JP2018072005A - Heater controller for gas concentration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heater driving device capable of circumventing continuous noise signal due to on/off switching of a heater when a resistance value of a gas detection element is measured in a gas concentration sensor.SOLUTION: A heater controller 100 for controlling activation of a heater of a gas concentration sensor includes a gas detection element 30 and a heater 40 for heating and activating the gas detection element. The number of synchronization between the detection cycle of the resistance value of the gas detection element and the drive cycle of the heater is set as to be the smallest within a predetermined time so that the detection cycle of the resistance value of the gas detection element 30 and the drive cycle of activation to the heater 40 are not synchronized at all times.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heater controller for a gas concentration sensor for controlling energization to a heater that activates a gas detection element of the gas concentration sensor.

  In a gas concentration sensor having a gas detection element including at least one cell composed of a solid electrolyte body and a pair of electrodes and detecting the concentration of a specific gas such as oxygen, the gas detection element is activated when the temperature rises, The electrolyte body exhibits oxygen ion conductivity satisfactorily, thereby enabling detection of the concentration of a specific gas. The gas detection element is heated by the heat of the exhaust gas discharged from the internal combustion engine. On the other hand, the gas concentration sensor includes a heater for heating the gas detection element in order to ensure early activation of the gas detection element and stability of operation by keeping the element temperature constant.

  The heater control device for the gas concentration sensor performs heater energization control by normal PWM (pulse width modulation) control. Here, the drive cycle applied to the PWM control should be operated as long as possible within a range that does not greatly affect the temperature change of the gas detection element as the heater is turned on / off, but it depends on the characteristics of the gas detection element. Some have been developed that require a shorter driving cycle.

  The heater controller of the gas concentration sensor detects the temperature of the gas detection element by detecting the resistance value (impedance) of the gas detection element while detecting the concentration of the specific gas by the gas detection element. The heater control device calculates the duty ratio in PWM control based on the detection result of the gas detection element temperature, and controls the heater energization to keep the temperature of the gas detection element constant.

Here, as shown in FIG. 6, when the ON / OFF switching timing of energization to the heater by the PWM control and the detection timing (detection period) of the resistance value of the gas detection element overlap, noise detection results are detected. May overlap. Therefore, a control device capable of forcibly shifting the on / off switching timing so that the on / off switching timing in the PWM control of energization to the heater does not overlap with the detection timing of the element resistance value. Is known (see, for example, Patent Document 1).
Similarly, the resistance value is calculated multiple times within a single cycle so that it is not affected by noise when the heater is turned on / off, and the current resistance value is correlated with the previous calculated value. A control device that calculates a value is known (see, for example, Patent Document 2).

JP 2006-113081 A JP2015-64208A

However, the method of Patent Document 1 requires control in accordance with the on / off switching timing of PWM control, and requires synchronization processing of element resistance detection control and heater drive PWM control, but element resistance detection control. When the heater-driven PWM control is performed by another device, it is considered difficult to synchronize the control timing. Even when element resistance detection control and heater drive PWM control are performed with the same device, the control contents are complicated to synchronize the control timing, and a high-performance microcomputer is required. Leading to Further, when the PWM control drive cycle is shortened, there arises a problem that a desired time cannot be set.
Also, in the method of Patent Document 2, when the PWM control drive cycle is shortened, the time of one cycle is shortened, so that a sufficient number of times for calculating the resistance value cannot be taken within one cycle, and the accurate resistance There arises a problem that the value cannot be calculated.

  In addition, when reducing the effect of noise caused by switching on / off the power supply to the heater, it is possible to reduce the effect of transient noise by performing an annealing process on the previous value. When the detection timing and the heater-driven PWM control overlap for a certain period, there is a problem that the influence cannot be reduced by the annealing process.

  The present invention has been made to solve the above-described problems. The heater is energized so that the detection period of the resistance value of the gas detection element and the drive period of the PWM signal energizing the heater are not always synchronized. It is an object of the present invention to provide a heater control device for a gas concentration sensor that is configured not to be continuously affected by noise associated with heater on / off switching by setting a PWM signal drive cycle. .

  A heater control device for a gas concentration sensor according to the present invention includes a gas detection element including at least one cell having a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and heating the gas detection element to activate the gas detection element. A heater control device for controlling energization to a heater of a gas concentration sensor comprising a heater for generating gas, so that the detection cycle of the resistance value of the gas detection element and the drive cycle of energization to the heater are not always synchronized. The heater driving cycle is set so that the number of tunings between the element resistance detection cycle and the heater driving cycle is minimized within a predetermined time.

  In the present invention, since the heater drive cycle is set so that the detection cycle of the resistance value of the gas detection element and the drive cycle of the PWM signal energizing the heater are not always synchronized, the resistance of the gas detection element of the gas concentration sensor is set. Since the noise signal accompanying the on / off switching of the heater is not continuously applied at the measurement timing, the resistance of the gas detection element can be measured without impairing the effect of the annealing process in the signal processing.

It is a block circuit diagram which shows the heater control apparatus of the gas concentration sensor concerning embodiment of this invention. It is a chart figure which shows the heater drive timing and sensor resistance measurement timing in Embodiment 1 of this invention. It is a flowchart figure showing the calculation method of the heater drive period in the fixed period concerning Embodiment 2 of this invention. It is a flowchart figure showing the calculation method of the heater drive period in the variable period concerning Embodiment 3 of this invention. It is a flowchart figure showing the setting method of the drive period in Embodiment 3 of this invention. It is a chart figure which shows the heater drive timing in the past, and sensor resistance measurement timing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, a heater control device for a gas concentration sensor according to an embodiment of the present invention will be described with reference to FIGS. In this embodiment, the gas concentration sensor is a linear air-fuel ratio sensor (hereinafter referred to as an A / F sensor) as an example, and the heater control device is an electronic control device (ECU = Engine Control Unit) of an automobile as an example. .

FIG. 1 is a block circuit diagram of a heater control device for a gas concentration sensor. In FIG. 1, a linear A / F sensor 10 as a gas concentration sensor is electrically connected to an electronic control device 100 as a heater control device. Has been.
In addition, since it is using a well-known thing about exclusive IC (ASIC) which comprises the electronic control apparatus 100 for controlling the linear A / F sensor 10 and the linear A / F sensor 10, its structure etc. A detailed description will be omitted, and a schematic configuration will be described below.

  The linear A / F sensor 10 is a sensor that is attached to an exhaust passage (not shown) of an automobile engine and detects the air-fuel ratio of the exhaust gas based on the oxygen concentration in the exhaust gas flowing through the exhaust passage. The linear A / F sensor 10 draws a plurality of lead wires from the sensor element 20 to the outside and is electrically connected to the electronic control device 100 arranged at a distant position. The electronic control device 100 includes a microcomputer 60 and incorporates a dedicated integrated circuit (hereinafter referred to as ASIC) 70 for operating the linear A / F sensor 10 and a heater driver 50. The electronic control unit 100 controls energization to the linear A / F sensor 10 using the ASIC 70 and the heater driver 50, and performs feedback control of the air-fuel ratio of the engine based on the output obtained from the linear A / F sensor 10. .

The sensor element 20 includes a gas detection element 30 and a heater 40. The gas detection element 30 includes an Ip cell 31 that functions as an oxygen pump cell and a Vs cell 32 that functions as an oxygen concentration detection cell. Each cell is a solid electrolyte body. And a pair of electrodes provided on the solid electrolyte body. One of the electrodes provided in the Ip cell 31 and the Vs cell 32 is electrically connected to each other and connected to the COM port of the linear A / F sensor 10 as shown in FIG. The other electrode of the Vs cell 32 is connected to the Vs + port, and the other electrode of the Ip cell 31 is connected to the Ip + port.
The heater 40 includes a heating resistor 41, and a voltage Vh from the battery is applied to both ends of the heating resistor 41. The heater driver 50 of the electronic control device 100 is connected to one heater terminal of the heating resistor 41, and PWM control (pulse width modulation control) of energization to the heating resistor 41 is performed.

Next, a schematic configuration of the electronic control device 100 to which the sensor element 20 is connected will be described. The electronic control device 100 has various functions related to the control of the microcomputer 60, the ASIC 70, the heater driver 50, and other engines (not shown), and mainly relates to the microcomputer 60, the ASIC 70, and the heater driver 50 below. The function will be explained.
In addition, the electronic control device 100 includes a resistor R1 and a detection resistor R4 connected to the COM port of the linear A / F sensor 10.

  The microcomputer 60 includes a heater control unit 61 and an A / D converter 62. The A / D converter 62 is connected to the VIP port and the VRPVS port of the ASIC 70, and converts an analog output voltage inputted as a voltage signal from the sensor element 20 according to the oxygen concentration in the exhaust gas into a digital value. Then, air-fuel ratio control is performed in the microcomputer 60. The heater control unit 61 inputs the resistance value of the sensor element 20 as a digital signal by the A / D converter 62, outputs a PWM control drive signal to the heater driver 50, and supplies power to the linear A / F sensor 10. To control.

The ASIC 70 is an application specific integrated circuit that integrates a circuit for performing drive control of the linear A / F sensor 10 into one chip and can be easily incorporated into the electronic control device 100. The ASIC 70 outputs the detection result of the oxygen concentration of the gas detection element 30 detected by supplying power to the gas detection element 30 to the microcomputer 60.
Specifically, the ASIC 70 mainly includes an Rpvs measurement circuit 71, a PID control circuit 72, a target voltage setting unit 73 set as a control target voltage (450 mV), an Ip output circuit 74, a VRPVS output sample and hold circuit 75, an operational amplifier OP1, It is composed of OP2.

  The Rpvs measurement circuit 71 detects the element resistance value Rpvs of the Vs cell 32 based on a change in potential generated at the Vs + port by allowing a constant current to flow through the Vs cell 32 every predetermined time for a predetermined short time. The PID control circuit 72 compares the voltage (electromotive force) Vs generated between the pair of electrodes of the Vs cell 32 with a control target voltage (for example, 450 mV) determined in advance by the target voltage setting unit 73, thereby comparing the Ip cell 31. A signal for controlling the direction and the magnitude of the pump current Ip that is passed through is output. The target voltage setting unit 73 generates a reference voltage (for example, 450 mV) that is a control target of the pump current Ip. The Ip output circuit 74 amplifies the potential difference generated at both ends of the detection resistor R4 when the pump current Ip flows, and outputs it to the A / D converter 62 of the microcomputer 60. The VRPVS output sample hold circuit 75 holds the element resistance value Rpvs of the Vs cell 32 detected by the Rpvs measurement circuit 71 and outputs the potential difference ΔVs generated at the Vs + port.

  The outline of the function of the ASIC 70 is as follows. A minute constant current Icp is passed through the Vs cell 32 of the gas detection element 30, and the electrode connected to the Vs cell 32 is caused to function as a reference electrode. The ASIC 70 detects the electromotive force Vs generated between the pair of electrodes of the Vs cell 32 and compares it with a predetermined reference voltage (for example, 450 mV). The ASIC 70 controls the direction and magnitude of the pump current Ip that flows between the pair of electrodes of the Ip cell 31 based on the comparison result. The Ip cell 31 pumps oxygen or pumps oxygen depending on the direction and magnitude of the pump current Ip. Further, in the ASIC 70, the Rpvs measurement circuit 71 detects a change in the resistance value of the gas detection element 30 that changes in accordance with the temperature, and outputs the change to the microcomputer 60.

  The heater driver 50 applies a voltage Vh from the battery to both ends of the heating resistor 41 of the heater 40. The heater driver 50 turns on and off by applying PWM (pulse width modulation) control to energize the heating resistor 41. The heater controller 61 of the microcomputer 60 calculates the duty ratio of the voltage waveform of the voltage Vh applied to both ends of the heating resistor 41. In the specific calculation, the heater control unit 61 calculates the duty ratio based on the resistance value change according to the heating state of the Vs cell 32 detected by the ASIC 70. The heater control unit 61 outputs a pulse signal to the heater driver 50 according to the duty ratio calculation result. The heater driver 50 applies the voltage Vh having a voltage waveform corresponding to the duty ratio to the heating resistor 41 based on the pulse signal output from the heater control unit 61 to heat the Ip cell 31 and the Vs cell 32.

Next, an operation for detecting the oxygen concentration (air-fuel ratio) of the exhaust gas using the linear A / F sensor 10 will be briefly described.
First, the voltage (electromotive force) Vs generated between the pair of electrodes of the Vs cell 32 is compared with 450 mV, which is set as a control target voltage of the voltage Vs for bringing the air-fuel ratio of the exhaust gas close to the stoichiometric air-fuel ratio, and detected. It is fed back to the operational amplifier OP1 through the resistor R4. That is, the direction and magnitude of the pump current Ip flowing through the Ip cell 31 is controlled by the PID control circuit 72 and the operational amplifier OP1, so that the air-fuel ratio of the exhaust gas in the gas detection element 30 becomes the stoichiometric air-fuel ratio. The cell 31 pumps or pumps oxygen.

Specifically, when the air-fuel ratio of the exhaust gas flowing into the gas detection element 30 is richer than the stoichiometric air-fuel ratio, since the oxygen concentration in the exhaust gas is thin, the solid electrolyte body of the gas detection element 30 is externally attached. The pump current Ip is energized and controlled so that oxygen is pumped into the gas detecting element 30 through.
On the other hand, when the air-fuel ratio of the exhaust gas flowing into the gas detection element 30 is leaner than the stoichiometric air-fuel ratio, a large amount of oxygen exists in the exhaust gas, so oxygen is released from the gas detection element 30 to the outside. The pump current Ip is energized to be pumped out.

  At this time, the pump current Ip flowing through the Ip cell 31 flows through the detection resistor R4. The Ip output circuit 74 converts the pump current Ip (potential difference between both ends of the detection resistor R4) into a voltage and outputs it as an output (detection signal) of the linear A / F sensor 10 to the A / D converter 62 of the microcomputer 60. In the microcomputer 60, the oxygen concentration contained in the exhaust gas, and hence the air-fuel ratio of the exhaust gas, is detected from the magnitude and direction of the pump current Ip obtained as the detection signal.

  By the way, in order to obtain a stable detection result of the oxygen concentration, the gas detection element 30 is heated and activated until the solid electrolyte body of the gas detection element 30 reaches an activation temperature or higher (for example, 750 ° C.). It is necessary to perform control to keep the temperature of the gas detection element 30 constant thereafter. As described above, the heater driver 50 energizes the heating resistor 41 of the heater 40 that heats the gas detection element 30 by PWM control according to the duty ratio calculated by the heater control unit 61 of the microcomputer 60. Since the battery voltage is applied to the heater 40, there is a possibility that noise may be generated when the energization of the heater 40 is switched on / off by PWM control. There is also a risk of being affected by external noise. When noise occurs, the reference potential of the electronic control device 100 changes.

  The element resistance value Rpvs of the Vs cell 32 is detected by the Rpvs measurement circuit 71 by detecting a change in the potential generated at the Vs + port by passing a constant current for a predetermined short time every predetermined time, and is held by the VRPVS output sample hold circuit 75. It is obtained based on the potential difference ΔVs output above. For this reason, when the element resistance value Rpvs of the Vs cell 32 is affected by noise, the element resistance value Rpvs may be higher than the element resistance value Rpvs that does not include the original noise depending on the timing at which the noise occurs. It may be a low value. That is, the element resistance value Rpvs with superimposed noise when the heater 40 is energized and the element resistance value Rpvs with superimposed noise when off may both be higher or lower than the original values, respectively. May be high and low.

  For example, when the VRPVS output sample hold circuit 75 holds the potential difference ΔVs, there is no influence of noise, and when the potential difference ΔVs is output to the heater control unit 61, the heater 40 is turned on and the reference potential becomes high. The element resistance value Rpvs acquired by the heater control unit 61 may be lower than the original value. Further, for example, the energization of the heater 40 is turned on, and the potential difference ΔVs becomes larger than the original value due to the influence of instantaneous noise generated at that time, and the value is held by the VRPVS output sample hold circuit 75. If the potential difference ΔVs is output to the heater control unit 61 before being affected and increased, the Rpvs acquired by the heater control unit 61 may be higher than the original value.

  Further, for example, although the energization of the heater 40 is turned off and the VRPVS output sample hold circuit 75 holds the potential difference ΔVs at a value larger than the original due to the influence of instantaneous noise generated at that time, the potential difference ΔVs is stored in the heater control unit 61. In the case where the reference potential is not affected when the voltage is output, the element resistance value Rpvs acquired by the heater control unit 61 may be higher than the original value. However, depending on the timing at which noise occurs, even when the reference potential varies, the VRPVS output sample hold circuit 75 outputs the potential difference ΔVs to the heater control unit 61 when the VRPVS output sample hold circuit 75 holds the potential difference ΔVs. In some cases, the reference potential is the same and the potential difference ΔVs, which is the difference, does not affect the noise.

The present invention provides a heater control device for a gas concentration sensor in which the measured value of the resistance of the gas detection element 30 associated with the on / off switching of the heater 40 is not affected by noise. Is described below.
Embodiment 1 FIG.
In the first embodiment of the present invention, as shown in FIG. 2, the resistance value detection cycle of the gas detection element 30 is set to 120 msec, for example, and the drive cycle of the heater 40 is periodically calculated and set to be variable. The heater 40 is controlled so that the on / off switching does not continuously overlap with the timing of detecting the resistance value of the gas detection element 30.
Specifically, the heater control unit 61 includes a process for periodically updating the heater driving cycle. In general, in PWM control, it is possible to update the cycle information and duty information set in the heater control unit 61 at the same time at the end timing of the cycle, and asynchronously with the actual drive in order to realize this setting. In addition, the period information and the duty information are stored in predetermined variables.

The heater controller 61 detects the resistance detection period of the gas detection element 30 and the heater 40 so that the detection period of the resistance value of the gas detection element 30 and the drive period of energization to the independently operating heater 40 do not always synchronize. The driving cycle of the heater 40 is set so that the number of times of tuning with the driving cycle is minimized within a predetermined time. The above-mentioned tuning is synonymous with synchronization.
In addition, when setting the calculation of the driving cycle of the heater 40, the upper and lower limits of the driving cycle of the heater 40 are defined from the characteristics of the gas detection element 30 due to the influence of temperature change, etc. Can be minimal. For example, the driving cycle upper limit value of the heater 40 is set to 16 msec, and the driving cycle lower limit value of the heater 40 is set to 13 msec. By setting the drive cycle upper limit value and lower limit value, it is possible to reduce the influence of the gas detection element 30 on the temperature change.

  As described above, according to the first embodiment, the heater 40 is periodically calculated and set so that the drive period of the heater 40 does not always synchronize with the detection period of the resistance value of the gas detection element 30. On / off switching of the heater 40 can be controlled so that it does not continuously overlap with the timing of detecting the resistance value of the gas detection element 30, and the influence of noise accompanying the on / off switching of the heater 40 is continuously maintained. The resistance value of the gas detection element 30 can be detected so as not to be received.

Embodiment 2. FIG.
In the second embodiment of the present invention, when the driving cycle of the heater 40 is a fixed cycle, the heater driving cycle is smaller than the upper limit value of the heater driving cycle, as shown in the flowchart of FIG. The least common multiple of the value detection cycle and the heater 40 drive cycle is calculated and set as a fixed cycle with a maximum value that is a product of the resistance detection cycle of the gas detection element 30 and the fixed cycle that is the drive cycle of the heater 40 as a fixed cycle. It is what I did.

FIG. 3 is a flowchart showing a method for calculating a fixed period in heater driving in the second embodiment.
In FIG. 3, step S31 sets a predetermined upper limit value (for example, 16 msec) as an initial value of a fixed period in energization driving of the heater 40. In step S32, the least common multiple of the resistance detection cycle of the gas detection element 30 and the heater drive cycle has a multiplication value of the element resistance detection cycle and the heater drive cycle (the element resistance detection cycle and the heater drive cycle have the same divisor other than 1). No). In step S33, when the least common multiple of the element resistance detection period and the heater driving period is a product of the element resistance detection period and the heater driving period (YES) in step S32, 13 msec which is the maximum heater driving period is calculated and set. The In step S34, when the least common multiple of the element resistance detection period and the heater driving period is not a product of the element resistance detection period and the heater driving period in step S32 (NO), the value is obtained by subtracting 1 msec from the driving period upper limit value 16 msec. The heater driving cycle is reset and the process returns to step S32.

In the above-described step S32 to step S34, it will be described that the maximum that the least common multiple of the measurement period is fixed period × measurement period is 13 msec as follows.
0) When the fixed period is 16 msec ⇒The least common multiple of the measurement period of 120 msec is not fixed period x measurement period.
1) When the fixed period is 15 msec ⇒The least common multiple of the measurement period of 120 msec is not fixed period x measurement period.
2) When the fixed cycle is 14 msec ⇒ The least common multiple of the measurement cycle of 120 msec does not become fixed cycle x measurement cycle.
3) When the fixed period is 13 msec => Since the least common multiple of the measurement period of 120 msec is fixed period x measurement period, the maximum multiplication value is 13 msec.
As described above, in the second embodiment, when the heater driving cycle is determined so that the resistance detection cycle and the heater driving cycle are not always synchronized, the driving cycle is always fixed to the value within a predetermined time. The expected value of the number of tunings of the resistance value detection cycle of the gas detection element 30 and the driving cycle of the heater 40 can be minimized.

表１に設定したデータに基づいて動作させた場合、ヒータ駆動周期は４つの周期デー
タがテーブル番号順に周期的に変更されるものとなる。 Embodiment 3 FIG.
In the third embodiment of the present invention, when the driving cycle of the heater 40 is a variable cycle, the heater driving cycle can be varied by a table.
In this embodiment, the resistance value detection cycle of the gas detection element 30 is set to 120 msec. Set to. The upper limit value of the driving cycle of the heater 40 was set to 16 msec, and the number of data in the variable cycle setting table was set to 4. As an example, as shown in Table 1 below, four drive cycle data are set between 16 msec and 15 msec by subtracting 1 msec from the drive cycle of 16 msec.

When the operation is performed based on the data set in Table 1, the heater driving cycle is such that four cycle data are periodically changed in the order of the table numbers.

  As shown in the flowchart of FIG. 4, regarding the calculation setting of the table elements, the least common multiple of the total value of all table elements (drive cycle) and the element resistance detection cycle is the element resistance detection cycle and all table elements (drive cycle). ) Is calculated and set so as to be a multiplication value with the total value, and each element (drive cycle) is set to be equal to or less than the upper limit value of the heater drive cycle.

FIG. 4 is a flowchart showing a variable period calculation method in heater driving in the third embodiment.
In FIG. 4, step S41 sets the upper limit value (for example, 16 msec) prescribed | regulated by each table data as an initial value of the variable period in heater drive. In step S42, the least common multiple of the sum of the resistance detection period of the gas detection element 30 and the drive period of all table data is a product of the resistance detection period of the gas detection element 30 and the sum of the drive periods of all table data (detection). It is determined whether or not the cycle and the total value of all table data match the same divisor other than 1). In step S43, when the least common multiple is a multiplication value of the resistance detection cycle of the gas detection element 30 and the total value of the drive cycles of all table data in step S42 (YES), the maximum heater drive cycle of 16 msec is calculated. Is set. In step S44, if the least common multiple is not a product of the element resistance detection cycle and the total value of all table data in step S42 (NO), the drive cycle upper limit value 16 msec is periodically changed in the order of the numbers in the table data. Then, the drive cycle is reset to a value obtained by subtracting 1 msec from step S42, and the process returns to step S42.

Regarding the setting of the variable cycle of the heater drive, it is possible to update the drive cycle to a desired value by monitoring the change in the actual drive cycle in the processing that is periodically executed. Specifically, this is performed according to the flowchart shown in FIG.
FIG. 5 is a flowchart showing a heater driving cycle setting method. In step S51, in the regular processing, whether the actual heater driving cycle matches the stored value (stored value of the table data) set in the monitoring processing. to decide. In step S52, if the heater driving cycle matches the stored value (YES), it is determined that the cycle has been updated in the actual driving process, and the next driving cycle is updated by incrementing the number of the table data (up to the final number). If it does, it will return to the top number). In step S53, the next drive cycle is calculated and set using preset table data. Thereafter, the stored value is updated to this set value.

In steps S42 to S44, the least common multiple of the total value of elements (drive cycle) and the measurement cycle matches the total value of the drive cycle × measurement cycle as follows: 16 msec, 15 msec, 15 msec, A description will be given of the fact that the heater driving cycle is variable such as 15 msec.
0) When the table data is (16, 16, 16, 16) ⇒ Because the total is 64, the least common multiple with the measurement cycle of 120 msec does not equal the total value × measurement cycle.
1) When the table data is (16, 16, 16, 15) ⇒ Because the total is 63, the least common multiple with the measurement cycle of 120 msec does not equal the total value × measurement cycle.
2) When the table data is (16, 16, 15, 15) ⇒ Because the total is 62, the least common multiple with the measurement cycle of 120 msec does not equal the total value × measurement cycle.
3) When the table data is (16, 15, 15, 15) ⇒ Because the total is 61, the least common multiple with the measurement cycle of 120 msec is the total value × measurement cycle.

In the third embodiment, the next drive cycle is calculated by regular processing, but a time drive cycle may be set at the end of the drive cycle.
In the setting of the variable period in the third embodiment, the driving period is calculated and set using preset table data, but an arbitrary driving period may be set. However, when the heater driving cycle is a high cycle, the resolution is insufficient depending on the driving duty, and there is a concern that the heater is not driven at the set driving duty.
Further, when the heater driving cycle is low, there is a concern that the influence of the thermal response becomes large and the element resistance is not normally detected. Therefore, by defining the upper limit value and the lower limit value of the drive cycle within a range that does not greatly affect the temperature change of the gas detection element 30, the above-described effects can be obtained in the same manner.

Embodiment 4 FIG.
The fourth embodiment of the present invention combines the case where the heater driving cycle is the fixed cycle of the second embodiment and the variable cycle of the third embodiment.
That is, when calculating and setting the heater driving cycle, the fixed cycle with the smallest number of tunings within a predetermined time with the resistance detection cycle of the gas detection element 30 and the average value of each element of the variable cycle set in the table The longer cycle is set as the heater driving cycle.
For example, since the table data average value of the variable period is 15.25 msec with respect to the fixed period of 13 msec, a longer variable period is selected and set as the heater driving period. Thereby, the expected value of the number of times of tuning of the element resistance detection period and the heater driving period within a predetermined time can be minimized.

  In the above-described embodiment, the heater control device is an automobile electronic control device (ECU), but a control device independent of the ECU may be provided. As an example of the gas concentration sensor, a linear A / F sensor has been described. However, a gas concentration sensor including a gas detection element having a solid electrolyte body as a base and a heater element for heating the solid electrolyte body to achieve early activation, for example, You may apply to an oxygen sensor, NOx sensor, HC sensor, etc.

  In the above embodiment, when detecting the element resistance value, detection is performed using a voltage change when a current of a specific magnitude is supplied to a specific cell (Vs cell in the above embodiment). However, it may be detected using a change in current when a voltage of a specific magnitude is applied to a specific cell. The specific cell for detecting the element resistance value is not limited to the Vs cell, and may be another cell (Ip cell in the above embodiment).

  Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various design changes can be made. Within the scope of the present invention, each embodiment is described. These embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

10: Linear A / F sensor, 20: Sensor element, 30: Gas detection element,
31: Ip cell, 32: Vs cell, 40: heater, 41: heating resistor,
50: Heater driver, 60: Microcomputer, 61: Heater control unit,
62: A / D converter, 70: ASIC, 71: Rpvs measurement circuit,
72: PID control circuit 73: Target voltage setting device 74: Ip output circuit
75: VRPVS output sample and hold circuit 100: Electronic control unit (ECU)

A heater control device for a gas concentration sensor according to the present invention includes a gas detection element including at least one cell having a solid electrolyte body and a pair of electrodes provided on the solid electrolyte body, and heating the gas detection element to activate the gas detection element. A heater control device for controlling energization to a heater of a gas concentration sensor comprising a heater for generating gas, so that the detection cycle of the resistance value of the gas detection element and the drive cycle of energization to the heater are not always synchronized. The heater drive cycle is calculated and set so that the number of tunings between the element resistance value detection cycle and the heater drive cycle is minimized within a predetermined time, and the heater drive cycle is set for the heater drive cycle calculation setting. When the fixed period is set, the heater driving period is the least common multiple of the resistance detection period of the gas detection element and the fixed period, and the resistance detection period of the gas detection element is It is obtained so as to set the maximum value as the multiplication value of the constant period.

Calculation setting table elements, as shown in the flowchart of FIG. 4, the minimum common multiple is the element resistance detection period and the total table elements (drive cycle of the sum and the element resistance detection cycle of all table elements (drive cycle) ) Is calculated and set so as to be a multiplication value with the total value, and each element (drive cycle) is set to be equal to or less than the upper limit value of the heater drive cycle.

FIG. 4 is a flowchart showing a variable period calculation method in heater driving in the third embodiment.
In FIG. 4, step S41 sets the upper limit value (for example, 16 msec) prescribed | regulated by each table data as an initial value of the variable period in heater drive. Step S42 is the smallest common multiple of the sum of the resistance detection period and the driving period of the entire table data of the gas detection element 30, the multiplication value of the sum of the resistance detection period and the driving period of the entire table data of the gas detection element 30 (detection It is determined whether or not the cycle and the total value of all table data match the same divisor other than 1). In step S43, when the least common multiple is a multiplication value of the resistance detection cycle of the gas detection element 30 and the total value of the drive cycles of all table data in step S42 (YES), the maximum heater drive cycle of 16 msec is calculated. Is set. In step S44, if the least common multiple is not a product of the element resistance detection cycle and the total value of all table data in step S42 (NO), the drive cycle upper limit value 16 msec is periodically changed in the order of the numbers in the table data. Then, the drive cycle is reset to a value obtained by subtracting 1 msec from step S42, and the process returns to step S42.

Claims (5)

  The gas concentration sensor comprising: a solid electrolyte body and a gas detection element including at least one cell having a pair of electrodes provided on the solid electrolyte body; and a heater that heats and activates the gas detection element A heater control device for controlling energization to a heater, wherein a detection cycle of a resistance value of the gas detection element and a detection cycle of a resistance value of the gas detection element so that a drive cycle of energization to the heater is not always synchronized. A heater control device for a gas concentration sensor, wherein the heater driving cycle is set such that the number of times of tuning between the heater and the heater driving cycle is minimized within a predetermined time.   2. The heater control device for a gas concentration sensor according to claim 1, wherein an upper limit value and a lower limit value of the heater drive cycle are defined when an arbitrary drive cycle is set when calculating and setting the drive cycle of the heater.   When setting the heater drive cycle to be a fixed cycle, the heater drive cycle has a least common multiple of the resistance detection cycle of the gas detection element and the fixed cycle. The heater control apparatus for a gas concentration sensor according to claim 1 or 2, wherein a maximum value that is a product of the resistance detection period and the fixed period is set.   When setting the heater drive cycle to be a variable cycle, the heater drive cycle includes a variable cycle setting table having a plurality of drive cycles, and each drive cycle of the variable cycle setting table includes the gas detection element. The least common multiple of the resistance detection cycle and the total value of all the drive cycles in the variable cycle setting table is a product of the resistance detection cycle of the gas detection element and the total value of all the drive cycles in the variable cycle setting table. The heater control device for a gas concentration sensor according to claim 1 or 2, wherein the heater control device is set as follows. When setting the calculation of the heater driving cycle, a fixed cycle with the smallest number of times of tuning within a predetermined time with the resistance detection cycle of the gas detection element in the range of the upper and lower limit values of the heater driving cycle, and the gas detection element Each of the driving cycles in the variable cycle setting table having the smallest number of tunings within a predetermined time with the resistance detection cycle is calculated, and among the average value of the driving cycles in the variable cycle setting table and the fixed cycle, the cycle The heater control device for a gas concentration sensor according to claim 4, wherein the longer one is set as a heater driving cycle.

Images