GLOW PLUG WITH COMBUSTION PRESSURE SENSOR

• US 20150334777A1
• Filed: 05/13/2015
• Published: 11/19/2015
• Est. Priority Date: 05/16/2014
• Status: Active Grant

• Current Assignee: NGK Spark PLUG Company Limited
• Original Assignee: NGK Spark PLUG Company Limited
• Inventors: SASSA, Akimitsu, YAMAMOTO, Yoshihiro, HARADA, Hiroshi
• Granted Patent: US 10,244,583 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F23Q 2007/002 with sensing means
• CPC Class Codes: F23Q 7/001 Glowing plugs for internal-combustion engines
• CPC Class Codes: G01L 9/0051 using variations in ohmic resistance
• CPC Class Codes: H05B 3/0014 Devices wherein the heating current flows through particular resistances
• CPC Class Codes: H05B 3/0042 used in motor vehicles

Abstract

A glow plug including a heater (200) having a rear heat-generating element (260) formed of a resistance heat-generating element, and provided in an axial region thereof between a forward end (136) of a housing and a rear end (315) of a displacement member (300) located rearward of the forward end (136). The heat-generating element (260) is arranged separately from a forward heat-generating element (205) provided at a forward end portion of the heater.

Claims

1. A glow plug with a combustion pressure sensor comprising a rodlike ceramic heater having a forward heat-generating element provided at a forward end portion and adapted to generate heat through application of electricity, a tubular housing having the ceramic heater disposed therein with a forward end of the ceramic heater protruding forward from a forward end thereof, and a sensor capable of sensing combustion pressure by detecting pressure or displacement generated as a result of the ceramic heater being pressed rearward at the forward end by the combustion pressure,

an inner circumferential surface of a forward end portion of the housing and an outer circumferential surface of the ceramic heater defining an annular space communicating with an opening in a forward end of the housing, and the space accommodating a displacement member joined along a circumferential direction to the housing and to the ceramic heater and being deformable so as to allow displacement of the ceramic heater along an axis,

the glow plug being characterized in that the ceramic heater has a rear heat-generating element adapted to generate heat through application of electricity, for heating at least a portion of the outer circumferential surface of the ceramic heater in an axial region between a rear end portion of a protruding portion of the ceramic heater protruding forward from the forward end of the housing and a rear end of the displacement member located rearward of the rear end portion of the protruding portion of the ceramic heater.

3. The glow plug with the combustion pressure sensor as claimed in claim 1, wherein the axial region is an axial region between the forward end of the housing and the rear end of the displacement member located rearward of the forward end of the housing.

4. The glow plug with the combustion pressure sensor as claimed in claim 1, wherein the rear heat-generating element is provided in such a manner as to be electrically connected in parallel with the forward heat-generating element.

5. The glow plug with the combustion pressure sensor as claimed in claim 4, wherein the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner as to connect axially intermediate portions of a pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element.

6. The glow plug with the combustion pressure sensor as claimed in claim 4, wherein the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner as to connect forward ends or forward end portions of a pair of lead elements extending rearward and provided separately from the pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element.

7. The glow plug with the combustion pressure sensor as claimed in claim 4, wherein the rear heat-generating element is formed of a resistance heat-generating element higher in resistance than that used to form the forward heat-generating element.

8. The glow plug with the combustion pressure sensor as claimed in claim 1, wherein, in order for the rear heat-generating element to be electrically connected in series with the forward heat-generating element, the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner that the rear heat-generating element is located in an axially intermediate portion of each of a pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element and the rear heat-generating element connects portions of the corresponding lead element, which portions are located forward and rearward of the axially intermediate portion.

9. The glow plug with the combustion pressure sensor as claimed in claim 8, wherein the rear heat-generating element is formed of a resistance heat-generating element lower in resistance than that used to form the forward heat-generating element.

10. The glow plug with the combustion pressure sensor as claimed in claim 1, wherein the annular space communicating with the opening in the forward end of the housing comprises a space which is relatively narrow in a radial direction of the housing and is located toward the forward end and a space which is relatively wide in the radial direction and is located rearward of the narrow space, and, in the wide space, the displacement member is joined to the housing.

2. A glow plug with a combustion pressure sensor comprising a rodlike ceramic heater having a forward heat-generating element provided at a forward end portion and adapted to generate heat through application of electricity, a tubular housing having the ceramic heater disposed therein with a forward end of the ceramic heater protruding forward from a forward end thereof, and a sensor capable of sensing combustion pressure by detecting pressure or displacement generated as a result of the ceramic heater being pressed rearward at the forward end by the combustion pressure,

an inner circumferential surface of a forward end portion of the housing and an outer circumferential surface of the ceramic heater defining an annular space communicating with an opening in a forward end of the housing, and the space accommodating a displacement member joined along a circumferential direction to the housing and to the ceramic heater and being deformable so as to allow displacement of the ceramic heater along an axis,

the glow plug being characterized in that the ceramic heater has a rear heat-generating element formed of a resistance heat-generating element, adapted to generate heat through application of electricity, and provided in an axial region between a rear end portion of a protruding portion of the ceramic heater protruding forward from the forward end of the housing and a rear end of the displacement member located rearward of the rear end portion of the protruding portion of the ceramic heater.

11. The glow plug with the combustion pressure sensor as claimed in claim 2, wherein the axial region is an axial region between the forward end of the housing and the rear end of the displacement member located rearward of the forward end of the housing.

12. The glow plug with the combustion pressure sensor as claimed in claim 2, wherein the rear heat-generating element is provided in such a manner as to be electrically connected in parallel with the forward heat-generating element.

13. The glow plug with the combustion pressure sensor as claimed in claim 12, wherein the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner as to connect axially intermediate portions of a pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element.

14. The glow plug with the combustion pressure sensor according to claim 12, wherein the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner as to connect forward ends or forward end portions of a pair of lead elements extending rearward and provided separately from the pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element.

15. The glow plug with the combustion pressure sensor as claimed in claim 12, wherein the rear heat-generating element is formed of a resistance heat-generating element higher in resistance than that used to form the forward heat-generating element.

16. The glow plug with the combustion pressure sensor as claimed in claim 2, wherein, in order for the rear heat-generating element to be electrically connected in series with the forward heat-generating element, the rear heat-generating element is provided in an electrically insulative ceramic base member of the rodlike ceramic heater in such a manner that the rear heat-generating element is located in an axially intermediate portion of each of a pair of lead elements provided for application of electricity and extending rearward from the forward heat-generating element and the rear heat-generating element connects portions of the corresponding lead element, which portions are located forward and rearward of the axially intermediate portion.

17. The glow plug with the combustion pressure sensor according to claim 16, wherein the rear heat-generating element is formed of a resistance heat-generating element lower in resistance than that used to form the forward heat-generating element.

18. The glow plug with the combustion pressure sensor as claimed in claim 2, wherein the annular space communicating with the opening in the forward end of the housing comprises a space which is relatively narrow in a radial direction of the housing and is located toward the forward end and a space which is relatively wide in the radial direction and is located rearward of the narrow space, and, in the wide space, the displacement member is joined to the housing.