JP2006275786A - Pointer type measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pointer type measuring instrument in which heat generation can be restrained. <P>SOLUTION: This pointer type measuring instrument is provided with a stepping motor (movable magnet type electric motor) 7 for rotation-operating a rotor 72 comprising a permanent magnet, by magnetic torque generated with supply of an excitation current to excitation coils 75, 76, a pointer 6 with a position varied in response to the rotation of the rotor 72, and a control means 8 for supplying the excitation current for operating the rotor 72, based on an input signal in response to a measuring amount, to excitation coils 75, 76, and the magnetic torque when holding the rotor 72 in a prescribed position in order to maintain the position of the pointer 6 is set to get smaller than the magnetic torque when rotation-operating the rotor 72 in order to change the position of the pointer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pointer-type instrument mounted on a moving body such as an automobile, a motorcycle, and a ship, and relates to a pointer-type instrument that uses a movable magnet type electric motor including a stepping motor as an actuator for moving the pointer.

As a pointer-type instrument using a stepping motor, for example, one described in Patent Document 1 below is known.
This pointer-type instrument rotates an annular moving member equipped with a pointer by a stepping motor, and the moving member is made of a relatively large annular gear wheel having a shape corresponding to the moving path of the pointer. The magnet-type electric motor is connected through a pinion gear and is rotatably supported through a support member such as a roller distributed around the pinion gear.
JP 2004-361183 A

  Incidentally, unlike the above-mentioned Patent Document 1, the pointer is not rotated through an annular moving member. However, as a method for driving a pointer-type instrument using a stepping motor, for example, the one described in Patent Document 2 below is known. ing.

In the patent document 2, the control means (microcomputer or motor drive circuit) for driving and controlling the stepping motor is provided, and the control angle is calculated from the previous indication angle data and the latest regarding the indication angle data sequentially calculated at predetermined intervals. The amount of change (difference) is obtained by comparing with the command angle data, a pulse signal corresponding to the number of steps corresponding to this difference is output to the stepping motor, and the pointer is rotated. As the pulse signal, It is common to use an exciting current whose period constantly changes with a constant waveform.
Japanese Patent Publication No. 5-14206

  However, since the pointer-type meter described in Patent Document 1 drives the pointer through an annular moving member that is large in volume and heavy, the load on the stepping motor is large, and the motor itself (coil) or There is concern about the heat generation of the circuit elements that drive and control this. In particular, in the case of a speedometer, a constant excitation current is continuously supplied to the stepping motor in order to maintain the pointer at a predetermined designated position during constant speed travel, and thus the amount of heat generation tends to increase. For this reason, for example, a countermeasure against heat such as devising a peripheral structure for ventilation or adopting a heat radiating element such as a heat sink or a heat radiating pattern may be required.

  The present invention has been made in view of this point, and its main object is to provide a pointer-type meter that can suppress heat generation.

In order to achieve the above object, the present invention provides a movable magnet type electric motor that rotates a rotor made of a permanent magnet by a magnetic torque generated by supplying an exciting current to an exciting coil, and a position thereof according to the rotation of the rotor. Changing guidelines,
Control means for supplying the exciting coil with the exciting current for operating the rotor based on an input signal corresponding to a measured quantity, and rotating the rotor to change the position of the pointer. The exciting current is set such that the magnetic torque when the rotor is held at a predetermined position with respect to the torque is reduced in order to maintain the position of the pointer.

  In order to achieve the above object, the present invention provides a movable magnet type motor that rotates a rotor made of a permanent magnet by a magnetic torque generated by supplying an exciting current to an exciting coil, and a position thereof according to the rotation of the rotor. The guide angle is changed, and the input signal corresponding to the measured amount is converted into the command angle data at a predetermined cycle, and the previous command angle data and the latest command angle data are compared for each cycle, and the previous command angle data When the latest command angle data changes in the increasing / decreasing direction, the excitation current for rotating the rotor so that the pointer moves to the command position corresponding to the latest command angle data based on the change amount is excited. When the first processing mode to be supplied to the coil is the same as the previous indication angle data and the latest indication angle data, the low-point direction is maintained so that the indication position of the pointer is maintained. Control means for executing the second processing mode for supplying the exciting current to the exciting coil to hold the magnet in a predetermined position, and for the magnetic torque acting on the rotor in the first processing mode, The exciting current is set so that the magnetic torque acting on the rotor is reduced in the second processing mode.

  The present invention is also characterized in that the movable magnet type motor is a claw pole type PM stepping motor including a comb-shaped yoke for guiding the magnetic field of the exciting coil to the rotor.

  Further, the present invention is characterized in that the pointer is supported by a moving member having a shape corresponding to the moving track of the pointer, and the position of the pointer is changed by moving the moving member by the movable magnet type motor. .

  According to the present invention, it is possible to provide a pointer-type meter that can achieve the initial purpose and can reduce heat generation.

  1 to 5 show an embodiment of the present invention, FIG. 1 is an exploded perspective view of a pointer-type instrument according to the present embodiment, FIG. 2 is a cross-sectional view of a stepping motor employed in the present embodiment, FIG. 3 is a block diagram showing a stepping motor drive system in the present embodiment, FIG. 4 is a flowchart showing a processing flow for operating the stepping motor in the present embodiment, and FIG. 5 is a pointer corresponding to the output waveform of the excitation current. It is a timing diagram which shows the designated angle.

  The pointer-type meter according to the present embodiment includes, for example, a speedometer for automobiles. As shown in FIG. 1, a circuit board 1, a display device 2 disposed on the circuit board 1, and the display device 2, connected to the moving member 4, a supporting member 3 disposed in front of the moving member 4, a moving member 4 supported rotatably by the supporting member 3, a display plate 5 disposed in front of the moving member 4, A pointer 6 that moves on the display board 5 along with the rotational movement, a stepping motor (movable magnet type electric motor) 7 that is arranged on the circuit board 1 together with the display device 2 and rotates the moving member 4, and the stepping motor. And a control means 8 (see FIG. 3) for controlling the operation of the display 6 and constitutes a so-called centerless meter in which the pointer 6 rotates around the outer periphery of the display information provided by the display device 2. .

  The circuit board 1 is made of, for example, a hard board, and is provided with a circuit pattern and various circuit elements (not shown) necessary for operating each element of the pointer-type instrument including the display device 2 and the stepping motor 7, as well as control means. 8 is also installed.

  The display device 2 is composed of, for example, a TFT (thin film transistor) type liquid crystal display, and includes a backlight unit (not shown) inside. The display information displayed on the display device 2 is arbitrary, but in this example, for example, the travel distance of the automobile, various alarm / notification information, and navigation information are displayed.

  The support member 3 is made of, for example, an annular synthetic resin component, and includes a first see-through portion 31 that can transmit the display surface of the display device 2 and a support portion 32 that supports the moving member 4 in the radial direction and the thrust direction. I have.

  The moving member 4 is made of, for example, an annular synthetic resin component that is accommodated and supported by the support portion 32, and corresponds to the first see-through portion 31 and is capable of transmitting the display surface of the display device 2. , A continuous tooth (gear train) 42 for connecting to the stepping motor 7 and a protrusion 43 for supporting and mounting the pointer 6 are provided.

  The display board 5 is composed of, for example, a print panel obtained by printing a synthetic resin plate, and is a target of the third see-through part 51 corresponding to the first and second see-through parts 31 and 41 and the panel pointer 6. In this case, the index portion 52 is printed so as to be light transmissive, and the background portion 53 is light-shielded. ing.

  In addition, behind the display panel 5, a first light source 5a made of, for example, an inorganic electroluminescence element panel is illuminated so as to illuminate the display panel 5 from behind. In this case, the first light source 5a is formed in a donut shape so as not to block the display surface of the display device 2.

  The pointer 6 is formed by appropriately coloring a transparent synthetic resin material extending in a rod shape, for example, and is attached to the protruding portion 43 of the moving member 4 so that the display plate 5 passes through the third see-through portion 51 of the display plate 5. 5 and moves on the display board 5 in accordance with the rotational movement of the moving member 4.

  In addition, a second light source 6 a made of, for example, a light emitting diode is disposed to face one end of the pointer 6 so that the pointer 6 emits light. The second light source 5a is covered with a light shielding cover 6b.

  The stepping motor 7 is composed of, for example, a claw pole (comb tooth) type PM stepping motor. As shown in detail in FIG. 2, a rotor 72 having a rotating shaft 71 (indicated by a one-dot chain line in the figure) and a rotor 72 Control means comprising yokes 73, 74 extending a plurality of pole teeth 731, 732, 741, 742 facing the peripheral surface, and stators A, B having exciting coils 75, 76 for magnetizing the yokes 73, 74 8, the rotor 72 is rotated by a magnetic torque generated by supplying an excitation current corresponding to the measured amount to the excitation coils 75 and 76 of the stators A and B. A pinion gear 77 that meshes with the continuous teeth 42 of the member 4 is fixed, and the rotation of the rotor 72 is transmitted to the moving member 4 via the pinion gear 77, and the pointer 6 A configuration in which moved.

Next, the control means 8 will be described with reference to FIG.
The control means 8 includes a microcomputer 81 that executes a predetermined processing program, a read-only ROM 82 that stores programs executed by the microcomputer 81 and various necessary data in advance, and a read / write function that temporarily stores necessary data. RAM 83, a current output circuit 84 for operating the stepping motor 7 by supplying a predetermined excitation current to the coils 75 and 76 of the stepping motor 7 based on a command from the microcomputer 81, and also based on a command from the microcomputer 81 The display output circuit 85 displays predetermined display information on the display device 2, and the stepping motor 7 and the display device 2 are operated based on an input signal received through the input terminal (group) 8a.

  Next, the operation control process of the stepping motor 7 by the control means 8 will be described based on FIG. In FIG. 4, it is assumed that an ignition switch (not shown) is turned on and the vehicle is already in a running state. The description of the operation control process of the display device 2 is omitted.

  That is, the control means 8 determines whether or not a measurement signal (input signal) proportional to the speed from, for example, a speed sensor or an in-vehicle communication system has been received in step S2 after step S1 that is in a standby state. In this case, the measurement signal is received continuously at a constant time interval (period).

  When the determination result in step S2 is “N (no)”, it is determined in step S3 whether or not the switch is off based on whether or not an off signal from the ignition switch is received. Is “Y (yes)”, the process is terminated. If “N (no)”, the process returns to step S1 and again waits.

  When the determination result in step S2 is “Y”, in step S4, the received (latest) measurement signal is arithmetically processed according to a predetermined program and converted to the latest indication angle data SP (t).

  In the subsequent step S5, the previous instruction angle data (instruction angle data obtained one cycle ago) SP (t-1) is read from the RAM 83, and in the subsequent step S6, the previous instruction angle data SP (t-1) is read. The latest indication angle data SP (t) is compared. Here, the change amount (difference) of the latest indication angle data SP (t) with respect to the previous indication angle data SP (t−1) is “0”. It is determined whether or not the previous instruction angle data SP (t-1) is equal to the latest instruction angle data SP (t).

  When the determination result of step S6 is N, that is, when the latest instruction angle data SP (t) has changed in either the increasing direction or the decreasing direction with respect to the previous instruction angle data SP (t-1), the process proceeds to step S7. Thus, the difference value of the latest indication angle data SP (t) with respect to the indication angle data SP (t−1) is converted into the step number n, and the current waveform data corresponding to the step number n converted in the subsequent step S8 is stored in the ROM. In step S9, the excitation current corresponding to the current waveform data is output through the current output circuit 84 as an excitation current (described later) based on the first processing mode.

  As a result, magnetic torque is generated in the exciting coils 75 and 76 of the stepping motor 7 to rotate the rotor 72 by the required number n of steps in order to change the pointer 6 toward a new position. Is rotated by the required angle or number of rotations, and the position of the pointer 6 is changed in conjunction with this rotation operation.

  After completion of step S9, the process returns to step S1 via step S12. In step S12, the instruction angle data SP (t) that has been updated so far is used to calculate the instruction angle in the next cycle (step S4). The process of updating as the previous instruction angle data SP (t-1) is performed.

  If the determination result in step S6 is Y, that is, if the change amount (difference) in the latest instruction angle data SP (t) with respect to the previous instruction angle data SP (t−1) is “0”, the process proceeds to step S10. Current waveform data corresponding to the step number n = 0 is read from the waveform pattern table stored in the ROM. In step S11, the excitation current corresponding to the current waveform data is based on the second processing mode. An exciting current (described later) is output through the current output circuit 84.

  As a result, magnetic torque is generated in the exciting coils 75 and 76 of the stepping motor 7 so as to hold the rotor 72 at a predetermined rotational position in order to maintain the pointer 6 at a predetermined position. While being held, the pointer 6 also maintains a predetermined indicated position.

  And after completion | finish of step S11, it returns to step S1 via step S12, but the processing content of step S12 is as above-mentioned.

  Next, the relationship between the output waveform of the excitation current and the pointing angle of the pointer will be described with reference to FIG.

  In FIG. 5, the excitation current waveform in the present embodiment corresponds to the excitation pattern of the 1-2 phase excitation bipolar system, and the times t0 to t4 indicate one output cycle section of the excitation current.

  First, in the output cycle from time t0 to t1, the excitation current based on the processing from step S7 to step S9 in FIG. 4 is output. That is, in step S7, the number of steps is converted to n = “5”, and based on the conversion result of “5”, a current waveform pattern of a pattern “tn−2” is read out in step S8, and this waveform pattern is supported. By outputting the exciting current in step S9, the position of the pointer 6 is changed in the increasing direction by 5 steps.

  In the subsequent output cycle from time t1 to time t2, the excitation current based on the processing from step S10 to step S11 in FIG. 4 is output. That is, in step S10, the current waveform pattern of the pattern “tn−1” is read based on the number of steps n = “0”, and the excitation current corresponding to this waveform pattern is output in step S11. It is kept in place.

  In the subsequent output period from time t2 to time t3, the excitation current based on the processing from step S7 to step S9 in FIG. 4 is output. That is, in step S7, the number of steps n = “− 3” is converted, and based on the conversion result “−3”, the current waveform pattern of the pattern “tn” is read out in step S8, and this waveform pattern is supported. By outputting the exciting current in step S9, the position of the pointer 6 is changed in the decreasing direction by three steps.

  In the subsequent output cycle from time t3 to t4, the excitation current based on the processing from step S10 to step S11 in FIG. 4 is output. That is, in step S10, a current waveform pattern having a pattern of “tn + 1” is read based on the number of steps n = “0”, and an excitation current corresponding to this waveform pattern is output in step S11. Is maintained.

  Here, the excitation current waveform in the output period of time t0 to t1 and time t2 to t3 when the position of the pointer 6 changes, and the output of time t1 to t2 and time t3 to t4 where the position of the pointer 6 is maintained without changing. Comparing with the excitation current waveform in the period, the excitation current having the normal value is used in the output period of time t0 to t1 and time t2 to t3, and the excitation current output based on this normal value is shown in step S9 in FIG. In the first processing mode, the excitation current output process is performed. On the other hand, in the output period from time t1 to t2 and from time t3 to t4, the value (absolute value) of the excitation current decreases from the normal value indicated by the dotted line. The value corrected (current limited) so as to be (smaller) is used, and the excitation current output based on this correction value is the excitation current output in the second processing mode of step S11 in FIG.

  In addition, the correction of the excitation current value in the output cycle from time t1 to t2 and from time t3 to t4 is performed so that the value (absolute value) of the excitation current becomes small during the output cycle from time t1 to t2 and from time t3 to t4. Is a value obtained by multiplying the normal value indicated by a predetermined coefficient (positive pure decimal). It should be noted that the excitation current flowing to the excitation coil 76 side from time t3 to t4 is equal to the normal value because the normal value is “0” (0 × coefficient = 0).

  Thus, when the position of the pointer 6 is maintained without changing, the magnetic torque is reduced using the correction value that is current-limited so that the value of the excitation current becomes small, and the position of the pointer 6 changes. By using a normal value (value that is not corrected) and making it larger than when the pointer 6 position is maintained, current consumption can be reduced compared to the case of driving using the normal value at all times. Can suppress heat generation.

  By using a correction value in which the current is limited so that the value of the excitation current is small, the magnetic torque acting on the rotor 72 is small compared to the case of using a normal value (a value that is not corrected). Is not required to be as large as when the position of the pointer 6 is changed, and it is sufficient if a magnetic torque sufficient to maintain the pointer 6 at a predetermined position is obtained.

  As described above, in the present embodiment, the stepping motor (movable magnet type motor) 7 that rotates the rotor 72 made of a permanent magnet by the magnetic torque generated by supplying the exciting current to the exciting coils 75 and 76, and the rotor 72 And a control means 8 for supplying an exciting current for operating the rotor 72 to the exciting coils 75 and 76 based on an input signal corresponding to the measured amount. The excitation current is set so that the magnetic torque when the rotor 72 is held at a predetermined position in order to maintain the position of the pointer 6 is smaller than the magnetic torque when the rotor 72 is rotated to change the position. As a result, heat generation can be suppressed.

  That is, in the present embodiment, the control means 8 converts the input signal according to the measurement amount into the instruction angle data at a predetermined period and compares the previous instruction angle data with the latest instruction angle data for each period, When the latest command angle data changes in the increase / decrease direction with respect to the previous command angle data, excitation is performed to rotate the rotor 72 so that the pointer 6 is directed to the command position corresponding to the latest command angle data based on the change amount. When the first processing mode S9 in which current is supplied to the exciting coils 75 and 76 and the previous instruction angle data and the latest instruction angle data are equal, the rotor 72 is moved to a predetermined position so that the indicated position of the pointer 6 is maintained. The second processing mode S11 for supplying the exciting current to be held to the exciting coils 75 and 76 is executed, and the second torque is applied to the magnetic torque acting on the rotor 72 in the first processing mode S9. By setting the excitation current so that the magnetic torque is reduced acting on the rotor 72 in the sense mode S11, it is possible to suppress heat generation.

  The present invention is particularly useful when a claw-pole PM stepping motor that easily generates heat is used as the movable magnet type electric motor.

  Further, according to the present invention, the pointer 6 is supported by the moving member 4 having a shape corresponding to the moving track, and the stepping motor moves the moving member 4 to change the position of the pointer 6 to easily generate heat. Is particularly useful when applied to,

  In the present embodiment, the moving member 4 is formed of a dimensionally stable synthetic resin material. However, the moving member 4 may be formed of a flexible member, and the movement locus of the pointer 6 may be freely changed.

  In the present embodiment, a claw pole PM type stepping motor is used as the movable magnet type motor. However, the type is arbitrary as long as it is a movable magnet type motor.

  In the present embodiment, the excitation current waveform shown in FIG. 5 is used. However, the excitation current waveform is arbitrary depending on the type and type of the movable magnet type motor, and the excitation current changes the position of the pointer 6 to the rotor 72. The magnetic torque when the rotor 72 is held at a predetermined position in order to maintain the position of the pointer 6 may be set to be small with respect to the magnetic torque when rotating the.

The disassembled perspective view of the pointer type meter by one Embodiment of this invention. Sectional drawing of the stepping motor employ | adopted in this embodiment. The block diagram which shows the drive system of the stepping motor in this embodiment. The flowchart figure which shows the processing flow for operating the stepping motor in this embodiment. The timing diagram which shows the indication angle of the pointer | guide corresponding to the output waveform of an exciting current.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Display apparatus 3 Support member 4 Moving member 5 Display board 5a 1st light source 6 Pointer 6a 2nd light source 6b Light-shielding cover 7 Stepping motor 8 Control means 31 1st see-through | perspective part 32 Support part 41 2nd See-through part 42 Continuous teeth (gear train)
43 Projection portion 51 Third perspective portion 52 Index portion 53 Background portion 71 Rotating shaft 72 Rotor 73, 74 Yoke 75, 76 Excitation coil 77 Pinion gear 81 Microcomputer 82 ROM
83 RAM
84 Current output circuit 85 Display output circuit 731, 732, 741, 742 Polar teeth A, B Stator

Claims (4)

A movable magnet type electric motor that rotates a rotor made of a permanent magnet by a magnetic torque generated by supplying an exciting current to an exciting coil;
A pointer whose position changes according to the rotation of the rotor;
Control means for supplying the exciting current to the exciting coil for operating the rotor based on an input signal corresponding to a measurement amount;
The magnetic torque when the rotor is held at a predetermined position in order to maintain the position of the pointer is smaller than the magnetic torque when the rotor is rotated to change the position of the pointer. A pointer-type meter characterized in that the exciting current is set in A movable magnet type electric motor that rotates a rotor made of a permanent magnet by a magnetic torque generated by supplying an exciting current to an exciting coil;
A pointer whose position changes according to the rotation of the rotor;
The input signal corresponding to the measurement amount is converted into the command angle data at a predetermined cycle, and the previous command angle data and the latest command angle data are compared for each cycle, and the latest command angle data is compared with the latest command angle data. When the angle data changes in the increase / decrease direction, a first current is supplied to the excitation coil that rotates the rotor so that the pointer is directed to the indicated position corresponding to the latest indicated angle data based on the change amount. When the processing mode is equal to the previous indication angle data and the latest indication angle data, the excitation current for holding the rotor in a predetermined position is supplied to the excitation coil so that the indication position of the pointer is maintained. Control means for executing the second processing mode,
The pointer type wherein the exciting current is set so that the magnetic torque acting on the rotor in the second processing mode is smaller than the magnetic torque acting on the rotor in the first processing mode. Instrument. 3. The pointer-type meter according to claim 1, wherein the movable magnet type electric motor is a claw pole type PM stepping motor including a comb-shaped yoke for guiding a magnetic field of the exciting coil to the rotor. 2. The pointer according to claim 1, wherein the pointer is supported by a moving member having a shape corresponding to a moving track of the pointer, and the position of the pointer is changed by moving the moving member by the movable magnet type motor. Item 2. A pointer-type instrument according to item 2.

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