WO2015194108A1

WO2015194108A1 - Control device

Info

Publication number: WO2015194108A1
Application number: PCT/JP2015/002788
Authority: WO
Inventors: 攻田中
Original assignee: 株式会社デンソー
Priority date: 2014-06-20
Filing date: 2015-06-02
Publication date: 2015-12-23
Also published as: JP2016006384A

Abstract

This control device (40) is provided with a first reception unit (411) that receives a detection signal outputted by a first sensor (20) that contains a first heater (22) and detects the state of an exhaust gas passing a first position (111a) in an exhaust passage (110), a second reception unit (412) that receives a detection signal outputted by a second sensor (30) that contains a second heater (32) and detects the state of the exhaust gas passing a second position (112a) that is different from the aforementioned first position (111a), a power supply unit (42) that supplies power to the first heater (22) and the second heater (32), and a control unit (43) that controls the power supply unit (42) such that said power supply unit (42) starts supplying power to the second heater (32) at a second point in time at which a given delay has elapsed since a first point in time at which the power supply unit (42) started supplying power to the first heater (22).

Description

Control device

Cross-reference of related applications

This application is based on Japanese Patent Application No. 2014-126839 filed on June 20, 2014, the contents of which are incorporated herein by reference.

The present disclosure relates to a control device that detects the state of exhaust gas flowing through an exhaust passage connected to an internal combustion engine.

For example, an internal combustion engine such as an automobile gasoline engine discharges exhaust gas generated by combustion of fuel to the outside. Since exhaust gas contains particulate matter such as nitrogen oxide and carbon monoxide, an internal combustion engine is generally equipped with a control device that optimizes the air-fuel ratio so that the particulate matter is reduced. Such a control device adjusts the fuel supply amount and the air supply amount to the internal combustion engine while detecting the exhaust gas state by a sensor, thereby bringing the air-fuel ratio closer to the theoretical air-fuel ratio (for example, the following patents) Reference 1).

As the above sensor, an A / F sensor or an O ₂ sensor is often used. These are sensors that are attached to an exhaust passage, which is a flow path through which exhaust gas flows, and output an electrical signal corresponding to a difference in oxygen concentration inside and outside the exhaust passage. Each of the A / F sensor and the O ₂ sensor includes a solid electrolyte and a heater that heats and activates the solid electrolyte.

The A / F sensor outputs an electric signal that changes continuously according to the oxygen concentration in the exhaust passage. Therefore, highly accurate control according to the change of the air-fuel ratio is possible. On the other hand, the O ₂ sensor outputs an electric signal that changes stepwise with the oxygen concentration at the stoichiometric air-fuel ratio as a boundary.

For example, the A / F sensor is disposed at a position upstream of the catalytic converter that purifies the exhaust gas in the exhaust passage, and the O ₂ sensor is disposed at a position downstream of the catalytic converter. Can be controlled with high accuracy. In this configuration, it is also possible to detect performance deterioration of the catalytic converter. As described above, the above-described sensors (A / F sensors and O ₂ sensors) are generally arranged in the exhaust passage instead of only one.

JP 2000-97902 A

When detecting the state of exhaust gas, the A / F sensor or O ₂ sensor activates the solid electrolyte by raising the temperature of the solid electrolyte due to the heat generated by the heater, that is, oxygen ions pass through the solid electrolyte. It is necessary to maintain a state that can The control device for an internal combustion engine includes a power supply unit that supplies power to a heater of the sensor. When a plurality of sensors are arranged in the exhaust passage, power is supplied from the power supply unit to the plurality of heaters.

At the start of the control device (for example, at the start of the internal combustion engine), power supply from the power supply unit to each heater is started. However, the power supply unit may break down when the power supply is started. There is sex. Since the current flowing through the power supply unit is the sum of the currents flowing through the heaters, from the viewpoint of avoiding failure of the power supply unit, even if a current that overlaps the currents that can flow through the heaters flows, it will not fail. It is necessary to set the allowable current value of the power supply unit. However, the conventional control apparatus does not consider the countermeasures against the failure of the power supply unit.

The present disclosure has been made in view of such a problem, and an object of the present disclosure is a control device that detects a state of exhaust gas flowing through an exhaust passage connected to an internal combustion engine, and supplies power to the sensor at startup. It is in providing the control apparatus which can suppress that a part breaks down.

In the first aspect of the present disclosure, the control device includes a first heater that generates heat when supplied with electric power, and detects a state of exhaust gas that passes through a first position of an exhaust passage connected to the internal combustion engine. State of exhaust gas passing through a second position different from the first position in the exhaust passage, having a first receiver that receives a detection signal output from one sensor and a second heater that generates heat upon receiving power supply A second receiving unit that receives a detection signal output from the second sensor that detects the power, a power supply unit that supplies power to the first heater and the second heater, and a first unit that starts supplying power to the first heater And a control unit that controls the power supply unit to start supplying power to the second heater at a second time when the delay time has elapsed from one time.

As a specific countermeasure against the failure of the power supply unit, select the components of the power supply unit so that the allowable current value of the power supply unit is larger than the total current that can flow to all heaters. In some cases, a protective circuit is provided. However, such a countermeasure is not preferable because the component cost of the power supply unit becomes large. In particular, when the number of sensors increases, the allowable current to be secured is added by that number, so that the component cost of the power supply unit jumps. Moreover, since it is necessary to reconfigure | reconfigure a power supply part so that it can endure the total current, whenever a sensor number increases, a versatile control apparatus cannot be comprised.

Therefore, the present disclosure paid attention to the fact that the current flowing through the power supply unit when starting the control device is instantaneous. When the control device is activated, the currents flowing through the first heater and the second heater increase instantaneously, and thereafter decrease over time to reach a steady state. Therefore, the present disclosure has been conceived using this temporal change. . In the present disclosure made based on such knowledge, power supply from the power supply unit to the first heater and the second heater is started not at the same time but at different timings. At the start of power supply to the first heater, a large current is output from the power supply unit to the first heater, but the current decreases as the delay time elapses. The power supply to the second heater is started after the delay time has elapsed, that is, after the current output from the power supply unit has decreased. Therefore, the first maximum current that is the maximum current that flows to the first heater at the start of power supply and the second maximum current that is the maximum current to flow to the second heater at the start of power supply are the power supply. Are not output simultaneously from the unit.

According to the present disclosure, the current output from the power supply unit can always be smaller than the sum of the first maximum current and the second maximum current. For this reason, even if the allowable current value of the power supply unit is not excessively increased, it is possible to suppress the failure of the power supply unit during startup.

By the way, considering that exhaust gas is discharged immediately after the start of the internal combustion engine, power supply to the first heater and the second heater is started at the earliest possible timing to detect the state of the exhaust gas early. It is desirable to start on. However, if the delay time is too short, the current starts to be supplied to the second heater in a state where the current flowing through the first heater is only slightly lower than the first maximum current. As a result, the current output from the power supply unit may exceed the allowable current value.

Therefore, in the present disclosure, the upper limit value that is the upper limit current value within a range in which the sum of the current value flowing through the first heater and the current value flowing through the second heater at the second time does not interfere with the power supply unit. It is preferable that the delay time is determined so as not to exceed. According to such an aspect, the delay time can be shortened as much as possible within a range where the power supply unit does not fail at the time of startup, and the exhaust gas state detection can be started early.

According to the present disclosure, it is a control device that detects the state of exhaust gas flowing through an exhaust passage connected to an internal combustion engine, and is capable of suppressing a failure of a power supply unit to the sensor during startup. An apparatus can be provided.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a schematic diagram illustrating a state in which a control device according to an embodiment of the present disclosure is attached to an internal combustion engine and an exhaust system connected thereto. FIG. 2 is a graph showing the time change of the voltage applied to the heater and the time change of the current supplied to the heater in the control device shown in FIG. FIG. 3 is a graph showing the change over time of the current supplied to the heater in the control device shown in FIG. FIG. 4 is a graph showing the time change of the voltage applied to the heater and the time change of the current supplied to the heater in the control device shown in FIG. FIG. 5 is a flowchart showing the operation of the control device shown in FIG. FIG. 6 is a diagram showing the relationship between the heater temperature and the set delay time. FIG. 7 is a diagram showing the relationship between the temperature of the cooling water for cooling the internal combustion engine and the set delay time, FIG. 8 is a graph showing the time change of the voltage applied to the heater and the time change of the current supplied to the heater in the conventional control device.

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

The internal combustion engine 100 that is a control target of the control system 10 including the control device 40 according to the embodiment of the present disclosure is a spark ignition type automobile gasoline engine. As schematically shown in FIG. 1, an intake pipe 101 and an exhaust pipe 110 are connected to the internal combustion engine 100. The exhaust pipe 110 forms an exhaust passage.

The intake pipe 101 is a pipe that supplies an air-fuel mixture in which air and fuel are mixed to the internal combustion engine 100. A throttle valve (not shown) for adjusting the amount of air supplied into the intake pipe 101 and a fuel injection valve (not shown) for adjusting the amount of fuel supplied into the intake pipe 101 are attached to the intake pipe 101. Yes. The amount of air supplied into the intake pipe 101 changes depending on the opening of the throttle valve, and the amount of fuel supplied into the intake pipe 101 changes depending on the opening time of the fuel injection valve. The control device 40 performs control to bring the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 100 closer to the stoichiometric air-fuel ratio by mainly adjusting the supply amount of fuel injected from the fuel injection valve.

The exhaust pipe 110 is a pipe connected to the internal combustion engine 100, and is an exhaust passage that discharges exhaust gas generated by fuel combustion in the internal combustion engine 100 to the outside. The exhaust pipe 110 includes an upstream pipe 111 that is an upstream pipe, a downstream pipe 112 that is a downstream pipe, and a catalytic converter 120. The catalytic converter 120 is disposed between the upstream pipe 111 and the downstream pipe 112. Exhaust gas generated in the internal combustion engine 100 flows through the upstream pipe 111, the catalytic converter 120, and the downstream pipe 112 in this order, and then is discharged to the outside from an exhaust port 114 that is an opening formed at the downstream end of the downstream pipe 112. Is done.

The catalytic converter 120 purifies particulate matter contained in the exhaust gas by oxidation or reduction, and has a catalyst carrier 121 carrying platinum, palladium, and rhodium as catalysts. Hydrocarbons, carbon monoxide, and nitrogen oxides contained in the exhaust gas are purified by touching these catalysts, and then flow through the downstream pipe 112 and are discharged to the outside through the discharge port 114.

The control system 10 includes a first sensor 20, a second sensor 30, a water temperature sensor 70, an air temperature sensor 80, and a control device 40. The first sensor 20 is an A / F sensor that detects the state of exhaust gas (oxygen concentration) generated in the internal combustion engine 100, and is provided at the first position 111 a of the upstream pipe 111. The first sensor 20 is an A / F sensor having a general configuration, and includes a plate-shaped solid electrolyte 21 and a ceramic heater 22 (first heater) for heating the solid electrolyte 21.

A detection electrode is disposed on the first surface of the solid electrolyte 21, and the exhaust gas in the upstream pipe 111 passes through the porous body and reaches the surface. A reference electrode is formed on the second surface of the solid electrolyte 21, and a gas having a reference oxygen concentration, that is, the atmosphere reaches the surface. When the state of the exhaust gas is detected by the first sensor 20, the solid electrolyte 21 is heated to a high temperature by the ceramic heater 22, that is, activated so as to allow oxygen ions to pass therethrough. Maintained. A voltage is applied between the detection electrode and the reference electrode. In such a state, when a difference (concentration difference) occurs between the oxygen concentration inside the upstream pipe 111 and the oxygen concentration outside (atmosphere), a current having a magnitude approximately proportional to the concentration difference is detected between the detection electrode and the reference. It flows between the electrodes (solid electrolyte 21). That is, a larger current flows as the oxygen concentration of the exhaust gas in the upstream pipe 111 is higher. The first sensor 20 generates an electrical signal based on this current and outputs it as a detection signal to the control device 40. Alternatively, the current itself may be directly input to the control device 40 as a detection signal. When receiving the detection signal, control device 40 calculates the air-fuel ratio based on the relationship between the current value stored in advance and the air-fuel ratio. Thus, the 1st sensor 20 is a sensor which outputs the electric signal which changes continuously according to the oxygen concentration inside the upstream piping 111. FIG.

The second sensor 30 is an O ₂ sensor that detects the state (oxygen concentration) of the exhaust gas after passing through the catalytic converter 120, and is provided at the second position 112 a of the downstream pipe 112. The second sensor 30 is an O ₂ sensor having a general configuration, and includes a solid electrolyte 31 formed in a plate shape and a ceramic heater 32 (second heater) for heating the solid electrolyte 31.

Detecting electrodes are arranged on the first surface of the solid electrolyte 31, and the exhaust gas in the downstream pipe 112 passes through the porous body and reaches the surface. Further, a reference electrode is formed on the second surface of the solid electrolyte 31, and a gas having a reference oxygen concentration, that is, the atmosphere reaches the surface. When the state of the exhaust gas is detected by the second sensor 30, the solid electrolyte 31 is heated to a high temperature by the ceramic heater 32, that is, activated so as to allow oxygen ions to pass therethrough. Maintained. A voltage is applied between the detection electrode and the reference electrode. In such a state, a current flows between the detection electrode and the reference electrode (solid electrolyte 31) due to the difference (concentration difference) between the oxygen concentration inside the downstream pipe 112 and the external oxygen concentration. However, when the concentration difference exceeds a predetermined value, the magnitude of the electromotive current changes abruptly (stepwise). The second sensor 30 generates an electrical signal based on this current and outputs it as a detection signal to the control device 40. Alternatively, the current itself may be directly input to the control device 40 as a detection signal. The predetermined value is a value of the oxygen concentration in the downstream pipe 112 when the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 100 is the stoichiometric air-fuel ratio. When receiving the detection signal, the control device 40 compares the current value with a threshold value stored in advance to determine whether or not the oxygen concentration in the downstream pipe 112 is greater than the oxygen concentration at the stoichiometric air-fuel ratio. To do. Thus, the second sensor 30 is a sensor that outputs an electrical signal indicating whether or not the oxygen concentration inside the downstream pipe 112 is higher than the oxygen concentration at the stoichiometric air-fuel ratio.

The internal combustion engine 100 is provided with a radiator (not shown). Cooling water for cooling the internal combustion engine 100 is circulated between the radiator and the internal combustion engine 100. The water temperature sensor 70 is a sensor that detects the temperature of the circulating cooling water.

The temperature sensor 80 is a sensor that measures the temperature of the outside air. The temperature of the cooling water measured by the water temperature sensor 70 and the temperature of the outside air measured by the air temperature sensor 80 are respectively input to the control device 40 described below.

The control device 40 is a computer system including a CPU, a ROM, a RAM, and an input / output interface, and is referred to as a so-called ECU (Engine Control Unit). The control device 40 adjusts the opening degree of the throttle valve and the opening time of the fuel injection valve based on the electrical signal received from the first sensor 20 and the electrical signal received from the second sensor 30. Then, control is performed to bring the air-fuel ratio closer to the theoretical air-fuel ratio. In the present embodiment, the electrical signal received from the first sensor 20 indicates the oxygen concentration in the upstream pipe 111, and the electrical signal received from the second sensor 30 indicates the oxygen concentration in the downstream pipe 112.

The control device 40 includes a signal receiving unit 41, a power supply unit 42, and a control unit 43. The signal receiving unit 41 includes a first receiving unit 411 and a second receiving unit 412. The first receiving unit 411 is an input port that receives an electrical signal output from the first sensor 20. The second receiving unit 412 is an input port that receives an electrical signal output from the second sensor 30. The first receiver 411 and the first sensor 20 are connected by a signal line 51. The electrical signal output from the first sensor 20 is transmitted via the signal line 51 and input to the first receiving unit 411. Similarly, the second receiver 412 and the second sensor 30 are connected by a signal line 61. The electrical signal output from the second sensor 30 is transmitted via the signal line 61 and input to the second receiving unit 412.

The power supply unit 42 is an output port that supplies power necessary for heat generation to each of the ceramic heater 22 of the first sensor 20 and the ceramic heater 32 of the second sensor 30. The power supply unit 42 and the ceramic heater 22 are connected by a power line 52. The power output from the power supply unit 42 is supplied to the ceramic heater 22 via the power line 52. Similarly, the power supply unit 42 and the ceramic heater 32 are connected by a power line 62. The power output from the power supply unit 42 is supplied to the ceramic heater 32 via the power line 62. The power supply to the ceramic heater 22 and the power supply to the ceramic heater 32 can be performed independently (at different timings). The power supply unit 42 is configured to be able to supply power independently to each of the ceramic heater 22 and the ceramic heater 32, but the part that generates the power is shared, A current in which the current flowing through the ceramic heater 22 and the current flowing through the ceramic heater 32 are superimposed flows.

The control unit 43 is a part that forms the center of the control device 40 that is a computer system, and that controls the throttle valve, the fuel injection valve, and the power supply unit 42. The timing at which the voltage is applied to each of the ceramic heater 22 and the ceramic heater 32 and the magnitude of the applied voltage are controlled by the control unit 43.

Referring to FIG. 2, the operation when the control system 10 is started will be described. FIG. 2A is a diagram in which time is taken on the horizontal axis, and voltages applied to the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 2B is a diagram in which time is taken on the horizontal axis, and currents flowing through the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 2C is a diagram in which time is taken on the horizontal axis and current flowing in the power supply unit 42 is taken on the vertical axis.

2A represents a time change of the voltage applied to the ceramic heater 22 with the power supply from the power supply unit 42. The line G10 illustrated in FIG. Similarly, a line G 20 shown in FIG. 2A represents a change over time in the voltage applied to the ceramic heater 32 as power is supplied from the power supply unit 42.

A line G30 shown in FIG. 2 (B) represents a time change of the current flowing through the ceramic heater 22 in accordance with the power supply from the power supply unit. In this case, this current is the first current. Similarly, a line G 40 shown in FIG. 2B represents a time change of the current flowing through the ceramic heater 32 with the power supply from the power supply unit 42. In this case, this current is the second current. A line G50 shown in FIG. 2C indicates a total current of the first current flowing through the ceramic heater 22 and the second current flowing through the ceramic heater 32, that is, the total output from the power supply unit 42. It represents the change in current over time. In this case, this current is the total current.

When the internal combustion engine 100 is started at time t0, the control system 10 is started at the same time, and supply of electric power to the ceramic heater 22 is started. In the period from time t0 to time t2, a relatively small voltage V ₁₀ is applied to the ceramic heater 22 (see line G10). After time t2, a large voltage V ₂₀ than the voltage V ₁₀ is applied to the ceramic heater 22. The reason why the applied voltage is increased stepwise is to prevent the ceramic heater 22 from being damaged due to a rapid temperature rise.

On the other hand, the supply of power to the ceramic heater 32 is not started at time t0, but is started at time t1 when the delay time td1 has elapsed from time t0. The time t1 is a time before the time t2. Thus, in this embodiment, the supply of power to the ceramic heater 22 and the supply of power to the ceramic heater 32 are not started simultaneously. The reason will be described later.

In the period from time t1 to time t3, a relatively small voltage V ₁₀ is applied to the ceramic heater 32 (see line G20). After time t3, a large voltage V ₂₀ is applied to the ceramic heater 32 than the voltage V _10. The reason why the applied voltage is increased stepwise is to prevent the ceramic heater 32 from being damaged due to a rapid temperature rise. In the present embodiment, the value of the voltage applied to the ceramic heater _{_{22 (V 10, V 20)}} , the value of the voltage applied to the ceramic heater 32 (V _10, V ₂₀₎ and in the equal to each other Only the timing for applying or increasing the voltage is different from each other. However, the value of the voltage applied to each ceramic heater may be different from each other.

Immediately after the internal combustion engine 100 is started, water droplets may adhere to the inner wall surface of the exhaust pipe 110 on the downstream side of the catalytic converter 120 (downstream piping 112). Accordingly, there is a possibility that water droplets are also attached to the ceramic heater 32 provided in the downstream pipe 112. If the temperature of the ceramic heater 32 is greatly increased in a state where water droplets are attached in this way, a large temperature unevenness (temperature difference depending on the location) occurs in the ceramic heater 32, and the ceramic heater 32 is caused to local thermal expansion. There is a risk of breaking.

Therefore, in this embodiment, the time during which the voltage V ₁₀ is applied to the ceramic heater 32 (time from time t1 to time t3) is the time during which the voltage V ₂₀ is applied to the ceramic heater 22 (from time t0). (Time until time t2). Applying a relatively small voltage V ₁₀ long, Evaporation of the water droplets with gentle rise in temperature of the ceramic heater 32, so as to prevent the ceramic heater 32 is cracked as described above. The timing at which the voltage V ₂₀ starts to be applied to the ceramic heater 32 (time t3 in the present embodiment) is a point in time when a certain time (fixed length of time) has elapsed from the time t0 when the internal combustion engine 100 was started. However, it may be the time when the water temperature sensor 70 confirms that the temperature of the cooling water for cooling the internal combustion engine 100 has risen and exceeded a predetermined temperature.

When the voltage V ₁₀ starts to be applied to the ceramic heater 22 at time t0, the first current starts to flow through the ceramic heater 22 (see line G30). At this time, the voltage V ₁₀ to be applied is constant for the first current is not constant from the beginning. At time t0 the voltage V ₁₀ begins to be applied, resulting in a large current (overcurrent) flows through the ceramic heater 22. Thereafter, the first current flowing through the ceramic heater 22 gradually decreases and approaches a substantially constant current. The maximum value of the overcurrent flowing when the voltage V ₁₀ is applied to the ceramic heater 22 (first current at time t0), hereinafter referred to as maximum current I ₁₀ is.

Even when the voltage V ₂₀ starts to be applied to the ceramic heater 22 (time t2), the overcurrent as described above occurs again. At time t2 the voltage V ₂₀ begins to be applied, resulting in overcurrent flows again to the ceramic heater 22 (see line G30). Thereafter, the first current flowing through the ceramic heater 22 gradually decreases and approaches a substantially constant current. The maximum value of the overcurrent flowing when the voltage V ₂₀ is applied to the ceramic heater 22 (first current at time t2), in the following referred to as maximum current I _20.

Similar to the case of the ceramic heater 22, the overcurrent as described above flows also in the ceramic heater 32. When the voltage V ₁₀ starts to be applied to the ceramic heater 32 at time t1, an overcurrent flows through the ceramic heater 32 (see line G40). Thereafter, the second current flowing through the ceramic heater 32 gradually decreases and approaches a substantially constant current.

Even when the voltage V ₂₀ starts to be applied to the ceramic heater 32 (time t3), the overcurrent as described above occurs again. As shown in line G40, at time t3 the voltage V ₂₀ begins to be applied, resulting in overcurrent flows again to the ceramic heater 32. Thereafter, the second current flowing through the ceramic heater 32 gradually decreases and approaches a substantially constant current.

In the present embodiment, the electrical resistance value of the ceramic heater 22 and the electrical resistance value of the ceramic heater 32 are substantially equal to each other. Therefore, the maximum value of the overcurrent flowing when the voltage V ₁₀ is applied to the ceramic heater 32 (second current at time t1) is substantially equal to the maximum current I _10. The maximum value of the overcurrent flowing when the voltage V ₂₀ is applied to the ceramic heater 32 (second current at time t3) is substantially equal to the maximum current I _20.

As described above, overcurrent flows through the ceramic heater 22 at each time point (time t0, t2) when the voltage is applied or increased. Similarly, overcurrent flows through the ceramic heater 32 at each time point (time t1, t3) when the voltage is applied or increased. For this reason, as indicated by a line G50, the total current output from the power supply unit 42 also increases at each of the times t0, t1, t2, and t3 when the overcurrent flows.

Conventionally, such a delay time has not been intentionally set when energizing a pair of heaters. Here, if the delay time td1 becomes 0, in other words, a phenomenon that occurs when power supply to the ceramic heater 22 and power supply to the ceramic heater 32 are started simultaneously at time t0. This will be described with reference to FIG. FIG. 8A is a diagram in which time is taken on the horizontal axis and voltages applied to the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 8B is a diagram in which time is taken on the horizontal axis and currents flowing through the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 8C is a diagram in which time is taken on the horizontal axis and current flowing in the power supply unit 42 is taken on the vertical axis.

A line G12 shown in FIG. 8A represents a time change of the voltage applied to the ceramic heater 22, and is a line that follows the same transition as the line G10 of FIG. Similarly, a line G22 shown in FIG. 8A represents a time change of the voltage applied to the ceramic heater 32, and is a graph obtained by shifting the line G20 of FIG. 2 to the left by the delay time td1. It has become. 8, time t31 the voltage applied to the ceramic heater 32 is changed from the voltage V ₁₀ to the voltage V ₂₀ has a time earlier by a delay time td1 than the time t3 of FIG.

8B represents a time change of the first current flowing through the ceramic heater 22, and follows the same transition as the line G30 in FIG. Similarly, a line G42 shown in FIG. 8B represents a time change of the second current flowing through the ceramic heater 32, and is a graph obtained by shifting the line G40 of FIG. 2 to the left by the delay time td1. It has become. A line G 52 shown in FIG. 8C represents a time change of the total current obtained by adding the first current flowing through the ceramic heater 22 and the second current flowing through the ceramic heater 32.

In conventional control, no special consideration has been given to the supply start timing of power to the

ceramic heaters

22 and 32. For this reason, as shown in FIG. 8, the power supply to the ceramic heater 22 and the power supply to the ceramic heater 32 may be started simultaneously at time t0. In this case, the magnitude of the total current output from the power supply unit 42 at time t0 is the maximum value of the overcurrent flowing through the ceramic heater 22 (maximum current I ₁₀ ) and the maximum value of the overcurrent flowing through the ceramic heater 32 ( The maximum current I ₁₀ ) is superposed, that is, a current twice as large as the maximum current I ₁₀ flows. As a result, a current exceeding the allowable current value I _TH of the power supply unit 42 is output at time t0 (see line G52), and the power supply unit 42 may break down. The allowable current value I _TH is the maximum value of the current that can be output to the outside without failure of the power supply unit 42, and is a specific value determined by the specifications of various electronic components and protection circuits that constitute the power supply unit 42. Value. The allowable current value I _TH is an upper limit current value in a range that does not interfere with the power supply unit.

From the viewpoint of avoiding the failure of the power supply unit 42, conventionally, it has been necessary to set the allowable current value I _TH sufficiently large. Specifically, the components of the power supply unit 42 (for example, such that the allowable current value I _TH is large enough to supply the maximum current I ₁₀ simultaneously to both the ceramic heater 22 and the ceramic heater 32). It was necessary to select a protection circuit. However, such a measure is not preferable because the parts cost of the power supply unit 42 becomes large.

Therefore, in the present embodiment, the power supply unit 42 is broken by devising the timing of power supply to each of the ceramic heater 22 and the ceramic heater 32 instead of increasing the allowable current value I _TH. It is preventing. Specifically, as described with reference to FIG. 2, at time t 1 (second time) when delay time td 1 has elapsed from time t 0 (first time) when supply of power to the ceramic heater 22 is started. Control of the power supply unit 42 by the control unit 43 is performed so as to start supply of power to the heater 32. Such a device for power supply timing is an instantaneous eddy current as described below, and the time when the current flowing through the ceramic heater 22 and the ceramic heater 32 starts to flow (time t0, t2). ), And it was made by paying attention to the point where it gradually decreases.

As shown in FIG. 2B, at time t0, that is, at the start of power supply to the ceramic heater 22, the first current flowing through the ceramic heater 22 becomes the maximum current I ₁₀ , and this time is peaked and thereafter gradually. Decrease (see line G30). The power supply from the power supply unit 42 to the ceramic heater 32 is performed after the delay time td1 has elapsed from time t0 (time t1), that is, the first current output from the power supply unit 42 decreases and the maximum current I ₁₀ is reduced. It starts after becoming smaller.

For this reason, at the start of power supply, the first current flowing through the ceramic heater 22 and the second current flowing through the ceramic heater 32 do not simultaneously reach their maximum values (maximum current I ₁₀ ). As a result, the value of the total current output from the power supply unit 42 is smaller than twice the maximum current I ₁₀ at both time t0 and time t1, and may exceed the allowable current value I _TH. None (see line G50).

As described above, in the control system 10, the current output from the power supply unit 42 has the maximum overcurrent (maximum current I ₁₀ ) flowing through the ceramic heater 22 and the maximum overcurrent (maximum current I ₁₀ ) flowing through the ceramic heater 32. It is always smaller than the superposition of the current I ₁₀ ). For this reason, it is possible to prevent the power supply unit 42 from being damaged by an overcurrent without excessively increasing the allowable current value I _TH of the power supply unit 42.

By the way, considering that exhaust gas is discharged immediately after the internal combustion engine 100 is started, power supply to the ceramic heater 22 and the ceramic heater 32 is started at the earliest possible timing to optimize the air-fuel ratio. It is desirable that control be started early. However, when the delay time td1 is too short, in a state where the current flowing through the ceramic heater 22 is not decreased only slightly from the maximum current I _10, current may begin to be supplied to the ceramic heater 32. As a result, the total current output from the power supply unit 42 may exceed the allowable current value I _TH .

Therefore, the delay time td1 in the present embodiment is set as short as possible within a range in which the total current does not exceed the allowable current value I _TH even when current is supplied to the ceramic heater 32.

That is, the total current at the time when the second current starts to be supplied to the ceramic heater 32 (time t1) is equal to the first current that has decreased during the delay time td1 (as shown in FIG. 2). Current I ₀₇ ) and the second current (maximum current I ₁₀ ), the length of the delay time td 1 is set so that the magnitude is slightly less than the allowable current value I _TH. ing. In other words, when the current value obtained by subtracting the maximum value (maximum current I ₁₀ ) of the second current from the allowable current value I _TH is defined as the upper limit current, the first current decreases from the maximum current I ₁₀ and the upper limit current The length of the delay time td1 is set so as to be a time required for the time to be slightly less than.

The total current at time t2 is the sum of the first current (maximum current I ₂₀ ) at that time and the second current (the magnitude thereof is current I ₀₈ as shown in FIG. 2). Further, the total current at time t3 is the sum of the first current at that time (the magnitude is current I ₀₉ as shown in FIG. 2) and the second current (maximum current I ₂₀ ). . In the present embodiment, the delay time td1 is set to be as short as possible within the range where the total current does not exceed the allowable current value I _TH not only at time t1 but also at time t2 and time t3. Yes. Therefore, while reliably preventing the power supply unit 42 from failing, the temperature of each of the ceramic heater 22 and the ceramic heater 32 is increased at an early stage, and control for optimizing the air-fuel ratio is started at an early stage. Is possible.

The ceramic heater 22 and the ceramic heater 32 are made of metal (tungsten) at the portion where current passes and generates heat. For this reason, the electrical resistance is not always constant, the electrical resistance decreases as the temperature decreases, and the electrical resistance increases as the temperature increases. The magnitude of the first current flowing through the ceramic heater 22 and the magnitude of the second current flowing through the ceramic heater 32 also vary depending on the temperature of the ceramic heater 22 and the temperature of the ceramic heater 32, respectively.

The line G30 shown in FIG. 3 is the same line as the line G30 shown in FIG. 2, and represents the time change of the first current flowing through the ceramic heater 22. Also, the line G31 shown in FIG. 3 is the time change of the first current flowing through the ceramic heater 22, and the time of the first current when the ceramic heater 22 is at a lower temperature than in the case of the line G30. It represents a change. The voltage applied to the ceramic heater 22 is the same as the voltage represented by the line G12 in FIG.

As indicated by the line G31, when the ceramic heater 22 is at a low temperature, the first current flowing through the ceramic heater 22 increases as the electrical resistance decreases. Specifically, the first current at time t0 is larger than the maximum current I ₁₀ (maximum current I ₁₀ a). The first current at time t2 has a large current (maximum current I ₂₀ a) than the maximum current I _20. Furthermore, the first current at the time t1 has a large current (current I ₀₇ a) than the current I _07.

Therefore, when the supply of the second current is started at time t1 as in the case of the line G20 in FIG. 2 when the ceramic heater 22 is at a low temperature, the total current is larger than the current I _07. The maximum value of the second current (maximum current I ₁₀ ) is added to the current I ₀₇ a. As a result, the total current may exceed the allowable current value I _TH at low temperatures.

Further, when the ceramic heater 22 is at a low temperature, the ceramic heater 32 is also at a low temperature, and there is a high possibility that a current easily flows through the ceramic heater 32. Therefore, the possibility that the total current exceeds the allowable current value I _TH is further increased.

Therefore, in this embodiment, the length of the delay time (td1) is not always fixed, but the delay time is set to an appropriate length based on the temperature of the ceramic heater 22 at the start of current supply. Is set. That is, the delay time is set based on the temperature of the ceramic heater 22 so that the delay time is as short as possible within a range where the total current does not exceed the allowable current value I _TH .

FIG. 4 shows the control performed by the control device 40 when the temperature is low, that is, when the outside air temperature is low and the temperature of both the ceramic heater 22 and the ceramic heater 32 is low (than the case of FIG. 2). While explaining. FIG. 4A is a diagram in which time is taken on the horizontal axis, and voltages applied to the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 4B is a diagram in which time is taken on the horizontal axis, and currents flowing through the ceramic heater 22 and the ceramic heater 32 are taken on the vertical axis. FIG. 4C is a diagram in which time is taken on the horizontal axis and current flowing through the power supply unit 42 is taken on the vertical axis.

A line G11 shown in FIG. 4A represents a time change of the voltage applied to the ceramic heater 22 at a low temperature, and follows the same transition as the line G10 in FIG. Similarly, a line G21 shown in FIG. 4A represents a change over time in the voltage applied to the ceramic heater 32 at a low temperature. The waveform of the line G21 is the same as that of the line G20 shown in FIG. 2, but is different from the line G20 at the timing when the voltage starts to be applied to the ceramic heater 32.

A line G31 shown in FIG. 4B represents a time change of the first current flowing through the ceramic heater 22 at a low temperature, and follows the same transition as the line G31 shown in FIG. . Similarly, a line G41 shown in FIG. 4B represents a time change of the second current flowing through the ceramic heater 32 at a low temperature. A line G50 shown in FIG. 4C represents a time change of the total current obtained by adding the first current flowing through the ceramic heater 22 and the second current flowing through the ceramic heater 32.

As described with reference to FIG. 3, current (first current) easily flows through the ceramic heater 22 at low temperatures. For this reason, if power supply to the ceramic heater 32 is started at the same time t1 as in the case of the line G20, the total current may exceed the allowable current value I _TH at that time. Moreover, since in the subsequent time t2 large current flows again to the ceramic heater 22, the total current even time t2 may exceed the allowable current value I _TH.

Therefore, as indicated by the line G41, at the time of low temperature, power supply to the ceramic heater 32 is started at time t10 after time t2. The delay time td2 set at this time is a time from time t0 to time t10, which is longer than the delay time td1 shown in FIG.

The electrical resistance of the ceramic heater 22 and the electrical resistance of the ceramic heater 32 are both lower than in the case of FIG. 2, and current easily flows through each ceramic heater. However, at a low temperature, a delay time td2 longer than the delay time td1 is set. Since the supply of the second current is started after the first current is sufficiently reduced, the total current does not exceed the allowable current value I _TH .

Further, the delay time td2 is set as short as possible within a range in which the total current does not exceed the allowable current value I _TH even when current is supplied to the ceramic heater 32.

That is, the total current at the time when the second current starts to be supplied to the ceramic heater 32 (time t10) is the first current (current I ₀₉ a) that has decreased during the lapse of the delay time td2 and the second current (maximum). although become the sum of the current I ₁₀ a), its magnitude as slightly below the allowable current value I _TH, the length of the delay time td2 is set. In other words, when the current value obtained by subtracting the maximum value of the second current at the low temperature (maximum current I ₁₀ a) from the allowable current value I _TH is defined as the upper limit current, the first current is calculated from the maximum current I ₁₀ a. The length of the delay time td2 is set so as to be the time required to decrease and slightly fall below the upper limit current.

The total current at time t30 is the sum of the first current at that time (the magnitude is current I ₀₈ a as shown in FIG. 4) and the second current (maximum current I ₂₀ a). It becomes. In the present embodiment, not only at time t10 but also at time t30, the delay time td2 at low temperature is set to be as short as possible within a range where the total current does not exceed the allowable current value I _TH. Yes. For this reason, it is possible to start the control for optimizing the air-fuel ratio at an early stage by increasing the temperatures of the ceramic heater 22 and the ceramic heater 32 at an early stage while preventing the power supply unit 42 from malfunctioning. It has become.

Thus, in the control system 10 according to the present embodiment, the delay time td1 or the delay time td2 is set according to the temperature of the ceramic heater 22. A flow of processing performed when the control system 10 is activated will be described with reference to FIG.

At the same time when the internal combustion engine 100 is started, the control system 10 is started and control by the control device 40 is started. In the first S01 of the control, the length of the delay time is set based on the temperature of the ceramic heater 22. Specifically, if the temperature of the ceramic heater 22 is higher than a predetermined threshold, a short delay time td1 is set. If the temperature of the ceramic heater 22 is equal to or lower than the threshold value, a long delay time td2 is set. The temperature of the ceramic heater 22 is acquired by a temperature sensor attached to the ceramic heater 22 directly or in the vicinity thereof.

In S02, the control unit 43 starts supplying power from the power supply unit 42 to the ceramic heater 22. Since the process of S01 immediately before is performed instantaneously, the time when S02 is executed is the same as the time t0 when the control system 10 is activated.

In S03, it is determined whether or not the set delay time (td1 or td2) has elapsed since time t0 when S01 was performed. If the delay time has not elapsed, the process of S03 is repeated. If the delay time has elapsed, the process proceeds to S04.

In S04, the control unit 43 starts supplying power from the power supply unit 42 to the ceramic heater 32. Since the processing as described above is executed when the control system 10 is started, an appropriate delay time (td1 or td2) corresponding to the temperature of the ceramic heater 22 is set.

In the present embodiment, as described above, the temperature of the ceramic heater 22 is acquired by a temperature sensor attached to the ceramic heater 22 directly or in the vicinity thereof. However, the temperature of the ceramic heater 22 may be acquired or estimated by another method. For example, the electrical resistance may be calculated from the voltage applied to the ceramic heater 22 and the current flowing therewith, and the temperature of the ceramic heater 22 may be estimated based on the electrical resistance.

Instead of the mode in which the temperature is estimated based on the calculated electrical resistance and the delay time is set based on the temperature, the delay time td1 or the time based on whether the calculated electrical resistance is higher than a predetermined threshold value or One of the delay times td2 may be set. Specifically, when the calculated electric resistance is higher than a predetermined threshold, the delay time td1 is set, and when the calculated electric resistance is equal to or less than the predetermined threshold, the delay time td2 is set. It is good.

Further, the temperature of the ceramic heater 22 may be estimated based on the element resistance value of the first sensor 20. The element resistance value of the first sensor 20 is an electrical resistance that a current passing through the solid electrolyte 21 receives. Such an element resistance value can be calculated from the relationship between the applied voltage to the solid electrolyte 21 and the passing current when exhaust gas having a known oxygen concentration passes through the exhaust pipe 110.

Instead of the mode in which the temperature is estimated based on the calculated element resistance value and the delay time is set based on the temperature, the delay time is determined based on whether the calculated element resistance value is higher than a predetermined threshold value. Either td1 or delay time td2 may be set. Specifically, the delay time td1 is set when the calculated element resistance value is higher than a predetermined threshold value, and the delay time td2 is set when the calculated element resistance value is less than or equal to the predetermined threshold value. It is good also as an aspect which is.

It is possible to obtain or estimate not only the temperature of the ceramic heater 22 but also the temperature of the ceramic heater 32 and set the delay time based on these temperatures. For example, when both the temperature of the ceramic heater 22 and the ceramic heater 32 are lower than a predetermined threshold value, a delay time longer than the delay time td2 may be set. Further, when both the temperature of the ceramic heater 22 and the ceramic heater 32 are higher than a predetermined threshold value, a delay time shorter than the delay time td1 may be set. Thus, if the delay time is set based on both the temperature of the ceramic heater 22 and the temperature of the ceramic heater 32, it is possible to more reliably prevent the total current from exceeding the allowable current value _ITH. .

As in the case of the ceramic heater 22, the temperature of the ceramic heater 32 may be directly acquired or may be estimated based on the electric resistance of the ceramic heater 32. Further, it may be estimated based on the element resistance value of the second sensor 30. In this case, the element resistance value of the second sensor 30 is an electrical resistance received by the current passing through the solid electrolyte 31.

Either the delay time td1 or the delay time td2 may be set based on whether or not the coolant temperature measured by the water temperature sensor 70 is higher than a predetermined threshold. Specifically, the delay time td1 is set when the measured cooling water temperature is higher than a predetermined threshold, and the delay time td2 is set when the measured cooling water temperature is equal to or lower than the predetermined threshold. It is good also as a mode set up.

Depending on whether the temperature of the outside air measured by the temperature sensor 80 is higher than a predetermined threshold, either the delay time td1 or the delay time td2 may be set. Specifically, the delay time td1 is set when the measured outside air temperature is higher than a predetermined threshold, and the delay time td2 is set when the measured outside air temperature is equal to or lower than the predetermined threshold. It is good also as an aspect which is.

In the present embodiment, either one of the two delay times (td1 or td2) is set based on whether or not the temperature of the ceramic heater 22 is higher than a predetermined threshold value. The delay time may be set from the values (candidates). As shown in FIG. 6, the relationship between the temperature (horizontal axis) of the ceramic heater 22 and the delay time (vertical axis) to be set is stored in the control device 40, and based on the relationship, the ceramic heater The delay time corresponding to the temperature of 22 may be set. In the example shown in FIG. 6, a shorter delay time is set as the temperature of the ceramic heater 22 is higher. The relationship between the temperature of the ceramic heater 22 and the delay time to be set is determined by experiments and simulations performed in advance and is stored by the control device 40.

Further, as shown in FIG. 7, the relationship between the coolant temperature (horizontal axis) measured by the water temperature sensor 70 and the delay time (vertical axis) to be set is stored in the control device 40. Based on this relationship, a delay time corresponding to the coolant temperature may be set. In the example shown in FIG. 7, a shorter delay time is set as the coolant temperature is higher.

Similarly, the relationship between the temperature of the outside air measured by the temperature sensor 80 and the delay time to be set is stored in the control device 40, and the delay time corresponding to the temperature of the outside air is based on the relationship. It is good also as an aspect by which is set. Also in this case, a shorter delay time is set as the outside air temperature is higher.

The embodiments of the present disclosure have been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. That is, those specific examples modified by appropriate design by those skilled in the art are also included in the scope of the present disclosure as long as they have the features of the present disclosure. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present disclosure as long as it includes the features of the present disclosure.

Claims

A first detector for detecting a state of exhaust gas passing through a first position (111a) of an exhaust passage (110) connected to the internal combustion engine (100) having a first heater (22) that generates heat upon receiving electric power. A first receiver (411) for receiving a detection signal output from the sensor (20);
A second sensor (30) that has a second heater (32) that generates heat upon receiving electric power and detects the state of the exhaust gas that passes through a second position (112a) different from the first position in the exhaust passage. A second receiving unit (412) for receiving a detection signal output from
A power supply unit (42) for supplying power to the first heater and the second heater;
A control unit that controls the power supply unit to start supplying power to the second heater at a second time when a delay time has elapsed from the first time at which supply of power to the first heater is started. (43).
The delay time is an upper limit current value within a range in which the sum of the current value flowing through the first heater and the current value flowing through the second heater at the second time does not interfere with the power supply unit. The control device according to claim 1, wherein the control device is determined not to exceed an upper limit value.
The control device according to claim 2, wherein the delay time is set based on at least one of a temperature of the first heater and a temperature of the second heater.
The control device according to claim 2, wherein the delay time is determined based on at least one of an electric resistance value of the first heater and an electric resistance value of the second heater.
The control device according to claim 2, wherein the delay time is determined based on at least one of an element resistance value of the first sensor and an element resistance value of the second sensor.
The control device according to claim 2, wherein the delay time is determined based on a temperature of cooling water for cooling the internal combustion engine.
The control device according to claim 2, wherein the delay time is determined based on a temperature of outside air.