Ultrasonic sensor

Patent metadata

Field	Value
Publication number	US-11667247-B2
Application number	US-202016922030-A
Country	US
Kind code	B2
Filing date	Jul 7, 2020
Priority date	Jul 10, 2019
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

Abstract

An ultrasonic sensor includes: an ultrasonic element provided to transmit or receive an ultrasonic wave propagating along a directional axis; and an element housing case that includes a case diaphragm having a thickness direction along the directional axis. A resonant space is defined between the case diaphragm and the ultrasonic element for the propagating wave, by housing the ultrasonic element while separating the ultrasonic element from the case diaphragm. A horn shape is defined in the element housing case in which a width of the resonant space in a direction orthogonal to the directional axis is reduced as the resonant space extends in an axial direction parallel to the directional axis.

First claim

What is claimed is:

1. An ultrasonic sensor comprising:
an ultrasonic element arranged to transmit or receive a propagating wave, which is an ultrasonic wave propagating along a directional axis; and
an element housing case that includes a case diaphragm, which is a vibration membrane or a vibrating plate having a thickness direction along the directional axis, the element housing case housing the ultrasonic element while separating the ultrasonic element from the case diaphragm, wherein
a resonant space for the propagating wave is defined between the case diaphragm and the ultrasonic element,
a horn shape is defined in the element housing case in which a width of the resonant space in a plane direction orthogonal to the directional axis is reduced as the resonant space extends in an axial direction parallel to the directional axis, and
the ultrasonic element, the resonant space, and the case diaphragm are configured such that a first resonance frequency, which is a resonance frequency in the ultrasonic element, a second resonance frequency, which is a resonance frequency in the resonant space, and a third resonance frequency, which is a resonance frequency in the case diaphragm, coincide with each other.

2. The ultrasonic sensor according to claim 1 , wherein
when a maximum value among a difference between the first resonance frequency and the second resonance frequency, a difference between the second resonance frequency and the third resonance frequency, and a difference between the first resonance frequency and the third resonance frequency is defined as Δfr, and a bandwidth of a widest resonance band among resonance bands of the ultrasonic element, the resonant space, and the case diaphragm is defined as BW, a relationship of Δfr≤BW is satisfied.

3. The ultrasonic sensor according to claim 1 , further comprising a damping member housed in the resonant space.

4. The ultrasonic sensor according to claim 1 , wherein
the element housing case has a vent provided to communicate an internal space with an external space, and
the vent is liquid-tightly sealed to allow a passage of an air while inhibiting a passage of a liquid.

5. The ultrasonic sensor according to claim 4 , wherein
the element housing case includes
a side plate portion formed in a cylindrical shape surrounding the directional axis,
an inner bottom plate portion that closes one end side of the side plate portion in the axial direction, and
an outer bottom plate portion that liquid-tightly closes the other end side of the side plate portion in the axial direction,

the case diaphragm is formed as a thin portion provided in the outer bottom plate portion, and
the vent is provided in the inner bottom plate portion.

6. The ultrasonic sensor according to claim 1 , further comprising a frequency changing unit provided to change a vibration frequency in the ultrasonic element, the resonant space, or the case diaphragm in response to an operating environment temperature of the ultrasonic sensor.

7. The ultrasonic sensor according to claim 1 , wherein a plurality of the case diaphragms, a plurality of the ultrasonic elements, or a plurality of the resonant spaces are arrayed in the plane direction.

8. The ultrasonic sensor according to claim 7 , further comprising a vibration isolation member interposed between the adjacent resonant spaces to inhibit a vibration transmission between the adjacent resonant spaces when the plurality of resonant spaces are arrayed in the plane direction.

9. An ultrasonic sensor comprising:
an ultrasonic element arranged to transmit or receive a propagating wave, which is an ultrasonic wave propagating along a directional axis; and
an element housing case that includes a case diaphragm, which is a vibration membrane or a vibrating plate having a thickness direction along the directional axis, the element housing case housing the ultrasonic element while separating the ultrasonic element from the case diaphragm, wherein
a resonant space for the propagating wave is defined between the case diaphragm and the ultrasonic element,
a horn shape is defined in the element housing case in which a width of the resonant space in a plane direction orthogonal to the directional axis is reduced as the resonant space extends in an axial direction parallel to the directional axis,
the element housing case includes a case thick portion which is a thick portion formed around an outer side of the case diaphragm in a radial direction orthogonal to the directional axis to surround the resonant space,
the case thick portion includes a horn inner surface which faces the resonant space to define the resonant space,
the resonant space has
a space bottom, which is an end of the resonant space adjacent to the ultrasonic element in the axial direction, and
a space top, which is an end of the resonant space adjacent to the case diaphragm in the axial direction,

the horn inner surface is formed in a cone inner surface shape which tapers the resonant space toward the case diaphragm, and
a radial dimension of the space bottom is larger than a radial dimension of the space top.

10. The ultrasonic sensor according to claim 9 , wherein
the ultrasonic element has an element diaphragm, which is a vibration membrane or a vibration plate formed on a semiconductor substrate and having a thickness direction along the directional axis, and
the element diaphragm has a radial dimension coinciding with the radial dimension of the space bottom.

11. The ultrasonic sensor according to claim 9 , wherein the ultrasonic element is fixedly supported on the element housing case to cause a gap between the ultrasonic element and the case thick portion in the axial direction to be ¼ or less of a wavelength of the propagating wave.

12. The ultrasonic sensor according to claim 9 , wherein
the case thick portion has a slit extending from the space top in the radial direction to communicate with the space top,
the case diaphragm has a central portion facing the space top in the axial direction, and a ring-shaped portion facing the slit in the axial direction, and
the slit has a radial dimension larger than the radial dimension of the space bottom.

13. The ultrasonic sensor according to claim 12 , wherein an axial dimension of the slit is set to ¼ or less of a wavelength of the propagating wave.

14. The ultrasonic sensor according to claim 12 , further comprising a spacer which is an elastic body filled in the slit.

15. The ultrasonic sensor according to claim 14 , wherein the spacer has an elastic modulus lower than that of the case diaphragm.

16. The ultrasonic sensor according to claim 9 , wherein the horn inner surface is formed in a curved shape.

17. An ultrasonic sensor comprising:
an ultrasonic element arranged to transmit or receive a propagating wave, which is an ultrasonic wave propagating along a directional axis; and
an element housing case that includes a case diaphragm, which is a vibration membrane or a vibrating plate having a thickness direction along the directional axis, the element housing case housing the ultrasonic element while separating the ultrasonic element from the case diaphragm, wherein
a resonant space for the propagating wave is defined between the case diaphragm and the ultrasonic element,
a horn shape is defined in the element housing case in which a width of the resonant space in a plane direction orthogonal to the directional axis is reduced as the resonant space extends in an axial direction parallel to the directional axis, and
an axial dimension of the resonant space is se

Assignees

• Denso Corp

Inventors

• Kamiya Tatsuya
• Ishii Itaru
• Tanemura Tomoki
• Aoki Takashi
• Katoh Tetsuya

Classifications

• G01S7/521 Primary

  Constructional features · CPC title

• B60R11/00 Primary

  Arrangements for holding or mounting articles, not otherwise provided for · CPC title

• G01S15/931

  of land vehicles · CPC title

• B60R2011/004

  outside the vehicle · CPC title

• G01S15/899

  Combination of imaging systems with ancillary equipment · CPC title