Temperature measuring device

This temperature measuring device includes: a case which has a bottomed tubular shape with a closed portion at one end and an opening at the other end, and in which a temperature sensing part is disposed on the side of the closed portion; an infrared temperature sensor unit in which an infrared temperature detection unit that has a light-receiving surface receiving an infrared ray and detects the received infrared ray and outputs the ray in the form of an electrical signal is disposed opposite the temperature sensing part while being spaced therefrom inside the case; and a connection terminal unit which has in the interior thereof a circuit unit that acquires the electrical signal and that generates temperature information so that the temperature information is outputted to an external device, wherein the connection terminal unit can be disposed at a position spaced from the heat source.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a temperature measuring device that utilizes an infrared temperature sensor that measures temperature, for instance, a temperature measuring device used for measurement of exhaust air temperature of an internal combustion engine.

2. Description of the Related Art

So-called exhaust temperature sensors are conventionally known in which the temperature of exhaust gas flowing through an exhaust gas passage such as an exhaust pipe of the interior of a catalytic converter of a purification device in an automobile, is detected by a thermistor element being a temperature sensing element.

In a temperature sensor of this kind, a thermistor element is provided at the tip of a wiring member for extracting signals to the exterior, the tip portion being covered with a metal case having a bottomed tubular shape. The thermistor element is accommodated within the space formed by the metal case and the tip portion of the wiring member.

Further, the interior of an outer tube made of metal is packed with an insulating powder, between the outer tube and core wires, as a result of which the core wires are held insulated from the outer tube. A coupler for electrical connection to the exterior is provided, in a pair of lead wires, at a portion on the end of the lead wires opposite that of a connection portion with the core wires.

In temperature detection by such a temperature sensor, exhaust gas heat from exhaust gas is received by the metal case, and is thereafter transferred from the metal case to the thermistor element (for instance, Japanese Patent Application Publication No. 2000-171308).

As a further temperature detection method, so-called infrared temperature measuring devices are also known in which temperature is detected by an infrared temperature detection unit, being a temperature sensing element, in a state where the detection unit is spaced from a heat source. In a temperature measuring device of this type temperature is detected by detection of infrared light from a temperature sensing part, in the form of the tip section of a tubular member, by an infrared sensor element being a temperature sensing element that is disposed spaced from the temperature sensing part.

In such an infrared temperature measuring device the temperature sensing part is disposed spaced from an infrared temperature detection means, and it is the tubular member that is disposed directly within the high-temperature exhaust gas. Accordingly, it becomes possible to avoid exposure of the infrared temperature detection unit to the high-temperature exhaust gas, and to suppress thermal degradation of the infrared temperature detection unit. Further, the temperature sensing part can be formed having a thin wall. A fast thermal response can be achieved as a result (for instance, Japanese Patent No. 5828033).

As a further temperature detection method, systems are known where, in an internal EGR control device of an internal combustion engine, a target internal EGR amount is corrected in accordance with the temperature of exhaust gas as detected by an exhaust temperature sensor and the pressure of exhaust gas as detected by an exhaust pressure sensor, the sensors being disposed inside an exhaust pipe.

The internal EGR control device controls an intake-exhaust valve timing varying mechanism and a lift mechanism, and controls an internal EGR amount by modification of a degree of valve overlap between an intake valve and an exhaust valve.

Further, the internal EGR control device corrects the targeted internal EGR amount in accordance with the temperature and pressure of the exhaust gas. The internal EGR control device allows controlling more properly the internal EGR amount, by compensating thus control errors derived from changes in temperature and pressure (for instance, Japanese Patent No. 4583354).

SUMMARY OF THE INVENTION

However, conventional technologies have the following problems.

In a temperature measuring device attached to an exhaust pipe, for measuring exhaust gas temperature, an infrared temperature detection unit being a temperature sensing element disposed spaced from a heat source is ordinarily made up of a material having heat resistance at 200° C. or higher. Accordingly, the device can be used in the temperature environment in which the exhaust pipe is attached.

A circuit unit that amplifies signals from the infrared temperature detection unit, however, must be used ordinarily at or below 150° C., on account of constraints such as semiconductor junction temperature. Therefore, measures must be taken, relying on constituent parts surrounding the circuit unit, with a view to reducing the thermal impact from the heat source.

Specific measures include the use of a metallic material having heat conduction, for instance aluminum alloys, stainless steel or brass, in a holder and peripheral members of the circuit unit. Other concrete measures that are taken include lowering of the temperature of the circuit unit by shaping the constituent parts that surround the circuit unit so as to secure as large a heat-dissipating surface area as possible.

Expensive materials must be selected in order to implement such measures, while the complex shapes involved make reductions in size difficult. All the above translates into higher component costs, which is problematic.

Tubing, harnesses and connectors must be disposed in an environment in which sufficient space cannot be secured, in internal EGR control devices in which an exhaust temperature sensor and an exhaust pressure sensor are disposed in an exhaust pipe. It is thus difficult to secure space for attachment of the exhaust temperature sensor and the exhaust pressure sensor.

When a sensor is disposed in an exhaust pipe, moreover, high-temperature heat from the exhaust pipe is transferred to the circuit unit of the sensor. Measures must therefore be taken, for instance by arranging the sensor spaced from the exhaust pipe, in order to reduce thermal impact from the exhaust pipe.

Specifically, a harness must be extended, and in some instances, moreover, a pressure guiding tube for introducing pressure of the exhaust gas into the exhaust pressure sensor must be laid, and components for fixing the sensor and/or the harness may be required. Component costs increase accordingly, which is problematic.

It is an object of the present invention, arrived at in order to solve the above problems, to provide a temperature measuring device that is less expensive and more precise than conventional devices.

The temperature measuring device according to the present invention includes: a case which has a bottomed tubular shape with a closed portion at one end and an opening at the other end, and in which a temperature sensing part that receives heat by being in direct contact with a heat source is disposed on the side of the closed portion; an infrared temperature sensor unit in which an infrared temperature detection unit that has a light-receiving surface receiving an infrared ray and detects the received infrared ray and outputs the ray in the form of an electrical signal is disposed opposite the temperature sensing part while being spaced therefrom inside the case; and a connection terminal unit which has in the interior thereof a circuit unit that acquires the electrical signal, which is the output from the infrared temperature sensor unit, via connection wiring connected to the infrared temperature sensor unit and that implements signal processing on the electrical signal to correct a temperature characteristic, in order to generate temperature information so that the temperature information is outputted to an external device, wherein the connection terminal unit having the circuit unit in the interior thereof can be disposed at a position spaced from the heat source.

By virtue of the effect of thermal impact reduction elicited by a configuration in which a circuit unit is disposed spaced from a heat source, in the present invention the periphery of a circuit unit can be configured out of inexpensive materials, with reductions in changes in the temperature characteristic of the electronic components that make up the circuit unit. As a result, a temperature measuring device can be provided that is less expensive and more precise than conventional devices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the temperature measuring device of the present invention will be explained next with reference to accompanying drawings.

FIG. 1is a cross-sectional diagram illustrating a temperature measuring device of Embodiment 1 of the present invention, in a state where the device is attached to an exhaust pipe. As illustrated inFIG. 1, a temperature measuring device1aof the present Embodiment 1 absorbs infrared energy in the form of heat, and outputs temperature information on the basis of a rise in temperature derived from the absorbed heat. The temperature measuring device1ais provided with a tubular portion2aand an infrared temperature sensor unit4a.

The tubular portion2ais made up of a metal having heat resistance, for instance stainless steel. The tubular portion2ais formed as a bottomed cylinder having a closed portion at one end and an opening at the other end. The tubular portion2ahaving such a shape is formed, for instance, by pressing of a plate material and/or cold forging of a wire material.

A temperature sensing part3is formed in a part of the tubular portion2a,specifically on the closed portion side. The temperature sensing part3comes in direct contact with a heat source, and absorbs heat therefrom.

A thin wall portion being the temperature sensing part3of the tubular portion2ais formed integrally with the tubular portion, but may be formed separately from the tubular portion. To form the thin wall portion separately, a member formed spaced from the thin wall is joined, by welding, brazing, bonding or the like, to one end of the tubular portion. A material having better heat conduction than the tubular portion is selected as the material of the separate member, to enable thereby a better thermal response of the temperature sensing part.

Austenitic stainless steel such as SUS 310S, SUS 304 or SUS 316, having excellent heat resistance, can be used as stainless steel, being an example of the forming material of the tubular portion2a.Alternatively, a material having high heat resistance, for instance a zirconia-based ceramic material of low thermal conductivity may be used instead of austenitic stainless steel. In order to improve the thermal response, the tubular portion2ashould be formed to be as thin-walled as possible, so long as no problems in terms of strength are incurred in doing so.

Next, for instance a material such as an aluminum alloy, stainless steel or brass is used as a metallic material having good heat conduction in a nipple5a,which is formed as a substantially tubular portion. The nipple5ahas, on the outer peripheral surface thereof, a male thread portion6, and has a hexagonal nut7at one end. The nipple5ais rotatably fitted to the outer periphery of the tubular portion2a.

A hole for attachment of the temperature measuring device1ais formed in an exhaust pipe50a.The male thread portion6is assembled onto a female thread portion formed in a part of the hole, as a result of which the temperature measuring device1abecomes fixed to the exhaust pipe50a.

FIG. 2is a cross-sectional diagram illustrating the infrared temperature sensor unit of the temperature measuring device of Embodiment 1 of the present invention. As illustrated inFIG. 2, the infrared temperature sensor unit4ais made up of a thermopile element13as a sensing element that detects an infrared ray, a heat-sensitive resistive element14as a sensing element for temperature compensation, a substrate40on which the sensing elements13,14are fixed, for connection to the exterior, and a cap41in which a lens is assembled onto a light guide of the thermopile element13.

The infrared temperature sensor unit4a,configured such that the sensing elements13,14are accommodated therein, is disposed at the opening side of the tubular portion2a,and is fixed to the tubular portion2aso that the infrared temperature sensor unit4aopposes the temperature sensing part3while being spaced from the temperature sensing part3.

The thermopile element13is made up of a thermocouple formed on a board that is mounted on the substrate40. The thermopile element13outputs, as output voltage, an electromotive force that is generated through reception of an infrared ray.

The heat-sensitive resistive element14is mounted on the substrate40. The resistance value of the heat-sensitive resistive element14varies with changes in temperature, so that the ambient temperature of the thermopile element13is detected on the basis of the resistance value of the heat-sensitive resistive element14.

The cap41is a substantially tubular shape made of metal, and has an opening that is opened, in the form of a circle, in the light guide of the thermopile element13. A lens42is assembled into the opening of the cap41.

The thermopile element13and the heat-sensitive resistive element14are disposed on the lower face of the substrate40. Four lead terminals43are attached to the substrate40, penetrating the substrate40vertically. The lead terminals43and the electrodes of the thermopile element13and of the heat-sensitive resistive element14are connected by way of bonding wires44a.Driving power is supplied to the thermopile element13and to the heat-sensitive resistive element14, and detection signals are transmitted, through the lead terminals43.

Other than the thermopile element13, a sensing element that outputs a signal upon detection of temperature on the basis of an infrared ray, for instance a bolometer or an infrared diode, can be used as the sensing element that detects an infrared ray.

Materials the resistance value of which varies with temperature, for instance platinum, permalloys and thermistors are well known as sensing elements for temperature compensation in the case of the heat-sensitive resistive element14. However, a thermocouple, diode or the like other than the heat-sensitive resistive element14may also be used as the sensing element for temperature compensation.

Next, the connection wiring8ais configured by having four lead wires45, and is protected by being covered by a metal pipe or protective tube. The ends of the four lead wires45are fixed by crimping with one end of each of respective crimp terminals46a.The other ends of the crimp terminals46aare connected, by a joining means such as welding, to the four lead terminals43disposed on the top face of the substrate.

A sealing member9afor insulatively holding the infrared temperature sensor unit4ais attached, from the opening side of the opening of the tubular portion2, and is fixed to the tubular portion2while covering the connection wiring8a.

One end of the connection wiring8ais connected to the infrared temperature sensor unit4a,and the other end is connected to a connection terminal unit10a.

FIG. 3is a cross-sectional diagram illustrating the connection terminal unit10aof the temperature measuring device of Embodiment 1 of the present invention. As illustrated inFIG. 3, a circuit unit11ais disposed on the connection terminal unit10a.First ends of the circuit unit11aare connected to connector terminals12by way of for instance bonding wires44b,and second ends are connected to first ends of circuit terminals47.

The ends of the four lead wires45are fixed by crimping with first ends of respective crimp terminals46b.The second ends of the crimp terminals46bare connected to respective circuit terminals47by a joining means such as welding.

A sealing member9bfor holding insulatively the circuit unit11ain the interior of the connection terminal unit10ais attached to an end of the connection terminal unit10a,the sealing member9bbeing fixed to the connection terminal unit1awhile covering the connection wiring8a.

A terminal attached to for instance a harness extending from an external circuit (for instance, an ECU), not shown, is connected to the circuit unit11avia the connector terminals12of the connection terminal unit10a.As a result, the output of the infrared temperature sensor unit4ais transmitted to an external circuit (for instance, an ECU) via the lead wires45, the circuit unit11aand the connector terminals12.

FIG. 4is circuit diagram of the temperature measuring device of Embodiment 1 of the present invention. The operation of the circuit unit11awill be explained in detail next with reference to the circuit diagram of the temperature measuring device of the present Embodiment 1 illustrated inFIG. 4.

A signal from the thermopile element13within the infrared temperature sensor unit4ais amplified in an amplifier circuit20a.Current is supplied, from a constant current circuit21, to the heat-sensitive resistive element14within the infrared temperature sensor unit4a.As a result, a voltage output signal at both ends of the heat-sensitive resistive element14, corresponding to a value resulting from conversion of resistance to voltage, is amplified in an amplifier circuit20b.

The amplified voltage outputs of the thermopile element13and of the heat-sensitive resistive element14are inputted to a multiplexing conversion circuit22a(for instance, a multiplexer). The multiplexing conversion circuit22aswitches the inputted signals, at periods established beforehand, and outputs the signals to an analog-digital conversion circuit23a.

The analog-digital conversion circuit23aconverts to digital signals the analog signals received from the multiplexing conversion circuit22a,and outputs the digital signals to a digital signal processing circuit24a.As a result, the digital signal processing circuit24aacquires, as digital signals, a temperature information signal of the temperature sensing part3as detected by the thermopile element13and a temperature information signal of the infrared temperature sensor unit4aas detected by the heat-sensitive resistive element14.

On the basis of the temperature information signal of the infrared temperature sensor unit4a,the digital signal processing circuit24aexecutes a process of correcting a temperature characteristic of the temperature information signal of the temperature sensing part3, a process of correcting signal nonlinearity to linearity, and a process of output adjustment to a desired characteristic.

The corrected value resulting from correction and the adjusted value resulting from output adjustment in the digital signal processing circuit24aare temporarily stored in the storage circuit25. The corrected value and adjusted value having been temporarily stored are set and modified to desired values through communication from the exterior with the storage circuit25via adjustment terminals33, the resulting values being thereafter stored in the storage circuit25. An EEPROM, a flash memory or the like is ordinarily used as the storage circuit25, but a PROM or EPROM may also be used.

The Inter-Integrated Circuit (I2C) scheme is ordinarily resorted to as the communication scheme with the storage circuit25, but for instance the Serial Peripheral Interface (SPI) or Microwire scheme may also be used.

The digital-analog conversion circuit26aconverts to an analog signal the digital signal resulting from signal processing in the digital signal processing circuit24a.The signal resulting from conversion to an analog signal is transmitted to an output interface circuit27a(for instance, a voltage follower circuit), and is voltage-outputted in the form of final temperature information. An instance has been explained in which analog voltage output is used as the output mode, but frequency output or digital output can also be resorted to.

Although not explained in detail herein,FIG. 4illustrates a constant voltage circuit29for supplying constant voltage and a reference voltage circuit30for supplying a reference voltage, within the circuit unit11a.

In Embodiment 1, thus, the circuit unit in the temperature measuring device can be configured, inside the connection terminal unit, spaced from the exhaust pipe the temperature whereof is high on account of exhaust gas. Accordingly, the circuit unit is not exposed to high temperature. It becomes as a result possible to utilize constituent parts made up of inexpensive materials around the circuit unit, thanks to a reduction in thermal impact. Further, the influence of the circuit unit on the temperature characteristic can be reduced, and accordingly it becomes possible to provide an inexpensive high-precision temperature measuring device.

FIG. 5is a cross-sectional diagram illustrating a temperature measuring device of Embodiment 2 of the present invention, in a state where the device is attached to an exhaust pipe. The temperature measuring device of the present Embodiment 2 differs from that of Embodiment 1 in that now the temperature measuring device is configured integrally with a pressure measuring device. The explanation below focuses therefore on this difference.

As illustrated inFIG. 5, the temperature measuring device1bof the present Embodiment 2 is identical to that of Embodiment 1 above, except for the configuration of a connection terminal unit10b.The connection terminal unit10bis configured, integrally with the pressure measuring device15, so that a signal received from the pressure measuring device15is outputted through the connector terminals12.

The exhaust pipe50bin the present Embodiment 2 has a pressure takeout outlet51formed therein. A pressure inlet16ais provided in the connection terminal unit10bhaving the pressure measuring device15accommodated therein. The pressure measuring device15acquires the pressure in the exhaust pipe50bvia the tube17that connects the pressure takeout outlet51and the pressure inlet16a.

FIG. 6is a circuit diagram of the temperature measuring device of Embodiment 2 of the present invention. The operation of the circuit unit11aand of the pressure measuring device15will be explained in detail next with reference to the circuit diagram of the temperature measuring device of the present Embodiment 2 illustrated inFIG. 6.

A pressure detection unit18ainside the pressure measuring device15is for instance configured in the form of a strain gauge on a diaphragm formed in a silicon substrate. This strain gauge detects, as pressure information, the strain of the diaphragm derived from pressure fluctuations, and the pressure information is outputted as a voltage value. In the present Embodiment 2 there is explained a method for detecting pressure by way of a strain gauge, but the pressure detection method is not limited to a strain gauge.

The voltage output of the pressure detection unit18ais amplified in the amplifier circuit20c.The amplified voltage output is transmitted to an analog-digital conversion circuit23b.Further, the pressure information signal converted from an analog signal to a digital signal by the analog-digital conversion circuit23bis transmitted to the digital signal processing circuit24a.The digital signal processing circuit24bperforms a process of correcting a temperature characteristic, a process of correcting signal nonlinearity to linearity, and a process of output adjustment to a desired characteristic.

The digital-analog conversion circuit26bconverts to an analog signal the digital signal resulting from signal processing in the digital signal processing circuit24b.The signal resulting from conversion to an analog signal is transmitted to an output interface circuit27b(for instance, a voltage follower circuit), and is voltage-outputted in the form of final temperature information. An instance has been explained in which analog voltage output is used as the output mode, but frequency output or digital output can also be resorted to.

The pressure measuring device15of the temperature measuring device1bof the present Embodiment 2 is configured integrally with the connection terminal unit10b.Adopting such a configuration allows reducing the size of a harness and of a connector pertaining to pressure measurement, and allows realizing an inexpensive temperature measuring device1bintegrated with the pressure measuring device15.

In the configuration of Embodiment 2, thus, the pressure measuring device is disposed within the connection terminal unit of the temperature measuring device, with the circuit unit of the pressure measuring device being integrated into the circuit unit of the temperature measuring device. As a result it becomes possible to provide an inexpensive temperature measuring device, integrated with a pressure measuring device, with a reduced number of circuit units, as well as reduced connectors and harnesses.

In Embodiment 2, a configuration has been explained in which the pressure measuring device and the connection terminal unit10bare integrated together. In the present Embodiment 3, by contrast, a configuration will be explained in which the pressure detection unit in the pressure measuring device is removed, and a processing circuit of pressure signals is built into the circuit unit.

FIG. 7is a cross-sectional diagram illustrating a temperature measuring device of Embodiment 3 of the present invention, in a state where the device is attached to an exhaust pipe. The temperature measuring device of the present Embodiment 3 differs from that of Embodiment 2 above in that now the temperature measuring device is configured integrally with the pressure detection unit, instead of being configured integrally with the pressure measuring device. The explanation below focuses therefore on this difference.

As illustrated inFIG. 7, a temperature measuring device1cof the present Embodiment 3 is identical to that of Embodiments 1 and 2, except for the configuration of a connection terminal unit10c.The connection terminal unit10cis configured having a pressure detection unit18bintegrated therewith. Signals from the pressure detection unit18bare outputted from the connector terminals12via a circuit unit11b.

The exhaust pipe50bin the present Embodiment 3 has the pressure takeout outlet51formed therein, as is the case in Embodiment 2 above. As in Embodiment 2 above, the pressure inlet16ais provided in the connection terminal unit10chaving the pressure detection unit18baccommodated therein. The pressure detection unit18bacquires the pressure in the exhaust pipe50bvia the tube17that connects the pressure takeout outlet51and the pressure inlet16a.

FIG. 8is a circuit diagram of the temperature measuring device of Embodiment 3 of the present invention. The operation of the circuit unit11band of the pressure detection unit18bwill be explained in detail next with reference to the circuit diagram of the temperature measuring device of the present Embodiment 3 illustrated inFIG. 8.

The pressure detection unit18bis for instance configured in the form of a strain gauge on a diaphragm formed in a silicon substrate. This strain gauge detects, as pressure information, the strain of the diaphragm derived from pressure fluctuations, and the pressure information is outputted as a voltage value. In the present Embodiment 3, there is explained a method for detecting pressure by way of a strain gauge, but the pressure detection method is not limited to a strain gauge.

In the circuit unit11bof the present Embodiment 3, an amplifier circuit20dis further provided in the circuit unit11aexplained in Embodiments 1 and 2 above, and a SENT interface circuit34is provided instead of the digital-analog conversion circuit26aand the output interface circuit27a.

A signal from the thermopile element13within the infrared temperature sensor unit4ais amplified in the amplifier circuit20a.Current is supplied from the constant current circuit21to the heat-sensitive resistive element14within the infrared temperature sensor unit4a.As a result, a voltage output signal at both ends of the heat-sensitive resistive element14, corresponding to the value resulting from conversion of resistance to voltage, is amplified in the amplifier circuit20b.The voltage output signal from the pressure detection unit18bis amplified in the amplifier circuit20d.

The amplified voltage outputs of the thermopile element13, the heat-sensitive resistive element14and the pressure detection unit18bare inputted to a multiplexing conversion circuit22b(for instance, a multiplexer). The multiplexing conversion circuit22bswitches the inputted signal, at periods established beforehand, and outputs the resulting signal to an analog-digital conversion circuit23c.

The analog-digital conversion circuit23cconverts to a digital signal the analog signal received from the multiplexing conversion circuit22b,and outputs the resulting digital signal to a digital signal processing circuit24c.As a result, the digital signal processing circuit24cacquires, as digital signals, a temperature information signal of the temperature sensing part3as detected by the thermopile element13, a temperature information signal of the infrared temperature sensor unit4aas detected by the heat-sensitive resistive element14and a pressure information signal detected by the pressure detection unit18b.

On the basis of the temperature information signal of the infrared temperature sensor unit4a,the digital signal processing circuit24cexecutes a process of correcting a temperature characteristic of the temperature information signal of the temperature sensing part3, a process of correcting signal nonlinearity to linearity, a process of output adjustment to a desired characteristic, a process of correcting a temperature characteristic in the pressure information signal of the pressure detection unit18b,a process of correcting to signal nonlinearity to linearity, and a process of output adjustment to a desired characteristic.

The corrected value resulting from correction and the adjusted value resulting from output adjustment in the digital signal processing circuit24care temporarily stored in the storage circuit25. The corrected value and adjusted value having been temporarily stored are set and modified to desired values through communication from the exterior with the storage circuit25via the adjustment terminals33, the resulting values being thereafter stored in the storage circuit25. An EEPROM, a flash memory or the like is ordinarily used as the storage circuit25, but a PROM or EPROM may also be used.

The Inter-Integrated Circuit (I2C) scheme is ordinarily resorted to as the communication scheme with the storage circuit25, but for instance the Serial Peripheral Interface (SPI) or Microwire scheme may also be used.

The SENT interface circuit34superimposes a temperature signal of the temperature measuring device and a pressure signal of the pressure measuring device onto the digital signal resulting from signal processing in the digital signal processing circuit24c.Further, the SENT interface circuit34transmits the signal, after superposition, in such a way so as to form a pulse signal on the basis of a SENT scheme according to Standard SAE-J2716 of the Society of Automotive Engineers. The acronym “SENT” stands for Single Edge Nibble Transmission.

FIG. 9is a diagram illustrating a SENT output waveform of a temperature measuring device according to Embodiment 3 of the present invention. The signal outputted by the SENT interface circuit34is a pulse signal of repeated 0 V and 5 V, as illustrated inFIG. 9. In order from the beginning, the signal is made up of: a synchronization pulse denoting synchronization data, a status pulse denoting status data, three communication data pulses denoting pressure information data, three communication data pulses denoting temperature information data, an error detection pulse denoting error detection data, and a pause pulse for fitting one period to a predetermined time.

InFIG. 9, the units of the time axis are “ticks”. In the present Embodiment 1, there is set for instance:

As illustrated inFIG. 9, one interval of the pulse signal extends from the point in time at which a predetermined threshold value is crossed upon a voltage fall, until the from the point in time at which the threshold value is crossed again upon a new voltage fall, following an intervening voltage rise. The pulse signal illustrated inFIG. 9is set so that the pulse period is lengthened by a predetermined time whenever a numerical value, denoted by a bit string of corresponding data, increases by one.

In the present Embodiment 3 described above, a SENT scheme widely used in on-board LAN communication schemes has been explained as the communication scheme between the sensor devices and the ECU, but the present invention is not limited to such a communication scheme. For instance, serial transmission may be resorted to on the basis of communication schemes such as Local Interconnect Network (LIN), Inter-Integrated Circuit (I2C), Controller Area Network (CAN) and Peripheral Sensor Interface 5 (PSI5 ).

In the temperature measuring device1cof the present Embodiment 3, thus, the pressure detection unit18bis configured integrally with the connection terminal unit10c,and thus a circuit unit pertaining to pressure measurement can be integrated into the circuit unit11b.By including such a configuration it becomes possible to realize an inexpensive temperature measuring device1cintegrated with a pressure detection unit and in which there can be reduced the number of circuit units pertaining to pressure measurement, while reducing connectors and harnesses.

Further, it becomes possible to reduce connector terminals and harnesses even if serial output is adopted as the output mode. An inexpensive high-precision temperature measuring device1cboasting high communication reliability can be provided as a result.

In the configuration of Embodiment 3, thus, the pressure detection unit is disposed in the connection terminal unit of the temperature measuring device, and exhaust pressure is measured directly by a circuit unit. A temperature measuring device can be provided as a result that is integrated with high-precision pressure measurement boasting excellent responsiveness towards pressure fluctuations.

In Embodiment 1, an instance has been explained in which a pressure detection unit is configured integrally with a circuit unit. In the present Embodiment 4, an instance will be explained in which a pressure detection unit is provided in the vicinity of an infrared temperature sensor unit.

FIG. 10is a cross-sectional diagram illustrating a temperature measuring device of Embodiment 4 of the present invention, in a state where the device is attached to an exhaust pipe. The temperature measuring device of the present Embodiment 4 differs from that of Embodiment 3 in that now the temperature measuring device is configured integrally with a pressure detection unit by arranging a pressure detection unit adjacent to the infrared temperature sensor unit4b.The explanation below focuses therefore on this difference.

As illustrated inFIG. 10, a temperature measuring device1dof the present Embodiment 4 differs from Embodiment 1 in that the pressure detection unit18bis disposed in the infrared temperature sensor unit4b,and in that a pressure inlet16band a hollow portion19are provided in a tubular portion2b.Signals from the pressure detection unit18bare outputted through the connector terminals12via a connection wiring8band the circuit unit11b.

FIG. 11is a cross-sectional diagram, in the radial direction, illustrating a state in which the temperature measuring device of Embodiment 4 of the present invention is attached to an exhaust pipe. As illustrated inFIG. 11, the pressure inlet16bis provided by formation of a passage having a diameter of about 1 mm at the tubular portion2b.The pressure inlet16bis opened in an exhaust pipe50cwithin a hole of the exhaust pipe50c,as illustrated inFIG. 10. The pressure detection unit18bdetects the pressure of exhaust gas that passes through the pressure inlet16b.

As illustrated inFIG. 11, the hollow portion19is provided, in the tubular portion2b,on the outer peripheral side of the infrared temperature sensor unit4b.By providing such a hollow portion19, it becomes possible to reduce the thermal impact transferred from the exhaust pipe50cto the infrared temperature sensor unit4band the pressure detection unit18bvia the tubular portion2b.

FIG. 12is a circuit diagram of a temperature measuring device of Embodiment 4 of the present invention. A detailed explanation follows next focusing on the operation pertaining to the pressure detection unit18disposed on the infrared temperature sensor unit4b,with reference to the circuit diagram of the temperature measuring device of the present Embodiment 4 illustrated inFIG. 12. The circuit unit11binFIG. 12is identical to the circuit unit11binFIG. 8explained in Embodiment 3.

A signal from the thermopile element13within the infrared temperature sensor unit4bis amplified in the amplifier circuit20a.Current is supplied from the constant current circuit21to the heat-sensitive resistive element14within the infrared temperature sensor unit4a.As a result, a voltage output signal at both ends of the heat-sensitive resistive element14, corresponding to the value resulting from conversion of resistance to voltage, is amplified in the amplifier circuit20b.The voltage output signal from the pressure detection unit18bprovided in the infrared temperature sensor unit4ais amplified in the amplifier circuit20d.

The amplified voltage outputs of the thermopile element13, the heat-sensitive resistive element14and the pressure detection unit18bare inputted to the multiplexing conversion circuit22b(for instance, a multiplexer). The multiplexing conversion circuit22bswitches the inputted signal, at periods established beforehand, and outputs the resulting signal to the analog-digital conversion circuit23c.

The analog-digital conversion circuit23cconverts to a digital signal the analog signal received from the multiplexing conversion circuit22b,and outputs the resulting digital signal to the digital signal processing circuit24c.As a result, the digital signal processing circuit24cacquires, as digital signals, a temperature information signal of the temperature sensing part3as detected by the thermopile element13, a temperature information signal of the infrared temperature sensor unit4bas detected by the heat-sensitive resistive element14and a pressure information signal detected by the pressure detection unit18b.

On the basis of the temperature information signal of the infrared temperature sensor unit4b,the digital signal processing circuit24cexecutes a process of correcting a temperature characteristic of the temperature information signal of the temperature sensing part3, a process of correcting signal nonlinearity to linearity, a process of output adjustment to a desired characteristic, a process of correcting a temperature characteristic of the pressure information signal of the pressure detection unit18bon the basis of the temperature information signal of the infrared temperature sensor unit4b,a process of correcting to signal nonlinearity to linearity, and a process of adjusting the output to a desired characteristic.

The corrected value resulting from correction and the adjusted value resulting from output adjustment in the digital signal processing circuit24care temporarily stored in the storage circuit25. The corrected value and adjusted value having been temporarily stored are set and modified to desired values through communication from the exterior with the storage circuit25via the adjustment terminals33, the resulting values being thereafter stored in the storage circuit25.

The SENT interface circuit34superimposes a temperature signal of the temperature measuring device and a pressure signal of the pressure measuring device onto the digital signal resulting from signal processing in the digital signal processing circuit24c.Further, the SENT interface circuit34transmits the signal, after superposition, in such a way so as to form a pulse signal by a SENT scheme.

The temperature measuring device1din the present Embodiment 4 is configured in such a manner that the pressure detection unit18bis built into the infrared temperature sensor unit4b.Specifically, pressure is introduced into the pressure detection unit18bvia the pressure inlet16bprovided in the tubular portion2b.

Adopting such a configuration allows measuring directly the pressure of exhaust from the exhaust from the exhaust pipe50b,without any intervening tube passing through an interposed tube. As a result a temperature measuring device1dcan be provided integrated with high-precision pressure measurement and in which responsiveness towards pressure fluctuations can be improved.

In the configuration of Embodiment 4, thus, the pressure detection unit is disposed inside the infrared temperature sensor unit, so as to measure directly the pressure of exhaust from the exhaust pipe. As a result a temperature measuring device can be provided integrated with high-precision pressure measurement boasting improved responsiveness towards pressure fluctuations.