JPH01307652A - Temperature controller for heater for oxygen sensor - Google Patents

Abstract

PURPOSE:To realize a long service life of the title controller and to execute a temperature control with high reliability and with high accuracy by controlling the heating power supplied to a heater for heating an oxygen sensor by turning on and off a switching element. CONSTITUTION:A heater temperature (oxygen sensor temperature) of a thermocouple 9 of a temperature controller 60 is detected as thermoelectromotive force, and this thermoelectromotive force is compared with a set temperature of a setting device in a PID controller 41, a PID operation is performed and inputted as a control operation output signal S to a pulse width modulating circuit 50, a control of a pulse duty ratio is executed, and a high frequency pulse signal of this pulse width is outputted to a power transistor (switching element) 15 through a photocoupler 55. An output of a DC current supply circuit 11 receives switching of the TR 15, is provided to a primary winding 16a of a high frequency transformer 16 as high frequency power, and high frequency AC power from a secondary winding 16b is inputted to a heater 7 as DC power by a smoothing circuit 18. By the signal S, a temperature of the heater 7 is maintained at a set temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature control device for a heater used in an oxygen sensor that detects the oxygen concentration of exhaust gas or the like.

[Conventional technology]

iS in exhaust gas! Since the temperature of the sensor element greatly affects the measurement accuracy of the heater for detecting 2-11 degrees, it is necessary to maintain the temperature of the sensor element at a constant high temperature, for example, 500 degrees Celsius or higher during use.

Temperature control devices for this purpose are generally those that use an AC i power source for on/off control or phase angle control using a thyristor. As disclosed in the above publication, a system in which a series transistor connected in series with a heater is used to adjust the heater current is generally adopted.

[Problem to be solved by the invention]

However, among the conventional temperature control circuits mentioned above, those that use an AC power source are small in size and have a small heat capacity R, and in the case of an oxygen sensor, the pulsating power directly appears as a fluctuation in temperature of FA degrees. ] - From the equation (below) for the electromotive force generated by the sensor, it is clear that the temperature T of the sensor
Fluctuations in this appear as fluctuations in the generated electromotive force, and therefore there is a problem in that the accuracy of oxygen 11 degree measurement is poor.

However, E: Generated electromotive force R: Gas constant T: Absolute temperature of sensor n: Ion valence (n=4) F: Faraday constant P 02 (A': Base Q Reference oxygen partial pressure PO2 of air, measured gas M cumulative partial pressure in
Since series transistors are used as variable resistors, they generate a large amount of heat, and this heat dissipation causes the temperature of the converter to rise, leading to short lifespans and low reliability of the electronic components used in the converter. Ta.

This invention solves the above-mentioned conventional problems, and aims to provide a temperature control device for an oxygen sensor heater that generates a small amount of heat, has a long life, is highly reliable, and is capable of highly accurate temperature control. .

[Means to solve the problem]

The first invention of this application controls the heating power supplied to the heater for heating the sensor element of the oxygen sensor. A temperature control device for a heater in which a primary winding of a high frequency transformer is connected to a DC current supply circuit via a switching element, and a secondary winding of the high frequency transformer is connected to a DC current supply circuit through a rectifying circuit and a smoothing circuit to control the temperature of a heater. and a temperature control output device that outputs a control oil level output signal in accordance with a deviation signal between the set temperature and the heater temperature, and a high frequency pulse signal in accordance with the control unit 0 output signal to the switching element as an on/off signal. and a pulse generator that controls the pulse width and/or pulse period of the high-frequency pulse so that when the control calculation output signal is large, the on time of the switching element becomes large. This is a temperature control device for a heater for an oxygen sensor.

Further, a second invention of this application connects the primary winding of a magnetic amplifier to the tertiary winding of the high-frequency transformer, and connects the control winding of this magnetic amplifier to the output side of the smoothing circuit. , a temperature control device for an oxygen sensor heater, in which an auxiliary power source formed by connecting a DC constant voltage circuit to the secondary winding of the magnetic amplifier is attached to the device of the first invention.

Further, a third invention of this application is a heater temperature control device for controlling heating power supplied to a heater for heating a sensor element of an oxygen sensor, the device having a DC current supply circuit connected to a commutating diode and a smoothing device via a switching element. The circuit is connected, and the output side of this smoothing circuit is connected to the heater, and a temperature adjustment output 1 that emits a control calculation output signal according to the deviation signal between the set temperature and the heater temperature! and a high-frequency pulse signal corresponding to this control calculation output signal is applied to the switching element as an on/off signal, and when the control calculation output signal is large, the on time of the switching element per medium time is large. Temperature control of an oxygen sensor heater 2 characterized in that it is equipped with a pulse generator that controls the pulse width and/or pulse period of high-frequency pulses.
There are 11 devices.

In this invention, the control field output signal corresponding to the deviation signal between the set temperature and the heater temperature is defined as the control field output signal corresponding to the deviation signal from the proportional control part, proportional-integral control wave mouth, proportional-integral control oil filling or proportional- This refers to the output signal that has been subjected to integral-integral control calculations.

[Effect]

In the heater temperature control device of the present invention, the temperature control output is 5A' in accordance with the deviation signal between the heater temperature and the set temperature.
The control wave output signal emitted by the FK controls the pulse width and/or pulse period of the high frequency pulse signal emitted by the pulse generator. The DC output of the DC upstream supply circuit is converted into high frequency AC power by a switching element that is turned on and off by the high frequency pulse signal, and is converted to high frequency AC power via a high frequency transformer, then by a rectifier circuit and a smoothing circuit, or directly by a commutating diode and a smoothing circuit. The current is converted into direct current and supplied to the heater.

Further, in the heater temperature control device of the second aspect of the invention, a direct current proportional to the heater current flows through the control winding of the magnetic amplifier of the auxiliary power supply to bias the iron core. This allows high frequency!・Even when the primary side input power of the lance is large, the upper limit of the secondary side voltage of the magnetic amplifier is controlled due to the nonlinearity of the iron core of the magnetic amplifier, and a high voltage is applied to the DC constant voltage circuit. is prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG.

In FIG. 2, reference numeral 1 denotes an oxygen sensor, which consists of a bottomed cylindrical body 2 made of a solid electrolyte such as zirconia, with porous platinum electrodes 3.4 adhered to both the front and back surfaces, and the outer surface covered with a ceramic filter membrane 5. , 6 is a flange for attachment to an exhaust pipe or the like. Reference numeral 7 denotes a tubular heater made of a resistance wire, which is fixed to the inner surface of the oxygen sensor 1 via a ceramic ring 8. Reference numeral 9 denotes a thermal lightning pair, the detection end 9a of which is placed close to the inner surface of the oxygen sensor 1, and the intermediate portion thereof is fixed to the inner surface of the heater 7 with heat-resistant cement 10.

In FIG. 1, reference numeral 11 denotes a DC current supply circuit, which is made up of an AC power supply 12 connected to a rectifier 13 and a smoothing capacitor 14. 16a. 17 is a rectifier circuit connected to the secondary winding 16b of the high frequency transformer 16; 18 is a smoothing circuit consisting of an actance 19 and a capacitor 20.21 and connected to the output side of the rectifier circuit 17; The output side of the smoothing circuit 18 is connected to the heater 7 and also to one of the magnetic amplifiers 31.
It is connected to the IJtl1 winding 31b. 30 is an auxiliary power supply, and a DC constant voltage circuit 32 is connected to the output side of the magnetic amplifier 31.
It consists of connecting The primary winding 31a of the magnetic amplifier 31 is
It is connected to the tertiary winding 16G of the high frequency 1-lance 16. Further, the DC constant voltage circuit 32 has a known configuration in which a capacitor 34, a three-terminal regulator 35, and a capacitor 36 are connected to the output side of a rectifier 33, and output terminals 37 and 38 each have a voltage of +15'V, for example.
It also generates a DC constant voltage of -15V.

On the other hand, 40 is a temperature control output device, which is made up of a thermocouple 9 and a P10 regulator 41 connected thereto. Further, 50 is a pulse width modulation circuit which is a pulse generator, and is a pulse width modulation circuit which is a pulse generator, and is a pulse width modulation circuit which is a pulse generator.
A triangular wave generating circuit 51 that generates a triangular wave of
A comparator 352 generates a high-frequency pulse signal P whose pulse is large when the control sieve output signal is large. It is optically coupled and electrically insulated and connected to the base of the power transistor 15.

In the heater temperature control device 60 configured as described above, the heater temperature (=oxygen sensor temperature) is detected by the thermocouple 9 as a thermoelectromotive force, and this thermoelectromotive force is used as the set temperature ( Specifically, it is compared with the thermoelectromotive force of the thermocouple 9 corresponding to the temperature, subjected to PID processing, and output as the control oil n output signal S to the pulse f1 modulation circuit 50. In the pulse width modulation circuit 50,
The pulse duty ratio is controlled so that the pulse width becomes large when the control calculation output signal S is large, and a high frequency pulse signal QP having this pulse width is applied to the power transistor 15 via the photocoupler 55. The output of the DC current supply circuit 11 is switched by the pulse signal P of the power transistor 15, and the primary winding 1! of the high frequency transformer 16 is output as high frequency AC power. i! The high frequency AC power given to the secondary 8 wire 16a and transferred to the secondary 8 wire 16b side is
The rectifier circuit 17 and the smoothing circuit 18 convert the DC power into DC power, which is then applied to the heater 7 . When the temperature of the heater 7 rises and approaches the set temperature, the control calculation output signal S of the temperature adjustment output device 40 decreases, the pulse width modulation circuit 50 decreases the pulse width of the high frequency pulse signal P, and the power transistor 15 The switching reduces the power given to the heater 7 and maintains the temperature of the heater 7 at the set temperature.

On the other hand, in the auxiliary power supply 30, a DC power supply proportional to the current of the heater 7 has a magnetic amplification ':? A31 control winding 31
b, the primary winding 16a of the high frequency transformer 16
When the input power of the three-terminal regulator 35 is large (therefore, the heater current is large), the nonlinearity of the iron core of the magnetic multiplier 31 suppresses the upper limit of the AC voltage generated in the secondary winding 31c, and therefore the three-terminal regulator 35 This prevents high voltage from being applied to the This auxiliary power source 30 can be used as a DC constant voltage power source for the temperature control output device 40, the pulse modulation circuit 50, and the like.

Next, FIG. 3 shows another embodiment of the present invention.
Components that are the same or corresponding to those in the figures are given the same reference numerals as in FIG. 1.

That is, in this embodiment, a DC current supply circuit 72 is used that once steps down the voltage of an AC power supply 12 using a commercial frequency transformer 71, and then rectifies and flows the voltage through a rectifier 13 and a capacitor 14 to supply DC power. The high frequency AC voltage switched by the power transistor 15 is
This embodiment differs from the previous embodiment in that the commutation diode 73 and the smoothing circuit 74 provide rectification to the τ heater 7.

In this heater temperature control device 70 as well, as in the above embodiment, the pulse width modulation circuit +
The high frequency pulse signal P generated by the 1850 causes the
The power transistor 15 is switched via the coupler 55, and DC power is given to the heater 7 based on a control calculation output signal corresponding to the deviation between the heater temperature and the set temperature.
Maintain the heater 7 at the set temperature.

Although the setting of the constant voltage power supply is omitted in this embodiment, the DC constant voltage circuit 32 shown in FIG. 1 can be connected to the tertiary winding of the transformer 71 to form a constant voltage power supply. . Further, in this embodiment, the transformer 71 is omitted and the AC power supply 12 is directly connected to the rectifier 13 and the capacitor 1/I.
It is also possible to use a direct current supply circuit connected to the

The present invention is not limited to the above-mentioned embodiments. For example, in addition to the pulse 111 modulation circuit 50, a frequency modulation circuit may be used as the pulse generation circuit to maintain a constant pulse width when the control calculation output signal S is large. The high-frequency pulse signal P may be controlled so that the frequency is constant, or the pulse generator may be configured with a digital signal processing circuit.

Furthermore, in each of the above embodiments, the heater temperature is detected using the thermocouple 9, but as shown in FIG. Temperature control output device that calculates a control calculation output signal according to the deviation of r! t81 can also be used. In the figure, 82 is a resistor for detecting the heater current, 83 and 84 are high resistance resistors connected in parallel to the heater 7, and 85 and 86 are amplifiers, which divide the voltage at a predetermined ratio. Heater voltage V J3 and heater current 'I+ are amplified by amplifiers 85 and 86, then digitally converted by Δ/D conversion 87, subjected to calculations of V, , /r, and converted into microblock as heater resistance RH. It is taken into the setter 88. In the microprocessor 88, a heater voltage approximately 1/10 of the expected control heater voltage at power-on is applied to the heater 7 in advance, and the heater resistance R8 at room temperature is set to C1.
Then, switch the heater voltage to the temperature control voltage, measure the heater resistance R, C1, and obtain the resistance ratio R, , /R.
8 and performs subsequent signal processing. This resistance ratio is, however, α: Temperature coefficient of heater resistance t: Temperature at the time of measurement of heater resistance to: Room temperature δ of heater resistance
The signal is proportional to the heater temperature, and is not affected by variations in heater resistance when replacing the sensor. The heater resistance RS for the set hot water temperature t3 of the heater is determined by
The control sieve output signal S obtained as the difference in resistance ratio is sent to the duty ratio calculating section 88b (pulse generator) of the microprocessor 88, and the pulse generator output signal S is compared with the difference signal S. The signal is subjected to modulation and is applied as a high-frequency pulse signal P to the power transistor 5 via the photocoupler 55.

Further, in each of the above embodiments, an AC power source is used as the power source of the DC current supply circuit, but a DC current supply circuit using a battery or a DC generator as the power source may also be used. In this case, the rectifier and smoothing circuit are not used. This eliminates the need and the device becomes simpler.

Further, as the switching element, a power FET or the like can be used in addition to the power transistor.

(Effects of the Invention) As explained above, according to the present invention, since the switching element is used only for on/off switching, a heater temperature control device that generates less heat, has a long life, and is highly reliable can be obtained. Further, since direct current is supplied to the heater, there is little variation in temperature, and highly accurate temperature control can be performed.

In the heater temperature control device according to the first aspect, since a high frequency transformer is used, the device can be made smaller and lighter.

In the heater temperature control device according to claim 2, even when the heater current is large, the magnetic increase in the auxiliary power supply [1]
The rise in the secondary side voltage of the regulator is suppressed, and high voltage is not applied to the three-terminal regulator.
The heat load of C) is reduced, and the lifespan and reliability of the auxiliary power source can be extended and improved.

In the heater temperature control device according to claim 3, when the power is turned on,
The inrush current during switching is small, and the switching is 0N-OF.
The F duty ratio can be greatly changed from 0 to 100%.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a heater temperature control device showing one embodiment of the present invention, Fig. 2 is a vertical cross-sectional view of an oxygen sensor, and Fig. 3 is a heater temperature control device showing another embodiment of the invention. Circuit diagram of the device. FIG. 4 is a circuit diagram showing another embodiment of the temperature control output device and the pulse generator. DESCRIPTION OF SYMBOLS 1... Oxygen sensor, 7... Heater, 9... Thermocouple, 11... DC current supply circuit, 15... Power transistor (switching element), 16... High frequency transformer, 16a...・-Secondary winding, 16b...Secondary winding,
16c... Tertiary winding, 17... Rectifier circuit, 18...
- Smoothing circuit, 30... Auxiliary power supply, 31... Magnetic amplifier, 31a...-Next winding, 31b... Control winding, 31c... Secondary winding, 32...・DC constant voltage circuit,
40... Temperature control output device, 41... PID controller, 50... Pulse width modulation circuit (pulse generator), 5
1... Triangular wave generation circuit, 52... Comparator, 55...
・Hotokabura, 60... Heater temperature control device, 70
... Heater temperature control device, 72 ... DC current supply circuit, 73 ... Commutation diode, 74 ... Smoothing circuit, 81 ... Humidity control output device, 88 ... Microprocessor , 88a... Comparison calculation unit, 88b... Duty comparison calculation unit (pulse generator). Procedure 1rJ Masahaya) 1989 1st [6J] 30th Patent Application No. 137858 2, Title of Invention Temperature Control Device for Oxygen Sensor Heater 3, Relationship with Person Making Correction f1 Patent Applicant Residence Location 2-56 Suda-cho, Mizuho-ku, Nagoya Name (40
6) Nippon Insulators Co., Ltd. Representative Toshito Ohara 4, Agent 〒460 5, Amendment order attached with El Voluntary action 6, Number of claims increased by amendment None 7, Supplementary +
[Claims of the patent specification, detailed description of the invention J3 and 8
, Contents of amendment (1) The description of the claims in the statement of claim is supplemented as shown in the attached sheet. - (2) 1 DC current supply circuit J on page 5, line 10 of the specification is corrected to "DC power supply circuit." (3) "DC current supply device J" in Mei III, page 6, lines 13 to 14 is corrected to "DC power supply circuit." (4) Correct "DC current supply circuit" on page 7, line 17 of Mei III to "DC power supply circuit 1." I) "DC current supply circuit" on page 9, line 5 in Akira II
is corrected as 1 DC power supply circuit 1. (6) Correct "DC current supply circuit" on page 11, line 10 of Mei 111 Old to read "DC power supply circuit." (7) Bright 11 [1m, page 12, line 20, "DC current supply circuit", j is corrected to "DC power supply circuit". (8) 1i on page 13, lines 19 and 20 of the specification! 1
"Current current supply circuit" is corrected to "DC power supply circuit." (9) "1 DC current supply circuit" on page 16, line 9 of the specification is corrected to "DC power supply circuit." (10) Correct ``DC current supply circuit'' in page 16, line 11 of Akirall 1 Dictionary to ``1 DC power supply circuit''. (11) "DC current" in the first line of page 17 of the specification is corrected to "1 DC power." (12) Correct “DC current supply circuit” on page 18, line 5 of Mei 111J to “ti DC power supply circuit.” (13) Correct “DC current supply circuit” on page 18, line 16 of Mei Ill. 0 current power supply circuit”. Claim 1: A heater temperature control 11 device for controlling heating power supplied to a heater for heating a sensor element of an oxygen sensor, wherein a high frequency transformer is connected to the primary of a high frequency transformer via a switching element to an Lλ The secondary winding of this frequency transformer is connected to the heater via a rectifier circuit and a smoothing circuit, and the temperature at which a control calculation output signal is generated according to the deviation signal between the set temperature and the heater temperature is determined. A control output device;
A high-frequency pulse signal corresponding to this ilJ control calculation output signal is applied to the switching element as an on/off signal, and the n-frequency pulse is set so that when the control calculation output signal is large, the on time of the switching element becomes large. 1. A temperature control device for a heater for an oxygen sensor, comprising: a pulse generator for controlling a pulse width J3 and/or a pulse period. 2. Connect the primary winding of a magnetic amplifier to the tertiary winding of the high frequency transformer, and connect the R and II windings of this magnetic amplifier to the output side of the smoothing circuit, and The temperature control device for an oxygen sensor heater according to claim 1n1, further comprising an auxiliary power source formed by connecting a DC constant voltage circuit to the secondary winding of the hood. 3. A heater control device that controls the heating power supplied to the heater for heating the sensor cord of the oxygen sensor, and 1. A temperature control output device to which a smoothing circuit is connected, the output side of this smoothing circuit is connected to a heater, and which emits a control calculation output signal according to a deviation signal between a set temperature and a heater temperature, and this control calculation output signal. A high frequency pulse signal corresponding to the switching element is applied as an on/off signal to the switching element, and the pulse width of the high frequency pulse and/or 11 of pulse period
1. A temperature control girt for an oxygen sensor heater, characterized in that it is equipped with a pulse generator that performs 11 control.

Claims (1)

[Claims] 1. A heater temperature control device for controlling heating power supplied to a heater for heating a sensor element of an oxygen sensor, which includes a DC current supply circuit connected to a primary winding of a high-frequency transformer via a switching element. and a temperature control output device which connects the secondary winding of the high frequency transformer to the heater via a rectifier circuit and a smoothing circuit, and which emits a control calculation output signal according to a deviation signal between the set temperature and the heater temperature. , a high-frequency pulse signal corresponding to this control calculation output signal is applied to the switching element as an on/off signal, and the high-frequency pulse is applied so that when the control calculation output signal is large, the ON time of the switching element per unit time is large. 1. A temperature control device for an oxygen sensor heater, comprising a pulse generator that controls pulse width and/or pulse period. 2. Connect the primary winding of a magnetic amplifier to the tertiary winding of the high frequency transformer, and connect the control winding of this magnetic amplifier to the output side of the smoothing circuit, and 2. The temperature control device for an oxygen sensor heater according to claim 1, further comprising an auxiliary power source comprising a DC constant voltage circuit connected to the secondary winding. 3. A heater temperature control device that controls the heating power supplied to the heater for heating the sensor element of an oxygen sensor, in which a commutation diode and a smoothing circuit are connected to the DC current supply circuit via a switching element, and this smoothing a temperature control output device that connects the output side of the conversion circuit to the heater and generates a control calculation output signal according to a deviation signal between the set temperature and the heater temperature; Give it to the element as an on/off signal,
It is characterized by comprising a pulse generator that controls the pulse width and/or pulse period of the high-frequency pulse so that when the control calculation output signal is large, the on-time per unit time of the switching element is large. Temperature control device for oxygen sensor heater.