HK1027157B - Vibration pickup with pressure sheath - Google Patents

Description

Vibration receiver with pressure sleeve

Prior Art

The invention relates to a vibration receiver with a pressure sleeve.

A vibration pickup with a pressure sleeve has already been described in DE-OS 4403660. Which is used as a knock sensor for monitoring the operating state of an internal combustion engine of an automobile. The pressure sleeve is fixed to the vibration-generating component, here mounted on the engine block, via a bearing region. The detected vibrations are knocking noises during operation of the internal combustion engine, which are transmitted via the pressure sleeve to the piezoceramic plate as sensor element for conversion into an electrical output signal that can be evaluated.

Here, the manner in which the sensor element is mounted or fixed on the pressure sleeve, and the manner in which the pressure sleeve is fixed on the vibrating member, have a great influence on the manner of manufacture. In this known vibration receiver, the fixation of the sensor element together with a plurality of components, such as springs, vibrating masses is done by a rather cumbersome manufacturing process.

THE ADVANTAGES OF THE PRESENT INVENTION

The object of the invention is to provide a vibration receiver with a pressure sleeve, which has a reduced number of components and a simple mounting and fixing.

According to the invention, a vibration pickup is proposed with a pressure sleeve, wherein the pressure sleeve is mounted indirectly or directly on a vibration-generating component by means of a fastening element and with a sensor element which is fastened under axial bias radially on the outside to the pressure sleeve and can be contacted electrically by contact lugs and connecting elements, wherein at least one of the contact lugs is a thin plate part with a radial gradient, such that the at least one contact lug is in the form of a coil spring between the sensor element and an axially adjacent element for generating the axial bias, wherein the seismic mass is provided with an internal thread and can be screwed directly onto the pressure sleeve for fastening the sensor element.

The vibration receiver according to the invention is particularly advantageous in that a separate coil spring for generating the axial bias is not required when the individual components are assembled together for fixing the sensor element. This is because the contact plate, which rests against the axial plane of the piezoceramic sensor element for making electrical contact, already takes the form of a coil spring and therefore does not have to be manufactured and mounted separately.

The pressure sleeve may be made of steel, brass or aluminium.

The contact plate can be stamped out of the plate in a simple manner in such a way that the contact plate is arched or inclined or sloped in the radial direction to produce the spring effect. In the stamping, it is advantageous to form a plug for connecting the line on the contact strip at the same time. The plug is thus integral with the contact from the beginning, so that the complex assembly steps for making the electrical connection of the components can be dispensed with.

The vibration receiver according to the invention can thus be produced from a smaller number of components in fewer assembly steps, so that special tools for mounting the coil spring and possibly separate soldered or welded contact pins are also superfluous. Thus, not only the manufacturing cost and the manufacturing time are saved, but also the manufacturing reliability is improved due to the simplification of the structure.

In a further preferred embodiment, a separate threaded ring or other fixing means for fixing the seismic mass can also be dispensed with. Here, the vibrating mass is produced with an internal thread and possibly an external hexagonal shape, so that a self-locking can be achieved thereby. Thus, while achieving high manufacturing quality and manufacturing reliability, the number of components can be further reduced, the manufacturing cycle can be shortened, and the weight can be reduced.

Further preferred embodiments are given in the dependent claims.

Drawings

Embodiments of a vibration receiver with a pressure jacket according to the invention are described below with reference to the drawings. Wherein:

FIG. 1 shows a cross-section of a knock sensor housing as a vibration receiver with a coil spring shaped contact piece;

fig. 2 is a cross-section of the contact sheet of fig. 1;

fig. 3 is a top view of the contact sheet of fig. 1;

FIG. 4 is a cross-section of a knock sensor having a vibrating mass with internal threads.

Description of the embodiments

Fig. 1 shows a knock sensor for an internal combustion engine as a vibration sensor, comprising a plastic housing 1, in which a pressure sleeve 2 is mounted, which is attached with its bottom surface 3 to an engine block, not shown here, whose vibrations are to be detected. On the outer circumference of the pressure jacket 2, the following elements are mounted from below to above: an insulating sheet 4, a first contact pad 5, a piezoceramic sheet 6 as sensor element, and, in turn, a second contact pad 7 and a second insulating sheet 4. On this structure is placed a vibrating mass 8, which is pressed against the piezoceramic plate 6 by a ring 9, wherein the ring 9 can be screwed or otherwise fixed.

In the integral connecting element 10 of the housing 1, which is produced in particular by plastic injection molding, electrical contacts 11 for the contact strips 5 are cast. Here, the electrical contacts 11 are made in one piece with the respective contact piece 5 or 7. Thus, electrical communication is made with both sides of the piezoceramic wafer 6 through the two contact pads 5 and 7. From the connection 11 a voltage is obtained which is generated by the piezo-ceramic plate 6 under compressive stress.

The pressure sleeve 2 has a central recess or bore 12 into which a fastening bolt, not shown in the figures, is inserted, by means of which the noise sensor is fastened directly or indirectly integrally to the engine block of the internal combustion engine.

Fig. 2 and 3 show an exemplary second contact strip 7, which also holds for the first contact strip 5. The contact lugs 7, like the contact lugs 5, also have a radial slope 13, which has the effect that each contact lug 5 or 7 rests only on its radial inside or outside on the piezoceramic plate 6 and, in correspondence with this, on its other side on the opposite insulating plate 4. The contact plates 5 and 7 each have a pre-tensioned spring action and are mounted between these elements. As can be seen from fig. 3, the contact plate 7 is stamped out of sheet metal in such a way that a web 14 is formed integrally with the contact plate 7, the web end having a plug-shaped thickened portion 15 formed by folding over a further sheet portion, which serves as the plug-shaped contact (11). The contact plate 5 is produced in the same way and has correspondingly dimensioned bridge pieces 14.

When the knock sensor is assembled, all the torque generated by the fixing bolts for mounting to the engine block is transmitted to the pressure sleeve 2 through the bottom surface 3, that is, when the knock sensor is fixed, no force acts on the piezoceramic wafer 6 as a sensor element.

Here, when the ring 9 is mounted, the bias is formed by the pressure plate spring-shaped contact pieces 5 and 7. The bias is chosen such that the axial forces acting on the piezoceramic wafers 6 do not just cause a permanent deterioration of the electrical signal, and is as far as possible independent of the thermal expansion and the compression of the pressure sleeve 2 that inevitably occurs during installation. The impulse generated by the seismic mass 8, which is proportional to the vibration of the internal combustion engine, is converted in the piezoceramic wafer 6 into voltage pulses, which can be read off with a corresponding measuring instrument.

In the exemplary embodiment according to fig. 4, components that have the same function as the components described with reference to fig. 1 to 3 have the same reference numerals. The seismic mass 16 in fig. 4 has an internal thread 17, by means of which the mass 16 can be screwed directly onto the pressure sleeve 2, so that the sensor element 6 is mounted between the elastic contact strips 5 and 7. To simplify assembly, the outside of the seismic mass 16 may be hexagonal. In this exemplary embodiment, the contact plates 5 and 7 are identical and are arranged symmetrically to one another. Thereby further simplifying the manufacturing process.

Claims (9)

1. Vibration receiver with a pressure sleeve, in which the pressure sleeve (2) is mounted indirectly or directly on a vibration-generating component by means of a fastening element, and with a sensor element (6) which is fastened under axial bias radially on the outside to the pressure sleeve (2) and can be contacted electrically by means of contact plates (5, 7) and a connecting element (11), in which at least one of the contact plates (5, 7) is a thin-plate part with a radial gradient (13), so that the at least one contact plate (5, 7) is in the form of a coil spring between the sensor element (6) and an axially adjacent element for generating the axial bias, characterized in that the vibrating mass (16) is provided with an internal thread (17) and can be screwed directly onto the pressure sleeve (2) for fixing the sensor element (6).

2. Vibration receiver according to claim 1, characterized in that the at least one contact piece (5, 7) is punched out of a thin plate and provided with a radial slope (13).

3. A vibration receiver according to claim 2, characterized in that the at least one contact piece (5, 7) and the bridging piece (14) are stamped out in one piece from a thin plate, wherein the bridging piece (14) has a thickened portion (15) at its end facing away from the respective contact piece (5, 7), which thickened portion functions as a plug-shaped joint (11).

4. A vibration receiver as claimed in claim 3, wherein the thickened portion is formed by folding a portion of the sheet.

5. Vibration receiver according to claim 3 or 4, characterized in that the two contact pieces (5, 7) are constructed identically and are arranged symmetrically to each other in such a way that the bridge pieces (15) are at the same height.

6. A vibration receiver as claimed in any one of claims 1 to 4, characterized in that the pressure jacket (2) is made of steel.

7. A vibration receiver as claimed in any one of claims 1 to 4, characterized in that the pressure sleeve (2) is made of brass.

8. A vibration receiver as claimed in any one of claims 1 to 4, characterized in that the pressure sleeve (2) is made of aluminum.

9. The vibration receiver as a knock sensor according to any one of claims 1 to 4, wherein the vibration generating member is an engine block of an internal combustion engine in an automobile.