Pressure sensor

• US 5,557,971 A
• Filed: 12/14/1994
• Issued: 09/24/1996
• Est. Priority Date: 12/17/1993
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Nakamura, Hiroshi, Kodama, Seiki, Uemura, Fumito
• Primary Examiner(s): Chilcot, Richard
• Assistant Examiner(s): Oen, William L.
• Application Number:
  US08/355,683
• Time in Patent Office: 650 Days
• Field of Search: 73/702, 73/703, 73/704, 73/706, 73/756
• US Class Current: 73/702
• CPC Class Codes: G01L 19/0046 using isolation membranes G01L13/026 and G01L19/0645 take precedence
• CPC Class Codes: G01L 23/18 by resistance strain gauges

Abstract

A pressure sensor for detecting engine knocking includes a diaphragm 40, and a pressure transmitting medium 10 filled between a pressure sensing element 5 and the diaphragm. The diaphragm has a diameter d and a plate thickness t for enabling the diaphragm to have a resonant frequency substantially equal to the frequency of an abnormal pressure vibration; the diameter d and the plate thickness t satisfy the formula t=Kd², where K=3.3×10⁴ ˜5.3×10⁴.

Claims

1. A pressure sensor for sensing pressure vibrations in a combustion chamber of an internal combustion engine, comprising:

a) a case (1) having a detection cavity (3c) which has an open end;

b) a pressure sensing means (5) disposed in said detection cavity of said case;

c) a diaphragm (40) disposed to seal said open end of said detection cavity; and

d) a pressure transmitting medium (10) filled within said detection cavity,

e) wherein said diaphragm is substantially disc-shaped, and a diameter d (mm) and plate thickness t (μ

m) of said diaphragm satisfy a formula t=Kd², where K=3.3×

10^-4 ˜

5.3×

10^-4, such that a resonant frequency of said diaphragm lies within a range of abnormal pressure vibration frequencies in the combustion chamber and outside of a range of normal pressure vibration frequencies therein, and an output amplitude of the pressure sensing means is thereby substantially greater for an abnormal pressure vibration than for a normal pressure vibration.

2. A pressure sensor according to claim 1, wherein the diameter d lies between about 6-12 mm, and the plate thickness t lies between about 20-50 μ

m.

3. A pressure sensor according to claim 2, wherein the range of abnormal pressure vibration frequencies is 5000-9000 Hz.