Rotation detection device in an eddy current type velocity meter

Abstract

We provide highly reliable add-on speed detection devices without requiring large manufacturing facilities. [Solution] A magnetic detection element for detecting the magnetic flux of the rotating magnet of an eddy current speedometer is mounted on a substrate, and the substrate is mechanically fixed to a metal holding member. Furthermore, the conversion element, substrate, metal holding member, and mechanical fixing means and substrate are connected by soldering to reinforce against rotation, loosening, and play. Sensitivity can also be adjusted by the plastic deformation of the mounting metal, and by using the metal holding member as an electrically conductive part, a simple, compact, and highly reliable retrofit speed detection device can be realized.

Description

[Technical Field]

[0001] The present invention relates to a speed detecting device that is retrofitted to an eddy-current type instrument. [Background Art]

[0002] In an eddy-current type instrument, the rotational motion of a wheel or drive shaft mounted on a vehicle via a flexible cable is transmitted to a magnet provided on a rotating shaft in the instrument. The instrument is provided with an induction rotor disposed in the magnetic circuit of the magnet and biased to a zero position by a spiral spring, and configured to display speed via a pointer coupled to the induction rotor which is rotationally displaced by an eddy current effect generated by rotation of the magnet. A conventional rotation detecting device for an eddy-current type speedometer, as described in Patent Document 1, is known to have a magnetic detecting element attached thereto. This instrument comprises a speed detecting device that detects a magnetic field change caused by rotation of the magnet by a magnetoelectric converting element such as a Hall element, and activates an alarm when the vehicle speed exceeds a predetermined value. Furthermore, a retaining device is arranged on a mounting screw of the detecting device to improve reliability. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-112259 [Patent Document 2] Japanese Utility Model Laid-Open Publication No. 63-88752 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 08-133107 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the conventional eddy current type instrument described in Patent Document 1, the velocity detection device has a three-dimensional structure with volume called a sensor support block attached to the frame of the meter device with special mounting bolts. However, in this structure, manufacturing a three-dimensional structure with volume requires creating a mold, sealing it with resin, carving a three-dimensional structure from a larger solid, or preparing a 3D printer. Furthermore, since such a structure is made of insulating material, it is made of relatively soft material, and the parts subjected to stress due to repeated thermal activity change shape, making the mounting bolts prone to loosening. In the conventional eddy current type instrument described in Patent Document 2, the Hall element is attached to the support member of the meter device integrally with the substrate via an insulating case, and the substrate and case are made of relatively soft material, so the parts subjected to stress due to repeated thermal activity change shape, making the mounting bolts prone to loosening.

[0005] Therefore, common methods to prevent bolts from falling out or loosening include attaching a retaining washer to the bolt point or installing a loosening prevention wall just before the bolt comes out completely. However, the deformation of the resin insulator is large, so prolonged thermal cycles can lead to insufficient support and further loosening. While loosening stoppers can prevent the bolt from falling out, they cannot completely prevent rattle.

[0006] Furthermore, when retrofitting a speed detection device, the device is attached to an existing eddy current type instrument during use. However, due to the deterioration of the permanent magnet and variations in the newly installed magnetoelectric conversion element, adjustment is necessary after assembly. However, in the case of a type where the insulating block is screwed in, as in the embodiment of Patent Document 1, while sliding may be possible due to the elongated holes and increased play, adjusting the air gap is not only difficult, but the stress around the mounting bolts becomes high, leading to durability problems. In the embodiment of Patent Document 2, the bolt mounting points for adjustment are elongated holes in the figure, and again, the stress on the substrate mounting is high, leading to durability problems. [Means for solving the problem]

[0007] In this invention, a speed detection device for an eddy current type instrument equipped with a magnet rotor that rotates together with the main shaft has a magnetic detection element placed in the rotating magnetic field generated by the magnet rotor to detect rotation. The device includes a circuit board to which the magnetic detection element is connected, and the circuit board is fixed to a metal support member formed by bending a plate using screws. The magnetic detection element is supported and fixed by the frame by fixing a metal holding member to the frame band with screws. Furthermore, the structure allows for the retrofitting of the speed detection device section without requiring extensive disassembly.

[0008] Furthermore, the metal holding member is designed to reduce the rigidity of the magnetic detection element in the air gap direction relative to the magnetic circuit, allowing for plastic deformation.

[0009] Furthermore, the circuit board is soldered to the screws that secure it to the support member, integrating it with the metal component. At this time, the screws are placed on the grounding electrode pattern of the magnetic detection element and soldered, thus also serving as the grounding wire.

[0010] Furthermore, the circuit board is designed with patterns on both sides, and soldering is performed directly between the back of the pattern and the metal component at locations other than screws. [Effects of the Invention]

[0011] According to the present invention, the rotation of screws that fasten the substrate, which is a resin component that collapses and deforms due to thermal cycles over time under stress on the fixing means, can be suppressed to prevent loosening or falling off even if the axial force decreases. Since the substrate can be directly soldered to the metal support member, even if the substrate deforms, movement and vibration of the detection part due to vibration can be prevented. Since the support member is made of copper metal plate material that is easy to solder, plastic deformation is also easy, and the distance between the magnetic detection element and the induction rotor and magnet rotor can be adjusted after assembly. The metal plate material that is easy to solder is made of soft metal such as copper or brass, even for small-scale production, so processing work can be done with metal shears, punches, knives, etc., and it can also be bent by hand, so large equipment and molds for manufacturing are not required. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Figure 1] Longitudinal sectional view of an eddy current type instrument fitted with a retrofitted signal generator according to the first embodiment [Figure 2] Cross-sectional view of an eddy current type instrument fitted with a retrofitted signal generator according to the first embodiment [Figure 3] Single retrofitted signal generator according to the first embodiment [Figure 4] Developed view of the metal holding device of the retrofitted signal generator according to the first embodiment [Figure 5] Print pattern on the magnetic detection element mounting side of the circuit board of the retrofitted signal generator according to the first embodiment [Figure 6] Print pattern on the back side opposite to the magnetic detection element mounting side of the circuit board of the retrofitted signal generator according to the first embodiment [Figure 7] Longitudinal sectional view according to the second embodiment [Figure 8] Cross-sectional view according to the second embodiment [Figure 9] Developed view of the sensor support member according to the second embodiment [Figure 10] Operation diagram when the number of magnet pole pairs is 2, only one Hall IC is installed, and the Hall IC has bipolar latch characteristics. [Figure 11] Internal block diagram of a general Hall IC [Figure 12] Characteristic diagram of a Hall IC having bipolar latch characteristics [Figure 13] Operation diagram when the number of magnet pole pairs is 2, only one Hall IC is installed, and the Hall IC has omnipolar (active high) characteristics. [Figure 14] Characteristic diagram of a Hall IC having omnipolar (active high) characteristics [Figure 15] Operation diagram when the number of magnet pole pairs is 1, two Hall ICs are installed, and the Hall ICs have omnipolar (active high) characteristics. [Figure 16]An operation diagram when the Hall IC installed in two units with one magnet pole pair has omnipolar (active low) characteristics. [Figure 17] Characteristic diagram of a Hall IC with omnipolar (active low) characteristics [Figure 18] Outline of signal processing device [Figure 19] Schematic outline diagram of an electric power steering equipped with a signal processing device [Figure 20] Operation characteristics of an electric power steering equipped with a signal processing device and controlled by doubled pulses [Figure 21] Operation characteristics of an electric power steering equipped with a signal processing device and controlled by standard pulses [Figure 22] Operation characteristics of an electric power steering equipped with a signal processing device and controlled by half pulses [Figure 23] Operation characteristics of an electric power steering equipped with a signal processing device and controlled by quarter pulses

Mode for Carrying Out the Invention

[0013] Hereinafter, a first embodiment of a speed detection device for an eddy current type meter according to the present invention will be specifically described with reference to the accompanying FIGS. 1, 2, 3, 4, 5 and 6.

[0014] The eddy current type meter C of the present embodiment is composed of a main shaft, a magnet rotor, an induction rotor, a pointer, a pointer shaft, and a frame body. The retrofitted speed detection device W is composed of a magnetic detection element, a circuit board, a support member, and mounting screws 9i. The speed detection device W is fixed to the eddy current type meter C with screws 10.

[0015] The main shaft 1 transmits rotation of vehicle wheels and a drive shaft, which is transmitted via a flexible cable (not shown), to the magnet rotor 2. The main shaft 1 is rotatably supported by a cylindrical body 1a on a bottom wall of the frame body 6, which will be described later.

[0016] The magnetic rotor 2 consists of a magnet 2a and a cup-shaped soft magnetic cover 2b facing the magnet 2a. The magnetic rotor 2 is fixed to the end of the main shaft 1.

[0017] The cup-shaped induction rotor 3 is positioned with an air gap between it and the radially circular gap created by the magnet 2a and cover 2b of the magnet rotor 2. The induction rotor 3 rotates due to the eddy current action generated by the rotation of the magnet rotor 2, and generates rotational torque proportional to the rotational speed of the magnet rotor 2. A pointer shaft 5 for mounting the pointer 4 is provided at the center of the induction rotor 3.

[0018] The pointer 4 is press-fitted and fixed to the end of the pointer shaft 5, and rotates together with the pointer shaft 5 mounted on the induction rotor 3 to display the vehicle's speed.

[0019] The pointer shaft 5 is supported by a plate 6c, described later, mounted on the frame 6, and by a bearing 13 on this plate and a lower bearing 1c located at the center of the upper end of the main shaft 1. The inner end of the whisker spring 11 is fixed below the center of the pointer shaft 5, and the outer end of the whisker spring 11 is fixed to a whisker holder 12 provided on the plate 6c.

[0020] The induction rotor 3 is made of a cup-shaped conductive metal (such as a copper plate) and rotates by generating an inductive force, but it has a rotation-stopping projection 15 when the vehicle speed is zero. The projection 15 of the rotor 3 is at the same radius as the stopper 14 extending from the plate 6c in the direction of rotation, and as shown in Figure 2, when the vehicle speed is zero, the projection 15 of the rotor 3 is in contact with the stopper 14 due to the rotational force of the wick spring. As the vehicle speed increases, the projection 15 rotates clockwise together with the induction rotor 3.

[0021] The frame 6 is made of a metal material such as cold-rolled steel sheet (e.g., SPCC), has a roughly U-shaped cross-section with two side walls 6a and a bottom wall 6b, and a plate 6c is installed on the upper ends of the two side walls 6a. The frame 6 holds the various components such as the main shaft 1, magnet rotor 2, and guide rotor 3.

[0022] The magnetic detection element 7 is positioned opposite the upper surface of the induction rotor 3, and is located almost next to the stopper 14 of the induction rotor 3, on the opposite side of the direction of rotation of the projection 15, so as to be able to detect the magnetic flux of the magnet 2 that has leaked out after penetrating the induction rotor 3. The magnetic detection element 7 is soldered and held in place on a circuit board 8 which is fixed with screws 9i to a support member 9b protruding from the side wall 6a.

[0023] Since the projection 15 on the induction rotor 3 does not rotate to the installation position of the magnetic detection element 7, the magnetic detection element 7 does not interfere with the rotation of the speed indicator on the indicator shaft 5. As a result, the magnetic detection element 7 detects the change in the magnetic field accompanying the rotation of the magnet rotor 2 across the entire speed range, converts this change in the magnetic field into an electrical signal, and outputs this electrical signal to various control devices mounted on the vehicle.

[0024] The circuit board 8 has the magnetic detection element 7 soldered to its surface pattern. Furthermore, the magnetic detection element 7 is reinforced and protected together with the circuit board 8 by resin podging 8a. Electronic components such as resistors and capacitors (not shown) that protect the magnetic detection element 7 from external noise may also be mounted. It is connected to the control equipment installed on the vehicle via electrical cords (not shown). The circuit board 8 is fixed to the support member 9 by screws 9i.

[0025] The support member 9 consists of a base portion 9a and an arm piece 9b that penetrates the hole 6d in the side wall 6a from the base portion 9a. The base portion 9a is fixed to the side wall 6a of the frame 6 with two screws 10. After fixing, the screws 10 are soldered to the base portion 9a or secured with spring washers or the like to prevent rotation. Since the tightening members for these screws do not contain any soft materials such as resin, normal anti-loosening measures can be applied.

[0026] The double-sided patterned circuit board 8 is fixed to the arm piece 9b by a screw 9i. After tightening, the head of the screw 9i is soldered 8b to the front side pattern of the circuit board. Solder 8c is also made to the opposite back side pattern of the circuit board, where the components are attached, and to the arm piece 9b.

[0027] Next, a second embodiment of the velocity detection device in the eddy current type instrument according to the present invention will be specifically described with reference to the attached Figures 7, 8, and 9.

[0028] The eddy current meter C2 of the second embodiment consists of a main shaft 21, a magnet rotor 22, an induction rotor 23, a pointer 24, a pointer shaft 25, a frame 26, and an external housing 26o. The speed detection device W2 consists of a circuit board 28 on which a magnetic detection element 27 is mounted, and a metal support member 29. The circuit board 28 is formed by bonding a circuit board 28a, on which the magnetic detection element 27 is surface-mounted, to a circuit board 28b using soldering and bonding. This is a two-stage structure due to the fine pitch of the connection wires of the surface-mounted Hall IC 27 and the ease of assembling the board. Of course, it is also possible to do this with a single printed circuit board. The circuit board 28b is fixed to the support member 29 by tightening screws 29i and nuts 29j. The screws 29i are soldered 28d after tightening. The nuts 29j are soldered 29d to the support member 29 and become one. The circuit board 28 is soldered 28c to the metal support member 29. The speed detection device W2 has a structure in which the support member 29 is fixed to the frame 26 and the external housing 26o by being sandwiched between two screws 210.

[0029] The support member 29 is made of a copper plate in the unfolded shape shown in Figure 9 and has a three-dimensional structure with bent edges. The bent edges are soldered 26h to the tangents of adjacent edges to give the structure rigidity. The central hole of the support member 29 is designed to fit snugly into the part that supports the main shaft at the center of the frame 26, and is centered with respect to the main shaft. In addition, the angle of the support member 29 is uniquely determined in relation to the frame 26 by the positions of the two mounting screw holes 210.

[0030] The main shaft 21 transmits the rotation of the vehicle's wheels and drive shafts, which are transmitted via a flexible cable (not shown), to the magnet rotor 22. The main shaft 21 is rotatably supported on the frame 26.

[0031] The magnetic rotor 22 consists of a magnet 22a and a soft magnetic holder 22b for the magnet 22a. The magnetic rotor 22 is fixed to the end of the main shaft 21.

[0032] The induction rotor 23 is a cup-shaped conductor. It is positioned with a small gap between it and the magnet 22a of the magnet rotor 22. The induction rotor 23 rotates due to the eddy current action generated by the rotation of the magnet rotor 22, and generates rotational torque proportional to the rotational speed of the magnet rotor 22. A pointer shaft 25 for mounting the pointer 24 is provided at the center of the induction rotor 23.

[0033] The pointer 24 is press-fitted and fixed to the end of the pointer shaft 25, and rotates together with the pointer shaft 25 mounted on the induction rotor 23 to display the vehicle's speed.

[0034] A plate 26c is mounted on the frame 26 and secured with screws. The pointer shaft 25 is supported by a bearing 213 on this plate and a lower bearing 21c located at the center of the upper end of the main shaft 21. The inner end of the whisker spring 211 is fixed above the center of the pointer shaft 25, and its outer end is fixed to the plate 26c.

[0035] The frame 26 is made of a metal material such as aluminum, and a plate 26c is mounted on its upper end. The frame 26 holds various components such as the main shaft 21, the magnet rotor 22, and the induction rotor 23.

[0036] The magnetic detection element 27 is positioned opposite the side of the induction rotor 23 and is fixed to a circuit board 28 which is fixed to a support member 29, so as to detect the magnetic flux of the magnet 22 that leaks out after penetrating the induction rotor 23. As shown in Figure 8, two sets of this combination are installed with a 90-degree phase difference. The magnetic detection element 27 detects the change in the magnetic field accompanying the rotation of the magnet rotor 22, converts this change in the magnetic field into an electrical signal, and outputs this electrical signal to various control devices mounted on the vehicle.

[0037] In the diagram, two magnetic detection elements 27 are set up with a 90-degree phase difference, but of course, a rotation signal can be obtained with just one. Other electronic components, such as diodes and resistors or capacitors (not shown) that protect the magnetic detection elements 27 from external noise, may also be mounted. The control equipment is connected via electrical wiring (not shown). The circuit board 28 is fixed to the support member 29 by screws 29i. In this case, the ground wire is connected to the external housing 26o through the screw portion and the support member 29, thereby supplying power to the vehicle body. This eliminates the need for a separate ground wire within the narrow meter area and also ensures highly reliable power supply.

[0038] Next, the operation of the first embodiment will be described. Figure 12 shows the operation diagram of the Hall IC. In the case of bipolar latch characteristics (S pole active Lo), when the magnetic flux changes from N to S, the output of the Hall IC becomes low resistance and current flows, making it a type of Hall element.

[0039] Figure 11 shows an internal block diagram of a typical Hall IC. In this type, the drain of the final stage FET is open for output. It is known that the plate that obtains the Hall effect in the magnetic detection section of a Hall IC is generally very small and therefore has little effect on the original magnetic circuit.

[0040] Figure 10 illustrates the operation of the circuit. The Hall element in this circuit has the characteristics shown in Figure 12. When the magnet rotor rotates clockwise from the position shown in the figure, the current turns off and the voltage rises when S→N moves. Next, the current turns on when N→S moves and the voltage falls. The current turns off when S→N moves and the voltage rises. Next, the current turns on when N→S moves and the voltage falls. In this way, with a two-pole pair magnet rotor, two pulses of signal are obtained per rotation.

[0041] Next, as shown in Figure 14, consider the case of an omnipolar (active high) characteristic. This is a type of Hall IC where the output resistance of the Hall IC becomes high and the output voltage increases when the magnetic flux changes from 0 to S (or N).

[0042] The Hall IC in the circuit shown in Figure 13 has an omnipolar (active high) characteristic. When the rotor rotates clockwise from the position shown in the figure, the current is turned off at the N and S magnetic poles, causing the voltage to rise. The current is turned on between the S and N poles, causing the voltage to fall. In this way, with a two-pole magnetic rotor, four pulses of signal are obtained per rotation.

[0043] By setting different types of Hall ICs, which are magnetic detection elements 7 and 27 that are mounted on the add-on signal generators W and W2, the fineness of rotation detection can be changed without modifying the eddy current type instrument C and C2 main body.

[0044] Next, we will explain the operation in the case of a second embodiment where the number of pole pairs of the magnet rotor 23 is 1 and there are two magnetic detection elements 27. Figure 15 shows two omnipolar Hall ICs (active high) from Figure 14, installed with a 90-degree phase difference. The output of this IC is a pulled-up FET transistor circuit, and when it approaches a magnetic pole (S, N), it switches OFF (resistance increases) and the output voltage rises. As the S pole approaches the upper Hall IC Q1, it switches OFF (resistance increases) and the voltage rises. At this time, Q2, which is 90 degrees behind in phase, is still switched ON (resistance zero) and the voltage is zero. After the S pole passes in front of Q1, Q1 switches ON (resistance zero) and the output voltage becomes zero. Then, when the S pole comes in front of Q2, Q2 switches OFF (resistance increases) and the output voltage rises. After the S pole passes in front of Q2, Q2 switches ON (resistance zero) and the output voltage becomes zero. The same operation is repeated for the N pole, and the voltage characteristics shown in the chart appear in each output circuit. By using a diode to suppress reverse current, the summed voltage waveform is obtained as the output. Therefore, a single-pole pair magnetic rotor can produce 4 pulses of signal per rotation.

[0045] Next, we will explain the operation of an omnipolar IC with different electrical characteristics, specifically when the magnet rotor 23 has one pole pair and two magnetic detection elements 27. Figure 17 shows the characteristics of an omnipolar Hall IC (active low). When this IC approaches a magnetic pole (S, N), the output switches ON, the internal resistance decreases, and the output voltage drops. When the magnetic flux density is near zero, the switch turns OFF and the voltage rises.

[0046] Figure 16 shows two omnipolar Hall ICs (active low) placed 90 degrees apart. As the south pole approaches the upper Hall IC Q1, it switches ON (resistance drops). At this time, Q2, which is 90 degrees behind, is still switched OFF. After the south pole passes in front of Q1, Q1 switches OFF and the voltage rises. Then, when the south pole approaches Q2, Q2 switches ON (resistance drops). After the south pole passes in front of Q2, Q2 switches OFF and the voltage rises. The same operation repeats for the north pole, and the voltage characteristics shown in the chart appear in each output circuit. Originally, the resistance drops and current flows only when the pull-up is ON, so even if the two switching elements are placed in parallel, there is no interference in operation. As a result, the circuit can be built with fewer components such as diodes.

[0047] Back when cable-driven eddy current type instruments were common, it was typical to use two pulses per revolution for engine control and power steering control. This was because the magnetic detection element was a reed switch, and a large span of the reed switch was required for magnetic detection. To increase the span, it was necessary to make the ends of the magnetic rotor a single pole pair of S and N to ensure reliable operation of the reed switch.

[0048] It is possible to install an additional speed detection device on an eddy current type instrument that already has a speed detection device that generates vehicle speed pulses. In this case, a separate vehicle speed signal can be sent to an aftermarket trip meter, car navigation system, and power steering system. This can be added without affecting the original speed detection device, engine, or transmission electronic control, and without compromising reliability.

[0049] We previously explained that the number of pulses per revolution can be changed by the type and number of semiconductors attached to the speedometer. Next, we will show a system that switches the number of generated pulses by electrical circuit processing of the obtained rotational pulses. Figure 18 shows the signal processing device 30. The input signal is input to the 1 / 2 frequency divider 31 through the buffer 32. The frequency divider 31 is composed of flip-flop circuits. It has a total of three stages and can extract four types of signals. When a signal of 4 pulses per revolution from the magnet rotors 2,22 is input, four types of signals can be obtained per revolution: 4, 2, 1, and 1 / 2. A final stage 34 is provided at the output of a switch 33 that can select each of these signals. As mentioned above, if the signal from the reference vehicle speed sensor is 2 pulses per revolution, it will be converted to 2 times, 1 / 2 times, and 1 / 4 times. The signal can also be selected by the switch 33.

[0050] As shown in Figure 4 of Patent Document 3, in electric power steering, the amount of power steering assist changes depending on the vehicle speed. Therefore, by taking a relatively large number of pulses from the vehicle speed sensor and then switching the pulse generation ratio using the signal processing device 30, the amount of power steering assist can be switched.

[0051] Figure 19 shows a configuration in which a speedometer with a speed detection device and a signal processing device 30 are incorporated into a typical electric power steering system. In electric power steering, the ignition signal indicates whether the ignition is ON, the engine signal indicates whether the vehicle is in operation, the steering torque is detected by a torque detector, and the vehicle speed is detected by the speed detection device. The signal processing device 30 is inserted into this vehicle speed signal path.

[0052] The Calculation Control Unit (ECU) calculates the amount of assist from torque and vehicle speed using the map shown in Figure 21, which represents 2 pulses per revolution (the standard pulse count), and drives the motor. If the toggle switch is set to 4 pulses per revolution (double the pulse count ratio) and the vehicle speed signal is provided to the ECU, the steering becomes lighter when turning, but once moving, it becomes heavier with less assist and a more direct feel, as shown in Figure 20. Conversely, if the switch is set to 1 pulse per revolution (half the pulse count ratio) as shown in Figure 22, or 1 / 2 pulses per revolution (quarter the pulse count) as shown in Figure 23, a lighter torque performance is obtained across the entire range. The driver can adjust the weight of the power steering according to their preference and the situation.

[0053] As described above, this aftermarket vehicle speed signal generator does not require large production facilities, enhances the mechanical reliability of the assembly, absorbs product variations in the elements, and can achieve an output signal that is optimal for the control system being used. [Explanation of symbols]

[0054] 1 21 Spindle 2 22 Magnet Rotor 3 23 Induction Rotor 4 24 Guidelines 5 25 Pointer shaft 6 26 Frame 7 27 Magnetic detection element 8 28 Circuit board 9 29 Support Member 10 210 volts C C2 Eddy Current Meter W W2 Speed ​​Detection Device

Claims

1. A rotation detection device for measuring rotational magnetic flux by adding one or more magnetic detection elements to the eddy current instrument, comprising a rotating magnet on a rotating shaft, an induction rotor which generates eddy currents due to the rotational magnetic flux of the rotating magnet and generates rotational torque proportional to the rotational speed of the rotating shaft, and a pointer shaft driven by the rotation of the induction rotor, wherein the rotation detection device comprises a metal holding member attached to the frame of the eddy current instrument, an electronic circuit board member mounted on the metal holding member by a mechanical coupling structure, magnetic detection elements soldered to the electronic circuit board member, and the connections between each of the assembly members, i.e., the metal holding member and the mechanical coupling structure, the mechanical coupling structure and the electronic circuit board, or the metal holding member and the electronic circuit board, are reinforced by soldering to prevent loosening and movement.

2. A rotation detection device configured in claim 1, wherein the air gap between the magnetic detection element and the rotating magnet can be adjusted by deforming a part of the structure of the metal holding member.

3. The rotation detection device according to claim 1, wherein the metal holding member is made of a metal containing a majority of copper, such as copper or brass, and can be easily soldered, and this metal plate is part of an electrical circuit.

4. A rotation detection device according to claim 1, wherein the metal holding member is made of a metal containing a majority of copper, such as copper or brass, and can be easily soldered, and the three-dimensional structure of the metal holding member can be maintained by bending and soldering this metal plate.

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