Current detecting device

A current detecting device includes a second fixed part to which the harness is fixed and electrically connected, a bus bar as a resistor inserted between a first fixed part and the second fixed part, a circuit board in which a current detection circuit is mounted, the current detection circuit detecting current flowing through the bus bar based on a potential difference between two points along an energizing direction of the bus bar, and a case accommodating the bus bar and the circuit board. The second fixed part to which the harness is fixed and electrically connected is disposed within a battery upper surface area.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from earlier Japanese Patent Applications No. 2010-17876 filed Jan. 29, 2010 and No. 2010-152685 filed Jul. 5, 2010, the descriptions of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a current detecting device equipped in a passenger car, a truck, etc. that detects charging/discharging current of a battery.

BACKGROUND

A current sensor has been known that is provided with a current detection circuit accommodated within a case in an intermediate portion of a flat bus bar in the length direction (refer to, for example, JP-A-2008-39571).

In the current sensor, the bus bar configures a ground terminal. The current sensor is attached to the negative terminal side of a battery and detects the charging/discharging currents of the battery.

The bus bar of the current sensor disclosed in JP-A-2008-39571 has a long, flat shape to ensure current detection accuracy.

Because a first connecting section and a second connecting section connected to respective attached members are formed at the tips of the bus bar in the length direction, when the distance between the first and second connecting sections is long, moment force is generated against the attached member connected to the first connecting section with the second connecting section as a point of action.

In particular, when a battery terminal is considered as the attached member connected to the first connecting section, excessive moment force is applied to the battery terminal, leading to reduced fastening strength of the battery terminal and damage to the battery terminal.

A problem occurs in that quality and vibration-resistance of the battery terminal may deteriorate during vehicle assembly.

SUMMARY

An embodiment provides a current detecting device capable of improving quality and vibration-resistance of a battery terminal during vehicle assembly.

In a current detecting device that detects a current flowing through a battery terminal to a harness according to a first aspect, the current detecting device includes a fixed part to which the harness is fixed and electrically connected; a resistor inserted between the battery terminal and the fixed part; a circuit board in which a current detection circuit is mounted, the current detection circuit detecting current flowing through the resistor based on a potential difference between two points along an energizing direction of the resistor; and a case housing the resistor and the circuit board.

The fixed part to which the harness is fixed and electrically connected is disposed within a battery upper surface area.

As a result of the fixed part being disposed on the battery upper surface area, even when a load is applied when the harness is fixed to the fixed part, the amount of deflection of the fixed part in the load direction can be reduced. Therefore, excessive moment can be prevented from being applied to the battery terminal.

As a result, reduction in fastening strength of the battery terminal and damage to the battery terminal can be prevented, and the quality and vibration-resistance of the battery terminal during vehicle assembly can be improved.

Furthermore, because the overall current detecting device including the fixed part or the main section thereof is contained within the battery upper surface area, the space on the battery upper surface can be effectively used, and mounting properties are enhanced.

In the current detecting device according to a second aspect, the above-described resistor preferably has a non-linear shape. Specifically, the non-linear shape is a shape that is folded back midway and of which at least a portion is overlapping. Alternatively, the non-linear shape is a C-shape or an L.-shape.

As a result, distance between the battery terminal and the fixed part can be shortened, and moment force applied to the battery terminal when the harness is fixed to the fixed part can be further reduced.

In the current detecting device according to a third aspect, the above-described fixed part is preferably disposed within a circular area that is within the battery upper surface area and has a radius from the center of the battery terminal that is a radius of the battery terminal multiplied by a predetermined value.

Specifically, the above-described predetermined value is preferably 3.5. The moment force applied to the battery terminal when a predetermined fastening force is applied to the fixed part is proportional to the distance between the battery terminal and the fixed part.

On the other hand, when the same moment force is applied as described in the present disclosure, the moment force can be dispersed and received in proportion to a battery terminal diameter. Therefore, reduction in the fastening strength of the battery terminal and damage to the battery terminal can be prevented.

Therefore, as a result of limiting the ratio of the battery terminal diameter to the distance between the battery terminal and the fixed part, the moment force applied to the battery terminal during fastening of the fixed part can be dispersed. The quality and vibration-resistance of the battery terminal can be improved with certainty.

In the current detecting device according to a fourth aspect, the above-described fixed part is preferably any of a bolt that is attached and fixed, an attaching hole that is formed in a penetrating manner, and a crimped terminal.

As a result of forming the fixed part by any of the bolt, the attaching hole, and the crimped terminal, variation of the harness position on the vehicle side can be increased, and attaching properties can be improved.

In the current detecting device according to a fifth aspect, attachment is preferably performed in a state in which the lower surface of the above-described fixed section is in contact with the battery upper surface.

As a result, the amount of deflection of the fixed part when the harness is fixed to the fixed part can be kept to a minimum, and the moment force applied to the battery terminal can be minimized.

Therefore, the quality and vibration-resistance of the battery terminal during vehicle mounting can be further improved.

In the current detecting device according to a sixth aspect, a cut-out section is preferably formed in the above-described case within the battery upper surface area. The battery terminal and the fixed part are each preferably provided such as to oppose the cut-out section.

A terminal provided in the battery within the battery upper surface area is preferably disposed in the cut-out section. Specifically, the battery terminal and the fixed part are each preferably provided in a position adjacent to the cut-out section.

As a result of the cut-out section being provided in the case of the current detecting device, and the terminal of the battery, and the battery terminal and the fixed part of the current detecting device being collectively disposed within or near the cut-out section in this way, the distance between each fastening section thereof can be shortened.

Therefore, the moment force applied during fastening or during use can be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A current detecting device according to an embodiment in which the present disclosure is applied will hereinafter be described in detail with reference to the drawings.

The current detecting device according to the embodiment is, for example mounted on and fixed to a negative-side terminal of a lead battery for a vehicle, and can be used to detect charge and discharge currents of the battery.

FIG. 1is a cross-sectional view of a configuration of the current detecting device according to the embodiment, showing a state in which the current detecting device is attached to the battery.FIG. 2is a cross-sectional view taken along line II-II inFIG. 1.

A current detecting device100according to the embodiment shown in the drawings includes: a bus bar110serving as a resistor (shunt resistor) formed using a conductive material; a circuit board120on which a current detection circuit is mounted, the current detection circuit detecting a current flowing through the bus bar110based on a potential difference between two points along the energizing direction of the bus bar110; a case130housing the bus bar110and the circuit board120; a connector140, inside of which a plurality of connector terminals142are exposed, the connector terminals142being electrically connected with the circuit board120; and a lid150that seals an opening of a recess in the case130housing the circuit board120.

The bus bar110is shaped such as to be folded back and overlapping within the case130.

One end of the bus bar110forms a first fixed section112that is fixed to an attachment fitting serving as a connection terminal on the battery200side and electrically connected.

The other end of the bus bar110forms a second fixed section114that is fixed to a harness and electrically connected. The bus bar110is formed by press-molding a single plate-shaped member.

According to the present embodiment, the main section (the section housing the circuit board120) of the case130having an overall rectangular shape is disposed near a side surface of the battery200(the side surface closest to a terminal202of the battery200to which the current detecting device100is attached) such as to project vertically.

The remaining section (the section in which the first and second fixed parts112and114are formed) is disposed on an upper surface200A of the battery200.

The first fixed part112has a flat shape. A through-hole is formed in a portion of the flat shape. A nut112A is fixed to the upper side of the through-hole. On the other hand, as shown inFIG. 1, an attachment fitting210is attached to the negative-side terminal202of the battery200.

The attachment fitting210serves both to attach the current detecting device100and as a wiring between the negative-side terminal202and the first fixed part112. A through-hole for inserting a bolt211in the upward direction is provided in the end of the attachment fitting210.

According to the embodiment, the bolt211is inserted upward through the through-hole in the attachment fitting210. The bolt211is then inserted into the nut112A in a state in which the attachment fitting210and the flat-shaped portion of the first fixed part112are sandwiched therebetween, and the first fixed part112is fastened and fixed to the attachment fitting210. Then, the attachment fitting210is attached to the negative-side terminal202of the battery200.

In addition, a through-hole is provided near the end of the second fixed part114. A bolt115is inserted into the through-hole. On the other hand, a terminal302having a through-hole is provided at the end of a harness300that is electrically connected to the second fixed part114.

The bolt115provided in the second fixed part114is inserted into the through-hole in the terminal302. The terminal302is fastened with a nut (not shown), thereby fixing the terminal302to the second fixed part114.

According to the present embodiment, the case130is formed by a resin material having favorable insulation and heat-transmission properties, such as PPS (Polyphenylenesulfide). The bus bar110is insert-molded using the resin material.

Next, the position of the second fixed part114will be described. As described above, the second fixed part114is disposed within an area (battery upper surface area) of the upper surface200A of the battery200in which the harness300is fixed and electrically connected. The second fixed part114is disposed in a position overlapping the first fixed part112.

As a result of the second fixed part114being disposed on the battery upper surface area in this way, even when a load is applied to the second fixed part114when the harness300is fixed, the amount of deflection of the second fixed part114in the load direction can be suppressed.

Therefore, excessive moment can be prevented from being applied to the first fixed part112serving as a battery terminal. As a result, reduction in the fastening strength of the first fixed part112and damage to the first fixed part112can be prevented, and quality and vibration-resistance of the battery terminal during vehicle assembly can be improved.

Further, because the overall current detecting device100including the second fixed part114or the main section thereof is contained within the battery upper surface area, space on the battery upper surface200A can be effectively used, and mounting properties are improved.

Furthermore, although workability, such as battery replacement, deteriorates when auxiliary machines are mounted in the space on the battery upper surface200A, when the current detecting device100is mounted, the attachment fitting210is removed when battery replacement or the like is performed.

Therefore, the current detecting device100can be removed at the same time, and deterioration of workability does not particularly occur.

FIG. 3is a diagram of a specific example of the circuit in the current detecting device100, and an example of connection with the battery200or the like.

As shown inFIG. 3, the circuit board120of the current detecting device100includes: a differential amplifier10connected to both ends of a shunt resistor100′ serving as a resistor formed by a portion of the bus bar110; a differential amplifier12connected to the positive terminal and the negative terminal of the battery200; a temperature detecting section20; a current detection processing section30; a voltage detection processing section32; a temperature detection processing section34; a battery status detecting section36; a charge controlling section40; communication input and output section (communication I/O)50and52; a CAN interface (CAN I/F)60that transmits and receives data based on CAN protocol; and a LIN interface (LIN I/F)62that transmits and receives data based on LIN protocol.

One differential amplifier10amplifies the voltage across the shunt resistor100′. The current detection processing section30detects the current flowing to the shunt resistor100′ based on the output voltage of the differential amplifier10.

The differential amplifier10and the current detection processing section30configure a current detection circuit. The other differential amplifier12converts the voltage across the battery200(battery voltage) to an appropriate level. The voltage detection processing section32detects the battery voltage based on the output voltage of the differential amplifier12.

The temperature detecting section20is configured by a voltage divider circuit composed of a resistor and a thermistor. The resistance value of the thermistor changes depending on the temperature and the divided voltage of the voltage divider circuit changes.

The temperature detection processing section34detects the temperature of the current detecting device100(temperature of the battery200) based on the output voltage (divided voltage) of the temperature detecting section20.

The battery status detecting section36loads the detection values of the current detection processing section30, the voltage detection processing section32, and the temperature detection processing section34, and generates a battery status signal.

The current detection processing section30, the voltage detection processing section32, the temperature detection processing section34, and the battery status detecting section36configure a status detection sensor38.

The charge controlling section40controls a power generation state of a vehicle power generator (G)80based on the battery status signal generated by the battery status detecting section36.

The power generation control is performed by an instruction being sent to a power generation controlling device82mounted in the vehicle power generator80, via the communication I/O52and the LIN I/F62.

The battery status signal generated by the battery status detecting section36is sent to a vehicle system via the communication I/O50and the CAN I/F60.

The vehicle system70performs integrated control of an engine and various electrical loads based on the received battery status signal and the like.

The differential amplifier10and the current detection processing section30, described above, configure the current detection circuit.

According to the above-described embodiment, the second fixed part114and the first fixed part112are disposed in positions such as to overlap with each other in the up-down direction. However, the positions may be shifted within a predetermined range.

Furthermore, the first fixed part112may be directly attached to the negative side terminal220of the battery200without the attachment fitting210therebetween.

FIG. 4is a cross-sectional view of a configuration of a variation example of the current detecting device. A current detecting device100A shown inFIG. 4differs from the current detecting device100shown inFIG. 1in that the attachment fitting210and the first fixed part112shown inFIG. 1are integrally formed and, as a whole, form a first fixed part212.

In the current detecting device100A, when a fastening force is applied to the bolt115of the second fixed part114and a load is applied in the vertical direction when the harness300is attached, the second fixed part114becomes a point of action, and the first fixed part212attached to the negative side terminal202of the battery200becomes a point of support.

The respective positions of the first and second fixed parts212and114are set such that the center of the second fixed part114is disposed within a circular area that, from the center of the first fixed part212, has a radius that is the radius of the first fixed part212(radius of the negative-side terminal202) multiplied by a predetermined value. Specifically, the predetermined value is preferably 3.5.

When a predetermined fastening force is applied to the second fixed part114, the moment force applied to the first fixed part212is proportional to the distance between the first fixed part212and the second fixed part114.

On the other hand, when the same moment force is applied, the moment force can be dispersed and received in proportion to the diameter of the first fixed part212(diameter of the negative-side terminal202).

Therefore, reduction in the fastening strength of the first fixed part212and damage to the first fixed part212can be suppressed.

Therefore, by limiting the ratio of the diameter of the first fixed part212to the distance between the first fixed part212and the second fixed part114, the moment force applied to the first fixed part212when the second fixed part114is fastened can be dispersed.

As a result, quality and vibration-resistance of the first fixed part212can be improved with certainty.

With the distance between the first fixed part212and the second fixed part114set to L, when the moment applied to the battery terminal in relation to (distance L/battery terminal radius) is actually determined, the moment becomes greater in proportion to (distance L/battery terminal radius).

It has been confirmed that, when (distance L/battery terminal radius) exceeds 3.5, the allowable moment in relation to damage to the battery terminal is exceeded.

FIG. 5is a planar view of another variation example of the current detecting device. A current detecting device100B shown inFIG. 5is disposed such that a large portion of the case130, excluding the connector140, and a circuit board120A accommodated therewithin are each parallel with the upper surface200A of the battery200.

Unlike the bus bar110shown inFIG. 1and the like, a bus bar110A serving as a resistor has a C-shape rather than the folded shape. A current detecting circuit of the circuit board120A detects the current flowing to the bus bar110A based on the electrical potential at two points near both ends of the C-shaped bus bar110A.

In the current detecting device100B, the respective positions of the first and second fixed parts212and114are set such that the center of the second fixed part114is disposed within a circular area that, from the center of the first fixed part212is the radius of the second fixed part114multiplied by a predetermined value (preferably 3.5, as described above).

As a result, the moment force applied to the first fixed part212when the harness300is attached to the second fixed part114can be reduced, and quality and vibration-resistance of the first fixed part212can be improved with certainty. In particular, as a result of the bus bar11A being formed into the C-shape, the distance between the first and second fixed parts212and114can be shortened.

FIG. 6AtoFIG. 6Care diagrams of overall configurations of other variation examples of the current detecting device. InFIG. 6AtoFIG. 6C, the positional relationship between the first and second fixed parts, and a rough shape of the bus bar serving as a resistor are shown.

In the example shown inFIG. 6A, a current detecting device100C having an L-shaped bus bar110C is attached to the attachment fitting210attached to the negative-side terminal202. The first and section fixed parts112and114are both disposed on the battery upper surface area.

In the example shown inFIG. 6B, a current detecting device100D having an L-shaped bus bar110D is directly attached to the negative-side terminal202. The first and second fixed parts212and114are both disposed on the battery upper surface area.

In the example shown inFIG. 6C, a current detecting device100E having a linear bus bar110E that is folded back at two points is attached to the attachment fitting210attached to the negative-side terminal202. The first and second fixed parts112and114are both disposed on the battery upper surface area.

FIG. 7AandFIG. 7Bare diagrams of another variation example of the current detecting device.FIG. 7Ais a perspective view of the variation example of the current detecting device.FIG. 7Bis a diagram of the variation example of the current detecting device viewed from the upper surface200A of the battery200.

As shown inFIG. 7AandFIG. 7B, a cut-out section132is provided in the case130of a current detecting device100F of the variation example, in a position corresponding to the interior of the battery upper surface area.

The first fixed part112and the second fixed part114are disposed in an area opposing the cut-out section132(adjacent area). In addition, the negative-side terminal202of the battery200is disposed within the cut-out section132. The second fixed part114and the negative-side terminal202are connected with the attachment fitting210therebetween (not shown inFIG. 7AandFIG. 7B).

As a result of the cut-out section132being provided in the case130of the current detecting device100F, and the negative-side terminal202, the first fixed part112, and the second fixed part114being collectively disposed within or near the cut-out section132in this way, the distances between each fastening section thereof becomes short.

Therefore, the moment force applied to each section of the current detecting device100F during fastening or during use can be reduced.

The present disclosure is not limited to the above-described embodiment. Various modifications can be made without departing from the spirit of the present disclosure. According to the above-described embodiment, when the bus bar100or the like is integrated with a resistor is described. However, a resistor separate from the bus bar100or the like may be used.

According to the above-described embodiment, the second fixed part114to which the bolt115is attached and fixed is described. However, the present disclosure can also be applied to when the second fixed part is formed by an attachment hole being formed in a penetrating manner, or when the second fixed part is formed by a crimped terminal.

According to the above-described embodiment, when a portion of the current detecting device100or the like is disposed in an area other than the upper surface200A of the battery200is described. However, the entire current detecting device100or the like may be disposed on the battery upper surface area.

Furthermore, attachment may be performed in a state in which the lower surface of the second fixed part114(the lower surface of a head portion of the bolt211of the attachment fitting210to which the first fixed part112directly below the second fixed part114is attached, in the example shown inFIG. 1) is in contact with the battery upper surface200A.

As a result, the amount of deflection of the second fixed part114to the lower side when the harness300is fixed to the second fixed part114can be kept to a minimum, and the moment force applied to the first fixed part112can be minimized.

As a result, further improvement in the quality and vibration-resistance of the first fitting section112can be achieved.

As described above, in the present disclosure, as a result of the second fixed part114being disposed on the battery upper surface area, even when a load is applied when the harness300is fixed to the second fixed part114, the amount of deflection of the second fixed part114in the load direction can be reduced.

Therefore, excessive moment can be prevented from being applied to the first fitting section112. As a result, reduction in fastening strength of the first fixed part112and damage to the first fixed part112can be prevented, and the quality and vibration-resistance of the second fixed part114during vehicle assembly can be improved.

Furthermore, because the overall current detecting device100including the second fixed part114or the main section thereof is contained within the battery upper surface area, the space on the battery upper surface200A can be effectively used, and mounting properties are enhanced.