Knock sensor with lower collar bored with attachment holes

Abstract

A knock sensor including a body, having a detection assembly able to measure vibrations, and a metal mount having a support ring on which the detection assembly rests, a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body. The mount includes a lower flange below the support ring and the lower flange is bored with attachment holes, which improve its sealing.

Claims

1. A knock sensor comprising: a body comprising: a detection assembly able to measure vibrations, a metal mount having a support ring on which the detection assembly rests, a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body, wherein the mount comprises a lower flange below the support ring and the lower flange is bored with attachment holes.

2. The knock sensor as claimed in claim 1, wherein the attachment holes are distributed on the lower flange periodically about a central axis of the mount.

3. The knock sensor as claimed in claim 2, wherein at least one of the attachment holes has a boring axis substantially parallel to a central axis of the mount.

4. The knock sensor as claimed in claim 1, wherein at least one of the attachment holes has a boring axis substantially parallel to a central axis of the mount.

5. The knock sensor as claimed in claim 1, wherein at least one of the attachment holes has an internal wall that is chamfered at a lower end.

6. The knock sensor as claimed in claim 1, wherein the support ring comprises circular crenellations in a peripheral face.

7. The knock sensor as claimed in claim 1, wherein the mount is an assembly of two components, with a lower component comprising the lower flange and the support ring, and an upper component, the two components being kept assembled by the peripheral casing.

8. The knock sensor as claimed in claim 7, wherein the upper component has an external lower shoulder that bears against an internal upper shoulder belonging to the lower component.

9. The knock sensor as claimed in claim 1, wherein the mount comprises an upper flange which extends radially above the detection assembly.

10. A vehicle comprising a knock sensor as claimed in claim 1.

11. A knock sensor comprising: a body comprising: a detection assembly able to measure vibrations, a metal mount having a support ring on which the detection assembly rests, and a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body, wherein the mount comprises a lower flange below the support ring and the lower flange is bored with attachment holes, and wherein the lower flange comprises a peripheral rim extending upward and with a peripheral face of the support ring delimiting a groove into which the attachment holes open.

12. A knock sensor comprising: a body comprising: a detection assembly able to measure vibrations, a metal mount having a support ring on which the detection assembly rests, and a peripheral casing to protect the detection assembly, made from a thermoplastic material applied by overmolding at least in part around the body, wherein the mount comprises a lower flange below the support ring and the lower flange is bored with attachment holes, and wherein the mount has an upper portion which comprises a plurality of circular grooves, and these circular grooves have a depth that decreases from one groove to the next, from the top down.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of aspects of the invention will become apparent from the following description, given with reference to the appended figures that are given by way of non-limiting example and in which identical references are given to similar objects.

(2) FIG. 1 is a view in axial section of a first embodiment of a knock sensor according to an aspect of the invention.

(3) FIG. 2 is a perspective view of the mount of the knock sensor of FIG. 1.

(4) FIG. 3 is a view in axial section of a second embodiment of a knock sensor according to an aspect of the invention.

(5) FIG. 4 is a perspective view of the mount of the knock sensor of FIG. 3.

(6) FIG. 5 is a perspective view of the knock sensor of FIGS. 3 and 4 (with the mount and casing assembled).

(7) FIG. 6 is a view in axial section of a third embodiment of a knock sensor according to an aspect of the invention.

(8) FIG. 7 is a perspective view of the mount of the knock sensor of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) All the knock sensors C illustrated comprise a vibration detection body and a peripheral body-protecting casing 2 made of a thermoplastic material applied by overmolding around said body, at least in part.

(10) The body comprises a metal mount 1 and a detection assembly 3.

(11) The metal mount 1 comprises, from the top down, namely from its upper end 11 to its lower end 12 (the references 11 and 12 also designating the respectively upper and lower ends of the knock sensor C): an upper portion 5, a central portion 9 extending (radially) opposite the detection assembly 3, the upper portion 5 having a maximum external diameter equal to the maximum external diameter of the central portion 9 and being able to have a minimum external diameter that is smaller if it is provided with circular grooves 51 as it is in the two examples of FIGS. 1 to 5, a support ring 6 on which the detection assembly 3 rests, the support ring 6 having a maximum external diameter greater than the maximum external diameter of the central portion 9, and, according to an aspect of the invention, a flange 7 bored with attachment holes 8. By definition, the flange 7 extends radially beyond the support ring 6, which means to say that it has an external diameter greater than the maximum external diameter of the support ring 6.

(12) For preference, the attachment holes 8 are distributed periodically about the central axis of the mount. For preference, the mount, considered without the attachment holes, exhibits symmetry of revolution. This is the case in all the examples illustrated.

(13) The mount 1 also comprises a central bore 10 to accept a fixing screw (not depicted) used to anchor the mountand the knock sensor Cin the engine block.

(14) The detection assembly 3 comprises a plurality of components such as, for example, a piezoelectric element 31, electrical contact elements 32, 33, a seismic mass 34 used to amplify the signal, and insulating elements. Electrical insulation between the detection assembly 3 and metallic mount 1 is afforded by a layer of thermoplastic belonging to the casing 2 between the central portion 9 of the mount and the detection assembly 3, and by an insulating washer 35 between the contact 32 and the support ring 6.

(15) The peripheral casing 2 comprises a portion 21 forming a cap around the mount 1 and a section 22 forming a connection end-piece, the section 22 delimiting a plug socket 23 incorporating an electrical contact 24 and intended to accept a complementary plug for connecting the knock sensor C to a connecting cable (not depicted) connected to a computer of the vehicle (not depicted).

(16) The three embodiments illustrated moreover differ in terms of the following features regarding their mount.

(17) In the first embodiment (FIGS. 1 and 2) and in the third embodiment (FIGS. 6 and 7), the attachment holes 8 of the mount are all identical, with a circular cross section. They exhibit, from the top down, an upper portion of constant cross section then a flared lower section of increasing cross section forming a chamfer 81. As an alternative, the attachment holes (or some of them) may be a constant cross section over their entire height, which means to say may be fully cylindrical.

(18) In the second embodiment (FIGS. 3 to 5), the mount comprises circular attachment holes 8 identical to those of the first and third embodiments and two diametrically opposed oblong attachment holes 82 (not visible in FIG. 4). The oblong holes may be fully cylindrical or may have a lower chamfer like the circular holes previously described.

(19) The lower flange 7 of the second embodiment (FIGS. 3 and 4) additionally comprises a rim 71 which extends axially upward and therefore, with the support ring 6, delimits a groove 72. The groove 72 plays a part in trapping thermoplastic material in order to strengthen the assembly between mount and casing.

(20) The support ring 6 of the first embodiment has crenellations 61 extending around its entire periphery (and this is why such crenellations were qualified as circular crenellations earlier). In the example illustrated, these crenellations have a cross section (taken on any axial plane containing the central axis of the mount) that is trapezoidal, but this cross section could have a different shape, being for example square or dovetailed. These crenellations increase the seepage line between the lower end 12 of the mount and the detection assembly 3. The third embodiment (FIGS. 6 and 7) is likewise provided with circular crenellations at its support ring, which is not the case in the second embodiment (FIGS. 3 to 5).

(21) The upper portion 5 of the first embodiment (FIGS. 1 and 2) has grooves 51 extending around its entire periphery and referred to as upper grooves in the overall description above. In the example illustrated, these upper groups 51 have a cross section (taken on any axial plane) that is square, but this cross section could have a different shape, being for example trapezoidal or dovetailed. These upper grooves 51 increase the seepage line between the upper end 11 of the mount and the detection assembly 3. The second embodiment (FIGS. 3 to 5) is likewise provided with upper grooves on its upper portion 5. It also has upper grooves on an upper part of its central portion 9, notably facing the seismic mass 34, which is not the case with the central portion of the first embodiment, which is fully cylindrical. The upper grooves 51 of the first embodiment (FIGS. 1 and 2) has a depth that is (radially) constant, whereas the upper grooves 51a, 51b, 51c, 51d, 51e, etc. of the second embodiment have a depth that decreases from the top down, with a maximum external diameter that remains constant, which means to say that the groove 51d starts from the same external cylinder but is not as deep as the groove 51a (which means that the bottoms of the two grooves are not inscribed in the same cylinder). In other words, the thickness of material of the upper and central portions of the mount in the region of the grooves increases from the top down, from one groove to the next. This increase in thickness compensates for the deformation (with greater crushing of the thickness of the mount in the bottom part of the central portion 9) that the mount experiences when the knock sensor C is mounted in the engine block.

(22) The mount of the third embodiment (FIGS. 6 and 7) is made up of two components 13, 14, whereas the mount of the first and second embodiments is made as a single component. The component 13 comprises the upper portion 5 and the central portion 9 of the mount, whereas the component 14 comprises the support ring 6 and the lower flange 7. Where the two components meet, an external shoulder 15 of the component 13 rests on an internal shoulder 16 of the component 14. The two-part design of the mount offers various advantages. It makes it possible to provide an upper flange 52 which significantly increases the seepage line between the upper end 11 and the detection assembly 3 and contributes to the strength of the mount/casing assembly: the casing is clamped between the upper flange 52 and the support ring 6 extended by the lower flange 7, while at the same time holding together the components 13 and 14 that it encapsulates. Creating an upper flange in a one-part mount such as that of the first embodiment is also possible, but less advantageous (if the mount is produced by machining) because it necessitates starting from an unfinished component of larger external diameter and leads to a significant wastage of material. Creating a two-part mount as illustrated is particularly simple and inexpensive.

(23) The features of the various embodiments illustrated may be combined. For example, upper circular grooves may be formed in the component 13 just below the upper flange 52 of the third embodiment. A groove 72 may be provided in the first embodiment. Other combinations and other alternate forms are possible, provided that they still fall within the scope delimited by the attached claims. By way of example, the detection assembly is not limited to the one illustrated; the attachment holes may have diverse and varying cross sections and the axis along which they are bored may be inclined (which is to say not parallel to the central axis ); etc.

(24) Thus, the attachment holes according to an aspect of the invention allow better attachment of the casing material around the mount and considerably reduce the effects of the expansion of the mount along the axis perpendicular to the central axis.

(25) The chamfered wall of the attachment holes, the peripheral rim, the groove, the circular crenellations and the circular grooves make it possible to improve the sealing of the knock sensor still further.