Acceleration Transducer

Abstract

To provide an acceleration transducer including at least one piezoelectric element, at least one seismic mass, and a main body.SOLUTION: Each of seismic mass 11, 11', 11'', which is attached one of piezoelectric elements 10, 10', 10'', upon acceleration, exerts a normal force along a normal axis a proportional to acceleration onto the piezoelectric element, the piezoelectric element generates piezoelectric interference electric charges on lateral surfaces 130, 140, 150, 160 under effect of the normal force along the normal axis, one piezoelectric element includes at least one lateral surface including at least one of lateral surface coatings 131, 133, 141, 151, 161 having conductivity in some areas thereof, the lateral surface coating having conductivity extracts the piezoelectric interference electric charges generated by the normal force along the normal axis.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an acceleration transducer according to the preamble of the independent claim. [Background technology]

[0002] The acceleration of a physical object is measured in many different applications, such as robotics, energy generation, and transportation. For this purpose, acceleration is detected in the form of an impact acting on the physical object or a vibration of the physical object. The acceleration is determined by the gravitational acceleration g=9.81 msec -2 The acceleration is expressed as a multiple of . A typical range of acceleration to be detected is + / - 500g with a measurement range of 2Hz to 10kHz. To detect acceleration, an accelerometer is fixed to the physical object.

[0003] Document CH399021A1 provides an acceleration transducer of the above mentioned kind, comprising a seismic mass, a piezoelectric system and a main body. The acceleration transducer comprises a housing for protecting the acceleration transducer from harmful environmental influences, the housing containing the seismic mass, the piezoelectric system and the main body. The acceleration transducer is attached to the physical object by the housing. When an acceleration occurs, the seismic mass exerts a force on the piezoelectric system that is proportional to the acceleration of the seismic mass. The piezoelectric system comprises a number of flat disks made of a piezoelectric material with high sensitivity due to the piezoelectric longitudinal effect. Under the influence of the acting force, the piezoelectric material generates a piezoelectric charge, the amount of generated piezoelectric charge being proportional to the magnitude of the force. By means of the piezoelectric longitudinal effect, a piezoelectric charge is generated on the face of the disk against which the force acts as a normal force. Each disk has two faces, and on these two faces a piezoelectric charge with opposite polarity is generated. Furthermore, the piezoelectric system comprises thin electrodes made of a conductive material for picking off the piezoelectric charge from the two end faces. Each electrode has a surface with the size of the end face. With said surface, the electrodes are in direct and complete contact with the end face. In addition, the piezoelectric system is mechanically preloaded between the seismic mass and the main body by a preloading sleeve. This mechanical preloading seals the micropores between the end faces and the electrodes so that all the generated piezoelectric charges can be obtained. This is important for the linearity of the acceleration transducer. Linearity means the ratio of the number of piezoelectric charges to the magnitude of the force. The piezoelectric charges can be electrically transmitted and represent an acceleration signal. The electrically transmitted acceleration signal can be electrically converted in the converter unit.

[0004] DE69405962T2 further describes an acceleration transducer comprising a seismic mass and a piezoelectric system located on a printed circuit board. The acceleration transducer detects acceleration according to the transverse shear effect as a shear force acting along an axis. The piezoelectric system is arranged between the seismic mass and the printed circuit board. A converter unit is located on the printed circuit board.

[0005] Thus, the piezoelectric system of CH399021A1 is sensitive only to normal forces along one axis, and the piezoelectric system of DE69405962T2 is sensitive only to shear forces along one axis, but it is desirable to have an acceleration transducer that can simultaneously detect acceleration along multiple axes of a Cartesian coordinate system.

[0006] Document RU1792537C1 discloses an acceleration transducer capable of detecting acceleration in three physical dimensions. To a cubic-shaped main body with six surfaces, a piezoelectric system is attached, which comprises six flat disks made of piezoelectric material, and six seismic masses. Each of two surfaces is oriented in a direction perpendicular to one of three axes perpendicular to each other. This axis is therefore referred to hereafter as the normal axis. At each of the six surfaces, a flat disk is introduced between the surface and the seismic mass. The disks are mechanically preloaded in contact with the main body by means of an external preloading housing. The piezoelectric system therefore comprises a pair of disks at each of the three normal axes. The disks have a high sensitivity to transverse shear effects. With the transverse shear effect, a piezoelectric charge is generated at the end faces of the disks, where a shear force tangential to the normal axis acts. This axis is therefore referred to hereafter as the main tangential axis. Additionally, the piezoelectric system includes electrodes made of a conductive material for extracting piezoelectric charge from the edge of the disk.

[0007] According to RU1792537C1, a piezoelectric system comprises a pair of disks made of a piezoelectric material exhibiting high sensitivity to shear forces acting along a principal tangential axis in each of three normal axes.

[0008] Unfortunately, it is unavoidable that piezoelectric materials have more or less high sensitivity to shear forces acting along various axes. Thus, a piezoelectric material with high sensitivity to shear forces along the main tangential axis also exhibits a sensitivity, albeit low, to shear forces acting along an axis perpendicular to the main tangential axis and perpendicular to the normal axis, which will therefore be referred to hereafter as the sub-tangential axis. Both shear forces, i.e. those acting along the main tangential axis and those acting along the sub-tangential axis, generate piezoelectric charges on the edge surface of the disk. As an example, the piezoelectric material quartz has a high sensitivity to shear forces along the main tangential axis, which is more than seven times higher than the low sensitivity to shear forces acting along the sub-tangential axis.

[0009] Therefore, the low sensitivity of the piezoelectric material for shear forces acting along the sub-tangential axis may distort the detection of shear forces along the main tangential axis. Therefore, each piezoelectric charge is hereafter referred to as a piezoelectric interference charge. In order to avoid such distortion, RU1792537C1 discloses electrically connecting a pair of disks in series with opposite polarity in each of the three normal axes. This has the advantage that the shear forces acting along the sub-tangential axis generate an equal number of piezoelectric interference charges on the end faces of each of the two disks, but these have opposite polarity and therefore cancel each other out when taken in series.

[0010] Furthermore, document EP 054680 A1 describes an acceleration transducer with a piezoelectric system for detecting acceleration with high sensitivity according to the transverse shear effect as shear forces acting along three main tangential axes perpendicular to each other. In the embodiment shown in FIG. 8, the piezoelectric system is composed of six disks made of piezoelectric material, where a pair of disks with opposite polarity are electrically connected in series in each of the three main tangential axes. The acceleration transducer requires only three seismic masses, one for each of the three main tangential axes. The piezoelectric interference charges resulting from the shear forces along the secondary tangential axes are nulled in each of the three main tangential axes when obtained in series.

[0011] Furthermore, US Patent No. 5,539,270 (A1) relates to an acceleration transducer for detecting acceleration in three physical dimensions. For each dimension a piezoelectric system is provided, each comprising two plates made of piezoelectric material. The end faces of the two plates facing towards each other are materially bonded to each other. This material connection is electrically insulating. On the end faces of the plates facing away from each other electrodes are attached, which extract the piezoelectric charge generated under the effect of a normal force. The three piezoelectric systems are mechanically attached to a support. The support comprises an electrical conductor for conducting the piezoelectric charge from the electrodes. No seismic mass is provided.

[0012] Often, the space available to mount an acceleration transducer on a physical object is limited. Therefore, it is often necessary to mount an acceleration transducer on a 50 cm 3 It must have small outer dimensions of less than 10 kHz. Furthermore, it is desired to measure frequencies above 10 kHz. Furthermore, the acceleration transducer must have a small weight, since the resonant frequency of an acceleration transducer is inversely proportional to its weight.

[0013] Document CN201152880Y discloses an acceleration transducer comprising a piezoelectric system, a seismic mass and a main body. The main body has a cylindrical shape and terminates at a vertical end face along a vertical axis. The piezoelectric system is mechanically preloaded between the main body and the seismic mass by means of a preloading sleeve along a normal axis that is perpendicular to the vertical axis. The preloading sleeve has a hollow cylindrical shape and terminates at a lateral surface in the plane of the vertical end face of the main body. The seismic mass is formed as a disk and terminates at a lateral surface, also in the plane of the vertical end face of the main body. A converter unit in the form of a charge amplifier is arranged in this plane on the lateral surfaces of the preloading sleeve and the seismic mass as well as on the vertical end face of the main body, thereby saving space.

[0014] The disadvantage of this arrangement of the preloading sleeve and the converter unit on the lateral surface of the seismic mass and also on the vertical end face of the main body is that a force shunt is formed between the seismic mass and the main body. As a result, the seismic mass cannot vibrate freely under the effect of acceleration, and the force acting on the piezoelectric system due to the inertia of the seismic mass is disturbed, so that this force is not proportional to the acceleration, and in addition, the piezoelectric charge generated by the piezoelectric material is not proportional to the acceleration to be detected. The force shunt therefore distorts the measurement of the acceleration. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] CH399021A1 [Patent Document 2] DE69405962T2 [Patent Document 3] RU1792537C1 [Patent Document 4] EP054680A1 [Patent Document 5] U.S. Patent No. 5,539,270(A1) [Patent Document 6] CN201152880Y Summary of the Invention [Problem to be solved by the invention]

[0016] A first object of the present invention is to provide an acceleration transducer capable of simultaneously detecting acceleration in several physical dimensions. A second object of the present invention is to provide an acceleration transducer which detects acceleration with as little distortion as possible. According to a third object of the present invention, the acceleration transducer has small outer dimensions and a low weight. A fourth object of the present invention is to provide an acceleration transducer which is configured for high measure of vibration frequencies above 10 kHz. According to a fifth object of the present invention, the acceleration transducer can be manufactured at low cost. [Means for solving the problem]

[0017] At least one of these objects is achieved by the features of the independent claims.

[0018] The present invention relates to an acceleration transducer comprising at least one piezoelectric element, at least one seismic mass and a main body, said acceleration transducer being arranged in a Cartesian coordinate system having three axes, one of which is a vertical axis, said main body having a tangential side and a normal side face, said tangential side being arranged tangentially to the vertical axis and said normal side being arranged normal to the vertical axis, said acceleration transducer comprising exactly three piezoelectric elements and exactly three seismic masses, exactly one piezoelectric element attached to each of the three tangential sides, one seismic mass attached to each of the three piezoelectric elements, wherein upon acceleration the seismic mass exerts a shear force on the piezoelectric element which is proportional to said acceleration, each of the three piezoelectric elements having a high sensitivity for the shear force along a main tangential axis exerted by the seismic mass attached to the piezoelectric element, and wherein for each of the three piezoelectric elements the main tangential axis is a different one of the three axes.

[0019] Thus, the acceleration transducer according to the invention can simultaneously detect acceleration along three axes. For this purpose, each of the three axes is equipped with exactly one piezoelectric element that has a high sensitivity for the shear force to be detected and detects the shear force to be detected independently of the other two piezoelectric elements. The acceleration transducer according to the invention has a remarkably compact design, since it requires only three piezoelectric elements and three seismic masses, which are arranged in a space-saving manner on the three tangential sides of the main body. In contrast, RU1792537C1 teaches the use of six piezoelectric elements and six seismic masses fixed to the six faces of a cubic-shaped main body. Thus, according to the invention, only half the number of piezoelectric elements and seismic masses is required, with a corresponding reduction in the overall space required.

[0020] Further advantageous embodiments of the invention are the subject matter of the characteristics of the attached claims.

[0021] In the following the invention will be explained in more detail by means of exemplary embodiments with reference to the drawings. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 shows a part of a first embodiment of an acceleration transducer comprising a transducer unit. [Diagram 2] FIG. 2 shows a part of a second embodiment of an acceleration transducer comprising a transducer unit; [Diagram 3] FIG. 2 shows a converter unit comprising a converter unit of the acceleration converter according to FIG. 1; [Figure 4] FIG. 3 shows a converter unit comprising a converter unit of the acceleration converter according to FIG. 2; [Diagram 5] FIG. 5 shows an exploded view of a part of the converter unit according to FIGS. [Figure 6] FIG. 6 shows a top view of the converter unit according to FIGS. 1 to 5 under the effect of acceleration. [Figure 7]FIG. 6 is a first diagram showing a first embodiment of a piezoelectric element of the transducer unit according to FIGS. 1 to 5; [Figure 8] FIG. 8 shows a second view of an embodiment of the piezoelectric element according to FIG. [Figure 9] FIG. 6 is a first view showing a second embodiment of a piezoelectric element of the transducer unit according to FIGS. [Figure 10] FIG. 10 shows a second view of a second embodiment of the piezoelectric element according to FIG. [Figure 11] FIG. 6 is a schematic diagram showing the transmission of piezoelectric charges in the converter unit according to FIGS. [Figure 12] FIG. 12 is a schematic diagram showing a high-pass filter of a converter unit of the converter unit according to FIG. 11. [Figure 13] FIG. 12 is a schematic diagram showing a low-pass filter of a converter unit of the converter unit according to FIG. 11. [Figure 14] FIG. 3 shows a first step in the assembly of the acceleration transducer according to FIG. 2, in which the signal lines are introduced into the housing. [Figure 15] FIG. 3 shows a second step in the assembly of the acceleration transducer according to FIG. 2, in which the signal wires are present in the cast material within the housing. [Figure 16] FIG. 3 shows a third step of the assembly of the acceleration transducer according to FIG. 2, in which the signal wires present in the casting material are exposed in some areas within the housing. [Figure 17] 3 shows a fourth step of the assembly of the acceleration transducer according to FIG. 2, in which the transducer unit is introduced into the housing; FIG. [Figure 18] FIG. 4 shows a fifth step of the assembly of the acceleration transducer according to FIG. 2, in which the converter units of the converter unit are electrically connected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1 and 2 show a part of each of two embodiments of an acceleration transducer 1 according to the invention. The acceleration transducer 1 comprises a transducer unit 1.1, a housing 1.2, a converter unit 1.3 and a signal output 1.4. The acceleration transducer 1 is arranged in a Cartesian coordinate system with three axes x, y, z, also called the transverse axis x, the longitudinal axis y and the vertical axis z.

[0024] The housing 1.2 protects the acceleration transducer 1 from harmful environmental influences such as contamination (dust, moisture, etc.) and from the influence of electrical and electromagnetic interference in the form of electromagnetic radiation. The housing 1.2 is made of a mechanically resistant material such as pure metal, nickel alloy, cobalt alloy, iron alloy, etc. The housing 1.2 has a rectangular cross section with a width along a transverse axis x preferably less than 5 cm, a length along a longitudinal axis y preferably less than 5 cm, and a height along a vertical axis z preferably less than 2 cm, so that the housing 1.2 has a length of 50 cm or less. 3 The housing 1.2 has small outer dimensions of less than 1.2 mm. The housing 1.2 has the shape of a pot and comprises a housing opening 1.20 and a housing bottom 1.23. The dimensions of the housing opening 1.20 are such that the transducer unit 1.1 can be introduced into the housing 1.2, fixed to the housing bottom 1.23 and connected to the signal output 1.4 through the housing opening 1.20. In the context of the present invention, the term "connection" is understood to mean an electrical connection as well as a mechanical connection. The housing opening 1.20 can be sealed by a housing cover 1.21. Preferably, the housing opening 1.20 is sealed by material bonding, such as welding, soldering, gluing, etc. The acceleration transducer 1 is attached by the housing 1.2 to a physical object whose acceleration is to be detected. Any attachment method can be chosen.

[0025] The transducer unit 1.1 comprises a first piezoelectric element 10, a second piezoelectric element 10' and a third piezoelectric element 10'', a first seismic mass 11, a second seismic mass 11' and a third seismic mass 11'', and a main body 12. The first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', and the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'' are attached to the main body 12. Furthermore, the main body 12 is attached to a housing 1.2. Preferably, the main body 12 is attached to the housing 1.2 by material bonding, such as gluing, soldering, etc.

[0026] The first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' are made of a material selected from the group consisting of quartz (single crystal of SiO2), calcium gallogermanate (Ca3Ga2Ge4O 14 or CGG), Langasite (La3Ga5SiO 14 The piezoelectric element 10 is made of a piezoelectric material such as gallium oxide or LGS, tourmaline, gallium orthophosphate, piezoceramics, etc. The first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' have a high sensitivity for the forces to be measured. The first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' have a rectangular cross section, preferably with a diameter of 1 cm. 2 It has a surface area of ​​less than 1 mm and preferably a thickness of less than 2 mm. A person skilled in the art having an understanding of the present invention may also use piezoelectric elements having different shapes and cross sections, such as circular.

[0027] Preferably, the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'' are made of a high density material, such as iridium, platinum, tungsten, gold, etc. For acceleration transducers 1 with smaller outer dimensions, the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'' preferably have a mass density of 19 g / cm 3 The cross section of the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'' preferably has a density of more than 1 cm 2It is rectangular with a smaller surface area and preferably a thickness of less than 5 mm. A person skilled in the art, having understood the present invention, can also use seismic masses with different shapes and cross sections, such as circular. Furthermore, a person skilled in the art can also use seismic masses made of materials with lower density, such as steel, ceramics, etc.

[0028] The main body 12 is made of a material having a high mechanical stiffness with a low density, such as Al2O3 ceramic, Al2O3 ceramic, sapphire, etc. The high mechanical stiffness of the main body 12 is necessary to inelastically transmit the acceleration to be detected from the housing 1.1 onto the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11''. For a high mechanical stiffness of the acceleration transducer 1, the main body 12 preferably has a high elastic modulus of 350 GPa to 470 GPa. For a low weight of the acceleration transducer 1, the main body 12 preferably has a low modulus of elasticity of 4 g / cm 3 The main body 12 is preferably a cube having six sides 12.1, 12.2, 12.3, 12.4, 12.6, 12.7. Four tangential sides 12.1, 12.2, 12.3, 12.4 are arranged tangentially to the vertical axis z. Two vertical sides 12.6, 12.7 are arranged perpendicularly to the vertical axis z. The sides 12.1, 12.2, 12.3, 12.4, 12.6, 12.7 are of substantially equal size. Each side 12.1, 12.2, 12.3, 12.4, 12.6, 12.7 has a size of 1 cm. 2 In the context of the present invention, the adverb "substantially" has the meaning of "+ / -10%". Each of the x-, y- and z-axes is perpendicular to two of the sides. A person skilled in the art aware of the present invention may also use main bodies having different shapes and surfaces of different shapes, such as circular.

[0029] A first seismic mass 11 and a first piezoelectric element 10 are attached to a first tangential side 12.1 of the main body 12. A second seismic mass 11' and a second piezoelectric element 10' are attached to a second tangential side 12.2 of the main body 12. A third seismic mass 11'' and a third piezoelectric element 10'' are attached to a third tangential side 12.3 of the main body 12. Here, each of the piezoelectric elements 10, 10', 10'' is located between a tangential side 12.1, 12.1, 12.3 and the seismic masses 11, 11', 11'', respectively. A fourth tangential side 12.4 is free.

[0030] The attachment of the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'', as well as the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' to the main body 12 is achieved by means of first inner connection means 15, second inner connection means 15' and third inner connection means 15'', as well as first outer connection means 16, second outer connection means 16' and third outer connection means 16''. The attachment is performed by material bonding, such as gluing, thermocompression, etc. Such mechanical attachment of the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'', and the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', by the first inner connecting means 15, the second inner connecting means 15' and the third inner connecting means 15'', and the first outer connecting means 16, the second outer connecting means 16' and the third outer connecting means 16'', makes the assembly of the acceleration transducer 1 easy and can be carried out quickly and cost-effectively.

[0031] The first inner connection means 15, the second inner connection means 15', and the third inner connection means 15'', and the first outer connection means 16, the second outer connection means 16', and the third outer connection means 16'' may be an adhesive that can be chemically cured or physically hardened, or a combination of adhesives that can be chemically cured and physically hardened. Preferably, the first inner connection means 15, the second inner connection means 15', and the third inner connection means 15'', and the first outer connection means 16, the second outer connection means 16', and the third outer connection means 16'' are made of an adhesive, such as epoxy, polyurethane, cyanoacrylate, methyl methacrylate, etc. The ... 12 Ωmm 2 It is an electrical insulator with an electrical resistivity of more than 1 / m.

[0032] As shown in FIG. 5, a first piezoelectric element 10 is attached to a first tangential side 12.1 via a first inner connection means 15. A first seismic mass 11 is attached to the first piezoelectric element 10 via a first outer connection means 16. A second piezoelectric element 10' is attached to a second tangential side 12.2 via a second inner connection means 15'. A second seismic mass 11' is attached to the second piezoelectric element 10' via a second outer connection means 16'. A third piezoelectric element 10'' is attached to a third tangential side 12.3 via a third inner connection means 15''. A third seismic mass 11'' is attached to the third piezoelectric element 10'' via a third outer connection means 16''.

[0033] Preferably, the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' are attached to the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11'' and the main body 12 in a shear-resistant manner by first inner connecting means 15, second inner connecting means 15' and third inner connecting means 15'', and first outer connecting means 16, second outer connecting means 16' and third outer connecting means 16''.

[0034] Each of the first inner connection means 15, the second inner connection means 15', and the third inner connection means 15'', and each of the first outer connection means 16, the second outer connection means 16', and the third outer connection means 16'' has a rectangular cross section, preferably with a diameter of 1 cm. 2 and preferably has a thickness of less than 0.1 mm. A person skilled in the art having understood the present invention may also use inner and outer connecting means of different shapes and cross sections, such as circular.

[0035] The first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' have a high sensitivity to transverse shear effects along a main tangential axis h, a low sensitivity to transverse shear effects along a sub-tangential axis n, and a low sensitivity to piezoelectric transverse effects along a normal axis a. The main tangential axis h is a different one of the three axes x, y, z for each of the three piezoelectric elements 10, 10', 10''. The sub-tangential axis n is a different one of the three axes x, y, z for each of the three piezoelectric elements 10, 10', 10''. The normal axis a is a different one of the three axes x, y, z for each of the three piezoelectric elements 10, 10', 10''.

[0036] The transverse shear effect along the primary tangential axis h or the secondary tangential axis n generates piezoelectric charges at the end faces of the first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' that are the same as the end faces to which the shear force is applied along the primary tangential axis h or the secondary tangential axis n.

[0037] The piezoelectric transverse effect generates piezoelectric charges on lateral surfaces of the first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'', which are perpendicular to the end faces of the first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'', where a normal force acts along the normal axis a.

[0038] An increased sensitivity results in more piezoelectric charge being generated for a given magnitude of force. In the present invention, the terms "high sensitivity" and "low sensitivity" are interrelated. Each of the three piezoelectric elements 10, 10', 10'' with a high sensitivity for shear forces along the main tangential axis h generates at least five times more piezoelectric charge per unit force compared to a low sensitivity for shear forces along the secondary tangential axis n or for normal forces along the normal axis a.

[0039] Therefore, the piezoelectric material is selected so that the detection of acceleration takes into account a large proportion of the piezoelectric charges generated by the transverse shear effect along the main tangential axis h. Hereinafter, the piezoelectric charges generated according to the transverse shear effect along the minor tangential axis n and the piezoelectric transverse effect along the normal axis a are referred to as piezoelectric interference charges.

[0040] 6 shows a top view of the transducer unit 1.1 during acceleration. The acceleration causes a force F to be exerted by the first seismic mass 11, the second seismic mass 11' and the third seismic mass 11' on the end faces of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10''. By way of example, the force F acts parallel along the longitudinal axis, as indicated by the arrows.

[0041] The first piezoelectric element 10 has a high sensitivity for shear forces along its longitudinal axis y, which is its main tangential axis h. Because the force F acts along the longitudinal axis y, the first piezoelectric element 10 generates piezoelectric charges due to the force F according to the transverse shear effect on its end faces. The first piezoelectric element 10 has a low sensitivity for shear forces acting along its minor tangential axis n, which is the vertical axis z, and a low sensitivity for normal forces acting along its transverse axis x, which is its normal axis a. The force F acts along the longitudinal axis y, where the force F exerts a torque along the vertical axis z. The first piezoelectric element 10 generates piezoelectric interference charges due to the transverse shear effect on its end faces due to this torque.

[0042] The second piezoelectric element 10' exhibits high sensitivity for shear forces along the transverse axis x, which is its main tangential axis h. However, a force F acts along the longitudinal axis y, and the second piezoelectric element 10' does not generate piezoelectric charges on its end surfaces due to the force F. The second piezoelectric element 10' has low sensitivity for shear forces acting along the vertical axis z, which is its minor tangential axis n, and low sensitivity for normal forces acting along the longitudinal axis y, which is its normal axis a. Because the force F acts along the longitudinal axis y, the second piezoelectric element 10' generates piezoelectric interference charges on its side surfaces according to the piezoelectric transverse effect due to the force F.

[0043] Furthermore, the third piezoelectric element 10'' exhibits high sensitivity for shear forces along its main tangential axis h, the normal axis z. However, a force F acts as a shear force along the longitudinal axis y, and the third piezoelectric element 10'' does not generate piezoelectric charges at its end faces due to the force F. The third piezoelectric element 10'' has low sensitivity for shear forces acting along its secondary tangential axis n, the longitudinal axis n, and low sensitivity for normal forces along its normal axis a, the transverse axis x. A force F acts along the longitudinal axis y, exerting a torque along the normal axis z. The third piezoelectric element 10'' generates piezoelectric interference charges according to the transverse shear effect on its end faces due to this torque.

[0044] Figures 7 and 8 show detailed views of a first embodiment of the first, second and third piezoelectric elements 10, 10' and 10'' of the transducer unit 1.1. Figures 9 and 10 show detailed views of a second embodiment of the first, second and third piezoelectric elements 10, 10' and 10'' of the transducer unit 1.1. The first, second and third piezoelectric elements 10, 10' and 10'' have two end faces 110, 120 and four side surfaces 130, 140, 150, 160.

[0045] Each of the three piezoelectric elements 10, 10', 10'' comprises a first end face 110 and a second end face 120. Each end face 110, 120 lies in a plane defined by a main tangential axis h and a sub-tangential axis n. In this plane, the sub-tangential axis n is perpendicular to the main tangential axis h. Furthermore, the normal axis a is perpendicular to this plane. Under the effect of a shear force along the main tangential axis h, each of the three piezoelectric elements 10, 10', 10'' generates a piezoelectric charge at the two end faces 110, 120. Furthermore, under the effect of a shear force along the sub-tangential axis n, each of the three piezoelectric elements 10, 10', 10'' generates a piezoelectric interference charge at the two end faces 110, 120. Each of the three piezoelectric elements 10, 10', 10'' comprises a lateral surface 130, 140, 150, 160. The lateral surfaces 130, 140, 150, 160 are parallel to the normal axis a. The lateral surfaces 130, 140, 150, 160 comprise a first lateral surface 130, a second lateral surface 140, a third lateral surface 150, and a fourth lateral surface 160. The first lateral surface 130 and the fourth lateral surface 160 are perpendicular to the minor tangential axis n of the piezoelectric element 10, 10', 10". The second lateral surface 140 and the third lateral surface 150 are perpendicular to the major tangential axis h of the piezoelectric element 10, 10', 10".

[0046] When a normal force acts along the normal axis a, each of the three piezoelectric elements 10, 10', 10'' generates a piezoelectric interference charge on the four lateral surfaces 130, 140, 150, 160.

[0047] Thus, the piezoelectric charge generated due to the shear force to be measured occurs only on the two end faces 110, 120 of the piezoelectric element. In addition, piezoelectric interference charges occur both on the two end faces 110, 120 and on the four side surfaces 130, 140, 150, 160.

[0048] The end faces 110, 120 are provided with at least an electrically conductive end face coating 111, 121 on a portion of their area. The area of ​​the electrically conductive end face coating 111, 121 may be between 90% and 100% of the area of ​​the end faces 110, 120. The side faces 130, 140, 150, 160 are provided with at least an electrically conductive side face coating 131, 141, 151, 161 on a portion of their area. The area of ​​the electrically conductive side face 131, 141, 151, 161 may be between 0% and 100% of the area of ​​the side faces 130, 140, 150, 160. The electrically conductive end face coating 111, 121 and the electrically conductive side face coating 131, 141, 151, 161 may be manufactured by thermal lamination of a metal film or by metal vapor deposition. The metal may be copper, copper alloys, gold, gold alloys, aluminum, aluminum alloys, silver, silver alloys, etc. The conductive end surface coatings 111, 121 and the conductive side surface coatings 131, 141, 151, 161 preferably have a thickness of less than 0.1 mm.

[0049] Therefore, instead of true electrodes, the acceleration transducer 1 only comprises conductive end coatings 111, 121 and conductive side surface coatings 131, 141, 151, 161. The acceleration transducer 1 therefore contains fewer elements, which saves space and makes the assembly of the acceleration transducer 1 easier.

[0050] Thanks to the conductive end coatings 111, 121 and the conductive side surface coatings 131, 141, 151, 161, no mechanical preloading of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' is necessary, because the conductive end coatings 111, 121 and the conductive side surface coatings 131, 141, 151, 161 are in material contact with the end faces 110, 120 and the side faces 130, 140, 150, 160 and seal the pores in the end faces 110, 120 and the side faces 130, 140, 150, 160. Sealing the pores in this way makes it unnecessary to provide the acceleration transducer 1 with separate preloading means, such as a preloading sleeve according to CH399021A1 or a preloading housing according to RU1792537C1. This reduces the number of components, thereby saving space and weight, and facilitating assembly of the acceleration transducer 1.

[0051] 7 and 8, according to a first embodiment of the first piezoelectric element 10, the second piezoelectric element 10' or the third piezoelectric element 10'', the first end face 110 comprises, on a portion of its area, two end face coatings 111, 111' having a first conductivity and two first uncoated end face areas 112, 112' on a portion of its area. Furthermore, the second end face 120 comprises, on a portion of its area, end face coatings 121, 121', 121'' having three or more conductivity types. The first lateral surface 130 comprises, on a portion of its area, a lateral surface coating 131 having a first conductivity type, a lateral surface coating 133 having another first conductivity type on a portion of its area, and a plurality of uncoated first lateral surface areas 132, 132', 132'', 132''', 132'''', 132'''' on a portion of its area. The second lateral surface 140 comprises, on a portion of its area, a lateral surface coating 141 having a second electrical conductivity and, on a portion of its area, a second uncoated lateral surface area 142. The third lateral surface 150 comprises, on a portion of its area, a lateral surface coating 151 having a third electrical conductivity and, on a portion of its area, two third uncoated lateral surface areas 152, 152'. The fourth lateral surface 160 comprises, on a portion of its area, a lateral surface coating 161 having a fourth electrical conductivity.

[0052] According to a first embodiment of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', shown in Figures 7 and 8, two end surface coatings 111, 111' having a first conductivity, another side surface coating 133 having a first conductivity and a side surface coating 151 having a third conductivity form a continuous coating 101 having a first conductivity. A plurality of end surface coatings 121, 121', 121'' having a second conductivity, a side surface coating 131 having a first conductivity, a side surface coating 141 having a second conductivity and a side surface coating 161 having a fourth conductivity form a continuous coating 102 having a second conductivity.

[0053] In the present invention, the adjective "continuous" has the meaning of "conductively connected". A continuous coating 101 having a first conductivity receives a first piezoelectric charge generated on the surfaces of the first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' below the continuous coating 101 having the first conductivity as a first acceleration signal S1. A continuous coating 102 having a second conductivity receives a second piezoelectric charge generated on the surfaces of the first piezoelectric element 10, the second piezoelectric element 10', and the third piezoelectric element 10'' below the continuous coating 102 having the second conductivity as a second acceleration signal S2. The first and second piezoelectric charges have different signals. Thus, the first piezoelectric charge has a negative signal and the second piezoelectric charge has a positive signal, or the first piezoelectric charge has a positive signal and the second piezoelectric charge has a negative signal.

[0054] Preferably, the end surface coating 111 having the first conductivity and the side surface coating 131 having the first conductivity form a continuous coating 101 having the first conductivity. Preferably, the end surface coating 121 having the second conductivity and the further side surface coating 133 having the first conductivity form a continuous coating 102 having the second conductivity. Preferably, at least one of the side surface coating 141 having the second conductivity, the side surface coating 151 having the third conductivity or the side surface coating 161 having the fourth conductivity is part of the continuous coating 101 having the first conductivity or is part of the continuous coating 102 having the second conductivity.

[0055] As shown in Figures 7 and 8, according to a first embodiment of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', the continuous coating 101 having a first electrical conductivity and the continuous coating 102 having a second electrical conductivity are electrically insulated from each other by two first uncoated end surface areas 112, 112', a plurality of first uncoated lateral surface areas 132, 132', 132'', 132''', a second uncoated lateral surface area 142 and two third uncoated lateral surface areas 152, 152'.

[0056] As shown in Figs. 9 and 10, according to a second embodiment of the first, second and third piezoelectric elements 10, 10' and 10'', the first end face 110 comprises an end face coating 111 having a first conductivity on a portion of its area and a plurality of first uncoated end face areas 112, 112', 112'' on a portion of its area. Furthermore, the second end face 120 comprises a plurality of end face coatings 121, 121'', 121'' having a second conductivity on a portion of its area and a second uncoated end face area 122 on a portion of its area. The first lateral surface 130 comprises a lateral surface coating 131 having a first conductivity on a portion of its area, two additional lateral surface coatings 133, 133' having a first conductivity on a portion of its area and a plurality of first uncoated lateral surface areas 132, 132', 132'' on a portion of its area. The second lateral surface 140 comprises, on a portion of its area, a lateral surface coating 141 having a second electrical conductivity and a plurality of second uncoated lateral surface areas 142, 142', 142'' on a portion of its area. The third lateral surface 150 comprises, on a portion of its area, a lateral surface coating 151 having a third electrical conductivity and a plurality of third uncoated lateral surface areas 152, 152' on a portion of its area. The fourth lateral surface 160 comprises, on a portion of its area, a lateral surface coating 161 having a fourth electrical conductivity.

[0057] As shown in Figures 9 and 10, according to the second embodiment of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', the plurality of end surface coatings 112, 112', 112'' having a first conductivity and two second side surface coatings 131, 131' having a first conductivity form a continuous coating 101 having a first conductivity. The plurality of end surface coatings 121, 121', 121'', two additional side surface coatings 133, 133' having a first conductivity, a side surface coating 141 having a second conductivity, a side surface coating 151 having a third conductivity and a side surface coating 161 having a fourth conductivity form a continuous coating 102 having a second conductivity.

[0058] As shown in Figures 9 and 10, according to the second embodiment of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', the conductive side surface coatings 131, 131' of the continuous coating 101 having the first conductivity extract piezoelectric interference charges for normal forces along the normal axis a, which have a polarity opposite to that of the piezoelectric interference charges extracted by the end surface coating 111 having the first conductivity of the continuous coating 101 having the first conductivity for shear forces along the sub-tangential axis n. In addition, the conductive side surface coatings 133, 141, 151, 161 of the continuous coating 102 having the second conductivity extract piezoelectric interference charges due to normal forces acting along the normal axis a, which have a polarity opposite to the polarity of the piezoelectric interference charges extracted by the end surface coatings 121, 121'', 121''' of the continuous coating 102 having the second conductivity due to shear forces acting along the sub-tangential axis n.

[0059] As shown in Figures 9 and 10, according to the second embodiment of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', the coating having the first conductivity 101 and the coating having the second conductivity 102 are electrically insulated from each other by a plurality of first uncoated end surface areas 112, 112', 112'', a second uncoated end surface area 122, a plurality of first uncoated lateral surface areas 132, 132', 132'', a plurality of second uncoated lateral surface areas 142, 142', 142'', and a third uncoated lateral surface area 152.

[0060] The ratio of the size of the coating 131 having a first conductivity to the size of the coating 133 having another first conductivity may be adjusted by the relative positions and / or sizes of the first uncovered lateral surface areas 132, 132', 132'', 132''', 132'''' of the first lateral surface 130. In the context of the present invention, the conjunction "and / or" means that only one of these conjunctions or both of these conjunctions apply.

[0061] The ratio of the size of the coating having the first conductivity 131 to the size of the coating having the further first conductivity 133 can be adjusted by the relative position of the first uncoated lateral surface area 132, 132′, 132″, 132′″, 132″″ of the first lateral surface 130 with respect to the second lateral surface 140 and the third lateral surface 150. Depending on the relative position of the first uncoated lateral surface area 132, 132′, 132″, 132′″, 132″″ of the first lateral surface 130 being moved further towards the second lateral surface 140 or further towards the third lateral surface 150, the ratio of the size of the coating having the first conductivity 131 to the size of the further first conductive coating 133 can be correspondingly decreased or increased. According to a first embodiment of the first thick element 10, second piezoelectric element 10', third piezoelectric element 10'', shown in Figures 7 and 8, the first uncoated lateral surface 132, 132', 132''', 132'''' is located relatively close to the second lateral surface 140. According to a second embodiment of the first thick element 10, second piezoelectric element 10', third piezoelectric element 10'', shown in Figures 9 and 10, the first uncoated lateral surface area 132, 132', 132'' is located at a substantially equal distance from the second lateral surface 140 and the third lateral surface 150.

[0062] However, the ratio between the size of the coating having the first conductivity 131 and the size of the coating having the further first conductivity 133 can also be adjusted by increasing or decreasing the size of the first uncoated lateral surface area 132, 132', 132''', 132'''' of the first lateral surface 130. According to the first embodiment of the first thick element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', shown in Figures 7 and 8, the first uncoated lateral surface area 132, 132', 132'', 132''', 132'''' has substantially twice the size of the coating having the further first conductivity 133, and the first uncoated lateral surface area 132, 132', 132''', 132'''', 132'''' is substantially one fifth the size of the coating having the first conductivity 131. According to a second embodiment of the first thick element 10, the second piezoelectric element 10' and the third piezoelectric element 10'', shown in Figures 9 and 10, the first uncoated lateral surface area 132, 132', 132'' has a size substantially equal to the first conductive coating 131, 131' and the further first conductive coating 133.

[0063] Preferably, the conductive side surface coating of the first conductivity coating 101 extracts piezoelectric interference charges for normal forces along the normal axis a, which have a polarity opposite to that of the piezoelectric interference charges extracted by the first conductivity end coating of the first conductivity coating 101 for shear forces acting along the sub-tangential axis n. In addition, the conductive side surface coating of the second conductivity coating 102 extracts piezoelectric interference charges for normal forces along the normal axis a, which have a polarity opposite to that of the piezoelectric interference charges extracted by the second conductivity end coating of the second conductivity coating 102 for shear forces along the sub-tangential axis n.

[0064] Preferably, the size of the conductive side surface coating of the continuous coating 101 having the first conductivity is such that the number of piezoelectric interference charges extracted by the conductive side surface coating for shear forces along the normal axis a is substantially equal to the number of piezoelectric interference charges extracted by the end coating of the first conductivity of the continuous coating 101 for shear forces along the sub-tangential axis n. Furthermore, the conductive side surface coating of the continuous coating 102 having the second conductivity extracts a number of piezoelectric interference charges for normal forces along the normal axis a that is substantially equal to the number of piezoelectric interference charges extracted by the end coating of the second conductivity of the continuous coating 102 having the second conductivity for shear forces along the sub-tangential axis n.

[0065] In contrast to RU1792537C1, shear forces are detected according to the invention by only one piezoelectric element 10, 10', 10'' per axis. It is therefore not possible to eliminate the piezoelectric interference charges arising from the shear forces acting along the secondary tangential axis n, which distort the measurement of the shear forces along the main tangential axis h by connecting two piezoelectric elements with opposite polarity in series per axis. The acceleration transducer 1 of the invention therefore uses a different solution. It is based on the fact that the piezoelectric material also generates piezoelectric interference charges for normal forces acting on the lateral surfaces 130, 140, 150, 160 along the normal axis a. These piezoelectric interference charges also distort the detection of the shear forces along the main tangential axis h. For this reason, these piezoelectric interference charges are usually not extracted from the lateral surfaces 130, 140, 150, 160. However, it has been found that the generation of shear forces along the minor tangential axis n is accompanied by a normal force acting along the normal axis a. In the former case, piezoelectric interference charges are generated on the end faces 110, 120, while in the latter case, piezoelectric interference charges are generated on the lateral surfaces 130, 140, 150, 160. These two types of piezoelectric interference charges interfere with the detection of shear forces along the major tangential axis h. By using a suitable first conductive continuous coating 101 and a second conductive continuous coating 102, it is possible to electrically connect the end faces 110, 120 and the lateral surfaces 130, 140, 150, 160 in series and to eliminate the piezoelectric interference charges that interfere with the detection of shear forces along the major tangential axis h.

[0066] 11 is a schematic diagram of the piezoelectric charge transmission of the transducer unit 1.1. Parts of the first, second and third piezoelectric elements 10, 10' and 10'' with the first lateral surface 130, as well as a part of the transducer unit 1.3 and also a part of the signal output 1.4 are shown.

[0067] The converter unit 1.3 is able to convert the first acceleration signal S1. The converter unit 1.3 comprises at least a first piezoelectric element conductor 13.1, 13.1', 13.1'' and a second piezoelectric element conductor 13.2, 13.2', 13.2'', at least a first main body conductor 13.3, 13.3', 13.3'' and a second main body conductor 13.4, 13.4', 13.4'', at least one transimpedance converter 13.10, 13.10', 13.10'', and at least a first signal output conductor 13.8, 13.8', 13.8'' and a second signal output conductor 13.9. Furthermore, the converter unit 1.3 comprises at least one first electrical resistor 13.5, 13.5', 13.5'' and / or at least one second electrical resistor 13.6, 13.6', 13.6''.

[0068] In a first embodiment of the acceleration transducer 1, shown in figures 1 and 3, the converter unit 1.3 is arranged directly only on the main body 12. Preferably, the converter unit 1.3 is arranged directly only on the first vertical side 12.7 of the main body 12. In a second embodiment of the acceleration transducer 1, shown in figures 2 and 4, the converter unit 1.3 is arranged directly only on the support 13.7. The support 13.7 is made of an electrically insulating material, such as Al2O3, ceramic, Al2O3 ceramic, fibre-reinforced plastic, etc. The support 13.7 is fixed to the main body 12. Preferably, the support 13.7 is attached to the first vertical side 12.7 of the main body 12 by material bonding, such as gluing, soldering, etc.

[0069] The first piezoelectric element conductor 13.1, 13.1', 13.1'' and the second piezoelectric element conductor 13.2, 13.2', 13.2'', the first main body conductor 13.3, 13.3', 13.3'' and the second main body conductor 13.4, 13.4', 13.4'', the first electrical resistor 13.5, 13.5', 13.5'', the second electrical resistor 13.6, 13.6', 13.6'' and the transimpedance converter 13.10, 13.10', 13.10'' are attached to the first vertical side 12.7 (first embodiment of the acceleration transducer 1 according to Figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to Figures 2 and 4).

[0070] The first piezoelectric element conductors 13.1, 13.1', 13.1'' and second piezoelectric element conductors 13.2, 13.2', 13.2'', the first main body conductors 13.3, 13.3', 13.3'' and second main body conductors 13.4, 13.4', 13.4'', as well as the first signal output conductors 13.8, 13.8', 13.8'' and second signal output conductors 13.9 are made of a conductive material, such as copper, copper alloy, gold, gold alloy, aluminum, aluminum alloy, etc., have a diameter of 0.02 mm to 0.10 mm, and are mechanically flexible.

[0071] The first piezoelectric element conductor 13.1, 13.1', 13.1'' and the second piezoelectric element conductor 13.2, 13.2', 13.2'', the first main body conductor 13.3, 13.3', 13.3'' and the second main body conductor 13.4, 13.4', 13.4'', as well as the first signal output conductor 13.8, 13.8', 13.8'' and the second signal output conductor 13.9 conduct the first and second acceleration signals S1, S2 in an electrically isolated manner from the ground. In the context of the present invention, the term "insulated from earth" means electrical isolation of the acceleration transducer 1 from the ground. Preferably, the housing 1.2 of the acceleration transducer 1 is earthed, so that the housing 1.2 has a potential equal to the local earth. The acceleration signals S1, S2 are therefore conducted in an electrically isolated manner from the potential of the acceleration transducer 1. In this way, the acceleration measurement is not distorted by changes in the potential of the acceleration transducer 1, for example between the housing 1.2 and the converter unit 1.3.

[0072] Preferably, the first main body conductor 13.3, 13.3', 13.3'' and the second main body conductor 13.4, 13.4', 13.4'' are patterned in a conductive coating. The conductive coating is formed by chemical vapor deposition, physical vapor deposition, etc. The conductive coating is made of a conductive material, such as copper, copper alloys, gold, gold alloys, platinum, platinum alloys, etc. The conductive coating is a conductive thin film. In the context of the present invention, the term "thin film" means that the thickness of the conductive coating in a direction perpendicular to its planar extension is preferably less than 0.1 mm. The conductive coating is applied directly to the first vertical side 12.7 (first embodiment of the acceleration transducer 1 according to figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to figures 2 and 4). In the context of the present invention, the adverb "directly" means "directly". Preferably, the patterning of the first main body conductor 13.3, 13.3', 13.3'' and the second main body conductor 13.4, 13.4', 13.4'' in the conductive coating is performed by stencil printing, photolithography and laser cutting.

[0073] Preferably, the converter unit 1.3 comprises three first piezoelectric element conductors 13.1, 13.1', 13.1'' and two second piezoelectric element conductors 13.2, 13.2', 13.2''. One first piezoelectric element conductor 13.1, 13.1', 13.1'' transmits a first acceleration signal S1 from the first conductive coating 101 of the first piezoelectric element 10, the second piezoelectric element 10' or the third piezoelectric element 10'', respectively, to the converter unit 1.3. One second piezoelectric element conductor 13.2, 13.2', 13.2'' transmits a second acceleration signal S2 from the second conductive coating 102 of the first piezoelectric element 10, the second piezoelectric element 10' or the third piezoelectric element 10'', respectively, to the converter unit 1.3.

[0074] The first piezoelectric element conductors 13.1, 13.1', 13.1'' and the second piezoelectric element conductors 13.2, 13.2', 13.2'' are in contact with the first lateral surface 130. This is because the first lateral surface 130 is available and serves a specific technical role, namely, that it has piezoelectric element contacts 13.01, 13.01', 13.01'' provided thereon for transmitting the piezoelectric charge, thereby saving space. Each of the first piezoelectric element conductors 13.1, 13.1', 13.1'' contacts the first lateral surface electrical coating 131 via the first piezoelectric element contacts 13.01, 13.01', 13.01''. Each of the second piezoelectric element conductors 13.2, 13.2', 13.2'' contacts the second side surface electrical coating 133 via a second piezoelectric element contact 13.02, 13.02', 13.02''. The first piezoelectric element contacts 13.01, 13.01', 13.01'' and the second piezoelectric element conductors 13.2, 13.2', 13.2'' are attached to the first side surface 130. The first piezoelectric element contacts 13.01, 13.01', 13.01'' and the second piezoelectric element conductors 13.2, 13.2', 13.2'' are material bonds made by wire bonding, soldering, or the like. Methods such as thermocompression, thermosonic ball wedge bonding, ultrasonic wedge bonding, and the like are suitable for wire bonding. The circular first piezoelectric element contacts 13.01, 13.01', 13.01'' and second piezoelectric element contacts 13.02, 13.02', 13.02'' in FIG. 11 represent formed wires.

[0075] The converter unit 1.3 preferably comprises three first main body conductors 13.3, 13.3', 13.3'' and two second main body conductors 13.4, 13.4', 13.4''. Each of the first piezoelectric element conductors 13.1, 13.1', 13.1'' contacts the first main body conductor 13.3, 13.3', 13.3'' via a first main body access contact 13.03, 13.03', 13.03''. One second piezoelectric element conductor 13.2, 13.2', 13.2'' contacts the second main body conductor 13.4, 13.4', 13.4'' via a second main body access contact 13.04, 13.04', 13.04'' respectively. The first main body access contact 13.03, 13.03', 13.03'', and the second main body access contact 13.04, 13.04', 13.04'' are attached to the first vertical side surface 12.7 (first embodiment of the acceleration transducer 1 according to figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to figures 2 and 4). The first main body access contact 13.03, 13.03, 13.03'' and the second main body access contact 13.04, 13.04', 13.04'' are material bonds made by wire bonding, soldering, etc. Methods such as thermocompression, thermosonic ball wedge bonding, ultrasonic wedge bonding, etc. are suitable for wire bonding. The circular first main body access contacts 13.03, 13.03', 13.03'' and second main body access contacts 13.04, 13.04', 13.04'' of FIG. 11 represent wire formed contacts.

[0076] The first electrical resistor 13.5, 13.5', 13.5'', the second electrical resistor 13.6, 13.6', 13.6'' and the transimpedance converter 13.10, 13.10', 13.10'' are electrically connected to each other by the first main body conductor 13.3, 13.3', 13.3''. The second main body conductor 13.4, 13.4', 13.4'' carrying the second acceleration signal S2 of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' is electrically shorted and serves as the reference potential of the converter unit 1.3. The reference potential is a stabilized, i.e. temporarily constant, direct electrical voltage.

[0077] Preferably, the converter unit 1.3 comprises three transimpedance converters 13.10, 13.10', 13.10''. The three transimpedance converters 13.10, 13.10', 13.10'' have an identical structure. In the embodiment according to figures 1 and 2, the transimpedance converters 13.10, 13.10', 13.10'' are electronic components. The transimpedance converter 13.10, 13.10', 13.10'' is fixed to the first vertical side surface 12.7 (first embodiment of the acceleration transducer 1 according to figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to figures 2 and 4) by a material bond via an interposer and / or the transimpedance converter 13.10, 13.10', 13.10'' is fixed to the first main body conductor 13.3, 13.3, 13.3'' and to the second main body conductor 13.4, 13.4', 13.4'' via an interposer. The interposer is a chemically curable adhesive, a physically hardening adhesive, a solder, etc. Preferably, the interposer is an adhesive, such as epoxy, polyurethane, cyanoacrylate, methyl methacrylate, etc. One first main body conductor 13.3, 13.3', 13.3'' contacts each of the transimpedance converters 13, 10, 13.10', 13.10''. Any contacting method may be selected. One first main body conductor 13.3, 13.3', 13.3'' transmits the first acceleration signal S1 to the input of the transimpedance converter 13.10, 13.10', 13.10''. Preferably, the input of the transimpedance converter 13.10, 13.10', 13.10' is connected to the input of the transimpedance converter 13.10, 13.10', 13.10''. 7 The transimpedance converter 13.10, 13.10', 13.10'' converts the first acceleration signal S1 into a voltage. The converted first acceleration signal S1 is provided at the output of the transimpedance converter 13.10, 13.10', 13.10''. Preferably, the output of the transimpedance converter 13.10, 13.10', 13.10' has a high impedance of more than 10 2However, instead of using a transimpedance converter, a person skilled in the art aware of the present invention may also use a charge amplifier having a low electrical resistance at the input of the charge amplifier.

[0078] FIG. 12 shows a schematic diagram of the high-pass filters 18, 18', 18'' of the converter unit 1.3. Preferably, the converter unit 1.3 comprises three first electrical resistors 13.5, 13.5', 13.5''. The three first electrical resistors 13.5, 13.5', 13.5'' are identical in structure.

[0079] In the embodiment according to figures 1 and 2, the first electrical resistor 13.5, 13.5', 13.5'' is a resistive coating made of a resistive material, such as Al2O3, ceramic, Al2O3 ceramic, etc. The resistive coating is produced by chemical vapor deposition, physical vapor deposition, etc. The resistive coating is a thin film of an electrical resistor. The resistive coating is also a "thin film" in the sense of the present invention, since its thickness in the direction perpendicular to its planar extension is preferably less than 0.1 mm. The resistive coating is applied directly to the first vertical side surface 12.7 (first embodiment of the acceleration transducer 1 according to figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to figures 2 and 4) and / or the resistive coating is applied directly to the first main body conductor 13.3, 13.3', 13.3'' and the second main body conductor 13.4, 13.4', 13.4''. The resistive coating may be patterned by stencil printing, photolithography, laser cutting, and the like.

[0080] In the embodiment according to figures 2 and 4, the first electrical resistor 13.5, 13.5', 13.5'' is an electrical component made of a resistive material such as ceramic, metal oxide etc. and a connecting wire.

[0081] The first main body conductor 13.3, 13.3', 13.3'' contacts the first electrical resistor 13.5, 13.5', 13.5'', respectively. Any contacting method may be selected. The first electrical resistor 13.5, 13.5', 13.5'' is electrically connected in parallel to one of the three piezoelectric elements 10, 10', 10'', respectively. This parallel connection is a high pass filter 18, 18', 18''', because the first piezoelectric element 10, the second piezoelectric element 10' or the third piezoelectric element 10'' is a capacitor. The high pass filter 18, 18', 18'' removes frequencies below a cutoff frequency. The cutoff frequency is preferably 10 Hz. When the measurement of acceleration by the acceleration transducer 1 is started, the discharge of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' can generate a low interference frequency that is below the cut-off frequency. This low interference frequency is present at the input of the transimpedance converter 13.10, 13.10', 13.10'' and represents an indefinite time constant. The low interference frequency can distort the measurement of acceleration. The low interference frequency is removed and the transimpedance converter 13.10, 13.10', 13.10'' obtains a definite time constant. The cut-off frequency can be adjusted depending on the value of the electrical resistance of the first electrical resistor 13.5, 13.5', 13.5''.

[0082] FIG. 13 shows a schematic diagram of the low-pass filters 17, 17', 17'' of the converter unit 1.3. Preferably, the converter unit 1.3 comprises three second electrical resistors 13.6, 13.6', 13.6''. The three second electrical resistors 13.6, 13.6', 13.6'' have the same structure. The second electrical resistors 13.6, 13.6', 13.6'' are electrical components made of resistive materials such as ceramics, metal oxides, etc., and connecting wires. The first main body conductors 13.3, 13.3', 13.3'' contact the second electrical resistors 13.6, 13.6', 13.6'', respectively. Any contacting method may be selected. The second electrical resistors 13.6, 13.6', 13.6'' are each electrically connected in series with one of the three piezoelectric elements 10, 10', 10''. This series connection is a low pass filter 17, 17', 17'', because the first piezoelectric element 10, the second piezoelectric element 10' or the third piezoelectric element 10'' is a capacitor. The low pass filter 17, 17', 17'' removes high interference frequencies below the natural frequency of the acceleration transducer 1. Such highly interfering frequencies are generated by the mechanical excitation of the acceleration transducer 1. Highly interfering frequencies are present at the input of the transimpedance converter 13.10, 13.10', 13.10'' and can saturate the transimpedance converter 13.10, 13.10', 13.10'' and thus distort the acceleration measurement. The low-pass filter 17, 17', 17'' can be adjusted to the natural frequency of the acceleration transducer 1 depending on the value of the electrical resistance of the second electrical resistor 13.6, 13.6, 13.6''.

[0083] Preferably, the converter unit 1.3 comprises three first main body output conductors 13.8, 13.8', 13.8''. Each output of the transimpedance converter 13.10, 13.10', 13.10'' contacts a first main body output contact 13.08, 13.08', 13.08'' via a first main body conductor 13.3, 13.3', 13.3''. Preferably, the converter unit 1.3 comprises a second main body output conductor 13.9. The second main body conductor 13.4, 13.4', 13.4'' contacts the second main body output conductor 13.9 via a second main body output contact 13.09. The first main body output contact 13.08, 13.08', 13.08'' and the second main body output contact 13.09 are fixed to the first vertical side surface 12.7 (first embodiment of the acceleration transducer 1 according to figures 1 and 3) or to the support 13.7 (second embodiment of the acceleration transducer 1 according to figures 2 and 4). The first main body output contact 13.08, 13.08', 13.08'' and the second main body output contact 13.09 are material bonds made by wire bonding, soldering, etc. Methods such as thermocompression, ultrasonic heat ball wedge bonding, ultrasonic wedge bonding, etc. are suitable for wire bonding. The circular first main body output contact 13.08, 13.08', 13.08'' and the second main body output contact 13.09 in figure 11 represent wire formed.

[0084] The first main body output conductor 13.8, 13.8', 13.8'' carries the converted first acceleration signal S1 to the signal output 1.4. The second main body output conductor 13.9 carries the sum of the second acceleration signal S2 to the signal output 1.4.

[0085] The signal output 1.4 is fixed to the housing 1.2 at a portion of its area. According to the embodiment of the acceleration transducer 1 shown in Figures 1 and 2, the signal output 1.4 is preferably an electric cable. The signal output 1.4 comprises signal lines 14.1, 14.1', 14.1'', 14.2, a protective sheath 14.3, a sheath flange 14.4, an electrical insulator 14.5 and a casting material 14.6.

[0086] In cross section, the signal output section 1.4 has a multi-layer structure.

[0087] The signal lines 14.1, 14.1, 14.1'', 14.2 form an inner layer. Preferably, the signal output 1.4 comprises three first signal lines 14.1, 14.1', 14.1'', and one second signal line 14.2. The signal lines 14.1, 14.1, 14.1'', 14.2 are made of an electrically conductive material, such as copper, copper alloy, gold, gold alloy, aluminium, aluminium alloy, etc. Preferably, each signal line 14.1, 14.1', 14.1'', 14.2 comprises an electrically insulating sheath. The first main body output conductor 13.8, 13.8', 13.8'', and the second main body output conductor 13.9 contact the first signal line 14.1, 14.1', 14.1'', and the second signal line 14.2. Each of the first main body output conductors 13.8, 13.8', 13.8'' contacts a respective first signal conductor 14.1, 14.1, 14.1''. The second main body output conductor 13.9 contacts the second signal conductor 14.2.

[0088] An electrical insulator 14.5 forms an intermediate layer and is disposed around the signal wires 14.1, 14.1', 14.1'', 14.2. The electrical insulator 14.5 electrically insulates the signal wires 14.1, 14.1', 14.1'', 14.2 from the protective sheath 14.3. The electrical insulator 14.5 is made of an electrically insulating material such as Al2O3, ceramic, Al2O3 ceramic, fiber reinforced plastic, etc.

[0089] A protective sheath 14.3 forms the outer layer. It protects the electrical insulator 14.5 and also the signal lines 14.1, 14.1', 14.1'', 14.2 from harmful environmental influences such as contamination (dust, moisture, etc.) and also from electromagnetic waves that may produce undesirable interfering effects on the first acceleration signal S1 and the second acceleration signal S2. The protective sheath 14.3 is made of a mechanically resistant material such as metal, plastic, etc.

[0090] 14 to 18 show the steps of assembling an embodiment of the acceleration transducer 1 according to FIG.

[0091] FIG. 14 shows the first step of assembly, in which the signal lines 14.1, 14.1', 14.1'', 14.2 are introduced into the housing 1.2. The housing 1.2 comprises a signal output opening 1.22. The signal output opening 1.22 preferably has the shape of the protective sheath 14.3 and the dimensions of the outer diameter of the protective sheath 14.3. The ends of the signal lines 14.1, 14.1', 14.1'', 14.2 are bare, whereas here the electrically insulating sheath has been removed in some areas. The ends of the signal lines 14.1, 14.1', 14.1'', 14.2 protrude through the signal output opening 1.22 into the inner space of the housing 1.2. The inner space of the housing 1.2 is the space around the housing bottom 1.23.

[0092] The signal output opening 1.22 is sealed from the outside by a protective sheath 14.3 and a sheath flange 14.3. Preferably, one end of the protective sheath 14.3 is attached to a sheath flange 14.4. The sheath flange 14.4 is made of a mechanically resistant material, such as metal, plastic, etc. The connection of the protective sheath 14.3 and the sheath flange 14.4 is achieved by a force connection, such as crimping.

[0093] The metal flange 14.4 itself is fastened to the housing 1.2 by a material joint. Preferably, the metal flange 14.4 is fastened to the outer edge of the housing opening 1.22 facing away from the interior of the housing 1.2. The material joint is made by welding, soldering, gluing, etc. The connection between the sheath flange 14.4 and the housing 1.2 provides a strain relief for the protective sheath 14.3. Such strain relief of the protective sheath 14.3 ensures that mechanical loads are not transferred from the protective sheath 14.3 to the interior of the housing 1.2. Mechanical loads that reach the converter unit 1.3 could cause damage, such as tearing or bursting, of the main body output conductors 13.8, 13.8,', 13.8'', 13.9. Such mechanical stresses arise due to twisting, twisting, etc. of the protective sheath 14.3 about its extension along its longitudinal axis.

[0094] FIG. 15 shows the second step of assembly, where the signal lines 14.1, 14.1', 14.1'', 14.2 are fixed in shape within the housing 1.2 using a casting material 14.6. The casting material 14.6 is applied through the housing opening 1.20 to the signal lines 14.1, 14.1', 14.1'' within the signal output opening 1.21. The casting material 14.6 is a chemically curable adhesive or a physically hardenable adhesive, or a combination of a chemically curable adhesive and a physically hardenable adhesive. Preferably, the casting material 14.6 is comprised of an adhesive such as epoxy, polyurethane, cyanoacrylate, methyl methacrylate, etc. The casting material 14.6 is applied to the signal lines 14.1, 14.1', 14.1'' within the signal output opening 1.21. 12 Ωmm 2 / m. Preferably, sufficient casting material 14.6 is applied to the signal lines 14.1, 14.1', 14.1'', 14.2 within the signal output opening 1.21 to completely seal the signal output opening 1.21.

[0095] FIG. 16 shows a third step of assembly, where the signal lines 14.1, 14.1', 14.1'', 14.2, which are fixed in shape in the casting material 14.6, are exposed in some areas in the housing 1.2. The exposed portions 14.7 of the signal lines 14.1, 14.1', 14.1'', 14.2 are obtained by a suitable cutting tool, such as a cutting wedge, a milling cutter, etc. The cutting tool is introduced into the interior of the housing 1.2 through the housing opening 1.20 and cuts off the ends of the signal lines 14.1, 14.1', 14.1'', 14.2 as well as a part of the hardened casting material 14.6. The exposed portions 14.7 lie in a plane defined by the transverse axis x and the longitudinal axis y. In this area of ​​the exposed portion 14.7, the end faces of the cut ends of the signal lines 14.1, 14.1', 14.1'', 14.2 are exposed in a plane. Preferably, this plane is parallel to the housing opening 1.20. In this area of ​​the exposed portion 14.7, the lateral surfaces of the signal lines 14.1, 14.1', 14.1'', 14.2 are completely covered by the casting material 14.6. The casting material 14.6 fixes the signal lines 14.1, 14.1', 14.1'', 14.2 in a strain-relieving manner. This strain-relief of the signal lines 14.1, 14.1', 14.1'', 14.2 prevents mechanical loads from being transferred from the signal lines 14.1, 14.1', 14.1'', 14.2 to the inside of the housing 1.2. Mechanical loads reaching the converter unit 1.3 can cause damage such as tearing or bursting of the main body output conductors 13.8, 13.8', 13.8'', 13.9. Such mechanical stresses can occur due to twisting or torsion of the signal lines 14.1, 14.1', 14.1'', 14.2 around their extension along their longitudinal axis. Furthermore, the casting material 14.6 hermetically seals the signal output opening 1.21. The hermetic seal of the signal output opening 1.21 prevents moisture from entering the interior of the housing 1.2 via the signal lines 14,1, 14.1', 14.1'', 14.2 and reaching the converter unit 1.1. Piezoelectric materials such as quartz are very hygroscopic, so moisture can impair the functionality of the piezoelectric elements 10, 10', 10''.

[0096] Fig. 17 shows the fourth step of assembly, where the converter unit 1.1 is introduced into the housing 1.2. The converter unit 1.1 together with the converter unit 1.3 is introduced into the interior of the housing 1.2 through the housing opening 1.20. The second vertical side 12.6 is fixed to the housing bottom 1.23 by a material bond, such as gluing, soldering, etc. Preferably, the converter unit 1.1 is positioned with the four tangential sides 12.4 adjacent to the exposed portion 14.7.

[0097] Fig. 18 shows the fifth step of assembly, in which the converter unit 1.3 of the converter unit 1.1 is contacted. The contacting of the converter unit 1.3 is performed by a suitable contacting tool, such as a wire bonder. The contacting tool is introduced into the interior of the housing 1.2 through the housing opening 1.20. The contacting tool connects the first main body conductors 13.3, 13.3', 13.3'' and the second main body conductors 13.4, 13.4', 13.4'' of the converter unit 1.3 to the first lateral surface 130 of the first piezoelectric element 10, the second piezoelectric element 10' and the third piezoelectric element 10'' via the first piezoelectric element conductors 13.1, 13.1', 13.1'' and the second piezoelectric element conductors 13.2, 13.2', 13.2''. In addition, a contact tool connects the first main body conductors 13.3, 13.3', 13.3'' and the second main body conductors 13.4, 13.4', 13.4'' of the converter unit 1.3 via the first main body output conductors 13.8, 13.8', 13.8'' and the second main body output conductor 13.9 to the signal lines 14.1, 14.1', 14.1'', 14.2 of the signal output 1.4.

[0098] Preferably, the first main body output conductor 13.8, 13.8', 13.8'' and the second main body output conductor 13.9 are directly connected to the end faces of the cut ends of the signal lines 14.1, 14.1', 14.1'', 14.2. This direct contact of the first main body output conductor 13.8, 13.8', 13.8'' and the second main body output conductor 13.9 to the signal lines 14.1, 14.1', 14.1'', 14.2 has the advantage that no separate support means such as a printed circuit board is required, which keeps the size and weight of the acceleration transducer low and makes the assembly of the acceleration transducer simple and cheap. This direct contact of the first 13.8, 13.8', 13.8'', and second 13.9 main body output conductors with the signal lines 14.1, 14.1', 14.1'', 14.2 has the additional advantage that the mechanically flexible main body output conductors 13.8, 13.8', 13.8'', 13.9 connect the converter unit 1.3 to the signal lines 14.1, 14.1', 14.1'', 14.2 in a strain-relieved manner, i.e. the mechanically flexible main body output conductors 13.8, 13.8', 13.8'', 13.9 attenuate the mechanical stresses that are transmitted to the signal lines 14.1, 14.1', 14.1'', 14.2.

[0099] Once the electrical contacting of the converter unit 1.3 is complete, the housing opening 1.20 is hermetically sealed by the housing cover 1.21. This seal is made by material bonding, such as welding, soldering or gluing. [Explanation of symbols]

[0100] 1 Acceleration transducer 1.1 Converter unit 1.2 Housing 1.20 Housing opening 1.21 Housing cover 1.22 Signal output opening 1.23 Housing bottom 1.24 Assembly Gap 1.3 Converter Unit 1.4 Signal Output Section 10, 10', 10'' Piezoelectric Elements 11, 11', 11'' vibrating mass 12 Main Body 12.1, 12.2, 12.3, 12.4 Tangential side 12.6, 12.7 Vertical side 13.01, 13.01', 13.01'' First Piezoelectric Element Contact 13.02, 13.02', 13.02'' Second Piezoelectric Element Contact 13.03, 13.03', 13.03'' 1st main body access contact 13.04, 13.04', 13.04'' Second main body access contact 13.08, 13.08', 13.08'' 1st main body output contact 13.09 Second main body output contact 13.1, 13.1', 13.1'' First piezoelectric element conductor 13.2, 13.2', 13.2'' Second piezoelectric element conductor 13.3, 13.3', 13.3'' 1st main body conductor 13.4, 13.4', 13.4'' Second Main Body Conductor 13.5, 13.5', 13.5'' First Electrical Resistor 13.6, 13.6', 13.6'' Second Electrical Resistor 13.7 Support 13.8, 13.8', 13.8'' 1st main body output conductor 13.9 Second main body output conductor 13.10, 13.10', 13.10'' Transimpedance Converter 14.1, 14.1', 14.1'' First signal line 14.2 Second Signal Line 14.3 Protective sheath 14.4 Sheath flange 14.5 Electrical Insulators 14.6 Casting materials 14.7 Exposed parts 15, 15', 15'' Inner Connection Means 16, 16', 16'' external connection means 17, 17', 17'' Low Pass Filter 18, 18', 18'' High Pass Filter 101 First conductive coating 102 Second conductive coating 110, 120 end face 111, 111' end surface coating having first conductivity 112, 112', 112'' first uncoated end area 121-121''' End face coating having second conductivity 122, 122', 122'' second uncoated end area 130, 140, 150, 160 lateral surface 131, 131' first conductive side surface coating 132, 132'-132'''' first uncoated lateral surface area 133, 133' another first conductive side surface coating 141 Second conductive side surface coating 142, 142', 142'' second uncoated lateral surface area 151, 151' Third conductive side surface coating 161 Fourth conductive side surface coating a Normal axis F force h Main tangential axis n Minor tangential axis S1, S2 acceleration signal x-axis y Longitudinal axis z vertical axis

Claims

1. An acceleration transducer (1) comprising at least one piezoelectric element (10, 10', 10''), at least one seismic mass (11, 11', 11'') and a main body (12), said acceleration transducer (1) being arranged in a Cartesian coordinate system having three axes (x, y, z), said three axes (x, y, z) including a transverse axis (x), a longitudinal axis (y) and a vertical axis (z); said main body (12) having tangential sides (12.1, 12.2, 12.3, 12.4) and vertical sides (12.6, 12.7), said tangential sides (12.1, 12.2, 12.3, 12.4) being arranged tangentially to said vertical axis (z) and said vertical sides (12.6, 12.7) being arranged perpendicularly to said vertical axis (z), At least one of said tangential sides (12.1, 12.2, 12.3) is fixed with exactly one piezoelectric element (10, 10', 10''); and exactly one seismic mass (11, 11', 11'') is fixed to said one piezoelectric element (10, 10', 10''), such that upon acceleration said exactly one seismic mass (11, 11', 11'') exerts on said piezoelectric element (10, 10', 10'') a shear force proportional to the acceleration, said shear force being along one of said three axes (x, y, z), which is the main tangential axis (h). said one piezoelectric element (10, 10', 10'') having end faces (110, 120), each end face (110, 120) lying in a plane defined by said main tangential axis (h) and a secondary tangential axis (n), said secondary tangential axis (n) lying in a plane perpendicular to said main tangential axis (h) and having a normal axis (a) perpendicular to said plane; under the effect of said shear force along said main tangential axis (h), said one piezoelectric element (10, 10', 10'') generates a piezoelectric electric field at said end face (110, 120); a seismic mass (11, 11', 11'') attached to said one piezoelectric element (10, 10', 10'') exerts, upon acceleration, a shear force along said sub-tangential axis (n) on said piezoelectric element (10, 10', 10'') proportional to the acceleration, said piezoelectric element (10, 10', 10'') generating a piezoelectric interference charge on said end face (110, 120) under the effect of said shear force along said sub-tangential axis (n); at least one end face (110, 120) having a conductive end face coating (111, 121); said conductive end face coating (111, 121) extracts piezoelectric charges generated by said shear forces along said major tangential axis (h); said conductive end face coating (111, 121) extracts piezoelectric interference charges generated by said shear forces along said minor tangential axis (n); said one piezoelectric element (10, 10', 10'') has lateral surfaces (130, 140, 150, 160) that are parallel to said normal axis (a);said seismic mass (11, 11', 11'') attached to said one piezoelectric element (10, 10', 10'') exerts, upon acceleration, a normal force along said normal axis (a) on said piezoelectric element (10, 10', 10'') proportional to the acceleration, said piezoelectric element (10, 10', 10'') generating piezoelectric interference charges on said lateral surfaces (130, 140, 150, 160) under the effect of said normal force along said normal axis (a); An acceleration transducer (1), characterized in that (10, 10', 10'') comprises at least one lateral surface (130, 140, 150, 160) which is provided in a partial area thereof with at least one electrically conductive lateral surface coating (131, 133, 141, 151, 161), said electrically conductive lateral surface coating (131, 133, 141, 151, 161) extracting piezoelectric interference charges generated by said normal force along said normal axis (a);

2. said one piezoelectric element (10, 10', 10'') having a high sensitivity for shear forces along said main tangential axis (h) exerted by said seismic mass (11, 11', 11'') attached to said piezoelectric element (10, 10', 10''); said one piezoelectric element (10, 10', 10'') has a low sensitivity to shear forces along said minor tangential axis (n) exerted by said seismic mass (11, 11', 11'') attached to said piezoelectric element (10, 10', 10''); 2. The acceleration transducer (1) according to claim 1, characterized in that the one piezoelectric element (10, 10', 10'') has a low sensitivity to normal forces along the normal axis (a) exerted by the seismic mass (11, 11', 11'') attached to the piezoelectric element (10, 10', 10'').

3. said one piezoelectric element (10) having a high sensitivity for shear forces along said longitudinal axis (y) which is said main tangential axis (h), a low sensitivity for shear forces along said perpendicular axis (z) which is said sub-tangential axis (n), and a low sensitivity for normal forces along said transverse axis (x) which is said normal axis (a); and / or said one piezoelectric element (10') has a high sensitivity for shear forces along said transverse axis (x) which is said main tangential axis (h), a low sensitivity for shear forces along said normal axis (z) which is said sub-tangential axis (n), and a low sensitivity for normal forces along said longitudinal axis (y) which is said normal axis (a); and / or 3. An acceleration transducer (1) according to claim 1 or 2, characterized in that the one piezoelectric element (10'') has a low sensitivity for shear forces along the vertical axis (z), which is the main tangential axis (h), a low sensitivity for shear forces along the longitudinal axis (y), which is the sub-tangential axis (n), and a low sensitivity for normal forces along the transverse axis (x), which is the normal axis (a).

4. 4. An acceleration transducer (1) according to claim 1, characterized in that one piezoelectric element (10, 10', 10'') with a high sensitivity for shear forces along the main tangential axis (h) generates at least five times more piezoelectric charge per unit force compared to a low sensitivity for shear forces along the secondary tangential axis (n) or a low sensitivity for normal forces along the normal axis (a).

5. 5. An acceleration transducer (1) according to claim 1, characterized in that for each of said piezoelectric elements (10, 10', 10''), the conductive end surface coatings (111, 121) and the conductive lateral surface coatings (131, 133, 141, 151, 161) form a conductive continuous coating (101, 102), and the extracted piezoelectric interference charges due to the shear forces along the sub-tangential axis (n) have a polarity opposite to that of the extracted piezoelectric interference charges due to the normal forces along the normal axis (a).

6. 6. An acceleration transducer (1) according to claim 5, characterized in that the size of the conductive lateral surface coatings (131, 133, 141, 151, 161) can be adjusted on each of the one piezoelectric elements (10, 10', 10'') such that the size of the conductive lateral surface coatings (131, 133, 141, 151, 161) extracts by the conductive continuous coating (101, 102) a number of piezoelectric interference charges substantially equal to the number of piezoelectric interference charges for the shear forces along the sub-tangential axis (n) and for the normal forces along the normal axis (a).

7. In said one piezoelectric element (10, 10', 10''), said lateral surfaces (130, 140, 150, 160) comprise a first lateral surface (130), said first lateral surface (130) being perpendicular to said sub-tangential axis (n) of said piezoelectric element (10, 10', 10''), said first lateral surface (130) comprising a first conductive lateral surface coating (131) and a further first conductive lateral surface coating (133), the size of said first conductive lateral surface coating (131) and the size of said further first conductive lateral surface coating (133) being determined by the thickness of said first conductive lateral surface coating (131).

7. An acceleration transducer (1) according to claim 5 or 6, characterized in that the ratio of the size of the first conductive lateral surface coating (131) to the size of the further first conductive lateral surface coating (133) can be adjusted such that the conductive continuous coatings (101, 102) extract a substantially equal number of piezoelectric interference charges due to the shear forces acting along the sub-tangential axis (n) and due to the normal forces acting along the normal axis (a).

8. The acceleration transducer (1) comprises a first piezoelectric element conductor (13.1, 13.1', 13.1'') and a second piezoelectric element conductor (13.2, 13.2', 13.2''), and in one of the piezoelectric elements (10, 10', 10''), the first electrically conductive lateral surface coating (131) is materially bonded to the first piezoelectric element conductor (13.1, 13.1', 13.1'') and in one of the piezoelectric elements (10, 10', 10''), the further first electrically conductive lateral surface coating (133) is materially bonded to the first piezoelectric element conductor (13.1, 13.1', 13.1'').

8. The acceleration transducer (1) according to claim 7, characterized in that the first piezoelectric element conductor (13.1, 13.1', 13.1'') is materially bonded to a second piezoelectric element conductor (13.2, 13.2', 13.2''), the first piezoelectric element conductor (13.1, 13.1', 13.1'') transmitting piezoelectric charges from the first conductive continuous coating (101) as a first acceleration signal (S1) and the second piezoelectric element conductor (13.2, 13.2', 13.2'') transmitting piezoelectric charges from the second conductive continuous coating (102) as a second acceleration signal (S2).

9. 9. The acceleration transducer (1) according to claim 1, characterized in that in one piezoelectric element (10, 10', 10''), the electrically conductive end surface coatings (111, 121) are intimately fitted to the end faces (110, 120) by material adhesion and seal pores in the end faces (110, 120) and the electrically conductive side surface coatings (131, 133, 141, 151, 161) are attached to the side surfaces (130, 140, 150, 160) by material adhesion and seal pores in the side surfaces (130, 140, 150, 160), and as a result of the sealing of the pores, the piezoelectric element (10, 10', 10'') does not require mechanical preloading.

10. In said one piezoelectric element (10, 10', 10''), said end faces (110, 120) comprise a first end face (110) and a second end face (120), said first end face (110) and said second end face (120) being arranged opposite to said normal axis (a) of said piezoelectric element (10, 10', 10''), said first end face (110) comprising a first conductive end face coating (111) and said second end face (120) comprising a second conductive end face coating (121), said lateral surfaces (130, 140, 150, 160) comprising a first lateral surface (130), said first lateral surface (130) being arranged opposite to said normal axis (a) of said piezoelectric element (10, 10', 10''), 10. The acceleration transducer (1) according to claim 1, characterized in that the first lateral surface (130) is perpendicular to the sub-tangential axis (n) of the axial direction (A) of the axial direction (A), the first lateral surface (130) comprises a first conductive lateral surface coating (131) and a further first conductive lateral surface coating (133), the first conductive end coating (111) and the first conductive lateral surface coating (131) form a first conductive continuous coating (101), and the second conductive end coating (121) and the further first conductive lateral surface coating (133) form a second conductive continuous coating (102).

11. In said one piezoelectric element (10, 10', 10''), said lateral surfaces (130, 140, 150, 160) comprise at least one second lateral surface (140) and at least one third lateral surface (150), said second lateral surface (140) and said third lateral surface (150) being perpendicular to said main tangential axis (h) of said piezoelectric element (10, 10', 10''), said second lateral surface (140) being a second conductive lateral surface 10. The acceleration transducer (1) according to claim 9 dependent on claim 8, characterized in that the third lateral surface (150) comprises a face coating (141), the third lateral surface (150) comprises a third conductive lateral surface coating (151), and the second conductive lateral surface coating (141) and the third conductive lateral surface coating (151) are part of the first conductive continuous coating (101) or part of the second conductive continuous coating (102).

12. In said one piezoelectric element (10, 10', 10''), said lateral surfaces (130, 140, 150, 160) comprise at least one second lateral surface (140) and at least one third lateral surface (150), said second lateral surface (140) and said third lateral surface (150) being perpendicular to said main tangential axis (h) of said piezoelectric element (10, 10', 10''), said second lateral surface (140) being a second conductive lateral surface 10. The acceleration transducer (1) according to claim 9 when dependent on claim 8, characterized in that the third lateral surface (150) comprises a face coating (141), the third lateral surface (150) comprises a third conductive lateral surface coating (151), the third conductive lateral surface coating (151) being part of the first conductive continuous coating (101) and the second conductive lateral surface coating (141) being part of the second conductive continuous coating (102).

13. In said one piezoelectric element (10, 10', 10''), said lateral surfaces (130, 140, 150, 160) comprise at least one second lateral surface (140) and at least one fourth lateral surface (160), said second lateral surface (140) being perpendicular to said main tangential axis (h) of said piezoelectric element (10, 10', 10'') and said fourth lateral surface (160) being perpendicular to said minor tangential axis (n) of said piezoelectric element (10, 10', 10''); 10. The acceleration transducer (1) according to claim 9 dependent on claim 8, characterized in that the lateral surface (140) of said acceleration transducer (1) comprises a second conductive lateral surface coating (141) and the fourth lateral surface (160) comprises a fourth conductive lateral surface coating (161), said second conductive lateral surface coating (141) and said fourth conductive lateral surface coating (161) being part of said first conductive continuous coating (101) or part of said second conductive continuous coating (102).

14. In the one piezoelectric element (10, 10', 10''), the lateral surfaces (130, 140, 150, 160) include at least one third lateral surface (150) and at least one fourth lateral surface (160), the third lateral surface (150) being perpendicular to the main tangential axis (h) of the piezoelectric element (10, 10', 10'') and the fourth lateral surface (160) being perpendicular to the minor tangential axis (n) of the piezoelectric element (10, 10', 10''); 10. The acceleration transducer (1) according to claim 9 when dependent on claim 8, characterized in that the lateral surface (150) of said acceleration transducer (1) comprises a third conductive lateral surface coating (151) and the fourth lateral surface (160) comprises a fourth conductive lateral surface coating (161), said third conductive lateral surface coating (151) being part of said first conductive continuous coating (101) and said fourth conductive lateral surface coating (161) being part of said second conductive continuous coating (102).

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