JP6989305B2 - Circuit board and motor controller - Google Patents

Description

The present invention relates to a circuit board provided with a current detection unit that detects potentials at both ends of a resistance element and detects a current, and a motor control device provided with the circuit board.

A current detection unit is used in which a current is passed through a resistance element inserted in series with a circuit on a circuit board, and the potentials at both ends of the resistance element are detected to obtain a current value. Patent Document 1 describes solder and wiring patterns that cause errors in detecting the potentials at both ends of the resistance element connected to the wiring pattern on the circuit board when the current is detected by this type of current detection unit. A structure for eliminating the influence of impedance and enabling detection of a potential as close as possible to the potential of both ends of the resistance element itself is disclosed.

Japanese Unexamined Patent Publication No. 2009-8548

When multiple resistance elements are connected in parallel by a wiring pattern and a current detector that detects current based on the combined resistance of multiple resistance elements is provided on the circuit board, the impedance of the path through which the current flows through each resistance element is used. If there is a difference, highly accurate current detection cannot be performed. For example, depending on the arrangement of the potential detection terminal provided on the wiring pattern and each resistance element, there may be a difference in the impedance of the path through which the current flows from the potential detection terminal via each resistance element. In such a case, highly accurate current detection cannot be performed.

In view of the above problems, an object of the present invention is to improve the detection accuracy by a current detection unit in which a plurality of resistance elements are connected in parallel.

In order to solve the above problems, the present invention is a circuit board having a substrate main body and a current detection unit for detecting a current to be detected flowing through a wiring pattern formed on the substrate main body, and the current detection unit. Is a current detection wiring pattern including a first wiring area provided with a first potential detection unit and a second wiring area provided with a second potential detection unit, the first wiring area, and the second wiring area. A plurality of resistance elements connected in parallel via a wiring region are provided, and the plurality of resistance elements include a first resistance element arranged on one side in the first direction and the other resistance element in the first direction. A first path that includes a second resistance element arranged on the side and passes through the first resistance element as a path through which the detected current flows between the first potential detection unit and the second potential detection unit. A second path via the second resistance element is provided, and the first path is from the first portion of the first path from the first potential detection unit to the first resistance element and from the first resistance element. First path to the second potential detection unit
A second portion is provided, and the second path includes a first portion of the second path from the first potential detection unit to the second resistance element, and a second path from the second resistance element to the second potential detection unit. The second portion of the route is provided, and the magnitude relationship between the first portion of the first route and the first portion of the second route is the path length between the second portion of the first route and the second portion of the second route. It is characterized by the fact that it is the opposite of the magnitude relationship of.

According to the present invention, the detected current can be obtained from the potential difference between the first potential detection unit and the second potential detection unit and the combined resistance of a plurality of resistance elements. Further, the magnitude relationship between the path length of the path portion on the first potential detection unit side with respect to the first resistance element and the second resistance element, and the path length on the second potential detection unit side with respect to the first resistance element and the second resistance element. The magnitude relationship of the path length of the path part is reversed. As a result, the difference in the path length of the path portion on the first potential detection unit side and the difference in the path length of the path portion on the second potential detection unit side are offset when the two path portions are totaled . Due to the difference in the impedance of the paths, the currents flowing through the plurality of paths differ, and the detection error of the resulting current value can be reduced. Therefore, the current can be detected with high accuracy. Further, since the detection error due to the difference in impedance of the plurality of paths does not exceed the detection error due to the component characteristics of the resistance element, the component characteristics of the resistance element are not wasted. Therefore, when a highly accurate resistance element is used, the current can be detected with high accuracy by effectively using the component performance.

In the present invention, the first wiring region and the second wiring region face each other in a second direction orthogonal to the first direction, and each of the first resistance element and the second resistance element is the first wiring. It is possible to adopt a configuration that is arranged so as to bridge between the area and the second wiring area. Further, in the present invention, the first potential detection unit is provided on the first wiring region at a position closer to the first resistance element than the second resistance element, and the second potential detection unit is the same. It is desirable that the second resistance element is provided at a position closer to the second resistance element than the first resistance element on the second wiring region. When such an arrangement is adopted, the relationship between the magnitude of the path length of the path portion on the first potential detection unit side with respect to the first resistance element and the second resistance element, and the first with respect to the first resistance element and the second resistance element. 2 The relationship between the magnitude of the path length of the path portion on the potential detection unit side is reversed. As a result, the difference in the path length of the path portion on the first potential detection unit side and the difference in the path length of the path portion on the second potential detection unit side are offset when the two path portions are totaled. Therefore, the difference in impedance between the current path passing through the first resistance element and the current path passing through the second resistance element can be reduced. Therefore, the current can be detected with high accuracy.

Further, when the first potential detection unit and the second potential detection unit are arranged at such positions, only the region on the first resistance element side needs to be widened in the first wiring region, and the second wiring region is the second wiring region. 2 Only the area on the resistance element side needs to be widened. Therefore, since the wiring pattern can be prevented from being formed in the unnecessary region, the area of the current detection wiring pattern can be reduced. Therefore, the area occupied by the board of the current detection unit can be reduced, and the circuit board can be miniaturized. In addition, the degree of freedom in circuit arrangement on the circuit board can be increased. Therefore, the degree of freedom in designing the circuit board is increased.

In the present invention, a configuration capable of realizing the above arrangement can be defined as follows. That is, before Symbol said second potential detecting section and the first potential detection unit, out of the one side of the corner portion of the first direction of said first resistor element, one side of the second direction perpendicular to the first direction The midpoint of the diagonal line connecting the first corner portion located at and the second corner portion located on the other side of the second direction among the corner portions on the other side of the first direction of the second resistance element. As a reference, the first potential detection unit is arranged on one side of the first direction from the midpoint and in the first diagonal region on one side of the second direction from the midpoint, and the first potential detection unit is arranged from the midpoint. It is possible to adopt a configuration in which the second potential detection unit is arranged on the other side of the first direction and in the second diagonal region on the other side of the second direction from the midpoint.

In this arrangement, the first potential detection unit and the second potential detection unit are arranged on one side and the other side in the diagonal direction with reference to the midpoint of the diagonal line of the arrangement region of the plurality of resistance elements. .. In such an arrangement, the magnitude relationship between the path lengths of the path passing through the first resistance element and the path passing through the second resistance element is reversed between the first potential detection unit side and the second potential detection unit side. Therefore, the difference between the impedances of the two paths can be reduced, and the current can be detected with high accuracy. Further, in such an arrangement, only the diagonally one-sided and the other-sided regions need be widened. Therefore, the area of the wiring pattern for current detection can be reduced, so that the area occupied by the board of the current detection unit can be reduced, and the circuit board can be miniaturized.

In this case, it is desirable that the first potential detection unit and the second potential detection unit are provided at positions symmetrical with respect to the midpoint. By doing so, the impedance of the path passing through the first resistance element and the path passing through the second resistance element can be the same or substantially the same. Therefore, the current can be detected with high accuracy.

In the present invention, it is desirable that at least one of the first potential detection unit and the second potential detection unit is formed with a through hole penetrating the substrate main body. In this way, the impedance can be adjusted by adjusting the path length of the path through which the current flows by changing the position of the through hole connecting the potential detection terminal. Therefore, if a plurality of through holes are formed in advance, the impedance of the path through which the current flows can be adjusted without changing the wiring pattern. Further, since the wiring patterns formed on one surface of the substrate body and the other surface can be conducted by through holes, resistance elements can be arranged on both sides of the circuit board to form a current detection unit. Further, when the substrate main body is a multilayer substrate, a wiring pattern can be formed on a layer other than the substrate surface and the wiring can be conducted through the through hole. Therefore, the formation area of the wiring pattern can be widened.

In the present invention, it is desirable that the resistance element is arranged on one surface and the other surface of the substrate body. By doing so, the area occupied by the substrate of the current detection unit can be reduced as compared with the case where all the resistance elements are arranged on one side of the substrate main body.

In this case, it is desirable that the same number of resistance elements are arranged on the one surface and the other surface. By doing so, it is possible to reduce the difference in impedance of the path passing through each resistance element as compared with the case where the number of resistance elements is different on the front and back sides. Further, it is desirable that the arrangement of the resistance element on the one surface and the other surface is the same. By doing so, it is possible to reduce the difference in impedance of the path passing through each resistance element with a simple arrangement. Therefore, the detection accuracy can be easily improved.

In the present invention, it is desirable that the plurality of resistance elements have the same nominal resistance value. In this way, the detected current can be obtained more easily as compared with the case where the current detection unit is configured by using a plurality of resistance elements having different nominal resistance values.

Next, the motor control device of the present invention is connected to the inverter circuit via the circuit board, the inverter circuit that supplies the three-phase alternating current, and the wiring pattern on the circuit board, and is connected to the inverter circuit from the inverter circuit. It has an output terminal that supplies the supplied three-phase current to the coil of the servo motor, and the current detection unit is connected in series between the inverter circuit and the output terminal, and is out of the three phases. It is characterized by detecting at least two phases of current.

According to the present invention, since the current detection unit for detecting the current supplied from the inverter circuit to the servo motor is provided, the current value supplied to the servo motor can be monitored. In addition, the current detection unit can detect the current with high accuracy. Therefore, the feedback control can be performed based on the detected current value, and the servomotor can be controlled with high accuracy. Further, since the total value of the three-phase currents for driving the servomotor becomes 0, if the current of two of the three phases is detected, the current value of the remaining one phase is the detected two-phase current. It can be calculated from the value. Therefore, the number of current detection units can be reduced as compared with the case where the three-phase currents are detected by the current detection units. Therefore, the number of parts and the assembly man-hours can be reduced, which is advantageous for cost reduction and miniaturization.

According to the present invention, the detected current can be obtained from the potential difference between the first potential detection unit and the second potential detection unit and the combined resistance of a plurality of resistance elements. Further, the magnitude relationship of the path length of the path portion on the first potential detection unit side with respect to the first resistance element and the second resistance element, and the path length on the second potential detection unit side with respect to the first resistance element and the second resistance element. The magnitude relationship of the path length of the path part is reversed. As a result, the difference in the path length of the path portion on the first potential detection unit side and the difference in the path length of the path portion on the second potential detection unit side are offset when the two path portions are totaled . It is possible to prevent a difference in the currents flowing through the plurality of paths due to the difference in the impedance of the paths, and the resulting detection error of the current value exceeding the resistance value tolerance of the resistance element. Therefore, since there is little possibility that a detection error exceeding the detection error due to the component characteristics of the resistance element will occur, the current can be detected with high accuracy.

It is a perspective view of the motor control device to which this invention is applied seen from the front side (diagonally upper right). It is an exploded perspective view of the motor control device seen from the side of the 1st cover member. It is a block diagram of a motor control device and a servomotor. It is explanatory drawing which shows the current detection schematically. It is a graph which shows the current detection error.

Hereinafter, embodiments of a circuit board and a motor control device to which the present invention is applied will be described with reference to the drawings. The motor control device of this embodiment is a servo amplifier used to control a servomotor.

FIG. 1 is a perspective view of the motor control device 1 to which the present invention is applied as viewed from the front side (obliquely upper right). The "right" in the theory of FIG. 1 is the "right" when the motor control device 1 is viewed from the front side. In the present specification, the three directions of XYZ are directions orthogonal to each other, the X direction is the width direction (horizontal direction) of the motor control device 1, the Y direction is the vertical direction of the motor control device 1, and the Z direction is. This is the front-rear direction of the motor control device 1. Further, one side (right side) in the X direction is indicated by + X, the other side (left side) is indicated by -X, one side (upper side) in the Y direction is indicated by + Y, and the other side (lower side) is indicated by -Y, in the Z direction. One side (front side) is indicated by + Z, and the other side (rear side) is indicated by −Z.

(Motor control device)
As shown in FIG. 1, the motor control device 1 has a rectangular parallelepiped shape as a whole. The motor control device 1 includes a frame 10 arranged substantially in the center of the width direction X, and a cover member 20 fixed to the frame 10. The cover member 20 is arranged on one side (+ X direction) of the width direction X with respect to the frame 10 and on the other side (−X direction) of the width direction X with respect to the frame 10. A second cover member 22 and a third cover member 23 arranged in front of the first cover member 21 (in the + Z direction) are provided. A connector portion 24 is provided on the + X direction side (right side) portion of the front surface of the motor control device 1. Further, an opening / closing lid 25 is provided on a portion of the front surface of the motor control device 1 on the −X direction side (left side). An output terminal portion (see FIG. 3) is provided inside the opening / closing lid 25.

The frame 10 includes a frame main body 11 arranged at the center of the motor control device 1 in the width direction X, and a rectangular back plate 12 provided at the rear end (end in the −Z direction) of the frame main body 11. A hook 13 is formed on the frame main body 11, and the first cover member 21 and the second cover member 22 have an engaging hole 27 formed at a position corresponding to the hook 13. The first cover member 21 and the second cover member 22 are fixed to the frame 10 by a hook mechanism including a hook 13 and an engaging hole 27. Further, the third cover member 23 includes a hook 231 that is engaged with the engaging hole 28 formed in the first cover member 21, and the first cover member is provided with a hook mechanism including the engaging hole 28 and the hook 231. The third cover member 23 is fixed to 21. The fixing structure between the frame 10 and the cover member 20 may be a structure other than the hook mechanism.

FIG. 2 is an exploded perspective view of the motor control device 1 as seen from the side of the first cover member 21. As shown in FIG. 2, inside the first cover member 21, the heat radiation fins 30 and the first substrate 40 integrally formed with the frame main body 11 are arranged. The first substrate 40 is arranged between the heat radiation fin 30 and the third cover member 23, and is screwed to the boss portion 15 protruding from the frame main body 11 in the + X direction. Further, a second substrate (not shown) is arranged inside the second cover member 22. The second substrate is screwed to a boss portion (not shown) protruding in the −X direction from the frame main body 11.

Heat-generating electronic components are fixed to the surface of the frame body 11 facing the −X direction. In this embodiment, as heat-generating electronic components, a diode bridge 43 constituting the rectifier circuit 61 described later and an IGBT transistor 42 constituting the inverter circuit 63 are provided. The heat radiating fin 30 projects from the frame body 11 to the side opposite to the side to which the heat generating electronic component is fixed. As shown in FIG. 2, a cooling fan 32 is arranged on the −Y direction side of the heat radiation fin 30. The cooling air from the fan 32 is blown in the + Y direction and discharged from the top surface of the motor control device 1 via the heat radiation fins 30.

(Control system)
FIG. 3 is a block diagram of the motor control device 1 and the servo motor 2. The motor control device 1 supplies a three-phase current of U phase, V phase, and W phase to the servomotor 2 via a terminal portion provided inside the opening / closing lid 25. The servomotor 2 includes an encoder 3 that detects the rotational position of the output shaft, and the encoder signal is input to the motor control device 1 via the connector unit 24.

The first board 40 is a control board. The first substrate 40 is provided with a control circuit including an MCU 51 as a control element and a gate drive IC 52. An encoder signal is input to the MCU 51 from the encoder 3 of the servomotor 2, and a current detection signal from the current detection unit 70 that detects the current of two of the three phases supplied to the servomotor 2 is input to the MCU 51. Entered. As will be described later, the current detection unit 70 is configured to detect potentials at two locations on both ends of the resistance element. The current detection signal from the current detection unit 70 is input to the MCU 51 via the A / D converter 80. Further, a control command from the outside is input to the MCU 51 via the connector unit 24.

The second board (not shown) is a driver board. On the second board, a rectifier circuit 61 connected to the commercial AC power supply 60, a smoothing capacitor 62 connected to the rectifier circuit 61, an inverter circuit 63 connected in series with the smoothing capacitor 62, and an inverter circuit 63. A current detection unit 70 for detecting the current supplied from the inverter to the servo motor 2 is provided. The rectifier circuit 61 is composed of the diode bridge 43 described above, and rectifies the power supply current shared from the commercial AC power supply 60 to charge the smoothing capacitor 62. The inverter circuit 63 includes six IGBT transistors 42 and a recirculation diode 46 connected in parallel to each IGBT transistor 42.

The MCU 51 provided on the first substrate 40 supplies a PWM signal to the gate drive IC 52 based on the encoder signal and the current detection signal. The gate drive IC 52 supplies the gate drive signal to the inverter circuit 63 based on the PWM signal. As a result, the switching operation of the IGBT transistor 42 is performed, and the U-phase, V-phase, and W-phase motor drive currents are generated. In configuring the servomotor control circuit, an IPM (intelligent power module) in which the inverter circuit 63 is modularized can also be used.

(Current detector)
The terminal portion of the motor control device 1 is provided with output terminals 29U, 29V, 29W (see FIG. 3) connected to the coil of the servomotor 2. Further, the second board (not shown) includes a board body and a wiring pattern formed on the surface of the board body, and the output terminals 29U, 29V, and 29W are inverters via the wiring pattern on the second board. It is connected to the circuit 63, and U-phase, V-phase, and W-phase motor drive currents are supplied from the inverter circuit 63 to the coil of the servo motor 2. The second board is provided with a current detection unit 70 inserted in series between the output terminals 29U, 29V, 29W and the inverter circuit 63 to detect the motor drive current. That is, the second substrate is a circuit board to which the present invention is applied. The current detection unit 70 is provided at two locations on the second substrate and detects the current value of two of the three-phase motor drive currents. In this embodiment, the currents of the U phase and the V phase are detected, but the two phases to be detected do not have to be the U phase and the V phase. Since the total of the three-phase motor drive currents is 0, the MCU 51 calculates the current value of the remaining one phase from the current values of the two phases.

The motor control device 1 includes a current detection unit 70U for detecting the U-phase motor drive current and a current detection unit 70V for detecting the V-phase motor drive current as the current detection unit 70. Each of the current detection units 70U and 70V includes a current detection wiring pattern formed on the second substrate and a plurality of resistance elements. The plurality of resistance elements have the same or similar resistance values, and are connected in parallel by a current detection wiring pattern.

FIG. 4 is an explanatory diagram schematically showing the current detection unit 70, and FIGS. 4A to 4C are examples of the form of the current detection unit 70, respectively. The current detection unit 70 may have any of the forms shown in FIGS. 4 (a) to 4 (c). Further, in the form shown in FIGS. 4A to 4C, the number of resistance elements is 2, but the number of resistance elements may be 3 or more. Further, the current detection unit may be provided on one surface and the other surface of the circuit board. For example, even in a form in which a wiring pattern for current detection and a resistance element are provided on one surface and the other surface of the circuit board, and a plurality of resistance elements are connected in parallel via a through hole penetrating the circuit board. good.

The current detection unit 70 shown in FIGS. 4A to 4C has two resistance elements (first resistance element R1 and second resistance element R2) arranged in the first direction RX and the first direction. A first wiring region 71 and a second wiring region 72 facing the second direction RY orthogonal to the RX are provided. The first wiring area 71 and the second wiring area 72 constitute a wiring pattern for current detection. A first potential detection unit 73 is provided in the first wiring region 71. Further, a second potential detection unit 74 is provided in the second wiring region 72. The first resistance element R1 and the second resistance element R2 are connected in parallel by the first wiring region 71 and the second wiring region 72.

The current detection unit 70 is connected to a wiring pattern on the circuit board so that a current flows between the first potential detection unit 73 and the second potential detection unit 74. The current detection unit 70 uses the first path C1 and the second resistance element R2 via the first resistance element R1 as a path through which the current flows between the first potential detection unit 73 and the second potential detection unit 74. It is provided with a second route C2 via. Since the current detection unit 70 has a predetermined combined resistance corresponding to the resistance values of the first resistance element R1 and the second resistance element R2, the potential difference between the first potential detection unit 73 and the second potential detection unit 74 and the combined resistance The current value can be measured based on. When the resistance values of a plurality of resistance elements connected in parallel are the same, the current detection unit 70 selects the element because the current loss (heat generation) due to the first resistance element R1 and the second resistance element R2 becomes equal. It is easy to calculate the detection accuracy. Therefore, it is easiest to measure the current value. Therefore, it is desirable to use the same resistance value as the first resistance element R1 and the second resistance element R2.

When the impedance of the first path C1 passing through the first resistance element R1 and the impedance of the second path C2 passing through the second resistance element R2 are equal, the current detection unit 70 causes a current to flow evenly through the two paths. be able to. When the current flows evenly, the current value can be measured with the highest accuracy based on the combined resistance when the first resistance element R1 and the second resistance element R2 are connected in parallel. Therefore, the current detection unit 70 determines the difference between the path length of the first path C1 and the path length of the second path C2 in order to reduce the difference between the impedance of the first path C1 and the impedance of the second path C2. Has adopted a small configuration. For example, the difference between the impedance of the first path C1 and the impedance of the second path C2 is configured to be within the range of the resistance value tolerance with respect to the nominal resistance values of the first resistance element R1 and the second resistance element R2. ing. In the current detection unit 70 of the present embodiment, the measurement error of the current value due to the difference between the impedance of the first path C1 and the impedance of the second path C2 is the resistance value of the first resistance element R1 and the second resistance element R2. It is less than or equal to the measurement error due to the tolerance.

In the example of FIG. 4A, the first path C1 is the first path portion C11 from the first potential detection unit 73 to the first resistance element R1 and the first resistance element R1 to the second potential detection unit 74. A second path portion C12 is provided. Further, the second path C2 includes a first path portion C21 from the first potential detection unit 73 to the second resistance element R2, and a second path portion C22 from the second resistance element R2 to the second potential detection unit 74. .. Further, the first potential detection unit 73 is arranged on the first wiring region 71 at a position closer to the first resistance element R1 than to the second resistance element R2. On the other hand, the second potential detection unit 74 is arranged on the second wiring region 72 at a position closer to the second resistance element R2 than to the first resistance element R1.

In the above four path portions, the magnitude relationship between the path lengths of the first path portion C11 and the first path portion C21 is opposite to the magnitude relationship between the path lengths of the second path portion C12 and the second route portion C22. It has become. Therefore, the magnitude relationship between the impedances of the first path portion C11 and the first path portion C21 is opposite to the magnitude relationship between the impedances of the second path portion C12 and the second path portion C22. As described above, in the first path C1 and the second path C2, the magnitude relation of the path length between the first potential detection unit 73 side and the second potential detection unit 74 side with respect to the first resistance element R1 and the second resistance element R2. If is reversed, at least a part of the impedance difference is canceled out when the impedances of the path portions on the first potential detection unit 73 side and the second potential detection unit 74 side are totaled. Therefore, since the difference between the impedance of the entire first path C1 and the impedance of the entire second path C2 is small, the measurement error of the current value due to the difference between the impedances of the first path C1 and the second path C2 is small.

In the example of FIG. 4A, in order to reverse the magnitude relationship of the path length between the first potential detection unit 73 side and the second potential detection unit 74 side with respect to the first resistance element R1 and the second resistance element R2, The first potential detection unit 73 and the second potential detection unit 74 are arranged as follows. That is, the arrangement region of the first resistance element R1 and the first resistance element R1 is rectangular as a whole, and the midpoint D of the diagonal corner portions (first corner portion E1 and second corner portion E2) is used as a reference. The first potential detection unit 73 is arranged on one of the first diagonal region F1 and the second diagonal region F2 located diagonally, and the second potential detection unit 74 is arranged on the other side.

In other words, the first corner portion E1 located on one side RY1 of the second direction RY among the two corner portions provided on the edge of the one side RX1 of the first direction RX of the first resistance element R1 and the first. 2 The midpoint of the diagonal line connecting the second corner portion E2 located on the other side RY2 of the second direction RY among the two corner portions provided on the edge of the other side RX2 of the first direction RX of the resistance element R2. With reference to D, the first potential detection unit 73 is arranged on one side RX1 of the first direction RX from the midpoint D and in the first diagonal region F1 of the one side RY1 of the second direction RY from the midpoint D. Has been done. Further, the second potential detection unit 74 is arranged on the other side RX2 of the first direction RX from the midpoint D and in the second diagonal region F2 of the other side RY2 of the second direction RY from the midpoint D.

In this way, the first potential detection unit 73 and the second potential detection unit are located diagonally with respect to the midpoint D of the diagonal line of the rectangular region in which the first resistance element R1 and the second resistance element R2 are arranged. By arranging 74, the difference between the path length of the first path C1 and the path length of the second path C2 can be reduced. Therefore, the difference in impedance between the first path C1 and the second path C2 can be reduced.

In the example of FIG. 4B, the first resistance element R1 and the second resistance element R2 are arranged at positions deviated from each other in the second direction RY. Even with such an arrangement, the midpoint D of the diagonal positions (first corner portion E1 and second corner portion E2) of the region where the first resistance element R1 and the second resistance element R2 are arranged is used as a reference. The first potential detection unit 73 can be arranged in one of the first diagonal region F1 and the second diagonal region F2 located in the diagonal direction, and the second potential detection unit 74 can be arranged in the other. Therefore, similarly to the example of FIG. 4A, the difference in the path lengths of the first path C1 and the second path C2 can be reduced, and the difference in impedance between the first path C1 and the second path C2 can be reduced. be able to.

In the embodiments of FIGS. 4A and 4B, the first wiring region 71 and the second wiring region 72 are the first diagonal region F1 in which the first potential detection unit 73 is arranged, and the second potential detection. Diagonal regions (third diagonal regions G1 and fourth) on the side where the first potential detection unit 73 and the second potential detection unit 74 are not arranged, although they extend to the second diagonal region F2 in which the unit 74 is arranged. In the diagonal region G2), it is not necessary to provide a wiring pattern in order to provide the potential detection unit. Therefore, the first wiring region 71 and the second wiring region 72 do not extend to the third diagonal region G1 and the fourth diagonal region G2, and in the third diagonal region G1 and the fourth diagonal region G2, the first wiring region 71 and the second wiring region 72 do not extend to the third diagonal region G1 and the fourth diagonal region G2. It has a concave shape on the side of the resistance element. Therefore, the occupied area of the current detection unit 70 on the second substrate is small.

In the current detection unit 70 shown in FIG. 4C, a plurality of through holes 75 penetrating the substrate main body are formed in the first potential detection unit 73 and the second potential detection unit 74. In this way, if a plurality of through holes 75 are formed in advance, the detection position of the potential difference can be adjusted without changing the wiring pattern. Therefore, the impedances of the first path C1 and the second path C2 can be adjusted after the formation of the current detection unit 70. Further, the through holes 75 can make the wiring patterns provided on one surface and the other surface of the circuit board conductive. Therefore, a plurality of resistance elements can be arranged on one surface and the other surface of the circuit board to form a current detection unit 70 in which these are connected in parallel. Further, when a multilayer board is used as the circuit board, the wiring pattern or resistance element provided on the surface of the circuit board can be made conductive with the wiring pattern provided on the inner layer. Therefore, the circuit board can be miniaturized. The through hole 75 may be provided only in one of the first potential detection unit 73 and the second potential detection unit 74.

In the modes of FIGS. 4A to 4C, the first potential detection unit 73 and the second potential detection unit 74 are arranged at positions symmetrical with respect to the midpoint D. In such an arrangement, the path lengths of the first path C1 and the second path C2 are the same or almost the same. Therefore, the measurement error due to the difference in impedance between the first path C1 and the second path C2 can be reduced.

FIG. 5 is a graph showing a current detection error. In FIG. 5, the graph H1 shown by a solid line shows the current detection error of the current detection unit (not shown) of the comparative example. In the current detection unit of the comparative example, the second potential detection unit 74 shown in the example of FIG. 4C is provided in the second diagonal region F2, but the first potential detection unit 73 has the first diagonal. It is not a region F1 but is provided at a position substantially equal to the first resistance element R1 and the second resistance element R2. Further, the graph H2 shown by the broken line shows the current detection error of the current detection unit 70 shown in FIG. 4 (c). From the data of FIG. 5, it can be seen that the current detection error becomes very small by moving the first potential detection unit 73 to the diagonal region.

(Main effect of this form)
As described above, the second substrate of the motor control device 1 of the present embodiment includes a circuit pattern in which the detected current flows (for example, a circuit pattern in which the motor drive current flows) and a current detection unit 70 for detecting the detected current. The current detection unit 70 includes a plurality of resistance elements (for example, the first resistance element R1 and the second resistance element R2) connected in parallel via the first wiring region 71 and the second wiring region 72. There is. Therefore, it is covered by the potential difference between the first potential detection unit 73 provided in the first wiring region 71 and the second potential detection unit 74 provided in the second wiring region 72, and the combined resistance of the plurality of resistance elements. The detection current can be obtained. Further, if the resistance values (nominal resistance values) of the plurality of resistance elements constituting the current detection unit 70 are the same, as compared with the case where the current detection unit 70 is configured by using a plurality of resistance elements having different resistance values. Therefore, the detected current can be obtained more easily.

Further, the current detection unit 70 of the present embodiment includes a plurality of paths (for example, first path C1 and second path C2) through which a current flows via a plurality of resistance elements, and the impedance of the plurality of paths. The difference is within the range of the resistance value tolerance with respect to the nominal resistance value of the resistance element constituting the current detection unit 70. Therefore, it is possible to reduce the detection error of the current value due to the difference in the currents flowing through the plurality of paths due to the difference in the impedances of the plurality of paths. Further, since the detection error due to the difference in impedance of the plurality of paths does not exceed the detection error due to the component characteristics of the resistance element, the component characteristics of the resistance element are not wasted. Therefore, when a highly accurate resistance element is used, the current can be detected with high accuracy by effectively using the component performance.

Specifically, in the present embodiment, the first potential detection unit 73 is provided on the first wiring region 71 at a position closer to the first resistance element R1 than the second resistance element R2, and the second potential detection unit 74. Is provided on the second wiring region 72 at a position closer to the second resistance element R2 than to the first resistance element R1. As a result, in the first path C1 and the second path C2, the difference in the path length of the path portion on the first potential detection unit 73 side and the difference in the path length of the path portion on the second potential detection unit 74 side are both routes. At least part is offset when the parts are summed. Therefore, the difference in impedance between the first path C1 and the second path C2 can be reduced.

This arrangement can also be specified as follows. That is, the current detection unit 70 includes a first resistance element R1 arranged on one side RX1 of the first direction RX and a second resistance element R2 arranged on the other side RX2 of the most first direction RX. The 1-potential detection unit 73 and the 2nd potential detection unit 74 are located on one side RY1 of the 2nd direction RY orthogonal to the 1st direction RX among the corner portions of the 1st direction RX 1 side RX1 of the 1st resistance element R1. Diagonal line connecting the located first corner portion E1 and the second corner portion E2 located on the other side RY2 of the second direction RY among the corner portions of the other side RX2 of the first direction RX of the second resistance element R2. With the midpoint D as a reference, the first potential detection unit 73 is located on one side RX1 of the first direction RX from the midpoint D and in the first diagonal region F1 of the one side RY1 of the second direction RY from the midpoint D. Is arranged, and the second potential detection unit 74 is arranged in the second diagonal region F2 of the other side RX2 of the first direction RX from the midpoint D and the other side RY2 of the second direction RY from the midpoint D. There is. In this way, by arranging the first potential detection unit 73 and the second potential detection unit 74 on one side and the other side in the diagonal direction with reference to the midpoint D of the diagonal line of the arrangement region of the plurality of resistance elements, the first potential detection unit 73 and the second potential detection unit 74 are arranged. The difference in path length between the first path C1 and the second path C2 can be reduced, and the difference in impedance between the first path C1 and the second path C2 can be reduced.

In particular, if the first potential detection unit 73 and the second potential detection unit 74 are provided at positions symmetrical with respect to the midpoint D, the first path C1 and the second resistance element passing through the first resistance element R1 are provided. The impedance of the second path C2 passing through R2 can be made the same. In this case, the detection error due to the difference in the path length between the first path C1 and the second path C2 does not occur.

Further, when the first potential detection unit 73 is arranged near the first resistance element R1 and the second potential detection unit 74 is arranged near the second resistance element as in the present embodiment, the first wiring region 71 is the first. Only the region on the resistance element R1 side may be widened, and the second wiring region 72 may widen only the region on the second resistance element R2 side. Therefore, the area of the current detection wiring pattern can be reduced by preventing the wiring pattern from being formed in an unnecessary region. Therefore, the area occupied by the board of the current detection unit 70 can be reduced, and the circuit board can be miniaturized. Alternatively, the degree of freedom in circuit arrangement on the circuit board can be increased, and the degree of freedom in designing the circuit board can be increased.

Further, the current detection unit 70 can adopt a form in which a through hole 75 penetrating the substrate main body is formed in the first potential detection unit 73 and the second potential detection unit 74. If a plurality of through holes 75 are formed in advance at positions where the potential is detected, the impedance of the path through which the current flows can be adjusted without changing the wiring pattern. Further, when the substrate main body is a multilayer substrate, a wiring pattern can be formed in a layer other than the substrate surface and conducted through the through hole 75, so that the formation area of the wiring pattern can be widened. ..

Further, when the through holes 75 are formed in the substrate body, resistance elements can be arranged on both sides of the substrate body and connected in parallel via the through holes 75 to form the current detection unit 70. In this case. In this case, the area occupied by the board of the current detection unit can be reduced as compared with the case where all the resistance elements are arranged on one side of the board body. Further, when the same number of resistance elements are arranged on both sides of the substrate body, the difference in impedance of the path passing through each resistance element can be reduced by a simple arrangement. Therefore, the detection accuracy can be easily improved.

An inverter circuit 63 that supplies a three-phase motor drive current is mounted on the second substrate of the motor control device 1 of the present embodiment, and the inverter circuit 63 and two of the three phases are used as the current detection unit 70. Current detection units 70U and 70V connected in series with the output terminals 29U and 29V that output the motor drive current of the above are provided. Therefore, since the current value supplied to the servomotor 2 can be detected with high accuracy, the servomotor can be controlled with high accuracy. Further, since only the current of two of the three phases is detected and the current value of the remaining one phase is obtained from the detected current value of the two phases, the current of each of the three phases is detected by the current detection unit 70. In comparison, the number of current detection units 70 can be reduced. Therefore, the number of parts and the assembly man-hours can be reduced, which is advantageous for cost reduction and miniaturization.

(Other embodiments)
In the above embodiment, the present invention is applied to a circuit board provided with a current detection unit 70 for detecting a motor drive current, but the current detection unit 70 can also be used to detect a current other than the motor drive current. can.

1 ... motor control device, 2 ... servo motor, 3 ... encoder, 10 ... frame, 11 ... frame body, 12 ... back plate, 13 ... hook, 15 ... boss part, 20 ... cover member, 21 ... first cover member, 22 ... 2nd cover member, 23 ... 3rd cover member, 24 ... Connector part, 25 ... Open / close lid, 27 ... Engagement hole, 28 ... Engagement hole, 29U, 29V, 29W ... Output terminal, 30 ... Radiation fin, 32 ... fan, 40 ... first board, 42 ... IGBT transistor, 43 ... diode bridge, 44 ... insulator, 46 ... recirculation diode, 51 ... MCU, 52 ... gate drive IC, 60 ... commercial AC power supply, 61 ... rectifying circuit, 62 ... Smoothing capacitor, 63 ... Inverter circuit, 70 ... Current detection unit, 71 ... First wiring area, 72 ... Second wiring area, 73 ... First potential detection unit, 74 ... Second potential detection unit, 75 ... Through hole , 80 ... A / D converter, 231 ... Hook, C1 ... 1st path, C11 ... 1st path part, C12 ... 2nd path part, C2 ... 2nd path, C21 ... 1st path part, C22 ... 2nd Path portion, D ... Midpoint, E1 ... 1st corner, E2 ... 2nd corner, F1 ... 1st diagonal region, F2 ... 2nd diagonal region, G1 ... 3rd diagonal region, G2 ... 4th Diagonal region, R1 ... first resistance element, R2 ... second resistance element, RX ... first direction, RX1 ... one side of the first direction, RX2 ... the other side of the first direction, RY ... second direction, RY1 ... One side of the second direction, RY2 ... the other side of the second direction, X ... width direction, Y ... vertical direction, Z ... front-back direction

Claims (11)

A circuit board having a board body and a current detection unit that detects a current to be detected flowing through a wiring pattern formed on the board body.
The current detection unit
A wiring pattern for current detection including a first wiring area provided with a first potential detection unit and a second wiring area provided with a second potential detection unit, and a wiring pattern for current detection.
A plurality of resistance elements connected in parallel via the first wiring region and the second wiring region are provided.
The plurality of resistance elements include a first resistance element arranged on one side of the first direction and a second resistance element arranged on the other side of the first direction.
As a path through which the detected current flows between the first potential detection unit and the second potential detection unit, a first path via the first resistance element and a second path via the second resistance element. Equipped with a route,
The first path includes a first path first portion from the first potential detection unit to the first resistance element, and a first path second portion from the first resistance element to the second potential detection unit. ,
The second path includes a first portion of the second path from the first potential detection unit to the second resistance element, and a second portion of the second path from the second resistance element to the second potential detection unit. ,
The magnitude relationship between the first portion of the first route and the first portion of the second route is opposite to the magnitude relationship between the second portion of the first route and the second portion of the second route. circuit board, characterized by that. The first wiring area and the second wiring area face each other in a second direction orthogonal to the first direction.
The circuit board according to claim 1, wherein each of the first resistance element and the second resistance element is arranged so as to bridge between the first wiring region and the second wiring region. The first potential detecting unit before SL, in the first wiring region provided at a position closer to the first resistive element than said second resistive element,
The circuit according to claim 1 or 2 , wherein the second potential detection unit is provided at a position closer to the second resistance element than the first resistance element on the second wiring region. substrate. Prior Symbol said second potential detecting section and the first potential detection unit,
Of the corner portions on one side of the first resistance element of the first resistance element, the first corner portion located on one side of the second direction orthogonal to the first direction and the first corner portion of the second resistance element. Of the corners on the other side of the direction, one side of the first direction from the midpoint and with reference to the midpoint of the diagonal line connecting the second corner located on the other side of the second direction. The first potential detection unit is arranged in the first diagonal region on one side of the second direction from the midpoint, the other side of the first direction from the midpoint, and the second from the midpoint. The circuit board according to claim 3 , wherein the second potential detection unit is arranged in a second diagonal region on the other side in the direction. The circuit board according to claim 4 , wherein the first potential detection unit and the second potential detection unit are provided at positions symmetrical with respect to the midpoint. The invention according to any one of claims 1 to 5 , wherein a through hole penetrating the substrate main body is formed in at least one of the first potential detection unit and the second potential detection unit. Circuit board. The circuit board according to any one of claims 1 to 6 , wherein the resistance element is arranged on one surface and the other surface of the substrate body. The circuit board according to claim 7 , wherein the same number of resistance elements are arranged on one surface and the other surface. The circuit board according to claim 8 , wherein the arrangement of the resistance elements on one surface and the other surface is the same. The circuit board according to any one of claims 1 to 9 , wherein the plurality of resistance elements have the same nominal resistance value. The circuit board according to any one of claims 1 to 10.
Inverter circuit that supplies three-phase alternating current and
The current detection unit has an output terminal that is connected to the inverter circuit via a wiring pattern on the circuit board and supplies a three-phase current supplied from the inverter circuit to the coil of the servo motor. A motor control device which is connected in series between the inverter circuit and the output terminal and detects a current of at least two of the three phases.

Images