Gas sensor control device and heating control method

Abstract

To provide a gas sensor control device or the like in a hybrid vehicle, which can reduce power consumption of a heater of a gas sensor during traveling in a motor traveling mode.SOLUTION: A gas sensor control device 1 fitted to an exhaust pipe 208 of an engine 201 in a hybrid vehicle 200 to control a gas sensor 2 having a detection cell 51 for detecting a density of specific gas and a heater 83 for heating the detection cell 51 comprises: a first determination unit that determines which of an engine traveling mode and a motor traveling mode using only a driving force of a motor 202 a traveling mode is; and a second determination unit that determines whether the charging level of a battery 204 exceeds a first threshold level α. A heater control unit executes energization control for the heater 83 in one of a standby mode for causing the heater 83 to generate heat at a standby temperature lower than an active temperature or a stop mode for stopping energization of the heater 83 when the first determination unit determines the motor traveling mode and the second determination unit determines that the charging level exceeds the first threshold level α.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas sensor control device and a heating control method. [Background technology]

[0002] A hybrid vehicle is a vehicle equipped with an engine and a motor with a power generating function as driving power sources. Such hybrid vehicles have two driving modes: a motor driving mode in which the vehicle runs solely on the driving force of the motor, and an engine driving mode in which the driving force of the engine is primarily used. These modes can be switched appropriately depending on the required driving force, etc. For example, when the required driving force is small, the hybrid vehicle runs in the motor driving mode. Furthermore, when the required driving force increases, for example, by depressing the accelerator pedal while in the motor driving mode, the hybrid vehicle runs in the engine driving mode.

[0003] A gas sensor is attached to the exhaust pipe of the engine of a hybrid vehicle. The gas sensor detects the concentration of a specific gas contained in the gas flowing through the exhaust pipe for purposes such as feedback control of the air-fuel ratio, and is equipped with a detection cell including a solid electrolyte (e.g., a zirconia-based material such as partially stabilized zirconia) and a pair of electrodes, and a heater for heating the detection cell. The detection cell needs to be maintained at a predetermined temperature (e.g., 600 to 700°C) to be activated by the heater so that the concentration of the specific gas can be detected with high accuracy.

[0004] Patent document 1 describes a technology that reduces the burden on the battery by stopping the power supply to the heater of the gas sensor when the engine is automatically stopped during a temporary stop such as waiting at a traffic light, thereby reducing the power consumption of the heater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-16317 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventionally, in hybrid vehicles, techniques for reducing the power consumption of the heater of the gas sensor when the vehicle is running in the motor running mode have not been fully considered.

[0007] An object of the present invention is to provide a gas sensor control device and the like for a hybrid vehicle that can reduce power consumption of a heater in a gas sensor when the vehicle is running in a motor running mode. [Means for solving the problem]

[0008] The means for solving the above problems are as follows: <1> A gas sensor control device is attached to an exhaust pipe of a hybrid vehicle that has an engine and a motor with a power generating function as driving power sources, and that also has a battery that supplies power to the motor or stores power from the motor, and that controls a gas sensor having a detection cell that detects the concentration of a specific gas and a heater that heats the detection cell, a heater control unit that controls the energization of the heater and, when the driving mode of the hybrid vehicle is an engine driving mode that uses the driving force of the engine, causes the heater to generate heat at an activation temperature that makes the detection cell detectable; the gas sensor control device also comprises a first determination unit that determines whether the driving mode is the engine driving mode or a motor driving mode that uses only the driving force of the motor; and a second determination unit that determines whether the charge level of the battery exceeds a first threshold value α, wherein, when the first determination unit determines the driving mode is the motor driving mode and the second determination unit determines that the charge level of the battery exceeds the first threshold value α, the heater control unit controls the energization of the heater in either a standby mode in which the heater generates heat at a standby temperature that is lower than the activation temperature, or a stop mode in which the energization of the heater is stopped.

[0009] <2> the heater control unit selects either the standby mode or the stop mode according to the charge level of the battery and controls the energization of the heater. <1> The gas sensor control device according to claim 1.

[0010] <3> When the charge level of the battery falls below a second threshold β (where β>α) in the stop mode, the heater control unit switches to the standby mode and controls the energization of the heater. <1> or <2> The gas sensor control device according to claim 1.

[0011] <4> When the charge level of the battery exceeds a third threshold value γ (where γ>β) during the standby mode, the heater control unit switches to the stop mode and controls the energization of the heater. <1> or <2> The gas sensor control device according to claim 1.

[0012] <5> A heating control method for a gas sensor control device, the gas sensor being attached to an exhaust pipe of the engine of a hybrid vehicle that has an engine and a motor with a power generating function as driving power sources, and also has a battery that supplies power to the motor or stores power from the motor, the gas sensor having a detection cell that detects the concentration of a specific gas and a heater that heats the detection cell, and a heater control unit that controls the energization of the heater and causes the heater to generate heat at an activation temperature that makes the detection cell in a state where it can detect gas when the driving mode of the hybrid vehicle is an engine driving mode that uses the driving force of the engine. a first determination step of determining whether the driving mode is the engine driving mode or a motor driving mode that uses only the driving force of the motor; a second determination step of determining whether the charge level of the battery exceeds a first threshold value α; and a power supply control step of the heater control unit controlling power supply to the heater in either a standby mode in which the heater generates heat at a standby temperature lower than the activation temperature, or a stop mode in which power supply to the heater is stopped, when the determination result of the first determination step is the motor driving mode and it is determined in the second determination step that the charge level exceeds the first threshold value α.

[0013] <6> In the power supply control step, the heater control unit selects either the standby mode or the stop mode according to a charge level of the battery and controls the power supply to the heater. <5> The heating control method according to claim 1.

[0014] <7> In the power supply control step, when the charge level of the battery falls below a second threshold value β (where β>α) in the stop mode, the heater control unit switches to the standby mode and performs power supply control of the heater. <5> or <6> The heating control method according to claim 1.

[0015] <8> In the power supply control step, when the charge level of the battery exceeds a third threshold value γ (where γ>β) in the standby mode, the heater control unit switches to the stop mode and performs power supply control of the heater. <5> or <6> The heating control method according to claim 1. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a gas sensor control device for a hybrid vehicle, which can reduce the power consumption of the heater of the gas sensor when the vehicle is running in the motor running mode. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of a hybrid vehicle equipped with a gas sensor control device according to a first embodiment; [Figure 2] Block diagram showing an example of the functional configuration of a microcontroller [Figure 3] 10 is a flowchart showing a process for controlling the power supply to the heater, which is executed by a microcomputer. [Figure 4] FIG. 1 is an explanatory diagram showing the relationship between the battery charge level and the driving mode in a hybrid vehicle, and the relationship between the battery charge level and the heater control mode. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Embodiment 1> A gas sensor control device 1 and a heating control method according to a first embodiment of the present invention will be described below with reference to Figures 1 to 4. Figure 1 is an explanatory diagram showing a schematic configuration of a hybrid vehicle 200 equipped with a gas sensor control device 1 according to the first embodiment. First, the hybrid vehicle 200 will be described.

[0019] As shown in Fig. 1, a hybrid vehicle (hereinafter sometimes referred to as an "HV vehicle") 100 includes an engine 201 as a driving force source and a motor 202 with a power generation function. The HV vehicle 200 has two driving modes: a motor driving mode in which the vehicle runs using only the driving force of the motor 202, and an engine driving mode in which the driving force of the engine 201 is mainly used, and the driving modes (motor driving mode, engine driving mode) are switched appropriately depending on the required driving force, etc.

[0020] 1, in addition to the engine 201 and the motor 202, the HV vehicle 200 includes an inverter 203, a battery 204, a powertrain 205, drive wheels 206, an ECU 207, etc. Note that in this specification, for the sake of convenience of explanation, the configuration of the HV vehicle 200 is simplified. Therefore, the HV vehicle 200 may be provided with other components in addition to the components shown in FIG. 1, as appropriate.

[0021] Engine 201 is an internal combustion engine that generates power using gasoline or other fuel, and may be, for example, a four-cylinder gasoline engine. Each cylinder of engine 201 is provided with a spark plug. An air cleaner, an intake pipe, and an intake manifold are provided upstream of engine 201. A throttle valve that adjusts the amount of intake air is provided in the intake pipe. A fuel injection valve that injects fuel into each cylinder is provided in the intake manifold. In another embodiment, the engine may be a direct injection engine in which the fuel injection valve is provided in the combustion chamber rather than in the intake manifold.

[0022] An exhaust manifold (not shown) and an exhaust pipe 208 are provided downstream of the engine 201. One end of the exhaust pipe 208 is connected to the exhaust manifold, and the other end of the exhaust pipe 208 is connected to a catalytic device (three-way catalyst). Exhaust gas discharged from an exhaust port of the engine 201 is guided to the exhaust pipe 208 via the exhaust manifold.

[0023] The crankshaft, which is the output shaft of the engine 201, is connected to the input side of a power transmission system 205, and the power output from the engine 201 is transmitted to the drive wheels via the power transmission system 205.

[0024] A gas sensor 2 is attached to the exhaust pipe 208 to detect the concentration of a specific gas (for example, oxygen gas) contained in the exhaust gas flowing through the exhaust pipe 208. Details of the gas sensor 2 will be described later.

[0025] Motor 202 (motor with power generation function) is composed of a motor generator that is regeneratively driven when HV vehicle 200 decelerates and is capable of generating power using the kinetic energy of drive wheels 206. The power generated by motor 202 is supplied to battery 204 via inverter 203. Inverter 203 converts the AC power generated by motor 202 into DC power, and the DC power obtained thereby is supplied to battery 10. In addition, inverter 203 supplies power to motor 202 by PWM control (i.e., pulse width modulation control).

[0026] The battery 204 is a driving battery and is made up of a battery that can charge and discharge power (for example, a lithium ion battery, a lithium ion polymer battery, etc.). The battery 204 stores the power to be supplied to the motor 202.

[0027] The output side of the power transmission system 205 is connected to the axle of the drive wheels 206. The power output from the engine 201 or the motor 202 is transmitted to the drive wheels 206 via the power transmission system 205 and the axle. The power transmission system 205 includes a transmission, and the power output from the engine 201 or the motor 202 is changed in speed by the power transmission system 205 and then transmitted to the drive wheels 206.

[0028] In the HV vehicle 200, the drive wheels 206 to which the power (driving force) output from the drive power source (engine 201 or motor 202) is transmitted may be either the front wheels or the rear wheels. Furthermore, the power output from the output side of the power transmission system 205 may be transmitted to both the front wheels and the rear wheels via a propeller shaft (not shown).

[0029] The ECU (Electronic Control Unit) 207 is a computer that performs various controls in the HV vehicle 200. The ECU 207 is equipped with computer hardware such as a processor and memory, and operates in accordance with installed software such as an OS (Operating System) and application programs.

[0030] The ECU 207 is electrically connected to the fuel injection valve, the ignition circuit, the distributor, the control device 3 of the gas sensor control device 1, etc. The ignition circuit is an electric circuit that generates a high-voltage current that drives the spark plug based on a signal output from the ECU 207. The distributor distributes the high-voltage current output from the ignition circuit to the spark plug in synchronization with the crank angle. A rotation sensor that detects the crank angle (i.e., the engine speed) is attached to the distributor. The control device 3 controls the operation of the gas sensor 2.

[0031] The ECU 207 executes various processes, such as a process for performing air-fuel ratio feedback control of the engine 201, and a process for selecting and switching between driving modes.

[0032] Next, we will explain the gas sensor control device 1. As shown in FIG.

[0033] The gas sensor 2 is used for air-fuel ratio feedback control of the engine 201, and is a full-range air-fuel ratio sensor that detects exhaust gas flowing in an exhaust pipe 208. The operation of the gas sensor 2 is controlled by a control device 3. The gas sensor 2 operates using power supplied from a battery 204 via an ECU 207.

[0034] The gas sensor 2 includes a sensor element (detection cell) 51 that detects the concentration of oxygen gas (specific gas) contained in exhaust gas, a heater element 53 that heats the sensor element 51, and a housing (not shown) that accommodates them.

[0035] The sensor element 51 has a laminated structure of solid electrolyte bodies 55, 57 and insulating substrates 59, 61. The solid electrolyte bodies 55, 57 are formed of a material mainly composed of partially stabilized zirconia (YSZ) using yttria as a stabilizer, and have oxygen ion conductivity. The insulating substrates 59, 61 are formed of a material mainly composed of alumina. The heater element 53 is laminated on the sensor element 51 to quickly activate the solid electrolyte bodies 55, 57 and maintain stability of their activity.

[0036] In detail, the sensor element 51 comprises a detection chamber 63, a diffusion-controlling section 65, an oxygen pump cell (hereinafter sometimes referred to as the "Ip cell") 67, an oxygen partial pressure detection cell (hereinafter sometimes referred to as the "Vs cell") 69, and insulating substrates 59, 61.

[0037] The detection chamber 63 is a small space into which the exhaust gas flowing inside the exhaust pipe 208 is introduced. The diffusion-controlling section 65 is formed of a porous material (for example, alumina) and adjusts the inflow rate when the exhaust gas is introduced into the detection chamber 63.

[0038] The Ip cell 67 includes a solid electrolyte body 55 and a pair of porous electrodes 71, 73 formed to sandwich the solid electrolyte body 55. These electrodes 71, 73 are formed of a material containing platinum (Pt) as a main component, for example. When a current is supplied between the electrodes 71, 73, the Ip cell 67 pumps oxygen in and out (so-called oxygen pumping) between the atmosphere (exhaust gas) in contact with the electrode 71 and the atmosphere (the atmosphere inside the detection chamber 63) in contact with the electrode 73.

[0039] The insulating base 61 has an opening 75 at a position that will be above the electrode 71. The opening 75 is provided with a protective layer 77 made of a porous material, for example, alumina.

[0040] The Vs cell 69 includes a solid electrolyte body 57 and a pair of porous electrodes 79 and 81 formed to sandwich the solid electrolyte body 57. These electrodes 79 and 81 are formed of a material mainly composed of platinum (Pt), for example. Of these, electrode 79 is provided on the surface of the solid electrolyte body 57 facing the detection chamber 63, and electrode 81 functions as an oxygen reference electrode that maintains an oxygen concentration that serves as a reference for detecting the oxygen concentration in the detection chamber 63.

[0041] The Vs cell 69 generates a voltage (electromotive force) mainly in response to the difference in oxygen partial pressure between the atmospheres separated by the solid electrolyte body 57 (the atmosphere in the detection chamber 63 in contact with the electrode 79 and the atmosphere in contact with the electrode 81).

[0042] The heater element 53 is an element that heats and activates the sensor element 51 (particularly the solid electrolyte bodies 55 and 57), and includes a heater (heating resistor) 83 and insulating bases 85 and 87. The heater 83 is made of a material mainly containing platinum. The heater 83 is sandwiched between the insulating bases 85 and 87. The insulating bases 85 and 87 are made of a material mainly containing alumina.

[0043] The control device 3 includes a microcomputer (hereinafter sometimes referred to as "mc") 91, an application specific integrated circuit (hereinafter sometimes referred to as "ASIC") 93, and a heater voltage supply circuit 95. The mc 91 is a microcomputer chip equipped with a CPU (Central Processing Unit) 91a, a ROM (Read Only Memory) 91b, a RAM (Random Access Memory) 91c, and the like, each having a known configuration.

[0044] The ASIC 93 includes an Ip detection circuit 101, an Ip drive circuit 103, a resistance detection circuit 105, a voltage output circuit 107, a reference voltage comparison circuit 109, an Icp supply circuit 111, and the like.

[0045] The Ip detection circuit 101 converts the current Ip flowing between the electrodes 71 and 73 of the Ip cell 67 into a voltage and outputs the converted voltage as a detection signal to the microcomputer 91. The resistance detection circuit 105 is a circuit that periodically passes a predetermined current through the Vs cell 69 and detects the amount of voltage change (amount of change in voltage Vs) obtained in response to this current flow. A value indicating the amount of change in voltage Vs detected by this resistance detection circuit 105 is output to the microcomputer 91.

[0046] The microcomputer 91 determines the impedance Ri of the Vs cell 69 based on the value output from the resistance detection circuit 105 and a table stored in ROM 91b that associates the amount of change in voltage Vs with the impedance Ri of the Vs cell 60. The impedance Ri of the Vs cell 69 correlates with the temperature of the Vs cell 69, i.e., the temperature of the entire sensor element 51. The microcomputer 91 detects the temperature of the gas sensor 2 (sensor element 51) based on the impedance Ri of the Vs cell 69.

[0047] The voltage output circuit 107 detects the electromotive force Vs generated between the electrodes 79 and 81 of the Vs cell 69. The reference voltage comparison circuit 109 compares the electromotive force Vs detected by the voltage output circuit 107 with a predetermined reference voltage and outputs the comparison result to the Ip drive circuit 103. Based on the comparison result output from the reference voltage comparison circuit 109, the Ip drive circuit 103 controls the magnitude and direction of the current Ip supplied between the electrodes 71 and 83 of the Ip cell 67. The Icp supply circuit 111 supplies a minute current Icp that flows from the electrode 81 to the electrode 79 of the Vs cell 69.

[0048] As will be described later, the heater voltage supply circuit 95 generates the voltage Vh to be applied to both ends of the heater 83 under known PI control in response to instructions from the CPU 91a (heater control unit 91d) of the microcomputer 91, and applies a predetermined voltage (for example, 12 V in the detection mode described later) to both ends of the heater (heating resistor) 83, causing the heater 83 to generate heat.

[0049] Here, a brief description will be given of the basic operation of the gas sensor 2. Here, a description will be given of the operation of detecting the oxygen concentration of the detection target gas (air-fuel ratio of the exhaust gas) using the gas sensor 2. When detecting the air-fuel ratio of the exhaust gas, a reference voltage (for example, 450 mV) to be compared is set in the reference voltage comparison circuit 109.

[0050] First, the Icp supply circuit 111 supplies a minute current Icp from the electrode 81 of the Vs cell 69 to the electrode 79 via the solid electrolyte body 57. This current flow causes oxygen in the exhaust gas to become oxygen ions, which migrate from the electrode 79 side to the electrode 81 side via the solid electrolyte body 57.

[0051] When a minute current Icp is supplied to the Vs cell 69, oxygen ions move from the electrode 79 side to the electrode 81 side, and an oxygen concentration atmosphere is generated that serves as a reference for generating an electromotive force Vs corresponding to the oxygen concentration in the exhaust gas.

[0052] The voltage output circuit 107 detects the electromotive force Vs between the two electrodes 79, 81 and outputs the detected electromotive force Vs to the reference voltage comparison circuit 109. The reference voltage comparison circuit 109 compares the electromotive force Vs with a reference voltage and outputs the comparison result to the Ip drive circuit 103.

[0053] Based on the comparison result by the reference voltage comparison circuit 109, the Ip drive circuit 103 controls the magnitude and direction of the current Ip supplied between the electrodes 71, 73 of the Ip cell 67 so that the electromotive force Vs becomes the reference voltage. This causes the Ip cell 67 to pump oxygen into or out of the detection chamber 63.

[0054] Here, when the air-fuel ratio of the exhaust gas flowing into the detection chamber 63 is richer than the stoichiometric air-fuel ratio, the magnitude and direction of the current Ip supplied between the electrodes 71, 73 are controlled in the Ip cell 67 so that oxygen is pumped into the detection chamber 63 from the outside. On the other hand, when the air-fuel ratio of the exhaust gas flowing into the detection chamber 63 is leaner than the stoichiometric air-fuel ratio, the magnitude and direction of the current Ip supplied between the electrodes 71, 73 are controlled in the Ip cell 67 so that oxygen is pumped out of the detection chamber 63 to the outside.

[0055] The current Ip at this time is converted into a voltage in the Ip detection circuit 101, and the converted current Ip is output as a detection signal to the microcomputer 91. The microcomputer 91 calculates a value corresponding to the concentration of oxygen contained in the target gas and also the air-fuel ratio of the exhaust gas based on the detection signal. In this way, the oxygen concentration of the target gas (air-fuel ratio of the exhaust gas) is detected using the gas sensor 2.

[0056] Next, a description will be given of a method for controlling the energization of the heater 83 (a heating control method of the gas sensor control device 1) performed in the gas sensor control device 1. Note that this energization control of the heater 83 is performed while the HV vehicle 200 is traveling.

[0057] 2 is a block diagram showing an example of the functional configuration of the microcomputer 91. In the microcomputer 91, a heater control unit 91d, a first determination unit 91e, a second determination unit 91f, a third determination unit 91g, a fourth determination unit 91h, and a fifth determination unit 91i are implemented by software.

[0058] Here, the processing executed in the heater control unit 91d and the like of the microcomputer 91 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing processing executed in the microcomputer 91 related to the energization control of the heater 83. When the ignition switch is operated and the hybrid system (ECU 207 and the like) of the HV vehicle 200 is started up, the ECU 207 executes processing to select the motor driving mode as the driving mode. In this situation, when the user (driver) depresses the accelerator pedal, the HV vehicle 200 starts to drive in the motor driving mode from a stopped state. Thereafter, the ECU 207 executes processing to switch the driving mode as appropriate depending on the driving conditions (required driving force, etc.) of the HV vehicle 200.

[0059] While the HV vehicle 200 is traveling, the first determination unit 91e executes a process to determine whether the traveling mode is the motor traveling mode (i.e., whether it is the motor traveling mode or the engine traveling mode) as shown in step S11 (first determination step). Information on the traveling mode of the HV vehicle is periodically supplied from the ECU 207 to the microcomputer 91, and the first determination unit 91e can acquire the traveling mode information as appropriate. If the first determination unit 91e determines in step S11 that the traveling mode is the motor traveling mode, the process proceeds to step S12. On the other hand, if the first determination unit 91e determines in step S11 that the traveling mode is not the motor traveling mode (i.e., the engine traveling mode), the process proceeds to step S21.

[0060] In step S21, the heater control unit 91d executes a process of causing the heater 83 to generate heat at an activation temperature (e.g., 750°C) that brings the sensor element (detection cell) 51 into a detectable state. The heater control unit 91d applies a predetermined voltage (heater control voltage 1) to both ends of the heater (heating resistor) 83 via the heater voltage supply circuit 95, with a predetermined activation temperature as the target. The heater control voltage 1 is, for example, 12 V. In this specification, a mode in which the heater 83 is energized and controlled is referred to as a "heater control mode." A heater control mode in which the heater 83 generates heat at the activation temperature (e.g., 750°C) is referred to as a "detection mode." A heater control mode in which the heater 83 is deenergized and the heater 83 stops generating heat is referred to as a "stop mode." When the process in step S21 ends, the process returns to step S11.

[0061] In step S12, the second determination unit 91f executes a process of determining whether or not the charge level of the battery 204 exceeds a first threshold value α (second determination step). The first threshold value α is a predetermined value stored in the ROM 91b. The first threshold value α is set, for example, as a charge level that is 50% of the charge level of the battery 204 when the battery 204 is fully charged. If the second determination unit 91f determines in step S12 that the charge level of the battery 204 exceeds the first threshold value α, the process proceeds to step S13. On the other hand, if the second determination unit 91f determines in step S12 that the charge level of the battery 204 does not exceed the first threshold value α (that is, if the charge level is determined to be equal to or lower than the first threshold value α), the process proceeds to step S20.

[0062] When the process proceeds to step S20, the heater control unit 91d executes a process of causing the heater 83 to generate heat at an activation temperature (e.g., 750°C) that puts the sensor element 51 into a detectable state. The process content of step S20 is basically the same as that of step S21 described above. When the process in step S20 ends, the process returns to step S11 again.

[0063] In step S13, the third determination unit 91g executes a process of determining whether the heater control mode is the stop mode (third determination step). If the third determination unit 91g determines in step S13 that the heater control mode is the stop mode, the process proceeds to step S14. On the other hand, if the third determination unit 91g determines in step S13 that the heater control mode is not the stop mode, the process proceeds to step S15.

[0064] In step S14, the fourth determination unit 91h executes a process of determining whether or not the charge level of the battery 204 is below a second threshold value β (fourth determination step). The second threshold value β is a predetermined value that is set to be greater than the first threshold value α (β>α). If it is determined in step S14 that the charge level of the battery 204 is below the second threshold value β, the process proceeds to step S16. On the other hand, if it is determined in step S14 that the charge level of the battery 204 is not below the second threshold value β (i.e., if it is determined that the charge level is equal to or greater than the second threshold value β), the process proceeds to step S17.

[0065] When the process proceeds to step S16, the heater control unit 91d controls the energization of the heater 83 in a standby mode in which the heater 83 generates heat at a standby temperature (e.g., 550°C) lower than the activation temperature. The heater control unit 91d applies a predetermined voltage (heater control voltage 2) to both ends of the heater (heating resistor) 83 via the heater voltage supply circuit 95, with a predetermined standby temperature as the target. The heater control voltage 2 is a value lower than the heater control voltage 1 described above. In this specification, the heater control mode in which the heater 83 generates heat at a standby temperature lower than the activation temperature is referred to as the "standby mode," as described above. When the process in step S16 ends, the process returns to step S11 again.

[0066] In step S17, the heater control unit 91d maintains the heater control mode in the stop mode and controls the energization of the heater 83. Therefore, in step S17, the state in which the heater 83 is stopped from generating heat is maintained. When the processing in step S17 ends, the process returns to step S11 again.

[0067] In step S15, the fifth determination unit 91i executes a process of determining whether or not the charge level of the battery 204 exceeds a third threshold value γ (fifth determination step). The third threshold value γ is a predetermined value that is set to be greater than the second threshold value (γ>β). If it is determined in step S15 that the charge level of the battery 204 exceeds the third threshold value γ, the process proceeds to step S18. On the other hand, if it is determined in step S15 that the charge level of the battery 204 does not exceed the third threshold value γ (i.e., if it is determined that the charge level is equal to or less than the third threshold value γ), the process proceeds to step S19.

[0068] When the process proceeds to step S18, the heater control unit 91d performs power supply control in the stop mode for the heater 83. That is, in step S18, the heater 83 stops generating heat. When the process in step S18 ends, the process returns to step S11 again.

[0069] In step S19, the heater control unit 91d controls the energization of the heater 83 in a standby mode in which the heater 83 generates heat at a standby temperature (for example, 550°C) lower than the activation temperature. When the process in step S19 ends, the process returns to step S11 again.

[0070] The heater control unit 91d is configured to select and switch the heater control mode depending on the charge level of the battery 204.

[0071] Fig. 4 is an explanatory diagram showing the relationship between the charge level of battery 204 and the driving mode in hybrid vehicle 200, and the relationship between the charge level of battery 204 and the heater control mode. Fig. 4 shows a graph in which the vertical axis corresponds to the charge level of battery 204 and the horizontal axis corresponds to time. Here, the processing content executed by microcomputer 91 (heater control unit 91, etc.) at each of times t1 to t8 shown in the graph of Fig. 4 will be described with reference to the flowchart of Fig. 3.

[0072] At the timing of time t1, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L1 of the battery 204 satisfies β < L1 < γ. In this case, the energization control of the heater 83 is performed by shifting the flowchart of FIG. 3 in the order of step S11, step S12, step S13, step S14, and step S17. Then, in step S17, the heater control unit 91d performs the energization control of the heater 83 while maintaining the heater control mode in the stop mode. That is, the heat generation of the heater 83 is stopped. Thus, at the timing of time t1, since the charge level L1 of the battery 204 is sufficiently high (β < L1) and driving in the motor driving mode is expected for some time to come, the heater control mode is maintained in the stop mode.

[0073] At the timing of time t2, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L2 of the battery 204 exceeds the first threshold α and is below the second threshold β (that is, α < L2 < β). In this case, the energization control of the heater 83 is performed by shifting the flowchart of FIG. 3 in the order of step S11, step S12, step S13, step S14, and step S16. Then, in step S16, the heater control unit 91d switches the heater control mode from the stop mode to the standby mode and performs the energization control of the heater 83 in the standby mode. The heater 83 generates heat so as to reach the standby temperature (for example, 550°C). Thus, at the timing of time t2, since the charge level L2 of the battery 204 is below the second threshold β and the driving mode is expected to switch to the engine driving mode in the near future, the heater control mode is switched to the standby mode.

[0074] At the timing of time t3, the driving mode of the HV vehicle 200 is the engine driving mode, and the charge level L3 of the battery 204 is less than the first threshold value α. The energization control of the heater 83 in this case is performed so as to shift the flowchart of FIG. 3 in the order of step S11 and step S21. Then, in step S21, the heater control unit 91d switches the heater control mode from the standby mode to the detection mode, and performs energization control of the heater 83 in the detection mode. The heater 83 generates heat so as to reach the activation temperature (for example, 750°C). Thus, at the timing of time t3, since the driving mode has switched to the engine driving mode, the heater control mode becomes the detection mode.

[0075] At the timing of time t4, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L4 of the battery 204 exceeds the first threshold value α and is less than the third threshold value γ (that is, α < L4 < γ). The energization control of the heater 83 in this case is performed so as to shift the flowchart of FIG. 3 in the order of step S11, step S12, step 13, step S15, and step S19. Then, in step S19, the heater control unit 91d switches the heater control mode from the detection mode to the standby mode, and performs energization control of the heater 83 in the standby mode. The heater 83 generates heat so as to reach the standby temperature (for example, 550°C). Thus, at the timing of time t4, although the driving mode has switched from the engine driving mode to the motor driving mode, since the charge level L4 of the battery 204 is less than the third threshold value γ, there is a possibility that the driving mode will switch back to the engine driving mode in the near future, so the heater control mode becomes the standby mode.

[0076] At the timing of time t5, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L5 of the battery 204 exceeds the third threshold γ (that is, γ < L5). In this case, the energization control of the heater 83 is performed so as to transition through the flowchart of FIG. 3 in the order of step S11, step S12, step 13, step S15, and step S18. Then, in step S18, the heater control unit 91d switches the heater control mode from the standby mode to the stop mode and performs the energization control of the heater 83 in the stop mode. That is, the heat generation of the heater 83 is stopped. Thus, at the timing of time t5, the driving mode is the motor driving mode, and moreover, since the charge level L5 of the battery 204 exceeds the third threshold and is sufficiently high, driving in the motor driving mode is expected for some time to come, so the heater control mode is switched to the stop mode.

[0077] At the timing of time t6, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L6 of the battery 204 exceeds the second threshold β while being lower than the third threshold γ (that is, β < L6 < γ). The content of the processing by the heater control unit 91d in this case is the same as in the case of time t1.

[0078] At the timing of time t7, the driving mode of the HV vehicle 200 is the motor driving mode, and the charge level L7 of the battery 204 exceeds the first threshold α while being lower than the second threshold β (that is, α < L7 < β). The content of the processing by the heater control unit 91d in this case is the same as in the case of time t2.

[0079] At time t8, the driving mode of the HV vehicle 200 is the motor driving mode, but the charge level L8 of the battery 204 is equal to or lower than the first threshold value α. In this case, the energization control of the heater 83 is performed by progressing through the flowchart of FIG. 3 in the order of steps S11, S12, and S20. In step S20, the heater control unit 91d switches the heater control mode from the standby mode to the detection mode and performs energization control of the heater 83 in the detection mode. In this case, in anticipation of the ECU 17 immediately switching the driving mode from the motor driving mode to the engine driving mode, the heater control unit 91d switches the heater control mode to the detection mode and performs energization control of the heater 83 in the detection mode.

[0080] As described above, in the gas sensor control device 1 of this embodiment, when the first determination unit 91e determines that the mode is the motor driving mode and the second determination unit 91f determines that the temperature exceeds the first threshold value α, the heater control unit 91d controls the supply of electricity to the heater 83 in either a standby mode in which the heater 83 generates heat at a standby temperature (e.g., 550°C) lower than the activation temperature (e.g., 750), or a stop mode in which the supply of electricity to the heater 83 is stopped. Therefore, the gas sensor control device 1 can reduce the power consumption of the heater 83 in the motor driving mode.

[0081] Furthermore, in the gas sensor control device 1 of this embodiment, the heater control section 91d selects either the standby mode or the stop mode in accordance with the charge level of the battery 204, and controls the energization of the heater 83. Therefore, the gas sensor control device 1 can reduce the power consumption of the heater 83 in the motor driving mode based on the charge level of the battery.

[0082] Furthermore, in the gas sensor control device 1 of this embodiment, when the charge level of the battery 204 falls below the second threshold value β (where β > α) in the stop mode, the heater control unit 91d switches the mode to the standby mode and controls the energization of the heater 83. In this way, by grasping the charge level of the battery 204 in the stop mode, it is possible to predict that the driving mode will switch from the motor driving mode to the engine driving mode in the near future. Therefore, the sensor element (detection cell) 51 of the gas sensor 2 can be preheated to a standby temperature, which is a relatively high temperature. Therefore, when the driving mode is switched from the motor driving mode to the engine driving mode in the near future, the gas sensor control device 1 can quickly bring the sensor element (detection cell) 51 of the gas sensor into a state where it can detect gas. The gas sensor control device 1 reduces power consumption of the heater 83 of the gas sensor 2 during driving in the motor driving mode, and maintains the sensor element (detection cell) 51 of the gas sensor 2 in a state where it can detect gas quickly when the driving mode is switched from the motor driving mode to the engine driving mode.

[0083] Furthermore, in the gas sensor control device 1 of this embodiment, when the charge level of the battery 204 exceeds a third threshold value γ (where γ>β) in the standby mode, the heater control unit 91d switches to the stop mode and controls the energization of the heater 83. In this way, by understanding the charge level of the battery 204 in the standby mode, it is predicted that the vehicle will be driven in the motor driving mode for some time to come, and the heater control mode becomes the stop mode. Therefore, the gas sensor control device 1 can reduce the power consumption of the heater 83 in the motor driving mode.

[0084] Furthermore, in the gas sensor control device 1 of this embodiment, when the charge level of the battery 204 is equal to or higher than the second threshold value β (where β > α) in a mode other than the stop mode (i.e., the detection mode or the standby mode), the heater control unit 91d switches from the detection mode to the standby mode or maintains the standby mode to control the energization of the heater 83. In this way, by determining the charge level of the battery 204 in a mode other than the stop mode, it is possible to determine that the driving mode may switch back to the engine driving mode in the near future, and the heater control mode becomes the standby mode. Therefore, the gas sensor control device 1 can quickly bring the sensor element (detection cell) 51 of the gas sensor into a state where it can detect gas when the driving mode is switched from the motor driving mode to the engine driving mode in the near future. In this gas sensor control device 1, power consumption of the heater 83 of the gas sensor 2 is suppressed during driving in the motor driving mode, and the sensor element (detection cell) 51 of the gas sensor 2 is maintained in a state where it can detect gas when the driving mode is switched from the motor driving mode to the engine driving mode.

[0085] The heating control method of the gas sensor control device 1 includes a first determination step of determining whether the driving mode is an engine driving mode that uses the driving force of the engine 201, or a motor driving mode that uses only the driving force of the motor 202; a second determination step of determining whether the charge level of the battery 204 exceeds a first threshold value α; and, if the determination result of the first determination step is the motor driving mode and the second determination step determines that the charge level exceeds the first threshold value α, a current control step (steps S16, S17, S18, and S19) in which the heater control unit 91d controls the current supply to the heater 83 in either a standby mode in which the heater 83 generates heat at a standby temperature lower than the activation temperature, or a stop mode in which the current supply to the heater 83 is stopped.

[0086] In the power supply control process (steps S16, S17, S18, and S19), the heater control unit 91d selects either the standby mode or the stop mode depending on the charge level of the battery 204, and controls the power supply to the heater 83.

[0087] In the power supply control process (step S16), when the charge level of the battery 204 falls below the second threshold value β (where β>α) in the stop mode, the heater control unit 91d switches the heater control mode to the standby mode and controls the power supply to the heater 83.

[0088] In the power supply control process (step S18), when the charge level of the battery 204 exceeds a third threshold value γ (where γ>β) in the standby mode, the heater control unit 91d switches the heater control mode to the stop mode and controls the power supply to the heater 83.

[0089] In the power supply control process (step S19), when the battery 204 is in a mode other than the stop mode (i.e., the detection mode or the standby mode), if the charge level of the battery 204 is equal to or greater than the second threshold value β (where β>α), the detection mode is switched to the standby mode or the standby mode is maintained, and the power supply to the heater 83 is controlled. [Explanation of symbols]

[0090] 1...gas sensor control device, 2...gas sensor, 3...control device, 51...sensor element (detection cell), 83...heater, 91...microcomputer, 91d...heater control unit, 91e...first determination unit, 91f...second determination unit, 200...hybrid vehicle, 201...engine, 202...motor with power generation function, 204...battery, 208...exhaust pipe

Claims

1. A gas sensor control device is attached to an exhaust pipe of a hybrid vehicle that has an engine and a motor with a power generating function as driving power sources, and that also has a battery that supplies power to the motor or stores power from the motor, and that controls a gas sensor having a detection cell that detects the concentration of a specific gas and a heater that heats the detection cell, a heater control unit that controls energization of the heater and causes the heater to generate heat at an activation temperature that puts the detection cell into a detectable state when the hybrid vehicle is in an engine drive mode that utilizes the driving force of the engine, The first threshold value α is a predetermined value, the second threshold value β is a predetermined value that is set to be greater than the first threshold value α; the third threshold value γ is a predetermined value that is set to be greater than the second threshold value β; a first determination unit that determines whether the driving mode is the engine driving mode or a motor driving mode that uses only the driving force of the motor; a second determination unit that determines whether or not the charge level of the battery exceeds the first threshold value α; when the first determination unit determines that the vehicle is in the motor driving mode and the second determination unit determines that the vehicle temperature exceeds the first threshold value α, the heater control unit controls the energization of the heater in either a standby mode in which the heater generates heat at a standby temperature lower than the activation temperature, or a stop mode in which energization of the heater is stopped; When the charge level of the battery falls below the second threshold β in the stop mode, the heater control unit switches to the standby mode and controls the energization of the heater; When the charge level of the battery exceeds the third threshold value γ in the standby mode, the heater control unit switches the mode to the stop mode and controls the energization of the heater.

2. 2. The gas sensor control device according to claim 1, wherein the heater control section selects either the standby mode or the stop mode in accordance with the charge level of the battery to control the energization of the heater.

3. A heating control method for a gas sensor control device, comprising: a gas sensor attached to an exhaust pipe of an engine of a hybrid vehicle having an engine and a motor with a power generating function as driving power sources, and a battery for supplying power to the motor or storing power from the motor, the gas sensor having a detection cell for detecting the concentration of a specific gas and a heater for heating the detection cell; and a heater control unit for controlling the energization of the heater and causing the heater to generate heat at an activation temperature that enables detection of the detection cell when the hybrid vehicle is in an engine driving mode that utilizes the driving power of the engine, The first threshold value α is a predetermined value, the second threshold value β is a predetermined value that is set to be greater than the first threshold value α; the third threshold value γ is a predetermined value that is set to be greater than the second threshold value β; a first determination step of determining whether the driving mode is the engine driving mode or a motor driving mode that uses only the driving force of the motor; a second determination step of determining whether the charge level of the battery exceeds the first threshold value α; a power supply control step of, when the determination result of the first determination step is the motor running mode and the second determination step determines that the temperature exceeds the first threshold value α, the heater control unit controls power supply to the heater in either a standby mode in which the heater is caused to generate heat at a standby temperature lower than the activation temperature, or a stop mode in which power supply to the heater is stopped; In the power supply control step, when the charge level of the battery falls below the second threshold β in the stop mode, the heater control unit switches to the standby mode and controls power supply to the heater; In the power supply control step, when the charge level of the battery exceeds the third threshold value γ while in the standby mode, the heater control unit switches to the stop mode and controls the power supply to the heater.

4. The heating control method according to claim 3 , wherein in the power supply control step, the heater control unit selects either the standby mode or the stop mode according to a charge level of the battery to control the power supply to the heater.

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