JP2007200079A - Sensor system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide detected data, with high accuracy, after correction by shortening the time from the detection of a physical quantity (temperature, pressure, etc.) until the transmission completion of the detected data. <P>SOLUTION: Power of a power supply supplied from a reading device 20 is transmitted to a detection unit 10 mounted on a detection target through a non-contact magnetic field coupling. A physical quantity of the detection target is detected by a sensor element 11, a detection circuit 12, and a control circuit 14 in the unit 10. Since in the element 11 and circuits 12, 14, the physical quantities thereof are detected from a change in a relative frequency of two oscillating circuits, a sensor system makes offset adjustment and full scale adjustment of the detected result, and further, chancels the fluctuation in the oscillation circuit properties by means of the two oscillation circuits. The system transmits the detected result after such adjustment and the correction data of sensor element characteristics stored in a memory 13 through the non-contact magnetic field coupling, to the reading device 20 and performs correction computing of the sensor element characteristics of the correction data for the detected result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a physical quantity (for example, temperature, pressure, stress, displacement, acceleration, electric quantity, etc.) of a moving detection object is detected by a sensor attached to the detection object, and the detection result is non-contacted. The present invention relates to a sensor system that reads and corrects detection errors and the like.

  Conventionally, as a sensor system for detecting a physical quantity of a moving detection target, for example, techniques described in Patent Documents 1, 2, and 3 below are known. In the sensor systems described in Patent Documents 1 to 3, a detection unit having a sensor element and a transmitter is mounted on the tire side of a vehicle, and the detection unit detects the tire pressure and temperature and wirelessly transmits the detection result. And the transmission signal is received by a receiver on the vehicle body side to determine whether or not an abnormality has occurred in the tire, thereby improving the safety of the vehicle.

JP 2004-161113 A JP 2003-291615 A JP-A-10-104103

  However, the conventional sensor system has the following problems (A) and (B).

(A) Problems due to wireless transmission of detection results Conventionally, a detection unit having a sensor element and a transmitter is mounted on the tire side of the vehicle, and the air pressure and temperature of the tire are detected, and the detection result is wirelessly transmitted to the vehicle body side. Although it is configured to transmit to the receiver, since a battery for supplying power is provided in the detection unit, maintenance and inspection for battery consumption is necessary, which is disadvantageous.

  Further, as described in paragraph 0028 of Patent Document 1, while the vehicle is running, the detection unit attached to the tire rotates as the tire rotates, so that the vehicle body side depends on the rotation angle of the detection unit. The reception sensitivity of the receiver changes, and there is a point that the receiver cannot receive within a certain rotation angle range (this point is also referred to as “null point”). In order to prevent this, it is sufficient to increase the power of the transmission radio wave. However, since such problems as radio wave regulation and interference occur, such measures cannot be taken. Therefore, in the technique of Patent Document 1, the detection data is wirelessly transmitted from the transmitter to the receiver in a tire rotation angle range (for example, a range of 180 ° ± 60 °) that avoids the null point.

  However, in such a configuration, since the detection data must be transmitted within a short time within a limited rotation angle range during one rotation of the tire, the detection unit operates until the detection data transmission is completed. If the time is long, data transmission is interrupted. In order to avoid this, if data transmission is completed in a short time, the data transmission rate must be increased. However, if the data transmission rate is increased, the bandwidth required for wireless communication is increased and the signal pair of the communication line is increased. There arises a problem that it is difficult to ensure the noise ratio (S / N ratio) at or above the allowable value.

(B) Issues regarding correction of detection results Since there are manufacturing variations in sensor element characteristics, conventionally, for example, when a detection unit having a sensor element and a transmitter is manufactured, this detection unit is required to operate. A correction amount corresponding to the detection accuracy is obtained, correction calculation is performed on the detection value of the sensor element, and the corrected detection result is output from the detection unit. However, when the detection unit having such a configuration is used on the tire side, the time until the detection unit operates and completes transmission of detection data for correction calculation or the like becomes longer, and the (A) As described in (1), there is a problem that data transmission is interrupted in the middle, so that it is difficult to correct the detection value of the sensor element, and it is difficult to improve the detection accuracy. Further, for the sensor elements having different characteristics, a correction function for performing different correction calculations and the like must be provided in the detection unit, which is disadvantageous.

  The sensor system of the present invention is a detection unit mounted on a moving detection object, and is installed apart from the detection unit, and detects the signal on which power is superimposed without contact with the detection unit. A reading device that transmits to the unit and receives a signal from the detection unit.

  The detection unit extracts first power from the signal received by the first receiving means, and receives the signal on which the power is superimposed, and extracts the power from the signal received by the first receiving means to an internal circuit of the detection unit. Power supply means to supply, a sensor element whose electrical characteristic value changes in response to a change in physical quantity in the detection object, and a reference whose electrical characteristic value is different from the sensor element with respect to the change in physical quantity An element, a first oscillation circuit that oscillates at a frequency determined based on an electrical characteristic value of the sensor element, and a second oscillation circuit that oscillates at a frequency determined based on the electrical characteristic value of the reference element Detecting a relative frequency change between the first and second oscillation circuits to detect a change in the physical quantity and outputting detection data; and correcting an electrical characteristic value of the sensor element Supplement A data storage unit that stores data, and the correction data of the detection data and in the data storage means and a first transmission means for transmitting to the reader.

  Furthermore, the reading device receives the detection data and the correction data transmitted from the detection unit, and second transmission means for transmitting the signal on which the power supply power is superimposed to the detection unit. Receiving means, and calculating means for performing correction calculation of the correction data received by the second receiving means on the detection data received by the second receiving means to obtain corrected detection data. Have.

  According to the present invention, since the power supply power is supplied from the reading device to the detection unit in a non-contact manner, the maintenance check for the battery consumption in the detection unit as in the past is not required, and the usability is improved. To do. Since the detection unit detects the physical quantity from the relative frequency change of the first and second oscillation circuits, the detection data can be adjusted for offset and full scale. It can be canceled by the first and second oscillation circuits. The adjusted detection data and the correction data stored in the data storage means are transmitted to the reading device in a non-contact manner, and the correction data is corrected by the calculation means in the reading device. Since the sensor element characteristics are corrected, data can be transmitted from the detection unit to the reading device in a short time, and the detection result can be read and corrected with low power consumption and high accuracy. In addition, even if communication is interrupted and transmission of correction data in the latter half of communication fails, for example, it is possible to correct sensor element characteristics using the previous correction data.

  The sensor system is installed separately from the detection unit mounted on the moving detection target, and is separated from the detection unit. The sensor system transmits a signal on which power is superimposed without contact to the detection unit. And a reading device for receiving a signal from the detection unit. The detection unit and the reading device exchange signals by non-contact magnetic field coupling.

  The detection unit includes first reception means, power supply means, sensor elements, reference elements, first and second oscillation circuits, detection circuits, data storage means, and first transmission means.

  The first receiving means receives the signal on which the power supply power is superimposed. The power supply means extracts the power supply power from the signal received by the first receiving means and supplies it to the internal circuit of the detection unit. The sensor element has an electrical characteristic value that changes in response to a change in a physical quantity in the detection object. The reference element is different from the sensor element in the electrical characteristic value with respect to the change in the physical quantity. For example, the reference element is configured by an element in which the electrical characteristic value is constant with respect to the change in the physical quantity. ing.

  The first oscillation circuit oscillates at a frequency determined based on an electrical characteristic value of the sensor element. The second oscillation circuit oscillates at a frequency determined based on an electrical characteristic value of the reference element. The detection circuit obtains a relative frequency change between the first and second oscillation circuits, detects a change in the physical quantity, and outputs detection data. The data storage means stores correction data for correcting an electrical characteristic value of the sensor element. The first transmission unit transmits the detection data and the correction data in the data storage unit to the reading device.

  Further, the reading device has a second transmission unit, a second reception unit, and a calculation unit.

  The second transmission means transmits the signal on which the power supply is superimposed to the detection unit. The second receiving means receives the detection data and the correction data sent from the detection unit. The calculation means obtains corrected detection data by performing a correction calculation of the correction data received by the second reception means on the detection data received by the second reception means.

(Configuration of FIGS. 1 and 2)
FIG. 1 is a schematic configuration diagram of a sensor system showing Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a tire of a vehicle to which the sensor system of FIG. 1 is applied.

  The sensor system shown in FIG. 1 detects, for example, the pressure of the tire 1 of the vehicle shown in FIG. 2 and the temperature closely related to this pressure as a moving detection object. A detection unit 10 that is embedded, and a reading device 20 that is attached to the vehicle body side away from the detection unit 10 and that supplies power to the detection unit 10 and transmits / receives data by non-contact magnetic field coupling; It has.

  The detection unit 10 includes a sensor element 11 having a temperature detection sensor element 11A that detects the temperature of the tire 1 and a pressure detection sensor element 11B that detects the pressure of the tire 1, and the sensor element 11 includes a temperature detection circuit. A detection circuit 12 having 12A and a pressure detection circuit 12B is connected.

  For example, the temperature detecting sensor element 11A constituting the sensor element 11 is configured by a thermistor resistance element or the like having a large temperature dependency, and the pressure detecting sensor element 10B is a variable capacitor or the like whose capacitance value changes by an external pressure. It is configured. The temperature detection circuit 12A constituting the detection circuit 12 is a circuit having a function of converting the temperature detection value detected by the temperature detection sensor element 11A into temperature detection data consisting of a digital signal, and the pressure detection circuit 12B is This is a circuit having a function of converting the pressure detection value detected by the pressure detection sensor element 11B into pressure detection data comprising a digital signal.

  Since the sensor elements 11A and 11B have non-linear electrical characteristic values, correction data for linearly correcting the sensor elements 11A and 11B (this correction data includes data related to a correction arithmetic expression, etc.). Data storage means (for example, a memory) 13 for storing in advance is provided. A control circuit 14 having a temperature control circuit 14A and a pressure control circuit 14B is connected to the detection circuit 12 and the memory 13. The control circuit 14 is a circuit that controls the entire detection unit 10, and includes, for example, a central processing unit (hereinafter referred to as “CPU”), an individual circuit, or the like.

  The control circuit 14 is connected to a power source means (for example, a rectifier circuit) 15, a first receiving means (for example, a receiving circuit) 16, and a first transmitting means (for example, a transmitting circuit) 17. , 16, 17, etc. are connected to an antenna coil 18 that exchanges power and signals in a contactless manner, and this antenna coil 18 is wound around a bar antenna 19. A capacitor (not shown) is connected to the antenna coil 18, and the antenna coil 18 and the capacitor are tuned to the frequency of the alternating magnetic field supplied from the reading device 20.

  The rectifier circuit 15 is a circuit that rectifies the AC electromotive voltage induced in the antenna coil 18 to generate a DC power supply voltage for driving the detection unit, and supplies this to the control circuit 14 and the like. The receiving circuit 16 receives a control signal from the reading device 20 superimposed on the AC electromotive voltage induced in the antenna coil 18, demodulates the control signal, and gives a command (command) and data to the control circuit 14. Circuit. The transmission circuit 17 is a circuit that generates a transmission signal by modulating detection data and correction data supplied from the control circuit 14 and transmits the transmission signal to the reading device 20 via the magnetic field coupling of the antenna coil 18. .

  The reading device 20 includes a loop antenna 21 that is magnetically coupled to the antenna coil 18, an oscillation circuit 22 that oscillates a carrier for power supply power (for example, a carrier of 125 KHz), and a modulation circuit 23 that is connected to the oscillation circuit 22. A second transmission means (for example, a transmission circuit) 24 connected between the modulation circuit 23 and the loop antenna 21; a second reception means (for example, a reception circuit) 25 connected to the loop antenna 21; And a demodulation circuit 26 connected to the reception circuit 25. Further, the modulation circuit 23 and the demodulation circuit 26 are connected to a control circuit 27 having a data correction processing function by an arithmetic means and a host controller 29 composed of a computer that controls the entire sensor system via an interface 28. Yes.

  The modulation circuit 23 is a circuit that modulates a command or data output from the control circuit 27 with a carrier for power supply power supplied from the oscillation circuit 22. The transmission circuit 24 is a circuit that converts the modulation signal modulated by the modulation circuit 23 into a transmission signal and transmits the transmission signal to the detection unit 10 via the loop antenna 21. The reception circuit 25 is a circuit that receives detection data and correction data transmitted from the detection unit 10 via the loop antenna 21. The demodulation circuit 26 is a circuit that demodulates the detection data and correction data received by the reception circuit 25 and outputs them to the control circuit 27. The control circuit 27 receives the detection data and the correction data from the demodulation circuit 26, performs correction calculation of the correction data on the detection data by the calculation means, obtains corrected detection data, and uses the detection data as an interface. 28 is a circuit for sending to the host controller 29 via 28.

(Configuration of FIG. 3)
FIG. 3 is a circuit diagram showing a configuration example of the temperature detection sensor element 11A, the temperature detection circuit 12A, and the temperature control circuit 14A in FIG.

  The sensor element 11A is formed of, for example, a thermistor resistance element having a large temperature dependency in which the resistance value Rth varies with temperature, and a detection circuit 12A is connected to the sensor element 11A. The detection circuit 12A is, for example, a circuit that detects a temperature by using a resistance element in a time constant circuit including a capacitance element and a resistance element that determine an oscillation frequency of the CR oscillation circuit. The detection circuit 12A includes a control circuit. 14A is connected. The control circuit 14A includes a control unit that outputs various control signals and temperature detection data (for example, count numbers N1, N2) for controlling the detection circuit 12A, a calculation unit, a data storage unit, and the like. It is composed of a CPU and the like.

  The detection circuit 12A is connected to a reference element (for example, a reference resistance element) 31A having a reference fixed resistance value Rref, a first oscillation circuit 32-1A connected to the sensor element 11A, and the reference resistance element 31A. And a second oscillation circuit 32-2A having the same characteristics as the first oscillation circuit 32-1A. The first oscillation circuit 32-1A constitutes a CR oscillation circuit together with the sensor element 11A, operates in accordance with the control signal of the control circuit 14A, oscillates at a frequency corresponding to the resistance value of the sensor element 11A, and outputs a clock signal. Circuit. The second oscillation circuit 32-2A constitutes a CR oscillation circuit together with the reference resistance element 31A, operates in accordance with the control signal of the control circuit 14A, oscillates at a frequency corresponding to the resistance value of the reference resistance element 31A, and generates a clock signal. Is a circuit that outputs.

  The detection circuit 12A includes a first memory 33-1A that operates in accordance with a control signal from the control circuit 14A and sets a set number (for example, a set value) M1 that is a count (count) number, and a control by the control circuit 14A. A second memory 33-2A that operates by a signal to set the set value M2 and a reference signal source 35A that includes a crystal oscillation circuit that outputs a reference frequency signal fref including a reference clock signal are provided. Yes. A first counting means (for example, a first counter) 34-1A is connected to the output side of the first memory 33-1A, and the first counter is also connected to the output side of the second memory 33-2A. A second counting means (for example, a second counter) 34-2A having the same characteristics as 34-1A is connected.

  The first counter 34-1A operates in accordance with the control signal of the control circuit 14A, and counts the number of output clock signals of the oscillation circuit 32-1A by the number of times of the set value M1 set in the first memory 33-1A. The third counting means (for example, a third counter) 34-3A is connected to the output side. The second counter 34-2A operates in accordance with the control signal of the control circuit 14A, and counts the number of output clock signals of the oscillation circuit 32-2A by the number of times of the set value M2 set in the second memory 33-2A. The fourth counting means (for example, a fourth counter) 34-4A is connected to the output side.

  The third counter 34-3A is operated by the control signal of the control circuit 14A, and is output from the reference signal source 35A during a period in which the first counter 34-1A performs the counting operation for the number of times of the set value M1. The number of clocks of the reference frequency signal fref is counted, and this count number N1 is stored in the control circuit 14A. The fourth counter 34-4A has the same characteristics as the third counter 34-3A, operates according to the control signal of the control circuit 14A, and the second counter 34-2A performs the counting operation for the number of times of the set value M2. During this period, the number of clocks of the reference frequency signal fref output from the reference signal source 35A is counted, and this count number N2 is stored in the control circuit 14A. The count number N1 corresponds to the set value M1, and the count number N2 corresponds to the set value M2.

(Configuration of FIG. 4)
4 is a circuit diagram showing a configuration example of the pressure detection sensor element 11B, the pressure detection circuit 12B, and the pressure control circuit 14B in FIG. 1, and is the same element as the element (numeral + A) in FIG. Are assigned a common code (same number + B).

  In the circuit of FIG. 4, instead of the sensor element 11A and the reference resistance element 31A made of the thermistor resistance of FIG. 3, a capacitive sensor element 11B and a reference capacitance element 31B are provided, and the tire 1 is formed using the sensor element 11B. The pressure is detected.

  In the circuit of FIG. 4, a control circuit 14B that outputs various control signals and pressure detection data D14B for controlling each circuit block, and operates according to the control signal of the control circuit 14B to operate the capacitance value Cs of the sensor element 11B. The first oscillation circuit 32-1B that oscillates at an oscillation frequency determined by the first oscillation circuit 32-1B, and the second oscillation circuit 32 that operates by a control signal from the control circuit 14B and oscillates at an oscillation frequency determined by the fixed capacitance value Cref of the reference capacitance element 31B. -2B, the first memory 33-1B that operates by the control signal of the control circuit 14B and sets the setting value M1 that is the number of counts, and the operation signal by the control signal of the control circuit 14B sets the setting value M3, It has a third memory 33-3B for giving the count number N3 corresponding to this to the control circuit 14B.

  A second counter 34-2B is connected to the output side of the second oscillation circuit 32-2B and the first memory 33-1B. The second counter 34-2B operates according to the control signal of the control circuit 14B, and counts the number of output clock signals of the second oscillation circuit 32-2B by the number of times of the set value M1 in the first memory 33-1B. The first counter 34-1B is connected to the output side. The first counter 34-1B is operated by the control signal of the control circuit 14B, and the number of output clock signals of the first oscillation circuit 32-1B is set while the second counter 34-2B is counting. Counting is performed and the count number N1 is output to the control circuit 14B. The control circuit 14B has a function of outputting various control signals and pressure detection data (for example, count numbers N1, N3).

(Operation of Example 1)
FIG. 5 is a time chart showing the operation of the detection data transmission and correction method of FIG. The horizontal axis in FIG. 5 is time.

  First, when a command or data for operating the detection unit 10 is output from the host device 29 in the reading device 20 of FIG. 1, the command or data is sent to the control circuit 27 via the interface 28. Under the control of the control circuit 27, the reading device 20 shifts to the operation mode. When the reading device 20 shifts to the operation mode, the modulation circuit 23 operates, and the control signal from the control circuit 27 is modulated by the carrier for power source output from the carrier oscillation circuit 22. When this modulated signal is converted into a transmission signal by the transmission circuit 24 and sent to the loop antenna 21, an alternating magnetic field is generated from the loop antenna 21.

  When the detection unit 10 embedded in the side portion of the tire 1 rotates together with the tire 1 and the antenna coil 18 of the detection unit 10 approaches the loop antenna 21, an AC electromotive voltage is induced in the loop antenna 21. The induced AC electromotive voltage is rectified by the rectifier circuit 15 to generate a DC power supply voltage. This DC power supply voltage is supplied to the control circuit 14 (power ring), and the detection unit 10 shifts to the operation mode. When the operation mode is shifted, the AC electromotive voltage induced in the antenna coil 18 is received and demodulated by the receiving circuit 16, and the demodulated command and data from the reading device 20 are sent to the control circuit 14. 14, the temperature control circuit 14A, the temperature detection circuit 12A, and the temperature detection sensor element 11A in FIG. 3, and the pressure control circuit 14B, the pressure detection circuit 12B, and the pressure detection sensor element 11B in FIG. The following operations (1) and (2) are performed.

(1) Operation of FIG. 3 First, the first oscillation circuit 32-1A oscillates at a frequency corresponding to the resistance value Rth of the sensor element 11A by the control signal of the control circuit 14A, and the second oscillation circuit 32- 2A oscillates at a frequency corresponding to the resistance value Rref of the reference resistance element 31A by the control signal of the control circuit 14A. The set value M1 in the first memory 33-1A is loaded into the first counter 34-1A by the control signal of the control circuit 14A, and at the same time in the second memory 33-2A by the control signal of the control circuit 14A. Is set to the second counter 34-2A. The first and second counters 34-1A and 34-2A operate according to the control signal of the control circuit 14A, and the number of clock signals output from the first oscillation circuit 32-1A by the first counter 34-1A. Is counted, and the number of clock signals output from the second oscillation circuit 32-2A is counted by the second counter 34-2A.

  During the period in which the first counter 34-1A performs the count operation of the set value M1, the third counter 34-3A is operated by the control signal of the control circuit 14A, and the number of clocks of the reference frequency signal fref is counted. The count number N1 is stored in the control circuit 14A. At the same time, the fourth counter 34-4A is operated by the control signal of the control circuit 14A while the second counter 34-2A performs the count operation of the set value M2 times, and the number of clocks of the reference frequency signal fref is set. The count number N2 is stored in the control circuit 14A.

(2) Operation of FIG. 4 First, the set value M1 in the first memory 33-1B is loaded into the second counter 34-2B by the control signal of the control circuit 14B, and at the same time by the control signal of the control circuit 14B. The first oscillation circuit 32-1B oscillates at an oscillation frequency determined by the capacitance value Cs of the sensor element 11B, and the second oscillation circuit 32-2B oscillates at an oscillation frequency determined by the capacitance value Cref of the reference capacitance element 31B. The number of clock signals output from the second oscillation circuit 32-2B is counted by the second counter 34-2B operated by the control signal of the control circuit 14B.

  During the period when the second counter 34-2B performs the count operation for the set value M1, the first counter 34-1B is operated by the control signal of the control circuit 14B, and output from the first oscillation circuit 32-1B. The number of clock signals to be counted is counted, and this count number N1 is stored in the control circuit 14B.

When the operations (1) and (2) are completed, the third and fourth counters 34-3A and 34-4A are reset by the control signal of the control circuit 14A shown in FIG. 3, and the control shown in FIG. The first counter 34-1B is reset by the control signal of the circuit 14B. Then, the detection data composed of the count numbers N1 and N2 in FIG. 3 and the count number N1 in FIG. 4 stored in the control circuit 14A, and correction data stored in the memory 13 (this correction data includes a correction arithmetic expression). Data, etc. are also included) by the transmission circuit 17 is converted into the following transmission signal, for example.
Transmission signal = synchronization signal + start signal +
Detection data + error detection correction code + correction data + end signal

  In this transmission signal, a synchronization signal, a start signal, and an end signal are signals added for data transmission. In addition, data transmission from the detection unit 10 operating in a non-contact manner to the reading device 20 may become unstable due to the influence of disturbance depending on the operating conditions. In order to correct this, an error detection / correction code is provided. It has been added. Such a transmission signal is sent to the reader 20 via the electromagnetic coupling of the antenna coil 18 and the loop antenna 21.

  The transmission signal sent to the reading device 20 side is received by the reception circuit 25, and demodulated by the demodulation circuit 26 into the original count numbers N1 and N2 in FIG. 3 and the count number N1 in FIG. It is sent to the circuit 27. In the control circuit 27, N1 is subtracted from the count number N2 in FIG. 3, and temperature detection data D14A as a subtraction result (N2-N1) is calculated. Since the temperature detection data D14A (= N2-N1) corresponds to the resistance value Rth (that is, the detected temperature) of the sensor element 11A, the temperature of the tire 1 is detected. Further, in the control circuit 27, the count number N3 in FIG. 4 is subtracted from the count number N1, and pressure detection data D14B as a subtraction result (N1-N3) is calculated. Since the pressure detection data D14B (= N1-N3) corresponds to the capacitance value Cs (that is, pressure) of the sensor element 11B, the pressure of the tire 1 is detected.

  In order to correct the non-linearity of the sensor elements 11A and 11B with respect to the detected temperature and pressure values, the control circuit 27 performs a correction operation using the correction data to obtain corrected detection data. .

  As shown in FIG. 5, one operation (41) from the detection unit 10 to the reading device 20 is (detection operation (41a) + communication operation (41b, 41c)). When the duration of power supply to the power source (power ring) is sufficiently long (40-1), two operations (41, 41) are performed, and when the duration of power ring is short (40-2), 1 Operations (41) are performed. Even when the operation of the power ring is too short and one operation (41) is not completed (40-3), at least the transmission rate at which the detection data (41a, 41b) can be transmitted is set in advance. In this case, the correction data (41c) is set to reuse the data sent last time, so that correction calculation is executed and corrected detection data is obtained.

(Effect of Example 1)
6 to 9 are characteristic diagrams showing effects of the first embodiment of the present invention. Among these, FIG. 6 is a characteristic diagram of detection data when correction is not performed according to the first embodiment, and FIG. 7 is a characteristic diagram of detection data after offset adjustment and full scale adjustment according to the first embodiment. (° C.), the vertical axis is detection data. FIG. 8 is a characteristic diagram of correction data, where the horizontal axis represents temperature (° C.) and the vertical axis represents correction data. FIG. 9 is a characteristic diagram of detection data after correction by offset adjustment, full scale adjustment, and correction data. The horizontal axis represents temperature (° C.), and the vertical axis represents corrected correction data.

The first embodiment has the following effects (A) to (C).
(A) Effects (A1) to (A7) of FIG.
(A1) Since the temperature of the tire 1 is detected by the combination of the sensor element 11A and the oscillation circuit 32-1A, and the combination of the reference resistance element 31A and the oscillation circuit 32-2A, the oscillation frequency in the initial state varies. However, initial adjustment (that is, offset adjustment) can be performed under a predetermined condition (count number N1 = N2).

  (A2) The combination of the sensor element 11A and the oscillation circuit 32-1A adjusts the temperature detection data (count value) when a predetermined temperature change is applied to a predetermined value (= N2-N1) (that is, full scale) Adjustment).

  (A3) The adjustment is performed without adjusting the oscillation frequency of the oscillation circuits 32-1A and 32-2A, and by adjusting the data of the surrounding logic circuits (for example, the set values M1 and M2 to the memories 33-1A and 33-2A). Can be adjusted. That is, instead of adjusting the oscillation frequencies of the oscillation circuits 32-1A and 32-2A, the oscillation circuits 32-1A and 32-2A may be operated in a dispersed state without adjusting the resistor R that determines the oscillation frequency. Moreover, since the temperature detection data (count value) when a predetermined maximum temperature change is applied can be adjusted to a predetermined value (= N2-N1) (that is, full scale adjustment), the oscillation circuits 32-1A, 32 can be adjusted. Even if there is a variation in detection characteristics in combination with -2A, it can be adjusted by adjustment, so that the cost can be reduced.

  (A4) By design, if the set values M1 and M2 are increased according to the required detection capability, the time required for detection increases, but the decomposition capability can be improved. At this time, the set values M1 and M2 are selected to be large so that one step of adjustment in the logic circuit is sufficiently small.

  (A5) Since oscillation circuits 32-1A and 32-2A having the same characteristics are used for oscillation by the sensor element 11A and oscillation by the reference resistance element 31A, a change in oscillation frequency is relatively detected. Even if the oscillation frequency changes at the same rate due to the characteristic fluctuation of 32-1A and 32-2A, it is canceled and does not affect the signal. Therefore, it is affected by variations and fluctuations of the oscillation circuits 32-1A and 32-2A. hard.

  (A6) The operations of the first oscillation circuit 32-1A, the first counter 34-1A, and the third counter 34-3A, the second oscillation circuit 32-2A, the second counter 34-2A, and The operation of the fourth counter 34-4A can be executed simultaneously. Therefore, even if the detection time is short and the power supply power applied to the first and second oscillation circuits 32-1A and 32-2A is unstable, the power supply power is supplied to the first and second oscillation circuits. By being simultaneously applied to 32-1A and 32-2A at the same time, the influence of the instability can be reduced. At this time, since it is desirable that the characteristics of the first and second oscillation circuits 32-1A and 32-2A are uniform, for example, it is desirable to arrange them adjacently on the same chip to form an integrated circuit.

  (A7) As shown in FIG. 6, the characteristics of the temperature detection data when the correction according to the first embodiment is not performed are ascending to the right in the series 1 to 7, but the value at the reference temperature is “0”. No (offset adjustment is off), and the value at the maximum temperature is not constant (full scale adjustment is not performed). Series 8 to 10 are examples in which the change curve is reversed and descends to the right. On the other hand, as shown in FIG. 7, when the correction according to the first embodiment is performed, the values at the reference temperature are “0” in any of the series 1 to 10 (the offset is adjusted). The value at the maximum temperature is a constant value (full scale adjustment). For series 8 to 10, the subtraction polarity in the control circuit 27 on the side of the reading device 20 is reversed so as to be unified to the right. As is apparent from FIGS. 6 and 7, the first embodiment has a remarkable effect as compared with the prior art.

(B) Effects of FIG. 4 There are substantially the same effects as the circuit of FIG.

(C) Effect of FIGS. 1 and 2 In the operation sequence of the reference example in FIG. 5, for example, with respect to the detection data (42 a) detected by the sensor elements 11 A and 11 B by the control circuit 14 in the detection unit 10. Then, the correction calculation (42b) for correcting the nonlinear characteristics of the sensor elements 11A and 11B to the linear characteristics is performed using the correction data in the memory 13, and the corrected detection data (42c) is converted into the antenna coil 18 and the loop antenna 21. An example of transmission to the reading device 20 side through electromagnetic coupling is shown.

  Since the sensor elements 11A and 11B have various non-linear characteristics due to manufacturing variations and the like, correction data for correcting the non-linear characteristics to linear characteristics also have various curve characteristics as shown in series 1 to 10 in FIG. . Such correction data is stored in the memory 13 in the detection unit 10 in advance, and the detection data after the offset adjustment and full scale adjustment as described above is corrected by, for example, the control circuit 14 in the detection unit 10. If the calculation is performed, the detection data is corrected to a linear characteristic as shown in FIG. This corrected detection data is transmitted to the reading device 20 side via the antenna coil 18 and the loop antenna 21 in the operation sequence of the reference example. In such an operation sequence of the reference example, communication data from the detection unit 10 to the reading device 20 need only be corrected detection data, so that there is an advantage that the data amount can be shortened. However, there are the following disadvantages.

  Since the sensor element characteristic correction calculation is performed in the detection unit 10, power consumption increases. The correction calculation takes time. Since the correction calculation processing routine is prepared in advance assuming the range of the characteristic variation of the sensor element 11, it is necessary to change the calculation formula in the detection unit 10 according to the sensor type to be combined. In order to have such a degree of freedom, it is not suitable for an application that requires a higher-performance arithmetic function and has a limitation of operating power. When combining with a plurality of sensor elements 11A and 11B having different characteristics, it is necessary to incorporate a correction calculation formula in advance. In order to switch to sensor elements 11A and 11B having different characteristics, a calculation process in the detection unit 10 is performed. Since it is necessary to change, the cost required for changing the specification of the detection unit 10 increases.

In the operation sequence of the reference example, as shown in FIG. 5, one operation (42) is (detection operation (42a) + correction calculation (42b) + communication operation (42c)). Here, the communication operation (42c) is, for example,
Synchronization signal + start signal + corrected data + error detection correction code + end signal. In applications where communication is established by one transmission from the detection unit 10 attached to the rotating tire 1, if the time required for one operation (42) is long, data transmission is interrupted in the middle. End up. In particular, when the demand for detection accuracy is high and the amount of correction data is large, the communication time becomes long and data transmission is interrupted, which is disadvantageous.

  In the first embodiment, such an inconvenience is solved and the correction accuracy is ensured, the one operation time (41) is shortened, the power consumption is reduced, the communication is interrupted in the middle, and correction data in the latter half of the communication is obtained. Even if transmission of (41c) fails, in order to correct the detection data correctly, the detection data and the correction data are sent to the reading device 20, and the sensor device characteristic correction calculation is performed on the reading device 20 side. Yes. As a result, the following effects (C1) to (C4) are obtained.

  (C1) Since the sensor element characteristic correction calculation is not performed on the detection unit 10 side, the time until the start of data transmission is short. Since the correction calculation processing of the sensor element characteristics with large power consumption is not performed on the detection unit 10 side, power ring from the reading device 20 side is easy. In addition, since the power supply power is supplied from the reading device 20 to the detection unit 10 in a non-contact manner, the conventional maintenance check for the battery consumption in the detection unit 10 becomes unnecessary, and the usability is improved. .

  (C2) Even if communication is interrupted during data communication, detection data can be corrected. That is, in one communication (41) from the detection unit 10 to the reader 20, for example, (synchronization signal + start signal + detection data + error detection correction code + correction data + end signal) is sent as data. If data can be sent to at least (synchronization signal + start signal + detection data + error detection / correction code), even if communication is interrupted, the sensor element characteristics can be corrected using the previous correction data. . The correction data is stored in the memory 13 at the time of manufacture, and until the tire 1 is replaced, the same correction data is always sent to the reading device 20 side every time. In some cases, it is sufficient if communication is complete, including correction data. Since the tire 1 may be exchanged, the correction data may be confirmed when communication can be completed.

  (C3) Even if the amount of correction data to be transmitted is reduced in order to correct the detected data, the actual fineness of correction can be maintained.

  For example, based on the values detected by applying a predetermined number of reference conditions to the set temperature and pressure within the detection range, a correction amount map is created and corrected based on the detected values and read. . At this time, a correction curve is obtained by calculation from a value obtained by calculating the correction amount at the time of manufacture.

  In order to increase the accuracy, the correction data is basically increased. However, there is a demand to simplify the data amount for correction and the correction calculation and to ensure the necessary accuracy. As this method, a plurality of types of correction curves are prepared in advance on the reading device 20 side, and data for selecting which type of correction curve is applied to the correction data and the corresponding correction curve are applied. By using the parameters to be used, the amount of data to be prepared for correction in advance on the reading device 20 side increases, but the amount of correction data that must be transmitted can be reduced. The fineness of the actual correction can be maintained. In relative terms, it is more convenient to reduce the amount of correction data that must be transmitted even if the amount of data to be held on the reading device 20 side increases.

As an example of a correction curve to be provided in plural on the reading device 20 side,
Classification of characteristics Polarity classification of change characteristics Presence or absence of hysteresis How to deviate from linearity

As a parameter,
It can be defined according to each correction curve.

  As described above, according to the first embodiment, the combination of the sensor element 11 and the detection circuit 12 is within a detectable range, the characteristic curve exhibits monotonicity within the correction target range, and there is no hysteresis. As shown in FIG. 5, correction can be made to a linear characteristic curve.

  (C4) New correction characteristics can be easily set. That is, since the data correction is performed on the reading device 20 side, the operating power, the required memory amount, the restrictions on the arithmetic device are relaxed, the processing can be performed in a high-level language, and the degree of freedom in design is high, and new correction characteristics are added. Easy to change.

  FIG. 10 is a schematic perspective view showing another application example of the sensor system showing the second embodiment of the present invention.

  In this application example, in a device that loads and transports a product 51 on a rotating conveyor 50, a detection unit 10 for temperature detection is mounted on the conveyor 50, and a reading device 20 is disposed in the vicinity of the conveyor 50 to detect it. The detected temperature data and correction data of the conveyor 50 detected by the unit 10 are transmitted to the reading device 20 in a non-contact manner, and temperature calculation and sensor element characteristic correction calculation are performed on the reading device 20 side. Even in such a sensor system, substantially the same effect as in the first embodiment can be obtained.

  The present invention is not limited to the illustrated first and second embodiments, and various modifications and usage forms are possible. Examples of such modifications and usage forms include the following (a) to (d).

  (A) The detection unit 10 and the reading device 20 can be changed to other circuit configurations other than those illustrated. For example, in FIG. 3 and FIG. 4, the reference resistance element 31A or the reference capacitance element 31B having a constant electrical characteristic value with respect to the change in the physical quantity is used as the reference element. However, other elements having different electrical characteristic values from the sensor elements 11A and 11B may be used, and the circuit configurations of FIGS. 3 and 4 may be changed correspondingly. 3 and 4 use two oscillation circuits, the first oscillation circuits 32-1A and 32-1B and the second oscillation circuits 32-2A and 32-2B. One common oscillation circuit may be provided, and this may be changed to a configuration that is switched by a switching unit.

  (B) The detection unit 10 and the reading device 20 are configured to exchange power and signals by magnetic field coupling, but may be changed to other non-contact coupling methods such as radio wave coupling.

  (C) In FIG. 1, the sensor element 11A for temperature detection and the sensor element 11B for pressure detection are used as the sensor element 11, and the detection unit 10A for temperature detection is used in FIG. As physical quantities of the object, various things such as stress, displacement, acceleration, electric quantity, etc. can be applied in addition to temperature and pressure.

  (D) The sensor system of the present invention can be applied to various devices and systems in which the detection unit 10 side circulates with respect to the reading device 20 and communication is repeated in addition to the vehicle tire 1 and the conveyor 50.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram of the sensor system which shows Example 1 of this invention. It is a perspective view which shows the tire of the vehicle to which the sensor system of FIG. 1 is applied. FIG. 2 is a circuit diagram illustrating a configuration example of a temperature detection sensor element 11A, a temperature detection circuit 12A, and a temperature control circuit 14A in FIG. FIG. 2 is a circuit diagram illustrating a configuration example of a pressure detection sensor element 11B, a pressure detection circuit 12B, and a pressure control circuit 14B in FIG. It is a time chart which shows operation | movement of the transmission and correction method of the detection data of FIG. It is a characteristic view of the detection data when not correct | amending by the present Example 1. FIG. FIG. 6 is a characteristic diagram of detection data after offset adjustment and full scale adjustment according to the first embodiment. FIG. 6 is a characteristic diagram of correction data according to the first embodiment. FIG. 6 is a characteristic diagram of detection data after correction by offset adjustment, full scale adjustment, and correction data according to the first embodiment. It is a schematic perspective view which shows the other application example of the sensor system which shows Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 10 Detection unit 11, 11A, 11B Sensor element 12, 12A, 12B Detection circuit 13 Memory 14, 14A, 14B, 27 Control circuit 15 Rectification circuit 16, 25 Reception circuit 17, 24 Transmission circuit 18 Antenna coil 20 Reading device 21 Loop antenna 50 conveyor

Claims (6)

A detection unit mounted on a moving detection object;
A reader that is installed apart from the detection unit, is non-contact with the detection unit, transmits a signal on which power is superimposed, and receives the signal from the detection unit; A sensor system,
The detection unit is
First receiving means for receiving the signal on which the power supply power is superimposed;
Power supply means for extracting the power supply power from the signal received by the first receiving means and supplying it to an internal circuit of the detection unit;
A sensor element whose electrical characteristic value changes in response to a change in a physical quantity in the detection object;
A reference element having an electrical characteristic value different from that of the sensor element with respect to a change in the physical quantity;
A first oscillation circuit that oscillates at a frequency determined based on an electrical characteristic value of the sensor element;
A second oscillation circuit that oscillates at a frequency determined based on an electrical characteristic value of the reference element;
A detection circuit for obtaining a relative frequency change of the first and second oscillation circuits to detect a change in the physical quantity and outputting detection data;
Data storage means storing correction data for correcting the electrical characteristic value of the sensor element;
First detection means for transmitting the detection data and the correction data in the data storage means to the reading device;
The reader is
Second transmission means for transmitting the signal on which the power source power is superimposed to the detection unit;
Second receiving means for receiving the detection data and the correction data sent from the detection unit;
Calculating means for obtaining corrected detection data by performing correction calculation of the correction data received by the second receiving means on the detection data received by the second receiving means; Sensor system.   The sensor system according to claim 1, wherein the detection unit and the reading device exchange signals by non-contact magnetic field coupling.   3. The sensor system according to claim 1, wherein the detection unit mounted on the detection object is circulated with respect to the reading device and communication is repeated. 4.   The sensor system according to any one of claims 1 to 3, wherein the first and second oscillation circuits are configured by one common oscillation circuit that is switched and used by a switching unit.   The sensor system according to claim 1, wherein the reference element is configured by an element having a constant electrical characteristic value with respect to a change in the physical quantity.   The sensor system according to claim 1, wherein the physical quantity includes temperature, pressure, stress, displacement, acceleration, and electric quantity.

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