TECHNICAL FIELD

The present invention relates to a physical quantity detection device that detects a physical quantity of intake air of an internal combustion engine, for example.

BACKGROUND ART

For example, in a configuration of a thermal type flowmeter disclosed in PTL 1, a measuring unit protrudes from an inner wall of an intake passage toward a center of a passage, a sub-passage in which a flow is taken is disposed in the measuring unit, and a circuit board is disposed so as to straddle the bent sub-passage. The above conventional device proposes a low-pressure-loss physical quantity detection device in which the circuit board is efficiently disposed in the sub-passage to reduce a size in a longitudinal direction of the measuring unit.

For example, in a configuration of a thermal type flowmeter disclosed in PTL 2, the measuring unit protrudes from the inner wall of the intake passage toward the center of the passage, the circuit board is disposed on an upstream side of the measuring unit so as to be perpendicular to a flow of a main passage, and the sub-passage is disposed on a downstream side of the measuring unit. The above conventional device proposes a low-pressure-loss physical quantity detection device in which the circuit board and the sub-passage are disposed in parallel with the measuring unit to reduce the size in the longitudinal direction of the measuring unit.

CITATION LIST

Patent Literature

PTL 1: Japanese Patent No. 4968267

PTL 2: EP 2029976 A1

SUMMARY OF INVENTION

Technical Problem

A mounting method for being able to reduce a height by efficiently disposing the circuit board and the sub-passage is proposed in the above conventional device. For example, when the detection functions of an intake air temperature sensor, a humidity sensor, a pressure sensor, and the like are made multifunctional, the size of the circuit board is enlarged due to the increase in the numbers of control circuits, protection circuits, and circuit wires and addition of an electronic component, which results in an influence on size maintenance of the measuring unit.

In the configuration described in PTL 1, the pressure loss in the sub-passage increases by an increase in the number of circuit boards, which results in degradation of flow speed sensitivity of the flow sensor. When various sensors are installed in the circuit board, the various sensors become an obstacle, and there is a risk that noise performance and a pulsation characteristic of the flow sensor are degraded due to turbulence of a fluid.

In the configuration described in PTL 2, although the size in the longitudinal direction of the measuring unit can be maintained, the size in the thickness direction of the measuring unit is enlarged due to the increase in the number of circuit boards, which results in an increase in pressure.

The present invention has been made in view of the above points, and an object of the present invention is to provide a low-pressure-loss physical quantity detection device that can detect a plurality of physical quantities of intake air.

Solution to Problem

According to one aspect of the present invention, a physical quantity detection device that detects a plurality of physical quantities of a measured gas flowing in a main passage, the physical quantity detection device includes: a circuit board on which a sensor that detects the plurality of physical quantities and an electronic component that controls the physical quantities can be mounted; a circuit board accommodating unit accommodating the circuit board; and a sub-passage in which a flow sensor is disposed. The circuit board is accommodated in the circuit board accommodating unit on an upstream side of the sub-passage, and disposed in parallel with the measured gas flowing through the main passage.

Advantageous Effects of Invention

In the present invention, the sizes in the longitudinal direction and the thickness direction can be maintained and reduced, and a multifunction can be achieved while performance is ensured. Thus, the present invention is to provide a low-pressure-loss physical quantity detection device that can detect a plurality of physical quantities of intake air.

Further features associated with the present invention will become apparent from the description of the present description and the accompanying drawings. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

