Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
  • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
  • G01L9/0058—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of pressure sensitive conductive solid or liquid material, e.g. carbon granules
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0001—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
  • G01L9/0002—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using variations in ohmic resistance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
  • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
  • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
  • G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
  • G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
  • G01L9/045—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges with electric temperature compensating means

Definitions

• the invention relates to a sensor according to the preamble of the main claim.
• Measuring a pressure in a medium has become known, in particular for measuring high pressures, for example the oil pressure in hydraulic systems or in fuel injection pumps.
• the sensor according to the invention with the characterizing features of the main claim has the advantage that an incredibly simple and thus inexpensive to manufacture arrangement is possible by using conventional resistance components.
• temperature compensation can be brought about by exposing only part of the elements of the bridge to pressure and the other part being pressure-shielded.
• Such an arrangement can be implemented in a particularly simple manner in thick-film technology in that the part of the bridge to be shielded in a pressure-tight manner is provided with a ring and a cover plate.
• the occurrence of temperature-related Error signals due to the inflow of the medium are reduced in that elements of the bridge are provided with an elastic covering layer which, however, does not distort the detection of the static or dynamic pressure.
• the lower usable cut-off frequency of the sensor can be significantly reduced in dynamic measurements without temperature compensation.
• the output signal is increased by using elements in the bridge which have a different pressure coefficient.
• elements in the bridge which have a different pressure coefficient.
• a further increase in the output signal is brought about in that the elements are arranged on a support which can be deformed elastically under the action of pressure, whereby the elements are simultaneously exposed to the action of pressure and an expansion or compression. It is particularly advantageous, when using a laterally clamped membrane, to arrange the elements of a bridge in a defined manner on the membrane so that they are each in the range of positive or negative expansion of the membrane, with resistance materials such as those with positive or negative pressure coefficients Use come so that the above-mentioned high output signal is produced by the superimposition of the signals by pressure and deformation.
• FIG. 1 shows the circuit diagram of a bridge arrangement as can be used in the sensor according to the invention
• Figure 2 is a sectional view through a first embodiment of a sensor according to the invention
• Figure 3 is a sectional view through a second embodiment of a sensor according to the invention
• FIG. 4 shows a sectional view through a third embodiment of a sensor according to the invention
• FIG. 5 shows a sectional view through a fourth embodiment of a sensor according to the invention using thick-film technology
• FIG. 6 shows a further circuit diagram of a bridge arrangement as can be used in the sensors according to the invention.
• the sensor according to the invention is intended to measure pressures in a medium using at least one element which changes its resistance under the action of pressure.
• the sensor is particularly suitable for measuring high pressures, such as those that occur in hydraulic systems or injection pumps of internal combustion engines.
• the sensors are part of a control system in which various operating parameters are used to control an internal combustion engine, including the injection quantity, which is determined indirectly via the pressure in the injection pump.
• the Ta resistors produced with the addition of air to the discharge gas by sputtering in contrast to the literature value for Have tantalum negative pressure coefficients; the TaNi resistors formed from the entire layer, on the other hand, have a positive pressure coefficient.
• the absolute pressure of the pressure coefficient for Ta resistors is of the order of magnitude of manganine, from which resistors for direct pressure measurement can advantageously be produced, as described in the earlier application F 30 28 188.0.
• the pressure coefficient of TaNi resistors is about two to three times larger.
• a bridge circuit 10 which consists of four resistors 11, 12, 13, 4.
• a bridge voltage U B is applied to one bridge diagonal, the measuring voltage U M is taken from the other bridge diagonal, which voltages can of course also be interchanged.
• the diagonally opposite resistors are now made of the same material, namely resistors 11, 13 made of Ta, resistors 12, 11 made of TaNi. Due to the different pressure coefficients specified above, the bridge circuit 10 shown in FIG. 1 accordingly has six to eight times the pressure sensitivity to a bridge made up of ganine resistors.
• the bridge arrangement according to FIG. 1 is used to measure dynamic pressures, in which absolute amounts are not important, the temperature dependence of the bridge signal does not interfere.
• the lower limit frequency for such dynamic measurements is also determined by the reaction speed of the bridge to temperature changes in the pressure medium.
• the bridge arrangement shown in Figure 1 in a flowing medium can Falsifications of the measurement result occur in that the medium flows against the resistors 11 to 14 and thereby causes temperature-related false signals.
• the resistors 11 to 1 4 are covered with an elastic organic protective layer, for example silicone, so that the sensitivity during pressure measurements is not impaired.
• an elastic organic protective layer for example silicone
• FIG. Carrier of the sensor is a screw 15 which, provided with a seal 16, can be screwed into a pressure housing 17.
• the pressure housing is, for example, the wall of a hydraulic element or an injection pump in a motor vehicle.
• the screw 15 is provided with an axial bore 18 into which a multi-core feed line 19 extends pressure-tight from the outside.
• the feed line 19 is fastened in the bore 18 to a plate 20 on which the resistor arrangement 21, for example a bridge circuit 10 according to FIG. 1, is arranged.
• the flat rather. 20 with the resistor arrangement 21 is surrounded by an elastic covering layer 22, as described above.
• the elastic covering layer 22 is in turn protected with a protective grid 23 against mechanical damage.
• FIG. 1 Another practical exemplary embodiment of a sensor according to the invention is shown in FIG.
• a screw 15 is screwed into a pressure housing 17 as a support for the sensor via a seal 16.
• the axial bore 30 is formed continuously by the screw 15.
• the bore 30 is filled with an elastic potting compound 31, a base 32 being seated on the screw head and the potting compound 31 at the end of the screw facing the pressure.
• the base 32 again carries a resistance arrangement 21 covered with an elastic cover layer 22.
• Feedthroughs 33 lead from the base 32 into the sealing compound 31.
• An electronic circuit 35 for example a preamplifier, can be connected to the feedthroughs 33.
• the electronic circuit 35 with its leads 34 is also poured into the potting compound 31.
• the base 32 is preferably designed in the form of an elastically deformable membrane, which, as will be described further below, results in a further increase in the useful signal.
• FIG. 4a and b A third practical embodiment of a sensor according to the invention is shown in FIG. 4a and b in section. shown in top view.
• an axial bore 30 ′ runs in the screw 15, but in this exemplary embodiment is conically stepped outward.
• the bore 30 ' is in turn filled with the elastic casting compound 31 and the base 32', which in a preferred embodiment is designed to be elastically deformable, rests on the pressure-facing end of the screw thread 15.
• the resistance arrangement 21 covered by the elastic covering layer 22 is in turn arranged on the base 32 '.
• the leads 34 of the resistor arrangement 21 lead through the casting compound 31 to the outside. In this way it is possible to construct a particularly simple and inexpensive sensor.
• Such an arrangement can preferably be constructed using thick-film technology, as illustrated in FIG. 5. It goes without saying, however, that this production technology is only given as an example and that the sensor arrangements described here in detail can be constructed with all of the resistor elements mentioned, provided that nothing else arises from the specially used elements and their special properties.
• an Ealb Portugalnancrdnung 39 is used, which consists of the resistors 4 1 and 42 and is arranged on a substrate 40 serving as a base.
• Resistors 41, 42 are particularly suitable for use in thick-film technology, for example cermet, conductive plastic, fiatin, etc. As has been shown, these resistors show an enormously high change in resistance depending on the pressure. It is possible according to the invention to vary the pressure-dependent resistance coefficient within wide limits by selecting the resistance pastes and by adding admixtures of conductive and non-conductive Steffen, as well as their grain size and shape.
• the ring 43 is printed around the resistor 41 from a suitable material, for example glass, ceramic or the like, and the cover plate 44 is placed pressure-tight in a further operation.
• an additional measuring effect can be achieved by specifically designing the cover.
• the thickness of the base 40 or the cover plate 44 it is possible to set the thickness of the base 40 or the cover plate 44 within wide limits. If, as shown in FIG. 5b, the base 40 is made substantially thinner than the cover plate 44, a concave deflection of the base 40 results when pressure is applied, as is indicated in FIG. 5b by the line 15 of the positive deflection. In the opposite case, a thick base 40 results in a convex deflection, as is shown by the line 46 of the negative deflection in FIG. 5c. The deflection of the base 40 results in an expansion or compression of the resistor 41, which opens up the possibility of utilizing this in addition to the pressure load to increase the mechanical load to increase the signal.
• the bridge circuit 50 consists in two opposite branches of resistors 51a, 51b and 53a, 53b and in the other two branches of individual resistors 52 and 54.
• the resistors 51a, 53a are as TaNi resistors and the resistors 51b, 53b Ta resistors formed.
• the resistors 52, 54 consist of a material with a positive pressure coefficient and a temperature coefficient which is in the range of + 200 ppm / ⁇ . These conditions are fulfilled e.g. Silver-manganese alloy layers.
• the bridge branch 51a, b is designed to have a low resistance during manufacture by means of targeted path widening. Due to the usual manufacturing variation of + 5%, the resistance of branch 51a, b can now be increased and the temperature coefficient reduced by laser adjustment, with which a range of + 20% can be adjusted.
• the resistors 51a, 51b it is possible to to set the resistance value and the temperature coefficient of this branch independently of one another, as is described, for example, in DE-OS 29 06 813. Since the TaNi resistor 51a has a smaller value than the resistor 52 but a larger temperature coefficient, this setting can have the effect that the overall temperature coefficient of the bridge circuit 50 is minimized.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Fluid Pressure (AREA)
• Measurement Of Force In General (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6135698

Family Applications (1)

Country Status (4)

Cited By (9)

Families Citing this family (16)

Citations (4)

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• 1981
  • 1981-06-30 DE DE19813125640 patent/DE3125640A1/de not_active Ceased
• 1982
  • 1982-02-18 WO PCT/DE1982/000025 patent/WO1983000225A1/en unknown
  • 1982-02-18 EP EP82900622A patent/EP0082151A1/de not_active Withdrawn
  • 1982-06-23 IT IT22023/82A patent/IT1151655B/it active

Patent Citations (4)

Non-Patent Citations (3)

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