JP4232579B2 - Control device for internal combustion engine for vehicle - Google Patents

Description

  The present invention relates to a control apparatus for an internal combustion engine for a vehicle that includes an exhaust purification catalyst and has a function of cutting fuel supply under a predetermined condition.

In order to purify the exhaust of an internal combustion engine (hereinafter also referred to as an engine), an exhaust purification catalyst (hereinafter simply referred to as a catalyst) is provided in the exhaust system of the engine.
The heat resistant temperature of such a catalyst is generally lower in an oxidizing atmosphere (A / F lean) than in a reducing atmosphere (ie, air / fuel ratio A / F rich). Therefore, the catalyst is more susceptible to thermal degradation at higher temperatures and in an oxidizing atmosphere (A / F lean). For example, when the fuel cut control at the time of deceleration in which fuel supply is stopped at the time of deceleration (so-called fuel cut) is performed, the air-fuel ratio A / F becomes significantly lean, and thus the catalyst is likely to be thermally deteriorated.

For this reason, in order to suppress catalyst thermal deterioration, it is necessary to prevent the catalyst from becoming high temperature and lean.
Therefore, the catalyst temperature is detected by a catalyst temperature sensor and the fuel cut during deceleration is prohibited when the catalyst temperature is high (Patent Document 1), or the catalyst temperature is estimated from the intake air flow rate, and the deceleration is performed when the catalyst temperature is high. Technology that prohibits fuel cuts has been proposed.

Alternatively, a technique for prohibiting fuel cut during deceleration based on the engine speed and engine load (Patent Document 2), or a technique for controlling the air-fuel ratio to the rich side for a predetermined period when fuel cut during deceleration is prohibited (patent 2) Reference 3) has also been proposed.
JP 55-137339 A JP-A-8-144814 JP-A-7-103031

By the way, as described above, in the operation region where the thermal deterioration suppression control of the catalyst is performed, even when the air-fuel ratio A / F is operated with stoichiometry, there is residual oxygen in the exhaust gas, which has adhered to the catalyst on the catalyst. The unburned material oxidizes and the catalyst temperature rises. Therefore, it is necessary to make the catalyst a reducing atmosphere (air-fuel ratio A / F rich).
Further, if the fuel cut is prohibited, the engine torque due to combustion increases as compared with the time of the fuel cut, and therefore, in the case of a vehicle engine, the driving feeling is deteriorated, for example, the feeling of deceleration is insufficient.

  Further, if the fuel cut prohibition cancellation condition for the thermal deterioration suppression control is only the fuel cut cancellation condition, that is, if the fuel cut prohibition is a logic that continues until the fuel cut cancellation condition is satisfied, the fuel cut prohibition (heat In the degradation suppression control), the engine speed increases due to the increase in engine torque due to combustion, does not decrease to the fuel cut cancellation (fuel supply return) speed, and does not satisfy the fuel cut cancellation condition. (Fuel cut prohibition) may not be canceled. Therefore, another measure is necessary to cancel the prohibition of fuel cut for thermal deterioration suppression control.

  The present invention was devised in view of the above-mentioned problems, so that the fuel cut does not cause thermal deterioration of the exhaust purification catalyst and does not cause deterioration of the driving feeling that is likely to occur at this time. An object of the present invention is to provide a control device for an internal combustion engine for a vehicle.

For this reason, the control device for an internal combustion engine for a vehicle according to the first aspect of the present invention includes an exhaust purification catalyst and performs fuel cut for stopping fuel supply when a preset fuel cut condition is satisfied. A control apparatus for an internal combustion engine for a vehicle provided with a fuel cut control means, wherein the temperature of the catalyst or a parameter value corresponding to the temperature is detected, and a fuel cut condition is satisfied. If the temperature detected by the catalyst temperature detecting means or the value of the parameter exceeds a preset catalyst upper limit temperature, the fuel cut prohibiting means for prohibiting the fuel cut and the fuel cut prohibiting means A fuel cut prohibition canceling means for canceling the fuel cut prohibition when a preset fuel cut prohibition canceling condition is satisfied during the fuel cut prohibition control. Cut prohibition releasing means, the target to the rotational speed predetermined rotational speed higher than the actual rotation speed of the fuel cut prohibiting means the internal combustion engine at the start of the fuel cut prohibition by the initial target rotational speed, it decreases as time passes set the rotational speed, the rate of decrease of the target speed in response to the transmission gear of the transmission connected to the internal combustion engine, than towards the case the speed change gear stage of the high speed stage is low speed stage A target rotational speed setting means that is set low , and a determination means that compares the actual rotational speed of the internal combustion engine with the target rotational speed corresponding to the transmission gear stage and determines cancellation of fuel cut prohibition from the comparison result. It is characterized by having.

  The fuel cut prohibition canceling means includes target rotational speed setting means for setting a target rotational speed of the internal combustion engine based on an actual vehicle speed when a transmission connected to the internal combustion engine is in a neutral state; It is preferable to include a determination unit that compares the actual rotational speed with the target rotational speed and determines cancellation of fuel cut prohibition based on the comparison result. Furthermore, it is preferable that the target rotational speed is set in terms of conversion when the shift speed is the second speed.

Alternatively, the fuel cut prohibition release means performs the setting of the target rotational speed by the target rotational speed setting means and the determination by the determination means when the transmission connected to the internal combustion engine is in a power transmission state. It is preferable that the target rotational speed setting means sets the target rotational speed in accordance with the selected transmission gear stage . Also, it is preferable that the shift stage is set in terms of the case of the second speed.

  Alternatively, the fuel cut prohibition canceling means corresponds to the actual rotational speed of the internal combustion engine on the assumption that the transmission is connected to a predetermined gear position when the transmission connected to the internal combustion engine is in a neutral state. The engine speed corresponding vehicle speed estimating means for estimating the vehicle speed, and the vehicle speed estimated by the engine speed corresponding vehicle speed estimating means by comparing the actual vehicle speed of the vehicle and determining whether to cancel the fuel cut prohibition from the comparison result And means.

  According to a sixth aspect of the present invention, there is provided a control apparatus for an internal combustion engine for a vehicle according to the present invention, which includes an exhaust purification catalyst and performs fuel cut for stopping fuel supply when a preset fuel cut condition is satisfied. A control apparatus for an internal combustion engine for a vehicle having a cut control means, wherein the temperature of the catalyst or a parameter value corresponding to the temperature is detected, and the fuel cut condition is satisfied When the temperature detected by the catalyst temperature detecting means or the value of the parameter exceeds a preset catalyst upper limit temperature, the fuel cut prohibiting means for prohibiting the fuel cut and the fuel cut prohibiting means And air-fuel ratio control means for controlling the air-fuel ratio to be richer than the stoichiometric air-fuel ratio when cutting is prohibited. Thereby, the thermal deterioration of the exhaust purification catalyst can be reliably suppressed.

  In the case where the fuel cut is prohibited by the fuel cut prohibiting means, it is preferable that an ignition timing control means for retarding the ignition timing of the internal combustion engine is provided. As a result, it is possible to suppress the occurrence of excessive engine torque that is more likely to occur when fuel cut is prohibited than when fuel cut.

According to the control apparatus for an internal combustion engine for a vehicle of the first aspect of the present invention, even when the fuel cut condition is satisfied, the fuel cut is prohibited when the exhaust purification catalyst becomes high temperature. Thermal degradation of the exhaust gas purification catalyst is suppressed, durability of the exhaust gas purification catalyst can be improved, and it can contribute to reduction of exhaust gas purification and maintenance costs. In addition, since the fuel cut prohibition is canceled when a preset fuel cut prohibition cancel condition is satisfied, the fuel cut prohibition can be appropriately canceled, and the fuel cut prohibition is enabled. It is possible to solve the problem that the state is continued unnecessarily.
Furthermore, when decelerating, the fuel cut prohibition is canceled as necessary by determining whether to cancel the fuel cut prohibition according to the selected gear position of the transmission, and smooth control is performed. Therefore, it is possible to perform highly accurate control that achieves both fuel efficiency improvement, which is the original purpose of fuel cut control, and catalyst thermal deterioration prevention control.

Further, when fuel cut is prohibited by the fuel cut prohibition means, the thermal deterioration of the exhaust purification catalyst is promoted by residual oxygen by controlling the air / fuel ratio to be richer than the stoichiometric air / fuel ratio. Problems can be avoided and thermal deterioration of the exhaust purification catalyst can be reliably suppressed.
The fuel cut prohibition canceling means sets the target rotational speed of the internal combustion engine based on the actual vehicle speed, compares the target rotational speed with the actual rotational speed of the internal combustion engine, and determines cancellation of the fuel cut prohibition from the comparison result. Accordingly, it is possible to appropriately cancel the fuel cut prohibition. In addition, it is possible to determine whether or not the actual rotational speed of the internal combustion engine is excessive, and if it is excessive, the logic can be configured to cancel the fuel cut prohibition, thereby appropriately implementing the fuel cut prohibition cancellation. can do. Furthermore, if this target rotational speed is set in terms of the second speed, the fuel cut prohibition cancellation can be appropriately determined substantially corresponding to the speed state during deceleration of the vehicle.

Alternatively, the fuel cut prohibition canceling means is set to perform setting of the target rotational speed and determination of prohibition cancellation when the transmission connected to the internal combustion engine is in a power transmission state, and the target rotational speed setting means selects By setting the target rotational speed in accordance with the transmission gear stage that is set, it is possible to reliably determine whether or not to cancel the fuel cut prohibition even when the transmission is in a power transmission state. At this time, the target rotational speed is set so as to change more gradually as the gear speed is higher , that is, the target rotational speed is reduced according to the transmission gear stage of the transmission connected to the internal combustion engine. By setting the gear position in the case of the high speed gear position lower than that in the case of the low speed speed stage, it is possible to appropriately determine the release of fuel cut prohibition corresponding to the time of deceleration. By converting and setting the case, it is possible to appropriately determine whether or not to cancel the fuel cut prohibition substantially corresponding to the shift stage state during deceleration of the vehicle.

  Alternatively, the fuel cut prohibition canceling means may assume that when the transmission connected to the internal combustion engine is in a neutral state, the vehicle speed corresponding to the actual rotational speed of the internal combustion engine is assumed to be connected to a predetermined gear stage. , And the actual vehicle speed of the vehicle is compared with the estimated vehicle speed, and the cancellation of the fuel cut prohibition is determined from the comparison result, so that the fuel cut prohibition can be canceled appropriately.

When the prohibit fuel cut by fuel cut prohibiting means, by retarding the ignition timing of the internal combustion engine, it is possible to suppress the generation of prone excessive engine torque as compared with the fuel cut in the fuel cut prohibition, driving comfort The ring can be made good.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, a first embodiment of the present invention will be described. FIGS. 1 to 3 show a control apparatus for an internal combustion engine for a vehicle as a first embodiment of the present invention, and FIG. 1 is a schematic diagram showing the overall configuration thereof. FIG. 2 is a flowchart for explaining the control contents, and FIGS. 3A to 3C are diagrams (a graph showing the engine speed) for explaining the release determination of the fuel cut prohibition control.

  In the present embodiment, as an example of an internal combustion engine, an example in which the present control device is applied to a direct injection internal combustion engine that directly injects fuel into a combustion chamber (a direct injection engine, hereinafter simply referred to as an engine) is shown. Also, in the second to fourth embodiments described later, an example in which the present control device is applied to a direct injection engine is shown, but it is needless to say that an internal combustion engine to which the present control device can be applied is not limited to the direct injection engine. It is.

As shown in FIG. 1, this in-cylinder engine is connected to a combustion chamber 1 so that an intake passage 2 and an exhaust passage 3 can communicate with each other, and the intake passage 2 and the combustion chamber 1 are exhausted by an intake valve 4. The passage 3 and the combustion chamber 1 are controlled to communicate with each other by an exhaust valve 5.
Further, in the intake passage 2, an air cleaner 2a, an air flow sensor (AFS) 2b for detecting the intake air amount, a throttle valve 2c for controlling the intake air amount, and a throttle position sensor (TPS) 2d for detecting the opening degree of the throttle valve 2c are provided. , An intake pressure sensor 2e for detecting the intake pressure is provided. The throttle valve 2c is configured by an electronically controlled throttle valve (ETV) that can be operated independently of the amount of depression of the accelerator pedal.

Further, in the exhaust passage 3, the exhaust temperature immediately upstream of an O ₂ sensor 3 a for detecting the O ₂ concentration in the exhaust and a three-way catalyst (hereinafter also simply referred to as a catalyst) 6 as an exhaust purification catalyst is supplied to the catalyst 6. catalyst temperature sensor (catalytic temperature detecting means) 3b for detecting a temperature T _C, an exhaust pressure sensor 3c for detecting an exhaust pressure muffler is provided (not shown).
Furthermore, an injector 8 is arranged in the combustion chamber 1 so that its opening faces the combustion chamber 1 so as to inject fuel directly into the combustion chamber 1.

  With such a configuration, the air sucked through the air cleaner 2a according to the opening degree of the throttle valve 2c is sucked into the combustion chamber 1 by opening the intake valve 4, and is formed on the upper surface of the piston in the combustion chamber 1 This is generated in a vertical vortex (reverse tumble flow) by the concave portion 1a and mixed with the fuel injected from the injector 8 based on a signal from an ECU (electronic control unit) 20 as a control means.

Then, the ignition plug 7 is ignited at an appropriate timing in the combustion chamber 1 to combust the air-fuel mixture to generate engine torque. After that, exhaust gas is discharged from the combustion chamber 1 to the exhaust passage 3, and the catalyst After being purified at 6, it is silenced by a muffler and discharged.
In addition to the above-described AFS 2b, TPS 2d, O ₂ sensor 3a, and catalyst temperature sensor 3b, this engine includes, for example, a crank angle detector 9a attached to the crankshaft 9 and a transmission (not shown) connected to the engine. Various sensors such as a gear stage detector (gear stage detecting means) 10 for detecting the current gear stage (which gear stage is selected or in a neutral state) of (automatic transmission or manual transmission) The detection information from these sensors is sent to ECU20.

In the in-cylinder in-cylinder injection engine, the intake air is generated in a reverse tumble flow in the combustion chamber 1 in this manner, so that a small amount of fuel is collected in the vicinity of the spark plug 7 and stratified combustion is performed. Combustion at a low air-fuel ratio (lean combustion) is possible.
The present in-cylinder injection engine, as an aspect of the fuel injection, the lean operation in this way perform operation under a lean air-fuel ratio, the O ₂ sensor 3a so that the air-fuel ratio becomes the stoichiometric air-fuel ratio (stoichiometric) near The stoichiometric operation in which feedback control is performed based on the detected information and the rich operation in which operation is performed at a rich air-fuel ratio can be performed.

Such an operation mode, that is, the setting and control of the air-fuel ratio, is performed by the air-fuel ratio control means 21 provided in the ECU 20 according to the operating state.
That is, the air-fuel ratio control means 21 calculates the engine load Pe and the engine speed (the number of revolutions per unit time = the engine speed) Ne (operating state) based on the detection information of the TPS 2d and the crank angle detecting means 9a. The air-fuel ratio is set according to the operating state, and the air-fuel ratio is set in the order of lean operation, stoichiometric operation, and rich operation as the engine load Pe and the engine speed Ne increase.

  As described above, in the present embodiment, the temperature of the catalyst 6 is configured to be detected by the catalyst temperature sensor (catalyst temperature detection means) 3b. However, the catalyst temperature is not limited to the actually measured value. An estimated value estimated from the operating state of the engine or the like may be used. For example, the exhaust flow rate and the catalyst temperature have a linear correlation with the intake pipe pressure (engine load) as a parameter (the higher the intake pipe pressure, the higher the catalyst temperature with respect to the exhaust flow rate). The temperature of the catalyst can also be estimated based on the engine load state) and the exhaust flow rate. The catalyst temperature sensor 3b is a so-called high temperature sensor and is expensive, but if this estimation is used, the cost can be reduced.

The control device for a vehicle internal combustion engine according to the present embodiment is configured as a functional element in the ECU 20, and cuts off the fuel supply when the air-fuel ratio control means 21 and a preset fuel cut condition are satisfied. A fuel cut control unit 22 that performs fuel cut, and a fuel cut prohibition unit 23 that prohibits fuel cut if the catalyst temperature detected by the catalyst temperature detection unit 3b exceeds the catalyst upper limit temperature even when the fuel cut condition is satisfied. The fuel cut prohibition canceling means 24 for canceling the fuel cut prohibition when the preset fuel cut prohibition canceling condition is satisfied during the fuel cut prohibition control, and the ignition timing control means for retarding the ignition timing of the internal combustion engine 25 and the above-described catalyst temperature sensor (catalyst temperature detection means) 3b.
Further, the fuel cut prohibition canceling means 24 compares the target engine speed setting means 26 for setting the target engine speed based on the actual vehicle speed, and compares the actual engine speed with the target engine speed. A determination means 27 for determining cancellation of prohibition of fuel cut is provided.

  Next, with reference to the flowchart (steps S1 to S14) shown in FIG. 2, the operation and control procedure of the control of the internal combustion engine by the control device for the vehicle internal combustion engine of the present embodiment configured as described above will be described. explain. Note that the flowchart of FIG. 2 is executed at a predetermined cycle.

  When the engine is operating, as shown in FIG. 2, it is first determined whether or not the flag F is 0 (step S1). This flag F is set to 1 when the fuel cut (hereinafter also referred to as F / C) condition is satisfied, and is set to 0 when the fuel cut condition is not satisfied. If the fuel cut condition is not satisfied, the flag F is 0. Therefore, the process proceeds to step S2, and the fuel cut control means 22 determines whether a preset fuel cut condition is satisfied. Here, as the fuel cut condition, for example, the vehicle is decelerating (it can be detected that the vehicle is decelerating or decelerating, for example, the accelerator is not depressed), and the engine speed Ne. Is equal to or greater than a preset lower limit value Ne0 (if the engine speed Ne is too low, there is a risk of engine stall due to fuel cut, so a predetermined speed Ne0 is provided as the fuel supply return speed) Is set to

  If it is determined that the fuel cut condition is not satisfied, the process proceeds from step S2 to step S3, and the fuel cut by the fuel cut control means 22 is not performed, and normal fuel injection control is performed. . On the other hand, if the fuel cut control means 22 determines that the fuel cut condition is satisfied, the process proceeds from step S2 to step S4, the flag F is set to 1, and the process further proceeds to step S5, where the catalyst temperature detection means 3b. It is determined whether the catalyst temperature detected in step 1 is higher than a preset temperature. This set temperature is set to a temperature lower than the heat-resistant temperature by a predetermined temperature, for example, based on the heat-resistant temperature (usage limit temperature) of the catalyst.

Here, if it is determined that the catalyst temperature is not higher than the preset temperature, the process proceeds from step S5 to step S6, and the fuel cut control means 22 performs the fuel cut control as usual. Yes.
On the other hand, if it is determined that the catalyst temperature is higher than the preset temperature, the process proceeds from step S5 to step S7, where the fuel cut prohibiting means 23 prohibits the fuel cut by the fuel cut control means 22 and It is comprised so that cut prohibition control may be implemented.

When the fuel cut prohibition control is performed, the air-fuel ratio is controlled to be slightly richer than stoichiometric (theoretical air-fuel ratio) under predetermined conditions, and the ignition timing is retarded. .
That is, during execution of the fuel cut prohibition control, the intake pressure of the internal combustion engine detected by the intake pressure sensor 2e is equal to or greater than a predetermined negative pressure value (that is, the internal combustion engine is in a high boost state and combustion is unstable). Or the intake air amount of the internal combustion engine detected by the AFS 2b is equal to or less than a predetermined value set in advance (that is, the intake air amount is low and combustion is unstable), or the exhaust gas detected by the O ₂ sensor 3a When the oxygen concentration is equal to or higher than a predetermined value set in advance (for example, the oxygen concentration is 2 to 3% or higher), the air-fuel ratio control means 21 makes the air-fuel ratio richer than stoichio (theoretical air-fuel ratio) (for example, The air-fuel ratio is controlled to be about A / F13).

Even when the air-fuel ratio is stoichiometric when the fuel cut is prohibited, the oxidation reaction of the catalyst occurs due to residual oxygen in the exhaust system and the temperature of the catalyst 6 rises, but the air-fuel ratio is slightly richer than the stoichiometric (air-fuel ratio) 13), the oxidation reaction of the catalyst due to residual oxygen can be suppressed, and the temperature rise of the catalyst 6 can be suppressed.
Further, when the torque obtained from the engine load Pe and the engine speed Ne is generated at a predetermined value or more during the fuel cut prohibition control, the ignition timing control means 25 retards the ignition timing of the internal combustion engine (for example, Ignition timing TDC to ATDC10). Although the engine output torque can be suppressed by fuel cut during deceleration and the deceleration performance can be ensured, the engine output torque is increased due to prohibition of fuel cut and the desired deceleration performance cannot be ensured However, by retarding the ignition timing in this manner, it is possible to suppress the generation of engine torque and improve the driving feeling (deceleration feeling). .

Then, during the fuel cut prohibition control, the shift state of the transmission (not shown) connected to the internal combustion engine is determined based on the shift stage detected by the shift stage detector 10 by the fuel cut prohibition release means 24. It is determined whether or not it is in a neutral state (step S8).
Here, when it is determined that the shift speed state is not neutral, the process returns. However, when it is determined that the shift speed state is neutral, the process proceeds to step S9, and the target rotation speed setting means 25 of the fuel cut prohibition release means 24 performs the process. The target engine speed Net is set based on the actual vehicle speed. In other words, as shown in the following equation (1), the target rotational speed setting means 25 sets the speed ratio corresponding to the current vehicle speed detected in real time [final reduction ratio (here, assumed when the second speed is selected). The target rotational speed Net is calculated by integrating the vehicle wheel circumference 2πr (value divided by r: wheel effective radius)].

Target rotational speed Net = current vehicle speed × (final reduction ratio ÷ 2πr) (1)
Then, the determination means 26 of the fuel cut prohibition release means 24 compares the target engine speed Net with the current engine speed Ne, and determines the cancellation of the fuel cut prohibition from the comparison result. That is, the target engine speed Net is compared with the current engine speed Ne, and whether or not the current engine speed Ne obtained based on the detection signal from the crank angle detection device 9a is larger than the target engine speed Net. Is determined (step S10).

In step S10, the engine speed Ne is compared with a value Net + α obtained by adding a minute amount α to the target speed Net, so that the fuel is detected when the engine speed Ne is reliably too high. You may set so that cutting prohibition may be cancelled | released.
Here, the routine returns when it is determined that the current engine speed Ne is not larger than the target engine speed Net, but here, when the current engine speed Ne is larger than the target engine speed Net, the determination is made. The means 26 determines whether to cancel the fuel cut prohibition, and proceeds to step S11 to cancel the fuel cut prohibition.

  That is, as shown in FIGS. 3A to 3C, when the target engine speed Net is set according to the vehicle speed from the time of neutral detection (clutch disengagement), if it is normal, the solid line As shown in the figure, the engine speed Ne follows the target speed Net corresponding to the vehicle speed or decreases more than this, and then the fuel cut release condition is surely established, and the fuel cut is canceled together with the fuel cut release. The ban can be lifted. However, when an abnormal (excessive) torque is generated in the engine, as indicated by a one-dot chain line, the engine rotational speed Ne does not decrease along the target rotational speed Net, and fuel due to a decrease in the engine rotational speed Ne. The establishment of the cut cancellation condition may not be realized. In this way, when the engine speed Ne is larger than the target speed Net, the determination means 26 determines that the fuel cut prohibition is to be canceled, so that the fuel cut prohibition is reliably canceled. (Step S11).

  Note that when setting the target rotational speed Net, the target rotational speed Net is set assuming that the speed stage is the second speed regardless of which speed stage is selected. When the cut is performed, since at least the speed stage is 2nd or higher, the target speed Net is set assuming that the speed stage is 2nd, and the actual speed Ne becomes larger than this. This is because if the logic for determining that the engine torque is excessive is employed, even if the shift speed is 3rd speed or 4th speed, it can be determined equivalent to the case of 2nd speed.

On the other hand, in the control cycle after the flag F is set to 1 in step S4, the flag F is determined to be 1 in step S1, and the process proceeds to step S12 to determine whether or not the fuel cut cancellation condition is satisfied. The Here, the fuel cut cancellation condition is, for example, that the vehicle is not decelerating (for example, it can be detected that the accelerator is depressed), or the engine speed Ne is equal to or lower than a preset lower limit value Ne1. (This lower limit value Ne1 is lower than the lower limit value Ne0 of the fuel cut condition).
If the fuel cut cancellation condition is not satisfied, the process proceeds to step S5 and the above-described processing is performed. If any one of the fuel cut cancellation conditions is satisfied, the process proceeds to step S13 and the flag F is set to 0. In step S14, the fuel cut is canceled. In step S11, the prohibition of fuel cut is canceled.

  Since the control apparatus for an internal combustion engine for a vehicle as the first embodiment of the present invention is configured as described above, even if the fuel cut condition is satisfied and the fuel cut control is performed, the catalyst temperature is equal to or higher than a predetermined temperature. If so, since the rich operation is performed by the air-fuel ratio control means 21, it is possible to prevent the catalyst from being in an air-fuel ratio state (a lean air-fuel ratio state including the vicinity of stoichio) that is likely to cause an oxidation reaction on the catalyst at a high temperature. And thermal degradation of the catalyst can be suppressed.

In particular, by making the air-fuel ratio slightly richer than stoichiometric, it is possible to suppress a situation in which residual oxygen in the exhaust system causes an oxidation reaction on the catalyst, and it is possible to reliably suppress thermal deterioration of the catalyst.
At this time, if the torque of the internal combustion engine is greater than or equal to a predetermined value, the ignition timing is retarded by the ignition timing control means 25, so the torque of the internal combustion engine can be suppressed and the driver's feeling of deceleration is impaired. The driving feeling can be improved.

In addition, when the vehicle is decelerating, the transmission is often temporarily in the neutral state. Therefore, when the transmission is in the neutral state, it is easy to cancel the fuel cut prohibition by determining whether to cancel the fuel cut prohibition. Thus, smooth control can be performed, and high-accuracy control that achieves both fuel efficiency improvement, which is the original purpose of fuel cut control, and heat deterioration prevention control of the catalyst can be performed.
Further, since the cancellation of the fuel cut prohibition control is performed based on the engine speed, it is easy to avoid the adverse effect of the torque fluctuation of the internal combustion engine when the fuel cut prohibition control is canceled, and the deterioration of the driving feeling can be suppressed. .

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIGS. 4 to 6 show a control apparatus for an internal combustion engine for a vehicle as a second embodiment of the present invention, and FIG. FIGS. 5 and 5 are flowcharts for explaining the control contents, and FIGS. 6A to 6C are diagrams (graphs showing the vehicle speed) for explaining the release determination of the fuel cut prohibition control. 4, the same reference numerals as those in FIG. 1 indicate the same elements, and in FIG. 5, the same reference numerals as those in FIG. 2 indicate the same elements, and the description thereof is omitted.

In the present embodiment, a fuel cut prohibition release determination method of the fuel cut prohibition release unit 24a is different from that in the first embodiment. That is, in the first embodiment, the fuel cut prohibition cancellation determination is made by paying attention to the engine speed, whereas in the present embodiment, the fuel cut prohibition release determination is made by focusing on the vehicle speed. Yes.
That is, as shown in FIG. 4, in the fuel cut prohibition releasing means 24a of the present embodiment, when the transmission connected to the engine is in the neutral state, the transmission is at a predetermined gear stage (here, the second speed). The Ne corresponding vehicle speed estimating means (engine speed corresponding vehicle speed estimating means) 26a for estimating the vehicle speed VsT corresponding to the actual rotational speed Ne of the internal combustion engine, and the actual vehicle speed (current vehicle speed) Vs of the vehicle The vehicle speed VsT estimated by the Ne corresponding vehicle speed estimation means 26a is compared, and a determination means 27a for determining cancellation of the fuel cut prohibition from the comparison result is provided.

Therefore, in the present embodiment, as shown in FIG. 5, during the fuel cut prohibition control, the shift stage state of the transmission is determined based on the shift stage detected by the shift stage detector 10 by the fuel cut prohibition release means 24a. It is determined whether or not it is in a neutral state (step S8).
Here, if it is determined that the shift speed state is neutral, the process proceeds to step S19, where the Ne corresponding vehicle speed estimation means 26a of the fuel cut prohibition release means 24a performs actual execution at a predetermined shift speed (second speed here). A vehicle speed VsT corresponding to the engine speed Ne is estimated. That is, as shown in the following equation (2), the speed ratio [vehicle wheel circumference 2πr (r: wheel effective radius) corresponding to the engine speed Ne detected in real time is selected as the final reduction ratio (here, the second speed is selected). The value corresponding to the time) is multiplied by] to calculate the Ne corresponding vehicle speed VsT.

VsT = current engine speed Ne × (2πr ÷ final reduction ratio) (2)
Then, the determination means 27a of the fuel cut prohibition release means 24a compares the Ne corresponding vehicle speed VsT with the current actual vehicle speed Vs, and determines the cancellation of the fuel cut prohibition from the comparison result. That is, the Ne corresponding vehicle speed VsT and the current actual vehicle speed Vs are compared, and it is determined whether the Ne corresponding vehicle speed VsT is larger than the actual vehicle speed Vs (step S20).

In step S20, the Ne corresponding vehicle speed VsT is surely excessively increased by making a determination by comparing the Ne corresponding vehicle speed VsT with a value Vs + α obtained by adding a minute amount α to the actual vehicle speed Vs. You may set so that fuel cut prohibition may be cancelled | released.
Here, if it is determined that the Ne corresponding vehicle speed VsT is not higher than the actual vehicle speed Vs, the routine returns. However, if the Ne corresponding vehicle speed VsT is higher than the actual vehicle speed Vs, the determination means 26a prohibits fuel cut. The cancellation is determined, and the process proceeds to step S11 to cancel the fuel cut prohibition.

That is, as shown in FIGS. 6A to 6C, when the vehicle speed VsT corresponding to the actual engine speed Ne at a predetermined gear position (second speed) is set from the time of neutral detection (clutch disengagement). In the normal case, as indicated by the broken line, the vehicle speed VsT corresponding to the engine rotational speed Ne follows the actual vehicle speed (current vehicle speed) Vs or decreases more than this, and then inevitably fuel cut The cancellation condition is established reliably, and the fuel cut prohibition can be canceled together with the fuel cut cancellation. However, when an abnormal (excessive) torque is generated in the engine, as indicated by a one-dot chain line, the vehicle speed VsT corresponding to the engine speed Ne does not decrease so as to follow the actual vehicle speed Vs, and the engine speed Ne The fuel cut cancellation condition may not be satisfied due to the decrease. As described above, when the vehicle speed VsT corresponding to the engine speed Ne is higher than the actual vehicle speed Vs, the determination unit 26a determines that the fuel cut prohibition is cancelled, so that the fuel cut prohibition is reliably cancelled. (Step S11).
Note that the second speed is selected as the gear position when setting the vehicle speed VsT for the same reason as in the first embodiment.

  With such a configuration, the same effect as that of the first embodiment can be obtained also by the control apparatus for an internal combustion engine for a vehicle according to the present embodiment.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIGS. 7 to 9 show a control apparatus for an internal combustion engine for a vehicle as a third embodiment of the present invention, and FIG. FIGS. 8A and 8B are flowcharts for explaining the control contents, and FIGS. 9A to 9C are diagrams (graphs showing gear ratios) for explaining the release determination of the fuel cut prohibition control. 7, the same reference numerals as those in FIGS. 1 and 4 indicate the same elements. In FIG. 8, the same reference numerals as those in FIGS. 2 and 5 indicate the same elements, and the description thereof is omitted. To do.

This embodiment is different from the first and second embodiments in the fuel cut prohibition canceling means 24b. That is, in the present embodiment, the determination of canceling the fuel cut prohibition is made by paying attention to the ratio between the engine speed and the vehicle speed.
That is, as shown in FIG. 7, in the fuel cut prohibition releasing means 24b of the present embodiment, a ratio corresponding to a gear ratio based on the current engine speed Ne, the current vehicle speed Vs, and the wheel circumference (hereinafter referred to as current rotation). The current rotation speed / vehicle speed correspondence ratio calculation unit 28 for calculating the current speed / vehicle speed correspondence ratio, and the fuel cut prohibition cancellation based on the preset target gear ratio (constant value) and the current rotation speed / vehicle speed correspondence ratio. A determination means 27b for performing the determination is provided. Here, the target gear ratio is set, for example, to a value that is larger by a predetermined value than the final reduction ratio at the second speed, based on the final reduction ratio at the second speed.

The determination means 27b compares the preset target gear ratio with the current rotation speed / vehicle speed correspondence ratio calculated by the current rotation speed / vehicle speed correspondence ratio calculation unit 28, and determines whether to cancel the fuel cut prohibition based on the comparison result. When the condition for canceling the fuel cut prohibition is satisfied, the cancellation of the fuel cut prohibition is determined.
That is, in the present embodiment, as shown in FIG. 8, determination is performed in the same manner as in the first embodiment (similar to steps S1 to S7 in FIG. 2), and in step S8, the gear position state is neutral. When the determination is made, the process proceeds to step S30, where the current rotation speed / vehicle speed correspondence ratio calculation unit 28 of the fuel cut prohibition release means 24b performs the current rotation based on the current engine speed Ne, the current vehicle speed Vs, and the wheel circumference 2πr. The number / vehicle speed correspondence ratio Get is calculated. As shown in the following equation (3), the current rotational speed / vehicle speed correspondence ratio calculating unit 28 divides a value obtained by adding the wheel circumference 2πr to the current engine rotational speed Ne detected in real time by the current vehicle speed Vs. Then, the current rotation speed / vehicle speed correspondence ratio Get is calculated.

Get = current engine speed Ne × 2πr ÷ current vehicle speed Vs (3)
Then, the determination unit 27b of the fuel cut prohibition release unit 24b compares the target gear ratio with the current rotation speed / vehicle speed correspondence ratio Get calculated by the current rotation speed / vehicle speed correspondence ratio calculation unit 28, and calculates the fuel from this comparison result. The release of cut prohibition is determined. That is, the target gear ratio is compared with the current rotational speed / vehicle speed correspondence ratio Get to determine whether the current rotational speed / vehicle speed correspondence ratio Get is smaller than the target gear ratio (step S31).

Here, when the current rotational speed / vehicle speed correspondence ratio Get is smaller than the target gear ratio, the determination unit 27b determines cancellation of the fuel cut prohibition, and proceeds to step S11 to cancel the fuel cut prohibition.
In other words, as shown in FIGS. 9A to 9C, when the current rotation speed / vehicle speed correspondence ratio Get is set from the time of neutral detection (clutch disengagement), as shown by a solid line in a normal case. In addition, the current engine speed / vehicle speed correspondence ratio Get corresponding to the actual engine speed Ne and the vehicle speed Vs is in line with the target gear ratio or is significantly lower than that. The fuel cut prohibition can be canceled together with the cancellation of the fuel cut. However, if an abnormal (excessive) torque is generated in the engine after the neutral detection time, the current rotation speed / vehicle speed correspondence ratio Get does not decrease so as to follow the target gear ratio, as shown by a one-dot chain line. The fuel cut cancellation condition may not be satisfied due to a decrease in the current rotation speed / vehicle speed correspondence ratio Get. As described above, when the current rotation speed / vehicle speed correspondence ratio Get is larger than the target gear ratio, the determination unit 27b determines that the fuel cut prohibition is to be canceled, so that the fuel cut prohibition is reliably canceled. (Step S11).

Note that when setting the target gear ratio, the target gear ratio is set on the assumption that the gear stage is 2nd speed, regardless of which gear stage is selected. At the time of execution, since at least the speed stage is 2nd speed or higher, the target gear ratio is set assuming that the speed stage is 2nd speed, and the current speed / vehicle speed correspondence ratio Get is larger than this. In this case, if the logic for determining that the engine torque is excessive is adopted, even when the gear position is 3rd speed or 4th speed, it can be determined equivalent to the case of 2nd speed.
On the other hand, if it is determined in step S31 that the current rotation speed / vehicle speed correspondence ratio Get is not larger than the target gear ratio, the routine returns.
If it is determined in step S8 that the gear position is not neutral, the process returns.

  With such a configuration, the same operation and effect as in the first and second embodiments can be obtained also by the control apparatus for an internal combustion engine for a vehicle according to the present embodiment.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 10 and FIG. 11 show a control apparatus for a vehicle internal combustion engine as a fourth embodiment of the present invention, and FIG. FIGS. 11A and 11B are flowcharts (a graph showing the engine speed) for explaining determination of canceling the fuel cut prohibition control. 10, the same reference numerals as those in FIGS. 2, 5, and 8 indicate the same elements, and the description thereof is omitted.

  Since this embodiment is configured in the same manner as the first embodiment (see FIG. 1) in terms of functional configuration, FIG. 1 is used and some of the codes are replaced (see the parenthesized codes in FIG. 1). )explain. In the present embodiment, the fuel cut prohibition release determination method of the fuel cut prohibition release unit 24c is different from the first to third embodiments. That is, in the present embodiment, the determination of canceling the fuel cut prohibition is performed noting when the transmission is in the neutral state but paying attention to the engine speed when in the power transmission state.

  That is, as shown in FIG. 1, in the fuel cut prohibition releasing means 24c of the present embodiment, when the transmission connected to the engine is in a power transmission state, the target engine speed is set according to the transmission gear stage. Target rotational speed setting means 26b, and determination means 27c for comparing the actual rotational speed of the engine with the target rotational speed to perform fuel cut prohibition release determination.

  The target rotational speed setting means 26b sets the target rotational speed (target deceleration rate) NeT-t1 as shown by a broken line in FIG. Is a low speed (here, 2nd speed or less, substantially only 2nd speed), the target rotational speed (target deceleration rate) NeT-t2 is set as shown by the broken line in FIG. In each figure, a plurality of target engine speeds are set. This is based on the actual engine speed when the fuel cut prohibition condition is satisfied, and any one of these target engine speeds is selected. This is for selecting and using.

  This target speed is set more gently than the standard speed reduction assumed when the fuel is cut during deceleration. In addition, as the high speed stage is selected, the deceleration is generally slower. Thus, as shown in FIGS. 11 (a) and 11 (b), the target engine speed is set so that the high-speed stage gradually decreases compared to the low-speed stage. Further, this target engine speed is set from the fuel cut start time, and when the high speed stage is selected, the target engine speed is initially set to a speed higher than the actual engine speed Ne-s at the fuel cut start time. If the low speed stage is selected as the target engine speed, the engine speed is initially set to be higher than the actual engine speed Ne-s at the start of fuel cut. The target rotational speed is set so as to decelerate relatively rapidly thereafter.

  With such a configuration, control is performed as shown in FIG. Although description of the same part as 1st Embodiment (refer FIG. 2) is abbreviate | omitted, in this embodiment, as shown in FIG. 10, when fuel cut prohibition control (step S7) is implemented, first, Then, it is determined whether or not the gear stage is a high speed stage (here, 3rd speed or higher) (step S21). When the gear stage is a high speed stage, the target rotational speed NeT-t1 is set as indicated by a broken line in FIG. It is set (step S22), and it is determined by the determination means 27c whether the actual rotational speed Ne exceeds the target rotational speed NeT-t1 (step S23). If the actual rotational speed Ne exceeds the target rotational speed NeT-t1, The fuel cut prohibition control is canceled (step S11). When the gear stage is a low speed stage, a target rotational speed NeT-t2 is set as shown by a broken line in FIG. 11B (step S24), and the determination means 27c sets the actual rotational speed Ne to the target rotational speed NeT-t1. Is exceeded (step S25), and when the actual rotational speed Ne exceeds the target rotational speed NeT-t1, the fuel cut prohibition control is canceled (step S11).

  With such a configuration, according to the control apparatus for an internal combustion engine for a vehicle as the present embodiment, even if the fuel cut condition is established and the fuel cut control is performed as in the first to third embodiments, the catalyst temperature If the temperature is equal to or higher than the predetermined temperature, the rich operation is performed by the air-fuel ratio control means 21, so that the catalyst is in an air-fuel ratio state (a lean air-fuel ratio state including the vicinity of stoichio) that is likely to cause an oxidation reaction on the catalyst. And thermal deterioration of the catalyst can be suppressed.

At this time, if the torque of the internal combustion engine is greater than or equal to a predetermined value, the ignition timing is retarded by the ignition timing control means 25, so the torque of the internal combustion engine can be suppressed and the driver's feeling of deceleration is impaired. The driving feeling can be improved.
Furthermore, when decelerating, the fuel cut prohibition is canceled as necessary by determining whether to cancel the fuel cut prohibition according to the selected gear position of the transmission, and smooth control is performed. Therefore, it is possible to perform highly accurate control that achieves both fuel efficiency improvement, which is the original purpose of fuel cut control, and catalyst thermal deterioration prevention control.

In this embodiment, the shift stage is divided into two stages, a high speed stage (3rd speed or more) and a low speed stage (2nd speed or less), and the release of the fuel cut prohibition is determined. The determination may be made in more detail.
For example, as indicated by a two-dot chain line in FIG. 11 (a), the target rotational speed NeT-t3 when the gear stage is 4th speed is set, and when the gear stage is 4th gear, the actual rotational speed Ne is the target rotational speed. The cancellation of the fuel cut prohibition is determined based on whether or not the number NeT-t3 or more. When the gear position is the third speed, the gear position is determined depending on whether or not the actual speed Ne is equal to or more than the target speed NeT-t1. In the case of the second speed, the cancellation of the fuel cut prohibition may be determined depending on whether the actual rotational speed Ne is equal to or higher than the target rotational speed NeT-t2. In this case, the target rotational speed NeT-t3 is set so as to decrease more slowly than the target rotational speed NeT-t1.

In this case as well, the target rotational speed NeT-t3 is set from the start of fuel cut, but the initial value of the target rotational speed NeT-t3 is greater than the initial value of the target rotational speed NeT-t1 at this time. It is preferable to set a value close to the actual engine speed Ne-s (at the time of starting fuel cut) (however, greater than the actual engine speed Ne-s).
In such a case, control is performed as shown in FIG. Although description of the same part as 4th Embodiment (refer FIG. 10) is abbreviate | omitted, as shown in FIG. 12, step S26-S28 is added with respect to the thing of 4th Embodiment, and the gear stage is changed. If it is determined whether the speed is the fourth speed (step S26) and the shift speed is the fourth speed, the target rotational speed NeT-t3 is set as described above (step S27), and the actual speed is determined by the determination means 27c. It is determined whether Ne exceeds the target rotational speed NeT-t3 (step S28). If the actual rotational speed Ne exceeds the target rotational speed NeT-t1, the fuel cut prohibition control is canceled (step S11).
By performing the control in this way, it becomes possible to release the fuel cut prohibition control according to the traveling state (engine operating state).

Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the determination unit of the fuel cut prohibition release unit may be configured to perform both the determination by the determination unit 27 of the first embodiment and the determination by the determination unit 27a of the second embodiment.

1 is a schematic diagram showing a configuration of a control device for an internal combustion engine for a vehicle as a first embodiment of the present invention. It is a flowchart explaining the control by the control apparatus of the internal combustion engine for vehicles as 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure (graph which shows an engine speed) for demonstrating cancellation | release determination of the fuel cut prohibition control by the control apparatus of the vehicle internal combustion engine as 1st Embodiment of this invention, Comprising: (a) is 2nd speed deceleration. (B) shows the case of the third speed reduction, and (c) shows the case of the fourth speed reduction. It is a schematic diagram which shows the structure of the control apparatus of the internal combustion engine for vehicles as 2nd Embodiment of this invention. It is a flowchart explaining the control by the control apparatus of the internal combustion engine for vehicles as 2nd Embodiment of this invention. It is a figure (graph which shows a vehicle speed) for demonstrating cancellation | release determination of the fuel cut prohibition control by the control apparatus of the vehicle internal combustion engine as 2nd Embodiment of this invention, Comprising: (a) is the case of 2nd speed deceleration. (B) shows the case of the third speed reduction, and (c) shows the case of the fourth speed reduction. It is a schematic diagram which shows the structure of the control apparatus of the internal combustion engine for vehicles as 3rd Embodiment of this invention. It is a flowchart explaining the control by the control apparatus of the internal combustion engine for vehicles as 3rd Embodiment of this invention. FIG. 6 is a diagram (a graph showing a gear ratio) for explaining determination of cancellation of fuel cut prohibition control by a control device for an internal combustion engine for a vehicle according to a third embodiment of the present invention, in which (a) is a case of second speed deceleration; (B) shows the case of 3-speed deceleration, and (c) shows the case of 4-speed deceleration. It is a flowchart explaining the control by the control apparatus of the internal combustion engine for vehicles as 4th Embodiment of this invention. It is a figure (a graph which shows engine speed) for demonstrating cancellation | release determination of the fuel cut prohibition control by the control apparatus of the vehicle internal combustion engine as 4th Embodiment of this invention, Comprising: (a) is in a high speed stage. The case of deceleration is shown, and (b) shows the case of deceleration at a low speed stage. It is a flowchart explaining the control by the control apparatus of the internal combustion engine for vehicles of the modification concerning 4th Embodiment of this invention.

Explanation of symbols

3b Catalyst temperature sensor (catalyst temperature detection means)
20 ECU
21 Air-fuel ratio control means 22 Fuel cut control means 23 Fuel cut prohibition means 24, 24a, 24b, 24c Fuel cut prohibition release means 25 Ignition timing control means 26, 26a, 26b Target rotational speed setting means 27, 27a, 27b, 27c Determination Means 28 Current Speed / Vehicle Speed Correspondence Ratio Calculation Unit

Claims (3)

A control device for an internal combustion engine for a vehicle, which includes an exhaust purification catalyst, and includes a fuel cut control means for performing fuel cut to stop fuel supply when a preset fuel cut condition is satisfied,
A catalyst temperature detecting means for detecting a temperature of the catalyst or a value of a parameter corresponding to the temperature;
Even if the fuel cut condition is satisfied, if the temperature detected by the catalyst temperature detection means or the value of the parameter exceeds a preset catalyst upper limit temperature, the fuel cut prohibition prohibits the fuel cut. Means,
A fuel cut prohibition canceling unit for canceling the fuel cut prohibition when a preset fuel cut prohibition canceling condition is satisfied during the fuel cut prohibition control by the fuel cut prohibiting unit;
The fuel cut prohibition release means is
A target rotational speed is set so as to decrease as time elapses, with an initial target rotational speed that is a predetermined rotational speed higher than the actual rotational speed of the internal combustion engine at the start of fuel cut prohibition by the fuel cut prohibiting means , the rate of decrease of the target speed in response to the transmission gear of the connected transmission to the internal combustion engine, the target rotational speed speed change gear stage is set lower than towards the case of the high speed stage is low speed stage Setting means;
A vehicle that includes a determination unit that compares the actual rotational speed of the internal combustion engine with the target rotational speed according to the transmission gear stage and determines cancellation of fuel cut prohibition based on the comparison result. Control device for internal combustion engine.   The air-fuel ratio control means for controlling the air-fuel ratio to be richer than the theoretical air-fuel ratio when the fuel cut is prohibited by the fuel-cut prohibiting means. Control device for internal combustion engine for vehicle. 3. The vehicle according to claim 1, further comprising ignition timing control means for retarding the ignition timing of the internal combustion engine when the fuel cut is prohibited by the fuel cut prohibiting means. Control device for internal combustion engine.

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