Exhaust sensor control device

Abstract

To suppress excessive power consumption in preheating while enabling early activation of a sensor element through the preheating.SOLUTION: A controller of an exhaust sensor comprises a heater control unit 55 that controls energization of a heater 20. The heater control unit starts energizing the heater at predetermined timing before a starter 36, which cranks an internal combustion engine 1, is turned on, and increases power supplied to the heater when the starter is turned on.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a control device for an exhaust gas sensor.

Background Art

[0002] Conventionally, in order to reduce exhaust emissions and the like, it is known to provide an exhaust gas sensor for detecting the concentration of a specific component in exhaust gas in an exhaust passage of an internal combustion engine. In such an exhaust gas sensor, the sensor element is heated by a heater in order to maintain the sensor element in an active state.

[0003] In order to activate the sensor element at an early stage, it is desirable to perform preheating for heating the sensor element before starting the internal combustion engine. Patent Document 1 describes starting preheating when the ignition switch is turned on, and Patent Document 2 describes starting preheating when the vehicle door changes from a locked state to an unlocked state.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when preheating is performed, the power consumption before starting the internal combustion engine increases. In particular, when the time from the start of preheating to the start of the internal combustion engine is long, the power consumption during preheating becomes excessive. As a result, the voltage of the battery that supplies power to the starter may decrease, and the starting performance of the internal combustion engine may deteriorate.

[0006] Therefore, in view of the above issues, the object of the present invention is to enable early activation of the sensor element by preheating while suppressing excessive power consumption during preheating. [Means for solving the problem]

[0007] The gist of this disclosure is as follows:

[0008] (1) A control device for an exhaust sensor, which includes a sensor element and a heater for heating the sensor element and is located in the exhaust passage of an internal combustion engine, the control device for controlling the supply of power to the heater. The system includes a voltage acquisition unit that acquires the voltage of the battery that supplies power to the starter that cranks the internal combustion engine, and The heater control unit is equipped with, When the ignition switch is turned ON The system starts supplying power to the heater and increases the power supplied to the heater when the starter is turned on. The heater control unit shall, when the ignition switch is turned on, stop supplying power to the heater if the battery voltage is below a predetermined first threshold, and when the starter is turned on, stop supplying power to the heater if the battery voltage is below a predetermined second threshold, and the second threshold is lower than the first threshold. Exhaust sensor control device.

[0010] ( 2 ) The heater control unit shall, if a predetermined starting delay condition is met between the start of energization to the heater and the starter is turned on, reduce the power supplied to the heater or stop energizing the heater, as described above (1 ) Control device for the exhaust sensor described.

[0011] ( 3 The starting delay condition is that the starter is not turned on for a predetermined time or longer after the start of power supply to the heater, as described above ( 2 A control device for the exhaust sensor described in ).

[0012] ( 4 ) An exhaust sensor control device for controlling an exhaust sensor located in the exhaust passage of an internal combustion engine, comprising a sensor element and a heater for heating the sensor element, further comprising a heater control unit for controlling the supply of power to the heater, wherein the heater control unit starts supplying power to the heater when the ignition switch is turned on, increases the power supplied to the heater when the starter for cranking the internal combustion engine is turned on, and if a predetermined starting delay condition is met between the start of power supply to the heater and the starter is turned on, the heater control unit decreases the power supplied to the heater or stops power supply to the heater. The aforementioned starting delay condition is that the door of the vehicle equipped with the internal combustion engine is opened after the heater has been energized. , exclusion Control device for air sensors.

[0013] ( 5 )The heater control unit further comprises a voltage acquisition unit that acquires the voltage of the battery that supplies power to the starter, and the heater control unit When the ignition switch is turned ONWhen the voltage of the battery is less than or equal to a predetermined first threshold value, the power supply to the heater is stopped. When the voltage of the battery is less than or equal to a predetermined second threshold value when the starter is turned on, the power supply to the heater is stopped. The second threshold value is lower than the first threshold value, as described above. 4) Exhaust gas sensor control device described above.

Advantages of the Invention

[0014] According to the present invention, it is possible to early activate the sensor element by preheating while suppressing excessive power consumption during preheating.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a diagram schematically showing an internal combustion engine to which an exhaust gas sensor control device according to a first embodiment of the present invention is applied. [Figure 2] FIG. 2 is a partial cross-sectional view of the air-fuel ratio sensor of FIG. 1. [Figure 3] FIG. 3 is a diagram showing the relationship between the air-fuel ratio of exhaust gas and the output current of the sensor element in the air-fuel ratio sensor. [Figure 4] FIG. 4 is a block diagram showing a part of the configuration of a vehicle in which an exhaust gas sensor control device according to a first embodiment of the present invention is provided. [Figure 5] FIG. 5 is a functional block diagram of the processor of the ECU in the first embodiment. [Figure 6] FIG. 6 is a time chart of on / off of the ignition switch and the like when heater control is executed in the first embodiment. [Figure 7] FIG. 7 is a flowchart showing a control routine for power supply processing in the first embodiment of the present invention. [Figure 8] FIG. 8 is a time chart of on / off of the ignition switch and the like when heater control is executed in the second embodiment. [Figure 9] FIG. 9 is a flowchart showing a control routine for power supply processing in the second embodiment of the present invention. [Figure 10] FIG. 10 is a functional block diagram of a processor of an ECU in the third embodiment. [Figure 11] FIG. 11 is a flowchart showing a control routine for power supply processing in the third embodiment of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are given to similar components.

[0017] <First Embodiment> First, referring to FIGS. 1 to 7, the first embodiment of the present invention will be described.

[0018] <Description of the entire internal combustion engine> FIG. 1 is a diagram schematically showing an internal combustion engine 1 to which a control device for an exhaust sensor according to the first embodiment of the present invention is applied. The internal combustion engine 1 shown in FIG. 1 is a spark ignition internal combustion engine, and specifically, is a gasoline engine that uses gasoline as fuel. The internal combustion engine 1 is mounted on a vehicle and functions as a power source of the vehicle.

[0019] The internal combustion engine 1 includes an engine body 2, and a plurality (for example, four) of cylinders 3 are formed in the engine body 2. An exhaust manifold 4 is connected to the engine body 2, and the exhaust manifold 4 is connected to a casing 7 containing a catalyst 6 via an exhaust pipe 5. The catalyst 6 is, for example, a three-way catalyst that can simultaneously purify hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) in exhaust gas. The exhaust manifold 4 and the exhaust pipe 5 form an exhaust passage for discharging exhaust gas generated by combustion of the air-fuel mixture in the cylinder 3. In FIG. 1, an intake passage for introducing air into the cylinder 3 is omitted.

[0020] <Description of the exhaust sensor> In this embodiment, the internal combustion engine 1 is equipped with an air-fuel ratio sensor 10 as an exhaust sensor for detecting specific components in the exhaust gas. The air-fuel ratio sensor 10 is located in the exhaust passage of the internal combustion engine 1. Specifically, as shown in Figure 1, the air-fuel ratio sensor 10 is located in the exhaust pipe 5 upstream of the catalyst 6. The air-fuel ratio sensor 10 linearly detects the air-fuel ratio of the exhaust gas by detecting the oxygen concentration in the exhaust gas.

[0021] The configuration of the air-fuel ratio sensor 10 will be described in detail below. Figure 2 is a partial cross-sectional view of the air-fuel ratio sensor 10 shown in Figure 1. The air-fuel ratio sensor 10 comprises a sensor element 11 and a heater 20.

[0022] In this embodiment, the air-fuel ratio sensor 10 is a stacked air-fuel ratio sensor constructed by stacking multiple layers. As shown in Figure 2, the sensor element 11 has a solid electrolyte layer 12, a diffusion-limiting layer 13, a first impermeable layer 14, a second impermeable layer 15, an exhaust side electrode 16, and an atmospheric side electrode 17. The solid electrolyte layer 12, the exhaust side electrode 16, and the atmospheric side electrode 17 constitute a sensor cell, which is an electrochemical cell.

[0023] The layers of the sensor element 11 are stacked in the following order from bottom to top in Figure 2: first impermeable layer 14, solid electrolyte layer 12, diffusion-limited layer 13, and second impermeable layer 15. A gas chamber 18 is formed between the solid electrolyte layer 12 and the diffusion-limited layer 13, and an atmospheric chamber 19 is formed between the solid electrolyte layer 12 and the first impermeable layer 14. That is, the gas chamber 18 is defined by the solid electrolyte layer 12 and the diffusion-limited layer 13, and the atmospheric chamber 19 is defined by the solid electrolyte layer 12 and the first impermeable layer 14.

[0024] The gas chamber 18 under test is connected to the exhaust passage of the internal combustion engine via the diffusion rate-limiting layer 13, and the exhaust gas flowing through the exhaust passage of the internal combustion engine is introduced into the gas chamber 18 as the gas under test. On the other hand, the atmospheric chamber 19 is open to the atmosphere, and the atmosphere is introduced into the atmospheric chamber 19.

[0025] The solid electrolyte layer 12 is a thin plate having oxide ion conductivity. The solid electrolyte layer 12 is a sintered body obtained by adding CaO, MgO, Y2O3, Yb2O3, etc. as stabilizers to ZrO2 (zirconia), HfO2, ThO2, Bi2O3, etc. The diffusion-limited layer 13 is a thin plate that is permeable to gas. The diffusion-limited layer 13 is composed of porous ceramics such as alumina, magnesia, silica, spinel, mullite, etc. The first impermeable layer 14 and the second impermeable layer 15 are gas-impermeable thin plates, composed of alumina, for example.

[0026] The exhaust-side electrode 16 is positioned on one side of the solid electrolyte layer 12 (the side facing the gas chamber 18) so as to be exposed to the gas to be measured in the gas chamber 18, i.e., the exhaust gas flowing through the exhaust passage of the internal combustion engine. On the other hand, the atmospheric-side electrode 17 is positioned on the other side of the solid electrolyte layer 12 (the side facing the atmospheric chamber 19) so as to be exposed to the atmosphere in the atmospheric chamber 19. The exhaust-side electrode 16 and the atmospheric-side electrode 17 are positioned facing each other with the solid electrolyte layer 12 in between. The exhaust-side electrode 16 and the atmospheric-side electrode 17 are each made of a highly catalytically active precious metal such as platinum (Pt). For example, the exhaust-side electrode 16 and the atmospheric-side electrode 17 are porous cermet electrodes mainly composed of Pt.

[0027] The heater 20 is placed inside the sensor element 11 and heats the sensor element 11. In this embodiment, the heater 20 is embedded in the first impermeable layer 14. The heater 20 is, for example, a thin plate of cermet containing platinum (Pt) and ceramic (e.g., alumina), and is a heating element that generates heat when an electric current is passed through it.

[0028] As shown in Figure 2, an electrical circuit 21 is connected to the exhaust-side electrode 16 and the atmospheric-side electrode 17 of the sensor element 11. The electrical circuit 21 includes a voltage application circuit 22 and a current detection circuit 23.

[0029] The voltage application circuit 22 is connected to the sensor element 11 and applies a voltage to the sensor element 11. Specifically, the voltage application circuit 22 applies a voltage to the sensor element 11 such that the potential of the atmospheric side electrode 17 is higher than the potential of the exhaust side electrode 16. Therefore, the exhaust side electrode 16 functions as the negative electrode and the atmospheric side electrode 17 functions as the positive electrode.

[0030] The current detection circuit 23 is connected to the sensor element 11 and detects the current flowing between the exhaust side electrode 16 and the atmospheric side electrode 17 when a voltage is applied to the sensor element 11, that is, the output current of the sensor element 11 when a voltage is applied to the sensor element 11.

[0031] When a voltage is applied to the sensor element 11, oxide ions move between the exhaust-side electrode 16 and the atmospheric-side electrode 17 in accordance with the air-fuel ratio of the exhaust gas on the exhaust-side electrode 16. As a result, the output current of the sensor element 11 changes according to the air-fuel ratio of the exhaust gas. Figure 3 shows the relationship between the air-fuel ratio of the exhaust gas and the output current I of the sensor element 11 in the air-fuel ratio sensor 10. In the example in Figure 3, a voltage of 0.45V is applied to the sensor element 11.

[0032] As can be seen from Figure 3, the output current I is zero when the air-fuel ratio of the exhaust gas is at the stoichiometric air-fuel ratio. Furthermore, with the air-fuel ratio sensor 10, the output current I increases as the oxygen concentration of the exhaust gas increases, that is, as the air-fuel ratio of the exhaust gas becomes leaner. Therefore, the air-fuel ratio sensor 10 can continuously (linearly) detect the air-fuel ratio of the exhaust gas.

[0033] <Exhaust sensor control device> Figure 4 is a block diagram showing a part of the configuration of a vehicle 100 equipped with an exhaust sensor control device according to the first embodiment of the present invention. As shown in Figure 4, the vehicle 100 is equipped with an electronic control unit (ECU) 50. The ECU 50 has a communication interface 51, a memory 52, and a processor 53. The communication interface 51 and the memory 52 are connected to the processor 53 via signal lines. In this embodiment, one ECU 50 is provided, but multiple ECUs may be provided for each function.

[0034] The communication interface 51 has an interface circuit for connecting the ECU 50 to an in-vehicle network compliant with standards such as CAN (Controller Area Network). The ECU 50 communicates with in-vehicle equipment connected to the in-vehicle network via the communication interface 51 and the in-vehicle network.

[0035] The memory 52 includes, for example, volatile semiconductor memory (e.g., RAM) and non-volatile semiconductor memory (e.g., ROM). The memory 52 stores computer programs executed by the processor 53, various data used when various processes are executed by the processor 53, and so on. The computer programs executed by the processor 53 may be provided in the form of data stored on a computer-readable recording medium. The computer-readable recording medium may be, for example, a magnetic recording medium, an optical recording medium, or a semiconductor memory.

[0036] The processor 53 has one or more CPUs (Central Processing Units) and their peripheral circuits, and performs various processes. The processor 53 may also have other arithmetic circuits such as a logic unit, a numerical unit, or a graphics processing unit.

[0037] The ECU 50 performs various controls based on the outputs of various sensors provided in the vehicle 100 or the internal combustion engine 1. In this embodiment, the current detection circuit 23, engine switch 31, door sensor 32, seat occupancy sensor 33, and battery voltage sensor 34 are electrically connected to the ECU 50, and their outputs are input to the ECU 50.

[0038] The engine switch 31 is located near the steering wheel of the vehicle 100 and is operated by the driver of the vehicle 100. When the engine switch 31 is operated by the driver, the switch position of the engine switch 31 is switched between ACC (accessory) on, ignition on, starter on, and power off, and the engine switch 31 outputs a signal corresponding to the switch position. When the switch position is ACC on, the ACC power is turned on. When the switch position is ignition on, the ignition switch is turned on. When the switch position is starter on, the starter 36, which will be described later, is turned on.

[0039] The engine switch 31 is, for example, a rotary-operated key switch or a push-operated button switch. If the engine switch 31 is a button switch, when the driver presses the push button while pressing the brake pedal, the switch position of the engine switch 31 is continuously switched from ignition on to starter on. The engine switch 31 may also be a portable switch capable of communicating with the ECU 50.

[0040] The door sensor 32 detects the opening and closing of the doors of the vehicle 100. The seat sensor 33 is located in the driver's seat of the vehicle 100 and detects whether or not the driver of the vehicle 100 is seated in the driver's seat. The battery voltage sensor 34 detects the voltage of the battery 35 that supplies power to the electrical components of the vehicle 100.

[0041] In this embodiment, the starter (starter motor) 36, the voltage application circuit 22, and the heater 20 are electrically connected to the ECU 50, which controls them. The starter 36 cranks the internal combustion engine 1. Specifically, the starter 36 rotates the crankshaft of the internal combustion engine 1 to increase the engine speed before combustion of the fuel-air mixture begins in the internal combustion engine 1. When the switch position of the engine switch 31 is set to starter ON, the ECU 50 turns on the starter 36 and starts the starter 36.

[0042] The ECU 50 controls the voltage applied to the sensor element 11 via the voltage application circuit 22. For example, after the internal combustion engine 1 starts, the ECU 50 applies a voltage (0.15V to 0.7V) within the limit current region where the output current hardly changes even if the applied voltage changes, for example, 0.45V, to the sensor element 11.

[0043] Figure 5 is a functional block diagram of the processor 53 of the ECU 50 in the first embodiment. In this embodiment, the ECU 50 functions as a control device for the exhaust sensor, and the processor 53 has a heater control unit 55. The heater control unit 55 is a functional module realized by the execution of a computer program stored in the memory 52 of the ECU 50 by the processor 53 of the ECU 50. The heater control unit 55 may also be realized by a dedicated arithmetic circuit provided in the processor 53.

[0044] By the way, in order to accurately detect the air-fuel ratio of the exhaust gas using the air-fuel ratio sensor 10, it is necessary to activate the sensor element 11 of the air-fuel ratio sensor 10. For this reason, the heater control unit 55 controls the power supply to the heater 20, and the heater 20 heats the sensor element 11. At this time, the heater control unit 55 supplies power from the battery 35 to the heater 20 via the heater drive circuit and controls the power supplied to the heater 20. For example, the heater control unit 55 controls the power supplied to the heater 20 so that the temperature of the sensor element 11 reaches a predetermined target temperature.

[0045] In this embodiment, the heater control unit 55 controls the power supplied to the heater 20 by PWM (Pulse Width Modulation) control. In PWM control, the switching period (frequency) is kept constant, and the effective voltage supplied to the heater 20 is controlled by changing the duty cycle by changing the switching pulse width (on time). The duty cycle is calculated by dividing the pulse width by the period (duty cycle = pulse width / period), and the longer the pulse width, the higher the duty cycle. The higher the duty cycle in PWM control, the greater the power supplied to the heater 20.

[0046] To activate the sensor element 11 early, it is desirable to perform preheating to heat the sensor element 11 before starting the internal combustion engine 1. However, when preheating is performed, the power consumption before starting the internal combustion engine 1 increases. In particular, if there is a long time between the start of preheating and the start of the internal combustion engine 1, the power consumption during preheating becomes excessive. As a result, the voltage of the battery 35 that supplies power to the starter 36 decreases, which may worsen the starting performance of the internal combustion engine 1.

[0047] Therefore, in this embodiment, the heater control unit 55 starts supplying power to the heater 20 at a predetermined timing before the starter 36 is turned on, and increases the power supplied to the heater 20 when the starter 36 is turned on. In other words, the heater control unit 55 makes the power supplied to the heater 20 before the starter 36 is turned on less than the power supplied to the heater 20 after the starter 36 is turned on. This makes it possible to enable early activation of the sensor element 11 by preheating while suppressing excessive power consumption during preheating.

[0048] When the ignition switch is turned on in vehicle 100, there is a high probability that the starter 36 will be turned on within a short time, requiring the start of the internal combustion engine 1. Therefore, in this embodiment, the heater control unit 55 starts supplying power to the heater 20 when the ignition switch is turned on. This prevents the waste of power consumption during preheating if the internal combustion engine 1 is not started.

[0049] In this embodiment, the heater control unit 55 increases or decreases the power supplied to the heater 20 by changing the duty cycle in the PWM control of the heater 20. Therefore, the heater control unit 55 increases the power supplied to the heater 20 by increasing the duty cycle when the starter 36 is turned on. That is, the heater control unit 55 makes the duty cycle before the starter 36 is turned on lower than the duty cycle after the starter 36 is turned on.

[0050] <Explanation of control using a time chart> The heater control described above will now be explained in detail with reference to the time chart in Figure 6. Figure 6 is a time chart of the on / off state of the ignition switch, the on / off state of the starter 36, the voltage of the battery 35, the duty cycle in the PWM control of the heater 20, and the temperature of the sensor element 11 when the heater control in the first embodiment is performed.

[0051] In the illustrated example, the ignition switch is turned on at time t1. When the ignition switch is turned on, power is supplied to the heater 20, and power is supplied to the heater 20 from the battery 35. When power is supplied to the heater 20, the duty cycle is set to the low power value LO, and the duty cycle is maintained at the low power value LO until the starter 36 is turned on.

[0052] From time t1 onward, the temperature of the sensor element 11 rises due to heating by the heater 20. At this time, the duty cycle is set so that the power supplied to the heater 20 is small, so the power consumption during preheating is reduced, and the drop in the battery voltage 35 is also reduced. Therefore, it is possible to suppress the deterioration of the starting performance of the internal combustion engine 1 due to insufficient voltage in the battery 35.

[0053] After time t1, at time t2, the starter 36 is turned on, and the duty cycle is switched from a low power value LO to a high power value HI. As a result, the power supplied to the heater 20 increases, and the temperature rise of the sensor element 11 is accelerated. The starter 36 also operates until the engine speed reaches a predetermined speed required for combustion of the fuel mixture, and the operation of the starter 36 causes a significant drop in the voltage of the battery 35.

[0054] The duty cycle is maintained at a high power value HI from the time the starter 36 is turned on until the temperature of the sensor element 11 reaches a predetermined switching temperature Tsw. The switching temperature Tsw is set to a temperature lower than the target temperature Ttrg at which the sensor element 11 is activated. In this embodiment, since preheating is started before the starter 36 is turned on, the temperature of the sensor element 11 rises rapidly and reaches the switching temperature Tsw at time t3. After time t3, the power supplied to the heater is feedback controlled so that the temperature of the sensor element 11 is maintained at the target temperature Ttrg. The duty cycle in the feedback control is set to a value lower than the high power value HI.

[0055] <Voltage supply processing> The control for supplying power to the heater 20 will be described in detail below with reference to the flowchart in Figure 7. Figure 7 is a flowchart of the control routine for the power supply process in the first embodiment of the present invention. This control routine is repeatedly executed by the ECU 50 at predetermined execution intervals.

[0056] First, in step S101, the heater control unit 55 determines whether the ignition switch has been turned on based on the output of the engine switch 31. If it is determined that the ignition switch has not been turned on, this control routine terminates. On the other hand, if it is determined that the ignition switch has been turned on, this control routine proceeds to step S102.

[0057] In step S102, the heater control unit 55 determines whether a predetermined heater energization condition is met. The heater energization condition is a condition for allowing power to be supplied to the heater 20, for example, that no abnormality is detected in the air-fuel ratio sensor 10. The abnormality diagnosis of the air-fuel ratio sensor 10 is performed as appropriate by a known method. If it is determined that the heater energization condition is not met, this control routine terminates. On the other hand, if it is determined that the heater energization condition is met, this control routine proceeds to step S103.

[0058] In step S103, the heater control unit 55 determines whether the temperature T of the sensor element 11 is equal to or greater than a predetermined switching temperature Tsw. The heater control unit 55 calculates the temperature of the sensor element 11, for example, based on the impedance of the sensor element 11. The switching temperature Tsw is set to a temperature lower than the target temperature Ttrg of the sensor element 11.

[0059] If it is determined in step S103 that the temperature T of the sensor element 11 is less than the switching temperature Tsw, the control routine proceeds to step S104. In step S104, the heater control unit 55 determines whether the starter 36 has been turned on based on the output of the engine switch 31. If it is determined that the starter 36 has not been turned on, the control routine proceeds to step S105.

[0060] In step S105, the heater control unit 55 supplies power to the heater 20 by setting the duty cycle DR in the PWM control of the heater 20 to a low power value LO. The low power value LO is predetermined and set to, for example, 10% to 30%. After step S105, this control routine terminates.

[0061] On the other hand, if it is determined in step S104 that the starter 36 has been turned on, the control routine proceeds to step S106. In step S106, the heater control unit 55 sets the duty cycle DR to the high power value HI and supplies power to the heater 20. The high power value HI is predetermined to be a value higher than the low power value LO, for example, set to 50% to 70%. After step S106, the control routine terminates.

[0062] Furthermore, if it is determined in step S103 that the temperature T of the sensor element 11 is equal to or greater than the switching temperature Tsw, the control routine proceeds to step S107. In step S107, the heater control unit 55 feedback controls the power supplied to the heater 20 so that the temperature T of the sensor element 11 is maintained at a predetermined target temperature Ttrg. In this embodiment, the heater control unit 55 feedback controls the duty cycle DR so that the temperature T of the sensor element 11 is maintained at a predetermined target temperature Ttrg. The target temperature Ttrg is predetermined as the temperature at which the sensor element 11 is activated. After step S107, the control routine terminates.

[0063] In step S101, the heater control unit 55 may determine whether the driver of the vehicle 100 is seated in the driver's seat based on the output of the seat sensor 33. That is, the predetermined timing at which power is supplied to the heater 20 may be when the driver of the vehicle 100 is seated in the driver's seat. Also in step S101, the heater control unit 55 may determine whether the door of the vehicle 100 is opened while the driver of the vehicle 100 is not seated in the driver's seat based on the outputs of the door sensor 32 and the seat sensor 33. That is, the predetermined timing at which power is supplied to the heater 20 may be when the door of the vehicle 100 is opened while the driver of the vehicle 100 is not seated in the driver's seat. Also in step S101, the heater control unit 55 may determine whether the door of the vehicle 100 has changed from a locked state to an unlocked state. That is, the predetermined timing at which power is supplied to the heater 20 may be when the door of the vehicle 100 has changed from a locked state to an unlocked state.

[0064] <Second Embodiment> The control device for the exhaust sensor according to the second embodiment is basically the same as the control device for the exhaust sensor according to the first embodiment, except for the points described below. For this reason, the second embodiment of the present invention will be described below, focusing on the differences from the first embodiment.

[0065] As described above, the heater control unit 55 starts supplying power to the heater 20 at a predetermined timing before the starter 36 is turned on, and increases the power supplied to the heater 20 when the starter 36 is turned on. However, the starter 36 is not always turned on quickly after the predetermined timing.

[0066] Therefore, in the second embodiment, if a predetermined starting delay condition is met between the start of energization to the heater 20 and the starter 36 is turned on, the heater control unit 55 reduces the power supplied to the heater 20 or stops energizing the heater 20. This makes it possible to suppress the waste of power when the internal combustion engine 1 is not started.

[0067] The starting delay condition is a condition that is met when there is a high probability that the starting of the internal combustion engine 1 will be delayed, for example, when the starter 36 is not turned on for a predetermined time or longer after the start of energization to the heater 20. In this embodiment, the heater control unit 55 starts energizing the heater 20 when the ignition switch is turned on, and reduces the power supplied to the heater 20 if the starter 36 is not turned on for a predetermined time or longer after the ignition switch is turned on. For example, when a predetermined time has elapsed after the ignition switch is turned on, the heater control unit 55 switches the duty cycle in the PWM control of the heater 20 from a low power value LO to a second low power value LO2 which is lower than the low power value LO.

[0068] The heater control in the second embodiment will be described in detail below with reference to the time chart in Figure 8. Figure 8 is a time chart of the on / off state of the ignition switch, the on / off state of the starter 36, the elapsed time since the ignition switch was turned on, the duty cycle in the PWM control of the heater 20, and the temperature of the sensor element 11 when the heater control in the second embodiment is performed.

[0069] In the illustrated example, the ignition switch is turned on at time t1. When the ignition switch is turned on, power is supplied to the heater 20, and power is supplied to the heater 20 from the battery 35. When power is supplied to the heater 20, the duty cycle is set to the low power value LO.

[0070] From time t1 onward, the temperature of the sensor element 11 rises due to heating by the heater 20. However, in this example, the ignition switch and starter 36 are not continuously turned on, and the starter 36 remains in the off state. At time t2, when the elapsed time since the ignition switch was turned on reaches a predetermined time Tth, the start delay condition is met. Therefore, at time t2, the duty cycle is switched from the low power value LO to the second low power value LO2 in order to reduce the power supplied to the heater 20. As a result, the temperature of the sensor element 11 is maintained at approximately the same temperature, and power waste is suppressed.

[0071] After time t2, at time t3, the starter 36 is turned on and the duty cycle is switched from the second low power value LO2 to the high power value HI. As a result, the power supplied to the heater 20 increases, and the temperature rise of the sensor element 11 is accelerated. When the temperature of the sensor element 11 reaches the switching temperature Tsw at time t4, the power supplied to the heater is feedback controlled so that the temperature of the sensor element 11 is maintained at the target temperature Ttrg from time t4 onward.

[0072] Figure 9 is a flowchart showing the control routine for power supply processing in the second embodiment of the present invention. This control routine is repeatedly executed by the ECU 50 at predetermined execution intervals.

[0073] Steps S201 to S204 are executed in the same way as steps S101 to S104 in Figure 7. If it is determined in step S204 that the starter 36 is not turned on, the control routine proceeds to step S205.

[0074] In step S205, the heater control unit 55 determines whether the start delay condition is met. The start delay condition is, for example, that the starter 36 is not turned on for a predetermined time or longer after the start of power supply to the heater 20, that is, a predetermined time or longer has elapsed since the ignition switch was turned on.

[0075] If it is determined in step S205 that the start delay condition is not met, the control routine proceeds to step S206. In step S206, the heater control unit 55 supplies power to the heater 20 by setting the duty cycle DR in the PWM control of the heater 20 to a low power value LO. The low power value LO is predetermined and set to, for example, 10% to 30%. After step S206, the control routine terminates.

[0076] On the other hand, if it is determined in step S205 that the start delay condition is met, the control routine proceeds to step S207. In step S207, the heater control unit 55 sets the duty cycle DR to the second low power value LO2 and supplies power to the heater 20. The second low power value LO2 is predetermined to be lower than the low power value LO, for example, set to 5% to 20%. After step S207, the control routine terminates.

[0077] Furthermore, if it is determined in step S204 that the starter 36 has been turned on, the control routine proceeds to step S208. In step S208, the heater control unit 55 sets the duty cycle DR to the high power value HI and supplies power to the heater 20. The high power value HI is predetermined to be a value higher than the low power value LO, for example, set to 50% to 70%. After step S208, the control routine terminates.

[0078] Furthermore, if it is determined in step S203 that the temperature T of the sensor element 11 is equal to or greater than the switching temperature Tsw, the control routine proceeds to step S209. In step S209, similar to step S107 in Figure 7, the heater control unit 55 provides feedback control to the power supplied to the heater 20 so that the temperature T of the sensor element 11 is maintained at a predetermined target temperature Ttrg. After step S209, the control routine terminates.

[0079] In step S205, the heater control unit 55 may determine, based on the output of the door sensor 32, whether or not the door of the vehicle 100 was opened after the ignition switch was turned on. That is, the starting delay condition may be that the door of the vehicle 100 was opened after the power supply to the heater 20 was started. Also in step S205, the heater control unit 55 may determine, based on the output of the seat sensor 33, whether or not the driver of the vehicle 100 left the driver's seat after the ignition switch was turned on. That is, the starting delay condition may be that the driver of the vehicle 100 left the driver's seat after the power supply to the heater 20 was started.

[0080] Furthermore, in step S207, the heater control unit 55 may provide feedback control to the power supplied to the heater 20 so that the temperature T of the sensor element 11 is maintained at a predetermined temperature lower than the switching temperature Tsw. The predetermined temperature is set, for example, to the temperature of the sensor element 11 when the starter 36 is started, when the ignition switch and starter 36 are continuously turned on.

[0081] Furthermore, in step S207, the heater control unit 55 may stop supplying power to the heater 20. In addition, the control routine in Figure 9 can be modified in the same way as the control routine in Figure 7.

[0082] <Third Embodiment> The control device for the exhaust sensor according to the third embodiment is basically the same as the control device for the exhaust sensor according to the first embodiment, except for the points described below. For this reason, the third embodiment of the present invention will be described below, focusing on the parts that differ from the first embodiment.

[0083] Figure 10 is a functional block diagram of the processor 53 of the ECU 50 in the third embodiment. In the third embodiment, the processor 53 has a voltage acquisition unit 56 in addition to the heater control unit 55. The heater control unit 55 and the voltage acquisition unit 56 are functional modules realized by the execution of a computer program stored in the memory 52 of the ECU 50 by the processor 53 of the ECU 50. The heater control unit 55 and the voltage acquisition unit 56 may also be realized by a dedicated arithmetic circuit provided in the processor 53.

[0084] The voltage acquisition unit 56 acquires the voltage of the battery 35 that supplies power to the starter 36. For example, the voltage acquisition unit 56 acquires the voltage of the battery 35 based on the output of the battery voltage sensor 34.

[0085] Since a lot of power is consumed when cranking the internal combustion engine 1, it is necessary to maintain a high voltage in the battery 35 until cranking begins. For this reason, in the third embodiment, the heater control unit 55 stops supplying power to the heater 20 if the voltage of the battery 35 is below a predetermined first threshold at a predetermined timing when power is supplied to the heater 20. For example, the heater control unit 55 stops supplying power to the heater 20 if the voltage of the battery 35 is below the first threshold when the ignition switch is turned on. This prevents preheating from being performed when the voltage of the battery 35 is insufficient, which would worsen the starting performance of the internal combustion engine 1.

[0086] On the other hand, after cranking has started, the required battery voltage 35 is lower than before cranking started. Therefore, when the starter 36 is turned on, the heater control unit 55 stops supplying power to the heater 20 if the voltage of the battery 35 is below a predetermined second threshold, which is lower than the first threshold. This prevents deterioration of the starting performance of the internal combustion engine 1 while ensuring an opportunity for preheating.

[0087] Figure 11 is a flowchart showing the control routine for power supply processing in the third embodiment of the present invention. This control routine is repeatedly executed by the ECU 50 at predetermined execution intervals.

[0088] Steps S301 to S304 are executed in the same way as steps S101 to S104 in Figure 7. If it is determined in step S304 that the starter 36 is not turned on, the control routine proceeds to step S305.

[0089] In step S305, the heater control unit 55 determines whether the voltage of the battery 35, acquired by the voltage acquisition unit 56, is higher than the first threshold Vth1. The first threshold Vth1 is predetermined and set to 12V to 13V, for example, 12.5V.

[0090] If it is determined in step S305 that the voltage of the battery 35 is higher than the first threshold Vth1, the control routine proceeds to step S306. In step S306, similar to step S105 in Figure 7, the heater control unit 55 supplies power to the heater 20 by setting the duty cycle DR in the PWM control of the heater 20 to a low power value LO. After step S306, the control routine terminates.

[0091] On the other hand, if it is determined in step S304 that the starter 36 has been turned on, the control routine proceeds to step S307. In step S307, the heater control unit 55 determines whether the voltage of the battery 35, acquired by the voltage acquisition unit 56, is higher than the second threshold Vth2. The second threshold Vth2 is predetermined as a value lower than the first threshold Vth1, and is set to 8V to 10V, for example, 9V.

[0092] If, in step S307, the voltage of the battery 35 is determined to be higher than the second threshold Vth2, the control routine proceeds to step S308. In step S308, similar to step S106 in Figure 7, the heater control unit 55 sets the duty cycle DR to the high power value HI and supplies power to the heater 20. After step S308, the control routine terminates.

[0093] Furthermore, if it is determined in step S305 that the voltage of the battery 35 is less than or equal to the first threshold Vth1, or if it is determined in step S307 that the voltage of the battery 35 is less than or equal to the second threshold Vth2, the control routine proceeds to step S309. In step S309, the heater control unit 55 stops energizing the heater 20, i.e., stops supplying power to the heater 20. After step S309, the control routine terminates.

[0094] Furthermore, the control routine in Figure 11 can be modified in the same way as the control routine in Figure 7.

[0095] <Other Embodiments> Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. For example, the internal combustion engine to which the exhaust sensor control device is applied may be a compression auto-ignition internal combustion engine (e.g., a diesel engine).

[0096] Furthermore, the air-fuel ratio sensor 10 may be positioned at another location, such as downstream of the catalyst 6. Alternatively, an upstream air-fuel ratio sensor positioned upstream of the catalyst 6 and a downstream air-fuel ratio sensor positioned downstream of the catalyst 6 may be provided in the internal combustion engine 1, and the exhaust sensor control device may apply the heater control described above to at least one of the upstream air-fuel ratio sensor and the downstream air-fuel ratio sensor.

[0097] Furthermore, instead of the air-fuel ratio sensor 10, other exhaust sensors controlled by the exhaust sensor control device may be used, such as a nitrogen oxide sensor (NOx sensor) that detects nitrogen oxides (NOx) in the exhaust gas, an ammonia sensor that detects the concentration of ammonia in the exhaust gas, or an oxygen sensor that detects whether the air-fuel ratio of the exhaust gas is rich or lean.

[0098] Furthermore, the embodiments described above can be implemented in any combination. When the second and third embodiments are combined, steps S205 to S207 in Figure 9 are executed in the control routine of Figure 11 instead of step S306. [Explanation of symbols]

[0099] 1. Internal combustion engine 5. Exhaust pipe 10. Air-fuel ratio sensor 11 Sensor elements 20 Heaters 36 Starter 50 Electronic Control Unit (ECU) 53 processors 55 Heater control unit

Claims

1. An exhaust sensor control device comprising a sensor element and a heater for heating the sensor element, and which controls an exhaust sensor located in the exhaust passage of an internal combustion engine, A heater control unit that controls the supply of power to the heater, A voltage acquisition unit that acquires the voltage of the battery that supplies power to the starter that cranks the internal combustion engine. Equipped with, The heater control unit starts supplying power to the heater when the ignition switch is turned on, and increases the power supplied to the heater when the starter is turned on. The heater control unit controls the supply of power to the heater when the ignition switch is turned on and the battery voltage is below a predetermined first threshold, and when the starter is turned on and the battery voltage is below a predetermined second threshold, wherein the second threshold is lower than the first threshold, and is a control device for an exhaust sensor.

2. The control device for an exhaust sensor according to claim 1, wherein the heater control unit reduces the power supplied to the heater or stops supplying power to the heater if a predetermined starting delay condition is met between the start of power supply to the heater and the starter is turned on.

3. The control device for an exhaust sensor according to claim 2, wherein the starting delay condition is that the starter is not turned on for a predetermined time or longer after the start of power supply to the heater.

4. A control device for an exhaust sensor, comprising a sensor element and a heater for heating the sensor element, and for controlling an exhaust sensor located in the exhaust passage of an internal combustion engine, The system includes a heater control unit that controls the supply of power to the heater, The heater control unit starts supplying power to the heater when the ignition switch is turned on, and increases the power supplied to the heater when the starter that cranks the internal combustion engine is turned on. If a predetermined starting delay condition is met between the start of power supply to the heater and the starter is turned on, the heater control unit reduces the power supplied to the heater or stops power supply to the heater. The start delay condition is that the door of the vehicle equipped with the internal combustion engine is opened after the heater has been energized, in the control device for the exhaust sensor.

5. The system further includes a voltage acquisition unit that acquires the voltage of the battery that supplies power to the starter, The control device for an exhaust sensor according to claim 4, wherein the heater control unit stops supplying power to the heater when the ignition switch is turned on and the battery voltage is below a predetermined first threshold, and stops supplying power to the heater when the starter is turned on and the battery voltage is below a predetermined second threshold, and the second threshold is lower than the first threshold.

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