Current sensor

• US 7,573,274 B2
• Filed: 07/17/2007
• Issued: 08/11/2009
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Aratani, Masahiro
• Primary Examiner(s): Nguyen; Vincent Q
• Application Number:
  US11/826,555
• Publication Number:
  US 20080030208A1
• Time in Patent Office: 756 Days
• Field of Search: 324/426, 324/713, 324/117.R, 324/117.H
• US Class Current: 324/713
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/364 Battery terminal connectors with integrated measuring arrangements
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01R 11/287 Intermediate parts between battery post and cable end piece
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A current sensor includes a busbar, a case, a connector, and a bare chip having a current detection circuit. The busbar has a crimp terminal at one end, a ring terminal at the other end, and a shunt resistor welded between the crimp and ring terminals. The shunt resistor is encapsulated in the case, and the busbar has an electrode exposed to a sealed inner room of the case. The connector has a connector body unitary with the case and has a connector terminal that is exposed to the inner room at one end and exposed to an outside of the connector body at the other end. The bare chip is arranged in the inner room of the case and wire-bonded to each of the busbar and the connector terminal.

Claims

1. A current sensor for measuring an electric current flowing through a current line, the current sensor comprising:

an electrically conductive busbar interposable in the current line to allow the electric current to flow through the busbar, the busbar having a first end portion connectable to a first side of the current line, a second end portion connectable to a second side of the current line, and a middle portion that joins the first and second end portions;

an electrically nonconductive case including a case body and a case lid, the case body encapsulating the middle portion of the busbar and having an inner room, the case lid being attached to the case body to cover the inner room;

a connector including a connector body and a connector terminal supported in the connector body, the connector body being joined to the case body, the connector terminal having a first portion exposed to the inner room of the case body and a second portion exposed to an outside of the connector body to be connectable to an external device;

a semiconductor bare chip arranged in the inner room of the case body and having a detection circuit that detects the electric current based on a resistance of the busbar and a voltage drop across the busbar, the detection circuit outputting a data signal indicative of the detected electric current to the external device via the connector;

a first bonding wire that electrically couples the bare chip to the busbar; and

a second bonding wire that electrically couples the bare chip to the first portion of the connector terminal of the connector.

2. The current sensor according to claim 1, wherein

the connector body of the connector is unitary with the case body of the case.

3. The current sensor according to claim 1, further comprising:

an adhesive, wherein

the case body of the case has a first engagement portion around its perimeter to surround an opening of the inner room,

the case lid of the case has a second engagement portion around its perimeter,

the first and second engagement portions are engaged with each other, and

the adhesive is placed between the first and second engagement portions so that the inner room of the case body is sealed by the case lid in a liquid-tight manner.

4. The current sensor according to claim 1, wherein

the case body has a first air passage communicating with the inner room,

the connector body has a second air passage communicating with the outside of the connector body, and

the first and second air passages communicate with each other.

5. The current sensor according to claim 1, wherein

the busbar has an electrode exposed to the inner room of the case body,

the electrode includes a first electrode portion and a second electrode portion, and

the first electrode portion is electrically coupled to the bare chip by the first bonding wire.

6. The current sensor according to claim 5, further comprising:

a first sealing member for covering the second electrode portion of the electrode.

7. The current sensor according to claim 1, further comprising:

a second sealing member for at least partially filling the inner room of the case body.

8. The current sensor according to claim 1, wherein:

the middle portion of the busbar is welded between the first and second end portions of the busbar,

each of the first and second end portions of the busbar has a low electrical resistance, and

the middle portion of the busbar is a shunt resistor having a low temperature coefficient of resistance.

9. The current sensor according to claim 8, wherein

the bare chip is arranged away from the shunt resistor.

10. The current sensor according to claim 1, wherein

the first end portion of the busbar has a crimp terminal, and

the second end portion of the busbar has a ring terminal.

11. The current sensor according to claim 1, wherein

the first end portion of the busbar has a bolt, and

the second end portion of the busbar has a ring terminal.

12. The current sensor according to claim 1, wherein

each of the first and second end portions of the busbar has a ring terminal.

13. The current sensor according to claim 1, further comprising:

a snap fit provided near the first end portion of the busbar and attachable to an object where the current sensor is mounted.

14. The current sensor according to claim 1, wherein

the busbar has a heat radiator.

15. The current sensor according to claim 1, wherein

the busbar is at least partially plated with a corrosion resistant material.

16. The current sensor according to claim 1, wherein

the current line connects a metallic part of a vehicle and an negative electrode of a battery installed in the vehicle.