Shunt resistor, method for manufacturing shunt resistor, and control device

Abstract

To provide a shunt resistor which can suppress an increase in manufacturing cost and can be downsized.SOLUTION: A shunt resistor is included in a printed circuit board including a base layer and a conductor layer laminated directly or indirectly on the base layer, and includes a shunt resistor portion in a conductor pattern formed on the conductor layer, the shunt resistor portion is constituted by a narrow portion, which is a portion between a current path input side and a current path output side of a current path through which a current flows, the cross-sectional area in a plane perpendicular to the current flow direction through which the current flows is smaller than other portions.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a shunt resistor for current detection, a method for manufacturing the shunt resistor, and a control device using the shunt resistor.

Background Art

[0002] Conventionally, shunt resistors have been widely used for current detection applications. Such shunt resistors are known, for example, as shunt resistors having a shape including a plate-shaped resistor body and plate-shaped electrodes joined to both ends of the resistor body. The resistor body is made of an alloy such as a copper-nickel alloy, a copper-manganese alloy, an iron-chromium alloy, or a nickel-chromium alloy, and the electrodes are made of a highly conductive metal such as copper. In such a shunt resistor, when a current is passed through the resistance portion (detection portion) between the current path input side and the current path output side of the current path through which the energizing current flows, the voltage drop in the resistance portion is detected, and the current value of the above current is calculated by Ohm's law using the resistance value of the resistance portion.

[0003] In Patent Document 1, a prior art regarding the above shunt resistor is disclosed, in which the resistance value is determined by providing notches 11 and 12 as shown in FIG. 1, and further, the change in the resistance value with respect to temperature change (resistance temperature coefficient; TCR) is reduced by defining the notch positions.

Prior Art Document

Patent Document

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If a shunt resistor such as in the prior art is used, the TCR can be suppressed, and as a result, the current detection accuracy is increased. However, there are cases where high current detection accuracy is not required even if current detection accuracy is required, cases where a small TCR is not required, and cases where the temperature change range is not large. There are also cases where cost is emphasized more than current detection accuracy. That is, when using a shunt resistor of the prior art, the number of components increases by the amount related to the resistor of the above shape, so the manufacturing cost increases by this increase amount and it becomes difficult to achieve cost reduction, and downsizing is inhibited because a plate-shaped member is used. Further, when a shunt resistor is provided in a control device inherent in, for example, a controller of an electric device, if a shunt resistor of the above shape is used, it affects dimensions and the like, and downsizing is inhibited.

[0006] Therefore, an object of the present invention is to provide a shunt resistor, a method for manufacturing a shunt resistor, and a control device in which an increase in manufacturing cost is suppressed and downsizing is possible in order to solve the above problems of the prior art.

Means for Solving the Problems

[0007] The shunt resistor according to the present invention is included in a printed circuit board including a base material layer and a conductor layer directly or indirectly laminated on the base material layer, In the conductor pattern formed on the conductor layer, a narrow portion is provided between the energization path input side and the energization path output side of the energization path through which the energization current flows, and the cross-sectional area in the plane orthogonal to the energization direction in which the energization current flows is smaller than other portions. It is provided with a shunt resistor portion configured by

[0008] The method for manufacturing a shunt resistor according to the present invention includes a step of manufacturing a printed circuit board by directly or indirectly laminating a conductor layer on a base material layer, a step of forming a conductor pattern on the conductor layer and In the step of forming the conductor pattern, there is a step of forming a narrow portion which is a portion where the cross-sectional area in a plane orthogonal to the current-carrying direction of the current-carrying path through which the energizing current flows is smaller than other portions, between the current-carrying path input side and the current-carrying path output side of the current-carrying path through which the energizing current flows.

[0009] The shunt resistor according to the present invention and the shunt resistor by the above manufacturing method are configured as the narrow portion of the conductor pattern formed on the conductor layer included in the printed circuit board, so the number of components does not increase and the manufacturing cost does not increase. Therefore, an increase in manufacturing cost is suppressed, and downsizing is possible.

[0010] In the conductor pattern formed on the conductor layer, a heat dissipation pattern which is a portion extending from the narrow portion and through which the energizing current does not flow may be provided. With this configuration, heat generated in the narrow portion can be propagated to the heat dissipation pattern and released to the atmosphere through the heat dissipation pattern, or heat can be transferred to other parts of the printed circuit board and released to the atmosphere from the same parts. Thereby, an increase in the temperature of the narrow portion can be suppressed. Since the heat dissipation pattern is configured as the conductor pattern, it can contribute to propagating and dissipating heat generated in the printed circuit board, and further has an advantage that it does not affect the energizing current because the energizing current does not flow as described above. The heat dissipation pattern is preferably made of a metal suitable for heat dissipation from the viewpoint of heat dissipation, and is preferably planar and extending from the narrow portion.

[0011] A notch may be provided in the narrow portion. The notch provided in the narrow portion can adjust the cross-sectional area of the narrow portion in a plane orthogonal to the current-carrying direction of the energizing current, and can also extend and adjust the current-carrying length of the energizing current in the narrow portion, so that variations in the target (desired) shunt resistance value can be reduced.

[0012] The notch may be provided in the narrow portion so as to extend in a direction perpendicular to the current-carrying direction. With this configuration, the cross-sectional area of the narrow portion in a plane perpendicular to the current-carrying direction in which the current-carrying current flows and the current-carrying length of the narrow portion in which the current-carrying current flows can be adjusted more effectively, and variations in the target (desired) shunt resistance value can be further reduced.

[0013] The heat dissipation pattern may be present on the side opposite to the side where the notch is present with respect to the narrow portion. With this configuration, it is possible to provide the notch portion that exhibits the above-described effects while reducing the influence on heat transfer to the heat dissipation pattern due to the notch.

[0014] The control device according to the present invention the above-described shunt resistor, a detection unit that detects a current-carrying voltage value in the shunt resistor, a processing control unit that outputs a control signal using the current-carrying voltage value detected by the detection unit, and includes. In the control device according to the present invention, an increase in manufacturing cost is suppressed and downsizing is made possible by the shunt resistor that exhibits the above-described effects.

[0015] The control device a switching unit that switches between the current-carrying current from the current-carrying path input side and a specified current, includes a correction unit that performs a correction calculation of the current-carrying voltage value in the shunt resistor, After the switching unit switches from the current-carrying current to the specified current, the correction unit may perform a correction calculation of the current-carrying voltage value using the reference voltage value after the reference voltage value is detected by the detection unit. With a configuration including the correction unit and the like, the current-carrying voltage value in the shunt resistor, and thus the resistance value in the narrow portion, can be corrected.

Effects of the Invention

[0016] The shunt resistor, method for manufacturing a shunt resistor, and control device of the present invention can suppress an increase in manufacturing cost and can be downsized.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0018] A shunt resistor, method for manufacturing a shunt resistor, and control device according to an embodiment of this invention will be described together with the drawings.

[0019] The shunt resistor of this embodiment assumes a cost - focused scenario without demanding high current accuracy or a small resistance temperature coefficient. It is a resistance portion (shunt resistor portion) with a predetermined resistance value formed by a conductor pattern such as a copper foil on a printed circuit board such as a so - called single - sided substrate, double - sided substrate, or multi - layer substrate. That is, the shunt resistor of this embodiment is included in a printed circuit board including a base material layer and a conductor layer laminated directly or indirectly on the base material layer. As will be described later, in the conductor pattern formed on the conductor layer, a narrow portion (corresponding to the above - mentioned shunt resistor portion) is a portion where the cross - sectional area in a plane perpendicular to the current - flowing direction between the current - path input side and the current - path output side of the current - path through which the energizing current flows is smaller than other portions. With this configuration, it is not necessary to add a separate resistor component as in the prior art, suppressing the corresponding increase in manufacturing cost, and since a plate - like member as described above is not used, downsizing is achieved. Also, for example, when providing a shunt resistor in a control device within a controller of an electric device or the like, downsizing is similarly possible. Note that the above - mentioned predetermined resistance value is determined depending on the configuration of the narrow portion and the like.

[0020] The above - mentioned shunt resistor can be manufactured, for example, by a manufacturing process including a step of manufacturing a printed circuit board by directly or indirectly laminating a conductor layer on a base material layer, and a step of forming a conductor pattern on the conductor layer. In the step of forming the conductor pattern, there is a step of forming a narrow portion which is a portion where the cross - sectional area in a plane perpendicular to the current - flowing direction between the current - path input side and the current - path output side of the current - path through which the energizing current flows is smaller than other portions. Note that as the base material layer, paper, glass cloth, plastic films including epoxy resin, phenolic resin, polyimide film, PET film, etc. are used. As the conductor layer, for example, metals such as copper are used. The conductor layer is laminated directly or indirectly on one side, both sides, or inner layer of the base material layer using an adhesive or the like, directly or via other layers.

[0021] By the way, in the shunt resistor of the present embodiment as described above, since a large current flows through the shunt resistor portion of the conductor pattern on the printed circuit board, a temperature rise becomes a problem. Also, variations in the resistance value in the shunt resistor portion are assumed. Therefore, a method will be described below that enables current detection while suppressing the temperature rise and reducing the variations.

[0022] The resistance value of the copper foil pattern on the printed circuit board can be calculated from the conductivity (material) of the pattern, the thickness of the pattern, the length in the current-carrying direction, and the width in the direction orthogonal to the current-carrying direction. Therefore, the heat generation amount and the resistance value in the shunt resistor of the present embodiment are mainly determined by the dimensions of the shunt resistor portion formed of the copper foil, that is, the foil thickness, and the length and width with respect to the current-carrying direction. Since the foil thickness and conductivity are determined by the printed circuit board standard, if these are set to constant values, the resistance value increases in proportion to the length and inversely proportional to the width. Fig. 2 shows the resistance value when the copper foil thickness is 35 μm. At the same time, the heat generation amount when a current of 15 A is passed through the shunt resistor portion is also shown.

[0023] In Fig. 2, the following three points are within the various applicable ranges based on the arrangement conditions (length) during printed circuit board production, the detection voltage considering noise effects, and the allowable heat generation amount considering temperature rise. Pattern length: 10 to 30 mm Resistance value: 1 to 20 mΩ Heat generation amount: 0.5 W or less

[0024] Regarding the above three constraints, when dividing the regions according to the resistance value and the calorific value with respect to the pattern length, there are a resistance value establishment region Rg1 (resistance value with respect to the pattern length) and a calorific value establishment region Rg2 (calorific value with respect to the pattern length) shown in FIG. 2. However, although these regions are regions where establishment is possible as described above, they are extremely small regions, and there is a possibility that the regions will become narrower due to manufacturing errors or the like. Also, when the ambient temperature is high or the energization current is large, the region where establishment is possible will become even narrower. Therefore, as a countermeasure, it is conceivable to widen the calorific value establishment region Rg2, that is, to increase the allowable calorific value. On the other hand, in the shunt resistance portion [narrow portion] formed on the substrate, the area is narrowed, that is, the cross-sectional area in the plane orthogonal to the energization direction in which the energization current flows is made smaller than other portions to generate a desired resistance value. As a side effect, the heat dissipation performance deteriorates. Also, due to variations in the copper foil pattern thickness, width, etc., variations occur in the shunt resistance value.

[0025] Therefore, in the present embodiment, in a printed circuit board that generates a shunt resistance portion with a copper foil pattern as described above, the heat dissipation performance of the shunt resistance portion is improved to suppress the temperature rise. This structure will be described below. Also, a method for reducing variations in the shunt resistance value will be described.

[0026] The heat dissipation of the heat generated in the printed circuit board is mainly carried out from the copper foil pattern of a metal suitable for heat dissipation performance, and thus the area of the copper foil pattern affects it. Therefore, a heat dissipation pattern that does not form an energization path, that is, does not affect energization, is provided in the vicinity of the shunt resistance portion that easily generates heat to transfer the heat generated by the shunt resistance portion, and the heat generated by the shunt resistance portion is released from the heat dissipation pattern to the atmosphere or other parts of the printed circuit board. For example, the heat dissipation pattern is a portion extending from the narrow portion. Thereby, the temperature rise of the shunt resistance portion can be suppressed. Therefore, it becomes possible to increase the allowable calorific value shown in FIG. 2.

[0027] FIG. 3 shows the shunt resistor 100 of the present embodiment. According to FIG. 3, a conductor pattern 200 made of copper foil or the like formed on a conductor layer CL in a printed circuit board PB including a base material layer BL and a conductor layer CL laminated directly or indirectly on the base material layer BL has an energization path 210, a shunt resistor portion 230 which is a part of the energization path 210, and one heat dissipation pattern portion 270 formed thereon, and further a voltage detection pattern 250 is also formed. Note that the heat dissipation pattern portion 270 is not limited to one. The shunt resistor portion 230 is a constricted portion where the cross-sectional area in a plane (not shown) orthogonal to the energization direction D in which the energization current I flows is smaller than other portions (of the energization path 210) between the energization path input side 210IN and the energization path output side 210OU of the energization path 210 through which the energization current I flows. In this way, the shunt resistor portion 230 has a larger resistance value than other portions of the energization path 210 for use as a shunt resistor.

[0028] The printed circuit board PB shown in FIG. 3 further includes a detection unit 300 that detects the voltage of the shunt resistor portion 230 measured through the voltage detection pattern 250. In the present embodiment, the detection unit 300 incorporates an ADC (analog-to-digital converter) and an amplification circuit that amplifies the detected value. The voltage detected by the detection unit 300 is calculated and processed by a processing control unit 400 as described later, and a control signal CS for controlling a subsequent functional unit is output from the processing control unit 400.

[0029] Assuming that the resistance value of the shunt resistor portion 230 is r [Ω] and the current value of the energizing current I flowing through the energization path 210 is a [A], the voltage drop value (energization voltage value) v generated in the shunt resistor portion 230 at this time is v = a × r [V]. This voltage is detected by the detection unit 300 through the voltage detection pattern 250 as described above. Also, the heat generation amount q of the shunt resistor portion 230 at this time is q = a × v [W]. Here, it is necessary to release the heat generated by the shunt resistor portion 230 to the outside to suppress the temperature rise of the shunt resistor portion 230. Therefore, this heat generation is dissipated from the heat dissipation pattern portion 270, which is a portion extending from the narrow portion that is the shunt resistor portion 230 in the conductor pattern 200 formed on the conductor layer CL and through which the energizing current I does not flow. Thus, in the present embodiment, the heat generated by the shunt resistor portion 230 is transmitted to the heat dissipation pattern 270 and released to the atmosphere through the heat dissipation pattern 270, and is also propagated to other parts of the printed circuit board and released to the atmosphere. Thereby, the temperature rise of the shunt resistor portion 230 can be suppressed. The heat dissipation pattern 270 is made of a metal suitable for heat dissipation and is configured as the conductor pattern 200, so that the heat generated in the printed circuit board can be propagated and contribute to heat dissipation, and further has the advantage of not affecting the energizing current I. Note that the heat dissipation pattern 270 is preferably a planar copper foil or the like extending from the narrow portion in terms of heat dissipation.

[0030] Here, in the shunt resistor portion 230 of FIG. 3, there are variations in the thickness of the copper foil, the pattern width of the shunt resistor portion 230, etc., and variations may occur with respect to the target (desired) shunt resistance value. Depending on the application to which the shunt resistor 100 is applied, the above variations may not be acceptable. Therefore, a method for correcting this shunt resistance value will be described.

[0031] The above correction method will be described by taking, as an example, a control device incorporated in a printed circuit board PB having a shunt resistor 100 as shown in FIG. 4. This control device CT includes the detection unit 300 that detects the energization voltage value in the shunt resistor portion 230, and the processing control unit 400 that outputs a control signal CS using the energization voltage value detected by the detection unit 300.

[0032] This control device CT further includes a switching unit 500 that switches between a conduction current I from the conduction path input side 210IN and a specified current PS that is a constant (fixed) value current such as 5A, and a correction unit 600 that performs a correction calculation of the conduction voltage value v in the shunt resistor unit 230. After the switching unit 500 switches from the conduction current I to the specified current PS, this correction unit 600 performs a correction calculation of the conduction voltage value v using the reference voltage value vr after the reference voltage value vr is detected by the detection unit 300. That is, according to a command from the processing control unit 400 or the like, the switching unit 500 switches the current flowing through the shunt resistor unit 230 from the conduction current I to the specified current PS (for example, 5A). In the detection unit 300, the detection value (analog value) at that time is AD-converted (analog-to-digital converted) and amplified, and the reference voltage value vr[v] is obtained from the detection value and the amplification factor at this time, and the reference shunt resistance value rr[Ω] is calculated. The shunt resistance value r[Ω] is corrected using this reference shunt resistance value rr[Ω] to calculate the conduction current I, which is used for the calculation of the control signal CS. Note that, instead of calculating the reference shunt resistance value rr[Ω], the conduction voltage value v may be corrected using the reference voltage value vr to calculate the shunt resistance value r[Ω].

[0033] Next, a method for reducing the above variations to obtain a desired shunt resistance value will be described below. As shown in FIG. 5, a notch (shunt resistance cut line) 240 is provided in the narrow portion that is the shunt resistance portion 230. Specifically, while checking the resistance value of the shunt resistance portion 230, the shunt resistance portion 230 is pattern-cut using a laser or the like to form the shunt resistance cut line 240. At this time, for example, the shunt resistance cut line 240 is provided so as to extend in a direction orthogonal to the energization direction D in which the energization current I flows. In order to ensure the length of the pattern cut, in the substrate pattern of the shunt resistance portion 230, it is preferable that the width direction orthogonal to the energization direction D is thickened in advance. Since the cross-sectional area of the shunt resistance portion 230 in the plane orthogonal to the energization direction D in which the energization current I flows can be adjusted by this shunt resistance cut line 240, and also the energization length in which the energization current I flows through the shunt resistance portion 230 can be extended and adjusted, variations with respect to the target (desired) shunt resistance value can be reduced.

[0034] Note that the shunt resistance cut line 240 is preferably cut from a position opposite to the portion where the heat dissipation pattern 270 is connected to the shunt resistance portion 230. With this configuration, while reducing the influence on heat transfer to the heat dissipation pattern 270 due to the notch, the notch portion 240 that exhibits the above effects can be provided. That is, the heat dissipation pattern 270 will exist on the side opposite to the side where the notch portion (shunt resistance cut line) 240 exists with respect to the narrow portion (shunt resistance portion) 230. In FIG. 5, there are three heat dissipation patterns 270A to 270C for the heat dissipation pattern 270, and the notch portions (shunt resistance cut lines) 240 have three shunt resistance cut lines 240A to 240C at positions opposite to each of the heat dissipation patterns 270A to 270C with respect to the narrow portion (shunt resistance portion) 230. By performing the pattern cut at these three locations, variations in the shunt resistance can be suppressed while suppressing the temperature. Note that the shunt resistance cut line is not limited to these three locations.

[0035] With the above configuration, at least as shown in FIG. 3, it is possible to suppress the temperature rise of the shunt resistor portion 230 formed on the printed circuit board PB. As a result, it becomes possible to handle a large allowable heat generation amount. Further, it is possible to suppress variations in the shunt resistance value, and it becomes possible to meet more precise requirements.

[0036] As described above, the mode for carrying out the present invention has been described based on the embodiments. However, the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0037] 100 Shunt resistor 200 Conductor pattern 210 Current path 210IN Input side of current path 210OU Output side of current path 230 Shunt resistor portion (narrow portion) 240, 240A, 240B, 240C Notch portion 270, 270A, 270B, 270C Heat dissipation pattern 300 Detection unit 400 Processing control unit 500 Switching unit 600 Correction unit BL Base material layer CL Conductor layer CT Control device D Current direction I Current PB Printed circuit board

Claims

1. In a printed circuit board including a base material layer and a conductor layer directly or indirectly laminated on the base material layer, in the conductor pattern formed on the conductor layer, a shunt resistance portion is configured by a narrow portion where the cross-sectional area in a plane perpendicular to the energization direction of the energization current is smaller than other portions between the energization path input side and the energization path output side of the energization path through which the energization current flows. Shunt resistance.

2. The shunt resistance according to Claim 1, wherein in the conductor pattern formed on the conductor layer, a heat dissipation pattern is provided in a portion extending from the narrow portion and where the energization current does not flow. Shunt resistance.

3. The shunt resistance according to Claim 2, wherein a notch portion is provided in the narrow portion. Shunt resistance.

4. The shunt resistance according to Claim 3, wherein the notch portion is provided in the narrow portion so as to extend in a direction perpendicular to the energization direction. Shunt resistance.

5. The shunt resistance according to Claim 4, wherein the heat dissipation pattern exists on the side opposite to the side where the notch portion exists with respect to the narrow portion. Shunt resistance.

6. A step of manufacturing a printed circuit board by directly or indirectly laminating a conductor layer on a base material layer, and a step of forming a conductor pattern on the conductor layer, including: in the step of forming the conductor pattern, a step of forming a narrow portion where the cross-sectional area in a plane perpendicular to the energization direction of the energization current is smaller than other portions between the energization path input side and the energization path output side of the energization path through which the energization current flows. Method for manufacturing a shunt resistance.

7. A shunt resistance according to any one of Claims 1 to 5, a detection unit that detects an energization voltage value in the shunt resistance, and a processing control unit that outputs a control signal using the energization voltage value detected by the detection unit. Control device comprising the same.

8. The control device according to Claim 7, wherein a switching unit that switches between the energization current from the energization path input side and a specified current, and a correction unit that performs a correction calculation of the energization voltage value in the shunt resistance are provided, and the correction unit performs a correction calculation of the energization voltage value using the reference voltage value after the reference voltage value is detected by the detection unit after the switching unit switches from the energization current to the specified current. Control device.

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