KR20070015952A - Glow plug head and corresponding piezo-electric pressure sensor - Google Patents

Abstract

The present invention provides a glow plug comprising a pressure sensor mounted in the tubular member 8 and maintained therein with the aid of the support and held in the tubular member 8 by plastic deformation 52 of the tubular member wall portion. It is about.

Description

Glow PLUG HEAD AND CORRESPONDING PIEZO-ELECTRIC PRESSURE SENSOR}

The present invention relates to a glow plug head and a piezoelectric pressure sensor positioned within the glow plug head.

It is known to integrate pressure sensors in glow plugs in internal combustion engines, in particular diesel engines. Such a sensor makes it possible to measure the internal pressure of the engine. Knowing these pressures makes it possible to better control the progress of combustion in the engine. Thus, engine efficiency is better and fuel consumption as well as emission of pollutants can be limited.

The glow plug generally includes a tubular body having threads on its outer surface, which allows the tubular body to be secured within a corresponding bore formed in the cylinder head. One part of this body is located inside the combustion chamber and the other part is located outside the combustion chamber. The part inside the combustion chamber has a finger in which the heating electrode is located. The heating electrode is supplied by the core passing through the tubular body of the glow plug. Parts outside the engine are also referred to as glow plugs. The head of the core is connected to an electrical energy source. It is also known to place the pressure sensor in such a head.

To mount such a pressure sensor, Applicants have not yet disclosed, but know to place the sensor in a housing provided in the body of the glow plug. A female thread is formed at the opposite end of the finger integrating the heating electrode, and the pressure sensor is held in the housing by assembling a nut having a male thread. One side of the piezoelectric type pressure sensor is placed on the support member via an insulating member, and the spacer connects the finger of the glow plug to the support member. Thus, the pressure sensor is held by the nut and the spacer transmits a force through the support member (and the insulation member), which force is applied to the support member by the pressure in the corresponding combustion chamber.

This assembly method has the problem that in particular the adjacent glow plugs, more particularly the head of the glow plug body, must be fully machined.

During assembly of the glow plug and pressure sensor, a number of members are placed in place and the nut with male thread is placed towards the end of the assembly. At times it should be noted that it is difficult to obtain the correct compressive stress of the piezoelectric pressure sensor. This compressive stress depends in particular on the processing tolerances and the roughness of the material.

Accordingly, the present invention aims at providing a sensor assembly which can solve these drawbacks, in particular a low manufacturing cost, and which can preferably control the compressive stress exerted on the pressure sensor.

To this end, the present invention provides a glow plug comprising a pressure sensor mounted in the tubular member and held by the support member in the tubular member.

According to the invention, the support member is held in the tubular member by plastic deformation of the wall portion of the tubular member.

This makes it possible to limit the machining operation for placing the pressure sensor in place as compared to the method in which the supporting member is screwed or the other member is held by the screwed member. This is because there is no need for screws in the pressure sensor here. In addition, by deforming the wall portion of the tubular member, it is possible to better control the stress applied to the sensor. Finally, no rotation is necessary during the plastic deformation carried out to hold the support member, so that the parts in the glow plug are not rotationally driven.

In one embodiment of the invention, the support member is held by crimping.

In order to maintain the support member well, the support member advantageously has a conical surface over at least a portion of the outer circumference and the large diameter base of the cone is oriented towards the pressure sensor.

In an advantageous embodiment, the pressure sensor is a piezoelectric sensor comprising a piezoelectric member mounted between two contact members, the piezoelectric member having an annular shape with a flat portion on the outer circumference. This method can optimize the surface of the pressure sensor in a state where the wall of the housing containing the pressure sensor should not be deformed. In this embodiment, the piezoelectric member and the contact member are disposed substantially transversely in the tubular member, for example; The contact members each have a connecting tab on an outer periphery extending substantially longitudinally with respect to the tubular member, which connecting tab is disposed in front of the flat portion of the piezoelectric member.

In the glow plug according to the invention, the tubular member comprises an inner wall which is substantially circular cylindrical.

The tubular member containing the pressure sensor may be a tubular body, generally referred to as a glow plug body, which allows the glow plug to be secured inside the cylinder head of the internal combustion engine. However, other parts, including the housing, may receive the pressure sensor.

When the pressure sensor is mounted in the glow plug body, the glow plug is fixed in the cylinder head by screwing, and includes a gripping area having a hexagonal cross section to facilitate screwing and unscrewing, the support member is in place. Plastic deformations that can be maintained are performed, for example, adjacent to the gripping region.

The invention also relates to an internal combustion engine, in particular a diesel internal combustion engine, characterized in that it comprises at least one glow plug as described above.

Finally, the present invention also provides a method of mounting a pressure sensor in the head of the glow plug, in which the sensor is installed in the mating housing and held by the support member.

According to the invention, the support member is held in place by plastically deforming the wall portion of the housing containing the sensor and the support member.

The details and advantages of the invention will become more apparent from the following detailed description with reference to the accompanying drawings.

1 is a longitudinal sectional view of an example of a glow plug according to the present invention;

2 is a side view of a glow plug according to the present invention;

3 is an enlarged view of an upper portion of the glow plug of FIG. 2, and

4 is an enlarged perspective view of a piezoelectric sensor having a corresponding supporting member of the glow plug of FIGS. 2 and 3;

1 shows a longitudinal cross-sectional view of a glow plug model of the prior art (not disclosed upon initial submission of this patent application). Such a glow plug may include a pressure sensor to measure the pressure in the engine cylinder. This glow plug 2 is mounted on a diesel engine 4, more particularly on the cylinder head 6 of the engine in a conventional manner. The glow plug comprises a body 8, a finger 10, a core 12 and a pressure sensor 14.

The main body 8 is fixed to the engine 4 by screwing. For this purpose the cylinder head 6 comprises a screw bore through the cylinder head and an opening into the combustion chamber of the engine. For the body 8, the body 8 has threads 16 on the other surface corresponding to the bores formed in the cylinder head 6. When the glow plug is in the mounting position of the engine 4, part of the body 8 extends inside the engine, ie toward the combustion chamber, while the other part of the body 8 extends out of the engine. . The main body 8 is a tubular main body and is formed of steel, for example.

In this embodiment, the finger 10 is mounted in the tubular body 8 and is fitted in the tubular body 8 and protrudes into the combustion chamber. This finger 10 integrates a heating electrode (not shown). The core 12 supplies electrical energy to this electrode and penetrates the body 8 from the finger 10 to the opposite end of the body 8 from which the finger 10 protrudes. This core 12 is then connected to the supply lead by means not shown.

The pressure sensor 14 is provided to measure the pressure in the corresponding combustion chamber. In the embodiment of FIG. 1, this pressure sensor 14 comprises a piezoelectric member 18 disposed between two connecting elements 20 formed of an electrically conductive material. The sensor is then insulated from the rest of the glow plug 2 by the insulating member 22.

In this embodiment, the pressure sensor 14 is supported on the body 8 via a bearing part 24. The pressure sensor 14 is connected to the body 8 by the upper surface and supports the finger 10 such that the pressure applied to the finger urges the finger against the body 8. For this purpose, the pressure sensor 14 acts on a spacer 38 placed on the finger 10 and disposed in the body 8.

Compression of the pressure sensor 14 against the finger 10 (via the spacer 38 and the support 24), as well as the connection to the body 8, is provided by a nut with an external screw threading 36. do. This nut, of course, does not contact the core 12 but cooperates with an internal thread formed on the inner surface of the side wall 16 of the housing 48 formed in the body 8 to receive the sensor 14.

The present invention is provided to support the pressure sensor 14 differently. 2 is an external view of a glow plug according to the invention. This glow plug has a substantially identical structure in the longitudinal section, for example as shown in FIG. 1. Of course, any other glow plug structure may also be possible.

In the following detailed description, the members of the glow plug according to the invention, similar to the glow plug shown in FIG. 1, will be indicated by the same reference numerals. In addition, the glow plug has a particular orientation, in particular the head of the glow plug comprising the pressure sensor is considered to be located upwards, while the fingers of the glow plug located inside the engine are considered to be bottomed.

The glow plug according to the invention also has a housing 48 similar to the housing 48 of FIG. 1. The second support member 50 is placed in position on the pressure sensor 14. The support member 50 closes the upper open surface of the housing 48. In contrast, in the embodiment of FIG. 1, the closure of this housing 48 is provided by a nut having a male thread, the male thread also acting as a supporting member for the piezoelectric sensor, wherein the second supporting member 50 is crimped ( maintained by crimping). During the crimping operation, the side wall portion 46 of the housing 48 is plastically deformed to trap the second support member 50. In Figure 2 it can be seen the indentation 52 due to crimping.

As can be seen in FIG. 2, the head of the main body 8 of the glow plug has a gripping area 54 of hexagonal cross section. The gripping area 54 is used for screwing and unthreading the glow plug into the cylinder head 6.

In FIG. 2 the head of the glow plug comprises a hexagonal gripping region 54 at the bottom. Above the gripping area the head of the glow plug has an outer surface of a circular cylindrical outer circumference. Thus, crimping is performed in the circular cylinder region located above the gripping region 54.

In the embodiment of the glow plug shown here, the piezoelectric pressure sensor is generally in the form of an annular shape (where a center hole is provided for the passage of the core 12) with a flat portion 56 on the outer circumference. The piezoelectric member 18, the contact member 20, and the second support member 50 reproduce this annular shape with the flat portion 56.

The contact member 20 and the piezoelectric member 18 are disposed laterally with respect to the housing 48 which houses them. Each contact member 20 has a connecting tab 58 extending perpendicular to the plane of the corresponding contact member 20. These connection tabs 58 thus extend longitudinally relative to the housing 48 and extend substantially parallel to the core 12. As shown in FIG. 3, providing a flat portion 56 on the pressure sensor 14 cuts out the side wall portion 46 of the housing to allow the connecting tab 58 to pass therethrough. Or pressure sensor 14 in housing 48 without the need to provide anything else.

As can be seen in FIG. 4, the second support member 50 has a somewhat conical shape. The diameter of the lower surface of this second support member 50, that is, the surface oriented toward the pressure sensor 14, is somewhat larger than the diameter of the upper surface of the support member 50. During the crimping operation, the side wall portion 46 at least partially adopts this truncated cone shape, which ensures that the second support member 50 is correctly held in the housing 48.

Compared to the maintenance of the pressure sensor by the screw plug (in the case of FIG. 1), the assembly of the sensor in the housing and covering the sensor by the support member prior to deforming the side wall of the housing to trap the support member and thus the pressure sensor is preferred. Very preferred.

First, the machining cost of the corresponding glow plugs is substantially reduced. More specifically, there is no need to manufacture female threads in the housing that houses the pressure sensor. In addition, the assembly can be facilitated to lower the assembly cost.

In the glow plug according to the invention it is also easier to control the compressive stress applied to the pressure sensor when the housing in which the sensor is located is closed compared to the glow plug as in FIG. 1. When the housing is closed using a nut, the force applied to the nut is adjusted to obtain a stress on the pressure sensor. Depending on the manufacturing tolerances and roughness of the parts, it is difficult to ensure that a specific load on the sensor is maintained. The method provided by the present invention makes it possible to better control this load.

Finally, while assembling the nut with male thread, the plurality of components in the glow plug are rotationally driven. Of course, as mentioned above, this drawback does not exist in the glow plugs according to the invention.

The invention is not limited to the embodiments described above by way of non-limiting illustration. In addition, the present invention relates to all modifications that can be understood by those skilled in the art.

Thus, the present invention is particularly applicable to a number of glow plug structures incorporating pressure sensors.

The method provided herein can be applied when the pressure sensor is mounted to the body of the glow plug, but can also be applied when the sensor is mounted to other parts within the housing.

Claims (10)

In the glow plug 2 comprising a pressure sensor 14 mounted in the tubular member 8 and held in the tubular member 8 by the support member 50, The support member 50 is held in the tubular member 8 by plastic deformation of the wall portion 46 of the tubular member. Glow plug. The method of claim 1, The support member 50 is characterized in that it is held in place by crimping Glow plug. The method according to claim 1 or 2, The support member 50 has a conical surface over at least a portion of the outer circumference, and the base having the large diameter of the cone is oriented towards the pressure sensor 14. Glow plug. The method according to any one of claims 1 to 3, The pressure sensor 14 is a piezoelectric sensor including a piezoelectric member 18 mounted between two contact members 20, and the piezoelectric member 18 has an annular shape having a flat portion 56 on its outer circumference. Characterized by having Glow plug. The method of claim 4, wherein The piezoelectric member 18 and the contact member 20 are disposed in the tubular member 8 substantially in the transverse direction, and the contact member 20 respectively extends substantially longitudinally relative to the tubular member 8. And a connection tab 58 on an outer circumference thereof, wherein the connection tab 58 is disposed in front of the flat portion 56 of the piezoelectric member 18. Glow plug. The method according to any one of claims 1 to 5, Characterized in that the tubular member 8 comprises an inner wall which is a substantially circular circular barrel. Glow plug. The method according to any one of claims 1 to 6, The tubular member 8 which receives the pressure sensor 14 is a tubular body 8 which allows the glow plug 2 to be fixed in the cylinder head 6 of the internal combustion engine. Characterized by Glow plug. The method of claim 7, wherein The tubular body 8 is secured in the cylinder head 6 by screwing and includes a hexagonal cross-section gripping region 54 that facilitates screwing and unscrewing, the gripping region 54. Characterized in that the plastic deformation is carried out to allow the support member 50 to be held in position adjacent to Glow plug. It characterized in that it comprises at least one glow plug 2 according to any one of the preceding claims. Internal combustion engines. As a method of mounting the pressure sensor 14 in the head of the glow plug 2, A pressure sensor mounting method in which the pressure sensor is installed in the mating housing 48 and held by the support member 50, The support member 50 is held in place by plastic deformation of the wall portion 46 of the housing 48 which accommodates the sensor and the support member 50. How to install a pressure sensor.

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