Patent Application
20070240485
Now, gas sensors of various embodiments according to the present invention are described below in detail with reference to the accompanying drawings. However, the present invention is construed not to be limited to such embodiments described below and technical concepts of the present invention may be implemented in combination with other known technologies or the other technology having functions equivalent to such known technologies.
In the following description, like reference characters designate like or corresponding parts throughout the several views. Also, in the following description, it is construed that a portion of a gas sensor adapted to be inserted to an exhaust pipe of an internal combustion engine of a motor vehicle is referred to as a “leading end” or a “distal end” and an opposite side of the gas sensor exposed to an atmosphere is referred to as a “base end” or a “base end portion”.
Also, it will be appreciated that the gas sensors of various embodiment according to the present invention may have a wide variety of applications to an oxygen sensor, an A/F sensor, a NOx sensor, etc.
A gas sensor of a first embodiment according to the present invention is described below in detail with reference to
As shown in
As shown in
Further, the housing 4 has a threaded portion 43, formed on an outer periphery of the lower cylindrical body 4c, with which the gas sensor 1 is mounted on the wall of the exhaust pipe. The housing 4 is internally formed with a first large diameter inner wall 4d and a second small diameter inner wall 4e, with an holder rest shoulder 4f being formed between the first and second inner walls 4d, 4e.
The insulating element holder 3 includes a large diameter cylindrical body 3a and a small diameter cylindrical body 3b, with an stepped engaging shoulder 3c being formed between the first and second cylindrical bodies 3a, 3b. The insulating element holder 3 also has a central bore 3d, through which the gas sensing element 2 extends in an axial direction of the gas sensor 1, and a cylindrical cavity 3e formed in the large diameter cylindrical body 3a and filled with glass sealant 6. Glass sealant 6 provides a sealing effect to prevent measuring gases from leaking through a clearance between the gas sensing element 2 and the small diameter cylindrical body 3b of the insulating element holder 3 to an upper area of the insulating element holder 3.
The insulating element holder 3 is accommodated in the housing 4 such that the large diameter cylindrical body 3a is inserted to the large diameter inner wall 4d of the housing 4 and the small diameter cylindrical body 3b is inserted to the small diameter inner wall 4e of the housing 4 with a packing element 5 being interposed between the stepped engaging shoulder 3c of the insulating element holder 3 and the holder rest shoulder 4f of the housing 4 to provide a sealing effect.
The packing element 5 separates a measuring gas side ambience 110 and an atmospheric side ambience 120 from each other in the gas sensor 1 in a hermetically sealing effect.
The holder rest shoulder 4f of the housing 4 is formed in the housing 4 at an opening angle “θ” representing an angle defined with a pair of profile lines appearing on a plane including a center axis M of the gas sensor 1 in a cross section thereof and set to be less than 100°.
As shown in
The gas sensor 1 of the present embodiment is further described in detail hereinafter.
The gas sensor 1 of the present embodiment has application to a motor vehicle and is mounted on an exhaust pipe of an internal combustion engine of the motor vehicle with a view to executing combustion control of the internal combustion engine. In such application, the gas sensor 1 of the present embodiment plays a role as, for instance, an O2 sensor, an A/F sensor, NOx sensor, etc.
The gas sensor 1 of the present embodiment comprises, in addition to the gas sensing element 2, the insulating element holder 3 and the housing 4, an atmospheric side insulator 8, a measuring gas side cover 11 fixedly mounted on an end face of the lower cylindrical body 4c of the housing 4, and an atmospheric side cover 12 fixedly mounted on the upper cylindrical body 4b of the housing 4 by welding. The atmospheric side ambience 120 is defined in the atmospheric side cover 12 and the measuring gas side ambience 110 is defined in the measuring gas side cover 11.
The atmospheric side insulator 8 is embedded in a protective casing 9 having outwardly extending retainer segments 9a held in abutting engagement with an inner periphery of the atmospheric side cover 12 for placement in fixed place. The atmospheric side insulator 8 has an axially extending cavity 8a that accommodates therein spring terminals 10, 10 held in electrical contact with electrode terminals (not shown) of the gas sensing element 2. The spring terminals 10, 10 are electrically connected to lead wire portions 13, 13.
The atmospheric side cover 12 has an upwardly extending base end section 12a having a plurality of ventilation openings 12b formed at circumferentially spaced positions. The base end section 12a of the atmospheric side cover 12 carries thereon an outer cover 14 formed with a plurality of ventilation openings 14a at circumferentially spaced positions in radial alignment with the ventilation openings 12b formed on the base end section 12a of the atmospheric side cover 12 to introduce atmospheric air into the atmospheric side ambience 120.
A ventilation filer 16 is interposed between the base end section 12a of the atmospheric side cover 12 and the outer cover 14 in a position to provide a waterproof function between the ventilation openings 14a of the outer cover 14 and the ventilation openings 12b of the base end section 12a of the atmospheric side cover 12 while admitting atmospheric air to an inside of the atmospheric side cover 12.
As shown in
The measuring gas side cover 11 takes a double-layer structure that includes an inner protecting cover 11a, formed with a plurality of openings 11 aa, and an outer protecting cover 11b having a plurality of openings 11ba. Thus, the openings 11aa, 11ba play roles as gas flow ports through which measuring gases are introduced to an inside of the measuring gas side cover 11 in contact with a detecting section 2a of the gas sensing element 2.
When assembling the insulating element holder 3 to the housing 4, the gas sensing element 2 is inserted through and fixedly supported with the insulating element holder 3 and the lower small diameter cylindrical body 3b of the insulating element holder 3 is then inserted through the packing element 5. Subsequently, the insulating element holder 3 and the packing element 5 are inserted through the housing 4 such that the upper cylindrical body 3a passes through the inner wall 4d of the housing 4 and the lower cylindrical body 3b passes through the inner wall 4e of the housing 4 with the packing element 5 being sandwiched between the stepped engaging shoulder 3c of the insulating element holder 3 and the holder rest shoulder 4f of the housing 4.
With such a condition, the packing element 5 has a base end face 5a held in abutting engagement with the stepped engaging shoulder 3c of the insulating element holder 3 and a leading end face 5b held in abutting engagement with the holder rest shoulder 4f of the housing 4 as shown in
Then, the ring-like spring 7 is held in fixed place on the upper end face of the insulating element holder 3 with the annular shoulder 44 of the housing 5 to allow the insulating element holder 3 to be pressed against the housing 4 with the given urging force. When this takes place, the insulating element holder 3 and the housing 4 are held in tight contact with each other by means of the packing element 5 sandwiched between the stepped engaging shoulder 3c of the insulating element holder 3 and the holder rest shoulder 4f of the housing 4. In such a way, the packing element 5 allows the measuring gas side ambience 110 and the atmospheric side ambience 120 to be hermetically separated from each other.
With the gas sensor 1 of the present embodiment, the packing element 5 is made of suitable metallic material such as nickel, nickel alloy and stainless steel (SUS430) with hardness of Hv100 to 200. In addition, the packing element 5 has a size with, for instance, an inner diameter φ1 of 13 mm and an outer diameter φ2 of 15.5 mm with a thickness of 0.4 mm.
Further, the holder rest shoulder 4f of the housing 4 has a cross section formed in a straight line on a plane including the center axis M of the gas sensor 1 as shown in
As shown in
Thus, with the gas sensor 1 of the present embodiment, the packing element 5 and glass sealant 6 hermetically seal off the atmospheric side ambience 120 and the measuring gas side ambience 110 from each other. This enables the gas sensing element 2 to detect a concentration of specified gas in measuring gases with high precision.
With the gas sensor 1 of the present embodiment set forth above, the insulating element holder 3 is press downward, that is, toward a distal end of the gas sensor 1 with the action of the ring-shaped spring 7 fixedly held with the annular shoulder 44 of the housing 4. When this takes place, the stepped engaging shoulder 3c of the insulating element holder 3 is pressed against the holder rest shoulder 4f of the housing 4 via the packing element 5.
Under such a state, as shown in
When mounting the gas sensor 1 of the present embodiment on an exhaust pipe of an internal combustion of a motor vehicle, the measuring gas side cover 11 of the gas sensor 1 is inserted to an inside of the exhaust pipe of the engine, after which the housing 4 is turned with an impact wrench engaging the tool-fitting portion 4aa of the housing 4. This causes the threaded portion 43, formed on the outer periphery of the lower cylindrical body 4c of the housing 4, to be screwed into a threaded bore formed in the wall of the exhaust pipe, and the gas sensor 1 is fixedly mounted on and tightened onto the wall of the exhaust pipe.
The gas sensor 1 of the present embodiment has various advantageous effects as listed below.
As shown in
That is, the ring-shaped spring 7, fixed in place with the annular shoulder 44 of the housing 4, urges the packing element 5 against the holder rest shoulder 4f of the housing 4 in an axial direction of the gas sensor 1. This allows the packing element 5 to be tightly held in contact with the stepped engaging shoulder 3c of the insulating element holder 3 and the holder rest shoulder 4f of the housing 4 via the packing element 5.
Thus, the atmospheric side ambience 120 and the measuring gas side ambience 110 can be hermetically separated from each other. Under such a condition, as shown in
The inventor has found out that increasing the component force “f” and the reactive force “F” to respective adequate levels enables the prevention of a drop in hermetically sealing effect resulting from impact shocks occurred during mounting step of the gas sensor 1 with the use of a mounting tool.
Thus, by forming the holder rest shoulder 4f of the housing 4 at the opening angle θ less than 100°, it becomes possible to ensure the component force “f” and the reactive force “F” with respective adequate values as shown in
As shown in
Further, since the packing element 5 has hardness in a range from Hv100 to 200, the packing element 5 can be uniformly deformed in an adequately fitted pattern between the holder rest shoulder 4f of the housing 4 and the stepped engaging shoulder 3c of the insulating element holder 3.
Furthermore, since the packing element 5 is made of stainless steel, the packing element 5 can suppress the occurrence of oxidation, corrosion and deteriorated durability even under real car ambiences. This results in a capability of obtaining a gas sensor 1 having an increased hermetically sealing effect between the atmospheric side ambience 120 and the measuring gas side ambience 110.
As set forth above, the present invention makes it possible to provide a gas sensor having an increased hermetically sealing effect between the atmospheric side ambience 120 and the measuring gas side ambience 110.
A gas sensor 1A of a second embodiment according to the present invention is described below with reference to
With the gas sensor 1A of the present embodiment, a housing 4A has a large diameter holder rest shoulder 200 contiguous with an inner peripheral wall 4d of the housing 4A and a small diameter holder rest shoulder 202 having one end contiguous with the first holder rest shoulder 200 and the other end contiguous with an inner peripheral wall 4e of the housing 4A. The first and second holder rest shoulders 200, 202 are formed at an obtuse angle with an intermediate portion formed in a crook portion 203. The insulating element holder 3 has a large-diameter engaging shoulder 204 and a small-diameter engaging shoulder 206, both of which are formed in a bend pattern substantially in parallel to the first and second holder rest shoulders 200, 202, respectively.
The large diameter holder rest shoulder 200 of the housing 4A is formed at an opening angle θ less than 120° representing an angle defined with a pair of profile lines extending on a plane including the center axis M of the gas sensor 1A in a cross section thereof. Meanwhile, the small diameter holder rest shoulder 202 of the housing 4A is formed at an opening angle θ of, for instance, approximately 150°.
In addition, the first and second holder rest shoulders 200, 202 are formed on straight lines, respectively. The gas sensing element 1A of the present embodiment has the same other structure as that of the gas sensor 1 shown in
The gas sensor 1A of the present embodiment has various advantageous effects as described below.
With the insulating element holder 3A press fitted against the housing 4A, the packing element 5 is compressed with an urging force of the spring 7 (see
Further, the crook portion 203 is provided on a boundary between the large diameter holder rest shoulder 200 and the small diameter holder rest shoulder 202, both of which are formed at different opening angles. The present inventor has also revealed that such a crook portion 203 is effective to retain the packing element 5 in a fixed place with increased adhesion between the packing element 5 and the first and second holder rest shoulders 200, 202.
Therefore, in a case where the opening angle θ is set to be less than 120°, the gas sensor 1A can have the component force and the reactive force with respective increased levels and the crook portion 203 that can ensure adequate adhesion between the packing element 5 and the first and second annular shoulder holder rest shoulders 200, 202. This enables the prevention of a drop in hermetically sealing effect resulting from impact shocks caused during mounting step with the use of a mounting tool, enabling the provision of a gas sensor 1A with increased hermetically sealing effect between the atmospheric side ambience 120 and the measuring gas side ambience 110.
The gas sensor 1A of the present embodiment has the other advantageous effects as those of the gas sensor 1 of the first embodiment shown in
Also, it will be appreciated that the present invention is not limited to such a particular structure mentioned above and various other modifications may be implemented. For instance, the gas sensor 1A may be altered such that the small diameter holder rest shoulder 202 is formed at an opening angle with a value less than that of the large diameter holder rest shoulder 200 to allow the small diameter holder rest shoulder 202 to be formed at the opening angle less than 120°.
Further, the housing 4A may have more than three holder rest shoulders defined at different opening angles. In another alternative, the housing 4A may have a holder rest shoulder formed in a curved profile.
A gas sensor 1B of a third embodiment according to the present invention is described below with reference to
With the gas sensor 1B of the present embodiment, a housing 4B has a holder rest shoulder 212 contiguous with the inner peripheral wall 4d of the housing 4B and the inner peripheral wall 4e of the housing 4B. The insulating element holder 3B has a curved engaging shoulder 210 formed in face-to-face relationship with the curved holder rest shoulder 212 of the housing 4B.
The curved holder rest shoulder 212 of the housing 4B is formed in the housing 4B so as to allow a tangential line of the curved holder rest shoulder 212 to be aligned at an opening angle θ less than 100°.
A gas sensor 1C of a fourth embodiment according to the present invention is described below with reference to
With the gas sensor 1C of the present embodiment, a housing 4C has an holder rest shoulder 310 formed at a given opening angle. The insulating element holder 3C has a large-diameter engaging shoulder 300 and a small-diameter engaging shoulder 302, with the large-diameter engaging shoulder 300 intersecting an inner peripheral wall 4d of the housing 4C at an acute angle while the small-diameter engaging shoulder 302 extending substantially parallel to the holder rest shoulder 310 of the housing 4C.
With the gas sensor 1C mentioned above, an annular space 312 is provided between the large-diameter stepped engaging shoulder 300 of the insulating element holder 3C and the inner peripheral wall 4d of the housing 4C. With the insulating element holder 3C assembled to the housing 4C, the packing element 5 has a base end portion 5c that is accommodated in the annular space 312. The base end portion 5c of the packing element 5 protrudes into the annular space 312 by a length greater than 0.3 mm from an upper edge of the holder rest shoulder 310 of the housing 4C.
The gas sensor 1C of the present embodiment has the same other structure as that of the gas sensor 1 of the first embodiment shown in
With the gas sensor 1C of the present embodiment, the base end portion 5c of the packing element 5 protrudes into the annular space 312 by a length greater than 0.3 mm from the upper edge of the stepped engaging shoulder 302, providing increased adhesion between the inner peripheral wall 4d of the housing 4C and the base end portion 5c of the packing element 5.
Various test pieces on gas sensors were prepared with structures having single holder rest shoulders formed at different opening angles θ. Impact shocks were applied to the test pieces on the housings thereof and the degrees of hermetically sealing performance of packing elements were measured, with test results being plotted in
Also, the component parts of the test pieces bear like reference numerals pursuant to those used in the gas sensor 1 shown in
For measuring the hermetically sealing performances, gas sensors were prepared as the test pieces with structures each formed with a housing 4 having a single holder rest shoulder formed at different opening angles θ. That is, four kinds of test pieces were prepared with the opening angles θ being set to 80°, 100°, 120° and 150°, respectively. Moreover, four samples were prepared for each test piece.
Also, the packing elements 5 had hardness of Hv120.
Impact shocks were applied to the test pieces and, thereafter, the hermetically sealing effects of the test pieces between atmosphere ambiences 120 and measuring gas side ambiences 110 were measured. The hermetically sealing effects of the test pieces were evaluated in two phases including one phase before tool fitting portions 4aa of the housings 4 of the test pieces were turned with a mounting tool such as an impact wrench and the other phase after the tool fitting portions 4aa of the housings 4 were turned with the mounting tool.
In evaluating the hermetically sealing performances of the test pieces, tests were conducted upon placing the test pieces on a hermetic sealing evaluation tester provided with a chamber maintained under a measuring gas atmosphere at the nearly same pressure (of 0.4 MPa) as that of a real car environment after which measurements were conducted to check the amount of gas leaked from the measuring gas side ambience 110 to the atmosphere ambience 120 in each test piece per unit time.
During tests, initially, a gas leakage quantity of each test piece was measured using the hermetic sealing evaluation tester under a condition before each sample is applied with shock impacts. Subsequently, the tool-fitting portion 4aa of each sample was turned with the impact wrench to cause each sample to be tightened and fixed to a dummy jig. Then, each sample was taken out of the jig and the gas leakage quantity was measured again with the hermetic sealing evaluation tester after the impact shocks were applied to each sample.
Prior to the application of impact shocks, each sample substantially had almost no gas leakage with the gas leakage quantity falling in a value less than 0.01 cc/minute.
It is turned out from
That is, it can be said that with the gas sensors including the housings each having the holder rest shoulder formed at the opening angle θ less than 100°, each gas sensor can ensure tightly contact states between the holder rest shoulder 4f and the packing element 5 and between the stepped engaging shoulder 3c and the packing element 5 for thereby preventing gas from leaking from the measuring gas side ambience 110 to the atmospheric side ambience 120.
Various test pieces on gas sensors for Example 2 were prepared with structures having composite holder rest shoulders formed at different opening angles θ. Housings of the test pieces were applied with impact shocks and hermetically sealing performances of packing elements were measured with test results being plotted in
Also, the component parts of the test pieces bear like reference numerals pursuant to those used in the gas sensor 1 shown in
For measuring hermetically sealing performances, gas sensors were prepared as the test pieces with structures including housings 4 having composite holder rest shoulders each including a large-diameter holder rest shoulder 200 and a small-diameter holder rest shoulder 202 (see
Also, the packing elements 5 had hardness of Hv120.
As will be apparent from
That is, it will be understood that even with the gas sensors having the housing formed with the plural holder rest shoulders 200, 202, the present invention can provide favorable advantageous effects provided that the large-diameter holder rest shoulders 200 are formed at the opening angles θ less than 120°.
Various test pieces on gas sensors for Example 3 were prepared with structures having composite engaging shoulders 300, 302 associated with packing elements 5 with base end portions 312 protruding in various protruding lengths T. Housings of the test pieces were applied with impact shocks and hermetically sealing performances of packing elements were measured with test results being plotted in
Also, the component parts of the test pieces bear like reference numerals pursuant to those used in the gas sensor 1 shown in
In this Example 3, three kinds of test pieces were prepared with packing elements 5 having base end portions Sc protruding into the annular spaces 312 in protruding lengths T of 0.2 mm, 0.3 mm and 0.5 mm. Moreover, the test pieces had housings 4C formed with holder rest shoulders 310 fixed at an opening angle θ of 100°. In addition, four samples were prepared for each test piece.
Also, the packing elements 5 had hardness of Hv120.
The samples had the same other structures as those of the gas sensor 1 shown in
As will be apparent from
Various tests were conducted on the gas sensors (see
In Example 4, the gas sensors were prepared as test pieces with structures employing the packing elements 5 with hardness varied in a range from Hv50 to 250.
Hardness of the packing elements 5 were measured with a test force of 4.903N using a MicroVickers hardness tester with hardness Hv (0.5) standardized under JIS Z2244.
Further, with the gas sensors, the housings 4A had the large-diameter holder rest shoulders 200 formed at a fixed opening angle θ of 120°.
Each of the samples had the same other structure as that of the gas sensor 1 shown in
As will be apparent from
While the specific embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limited to the scope of the present invention, which is to be given the full breadth of the following claims and all equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-114340 | Apr 2006 | JP | national |
