toward the outer peripheral surface 4111.

[0119] (5) The first sensor 71 includes a laser projector 711 that projects a laser beam and a laser receiver 712 that receives the laser beam. When the laser receiver 712 receives the laser beam, the first sensor 71 outputs signal #1 to the control device 500. When the laser receiver 712 does not receive the laser beam, the first sensor 71 outputs signal #2 to the control device 500. Similarly, the second sensor 72 includes a laser projector 721 that projects a laser beam and a laser receiver 722 that receives the laser beam. When the laser receiver 722 receives the laser beam, the second sensor 72 outputs signal #3 to the control device 500. When the laser receiver 722 does not receive the laser beam, the second sensor 72 outputs signal #4 to the control device 500.

[0120] (6) When the diameter D of the grinding wheel 41 is 100 mm, the allowable rotational speed S is faster than the maximum rotational speed (20,000 / min) of the tool spindle 13. When the control device 500 receives signals #1 and #3 from the sensor 70, it sets the maximum rotational speed as the upper limit value U (first upper limit value) of the rotational speed of the tool spindle 13.

[0121] <Variation Example>

[0122] (1) In the above description, the structure of the machine tool 100 having a sensor 70 was described as an example. Specifically, the sensor 70, which includes a first sensor 71 and a second sensor 72 that respectively project a laser beam, was described as an example. Hereinafter, the structure of the machine tool 100 having a line sensor 80 instead of the sensor 70 will be described.

[0123] and Figure 4 Similarly, Figure 8 This is a diagram illustrating the sensing of the diameter of the grinding wheel 41. Figure 8 This is a side view of the grinding wheel 41, the tool holder 42, and the tool sleeve 43. Figure 9 Viewed from the +Z axis direction Figure 8 The image shows grinding wheel 41.

[0124] Reference Figure 8 and Figure 9 The line sensor 80 includes a projector 81 and a receiver 82. For example... Figure 9 As shown, the projector 81 has multiple laser projection sections 801. The multiple laser projection sections 801 are arranged in a row along the Y-axis. In this example, the multiple laser projection sections 801 are arranged at equal intervals. The receiver 82 has multiple laser receiving sections (not shown).

[0125] In this example, the projector 81 is positioned below the tool holder 43. The projector 81 can also be positioned below the tool holder 42. The projector 81 can also be positioned below the shank 412. The placement of the projector 81 is not limited to below the tool holder 43, tool holder 42, or shank 412; it can be positioned around the tool holder 43, tool holder 42, or shank 412 (e.g., above, in the +Y axis direction, or in the -Y axis direction).

[0126] The projector 81 projects multiple laser beams in the Z-axis direction. The projector 81 projects laser beams in a direction parallel to axis 904. The receiver 82 is positioned to receive the multiple laser beams projected from the projector 81. Each laser receiving section of the receiver 82 is opposite a different laser projection section 801 in the Z-axis direction. The receiver 82 is connected to the control device 500.

[0127] exist Figure 9 In the example shown, a portion of the multiple laser beams projected from the multiple laser projection sections 801 is blocked by the main body 411 of the grinding wheel 41. More specifically, a portion of the multiple laser beams is blocked by the back surface 4113 of the surface 4112. Figure 8 (Obstruction). For example, in this case, the central 5 of the 11 laser beams are blocked. In this case, the 6 laser receivers at both ends of the plurality of laser receivers of the photodetector 82 receive the laser.

[0128] The control device 500 determines the diameter D of the grinding wheel 41 based on the number of laser beams received by the photodetector 82. Specifically, the control device 500 determines which of a plurality of numerical ranges the diameter D of the grinding wheel falls within. To determine whether the diameter D of the grinding wheel 41 is less than 100 mm or less than 130 mm, the boundary of the plurality of numerical ranges must include at least 100 mm and 130 mm.

[0129] As described above, the sensor in this modified example is a laser-type line sensor 80, and it has a projector 81 that projects multiple laser beams and a receiver 82 that receives each laser beam. The control device 500 determines the numerical range of the diameter D of the grinding wheel 41 based on the number of laser beams received by the receiver 82 among the multiple laser beams.

[0130] (2) The above description uses a structure with two upper limit values ​​U as an example, but it is not limited to this. When the diameter D of the grinding wheel 41 is greater than the first threshold (100 mm in this example), the upper limit value U can be made different in stages according to the above numerical range, provided that the allowable rotation speed S is below. Specifically, the larger the diameter D of the grinding wheel 41 is, the smaller the upper limit value U becomes.

[0131] (3) In the above description, the structure of the machine tool 100 having only the first sensor 71 and the second sensor 72 as the sensor 70 is used as an example, but it is not limited to this. It is also possible that the sensor 70 has other sensors. In this case, the threshold can also be set to a value other than 100mm or 130mm. Therefore, in this case, the rotational speed of the tool spindle 13 can be controlled more precisely.

[0132] For example, by using a sensor that outputs signal #5 when the diameter D of the grinding wheel 41 is greater than a specified value between 100 mm and 130 mm (e.g., 115 mm) and outputs signal #6 when it is less than the specified value, it is possible to further set an upper limit value (e.g., 15,000 / min) between 20,000 / min (first upper limit value) and 12,000 / min (second upper limit value).

[0133] (4) In the above description, the structure of the machine tool 100 having a first sensor 71 and a second sensor 72 as sensor 70 was used as an example, but it is not limited to this. The machine tool 100 may, for example, only have the second sensor 72. As long as there is at least the second sensor 72, it is possible to determine whether the diameter D of the grinding wheel 41 is less than or greater than 100 mm. In such a case, the machine tool 100 can be said to have the following structure.

[0134] The machine tool 100 includes: a tool spindle 13 that rotates the grinding wheel 41 that grinds the workpiece W; a control device 500 that controls the rotational speed of the tool spindle 13; and a second sensor 72 that outputs signal #3 to the control device 500 when the diameter D of the grinding wheel 41 is less than 100 mm, and outputs signal #4 to the control device 500 when the diameter D of the grinding wheel 41 is greater than 100 mm.

[0135] When the control device 500 receives signal #3 from the second sensor 72, it sets the upper limit value U of the rotational speed of the tool spindle 13 to 20,000 / min (first upper limit value) and controls the rotational speed of the tool spindle 13 to not exceed 20,000 / min. When the control device 500 receives signal #4 from the second sensor 72, it sets the upper limit value U of the rotational speed of the tool spindle 13 to 12,000 / min (second upper limit value) and controls the rotational speed of the tool spindle 13 to not exceed 12,000 / min.

[0136] The second sensor 72 includes a projector 721 that projects laser light and a receiver 722 that receives the laser light. When the receiver 722 receives laser light, the second sensor 72 outputs signal #3 to the control device 500. When the receiver 722 does not receive laser light, the second sensor 72 outputs signal #4 to the control device 500.

[0137] Based on this structure, the rotational speed of the grinding wheel 41 can also be automatically controlled to a permissible rotational speed S determined by the diameter D of the grinding wheel 41.

[0138] (5) In the above description, the diameter D is used as the diameter of the grinding wheel 41, but it is not limited to this. The radius can also be used as the diameter of the grinding wheel 41.

[0139] Embodiments of the present invention have been described, but should be considered illustrative rather than restrictive in all respects. The scope of the invention is set forth in the claims and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0140] This application is based on Japan Patent Application No. 2025-073171 filed with the Japan Patent Office on April 25, 2025 and Japan Patent Application No. 2026-016805 filed with the Japan Patent Office on February 4, 2026, the entire contents of which are incorporated herein by reference.

Claims

1. A machine tool, wherein, This machine tool has the following features: The spindle rotates the grinding wheel used to grind the workpiece. A control device that controls the rotational speed of the spindle; and A sensor outputs a first signal to the control device when the diameter of the grinding wheel is below a predetermined threshold, and outputs a second signal different from the first signal to the control device when the diameter of the grinding wheel is greater than the threshold. Upon receiving the first signal from the sensor, the control device sets the upper limit of the rotational speed to a first upper limit value and controls the rotational speed to ensure that it does not exceed the first upper limit value. Upon receiving the second signal from the sensor, the control device sets the upper limit of the rotation speed to a second upper limit that is slower than the first upper limit, and controls the rotation speed to ensure that it does not exceed the second upper limit. The larger the diameter of the grinding wheel, the slower its permissible rotational speed. The first upper limit value is a value below the allowable rotational speed when the diameter of the grinding wheel is the threshold value.

2. The machine tool according to claim 1, wherein, The grinding wheel includes: A handle that extends axially about a predetermined axis and rotates about the predetermined axis; and The main body is mounted on the handle and grinds the workpiece. The sensor projects a laser beam onto the main body in a direction parallel to the defined axis.

3. The machine tool according to claim 2, wherein, The machine tool also features: Automatic tool changer; Tool magazine, which can hold the grinding wheel; and A conveying device transports the grinding wheel from the tool magazine to the tool standby position of the automatic tool changer. The sensor projects the laser onto the grinding wheel that has been transported to the tool standby position.

4. The machine tool according to claim 3, wherein, The main body has an outer peripheral surface that contacts the workpiece during grinding and a surface that is continuous with the outer peripheral surface and extends radially in the grinding wheel. The sensor projects the laser toward the surface.

5. The machine tool according to claim 4, wherein, The sensor includes a laser projector that projects laser light and a laser receiver that receives the laser light. When the light receiver receives the laser, the sensor outputs the first signal to the control device. If the light receiver does not receive the laser, the sensor outputs the second signal to the control device.

6. The machine tool according to any one of claims 1 to 5, wherein, When the diameter of the grinding wheel is the threshold value, the allowable rotational speed is faster than the maximum rotational speed of the spindle. Upon receiving the first signal from the sensor, the control device sets the maximum rotational speed to the first upper limit value.

7. The machine tool according to any one of claims 3 to 5, wherein, The second upper limit is a value below the allowable rotational speed when the diameter of the grinding wheel is the maximum diameter of the grinding wheel that can be replaced by the automatic tool changer.

8. A method for controlling a machine tool, wherein, The control method includes the following steps: The steps of the control device controlling the rotational speed of the spindle that rotates the grinding wheel of the workpiece; The step of the sensor outputting a first signal to the control device when the diameter of the grinding wheel is below a predetermined threshold; as well as When the diameter of the grinding wheel is greater than the threshold, the sensor outputs a second signal, different from the first signal, to the control device. The steps for controlling the rotational speed include the following: The control device sets the upper limit of the rotation speed to a first upper limit value based on the output of the sensor to the first signal, and controls the rotation speed so that it does not exceed the first upper limit value. as well as The control device, based on the sensor's output of the second signal, sets the upper limit of the rotational speed to a second upper limit that is slower than the first upper limit, and controls the rotational speed so that it does not exceed the second upper limit. The larger the diameter of the grinding wheel, the slower its permissible rotational speed. The first upper limit value is a value below the allowable rotational speed when the diameter of the grinding wheel is the threshold value.

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