JP2008267862A - Gas pressure in tire measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce size, number of parts items, weight and power consumption of a gas pressure in tire measuring device having a pressure sensor for measuring gas pressure in tire and a transmitting circuit for transmitting data to the outside of the tire with utilizing radio. <P>SOLUTION: A gas pressure in tire measuring device includes one integrated circuit chip of a pressure detecting circuit and an acceleration detecting circuit for measuring acceleration caused by tire movement. Both of a pressure detecting means of the pressure detecting circuit and an acceleration detecting means of the acceleration detecting circuit are due to the capacitance of a movable electrode and a fixed electrode, and the capacitance detected by the pressure detecting means and the capacitance detected by the acceleration detecting means are converted to voltage by a capacitance-voltage converting circuit. The capacitance-voltage converting circuit in the pressure detecting circuit and the acceleration detecting circuit converts the capacitance into the voltage with clock signals for driving input from the outside of the integrated circuit chip to one common terminal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a gas pressure measuring device in a tire that measures the gas pressure inside a tire used in an automobile or the like.

  In recent years, attention has been focused on a system that measures a gas pressure inside a tire used in an automobile and notifies a warning when the pressure decreases. The reason why this system is attracting attention is that the gas pressure in the tire needs to be kept at around 220 kPa at room temperature if it is a passenger car. However, if the gas pressure in the tire decreases, the ride comfort and fuel consumption only deteriorate. This is because, depending on the conditions, the tire may burst. In addition, in the United States, it is obliged to install a system for monitoring the gas pressure in tires in automobiles due to laws and regulations.

  By the way, the tire pressure measurement module is installed in a tire which is a rotating body. For this reason, it is difficult to receive power supply from the outside, and thus batteries are often built in. However, although the amount of power that can be supplied by the battery is limited, since automobiles are used for a long period of time (for example, 10 years), low power consumption is indispensable for the tire pressure measurement module.

  Further, in order to reduce the disruption of the wheel balance caused by mounting the tire pressure measurement module on the tire, it is essential to reduce the weight and size of the tire pressure measurement module. As this tire pressure measuring module, for example, a tire pressure measuring module described in Patent Document 1 (Japanese Patent Laid-Open No. 11-20247) and Patent Document 2 (Japanese Patent Laid-Open No. 11-326099) is known.

  What is described in Patent Document 1 includes a tire pressure measuring device that includes an air pressure sensor, a centrifugal force switch that responds to wheel rotation, and a wireless transmission device having a control unit and a transmission unit. When the force switch is turned on and the vehicle is in a running state, the air pressure sensor is periodically operated to detect the tire air pressure, and the transmitter is operated to wirelessly transmit a signal indicating the tire air pressure from the wheel side to the vehicle body side. Sending. In addition, the tire pressure alarm device described in Patent Document 2 is a timer circuit or a forced output means that outputs a signal at regular intervals by setting a control unit having a low current consumption mode to a low current consumption mode normally. The control unit cancels the low-current-consumption mode of the control unit according to the output of the control unit to enter the normal operation mode, supplies power to the tire air pressure abnormality detecting means, and controls the tire air pressure abnormality detecting means to check the tire air pressure abnormality. Yes.

Japanese Patent Laid-Open No. 11-20247 JP 11-326099 A

  In the tire pressure measuring device described in Patent Document 1, power consumption can be reduced by periodically operating the air pressure sensor when the vehicle is in a running state by a centrifugal force switch. However, since it is necessary to provide a centrifugal force switch separately from the air pressure sensor, the tire pressure measuring device is increased in size. In the tire air pressure alarm device described in Patent Document 2, the configuration of the tire air pressure abnormality detecting means is not clear, no consideration is given to downsizing the tire air pressure alarm device, and a signal input to the forced output means May be input at unspecified timing, and it is necessary to always operate the circuit of the forced output means, so that power is always consumed.

  The present invention has been made for the purpose of solving the above-mentioned problems, and the pressure detection circuit and the acceleration detection circuit are integrated into one integrated circuit chip to reduce the number of parts and reduce the size. The object is to provide a tire pressure measuring device that is light in weight and low in power consumption.

  In order to achieve the above object, a gas pressure measuring device in a tire according to the present invention comprises a pressure detection circuit for measuring the gas pressure in the tire and an acceleration detection circuit for measuring acceleration due to the movement of the tire on a single chip. It is characterized by comprising an integrated circuit chip formed on a substrate. In the present invention, since the pressure detection circuit and the acceleration detection circuit are formed of an integrated circuit chip formed on a single chip semiconductor substrate, the pressure detection circuit and the acceleration detection circuit necessary for measuring the gas pressure in the tire. Can be reduced in size by reducing the number of parts, and the weight can be reduced and power can be saved.

  In the tire pressure measuring apparatus in the present invention, specifically, the integrated circuit chip includes a capacitance-voltage conversion circuit, the pressure detection circuit detects the gas pressure by the capacitance between the movable electrode and the fixed electrode, and the acceleration. The detection circuit detects acceleration by the capacitance of the movable electrode and the fixed electrode, and converts the capacitance detected by the pressure detection circuit and the capacitance detected by the acceleration detection circuit into a voltage by the capacitance-voltage conversion circuit. Thus, the pressure in the tire and the rotation of the tire are detected.

  In the gas pressure measuring device for a tire in the present invention, the integrated circuit chip has one clock signal input terminal from the outside of the integrated circuit chip, and each of the pressure detection circuit and the acceleration detection circuit has a capacity voltage conversion circuit. In addition, a driving clock signal for each of the capacitance voltage conversion circuits is input from the clock signal input terminal. In the present invention, the configuration is such that the driving clock signal is input from one clock signal input terminal to each capacitance voltage conversion circuit, so that the number of clock signal input terminals can be reduced, and the integrated circuit chip can be downsized. As a result, the gas pressure measuring device can be miniaturized.

  An apparatus for measuring gas pressure in a tire according to the present invention includes a pressure detection capacitive element that converts a gas pressure in a tire into a capacitance value, an acceleration detection capacitive element that converts acceleration due to tire movement into a capacitance value, and a capacitance. A capacitance-voltage conversion circuit that converts the voltage into a voltage, and the capacitance-voltage conversion circuit is configured to be connected to a pressure detection capacitance element or an acceleration detection capacitance element by a changeover switch. The pressure detection circuit is configured to be connected to the acceleration detection capacitor, and the acceleration detection circuit is configured to be connected to the acceleration detection capacitance element. According to the present invention, the integrated circuit chip can be further reduced in size by configuring the capacitance-voltage conversion circuit so as to be used both as the pressure detection capacitance element and the acceleration detection capacitance element.

  In the tire gas pressure measuring device according to the present invention, preferably, a temperature detection circuit for measuring the temperature in the tire is arranged on the integrated circuit chip, and further, a constant voltage output circuit is arranged. In the present invention, by correcting the pressure in the tire based on the temperature in the tire, the pressure at normal temperature can be known, and the remaining amount of the battery disposed in the tire can be known.

  In the gas pressure measuring apparatus for a tire in the present invention, a control circuit having a control input terminal to which a pulse signal is input is disposed on an integrated circuit chip, and a pressure detection circuit, an acceleration detection circuit, a temperature detection circuit, and a constant detection circuit are arranged. The voltage output circuit includes means for switching between operation and non-operation corresponding to the count number of the pulse signal from the control circuit. In the present invention, a pulse signal is input from the control input terminal of the control circuit arranged on the integrated circuit chip, and the pulse signal is output from the control circuit to the pressure detection circuit, acceleration detection circuit, temperature detection circuit, and constant voltage output circuit. Therefore, the input terminals of the integrated circuit chip can be reduced, and the gas pressure measuring device can be miniaturized.

  In the tire gas pressure measuring device according to the present invention, an output circuit having a first output terminal is disposed on an integrated circuit chip, and the output circuit has switching means for switching to an operating circuit, and operates. An output voltage from the above circuit is output from a first output terminal. In the present invention, the output circuit arranged on the integrated circuit chip is connected to a circuit such as a pressure detection circuit and an acceleration detection circuit which are operating by the switching means, and is connected to the circuit operating from the first output terminal of the output circuit. Since it is comprised so that an output voltage may be output, an output terminal can be decreased and a gas pressure measuring device can be reduced in size.

  In the tire gas pressure measuring device according to the present invention, specifically, the integrated circuit chip has a second output terminal and a third output terminal, and also has a receiving terminal, and the integrated circuit chip is provided from the second output terminal. An operation signal is output to a radio transmission circuit provided outside the circuit, and an operation signal is output from the third output terminal to a radio reception circuit provided outside the integrated circuit chip. A reception signal output from the circuit is input from the reception terminal and output from the first output terminal.

  In the gas pressure measuring device in a tire according to the present invention, the integrated circuit chip has means for outputting a predetermined voltage from the first output terminal corresponding to the count number of the pulse signal input to the control input terminal. Specifically, a power supply voltage or a GND voltage is output as a predetermined voltage. In the present invention, by confirming that the power supply voltage or the GND voltage is output, it is possible to confirm whether or not the control pulse signal output from the microcomputer has been normally received by the integrated circuit chip.

  The apparatus for measuring gas pressure in a tire according to the present invention includes means for stopping pressure measurement by the pressure detection circuit when the acceleration measured by the acceleration detection circuit is equal to or less than a predetermined threshold. In the present invention, when the tire is not rotating, that is, when the vehicle is stopped, the pressure measurement by the pressure detection circuit is stopped, so that it is possible to measure the pressure in the tire for a long time with less battery consumption. .

  The device for measuring gas pressure in a tire according to the present invention has means for outputting a signal at predetermined time intervals, and the acceleration detection circuit measures acceleration based on a signal from the means. In the present invention, since the acceleration detection circuit measures the rotation speed of the tire at predetermined time intervals, the power for measuring the gas pressure in the tire can be saved, and battery consumption can be further reduced.

  According to the present invention, since the pressure detection circuit and the acceleration detection circuit are integrated into one integrated circuit chip, the number of components can be reduced, the size can be reduced, and the weight can be reduced.

  Hereinafter, the configuration and operation of the gas pressure monitoring system in the tire according to the first embodiment will be described with reference to FIGS. 1 to 9.

  First, the overall configuration of the gas pressure monitoring system in the tire according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a block diagram of a gas pressure measuring device 1 in a tire, and FIG. 2 is a block diagram of a vehicle-mounted machine 800. FIG. 3 shows the configuration of the gas pressure monitoring system in the tire as seen from the bottom of the vehicle. The interior of each of the vehicle 700, tires 701a to 701d and tires 701a to 701d arranged on the front, rear, left and right sides. The gas pressure measuring devices 1a to 1d in the tire installed in the vehicle and the vehicle-mounted machine 800 are configured.

In FIG. 1, the gas pressure measuring device 1 in the tire is broadly divided into a sensor chip 2, a microcomputer 12, a transmission circuit 13, a receiving circuit 11, and a voltage V _BAT for supplying power to the entire gas pressure measuring device 1 in the tire. Battery 10.

The sensor chip 2 includes a pressure detection circuit 3 that measures the gas pressure in the tire, an acceleration detection circuit 4 that detects whether the tire is rotating by centrifugal force, a temperature detection circuit 5 that measures temperature, and a voltage V _BAT that changes. Even so, it is composed of a constant voltage output circuit 6 that outputs a constant voltage, a control circuit 7, and a multiplexer 9, and functions as a gas pressure measuring device. The sensor chip 2 is configured as an integrated circuit chip in which the pressure detection circuit 3, acceleration detection circuit 4, temperature detection circuit 5, constant voltage output circuit 6, control circuit 7, multiplexer 9 and the like are formed on a single chip semiconductor substrate. Has been.

  The control circuit 7 in the sensor chip 2 has a control pulse input terminal 24 that is a control input terminal, and a pulse signal is input from the digital output terminal 122 of the microcomputer 12 to the control pulse input terminal 24. The control circuit 7 outputs an ON / OFF signal via the control lines 31, 41, 51, 61, 81 according to the count number of the pulse signal, and switches the switch to the multiplexer 9 via the control line 98. Output a signal. The pressure detection circuit 3, the acceleration detection circuit 4, the temperature detection circuit 5, the constant voltage output circuit 6 and the comparator 8 in the sensor chip 2 can be controlled to be turned on / off by an ON / OFF signal from the control circuit 7. It has become. Further, the control circuit 7 receives the ON / OFF signal output via the control lines 71 and 81, the output terminal (third output terminal) 21 and the output terminal (second output terminal) 25, and receives the signal from the outside of the sensor chip 2. 11 and the transmission circuit 13 can be turned on and off. Further, the control circuit 7 can be reset by a pulse input from the digital output terminal 121 of the microcomputer 12 to the reset signal input terminal 23.

  The pressure detection circuit 3 includes a pressure detection capacitance element 32, a comparative fixed capacitance 33, and a capacitance-voltage conversion circuit 34. The capacitance value detected by the pressure detection capacitance element 32 is a capacitance-voltage conversion circuit. At 34, the voltage is converted. The acceleration detection circuit 4 includes an acceleration detection capacitance element 42, a comparative fixed capacitance 43, and a capacitance-voltage conversion circuit 44. The capacitance value detected by the acceleration detection capacitance element 42 is a capacitance-voltage conversion circuit. In 44, it is converted into a voltage. The capacitance-voltage conversion circuits 34 and 44 are driven by a pulse signal (drive clock signal) input from the digital output terminal 123 of the microcomputer 12 to the clock signal input terminal 26.

  Further, the 6-input 1-output multiplexer 9 functions as an output circuit, and output signals from the pressure detection circuit 3, the acceleration detection circuit 4, the temperature detection circuit 5, the constant voltage output circuit 6, the control circuit 7 and the comparator 8 are The signals are input to six input terminals via signal lines 35, 45, 55, 65, 75 and 85. The multiplexer 9 is configured such that a switch as a switching means is switched by a signal input from the control circuit 7 via the control line 98, and an output signal input from the circuit or the like is a multiplexer serving as a first output terminal. Output from the output terminal 27. The sensor chip 2 is provided with a comparator 8, and the voltage output from the reception intensity output terminal 112 of the reception circuit 11 outside the sensor chip 2 is input to the comparator 8 having the comparison voltage 82 via the comparator input terminal 22. The configuration is as follows.

  The microcomputer 12 is a calculation processing / control device that performs input / output and calculation of data from / to the outside according to a predetermined program. The microcomputer 12 has digital output terminals 121 to 124 as output terminals and is input as an input terminal. An analog-to-digital conversion circuit input terminal 125 that converts an analog voltage value to a digital value is provided. Further, for example, it has an activation circuit 126 that outputs a pulse every 10 seconds.

  The transmission circuit 13 is a circuit that wirelessly transmits data such as measurement values corrected and calculated by the microcomputer 12 to the vehicle-mounted machine 800 shown in FIG. 2, and an ON / OFF signal that is an operation signal from the control circuit 7. An input terminal 132 is provided. The UHF band, for example, 315 MHz is used for the radio frequency of the transmission circuit 13, and communication is performed by performing ASK modulation or FSK modulation with a data signal input from the digital output terminal 124 of the microcomputer 12 to the modulation input terminal 131 with respect to the carrier wave. . On the other hand, the reception circuit 11 is a circuit that wirelessly receives data such as a control signal from the vehicle-mounted machine 800 and transmits the data to the microcomputer 12 via the sensor chip 2, and is an operation signal from the control circuit 7. An input terminal 111 for inputting an ON / OFF signal is provided. The radio frequency of the receiving circuit 11 is an LF band, for example, 125 kHz, and performs communication by performing ASK modulation on a carrier wave with transmission data. The transmission circuit 13 and the reception circuit 11 each have an antenna built therein. The battery 10 that drives the gas pressure measuring device 1 in the tire uses a coin-type lithium battery (nominal voltage 3 V).

  FIG. 2 is a block diagram of the vehicle-mounted machine 800. The vehicle-mounted machine 800 includes a calculation processing / control unit 801 that performs data input / output and calculation, a reception circuit 802, a transmission circuit 804, a reception circuit 802, and a transmission circuit 804. The antennas 803 and 805 are connected to the display unit 806 and a display unit 806 that displays measurement values and warnings. The calculation processing / control unit 801 receives data wirelessly transmitted from the gas pressure measuring device 1 in the tire shown in FIG. 1 via the receiving circuit 802, calculates based on the input data, calculates pressure values and This is a circuit that outputs a warning and warning such as a pressure drop to the display unit 806. Further, the calculation processing / control unit 801 transmits control data to the gas pressure measuring device 1 in the tire via the transmission circuit 804. Note that the electric power necessary for the operation of the vehicle-mounted machine 800 is supplied from a battery mounted on an automobile (not shown).

  FIG. 4 is a schematic view of a cross section of the pressure detection unit and the acceleration detection unit. In the present embodiment, a pressure detection capacitance element 32 and an acceleration detection capacitance element 42 using capacitance will be described as an example.

In the pressure detection capacitive element 32, a fixed electrode 324 is formed on a silicon single crystal substrate 28, and a diaphragm 321 is disposed thereon via a gap 323. A movable electrode 322 is provided in the diaphragm 321 so as to face the fixed electrode 324. A capacitance signal (electric signal) between the movable electrode 322 and the fixed electrode 324 is taken out by an aluminum wiring or the like. If the area where the movable electrode 322 and the fixed electrode 324 face each other is S, the distance of the gap between the movable electrode 322 and the fixed electrode 324 is d, and the dielectric constant in vacuum is ε ₀ , this pressure is the capacitance. The capacitance C _S of the pressure detection capacitance conversion element 32 that is converted into is expressed by (Equation 1).

Here, when pressure is applied to the diaphragm 321, the diaphragm 321 is bent, the movable electrode 322 is brought close to the fixed electrode 324, the gap d between the movable electrode 322 and the fixed electrode 324 is changed, and the capacitance _CS is changed.

The acceleration detection capacitive element 42 is formed on the same single crystal substrate 28 of silicon as the pressure detection electrostatic element 32, and a movable electrode 422 is provided so as to face the fixed electrode 425. The movable electrode 422 is arranged in a state of floating in the gap 424 through a spring 423 in the gap 424 in the cap 421. Here, when acceleration is applied to the movable electrode 422, movable electrode 422, the gap d is changed between the fixed electrode 425, the capacitance C _S is changed similarly to the pressure sensing capacitance device 32. The capacitance C _S of the acceleration detecting capacitance device 42 for converting the acceleration in the electrostatic capacitance is expressed by the equation (1).

5, the capacitance converts the capacitance value C _S of the pressure sensing capacitance device 32 into a voltage signal - has been shown the pressure detecting circuit 3 including a voltage conversion circuit 34. Here, 33 is a reference (reference) capacitive element, and its capacitance _CR is fixed. Further, 32 is a pressure sensing capacitance element shown in FIG. 4, 341 operational amplifier, 346 is a reference voltage source of the voltage _{V B2,} 345a, 345b selector switch, 348 is a zero-span adjustment circuit.

The reference capacitive element 33 is connected to the inverting input terminal of the operational amplifier 341. Further, the pressure detection capacitance element 32 is connected to a feedback circuit between the inverting input terminal and the operational amplifier output terminal. The non-inverting input terminal is set to the voltage V _B2 of the reference voltage source. That is, the voltage at the inverting input terminal is always kept at the voltage V _B2 . The switches 345a and 345b are circuit elements for charging and discharging the pressure detection capacitance element 32 and the reference capacitance element 33. The switches 345a and 345b are switched to the solid line position at the timing φ1 and switched to the broken line position at the timing φ1B. Switching of these switches 345a and 345b is controlled by a pulse signal (drive clock signal) input from the digital output terminal 123 of the microcomputer 12 to the clock signal input terminal 26.

According to this circuit configuration, at the timing φ1, the switch 345a is at the solid line position and is connected to GND, and the potential difference between the electrodes of the reference capacitive element 33 becomes V _B2 , so that the reference capacitive element 33 is charged. The On the other hand, the potential difference between the electrodes of the pressure detection capacitive element 32 becomes zero because the switch 345b is at the solid line position and is closed. At the timing φ1B, the switch 345a is at the broken line position, the potential difference between the electrodes of the reference capacitor 33 connected to the voltage _VB2 side of the reference voltage source becomes zero, and the charged charge is discharged. The discharged electric charges are all charged in the pressure detection capacitive element 32 because the switch 345b is open. By repeating these two modes, an output signal is obtained in a pulse manner at the output terminal 347.
The output V _{out at} the timing φ1B of this circuit configuration is expressed by (Equation 2).

Therefore, the pressure detection circuit 3, in proportion to the reciprocal of the capacitance C _S of the pressure sensing capacitance device 32 for converting the pressure into a capacitance, that is, the output voltage V _out proportional to the change of the gap d is changed It is configured as follows. Since the air gap d changes in proportion to the pressure P, a good linear characteristic is obtained in principle between the pressure P and the voltage output _Vout . It performs voltage conversion by performing offset adjustment and amplifies the output V _out at zero and span adjustment circuit 348 to obtain an output V _p. Here, FIG. 6 shows an example of a characteristic of the pressure P and the output voltage V _p in the pressure detection circuit 3 of FIG. The detection range of the pressure is 100～700KPa, the output voltage _{V p} becomes _{0.2V BAT ~0.8V} BAT. Note that the pressure detection range and the voltage output range are not limited to this. The acceleration detection circuit 4 will be described because the circuit including the acceleration detection capacitance element 42, the reference capacitance element 43, and the capacitance-voltage conversion circuit 44 is the same configuration circuit as the pressure detection circuit 3. Omitted.

  Next, an outline of operations in the gas pressure measuring device 1 in the tire and the vehicle-mounted machine 800 will be described with reference to FIGS. The gas pressure measuring device 1 in the tire and the vehicle-mounted machine 800 operate according to programs written in advance in respective memories (not shown) of the microcomputer 12 and the calculation processing / control unit 801.

  FIG. 7 shows an outline of signal timing in the gas pressure measuring device 1 in the tire. First, the operation of the gas pressure measuring device 1 in the tire will be described with reference to FIG. In this example, the counter in the control circuit 7 has 4 bits and is configured to make one round with 16 counts. In addition, the gas pressure measuring device 1 in the tire is normally in a sleep state in which most of the circuits are in a non-operating state, and the current consumption is the smallest.

  First, the microcomputer 12 is activated by the pulse signal output from the activation circuit 126, and the program is started. First, the microcomputer 12 outputs a falling pulse via the digital output terminal 121. In the sensor chip 2, the counter in the control circuit 7 is reset by the falling pulse input to the reset signal input terminal 23, and the counter value becomes zero.

Subsequently, a pulse is input from the microcomputer 12 to the control pulse input terminal 24 of the sensor chip 2 and counted by a counter in the control circuit 7 of the sensor chip 2. The microcomputer 12 performs an operation to check whether the control circuit 7 of the sensor chip 2 is operating normally from the first pulse to the third pulse output to the control input terminal. Specifically, the sensor chip 2 outputs the V _BAT voltage at the first count and the third count from the multiplexer output terminal 27 and the GND voltage at the second count. The V _BAT voltage and the GND voltage are input to the analog / digital conversion circuit input terminal 125 of the microcomputer 12 and are converted from analog to digital. Voltage converted in the microcomputer 12, the first pulse and the third threshold value in the pulse of (e.g. _{0.95 V BAT)} above, if a certain threshold in the second pulse (e.g., _{0.05 V BAT)} below, the control circuit 7 On the other hand, it is determined that the pulse has been normally received.

  Subsequently, the sensor chip 2 does nothing at the fourth count. The control circuit 7 operates the temperature detection circuit 5 with an ON / OFF signal via the control line 51 at the fifth count, and a voltage corresponding to the temperature output from the temperature detection circuit 5 is output from the multiplexer output terminal 27. This voltage is input to the analog / digital conversion circuit input terminal 125 of the microcomputer 12 and is converted from analog to digital.

  Next, the control circuit 7 inputs an ON / OFF signal to the acceleration detection circuit 4 via the control line 41 at the sixth count, and operates the acceleration detection circuit 4. At this time, a pulse is input to the acceleration detection circuit 4 from the microcomputer 12 to the clock signal input terminal 26, the capacitance-voltage conversion circuit 44 is driven, and the capacitance-voltage conversion circuit 44 outputs a voltage corresponding to the acceleration. A voltage corresponding to the acceleration is output from the multiplexer output terminal 27 and input to the analog / digital conversion circuit input terminal 125 of the microcomputer 12 for analog / digital conversion. Note that the number of pulses input to the clock signal input terminal 26 may be a plurality of times, and analog-digital conversion may be performed in synchronization with this pulse to obtain an integral average. Nothing is done at the 7th count.

  At the eighth count, the control circuit 7 inputs an ON / OFF signal to the pressure detection circuit 3 via the control line 31 and operates the pressure detection circuit 3. At this time, a pulse is input from the microcomputer 12 to the clock signal input terminal 26 in the pressure detection circuit 3 to drive the capacitance-voltage conversion circuit 34, and the capacitance-voltage conversion circuit 34 outputs a voltage corresponding to the pressure. A voltage corresponding to this pressure is output from the multiplexer output terminal 27 and input to the analog / digital conversion circuit input terminal 125 of the microcomputer 12 for analog-digital conversion. The number of pulses input to the clock signal input terminal 26 may be a plurality of times as in the case of the acceleration detection circuit 4, and analog-digital conversion may be performed in synchronization with this pulse to obtain an integral average.

Control circuit 7, the 9 count th operates the constant voltage output circuit 6, and outputs a constant voltage V _C which is from the multiplexer output terminal 27. The voltage V _C is analog-digital converted by the microcomputer 12. When the resolution of the analog-digital conversion circuit is set to N _res from the converted digital value N _ADC , the battery voltage V _BAT is obtained by the following (Equation 3).

  From this equation, the voltage drop, that is, the life of the battery 10 is known. Nothing is done at the 10th count. At the 11th count, the control circuit 7 outputs the ID assigned to each gas pressure measuring device 1 in the tire, the measured pressure, acceleration, temperature, digital value according to the voltage, check data, etc. to the transmission circuit 13. To the vehicle-mounted machine 800.

  Here, as shown in FIG. 8, vehicle-mounted device 800 first receives data in data reception SC1. The calculation processing / control unit 801 of the vehicle-mounted machine 800 determines whether the received ID is for a tire attached to the own vehicle, and at the same time uses the check data to determine whether the data has been normally received. Next, the process proceeds to the display / warning SC2 in FIG. 8, and the calculation processing / control unit 801 transmits a signal indicating a warning / warning to the display unit 806 in the case of a pressure measurement value signal, a pressure drop, etc. A display unit 806 displays a pressure measurement value or a caution / warning.

  Next, in the gas pressure measuring device 1 in the tire, the count value of the pulses input to the control pulse input terminal 24 shown in FIG. 7 becomes 12 counts, and data is transmitted to the receiving circuit 11 for a certain period of time. Wait (for example, 10 ms). At the same time, in the vehicle-mounted machine 800, if it is necessary to control the gas pressure measuring device 1 in the tire, the process proceeds to the data transmission SC3 shown in FIG. Is transmitted to the gas pressure measuring device 1. Note that after the control data is transmitted or when it is not necessary to transmit the control data, the process returns to the data reception mode SC1 again. Subsequently, in the gas pressure measuring device 1 in the tire, the count value of the pulses input to the control pulse input terminal 24 shown in FIG. 7 is changed from 13 counts to 15 counts, and the control circuit is the same as the first count to the third count. Check to see if it is working properly.

From the multiplexer output terminal 27, the V _BAT voltage is output at the 13th and 15th counts, and the GND voltage is output at the 14th count. The microcomputer determines whether the control pulse has been normally received as in the first to third counts. Subsequently, the count value becomes 16 counts, and the sensor chip 2 shifts to the sleep state.

  The microcomputer 12 determines whether the vehicle is running or stopped based on whether the measured value of acceleration measured by the acceleration measuring circuit 4 at the sixth count is greater than or less than a certain threshold, and the measured value of acceleration is less than a certain threshold. In this case, as shown in FIG. 9, pressure measurement by the pressure detection circuit 3 is not performed. Since the pressure measurement by the pressure detection circuit 3 is not performed while the vehicle is stopped, the power consumption of the pressure measuring device can be further reduced. This stops the input of pulses from the microcomputer 12 to the clock signal input terminal 26 for driving the capacitance-voltage conversion circuit 34 at the 8th count of the pulses input to the control pulse input terminal 24 shown in FIG. This can be realized by not performing analog-digital conversion.

  Next, the configuration and operation of the gas pressure monitoring system in the tire according to the second embodiment will be described with reference to FIGS. 10 and 11. Since the basic configuration is the same as the configuration of the first embodiment, only the different configuration will be described here.

  In the first embodiment, the pressure detection circuit 3 and the acceleration detection circuit 4 have capacitance-voltage conversion circuits 34 and 44, respectively, as shown in FIG. As shown in FIG. 10, the pressure / acceleration detection circuit 91 is configured by combining the capacitance-voltage conversion circuit of the pressure detection unit 30 and the acceleration detection unit 40 with one capacitance-voltage conversion circuit 92. As in the first embodiment, an ON / OFF signal is input to the capacitance-voltage conversion circuit 92 from the control circuit 7 via the control line 93 to control ON / OFF of the power supply of the capacitance-voltage conversion circuit 92. Is done. In addition, a control line 94 for switching between pressure detection by the pressure detection capacitance element 32 and acceleration detection operation by the acceleration detection capacitance element 42 is added. A voltage signal corresponding to the pressure and acceleration from the capacitance-voltage conversion circuit 92 is output to the signal line 95 and input to the multiplexer 9. The multiplexer 9 is changed to 5 inputs and 1 output. In the present embodiment, since the capacitance-voltage conversion circuit of the pressure detection unit 30 and the acceleration detection unit 40 is shared by one capacitance-voltage conversion circuit 92, the sensor chip 2 can be reduced in size.

  FIG. 11 shows a specific circuit configuration of the pressure / acceleration detection circuit 91 according to the second embodiment. A reference capacitance 33 for the pressure detection capacitance element 32 and a reference capacitance 43 for the acceleration detection capacitance element 42 are connected in parallel to the inverting input terminal of the operational amplifier 341. The reference capacitance 33 and the reference capacitance 43 are changeover switches. It is configured to be connected to a power source through 96a. In addition, the pressure detection capacitance element 32 and the acceleration detection capacitance element 42 are provided in parallel in the feedback circuit between the inverting input terminal and the output terminal 347 of the operational amplifier 341, and the pressure detection capacitance element 32 and the acceleration detecting capacitance element 42 are configured to be connected to the output terminal 347 via the changeover switch 96b.

  The changeover switch 96a and the changeover switch 96b are switched by a signal from the control line 94. When the changeover switch 96a is connected to the reference capacitor 33 and the changeover switch 96b is connected to the pressure detection capacitance element 32, A detection circuit is configured, and a voltage corresponding to the pressure detected by the pressure detection capacitance element 32 is output from the capacitance-voltage conversion circuit 92.

  When the changeover switch 96a is connected to the reference capacitor 43 and the changeover switch 96b is connected to the acceleration detection capacitance element 42, an acceleration detection circuit is configured and detected by the acceleration detection capacitance element 42. Then, a voltage corresponding to the acceleration is output from the capacitance-voltage conversion circuit 92.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to the said embodiment, Unless each characteristic function of this invention is impaired, each component is limited to the said structure. It is not a thing.

  In the above-described embodiment, the startup circuit 126 is built in the microcomputer 2, but the startup circuit 126 is not necessarily built in the microcomputer 2, and may be provided outside. For example, as shown in FIG. 12, the activation circuit 35 is mounted on the sensor chip 2 and the pulse output output from the reset signal output terminal 29 is input to the reset signal input terminal 127 of the microcomputer 12 to be activated. good. At this time, the control circuit 7 in the sensor chip 2 may be reset using a pulse signal output from the activation circuit 35.

1 is a block diagram of a tire pressure measurement module according to a first embodiment of the present invention. The block diagram of a vehicle mounting machine. The figure which shows the structure of the gas pressure monitoring system in the tire seen from the vehicle bottom face of a motor vehicle. The schematic of the cross section of the pressure detection capacitive element and acceleration detection capacitive element which concern on 1st Example of this invention. The figure which shows the structure of the pressure detection circuit containing the capacitance-voltage conversion circuit which converts the electrostatic capacitance value _CS into a voltage signal. Diagram showing an example of the characteristics of the pressure P and the output V _p in the circuit configuration of FIG. The figure which shows the outline of the timing of the signal in the tire pressure measurement module in connection with the 1st Embodiment of this invention. The figure which shows the outline of one part operation | movement in a vehicle mounting machine. The figure which shows the outline of a one part operation | movement in the tire-pressure measurement module in the 1st Embodiment of this invention. The block diagram of the tire pressure measurement module in the 2nd Embodiment of this invention. The figure which shows the structure of the pressure detection circuit and acceleration detection circuit containing the capacitance-voltage conversion circuit which converts the electrostatic capacitance value CS in the 2nd Embodiment of this invention into a voltage signal. The block diagram which shows the modification of the tire pressure measurement module of this invention.

Explanation of symbols

1, 1a, 1b, 1c, 1d Tire pressure measurement module 2 Sensor chip 3 Pressure detection circuit 4 Acceleration detection circuit 5 Temperature detection circuit 6 Constant voltage output circuit 7 Control circuit 8 Comparator 9 Multiplexer 10 Battery 11 Reception circuit 12 Microcomputer 13 Transmission circuit 700 Vehicle 701a-d Tire 800 Vehicle mounted machine

Claims (18)

  A gas in a tire comprising an integrated circuit chip formed on a single-chip semiconductor substrate, and a pressure detection circuit for measuring a gas pressure in the tire and an acceleration detection circuit for measuring an acceleration due to tire movement Pressure measuring device.   The gas pressure measuring device in a tire according to claim 1, wherein the integrated circuit chip includes a capacitance-voltage conversion circuit, the pressure detection circuit detects a gas pressure by a capacitance of a movable electrode and a fixed electrode, and The acceleration detection circuit detects acceleration by the capacitance of the movable electrode and the fixed electrode, and converts the capacitance detected by the pressure detection circuit and the capacitance detected by the acceleration detection circuit into a voltage by the capacitance voltage conversion circuit. An apparatus for measuring a gas pressure in a tire, characterized in that:   3. The apparatus for measuring gas pressure in a tire according to claim 2, wherein the integrated circuit chip has one clock signal input terminal from the outside of the integrated circuit chip, and each of the pressure detection circuit and the acceleration detection circuit includes: An apparatus for measuring a gas pressure in a tire, comprising the capacitance voltage conversion circuit, wherein a driving clock signal for each capacitance voltage conversion circuit is input from the clock signal input terminal.   A pressure detection capacitive element that converts gas pressure in the tire into a capacitance value, an acceleration detection capacitive element that converts acceleration due to tire movement into a capacitance value, and a capacitance-voltage conversion circuit that converts capacitance into voltage, The capacitance voltage conversion circuit is configured to be connected to a pressure detection capacitance element or an acceleration detection capacitance element by a changeover switch, and the capacitance voltage conversion circuit becomes a pressure detection circuit by being connected to the pressure detection capacitance element, and an acceleration An apparatus for measuring a gas pressure in a tire, which is configured to be an acceleration detection circuit by being connected to a detection capacitor element.   5. The apparatus for measuring a gas pressure in a tire according to claim 4, wherein the pressure detection capacitive element, the acceleration detection capacitive element, and the capacitive voltage conversion circuit are configured by an integrated circuit chip formed on a one-chip semiconductor substrate. An apparatus for measuring a gas pressure in a tire, wherein:   6. The gas pressure measuring device in a tire according to claim 1 or 5, wherein a temperature detection circuit for measuring the temperature in the tire is arranged on the integrated circuit chip. .   The gas pressure measuring device in a tire according to claim 1, wherein a constant voltage output circuit is disposed on the integrated circuit chip.   6. The apparatus for measuring a gas pressure in a tire according to claim 1 or 5, wherein a control circuit having a control input terminal to which a pulse signal is input is disposed on the integrated circuit chip, and the pressure detection circuit and acceleration detection are arranged. The circuit has a means for switching between operation and non-operation corresponding to the count number of pulse signals from the control circuit.   The apparatus for measuring a gas pressure in a tire according to claim 6, wherein a control circuit having a control input terminal to which a pulse signal is input is disposed on the integrated circuit chip, and the pressure detection circuit, the acceleration detection circuit, and The temperature detection circuit includes means for switching between operation and non-operation corresponding to the number of counts of pulse signals from the control circuit.   In the gas pressure measuring device in a tire according to claim 7, a control circuit having a control input terminal to which a pulse signal is input is disposed on the integrated circuit chip, and the pressure detection circuit, the acceleration detection circuit, The temperature detection circuit and the constant voltage output circuit have means for switching between operation and non-operation according to the count number of pulse signals from the control circuit.   The gas pressure measuring device in a tire according to any one of claims 8 to 10, wherein an output circuit having a first output terminal is disposed on the integrated circuit chip, and the output circuit is in operation. A gas pressure measuring device in a tire having switching means for switching to a circuit and outputting an output voltage from the circuit in operation from a first output terminal.   11. The device for measuring a gas pressure in a tire according to claim 8, wherein the integrated circuit chip has a second output terminal, and is provided outside the integrated circuit chip from the second output terminal. An apparatus for measuring a gas pressure in a tire, which outputs an operation signal to a circuit for wireless transmission.   The gas pressure measuring device in a tire according to any one of claims 8 to 10, wherein the integrated circuit chip has a third output terminal and is provided outside the integrated circuit chip from the third output terminal. An apparatus for measuring a gas pressure in a tire, which outputs an operation signal to a wireless reception circuit.   The gas pressure measuring device in a tire according to claim 11, wherein the integrated circuit chip has a third output terminal and a receiving terminal, and the control circuit is connected to the integrated circuit chip from the third output terminal. An operation signal is output to a radio receiving circuit provided outside, and a gas pressure in the tire is input from the reception terminal and output from the first output terminal. measuring device.   The tire pressure measuring apparatus according to claim 11, wherein the integrated circuit chip outputs a predetermined voltage from the first output terminal in accordance with a count number of a pulse signal input to the control input terminal. An apparatus for measuring a gas pressure in a tire, characterized by comprising:   The gas pressure measuring device in a tire according to claim 15, wherein the predetermined voltage is a power supply voltage or a GND voltage.   5. The apparatus for measuring gas pressure in a tire according to claim 1 or 4, further comprising means for canceling pressure measurement by the pressure degree detection circuit when the acceleration measured by the acceleration detection circuit is equal to or less than a predetermined threshold value. A gas pressure measuring device in a tire characterized by the above.   18. The tire pressure measuring apparatus according to claim 17, further comprising means for outputting a signal at predetermined time intervals, wherein the acceleration detection circuit measures acceleration based on a signal from the means. A device for measuring gas pressure in tires.

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