Gas sensor deterioration determination device

Abstract

To provide a deterioration determination device for a gas sensor capable of securing an opportunity for a deterioration determination of the gas sensor.SOLUTION: A deterioration determination device determines deterioration of a gas sensor provided in an exhaust passage of an internal combustion engine. The deterioration determination device for the gas sensor includes: a fuel control section controlling supply of fuel to the internal combustion engine; and a determination section for determining whether or not the gas sensor is deteriorated during stop of the fuel supply to the internal combustion engine. When an air-fuel ratio detected by the gas sensor is on the lean side of a predetermined value, the fuel control section supplies the fuel. When the air-fuel ratio detected by the gas sensor is on the rich side of the predetermined value, the fuel control section stops the supply of the fuel and the determination section makes a determination.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a deterioration determining device for a gas sensor. [Background technology]

[0002] A catalyst and a gas sensor are provided in the exhaust passage of an internal combustion engine. The catalyst removes harmful substances in the exhaust and purifies the exhaust. The gas sensor outputs a signal (e.g., a current) according to, for example, the air-fuel ratio. Deterioration of the catalyst can be detected based on the signal output by the gas sensor. If the gas sensor deteriorates, it is not possible to detect an accurate air-fuel ratio, and it becomes difficult to accurately determine the deterioration of the catalyst. Therefore, there is a demand for a technology to determine whether the gas sensor has deteriorated. As an example, a technology has been developed to determine the deterioration of the gas sensor when fuel is cut off (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-052462 A Summary of the Invention [Problem to be solved by the invention]

[0004] By stopping the supply of fuel to the internal combustion engine (fuel cut), the air-fuel ratio shifts to the lean side. The output value of the gas sensor also changes according to the change in the air-fuel ratio. For example, deterioration of the gas sensor can be determined based on the change in the output value of the gas sensor when the air-fuel ratio shifts from stoichiometry to lean.

[0005] However, when fuel cut is performed when the air-fuel ratio is lean, it is difficult to determine the deterioration of the gas sensor. Therefore, an object of the present invention is to provide a gas sensor deterioration determination device that can secure an opportunity to determine the deterioration of the gas sensor. [Means for solving the problem]

[0006] The object of the present invention is to provide a deterioration determination device for determining deterioration of a gas sensor provided in an exhaust passage of an internal combustion engine, the deterioration determination device including: a fuel control unit that controls the supply of fuel to the internal combustion engine; and a determination unit that determines whether the gas sensor has deteriorated while the supply of fuel to the internal combustion engine is stopped, and when an air-fuel ratio detected by the gas sensor is leaner than a predetermined value, The determination unit does not perform the determination, The air-fuel ratio detected by the gas sensor is on the rich side of the predetermined value. and when the fuel control unit supplies the fuel, the determination unit does not perform the determination, and when the fuel control unit stops the supply of the fuel and the air-fuel ratio detected by the gas sensor is on the rich side of the predetermined value, The determination unit The above Judgment During the stop of the fuel supply, the determination unit continues the determination until the determination is completed, and when the fuel control unit resumes the fuel supply after the fuel supply is stopped and before the determination is completed, the determination unit interrupts the determination. This can be achieved by a gas sensor deterioration determination device. Effect of the Invention

[0007] It is possible to provide a gas sensor deterioration determining device capable of ensuring an opportunity to determine deterioration of a gas sensor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a hybrid vehicle. [Diagram 2] FIG. 2 is a schematic diagram illustrating an internal combustion engine. [Diagram 3] FIG. 3 is a diagram illustrating the characteristics of a gas sensor. [Figure 4] FIG. 4 is a flowchart illustrating a process according to the embodiment. [Diagram 5] FIG. 5 is a flowchart illustrating a process according to the embodiment. [Figure 6] FIG. 6 is a flowchart illustrating a process according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating a time chart. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the gas sensor deterioration determination device of this embodiment will be described with reference to the drawings. Fig. 1 is a schematic diagram illustrating a hybrid electric vehicle (Hybrid Electric Vehicle) 1. The hybrid vehicle 1 includes an internal combustion engine 10, a motor generator (motor MG1 and motor MG2), a charger 24, a battery 32, a battery ECU (Electronic Control Unit) 34, an HV (Hybrid) ECU 40, an engine ECU 42, and a motor ECU 44.

[0010] The hybrid vehicle 1 is capable of HV running and EV running. In HV running, the operation of the internal combustion engine 10 and the operation of the motor MG are coordinated. In EV running, the internal combustion engine 10 is not operated, and the vehicle runs by operating the motor MG using the power of the battery 32. The CS (Charge Sustaining) mode is a mode in which the vehicle runs while maintaining the state of charge (SOC) of the battery 32 near the control center, and the CD (Charge Depleting) mode is a mode in which the vehicle runs by consuming the state of charge SOC of the battery 32.

[0011] The motors MG1 and MG2 are driven by electric power supplied from a battery 32. The accelerator opening sensor 11 detects the amount of depression of the accelerator pedal (accelerator opening).

[0012] The planetary gear 14 is connected to a crankshaft (not shown) of the internal combustion engine 10 via a damper 12, and is also connected to a motor MG1 and a motor MG2. The motor MG2 is connected to driving wheels 1a of the hybrid vehicle 1 via a differential gear 16. Driving forces generated by the internal combustion engine 10, the motor MG1, and the motor MG2 are transmitted to the driving wheels 1a, and the hybrid vehicle 1 runs.

[0013] The hybrid vehicle 1 is, for example, a plug-in hybrid vehicle. The power plug 26 can be connected to an external power source outlet outside the hybrid vehicle 1. The charger 24 includes, for example, an AC / DC converter, a DC / DC converter, etc., and can convert AC power input from the external power source via the power plug 26 into DC power and return the voltage of the DC power. The battery 32 includes, for example, a lithium-ion secondary battery, a nickel-metal hydride secondary battery, etc. The battery 32 can be charged by supplying power to the battery 32 from the external power source via the power plug 26 and the charger 24.

[0014] The inverter 20 is electrically connected to the motor MG1, the charger 24, and the battery 32. The inverter 22 is electrically connected to the motor MG2, the charger 24, and the battery 32. The inverter 20 converts the AC power generated by the motor MG1 into DC power and supplies it to the battery 32, and converts the DC power of the battery 32 into AC power and supplies it to the motor MG1. The inverter 22 similarly converts between DC power and AC power.

[0015] 2 is a schematic diagram illustrating an internal combustion engine 10. The internal combustion engine 10 outputs power by burning fuel such as gasoline. As shown in FIG. 2, the internal combustion engine 10 has a cylinder block 50, a cylinder head 51, an intake valve 64, and an exhaust valve 66.

[0016] A cylinder head 51 is attached on top of the cylinder block 50. A crankshaft 60 is housed in the cylinder block 50. One end of a connecting rod 61 is connected to a piston 62, and the other end is connected to the crankshaft 60. A combustion chamber 63 is defined by the cylinder block 50, the cylinder head 51, and the piston 62.

[0017] An intake valve 64, an exhaust valve 66, a fuel injector 58, and an ignition plug 59 are provided in the cylinder head 51. The fuel injector 58 performs in-cylinder injection. The fuel injector 58 is provided in the intake passage 52 and may perform port injection. A crank angle sensor 68 is provided in the cylinder block 50 and detects the rotation angle of the crankshaft 60.

[0018] An intake passage 52 and an exhaust passage 53 are connected to a cylinder head 51. In the intake passage 52, an air cleaner 54, an air flow meter 55, and a throttle valve 56 are provided in this order from the upstream side. The air cleaner 54 removes dust and other particles from the air in the intake passage 52 to purify the air. The air flow meter 55 detects the flow rate of air in the intake passage 52. The larger the opening of the throttle valve 56, the greater the air flow rate. The smaller the opening of the throttle valve 56, the smaller the air flow rate.

[0019] When the intake valve 64 opens, the intake passage 52 and the combustion chamber 63 communicate with each other. Air in the intake passage 52 is introduced into the combustion chamber 63. The fuel injection valve 58 injects fuel into the combustion chamber 63. A mixture of fuel and air is generated in the combustion chamber 63. The mixture is ignited by the spark plug 59 and combusted. The combustion of the mixture causes the piston 62 to reciprocate up and down. Power is transmitted from the piston 62 to the crankshaft 60, causing the crankshaft 60 to rotate. When the exhaust valve 66 opens, the exhaust passage 53 and the combustion chamber 63 communicate with each other. Exhaust gas after combustion is discharged into the exhaust passage 53.

[0020] A catalyst 57 and a gas sensor 67 are provided in the exhaust passage 53. The catalyst 57 is, for example, a three-way catalyst, and removes harmful substances in the exhaust, such as carbon monoxide (CO), unburned fuel (HC), and nitrogen oxides (NOx), to purify the exhaust. The gas sensor 67 is provided downstream of the catalyst 57. The gas sensor 67 is, for example, an air-fuel ratio sensor, and outputs a current according to the air-fuel ratio. For example, when the air-fuel ratio becomes lean, the current increases, and when the air-fuel ratio becomes rich, the current decreases.

[0021] The battery ECU 34, the HVECU 40, the engine ECU 42, and the motor ECU 44 are each a control device including a calculation device such as a CPU (Central Processing Unit) and a storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0022] The motor ECU 44 controls the inverters 20 and 22, and the motors MG1 and MG2. The battery ECU 34 monitors the charging rate SOC of the battery 32, and controls the control center of the SOC, the output upper limit value of the power output by the battery 32, and the like.

[0023] The HVECU 40 is connected to the battery ECU 34, the engine ECU 42, and the motor ECU 44. The HVECU 40 controls switching between the CS mode and the CD mode. The driving mode can also be switched by, for example, the user operating a mode switch (not shown). The HVECU 40 acquires the accelerator opening detected by the accelerator opening sensor 11, and determines the required output based on the accelerator opening.

[0024] The engine ECU 42 obtains the rotation angle detected by the crank angle sensor 68, and obtains the rotation speed of the internal combustion engine 10 based on the rotation angle. The engine ECU 42 obtains the amount of air detected by the air flow meter 55. The engine ECU 42 changes the amount of air introduced into the internal combustion engine 10 by controlling the opening degree of the throttle valve 56.

[0025] The engine ECU 42 controls the amount and timing of fuel injection from the fuel injection valve 58, and controls the ignition timing of the spark plug 59. The engine ECU 42 obtains the accelerator opening from the accelerator opening sensor 11. The engine ECU 42 controls the fuel injection amount, ignition timing, etc. so as to obtain an output according to the accelerator opening.

[0026] The engine ECU 42 functions as a fuel control unit that turns on and off fuel injection from the fuel injection valve 58 based on the accelerator opening and the like. For example, when the accelerator opening becomes zero, the engine ECU 42 stops fuel injection (FC: Fuel Cut). The engine ECU 42 functions as a determination unit that performs deterioration determination (OBD: On Board Diagnosis) of the gas sensor 67.

[0027] 3 is a diagram illustrating the characteristics of the gas sensor 67. The horizontal axis represents time. The vertical axis represents the current output by the gas sensor 67. The solid line represents the characteristics when the gas sensor 67 is normal. The dashed line represents the characteristics when the gas sensor 67 is deteriorated. In FIG. 3, the air-fuel ratio changes from stoichiometry (theoretical air-fuel ratio, 14.7) to lean (a value greater than 14.7) over time.

[0028] As shown in Fig. 3, when the air-fuel ratio is stoichiometric, the current is Is. Is may be, for example, 0 amperes or a value other than 0. When the air-fuel ratio changes to the lean side, the output current of the gas sensor 67 increases. When the air-fuel ratio is 16, the gas sensor 67 outputs a current Ia. When the air-fuel ratio is 18, the gas sensor 67 outputs a current Ib.

[0029] For example, the range of air-fuel ratios for which deterioration is determined is set to be between 16 and 18. The time taken for the output current of the gas sensor 67 to change from current Ia corresponding to air-fuel ratio 16 to current Ib corresponding to air-fuel ratio 18 is measured. If this time is less than a threshold, the gas sensor 67 is determined to be normal. If the time is equal to or greater than the threshold, the gas sensor 67 is determined to be abnormal (deteriorated).

[0030] In the example of the solid line in FIG. 3, at time ta, the current is Ia. At time tb, the current is Ib. The time that elapses until the current changes from Ia to Ib is tb-ta. In the example of the dashed line, the gas sensor 67 is deteriorated, so the current increases more slowly than in the example of the solid line. At time tc, the current is Ia. At time td, the current is Ib. The time that elapses until the current changes from Ia to Ib is td-tc, which is longer than tb-ta.

[0031] The engine ECU 42 determines that the gas sensor 67 in the example shown by the solid line is normal because tb-ta is less than the threshold value. The engine ECU 42 determines that the gas sensor 67 in the example shown by the dashed line is abnormal because td-tc is equal to or greater than the threshold value.

[0032] As shown in the example of FIG. 3, when the air-fuel ratio changes from stoichiometry to lean, it is possible to determine the deterioration of the responsiveness of the gas sensor 67 based on the change time of the current corresponding to the air-fuel ratio band (for example, from 16 to 18). In addition, by evaluating the current (limit current) output by the gas sensor 67 when the air-fuel ratio is stoichiometry, it is also possible to determine the deterioration of the accuracy of the limit current (IL accuracy). The deterioration determination of the gas sensor 67 in the embodiment includes at least one of the deterioration determination of the responsiveness and the deterioration determination of the IL accuracy. The deterioration determination is started when the air-fuel ratio is stoichiometry. If the air-fuel ratio is leaner than stoichiometry, the deterioration determination is not performed.

[0033] When the supply of fuel to the internal combustion engine 10 is stopped, the air-fuel ratio becomes lean. When the supply of fuel to the internal combustion engine 10 is resumed, the air-fuel ratio approaches stoichiometry. After the air-fuel ratio becomes stoichiometry, the air-fuel ratio changes when the supply of fuel is stopped. At this time, the deterioration determination of the gas sensor 67 can be performed. On the other hand, if the fuel cut is performed before the air-fuel ratio becomes stoichiometry, that is, in a lean state, the deterioration determination of the gas sensor 67 is not performed. Also, in the hybrid vehicle 1, the internal combustion engine 10 may be stopped intermittently during deceleration, and the fuel cut may not be performed. This is because the fuel efficiency is improved by the effect of energy regeneration. By not cutting the fuel, there is a risk that the opportunities for the deterioration determination of the gas sensor 67 will decrease. In this embodiment, the opportunities for the deterioration determination of the gas sensor 67 are secured.

[0034] 4 to 6 are flow charts illustrating the processing in the embodiment. As shown in FIG. 4, the engine ECU 42 turns on a fuel cut request (FC request) to determine deterioration of the gas sensor 67 (step S10). When the user of the hybrid vehicle 1 stops depressing the accelerator pedal, the engine ECU 42 detects that the accelerator opening is zero (accelerator off, step S12). The engine ECU 42 starts a fuel cut (FC) (step S14). Fuel injection from the fuel injection valve 58 stops.

[0035] When the user depresses the accelerator pedal, the engine ECU 42 detects that the accelerator opening has increased from zero (accelerator on, step S16). The engine ECU 42 stops the FC (step S18). The engine ECU 42 turns on the start request (engine start request) for the internal combustion engine 10 (step S20). The engine ECU 42 controls the air-fuel ratio so that the air-fuel ratio of the internal combustion engine 10 becomes stoichiometric (step S22). The control of the air-fuel ratio will be described later with reference to FIG. 6. When the user stops depressing the accelerator pedal, the engine ECU 42 detects that the accelerator opening is zero (accelerator off, step S24).

[0036] As shown in FIG. 5, the engine ECU 42 determines whether or not the engine start request is ON (step S26). If the determination is negative (No), the engine ECU 42 starts FC without controlling the air-fuel ratio (step S30). If the determination is positive (Yes), the engine ECU 42 controls the air-fuel ratio (step S28). The air-fuel ratio becomes stoichiometric. After that, the engine ECU 42 starts FC (step S30).

[0037] The engine ECU 42 acquires the current output by the gas sensor 67 and measures the elapsed time T1 until the current changes in response to a change in the air-fuel ratio. For example, as shown in FIG. 3, when the air-fuel ratio changes from 16 to 18, the current changes from Ia to Ib. The elapsed time T1 is the time it takes for the current to change from Ia to Ib. The engine ECU 42 determines whether the elapsed time T1 is less than the threshold value Tth1 (step S32). If the determination is positive, the engine ECU 42 determines that the gas sensor 67 is normal (step S34). If the determination is negative, the engine ECU 42 determines that the gas sensor 67 is abnormal (step S36).

[0038] 6 shows the control of the air-fuel ratio. The engine ECU 42 acquires the air-fuel ratio λ detected by the gas sensor 67, and determines whether the air-fuel ratio λ is less than a threshold λth (step S40). The threshold λth may be, for example, the stoichiometric air-fuel ratio of 14.7, or a value close to 14.7. If the determination is negative, the engine ECU 42 continues the injection of fuel from the fuel injector 58 (step S42). After step S42, step S40 is performed again.

[0039] If the air-fuel ratio λ is less than the threshold value λth (positive determination in step S40), the engine ECU 42 measures the elapsed time T2 in the state where λ<λth, and determines whether the elapsed time T2 is equal to or greater than the threshold value Tth2 (step S44). If the determination is negative, the engine ECU 42 continues the injection of fuel from the fuel injector 58 (step S46). After step S46, step S44 is performed again. If the elapsed time T2 is equal to or greater than the threshold value Tth2 (positive determination in step S44), the engine ECU 42 turns off the engine start request (step S48). The operation of the internal combustion engine 10 stops.

[0040] After the air-fuel ratio becomes stoichiometric through the air-fuel ratio control and a time period Tth2 or more has elapsed in this state, a deterioration determination of the gas sensor 67 is performed (steps S32 to S36 in FIG. 5).

[0041] 7 is a diagram illustrating a time chart. From the top, the chart shows the accelerator opening, the RPM of the internal combustion engine 10, the fuel cut signal (FC signal), the engine start request, the air-fuel ratio, a flag indicating permission for the deterioration determination of the gas sensor 67, and a completion flag for the deterioration determination. The upper side of the air-fuel ratio is lean, and the lower side is rich.

[0042] 7, the hybrid vehicle 1 is decelerating. The accelerator opening degree repeatedly increases and decreases, and finally becomes 0 (accelerator off). The rotation speed of the internal combustion engine 10 also decreases.

[0043] At time t1, the accelerator opening is 0. The FC signal changes from off to on (from 0 to 1) and fuel cut-off is performed. At time t2, the accelerator opening increases from 0. The FC signal turns off and the engine start request turns on. Fuel cut-off stops and fuel injection resumes. The permission flag for deterioration determination of gas sensor 67 turns on at time t1 and turns off at time t2. Because the time that the permission flag for deterioration determination is on (the permitted time for OBD detection) is short, the deterioration determination is not completed.

[0044] From time t3 to t4, fuel cut is performed and the flag for permission of deterioration determination is turned on. However, since the flag for permission of deterioration determination is turned on for a short period of time, the deterioration determination is not completed.

[0045] At time t4, the accelerator opening increases beyond 0, and the FC signal turns off. The internal combustion engine 10 returns from the fuel cut to a state in which fuel injection is performed. At time t5, the accelerator opening becomes 0, but the FC signal remains off until time t6, and the engine start request remains on. That is, fuel injection continues from time t5 to t6.

[0046] During the fuel cut, the air-fuel ratio becomes lean. When fuel injection is resumed after the fuel cut is stopped at time t4, the air-fuel ratio changes from lean toward stoichiometry. In this embodiment, the FC signal is off from time t5 to t6, and fuel injection continues. Therefore, the air-fuel ratio continues to change and reaches stoichiometry. In step S40 of FIG. 6, λ<λth.

[0047] At time t6, the engine start request is turned off. The FC signal is turned on, and fuel cut is initiated. The permission flag for deterioration determination is also turned on. During FC, the air-fuel ratio changes from stoichiometry to lean. The engine ECU 42 obtains the current output by the gas sensor 67, and performs deterioration determination of the gas sensor 67 based on the current (steps S32 to S36 in FIG. 5). At time t7, the deterioration determination is completed, and the completion flag is turned on.

[0048] According to this embodiment, even during fuel cut, if the air-fuel ratio is leaner than stoichiometry, the engine ECU 42 does not perform a deterioration determination of the gas sensor 67. As shown in Fig. 7, the engine ECU 42 continues the fuel cut until the air-fuel ratio becomes stoichiometric. When the air-fuel ratio becomes stoichiometric, the engine ECU 42 performs a deterioration determination of the gas sensor 67. This ensures an opportunity to perform a deterioration determination of the gas sensor 67.

[0049] In the hybrid vehicle 1, the internal combustion engine 10 may be stopped intermittently and fuel cut may not be performed. Compared to fuel cut, intermittent stopping improves fuel economy. Compared to engine vehicles, the opportunities for fuel cut are limited, and there is a risk that the opportunities for determining deterioration of the gas sensor 67 may decrease. According to this embodiment, after fuel cut is performed, fuel cut is continued until the air-fuel ratio becomes stoichiometric, thereby ensuring the opportunities for determining deterioration of the gas sensor 67. In other words, deterioration determination can be performed in response to fuel cut. In the hybrid vehicle 1, it is possible to achieve both improvement of fuel economy and ensuring the opportunities for determining deterioration of the gas sensor 67. The embodiment may be applied to engine vehicles other than the hybrid vehicle 1.

[0050] When the fuel cut time is short, such as from time t1 to time t2 in Fig. 7, the deterioration determination of the gas sensor 67 is not completed. According to this embodiment, the deterioration determination time is secured long after the air-fuel ratio returns to stoichiometry, such as after time t6 in Fig. 7. The deterioration determination of the gas sensor 67 can be completed.

[0051] For example, the deterioration judgment of the gas sensor 67 may be performed once, and the deterioration judgment of the gas sensor 67 may be made from the time T1 at which the air-fuel ratio changes in the judgment. For example, the deterioration judgment may be performed multiple times, and the deterioration judgment may be made based on the average value of the time T1. In the process of FIG. 5, it is judged whether the responsiveness of the gas sensor 67 shown in FIG. 3 to the air-fuel ratio is normal or abnormal. The accuracy of the current of the gas sensor 67 at the stoichiometric air-fuel ratio (IL accuracy) may be judged. Fuel injection is continued, and the output current of the gas sensor 67 when the air-fuel ratio becomes stoichiometric is measured, and the judgment is made based on the value of the current.

[0052] The threshold value λth for the air-fuel ratio λ may be, for example, the theoretical air-fuel ratio of 14.7, or may be a value close to 14.7. It is sufficient that the air-fuel ratio λ becomes less than the threshold value λth (richer than λth) to know that the air-fuel ratio becomes stoichiometric from lean. The deterioration determination of the gas sensor 67 may be started in response to the air-fuel ratio λ becoming less than the threshold value λth without comparing the elapsed time T2 in the state in which the air-fuel ratio λ becomes less than the threshold value λth with the threshold value Tth2. In the example of FIG. 6, the deterioration determination of the gas sensor 67 is performed in response to the elapsed time T2 in the state in which the air-fuel ratio λ becomes less than the threshold value λth continuing for more than the threshold value Tth2. The deterioration determination of the gas sensor 67 can be performed in a state in which the air-fuel ratio λ maintains stoichiometry. The accuracy of the deterioration determination is improved.

[0053] Although a preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0054] 1 Hybrid vehicles 1a Drive wheel 10 Internal combustion engine 11 Accelerator opening sensor 12 Damper 14 Planetary Gear 16 Differential gear 20, 22 Inverter 24 Charger 26 Power plug 32 Battery 34 Battery ECU 40 HVECU 42 Engine ECU 44 Motor ECU 50 Cylinder block 51 Cylinder head 52 Intake passage 53 Exhaust passage 54 Air cleaner 55 Air flow meter 56 Throttle valve 57 Catalyst 58 Fuel Injection Valve 59 Spark plug 60 Crankshaft 61 Connecting rod 62 Piston 63 Combustion chamber 64 Intake valve 66 Exhaust valve 67 Gas Sensor 68 Crank Angle Sensor MG1, MG2 motors

Claims

[Claim 1] A deterioration determination device for determining deterioration of a gas sensor provided in an exhaust passage of an internal combustion engine, comprising: A fuel control unit that controls the supply of fuel to the internal combustion engine; a determination unit that determines whether the gas sensor has deteriorated while the supply of fuel to the internal combustion engine is stopped, When the air-fuel ratio detected by the gas sensor is leaner than a predetermined value, the determination unit does not perform the determination, When the air-fuel ratio detected by the gas sensor is richer than the predetermined value and the fuel control unit supplies the fuel, the determination unit does not perform the determination, When the fuel control unit stops the supply of the fuel and the air-fuel ratio detected by the gas sensor is on the rich side of the predetermined value, the determination unit performs the determination, During the stop of the supply of fuel, the determination unit continues the determination until the determination is completed, A deterioration determining device for a gas sensor, wherein when the fuel control unit resumes the supply of fuel after the supply of fuel has been stopped and before the determination is completed, the determining unit suspends the determination.

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