Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
  • G01P3/42—Devices characterised by the use of electric or magnetic means
  • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
  • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
  • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
  • G01P3/489—Digital circuits therefor

Definitions

• the invention relates to a sensor arrangement for detecting movements, in which a sensor signal is generated in an active sensor by an encoder acted upon by the movement, and which has a first device with which the sensor signal together with at least one piece of additional information can be transmitted to an evaluation device Output signal is implemented.
• Sensor arrangements of this type are known, for example, from WO 98/09173 and are used in particular for detecting the turning behavior of a vehicle wheel (wheel speed sensors) in slip-controlled brakes or anti-lock braking systems.
• the rotary movement is carried out by a pulse generator present in the encoder (for example a magnetic pole wheel or a steel gear wheel) and detected by an active sensor, the transducer of which, for. B. is a Hall element or a magnetoresistive bridge (AMR bridge), the / which responds specifically to modulations of the flux density or the field strength by the pulse generator.
• a pulse generator present in the encoder (for example a magnetic pole wheel or a steel gear wheel) and detected by an active sensor, the transducer of which, for. B. is a Hall element or a magnetoresistive bridge (AMR bridge), the / which responds specifically to modulations of the flux density or the field strength by the pulse generator.
• AMR bridge magnetoresistive bridge
• the signal voltage generated in this way is converted with the aid of an amplifier / trigger circuit into a binary sensor signal with two constant amplitude values, the edge changes of which are evaluated to determine the speed of movement. Since the signal voltage depends on the size of the air gap between the sensor and the encoder, it must be ensured that the air gap does not exceed a certain limit air gap.
• the sensor signal present at the sensor output leaves none due to the internal amplifier / trigger circuit
• the invention is therefore based on the object of providing a sensor arrangement of the type mentioned at the outset in which the size of the air gap between the active sensor and an encoder and in particular impermissible changes in the air gap can be detected in order to provide a corresponding status signal in good time before a possible exposure of the sensor signal generate or take other precautions.
• this solution enables a relatively simple evaluation and determination or control of the size of the air gap. This can be done after installing the sensor arrangement and in the course of regular maintenance. - 3 -
• the first device then preferably generates a pulse signal in which the sensor signal is coded with first current pulses and the additional information is coded with second current pulses, a first current level being provided for the first current pulses and a second current level being provided for the second current pulses.
• the first current level is approximately twice as large as the second current level relative to a common reference level.
• the first device preferably comprises a signal processing device with which further additional information in the form of status signals or numerical values can be transmitted, which contain, for example, information about a direction of rotation, temperatures, etc.
• FIG. 1 is a block diagram of a sensor arrangement according to the invention
• Fig. 2 shows a course of a pulse signal at the output of the sensor arrangement and Fig. 3 shows the pulse signal in detail.
• the sensor arrangement comprises an active sensor 1, in which a sensor signal is generated by an encoder E, which is acted upon by a movement and which is transmitted to a first device 2, 3, 4, 5 together with several additional - 4 -
• the encoder E contains a pulse generator which executes the movement to be measured, which is generally a rotary movement.
• the pulse generator has, for example, a steel gearwheel or a permanent magnetic structure, the movement of which generates a corresponding signal voltage in a sensor M (Hall element or magnetoresistive bridge) present in the sensor.
• This signal voltage is converted in a known manner with a sensor-internal amplifier / trigger circuit (not shown) into a sensor signal 60 (FIG. 2) with two constant amplitude values.
• the active sensor 1 contains a second device la, with which the signal voltage dependent on the air gap d between the active sensor 1 and the encoder E is measured, and a third device 1b, which is used to measure a sensor temperature.
• the outputs of the sensor 1 are connected to the inputs of a signal processing device 2. Furthermore, a shift register 3 is provided, the inputs of which are applied to the outputs of the signal processing device 2.
• the measured signal voltage is transmitted to the signal processing device 2 as an analog value.
• the analog signal is digitized by 3-bit coding and converted into a bit sequence 40 (bits 5 to 7).
• the measured signal voltage is compared in the signal processing device with a minimum value and, in the case in which the signal voltage is smaller than the minimum value, a first 1-bit status signal (bit 0) is generated.
• the signal processing device 2 further preferably comprises a direction of rotation detection, with which a second 1-bit status signal (bit 4) for identifying the direction of rotation, that is to say a rotation of the encoder in a reference direction or opposite thereto, is generated.
• bit 4 a second 1-bit status signal
• a third 1-bit status signal (bit 3) can also be derived from the detected direction of rotation, which indicates the validity of the direction of rotation.
• a fourth status signal (bit 2) can be generated from the temperature measured with the third device 1b, which indicates whether the temperature of the sensor arrangement is in a permissible range.
• bit 1 Another bit signal (bit 1) is reserved for additional information, while bit 8 is a parity bit. - 6th
• bit-coded signals are transmitted as additional information by the signal processing device 2 in parallel into the shift register 3 and temporarily stored there.
• the state generator 4 controls the current source 5 in such a way that a pulse signal is present at its output 5c, which contains both the movement information (first current pulses Ig) and the additional information (second current pulses IM), which in the form of a signal in FIGS and 3 shown data protocol are transmitted.
• the different current levels can be generated by switching between different individual current sources 5a, 5b or in some other way.
• the state generator 4 Upon receipt of the sensor signal 60, the state generator 4 controls the current source 5 in such a way that a first current pulse of the height Ig with the same duration 10 is always generated at its output 5c.
• the first current pulse is used to encode one of the edges 61, 62 of the sensor signal 60, the frequency of which is higher, the greater the speed of rotation or movement of the pulse generator in the encoder E. - 7 -
• Each first current pulse is followed by a first pause interval of constant length 20, during which the current level is reduced to the reference level II.
• a first bit sequence 30 comprises the current pulses (bits) 0 to n and is used for coding status signals according to the 1-out-of-n code, so that each individual bit can be assigned separate status information.
• this first bit sequence 30 comprises bits 0 to 4 with the following assignment:
• Bit 0 is a status signal to indicate that an admissible air gap limit value has been exceeded, which is derived from the measurement of the signal voltage at the sensor and the resulting air gap field strength between the sensor and the encoder of the encoder.
• the permissible air gap limit value is considered to be exceeded when the sensor la (magnetoresistive bridge or Hall element) of the active sensor 1 generates a signal voltage which is below twice the hysteresis of the above-mentioned, downstream trigger circuit. Bit 1 is reserved for additional applications.
• Bit 2 represents a status signal for identifying the exceeding of a wheel speed-independent limit value of an additional measured variable, such as a temperature, which is measured with the third device 1b.
• Bit 3 is a status signal to confirm the validity of the direction of rotation of the pulse generator indicated by bit 4.
• bit 4 is a status signal for the direction of rotation of the pulse generator compared to a specified reference direction of rotation.
• a immediately following second bit sequence 40 is used in its entirety to encode numerical values, so that the bits (n + 1) to (p-1) can be used to transmit the measured values of analog signal quantities which result from the (magnetic) interface between the Encoder E and the active sensor 1 can be obtained.
• the length of the second bit sequence 40 is arbitrary. Overall, it can preferably be used to transmit a single analog value. On the other hand, a combination of analog values can also be transmitted simultaneously, with each analog value being assigned a defined number of bits and their position in the second bit sequence 40. The different analog values can also be combined with different codes. - 9 -
• the second bit sequence 40 comprises three bits 5 to 7, which are used for 3-bit coding of a numerical value representing the air gap field strength, which is detected by the transducer la of the active sensor, the bits 5, 6, 7 increasing value (LSB-MSB).
• This numerical value represents in particular the signal voltage at the sensor la of the sensor.
• a single parity bit p follows the second bit sequence 40.
• a second pause interval with a duration of 50 and a current level of level II (cf. FIG. 2).
• the duration depends on the speed of movement of the pulse generator and extends until a new first current pulse I H occurs , whereupon the pulse signal is transmitted again.

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• General Physics & Mathematics (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)

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• 1999
  • 1999-03-17 US US09/646,692 patent/US6542847B1/en not_active Expired - Lifetime
  • 1999-03-17 WO PCT/EP1999/001752 patent/WO1999049322A1/de not_active Application Discontinuation
  • 1999-03-17 EP EP99915641A patent/EP1064559A1/de not_active Withdrawn
  • 1999-03-17 DE DE19911774A patent/DE19911774B4/de not_active Expired - Lifetime
  • 1999-03-17 JP JP2000538241A patent/JP2002507751A/ja active Pending

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