JP6003867B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device that executes stop and return of fuel injection to an internal combustion engine based on a required torque for the internal combustion engine.

  2. Description of the Related Art Conventionally, an engine control device that performs torque control that realizes a required torque for an internal combustion engine by adjusting an intake air amount taken into the internal combustion engine and an ignition timing in the internal combustion engine is known.

  In such an engine control device, for example, when the vehicle travels on a downhill, a cut determination torque that is a threshold value for determining whether or not to execute a fuel cut to stop fuel injection to the internal combustion engine. When the required torque decreases, the fuel cut is executed (for example, see Patent Document 1).

  When determining whether to return the fuel injection from the fuel cut state, it is desirable to set a return determination torque larger than the cut determination torque as a threshold. In a state where the required torque is lower than the cut determination torque and the fuel cut is executed, even if the required torque rises above the cut determination torque, fuel injection to the internal combustion engine does not return, and the required torque rises above the return determination torque Then, fuel injection returns.

JP 2010-174650 A

  The actual torque generated by the internal combustion engine when the required torque rises above the return determination torque and the fuel injection returns is the combustion limit torque at the combustion limit by the internal combustion engine. Naturally, the torque at the time of fuel cut when the fuel injection is cut is smaller than the combustion limit torque. The internal combustion engine cannot generate a torque between the combustion limit torque and the fuel cut time torque.

  When the required torque is lower than the cut determination torque and the fuel injection is cut, the actual torque is reduced to the fuel cut torque. When the engine speed decreases due to this torque decrease, the required torque increases to increase the engine speed and keep it constant.

  When the required torque rises above the return determination torque and the fuel injection returns, the actual torque increases from the fuel cut time torque to the combustion limit torque. When the engine speed increases due to this torque increase, the required torque decreases in an attempt to maintain the engine speed at a constant level.

  As described above, when the actual torque changes due to the change in the required torque, the fuel injection is repeatedly stopped and returned, so that the engine speed changes. If both the cut determination torque and the return determination torque are constant, the engine speed fluctuates in the same manner as time elapses, so that the fluctuation amount of the engine speed cannot be reduced.

  The present invention has been made to solve the above-described problem, and when executing stop and return of fuel injection to the internal combustion engine based on the required torque, while reducing the fluctuation amount of the engine speed, An object of the present invention is to provide an engine control device that suppresses a temperature rise of an exhaust purification catalyst.

  The inventor of the present application executes the fuel cut next even if the required torque rises above the return determination torque and the fuel injection returns by reducing the cut determination torque once the required torque falls below the cut determination torque. We examined the technology to make it difficult to do. By making it difficult to execute the fuel cut, the fluctuation of the actual torque is suppressed and the fluctuation amount of the engine speed is reduced.

  However, if the cut determination torque is lowered to make it difficult to execute the fuel cut, the fuel cut is not executed and the fuel combustion is continued, so that the time during which the actual torque is held at the combustion limit torque becomes longer. Usually, the combustion limit torque is a lower limit value at which the internal combustion engine can burn fuel by generating a torque by retarding the ignition timing.

  If the ignition timing is retarded, the exhaust temperature rises. Therefore, if the actual torque is maintained at the combustion limit torque and the ignition timing is retarded, the catalyst temperature rises due to the exhaust temperature rise, and the catalyst deteriorates. There is a fear.

Therefore, according to the engine control apparatus of the present invention, it includes a cut determination means, a return determination means, a torque control means, and a threshold setting means.
The cut determination means compares the required torque required for the internal combustion engine with the cut determination torque for determining whether or not to execute the fuel cut for stopping the fuel injection to the internal combustion engine, and the return determination means In order to determine whether to return the fuel injection from the fuel cut state to the internal combustion engine, a comparison is made between the return determination torque set to a value larger than the cut determination torque.

The torque control unit controls the output torque of the internal combustion engine based on the comparison result by the cut determination unit and the comparison result by the return determination unit. Upper threshold value setting means, at least cut judging torque of cut determination torque and return judgment torque, based on the catalyst temperature of the exhaust gas purification catalyst of an internal combustion engine, the catalyst temperature decreases so please low, the catalyst temperature increases Raise it.

  First, in a state where the catalyst temperature does not change and the cut determination torque is not changed, when the required torque is lower than the cut determination torque and the fuel injection is stopped, the actual torque is smaller than the required torque when the fuel injection is stopped. The engine speed decreases because the engine speed decreases. When the required torque is increased to increase the engine speed and is higher than the return determination torque, the fuel injection is recovered and the actual torque increases to the combustion limit torque, so the engine speed increases.

  If the actual torque rises to the combustion limit torque and the catalyst temperature rises by retarding the ignition timing, the present invention increases the cut determination torque, so the engine speed is lower than when the cut determination torque is not increased. Therefore, the fuel cut can be executed at an early timing when the required torque decreases. As a result, the period during which the ignition timing is retarded and the actual torque is held at the combustion limit torque can be shortened as much as possible, so that an increase in the catalyst temperature can be suppressed.

  Furthermore, since the fuel cut can be executed at an early timing when the required torque decreases in order to decrease the engine speed, the increase in the engine speed is suppressed earlier than when the cut determination torque is not increased. Thereby, the fluctuation amount of engine speed can be reduced. Since it is not necessary to perform fuel cut early when the catalyst temperature decreases, the cut determination torque is decreased.

The block diagram which shows the engine control system by this embodiment. The flowchart which shows the torque control process of this embodiment. The flowchart which shows the determination torque setting process 1 of this embodiment. The characteristic view which shows the relationship between catalyst temperature and a torque rate. The time chart which shows the determination torque setting process 1 of this embodiment. The flowchart which shows the determination torque setting process 2 of this embodiment. The time chart which shows the determination torque setting process 2 of this embodiment. The flowchart which shows the determination torque setting process 3 of this embodiment. The time chart which shows the determination torque setting process 3 of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An engine control system 2 shown in FIG. 1 is a system that controls the operation of a gasoline internal combustion engine (hereinafter also referred to as “engine”) 10 that ignites an air-fuel mixture sucked into a cylinder with a spark plug 22.

  An air cleaner (not shown) is installed upstream of the intake pipe 100 of the engine 10. An air flow meter 12, a throttle device 14, an intake pressure sensor 18, and an injector 20 are installed from the air cleaner toward the engine 10 on the downstream side of the intake flow. Has been.

  The air flow meter 12 detects the amount of intake air flowing through the intake pipe 100. The throttle device 14 adjusts the amount of intake air taken into the engine 10 from the intake pipe 100 by controlling the throttle opening degree by the motor 15. The throttle device 14 is provided with a throttle opening sensor 16 for detecting the throttle opening.

  An intake pressure sensor 18 for detecting intake pressure is installed in the surge tank 102 on the downstream side of the throttle device 14. An injector 20 for injecting fuel is installed in the vicinity of an intake port of an intake manifold 104 that introduces air from the surge tank 102 to each cylinder of the engine 10.

  A spark plug 22 is installed in the cylinder head of the engine 10 for each cylinder. The air-fuel mixture in the cylinder is ignited by spark discharge of the spark plug 22. The cylinder block of the engine 10 is provided with a water temperature sensor 24 that detects the cooling water temperature and a rotation speed sensor (crank angle sensor) 26 that detects the engine rotation speed.

The A / F sensor 28 and the exhaust purification catalyst 30 are installed in the exhaust pipe 110 of the engine 10. The exhaust purification catalyst 30 is a three-way catalyst that purifies CO, HC, and NOx in the exhaust.
Outputs from various sensors including the air flow meter 12, the throttle opening sensor 16, the intake pressure sensor 18, the water temperature sensor 24, the rotation speed sensor 26, the A / F sensor 28, and an accelerator sensor (not shown) are electronic control units (ECU: Electronic Control Unit) 40.

  The ECU 40 is mainly configured by a microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like. The ECU 40 implements various engine controls such as a throttle opening control for the throttle device 14, an injection control for the injector 20, and an ignition control for the spark plug 22 by the CPU executing a control program stored in the ROM.

(Torque control)
The ECU 40 controls the throttle opening of the throttle device 14 based on the required torque required as the output torque of the engine 10 to adjust the amount of intake air drawn into the engine 10 and adjust the ignition timing of the spark plug 22. To do. When the throttle opening is increased and the intake amount is increased, the output torque is increased. When the throttle opening is decreased and the intake amount is decreased, the output torque is decreased. Further, when the ignition timing is advanced, the output torque increases, and when the ignition timing is retarded, the output torque decreases.

  In addition to the driving torque required for vehicle travel set based on the accelerator opening and the engine speed, the ECU 40 is required for torque required by an external load caused by ON / OFF of an auxiliary device such as an air conditioner, shift change, etc. Is obtained from another ECU as a required torque for the engine 10.

  In the present embodiment, for example, when the required torque is increased due to a drive request for an auxiliary machine or a shift change and an external load is applied to the engine 10, before the output torque is increased in accordance with the increase in the required torque, Torque control is executed to retard the ignition timing in advance in order to temporarily secure reserve torque by increasing the intake air amount and to reduce output torque that increases by securing the reserve torque.

  If the ignition timing is advanced in a state where the reserve torque is secured, the output torque can be increased rapidly even if the required torque suddenly increases according to the driving of auxiliary equipment or the execution of shift changes. Since the output torque is insufficient with respect to the increase in the engine speed, the engine speed can be prevented from decreasing.

  In normal torque control, since the ignition timing is set to MBT (Minimum Advance for Best Torque) so that the fuel efficiency is optimized, the intake air amount is set to a value that realizes the required torque in MBT.

(Fuel cut)
The combustion limit torque is a lower limit value at which the ignition timing can be retarded so that the engine 10 can burn fuel and generate torque. The combustion limit air torque is a torque obtained by adding a reserve torque corresponding to the retard of the ignition timing to the combustion limit torque, and is determined by the intake air amount. Therefore, the combustion limit air torque is larger than the combustion limit torque.

  When the required torque for the engine 10 decreases and falls below the combustion limit torque, a fuel cut for stopping fuel injection is executed. The cut determination torque to be compared with the required torque when executing the fuel cut is set to a value lower than the combustion limit torque.

  The return determination torque to be compared with the required torque when the fuel injection is returned from the fuel cut state in which the fuel injection is stopped is set to a value that is larger than the cut determination torque and smaller than the combustion limit torque.

(Torque control processing)
Next, the main routine of the torque control process executed by the ECU 40 based on the control program stored in the ROM will be described based on the flowchart shown in FIG. The flowchart of FIG. 2 is executed at predetermined time intervals. “S” in the flowchart represents a step.

  The ECU 40 calculates the catalyst temperature of the exhaust purification catalyst 30 from a map or the like based on the engine speed, the intake air amount, the ignition timing, the air-fuel ratio detected by the A / F sensor 28, etc. (S400). Based on the amount, the catalyst temperature, the water temperature, etc., the ignition delay limit, the combustion limit air torque, and the combustion limit torque are calculated from a map or the like (S402).

  In this embodiment, as shown in FIG. 5, the combustion limit torque is increased when the catalyst temperature is increased, and the combustion limit torque is decreased when the catalyst temperature is decreased. On the other hand, the combustion limit torque may be constant regardless of the catalyst temperature.

  The ECU 40 calculates a required torque for the engine 10 from a map or the like based on the engine speed, the accelerator opening, and the like (S404), a cut determination torque for determining whether or not to stop the fuel injection, a fuel injection A return determination torque for determining whether or not to return is set (S406). Details of S406 will be described later.

In S408, the ECU 40 determines whether the required torque calculated in S404 is smaller than the cut determination torque set in S406.
When the required torque is smaller than the cut determination torque (S408: Yes), the ECU 40 turns on the fuel cut request flag (S410) and ends this process.

  When the required torque is equal to or greater than the cut determination torque (S408: No), the ECU 40 determines whether the required torque is larger than the return determination torque set in S406 (S412). When the required torque is equal to or less than the return determination torque (S412: No), the ECU 40 ends this process.

If the requested torque is greater than the return determination torque (S412: Yes), the ECU 40 turns off the fuel cut request flag (S414) and ends this process.
(Determination torque setting process 1)
The cut determination torque and return determination torque setting processing set in S406 in FIG. 2 will be described based on the flowchart shown in FIG.

  In S420, the ECU 40 calculates the torque rates of the cut determination torque and the return determination torque from a map or the like representing the characteristics shown in FIG. 4 based on the catalyst temperature calculated in S400 of FIG.

  In the present embodiment, the torque rate is the relative position of the cut determination torque and the return determination torque from the fuel cut time torque as a ratio when the difference between the combustion limit torque and the fuel cut time torque is 100%. It is. Therefore, the torque rate of the fuel cut torque is 0%, and the torque rate of the combustion limit torque is 100%.

  As shown in FIG. 4, the torque rate 200 of the cut determination torque and the torque rate 202 of the return determination torque increase as the catalyst temperature rises, and the torque rate 202 is larger than the torque rate 200.

  When the torque rates of the cut determination torque and the return determination torque are set based on the catalyst temperature, the ECU 40 calculates the cut determination torque and the return determination torque from the following equations (1) and (2) (S422).

Cut judgment torque = (combustion limit torque−fuel cut torque) × cut judgment torque torque ratio + fuel cut torque (1)
Return determination torque = (combustion limit torque−fuel cut torque) × return determination torque torque ratio + fuel cut torque (2)
Thus, by calculating the cut determination torque and the return determination torque in accordance with the catalyst temperature, the cut determination torque and the return determination torque change as shown in FIG. In this embodiment, the cut determination torque when the catalyst temperature is low is reduced so as to be as close as possible to the fuel cut torque.

  When the vehicle travels on the downhill and the required torque decreases during the period T1 in FIG. 5 and falls below the cut determination torque, the fuel cut request flag is turned on during the period T2, and fuel injection to the engine 10 stops. Is done. Then, the actual torque generated by the engine 10 is lower than the required torque and is reduced to the torque at the time of fuel cut.

  When the actual torque decreases to the fuel cut time torque, the engine speed decreases, so the ECU 40 increases the required torque. When the required torque rises above the return determination torque, the fuel cut request flag is turned off in period T3, and fuel injection to the engine 10 is restored. Then, the actual torque generated by the engine 10 increases from the required torque to the combustion limit torque.

  When fuel injection returns, the ignition timing is retarded and the actual torque rises to the combustion limit torque. When the ignition timing is retarded, the exhaust temperature rises, so the catalyst temperature of the exhaust purification catalyst 30 rises gradually. When the catalyst temperature increases, the cut determination torque and the return determination torque increase.

  When the fuel injection is restored and the actual torque increases to the combustion limit torque, the engine speed increases. The ECU 40 reduces the required torque in order to reduce the actual torque and suppress the increase in the engine speed.

  Even if the required torque decreases, the fuel injection continues until the required torque decreases below the cut determination torque, so the engine speed increases. However, when the engine speed approaches the upper limit value reached when the actual torque is the combustion limit torque, the engine speed gradually increases.

  Since the cut determination torque is increased as the catalyst temperature increases, the required torque is lower than the cut determination torque at an earlier timing than when the cut determination torque is not increased. Thereby, fuel injection is stopped at an early timing, and the actual torque is reduced to the torque at the time of fuel cut. As a result, the engine speed decreases in the period T4. Since the fuel injection is stopped at an early timing when the catalyst temperature is rising, the increase in the catalyst temperature can be suppressed.

  The actual torque is reduced to the torque at the time of fuel cut by the fuel cut, and the retard control of the ignition timing is stopped. Therefore, the catalyst temperature is lowered as the exhaust temperature is lowered. As the catalyst temperature decreases, the ECU 40 decreases the cut determination torque and the return determination torque.

When the actual torque decreases to the fuel cut time torque and the engine speed decreases, the ECU 40 increases the required torque in the period T4.
Since the cut determination torque and the return determination torque are reduced as the catalyst temperature decreases, the required torque rises earlier than the return determination torque compared to when the return determination torque is not reduced. As a result, since the fuel injection is restored, the actual torque increases to the combustion limit torque. As a result, the engine speed increases at an earlier timing than when the return determination torque is not reduced.

  As described above, when the engine speed is increased, the engine speed is reduced at an early timing, and when the engine speed is decreased, the engine speed is increased at an early timing.

  In the present embodiment, the cut determination torque when the catalyst temperature is low is reduced as much as possible to increase the difference between the cut determination torque and the return determination torque. As a result, even if the cut determination torque increases as the catalyst temperature increases, the time required for the required torque to decrease from the fuel injection return state to decrease below the cut determination torque becomes longer. As a result, it is possible to reduce as much as possible the frequency with which the fuel injection is repeatedly stopped and returned while reducing the fluctuation amount of the engine speed.

(Determination torque setting process 2)
FIG. 6 shows another determination torque setting process. In S430, the ECU 40 calculates a torque rate (also referred to as a basic torque rate) of the basic torque of the cut determination torque and the return determination torque from a map based on the engine speed. The basic torque is a torque that serves as a reference for the offset when the cut determination torque and the return determination torque are set by an offset, which will be described later, set based on the catalyst temperature.

  The basic torque ratio is the relative position of the basic torque of the cut determination torque and the return determination torque from the fuel cut time torque as a ratio when the difference between the combustion limit torque and the fuel cut time torque is 100%. is there. The basic torque rate may be a constant value regardless of the engine speed.

  The basic torque (also referred to as basic cut determination torque) of the cut determination torque calculated from the basic torque rate in the determination torque setting process 2 is the cut determination set in the determination torque setting process 1 described above regardless of the engine speed. A value larger than the minimum value of torque is set.

  Next, the ECU 40 determines whether there is an acceleration request (S432). The acceleration request is generated by an acceleration operation by a driver, such as depression of an accelerator pedal, and acceleration determination by vehicle travel control in cruise control or the like.

  If there is an acceleration request (S432: Yes), the ECU 40 turns off the fuel cut execution flag to return the cut determination torque and the return determination torque to the basic torque (S434), and the process proceeds to S440.

  When there is no acceleration request (S432: No), the ECU 40 determines whether or not the fuel cut request flag is on when executing this routine (S436). If the fuel cut request flag is on when this routine is executed, the fuel cut is executed during the previous processing of this routine. If the fuel cut request flag is off, the fuel cut is executed during the previous processing of this routine. Indicates that it has not been executed.

  If the fuel cut request flag is off (S436: No), the ECU 40 proceeds to S440. If the fuel cut request flag is on (S436: Yes), the ECU 40 turns on the fuel cut execution flag (S438), and the process proceeds to S440.

  In S440, the ECU 40 determines whether or not the fuel cut execution flag is on. When the fuel cut execution flag is on (S440: Yes), the ECU 40 calculates the offset rate for each basic torque rate from the map or the like based on the catalyst temperature for the cut determination torque and the return determination torque (S442), and S446. The process is transferred to.

  As shown in FIG. 7, the offset rate for each basic torque ratio calculated for the cut determination torque and the return determination torque is increased when the catalyst temperature rises, and the cut determination torque and the return determination torque increase when the catalyst temperature decreases. The map is set so that the determination torque and the return determination torque are reduced.

  Furthermore, the offset rate for each basic torque rate calculated for the cut determination torque and the return determination torque is set to a negative value so as to be smaller than the basic cut determination torque in the case of the cut determination torque, In the case of the return determination torque, it is set to a positive value so as to be larger than the basic return determination torque.

  When the fuel cut execution flag is off (S440: No), the ECU 40 sets the offset rate for each basic torque rate to 0 for the cut determination torque and the return determination torque (S444), and the process proceeds to S446.

In S446, the ECU 40 calculates the torque rate of the cut determination torque and the torque rate of the return determination torque from the following equations (3) and (4), respectively.
Torque rate of cut judgment torque = Basic torque rate of cut judgment torque + Offset rate of cut judgment torque (3)
Torque rate of return determination torque = basic torque rate of return determination torque + offset rate of return determination torque (4)
In S448, the ECU 40 uses the torque rate of the cut determination torque and the torque rate of the return determination torque calculated in S446 to calculate the cut determination torque and the return determination torque from the above-described equations (1) and (2).

  If the offset rate is set to 0 in S444, the cut determination torque and the return determination torque calculated in S448 are the basic cut determination torque and the basic return determination torque calculated from the basic torque rate, respectively.

  If the fuel cut execution flag is set to ON in S438, the fuel cut execution flag is not set to OFF until an acceleration request is generated. Accordingly, once the fuel cut is executed, the cut determination torque and the return determination torque offset according to the catalyst temperature from the reference cut determination torque and the reference return determination torque are set until an acceleration request is generated.

  In the determination torque setting process 2, the basic cut determination torque is set to a value larger than the cut determination torque set in the determination torque setting process 1 regardless of the engine speed. Therefore, the timing at which the fuel cut is first executed is earlier than the determination torque setting process 1. Thereby, fuel consumption can be improved.

  Once the fuel cut is executed, the cut determination torque and the return determination torque are offset with respect to the basic cut determination torque and the basic return determination torque until an acceleration request is generated, and the difference between the return determination torque and the cut determination torque is calculated. , It is expanded to the same extent as in the determination torque setting process 1. Further, when the catalyst temperature increases, the cut determination torque and the return determination torque are increased, and when the catalyst temperature decreases, the cut determination torque and the return determination torque are decreased.

  Thus, once the fuel cut is executed, as in the determination torque setting process 1, the increase in the catalyst temperature is suppressed and the fluctuation amount of the engine speed is reduced, while the frequency at which the fuel injection is stopped and returned is repeated. It can be reduced as much as possible.

(Determination torque setting process 3)
FIG. 8 shows another determination torque setting process. S450 to S460 and S464 to S468 in FIG. 8 are substantially the same processes as S430 to S440 and S444 to S448 in FIG.

  That is, once the fuel cut is executed, the determination torque setting process is performed in that the basic cut determination torque and the basic return determination torque are offset according to the catalyst temperature to set the cut determination torque and the return determination torque until an acceleration request is generated. 3 and determination torque setting processing 2 are the same. The process for setting the offset rate is different between S462 in the determination torque setting process 3 and S442 in the determination torque setting process 2.

  In the determination torque setting process 3, when the fuel cut execution flag is on (S460: Yes), the ECU 40 sets the offset rate for each basic torque ratio, the catalyst temperature, and the fuel injection for the cut determination torque and the return determination torque. Set based on the elapsed time from return and stop.

  Specifically, as shown in FIG. 9, when the required torque is lower than the cut determination torque and the fuel cut is executed, the basic cut determination torque and the basic return determination torque are offset according to the catalyst temperature to perform the cut determination. The torque and the return determination torque are set, and the return determination torque is further increased for the first predetermined period after the fuel cut is executed.

  On the other hand, when the required torque rises above the return determination torque and fuel injection returns, the basic cut determination torque and the basic return determination torque are offset according to the catalyst temperature to set the cut determination torque and the return determination torque. Regarding the torque, the cut determination torque is further reduced for a second predetermined period after the fuel injection is restored.

  As a result, even if the required torque suddenly increases when the fuel injection is stopped, the return determination torque is increased for the first predetermined period, so that it is prevented from returning immediately after the fuel injection stops. . Further, even if the required torque rapidly decreases when the fuel injection is restored, the cut determination torque is reduced for the second predetermined period, so that it is prevented from stopping immediately after the fuel injection is restored.

As a result, the frequency with which fuel injection is repeatedly stopped and returned and the frequency with which the engine speed fluctuates can be minimized.
[Other Embodiments]
In the above embodiment, the cut determination torque and the return determination torque are set based on the torque rate that changes according to the catalyst temperature. On the other hand, the cut determination torque and the return determination torque that change according to the catalyst temperature may be directly calculated and set as a torque value from a map, a mathematical expression, or the like.

  In addition, when setting the return determination torque based on the catalyst temperature in S406 of FIG. 2, it may be calculated by adding a predetermined offset to the cut determination torque, instead of setting it independently of the cut determination torque. . Thereby, the setting process of the return determination torque is facilitated.

  Furthermore, since the difference between the return determination torque and the cut determination torque can be reliably ensured, the difference between the return determination torque and the cut determination torque is reduced by the catalyst temperature, and the frequency at which fuel injection is stopped and returned is increased. Can be suppressed.

Alternatively, only the cut determination torque may be changed based on the catalyst temperature, and the return determination torque may be a constant value.
As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

10: Engine (internal combustion engine), 40: ECU (engine control device, cut determination means, return determination means, torque control means, threshold setting means)

Claims (7)

A cut determination means (S408) for comparing a required torque required for the internal combustion engine (10) and a cut determination torque for determining whether or not to execute a fuel cut for stopping fuel injection to the internal combustion engine;
A return determination means (S412) which is set higher than the cut determination torque and compares the required torque with a return determination torque for determining whether or not to return the fuel injection to the internal combustion engine from a fuel cut state; ,
Torque control means (S410, S414) for controlling the output torque of the internal combustion engine based on the comparison result by the cut determination means and the comparison result by the return determination means;
At least the cut judging torque of the cut judging torque and the return judgment torque, on the basis of the catalyst temperature of the internal combustion engine of the exhaust purification catalyst (30) causes a low Do When the catalyst temperature drops, the catalyst temperature threshold setting means for raising the upper with increasing (S406, S420, S422, S430~S448 , S450~S468) and,
An engine control device (40) comprising: The threshold setting means includes a combustion limit torque of the internal combustion engine and a torque at the time of fuel cut that is the output torque when the fuel cut is executed for at least the cut determination torque of the cut determination torque and the return determination torque. Is set based on the catalyst temperature, and the catalyst temperature decreases at least the cut determination torque of the cut determination torque and the return determination torque based on the torque ratio. preparative low Do not, the engine control apparatus according to claim 1, wherein the catalyst temperature is equal to or to Noboru Ue the raised. The threshold value setting means (S430 to S448, S450 to S468) cuts the basic cut determination torque set regardless of the catalyst temperature in the off state where the fuel cut has not yet been executed. As the determination torque, when the required torque is lower than the basic cut determination torque and the fuel cut is performed and turned on, it is reduced from the basic cut determination torque by an offset set based on the catalyst temperature. Set the cut judgment torque,
When the threshold value setting means sets the return determination torque based on the catalyst temperature, the basic return determination torque set regardless of the catalyst temperature in the off state is set as the return determination torque, and the on state The return determination torque is set higher than the basic return determination torque by an offset set based on the catalyst temperature.
The engine control apparatus according to claim 1 or 2, wherein The threshold value setting means (S434, S438, S454, S458) is in the on state when the fuel cut is executed once in the off state, and in the off state when an acceleration request is generated in the on state. The engine control device according to claim 3 . The engine control apparatus according to claim 4 , wherein the acceleration request is generated when an accelerator operation is performed. 6. The engine control apparatus according to claim 4, wherein the acceleration request is generated by a request from vehicle travel control.   The threshold setting means, when setting the return determination torque based on the catalyst temperature, sets the return determination torque by adding a predetermined offset to the cut determination torque. The engine control device described in 1.

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