JP3057218B2 - Tool edge detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool edge detecting device mounted on an NC machine tool for detecting a tool edge position and setting a tool correction value. The present invention relates to a tool edge detecting device having a function of automatically generating a tool correction amount for detecting and correcting a processing error caused by deformation of a tool due to a cutting resistance, and automatically setting the amount.

[0002]

2. Description of the Related Art In machining a workpiece by an NC machine tool, a tool edge detecting device mounted on the machine tool detects a position of a tool edge relative to a machine origin of a tool used for machining and attaches a reference tool before machining. In this case, a tool correction value is calculated from the difference from the position of the cutting edge, and the tool correction value is set and input to the NC machine tool to correct the machining program and perform machining. FIG. 11 is an explanatory view showing a conventional tool edge detecting device mounted on an NC lathe for setting a tool correction value. In this tool cutting edge detecting device, a sensor arm 17 rotatable around a pivot axis perpendicular to the main shaft 36 is mounted on a headstock 37, and is attached to the tip of the sensor arm 17 when the sensor arm 17 swings out. The touch sensor 38 is located on the front surface of the chuck 39. When the turret tool post 15 is moved, the tool tip Tp becomes the touch sensor 38.
The relative coordinate value between the position data of the tool drive shaft at this time and the position data when the reference tool is brought into contact with the tracing stylus 38a is calculated as a tool correction value. , And the NC lathe. Also, if you want to perform a machining operation with high dimensional accuracy, enter a tool correction value, perform trial cutting, add the error amount obtained by measuring the workpiece after cutting to the previous tool correction value, Was re-entered as a new tool correction value to execute the machining operation.

[0003]

The above-mentioned conventional tool edge position detecting device mounted on a machine tool accurately detects a tool edge position with respect to a machine origin, calculates a tool correction value, and sets the tool correction value on the machine tool. be able to. However, even if the tool correction value is set and input, the cutting edge of the tool is deformed by resistance at the time of cutting, so that the machine tool cannot machine the workpiece with high dimensional accuracy.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, detects a tool edge position with high accuracy, estimates the amount of deformation of a tool due to resistance during cutting from tool rigidity and machining conditions, An object of the present invention is to provide a tool edge detection device capable of calculating a tool correction value in consideration of a deformation amount and automatically setting the tool correction value in the machine tool, thereby enabling the machine tool to perform machining with high dimensional accuracy.

[0005]

According to the present invention, there is provided a tool cutting edge which is mounted on an NC lathe, detects a cutting edge position of a tool attached to the NC lathe, calculates a tool correction value, and sets the tool correction value on the NC lathe. A detecting device, which detects a contact with a tool edge by a tracing stylus having a cutting edge contact surface and outputs a contact detection signal, a cutting edge position contact detecting section, a cutting edge position measuring mode for detecting contact with the tool cutting edge, and a tool rigidity. Measuring mode generating means for executing a cutting edge rigidity measuring mode for detecting a cutting edge position, outputting cutting edge position data at the time of receiving the contact detection signal, and sending an axial movement amount in a probe contacting process at the time of tool rigidity measurement. Means, a stylus displacement amount detection unit that detects a displacement amount of the stylus pressed by a tool in the stylus pressing process, and outputs a displacement detection signal, and an axial movement amount in the stylus pressing process. From the gauge the amount of displacement detected by serial measurement element displacement detecting unit that is provided between the tool rigidity calculation unit for calculating a tool rigidity.

[0006] Further, the tool is mounted on an NC machine tool that performs machining by attaching a tool to a spindle that is rotatably supported on the spindle head, and detects the position of the cutting edge of the tool attached to the spindle of the machine tool to obtain a tool correction value. A tool edge detection device that calculates a tool edge and detects the contact between the tool edge and a tracing stylus having a blade edge contact surface, and outputs a contact detection signal; and a tool edge. Measuring mode generating means for executing a blade edge position measuring mode for detecting contact and a tool rigidity measuring mode for detecting tool rigidity, and outputting blade edge position data at the time of receiving the contact detection signal, and a step of pressing a stylus at the time of measuring the tool rigidity. Cutting edge position detecting means for sending the amount of axial movement in the step, and detecting the displacement of the tracing stylus pressed by a tool in the process of pressing the tracing stylus, and detecting the displacement of the tracing stylus for outputting a displacement detection signal. If, in the provision and edge stiffness calculator for calculating a tool rigidity from the detected measuring element displacement axis movement amount from the measuring element displacement amount detection section at the gauge head pressing process.

[0007]

[Function] After the tool blade is brought into contact with the blade contact surface of the measuring element and the position of the tool blade with respect to the machine origin is detected, in this state, the tool blade is further pressed against the blade contact surface and measured. The child is displaced. Then, the tracing stylus displacement amount and the axial movement amount at this time are detected, and the stiffness of the tool is calculated from these values and the stiffness of the tracing stylus determined in advance. Further, the resistance at the time of cutting is estimated from the tool rigidity and the processing conditions, and the deformation amount of the tool caused by the resistance at the time of cutting is calculated. Then, a tool correction value for compensating the deformation amount is calculated, and the correction value is set and input to the machine tool. Therefore, since the machine tool equipped with the tool edge detection device operates to correct the correction value in consideration of the deformation amount, it is possible to perform processing with high dimensional accuracy with reduced processing errors due to tool deformation. Can be.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. [Embodiment 1] FIG. 1 is a block diagram showing a basic configuration of a tool edge position detecting device for an NC lathe according to the present invention.
The tool edge position detecting device includes a tool edge Tp of the tool T driven by the servomotor 14 and a blade edge contact surface 16 of the tracing stylus S.
And a blade tip position contact detection unit 1 that outputs a contact detection signal when a contact is made, and a probe contact amount detection unit that detects a displacement amount of the probe S pressed by the tool T after the contact detection and simultaneously outputs a displacement detection signal. A measuring mode generating means 2 for executing a cutting edge position measuring mode for measuring a cutting edge position and a tool rigidity measuring mode for measuring a tool rigidity in a measuring program;
And a blade edge position detecting means 3 which, upon receiving a contact detection signal output from the blade position contact detection unit 1 and a displacement detection signal output from the tracing stylus displacement amount detection unit 4, detects shaft position data at the time of signal reception. A cutting edge rigidity calculating section 5 for calculating a tool rigidity from a stylus displacement amount and an axis moving amount detected in a stylus pressing process at the time of tool rigidity measurement and a previously verified stylus rigidity; a cutting edge position measurement mode and a tool; A function generator 6 for outputting a position command corresponding to the rigidity measurement mode,
A position control device 7 that controls the servomotor 14 so that the tool edge Tp is positioned as instructed while feeding back the current position data from the position detector 13, and a process that stores the processing conditions input from the input interface 8. A condition memory unit 9; a cutting back force calculating unit 10 for estimating a cutting back force from the processing conditions read from the processing condition memory unit 9; A tool deformation calculating unit 11 calculated from
There is provided a tool correction value generation unit 12 that generates a tool correction value from the blade edge position data at the time of contact between the tool edge Tp and the tracing stylus S and the amount of tool deformation due to the cutting back force.

The cutting edge position detecting means 3 detects the position data at the time of receiving the contact detection signal from the position detector 13 and temporarily stores it as first position data, and then stores the position data at the time of receiving the displacement detection signal. 2 is detected as the position data of No. 2 and the amount of axial movement in the stylus pressing process from the contact of the cutting edge to the end of pressing of the stylus is obtained from the difference between the first position data and the second position data, and is output. Finds and outputs the blade position data from the data. Tool correction value generator 12
Is the tool edge Tp detected by the edge position detecting means 3
The relative coordinates between the blade position data at the time of contact of the probe and the stylus S with the blade position data of the reference tool are determined. In this way, a tentative tool correction value of the tool to be measured is determined, and the amount of blade edge deformation due to the back force at the time of cutting is added to the tentative tool correction value to generate a true tool correction value. FIG. 2 shows a state in which the tool tip Tp is brought closer to the tracing stylus S of the tool tip detecting device mounted on the sensor arm 17.

Next, the procedure for calculating the amount of deformation of the tool edge caused by the cutting back force will be described. FIG. 3 is an explanatory diagram illustrating a state in which the tool tip Tp of the tool T is in contact with the tracing stylus S from the X-axis plus direction (the direction of the arrow in FIG. 3) and a state in which the tracing stylus S is pressed. X is the position data at the time of contact
1. Assuming that the position data after the stylus is pressed is X2, the axial movement amount Xt in the stylus pressing process can be obtained by the following equation.

Xt = X2-X1 Assuming that the displacement amount of the tracing stylus S at this time is e and the stiffness of the tracing stylus which has been verified in advance is Ks, the tool edge stiffness Kt can be obtained by the following equation.

Kt = Ks ・ e / Xt And the tool edge deformation δ caused by the cutting back force
Is the tool edge rigidity Kt and the cutting back force Fp obtained in Equation 2.
Is calculated using the following equation.

Δ = Fp / Kt The cutting back force is estimated by inputting the data shown in Table 1 below through the input interface 8 and simplifying the three-dimensional cutting by regarding the two-dimensional cutting as an accumulation of narrow two-dimensional cutting. can do.

[Table 1]

FIGS. 4 and 5 show a longitudinal section and a transverse section of the blade edge position contact detecting section 1 and the tracing stylus displacement amount detecting section 4, respectively.
Shown in FIG. 6 is an enlarged explanatory diagram of the tracing stylus displacement amount detection unit 4. The shaft 19 is rotatably mounted on the housing 30 via ball bearings 20a and 20b together with the tracing stylus S and the mover 21. The tracing stylus S has a rectangular parallelepiped shape, and is provided with a cutting edge contact surface 16 at one end of each side surface at a predetermined distance from the center of the shaft 19 so as to be able to detect the cutting edge of various tools. I have. A coil spring 22 wound around the lower end of the shaft 19 so that both ends are locked to the stopper 23 and the mover 21 is used.
Are urged to close the contact between the first contact 24a and the second contact 24b.

Next, the operation of the blade edge position contact detecting section 1 and the tracing stylus displacement amount detecting section 4 will be described. In the cutting edge position measurement mode, when the cutting edge Tp of the tool T attached to the turret tool rest 15 comes into contact with the measuring element S, the measuring element S rotates a minute amount against the urging force of the torsion coil spring 22, and the measuring element The integral mover 21 rotates through the shaft S and the shaft 19. The rotation of the mover 21 causes the first contact 24b to be in contact with the second contact 24b by the bias of the torsion coil spring 22.
Are separated, and the contacts are opened. When detecting that the contact has been opened, the detection switch 25 transmits a contact detection signal. Subsequently, the cutting edge rigidity measurement mode is executed, the movable element 21 rotates, and the contact of the tool cutting edge Tp is detected, and at the same time, the piston 26 attached at a position symmetrical to the first contact 24a with respect to the shaft 19. , Spindle 2
The rocker 28 integrated with 7 rotates and rotates around the support shaft 27.

When the oscillator 28 swings and rotates due to the pressing force of the piston 26, a torsional moment is applied to the support shaft 27, and the support shaft 27 generates a twist angle and simultaneously generates a shear strain on the surface. This shear strain is
On the shaft surface at the lower end of the support shaft 27, 45 ° with respect to the axial direction,-
The torsion angle of the support shaft 27 is determined by detecting with the four strain gauges 29 adhered in the direction of 45 °. Then, the torsion angle is converted into the displacement amount of the tracing stylus S from the previously verified relationship between the strain amount of the support shaft 27 and the displacement amount of the tracing stylus S. When the tracing stylus displacement detecting unit 4 detects the amount of the tracing stylus displacement exceeding the set value, a displacement detection signal is output to the measurement mode generating means 2, and the tool tip Tp presses the tracing stylus S. Then, the stop command of the turret tool post 15 is executed. At this time, the final probe displacement amount is detected.

A stopper 23 is provided between the mover 21 and the rocker 28 so that the measuring element contact surface 16
The stopper 23 locks the mover 21 even when the piston 2 receives an excessive pressing force due to the tool edge Tp.
Since the stroke of the oscillator 6 is suppressed to a certain amount or less, an excessive torsional moment is not applied to the support shaft 27, and the shear strain detecting unit attached to the support shaft 27 is not damaged.

When the turret tool post 15 is retracted after the displacement of the tracing stylus is detected, the turret tool rest 15 is moved to an initial state in which the first contact 24a and the second contact 24b are in contact with each other by the urging force of the torsion coil spring 22. Will be restored. Note that the mover 21 is
Since the torsion coil spring 22 is urged, a tool edge detection signal is not output erroneously due to an external force such as vibration other than pressing of the tool edge Tp.

In the blade edge position contact detecting section 1 and the tracing stylus displacement amount detecting section 4, the shaft 1 is larger than the length from the center of the shaft 19, which is the fulcrum, to the force point of the blade abutting surface 16 which is pressed.
Since the distance from the center of 9 to the first contact point 24a on the mover 21 and the center of the shaft 19 to the piston 26 is sufficiently long, even a small displacement with respect to the power point is greatly amplified. Therefore, the responsiveness and the detection accuracy of the tool edge contact detection and the stylus displacement amount detection are extremely high. Further, the tracing stylus displacement amount detecting section 4 is configured such that the rigidity of the supporting portion of the tracing stylus S including the ball bearings 20a and 20b and the support shaft 27 is sufficiently higher than the tool edge rigidity to be detected. Therefore, the tool edge rigidity is detected with high accuracy.

Next, the operation procedure of the above-described tool edge detection device will be described with reference to the flowchart shown in FIG. In step S1, the cutting edge detection operation of the tool T is started, and the sensor arm 17 located at the retracted position in the headstock 33 is started.
Is rotated to the detection position on the front surface of the chuck 35. Then, in step S2, the turret tool rest 15 is moved at a very small speed, and the tool tip Tp is changed to the tip contact surface 16 of the tracing stylus S.
Contact. Then, when the measurement mode generating means 2 receives the contact detection signal from the blade position contact detection unit 1 in step S3, the operation of the turret tool post 15 is temporarily stopped, and in step S4, the position data when the turret tool post 15 is stopped. Is detected and stored as first position data.

Next, in step S5, the turret tool rest 15 is again moved at a very small speed, the blade contact surface 16 is pressed by the tool tip Tp, and the probe S is displaced by a very small amount. In step S6, the probe Displacement detector 4
In step S7, the displacement amount of the tracing stylus S is detected, and the displacement amount of the tracing stylus S is compared with a preset value. At this time, if the probe displacement does not exceed the set value, the pressing of the tool T is continued. If the set value is exceeded, the tracing stylus displacement amount detection unit 4 outputs a displacement detection signal to the measurement mode generation unit 2 and the blade position detection unit 3, and then the process from step S8 is continued. Then, in step S8, the stop command of the turret tool post 15 is executed by the measurement mode generating means 2, and in step S9, the final displacement of the tracing stylus S after the turret tool post 15 is stopped is detected.

In step S10, the turret tool rest 15
The second position data after the stop is detected, the axial movement amount in the stylus pressing process is calculated from the difference between the first position data and the second position data, and the measurement in the stylus pressing process is performed in step S11. The cutting edge rigidity of the tool T is calculated from the displacement amount and the axial movement amount, and the rigidity of the tracing stylus S that has been verified in advance. Then, in step S12, the processing conditions for using the tool are input from the input interface 8, and in step S13, the back force at the time of cutting is estimated from the processing conditions. Calculate the tool edge deformation amount in the cutting direction from the component force. Then, in step S15, based on the tool edge position data at the time of contact between the tool edge Tp and the tracing stylus S output from the tool edge position detecting means 3, a provisional tool correction value is set so as to match the tool edge position with respect to the mechanical origin of the reference tool. Is generated, and a true tool correction amount is generated and set in consideration of a tool edge deformation amount due to a cutting back force. In step S16, the turret tool rest 15 is retracted. In step S17, the sensor arm 17 is moved to the retracted position in the headstock 33, and the operation is completed.

In this embodiment, the tracing stylus displacement detector 4
In the cutting edge rigidity measurement mode, the tool cutting edge Tp and the probe S
After the contact of the probe tip, the tool tip Tp is further moved by a small amount to detect the displacement of the probe S when the probe S is pressed. After the tool tip Tp is brought into contact with the tracing stylus S to eliminate the detection error of the tracing stylus displacement amount due to the alignment error, the displacement amount when the tracing stylus S is slightly pressed once, and then the further pressing The difference between the displacement and
It can also be configured to detect it as the tracing stylus displacement. In the present embodiment, the case where a general tool having an acute-angled cutting surface is attached is illustrated.However, the tool cutting-edge detecting device of the present invention includes a parting tool, The same effect can be exerted even when a tool having a cutting edge parallel to the drive shaft, such as a cutting tool that can be machined in the direction (for example, a cut grip manufactured by Kyocera Corporation), is attached.

[Embodiment 2] FIG. 8 is a block diagram showing a basic configuration of a tool edge detecting device mounted on a machining center. In FIG. 8, the same components as those of the tool edge detection device of the first embodiment are denoted by the same reference numerals. Note that the same components as those of the first embodiment will not be described because there is no difference in operation.
A spindle 33 is rotatably supported on the spindle head 32.
A tool 34 is attached to the tip of the spindle 33 via a holder (not shown).
Is held. The difference from the tool edge detection device of the first embodiment (FIG. 1) is that the cutting feed component force of the cutting resistance is estimated from the processing conditions read from the processing condition memory unit 9 instead of the cutting back force calculation unit. This is the point that the cutting feed force calculating unit 35 is provided. That is, the tool correction value generation unit 1
Numeral 2 is configured to generate a tool correction value from the cutting edge position data at the time of contact between the tool cutting edge Tp and the tracing stylus S and the amount of tool deformation due to the cutting feed force calculated by the cutting feed force calculator 35. ing.

Next, a description will be given of a procedure for calculating the amount of tool deformation caused by resistance during cutting according to the second embodiment. FIG. 9 is an explanatory diagram illustrating a state in which the tool T is brought into contact with the tracing stylus S from the X-axis plus direction (the direction of the arrow in FIG. 3) and a state in which the tracing stylus S is pressed. As in the first embodiment, assuming that the position data at the time of contact with the tracing stylus is X1 and the position data after pressing the tracing stylus is X2, the axial movement amount Xt in the stylus pressing process can be obtained by the following equation.

Xt = X2-X1 Assuming that the displacement amount of the tracing stylus S at this time is e and the stiffness of the tracing stylus that has been verified in advance is Ks, the tool stiffness Kt is obtained by the following equation.

Kt = Ks ・ e / Xt Then, from the tool edge rigidity Kt obtained in Equation 5, and the feed component force Fp of the cutting resistance, the tool edge deformation δ caused by cutting can be obtained by the following equation.

Δ = Fp / Kt

FIG. 10 shows a state in which the tool edge is brought into contact with the tracing stylus from the plus direction of the Z axis, and the tool rigidity Kt at this time is obtained by the following equation.

Kt = KsＫe / Zt

The tool edge detecting device mounted on a lathe and a machining center has been described with reference to the first and second embodiments. However, the tool edge detecting device of the present invention is not limited to these machine tools. Needless to say, it can be widely mounted on all NC machine tools such as boring machines. In addition to calculating the tool correction value in consideration of the tool deformation amount due to the back component force in the lathe or the feed force component in the machining center, a tool correction value in consideration of the tool deformation amount due to the main component force or the like may be calculated in the same manner. it can.

[0025]

According to the tool edge detecting device of the present invention, a tool correction value for predicting the amount of tool deformation during work can be automatically set and input. Not only does it not have to take the time and effort to re-enter the tool correction value after performing trial cutting, but also allows the machine tool to machine with extremely high dimensional accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic configuration of a tool edge detection device according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a state in which a tool edge is brought close to a tracing stylus of the tool edge detection device according to the first embodiment.

FIG. 3 is an explanatory diagram showing a state in which a tool tip is brought into contact with a tracing stylus of the tool tip detecting device according to the first embodiment, and a state in which a tracing stylus is pressed by the tool tip.

FIG. 4 is a partial vertical cross-sectional explanatory view showing a state where a part of a blade edge position contact detection unit and a tracing stylus displacement amount detection unit of the tool blade edge detection device of the first embodiment is partially cut away.

FIG. 5 is an explanatory sectional view taken along line AA of FIG. 4;

FIG. 6 is an enlarged explanatory diagram of a tracing stylus displacement amount detection unit of the tool edge detection device of the first embodiment.

FIG. 7 is a flowchart illustrating an operation procedure of the tool edge detection device according to the first embodiment.

FIG. 8 is a block diagram illustrating a basic configuration of a tool edge detection device according to a second embodiment.

FIG. 9 is an explanatory diagram showing a state in which a tool tip is brought into contact with a tracing stylus of the tool edge detecting device according to the second embodiment, and a state in which the tracing stylus is pressed by the tool tip.

FIG. 10 is an explanatory diagram illustrating a state in which a tool tip is brought into contact with a tracing stylus of the tool edge detection device according to the second embodiment from a positive Z-axis direction.

FIG. 11 is an explanatory view showing a conventional tool edge detection device.

[Explanation of symbols]

1. ·················································· Function generator, 7.
· Position control device, 8 · · · Input interface, 9 · · · Machining condition memory unit, 10 · · · cutting back force calculation unit, 11 · · ·
Cutting edge deformation calculator, 12 ・ ・ Tool correction value generator, 13 ・
· Position detector, 14 · · Servo motor, 15 · · · Turret tool post, 16 · · · Blade contact surface, 17 · · Sensor arm, 18 · · · Tool post drive shaft, 19 · · axis, 20a, 20
b ball bearing, 21 mover, 22 torsion coil spring, 23 stopper, 24a first contact,
24b... Second contact, 25... Detection switch, 26.
.Piston, 27 .. spindle, 28 .. oscillator, 29 ..
Strain gauge, 30 housing, 31 detection switch mounting part, 32 spindle head, 33 spindle, 34
・ Tool, 35 ・ ・ Cutting feed force calculator, e ・ ・ Measurement element displacement, Ks ・ ・ Measuring element rigidity, Kt ・ ・ Tool edge rigidity, S
..Measuring element, T..Tool, Tp..Tool edge, X1
Position data at the time of contact with the probe, X2 ··· Position data after pressing the probe, Xt
・ The amount of tool tip deformation.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B23Q 15/18 B23Q 17/00 B23Q 17/22

Claims (2)

(57) [Claims] 1. A tool edge detecting device mounted on an NC lathe, detecting a tool edge position of a tool attached to a tool rest of the NC lathe, calculating a tool correction value, and setting the tool correction value on the NC lathe. A tool tip position contact detection unit that detects contact with the tool tip with a contact point having a contact surface and outputs a contact detection signal, a tool tip position measurement mode that detects contact with the tool tip, and a tool rigidity measurement mode that detects tool rigidity A cutting mode generating means for executing cutting edge position data at the time of receiving the contact detection signal, and a cutting edge position detecting means for sending an axial movement amount in a stylus pressing process during tool rigidity measurement; A stylus displacement amount detection unit that detects a displacement amount of the stylus pressed by a tool in a process and outputs a displacement detection signal; and an axial movement amount and the stylus displacement amount detection in the stylus pressing process. Tool edge detecting apparatus characterized by comprising a cutting edge rigidity calculation unit for calculating a tool rigidity from the gauge the amount of displacement detected from. 2. A tool which is mounted on an NC machine tool that performs machining by attaching a tool to a spindle rotatably supported on a spindle head, detects a cutting edge position of the tool attached to the spindle of the NC machine tool, and performs tool correction. A tool edge detection device that calculates a value and sets the value on an NC machine tool, wherein the device detects a contact between the tool edge and a tracing stylus having a blade contact surface, and outputs a contact detection signal; A measurement mode generating means for executing a blade edge position measurement mode for detecting contact of the tool blade edge and a tool rigidity measurement mode for detecting tool rigidity, and outputting blade edge position data at the time of receiving the contact detection signal, and a tracing stylus for measuring tool rigidity. Cutting edge position detecting means for transmitting an axial movement amount in a pressing process; a probe displacement for detecting a displacement of the probe pressed by a tool in the probe pressing process and outputting a displacement detection signal; A tool comprising: a detecting unit; and a cutting edge rigidity calculating unit configured to calculate a tool rigidity from an axial movement amount in the stylus pressing process and a stylus displacement amount detected from the stylus displacement amount detecting unit. Cutting edge detection device.