BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic sensor device including a magnetic detection element and a conductor that generates a magnetic field.

2. Description of the Related Art

Magnetic sensor devices in which a magnetic detection element and a coil for generating a magnetic field are integrated have recently been used for various applications. The coil is used for such purposes as cancelling out another magnetic field applied to the magnetic detection element, setting the magnetic detection element to a desired state, and resetting the magnetic detection element.

EP 3130929 A1 describes a current detection device using a magnetic sensor device in which a magnetic detection element and a coil are integrated. The current detection device according to EP 3130929 A1 is a so-called magnetic balance type current sensor. In the magnetic balance type current sensor, the coil of the magnetic sensor device is used as a feedback coil. The feedback coil generates a second magnetic field that cancels out a first magnetic field generated by a current to be detected flowing through a conductor. The magnetic detection element detects a composite magnetic field of the first magnetic field and the second magnetic field. A feedback coil current depending on a detection value of the magnetic detection element flows through the feedback coil so that the composite magnetic field approaches zero. The magnetic balance type current sensor is configured to be able to detect a detection value of the feedback coil current (hereinafter, also referred to as a current detection value). The current detection value is proportional to the value of the current to be detected. The current detection value therefore corresponds to the detection value of the current to be detected.

In EP 3130929 A1, the feedback coil is described to include an element facing portion opposed to the magnetic detection element and a portion other than the element facing portion. In addition, the width dimension of a coil line in the element facing portion is described to be reduced compared to that of the coil line in the portion other than the element facing portion.

U.S. Pat. No. 5,952,825 A describes a coil (conductor) that generates a magnetic field at a position of a magnetoresistive element for the purpose of cancelling or balancing out an external magnetic field, and a coil (conductor) that sets or resets magnetic domains of the magnetoresistive element. According to U.S. Pat. No. 5,952,825 A, the coils have a relatively large width in portions facing the magnetoresistive element and a relatively small width in portions not facing the magnetoresistive element.

US 2013/0320972 A1 describes a coil (flip conductor) that applies a flip magnetic field for flipping the internal magnetization of a magnetic field sensing element. US 2013/0320972 A1 also describes arranging flip conductor stripes having a relatively small width at the end parts of magnetic field sensing elements and a relatively large width at the center portions of the magnetic field sensing elements.

US 2014/0300348 A1 describes a coil that generates a magnetic field for initializing a magnetoresistive sensor element and a magnetic field for calibrating the magnetoresistive sensor element. According to US 2014/0300348 A1, a width of the coil in a portion facing magnetoresistive sensor elements is greater than or equal to that in a portion not facing the magnetoresistive sensor elements.

Suppose that a coil is used for the purpose of cancelling another magnetic field to be applied to a magnetic detection element. In such a case, depending on the strength of another magnetic field, another magnetic field can fail to be fully cancelled out unless the magnetic field generated by the coil has sufficient strength. To increase the strength of the magnetic field capable of cancellation, the current density in the coil needs to be increased. Similarly, if a coil is used for the purpose of setting a magnetic detection element to a desired state or resetting the magnetic detection element, the current density in the coil needs to be increased to apply a magnetic field of sufficient strength to the magnetic detection element.

The current density can be increased, for example, by reducing the width of the conductor constituting the coil. However, reducing the width of the conductor of the entire coil increases the resistance of the coil, whereby power consumption and the amount of heat generation are increased.

As described above, EP 3130929 A1 describes making the width dimension of the coil line in the element facing portion smaller than that of the coil line in the portion other than the element facing portion. However, the feedback coil described in EP 3130929 A1 is not capable of a sufficient reduction in resistance, since the proportion of the element facing portion to the entire feedback coil is relatively high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetic sensor device including a magnetic detection element and a conductor that generates a magnetic field, wherein the resistance of the conductor can be reduced while increasing the strength of the magnetic field applied to the magnetic detection element.

A magnetic sensor device according to the present invention includes a magnetic detection element that detects an external magnetic field, and a conductor through which a current flows. The conductor includes a first conductor portion and a second conductor portion that extend continuously when viewed in one direction. A cross-sectional area of the conductor perpendicular to a direction in which the current flows changes from the first conductor portion to the second conductor portion. An average cross-sectional area of the conductor in the first conductor portion is smaller than that of the conductor in the second conductor portion. The first conductor portion is located at a position where a first partial magnetic field occurring from the first conductor portion due to the current is applied to the magnetic detection element. The second conductor portion is located at a position where a second partial magnetic field occurring from the second conductor portion due to the current is not applied to the magnetic detection element, or a position where the second partial magnetic field applied to the magnetic detection element has strength lower than that of the first partial magnetic field applied to the magnetic detection element.

In the magnetic sensor device according to the present invention, the conductor may further include a third conductor portion located on a side opposite to the second conductor portion with respect to the first conductor portion. The first to third conductor portions may extend continuously when viewed in one direction. The cross-sectional area of the conductor perpendicular to the direction in which the current flows may change from the first conductor portion to the third conductor portion. The average cross-sectional area of the conductor in the third conductor portion may be greater than that of the conductor in the first conductor portion. The third conductor portion is located at a position where a third partial magnetic field occurring from the third conductor portion due to the current is not applied to the magnetic detection element, or a position where the third partial magnetic field applied to the magnetic detection element has strength lower than that of the first partial magnetic field applied to the magnetic detection element.

The magnetic sensor device according to the present invention may be used as a current sensor that detects a current to be detected. In such a case, the conductor may constitute a coil for generating a second magnetic field that cancels out a first magnetic field generated by the current to be detected. The magnetic detection element detects a composite magnetic field of the first magnetic field and the second magnetic field. The magnetic detection element may be a magnetoresistive element.

In the magnetic sensor device according to the present invention, the magnetic detection element may be a magnetoresistive element. The magnetoresistive element includes a magnetization pinned layer having a first magnetization whose direction is fixed, and a free layer having a second magnetization whose direction is variable depending on the external magnetic field. The conductor may constitute a coil for generating a magnetic field that sets the direction of the second magnetization of the free layer to a predetermined direction. In such a case, the magnetic sensor device may further include a support member that supports the magnetic detection element. The support member includes a top surface opposed to the magnetic detection element and a bottom surface located opposite to the top surface. The top surface of the support member may include an inclined portion inclined relative to the bottom surface. The magnetic detection element, at least a part of the first conductor portion, and at least a part of the second conductor portion may be located on the inclined portion. A thickness of the conductor in a direction perpendicular to the bottom surface of the support member may change from the first conductor portion to the second conductor portion. An average thickness of the conductor in the first conductor portion may be smaller than that of the conductor in the second conductor portion.

The magnetic sensor device according to the present invention includes the conductor through which the current flows. The conductor includes the first conductor portion and the second conductor portion. In the present invention, the average cross-sectional area of the conductor in the first conductor portion is smaller than that of the conductor in the second conductor portion. Moreover, in the present invention, the first conductor portion is located at a position where the first partial magnetic field occurring from the first conductor portion is applied to the magnetic detection element. The second conductor portion is located at a position where the second partial magnetic field occurring from the second conductor portion is not applied to the magnetic detection element, or a position where the second partial magnetic field applied to the magnetic detection element has strength lower than that of the first partial magnetic field applied to the magnetic detection element. According to the present invention, the resistance of the conductor can thus be reduced while increasing the strength of the magnetic field applied to the magnetic detection element.

Other and further objects, features and advantages of the present invention will appear more fully from the following description.

