JP2003020969A - Controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller of an internal combustion engine capable of providing torque similar to the production of an intended output torque of the internal combustion engine, providing an excellent response characteristic, and preventing such a problem from occurring that the wall surface temperature of a specified cylinder is lowered by fuel cut. SOLUTION: In the control device of the internal combustion engine for performing the fuel cut at a specified rate for all cylinders of the internal combustion engine having the plurality of cylinders, a fuel cut execution pattern is formed by taking the number of cylinders different from all cylinders, for example, 5 cylinders (1st to 5th) of a 6-cylinder internal combustion engine as one cycle and cutting fuel by a specified fuel cut pattern during one cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for an internal combustion engine having a plurality of cylinders, and more particularly to a control system for an internal combustion engine that cuts fuel in a cylinder having a predetermined ratio with respect to the total number of cylinders.

[0002]

2. Description of the Related Art As a technique for controlling engine output torque for traction control of vehicles such as automobiles,
2. Description of the Related Art In an internal combustion engine having a plurality of cylinders, a cut-off cylinder control is known in which fuel cut is performed for cylinders having a predetermined ratio to the total number of cylinders. This cut-off cylinder control can be applied to a fuel injection supply type internal combustion engine in which fuel is supplied to each cylinder by an individual fuel injector.

As a conventional technique for reducing cylinder control, Japanese Unexamined Patent Publication No.
As disclosed in Japanese Patent No. 246334, a fuel cut is performed for cylinders at equal intervals with respect to an explosion cylinder order (ignition order) to suppress torque fluctuation.
As disclosed in Japanese Patent Publication No. 10, the cylinders that continuously stop the fuel supply are set at equal intervals in the ignition order in order to increase the operating frequency of the cylinders and obtain stable combustion even when restarting. There is a control device that, when there is a request for further lowering of the operating rate, the cylinders to be further stopped are sequentially replaced from the operating cylinders and executed.

FIG. 20 shows an example of a fuel cut pattern in a conventional control device. FIG. 20 is a fuel cut pattern table with 6 cylinders as one cycle. The vertical axis shows the number of cylinders for which fuel cut is performed, and the horizontal axis shows the combustion cycle (cylinder number # 1 in the ignition sequence) that has elapsed since the request was made. ~ # 6)
Is represented. Further, in the table, "0" represents execution of fuel cut, and "1" represents execution of fuel injection.

For example, when a request to cut one cylinder is made, fuel cut is executed for one cylinder (# 1) which is next ignition timing, and fuel is cut for the remaining five cylinders (# 2 to # 6). Perform injection supply. This process repeats the same cycle unless the fuel cut request changes. As a result, the torque request can be continuously realized.

[0006]

In the case of the conventional example as shown in FIG. 20, if the fuel cut state continues, the fuel cut continues in a specific cylinder (for example, # 1 cylinder), As a result, the temperature of the wall surface of the specific cylinder decreases. After that, when the fuel cut is ended and the combustion of the specific cylinder is restarted, the vaporization of the fuel is delayed because the wall surface temperature of the cylinder is lowered, and as a result,
This may result in combustion failure. Further, in the conventional control device, the cycle of a series of fuel cut operations becomes long, the output torque fluctuation is large with respect to the intended output torque generation state of the internal combustion engine, and the response characteristic to the request is poor.

This can be improved by sequentially changing the cylinders to be stopped from the operating cylinders. However, one cycle (cycle), which is a unit of a series of fuel cut operations, becomes longer and less. It is not possible to meet the demands of completing one cycle in a number, reducing the torque fluctuation, shortening the time required for one cycle, and shortening the response to the change in the required torque.

The present invention has been made by paying attention to the above-mentioned problems, and an object of the present invention is to obtain torque generation close to an intended output torque generation state of an internal combustion engine, with good response characteristics, and fuel consumption. An object of the present invention is to provide a control device for an internal combustion engine that does not cause a problem such as a decrease in wall surface temperature of a specific cylinder due to cutting.

[0009]

In order to achieve the above object, a control device for an internal combustion engine according to the present invention is a control device for performing fuel cut of a cylinder having a predetermined ratio with respect to the total number of cylinders of an internal combustion engine having a plurality of cylinders. In the fuel cut execution pattern, the number of cylinders different from the total number of cylinders is set as one cycle, and the fuel is cut in a predetermined fuel cut pattern during one cycle.

With this, it is possible to complete the one cycle with a small number, reduce the torque fluctuation, shorten the time required for one cycle, and shorten the response to the change in the required torque. The fuel cut is not biased toward the cylinders, and the wall surface temperature of a specific cylinder is not lowered by the fuel cut. For torque control with good responsiveness, fuel cut can be performed with different preset fuel cut patterns when the number of cylinders of a predetermined ratio increases and when the number of cylinders decreases.

Further, in order to reduce the frequency of fuel cut of a specific cylinder, it is preferable that the number of cylinders included in one cycle is one less or one more than the total number of cylinders of the internal combustion engine. Further, the control device for an internal combustion engine according to the present invention performs the fuel injection amount correction or the ignition timing correction along with the fuel cut operation among the plurality of operation modes according to the operating state of the internal combustion engine so that the required torque can be obtained. The operation is performed so that the response characteristic is equivalent to that of the operation mode having a slow response characteristic. In addition, the control device for an internal combustion engine according to the present invention can perform an operation that does not perform ignition instead of the fuel cut operation.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an overall system of a multi-cylinder / cylinder injection internal combustion engine (engine) to which an embodiment of a control device for an internal combustion engine according to the present invention is applied.

The engine body 1 has a piston 3 in a combustion chamber 2 of each cylinder, and the piston 3 is a connecting rod 4.
Is connected to the crankshaft 5. An air cleaner 7, an air flow meter 8, a throttle body 10 accommodating an electronically controlled throttle valve 9, a collector 11, and an intake pipe 12 are connected to an intake port 6 of the engine body 1, and the intake port 6 of each cylinder is connected through these. Air is sucked into each combustion chamber 2 by the above. The intake port 6 is a camshaft-driven intake valve 1
It is opened and closed by 3.

The engine body 1 is provided with a fuel injector 14 for in-cylinder injection and an ignition plug 15 for each cylinder. The exhaust port 16 of the engine body 1 is opened and closed by an exhaust valve 17 driven by a cam shaft. In the exhaust port 16,
An exhaust pipe 18 and a catalytic converter 19 are connected, and exhaust gas is exhausted through these.

As a fuel supply device, an electric low-pressure fuel pump 21 for pumping fuel such as gasoline from a fuel tank 20 to primarily pressurize the fuel, and a fuel pressure regulator for adjusting the pressure of the primary pressurized fuel to a constant pressure. 22 and a camshaft-driven high-pressure fuel pump 23 for further secondary-pressurizing the regulated fuel. The secondary-pressurized high-pressure fuel is supplied to the fuel system in which the fuel injector 14 is piped. It
The fuel injector 14 directly injects high-pressure fuel into the combustion chamber 2. The fuel injected into the combustion chamber 2 is the ignition coil 2
The ignition plug 15 applied with a voltage higher than 4 ignites and burns.

A control unit 50 is provided which comprehensively controls the entire system of the cylinder injection type internal combustion engine. As shown in FIG. 2, the control unit 50 is a microcomputer type composed of an MPU 51, an EP-ROM 52, a RAM 53, an I / O / LSI 54 including an A / D converter, and the like. As various information for detecting the operating state of the engine, a signal indicating an intake air flow rate from an air flow meter (air flow sensor) 8, a signal indicating a slot valve opening degree from a throttle sensor 26, a signal indicating a crank angle from a crank angle sensor 27, A signal representing the cam angle from the cam angle sensor 28, a signal representing the air-fuel ratio from the air-fuel ratio sensor 29, a signal representing the engine cooling water temperature from the water temperature sensor 30, a signal representing the fuel pressure from the fuel pressure sensor 31, and a starter switch 32 from the starter switch 32. A signal representing the on / off state of the switch 32 is input, and a predetermined calculation is performed based on these input signals. And row control signals calculated by the various as the calculation result, the fuel injector 14, the low pressure fuel pump 21, the ignition coil 24, electrically controlled throttle valve 9
To control the fuel supply, the ignition timing, and the intake air amount. In such an apparatus, when controlling the behavior of the vehicle, such as when ensuring the running stability of the vehicle, there is a case where a request to rapidly change the output torque of the engine to a target torque occurs.

In response to such a request, there is a control method in which the intake air amount is operated by the electronically controlled throttle valve 9 and the engine output torque is set as a target value. However, the changing speed of the intake air amount is rounded by the collector 11 and averaged. Therefore, it can be difficult to say that it is quick. Therefore, the torque is controlled to the target value by operating the fuel supply method and the ignition timing.

There are two methods for changing the output torque of the internal combustion engine to the target required torque by the fuel supply control accompanied by the fuel cut to the specific cylinder. The concept of one of them is shown in FIG. FIG. 3 shows a 6-cylinder internal combustion engine as an example. Before changing the torque, the internal combustion engine outputs the torque shown on the left side of the bar graph.
The case where the intention is to change the torque after the torque change is shown. The dividing line of the bar graph represents the torque output by each cylinder (A to F).

Normally, no special operation is performed to generate a large or small torque for each cylinder, so that each cylinder (A to F)
Output torque is the same. 6 cylinders (A to F)
Among them, when the fuel supply to the two cylinders E and F is cut off and the fuel supply is stopped, the output torque Teo of the internal combustion engine becomes smaller than the required torque Tde (down to the torque Tsh). At the same time, if the fuel supply amount Fcy of each cylinder A to D that does not perform fuel cut is increased by a predetermined amount ΔF as shown in the figure and the output torque of each cylinder is increased, the internal combustion engine as a whole is increased. The required torque Tde can be realized. Note that Fall is the fuel supply amount of the entire internal combustion engine (fuel supply total value of all cylinders).

The other concept is shown in FIG. The notation method of FIG. 4 is the same as that of FIG. 6 cylinders (A to F)
Among them, when the fuel cut of one cylinder F is performed and the fuel supply is stopped, the output torque Teo of the internal combustion engine becomes the required torque Td.
A little larger than e (decreased to torque Tov). At the same time, as shown in the figure, the fuel supply amount Fcy of each cylinder (A to E) that does not perform fuel cut is reduced by a predetermined amount ΔF and the output torque of each cylinder is reduced.
e can be realized.

The above-mentioned two methods are inaccurate with respect to the required output torque, but the output torque manipulated variable is roughly manipulated by the fuel cut for each cylinder which is excellent in the range of manipulated variables.
The target torque (request torque Tde) is realized by finely adjusting the surplus by increasing or decreasing the fuel supply amount. As for which of the method (fine adjustment of fuel amount increase) shown in FIG. 3 and the method (fine adjustment of fuel amount decrease) shown in FIG. 4, the change in the air-fuel ratio caused by the fuel increase / decrease operation Can withstand combustion, or can be appropriately selected depending on the ease of operation. The control flow of this operation will be described with reference to FIG. This process is repeatedly executed every predetermined time.

First, the torque reduction amount is calculated (step S101). Here, the calculated value is, for example, a torque change rate that is a ratio between the requested engine output torque and the current engine output torque. Next, the number of cylinders for which fuel cut is performed is calculated from the calculated torque change rate (step S1).
02). The actual fuel cut can be executed only with an integral number of cylinders, but if a decimal occurs in the number of fuel cut cylinders, the decimal may remain.

Next, it is determined whether or not the calculation result of the number of fuel cut cylinders is an integer (step S103). If the calculated number of fuel cut cylinders is an integer (Yes at step S103), the required torque can be realized only by the fuel cut operation based on the number of fuel cut cylinders, and therefore the calculation of the fuel supply increase / decrease amount is not performed as it is. The process ends.

On the other hand, if the calculated number of fuel cut cylinders is not an integer (No at step S103),
It is selected whether the number of fuel cut cylinders is rounded up or down, that is, whether the fuel amount is finely adjusted (for rounding up) or the fuel amount is finely adjusted (for rounding up) (step S10).
4). This selection is to select which process is appropriate in view of whether the change in the air-fuel ratio caused by the fuel increase / decrease operation can withstand combustion, or the ease of operation.

When rounding up, fuel cutting is performed with the number of rounded up fuel cut cylinders (step S10).
5). This means that the fuel cut is performed on an integral number of cylinders larger than the calculated value of the number of fuel cut cylinders. For example, when the calculated value of the number of fuel cut cylinders is 1.5, the fuel cut of two cylinders is performed. . On the other hand, when the devaluation is performed, the fuel cut is performed with the number of the fuel cut cylinders that have been devalued (step S106). This means that the fuel cut is performed on an integral number of cylinders smaller than the calculated value of the number of fuel cut cylinders. For example, if the calculated value of the number of fuel cut cylinders is 1.5, the fuel cut of one cylinder is performed. .

Next, the torque (torque correction amount) obtained when the fuel cut is performed for the number of cylinders that are rounded up or the number of cylinders that are rounded down is calculated (step S107),
The fuel increase / decrease amount (operating cylinder fuel injection amount correction) of cylinders other than the fuel cut cylinders required for the engine output torque to reach the target torque, that is, operating cylinders is calculated (step S1).
08). When the operation shown in FIG. 3 is performed, the fuel amount increase of each cylinder for realizing the required torque is performed. When the operation shown in FIG. 4 is performed, the fuel increase amount for each cylinder is achieved. Calculate the fuel reduction of the cylinder. FIG. 6 shows the output characteristics of the torque when such an operation is performed. In response to the torque operation request, a predetermined number of cylinders are fuel cut to realize the request with an accuracy of 1 / the number of operated cylinder groups. Further, by increasing / decreasing the fuel amount in the cylinders without fuel cut, the request is made with good accuracy. Torque can be realized in a wide range.

In the above description, the method of adjusting the generated torque by operating the fuel amount in the cylinder where the fuel is not cut has been described. The premise is that the output torque of each cylinder can be increased or decreased while changing the air-fuel ratio by changing only the fuel supply amount without changing the intake air amount of each cylinder. However, when it is desired to operate the internal combustion engine at a predetermined air-fuel ratio, for example, at the stoichiometric air-fuel ratio, the degree of freedom to operate the air-fuel ratio cannot be obtained. In such a case, the output torque of each cylinder can be increased or decreased by operating the ignition timing. FIG. 7A shows the concept. Torque operability depending on the ignition timing at the stoichiometric air-fuel ratio and torque operability depending on the fuel injection amount during lean combustion (see FIG. 7B).
Can statically have the same degree of freedom.

FIG. 8 shows the tendency of the number of cylinders included in one cycle of the combustion group of the process, the control accuracy of the torque operation by the fuel cut operation, and the time required for one cycle. This is because the fuel cut can be realized only by an integral number of cylinders, and the more the number of cylinders in one cycle is, the better the control accuracy of the torque operation by the fuel cut operation, which is 1 / the number of cylinders in one cycle, is. It shows that the torque can be operated with accuracy. On the other hand, the combustion of the internal combustion engine is intermittent combustion, and in the case of a 4-cycle engine, combustion is performed for the number of cylinders by rotating the crankshaft twice. Therefore, the larger the number of cylinders included in one cycle, the longer the time required for one cycle.

Generally, in an internal combustion engine, in order to obtain a smooth output by suppressing fluctuations in torque due to intermittent combustion,
Inertia is given. If the inertia is large, the response when the output changes becomes slow, so the appropriate inertia weight is set in consideration of those advantages and disadvantages. FIG. 9 shows an example of the behavior of the output torque generation including the inertia when the fuel is cut off from one cylinder in the processing group of six cylinders and one cycle in the internal combustion engine in which the inertial weight is set. . The horizontal axis represents the number of combustions, and the vertical axis represents the torque output ratio which is 1 when the fuel is not cut.

If there is no inertia, the output torque is 0 when the fuel cut cylinders are in the combustion order, and the others are 1. However, due to the aforementioned inertia, a predetermined fluctuation is repeated and an average of 6 minutes. The output torque of 5 is obtained. That is, if the number of cylinders included in one cycle is completed with a smaller number, the torque fluctuation can be reduced, and the time required for one cycle is short, so that the response to the change in the required torque can be shortened.

However, if the number of cylinders included in one cycle is small, as described with reference to FIG. 6, a wide application capability is required for the operation of the fuel injection amount or the ignition timing in the cylinder where the fuel is not cut. Further, in one cycle, it is desirable from the viewpoint of torque fluctuation that the cylinders that perform fuel cut be distributed as uniformly as possible, as can be inferred from FIG.

A fuel cut operation can be completed by completing one cycle with a smaller number, distributing the fuel cut cylinders as uniformly as possible within one cycle, reducing torque fluctuation, and shortening the time required for one cycle. In order to meet the demand for shortening the response to changes in torque, in the present embodiment, the fuel cut is performed with the number of cylinders (N−n) or (N + m) different from the total number of cylinders N of the internal combustion engine as one cycle. did. However, N> n ≧ 1 and m ≧ 1.

One embodiment thereof is shown in FIG. In FIG. 10, “0” indicates a fuel cut cylinder,
“1” indicates a fuel injection cylinder, 1st, 2nd, 3r
d, 4th, and 5th indicate the order of the fuel cut cycle, and are not the numbers that physically specify the cylinder of the internal combustion engine such as the numbered cylinder. In this embodiment, in a 6-cylinder engine, n = 1 and 5 cylinders are set as one cycle (1st to 5th), and a cylinder cut pattern is set for each number of fuel cut cylinders (1 cylinder cut to 5 cylinder cuts). To cut fuel.

FIG. 11 shows how the fuel cut cylinder appears when the fuel cut pattern of this cycle is maintained. Since the fuel cut operation is started immediately when the torque operation request is made, the cylinder in which the operation is started is the nearest cylinder and cannot be specified. Therefore, in FIG. 10, the cylinders are designated as A to F and are not specified such as the numbered cylinder. According to FIG. 11, with a 6-cylinder engine,
The fuel cut is repeatedly performed according to the above fuel cut pattern with 5 cylinders as one cycle,
It can be seen that the fuel cut is not biased toward a specific cylinder. Therefore, the wall temperature of the specific cylinder does not decrease due to the fuel cut.

Generally, the fuel cut of a specific cylinder is represented by the cycle of the fuel cut operation and the frequency of the least common multiple of the number of cylinders. Therefore, if the fuel cut operation is performed with one or more cylinders being one cycle relative to the number of cylinders of the internal combustion engine, the least common multiple is increased, and therefore the frequency of fuel cut for a specific cylinder can be reduced. Therefore, in a 4-cylinder engine, 3 or 5 cylinders are
It is preferable to perform fuel cut operation with one cylinder having five cylinders or seven cylinders, and with eight cylinder engines having seven cylinders or nine cylinders as one cycle.

FIG. 12 shows an example of a fuel cut pattern in a 6-cylinder engine when 7 cylinders are set as one cycle (1st to 7th), and the fuel cut pattern is maintained when the fuel cut pattern of this cycle is continued. 13 is shown in FIG. As can be seen from FIG. 13, in the 6-cylinder engine, 7 cylinders are set as 1 cycle, and the fuel cut is repeatedly performed according to the above-described fuel cut pattern. Similar to the case where the fuel cut is performed, the fuel cut is not biased toward the specific cylinder, and the wall surface temperature of the specific cylinder is not lowered by the fuel cut.

Further, by setting the number of cylinders close to the total number of cylinders of the internal combustion engine as one cycle of fuel cut, the cycle close to two rotations of the crankshaft can be operated as one cycle, and the operation cycle can be specified. In the relationship between the inertial weight and the torque fluctuation, the amplitude of the torque fluctuation due to the fuel cut operation can be specified within a predetermined range. Here, whether the cycle is one more than the number of cylinders of the internal combustion engine or one less than the number of cylinders is determined from the above-mentioned torque sensitivity, responsiveness, fuel amount, degree of freedom in operating ignition timing, etc. It may be judged and selected.

Further, in FIG. 10 described above, when the uniformity is equivalent, the pattern is arranged so that the fuel cut is executed earlier in time. In the present description, the operation is to reduce the current torque with respect to the required torque, and the effect of the reduction is remarkable in the fuel cut. Therefore, the fuel cut is performed early. Here, the torque request is a request that the torque of the engine is quickly changed to a target torque when controlling the behavior of the vehicle, for example, when ensuring the running stability of the vehicle, and the request value itself. Should be assumed to change from moment to moment.

Therefore, when the number of cylinders to be subjected to fuel cut changes due to the required torque, the fuel cut pattern that has been executed up to that point is discarded, and a new fuel cut pattern is switched to operate to realize the required torque. Good to do. In such a case, when the required torque becomes smaller and the number of cylinders to be subjected to fuel cut increases, fuel cut is set earlier in the pattern shown in FIG. Suitable to be done.

On the contrary, in the case where the required torque increases from the originally small place and the number of fuel cut cylinders decreases, when the fuel cut operation is executed according to the new required fuel cut cylinder, the torque increases. Despite the desire to do so, it is a pattern in which the fuel cut is set early, so it is not possible to increase the torque quickly. Therefore, in the present invention, different fuel cut patterns can be applied depending on whether the fuel cut cylinders increase or decrease. The fuel cut pattern shown in FIG. 10 can be used when the fuel cut cylinder is increased, and the fuel cut pattern shown in FIG. 14 can be used when the fuel cut cylinder is decreased.

In the fuel cut pattern shown in FIG. 14, the time series of the fuel cut pattern shown in FIG. 10 is reversed. That is, the fuel cut cylinders are distributed as uniformly as possible, and when the uniformity is equivalent, the fuel injection is preferentially arranged, and this fuel cut pattern is reduced in the fuel cut cylinders. In this case, since the fuel injection cylinder is set early, the torque can be increased quickly. Further, FIG. 15 shows an example of a fuel cut pattern suitable for a case where the number of cylinders in the fuel cut is reduced in the case where seven cylinders are set as one cycle corresponding to FIG.
The effect is the same as that described in.

The control procedure for executing the above-described operation will be described with reference to FIGS. 16 and 17. FIG. 16 shows a part of a control flow for determining an operation value of fuel injection including determination of fuel cut and injection, and this control flow is executed by the control unit 50 at every predetermined time. FIG. 17 shows a part of a flow of control for finally operating the fuel injection, and since the fuel injection is an operation performed in synchronization with the phase of the crankshaft, the control flow is for every predetermined crankshaft angle. Is executed by the control unit 50.

First, the operation for setting the fuel cut pattern is performed according to the control flow shown in FIG. First, the number of fuel cut cylinders is calculated as described with reference to FIG. 5 (step S201). Next, it is determined whether or not there is a change in the number of fuel cut cylinders due to a new calculation result with respect to the fuel cut pattern currently being executed (current number of fuel cut cylinders) (step S202). If there is no change in the number of fuel cut cylinders (No at step S202), there is no need to change the cylinder cut operation, so the operation is ended.

On the other hand, when the number of fuel cut cylinders is changed (Yes at step S202), it is determined whether the number of fuel cut cylinders is increased or decreased (step S).
203). If it increases (Yes at step S203), a fuel cut pattern for increasing the number of fuel cut cylinders (for example, the fuel cut pattern illustrated in FIG. 10 or 12) corresponding to the number of fuel cut cylinders is selected (step S204). ), The fuel cut pattern for reducing the number of fuel cut cylinders (for example, the fuel cut pattern illustrated in FIG. 14 or FIG. 15) corresponding to the number of fuel cut cylinders is selected. By this control flow, at a predetermined time interval with a frequency sufficient to respond to the torque operation request,
Calculate the optimal fuel cut pattern.

The control flow shown in FIG. 17 is started at a predetermined crankshaft angle, and the fuel cut pattern calculated in the control flow shown in FIG. 16 is received.
With respect to the fuel cut pattern currently being executed, it is determined whether the pattern is updated (step S301).
If the fuel cut pattern has not been updated (No at step S301), the operation based on the fuel cut pattern currently being executed may be executed as it is. Therefore, fuel is injected into the cylinder to be operated this time, or the fuel cut is performed. The operation to perform is performed (step S304). An example of this fuel injection / fuel cut operation will be described with reference to FIG. As an example of the required fuel cut pattern, FIG. 18 shows a case where two cylinders are cut.

A pattern pointer indicates which of the fuel cut patterns the operation performed at this process start corresponds to. The operation is performed according to the fuel cut or fuel injection setting indicated by the pattern pointer. When the operation is completed, the putter pointer is advanced by 1 as a delivery to the next startup process. As a result, the intended fuel cut pattern can be executed according to the number of times the fuel injection control flow is activated.

Returning to the explanation of the control flow shown in FIG. 17, if the fuel cut pattern has been updated (Yes at Step S301), a new request fuel cut pattern is read (Step S302), and The pattern pointer described with reference to FIG. 18 is reset to indicate the beginning of a new fuel cut pattern, and fuel injection or fuel cut operation is executed for the cylinder to be operated this time (step S304). By such processing, when the fuel cut pattern is updated, a new fuel cut pattern can be executed from the beginning of the pattern.

The temporal relationship between the fuel cut operation, the fuel injection amount operation, and the ignition timing operation described above will be described with reference to FIG. FIG. 19 shows the crankshaft angle in the upper part and shows the stroke of each cylinder of the 6-cylinder engine with respect to it. Here, as an example of activating the control flow shown in FIG. 17 at a predetermined crankshaft angle, an example of activating at BTDC 67 degrees is shown. That is, BTDC6 of each cylinder
The BTDC 67 is used to determine which cylinder is to be injected with fuel and at which crankshaft angle the ignition operation is performed at which crankshaft angle of 7 degrees.
Set and execute at the timing of every.

Further, this example shows an example of a cylinder injection engine. In a cylinder injection engine, fuel is directly injected into the cylinder, so fuel is injected during the intake stroke to uniformly distribute the fuel in the combustion chamber for combustion, and fuel is injected during the compression stroke to inject fuel. It is possible to selectively execute the stratified injection in which a portion of the combustion chamber is stratified and distributed to perform combustion. In this figure, both injections are entered.

The arrows extending from fuel injection and ignition from the timing of BTDC 67 degrees show the relationship between fuel injection and ignition set at the timing. That is, homogeneous injection is performed for a certain cylinder, and then the BDC 67
The operation of giving ignition is performed when the timing of the degree comes three times. In the stratified injection, ignition is applied at the timing of BTDC 67 degrees next to the injection.

On the other hand, the internal combustion engine produces an output during the expansion stroke of each cylinder. Therefore, when the operation for fuel injection is performed, the time until the effect as the output is obtained requires about 2 strokes in the case of homogeneous injection and about 1 stroke in the case of stratified injection. On the other hand, the operation of the ignition timing can obtain an effect in a time of about 0.5 stroke.

The above description is for the case where fuel injection and ignition are performed at the timings shown in the figure, and these timings take various values depending on various operating conditions of the internal combustion engine, and are not necessarily the same as those described above. It does not take the value of delay like. However, qualitatively, there is a time difference required for the response as described above. Therefore, when the fuel injection amount operation and the ignition timing operation associated with the fuel cut as described with reference to FIG. 6 are performed in each operating state with different air-fuel ratios, the responsiveness due to the operation is, for example, in the theoretical air-fuel ratio. There is a phenomenon that the ignition timing operation is early, the fuel amount operation in the lean burn is slow, and the homogeneous fuel injection in the lean burn is even slower.

On the other hand, the side that generates the torque request,
For example, on the side that controls the behavior of the vehicle, the response of torque operation of the internal combustion engine may be predicted and estimated for control. When a torque operation with different responsiveness is performed for such control, the control accuracy may deteriorate. In order to avoid this, in engine control, among a plurality of operation modes determined according to the operating state of various internal combustion engines, by operating so as to have an operation response equivalent to the operation mode with the slowest response characteristic, The responsiveness of the torque operation can be unified.

That is, in the above-described example, in order to realize the responsiveness of the fuel amount operation in the homogeneous injection having the slowest responsiveness, the operation of the fuel amount in the stratified injection is delayed by one stroke. In the operation of the ignition timing, if the operation is delayed by 1.5 strokes, the responsiveness of the torque operation can be unified. Further, as can be understood from FIG. 19, the fuel cut is one type of fuel injection operation, and the response to the required torque has the delay as described above. If such a delay cannot be ignored, it is possible to obtain the same effect as fuel cut by ignition with quick response as described above. That is, the ignition operation is not performed. As a result, an explosion does not occur even in the expansion stroke, so that it is possible to obtain the same torque as when the fuel is cut.

In such a case, the fuel which is scheduled to be burned and has been supplied to the cylinder is guided to the exhaust system without being burned.
Whether to implement this method may be determined in view of the request for torque response and the rebound caused by not burning the fuel. Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various designs can be made without departing from the spirit of the present invention described in the claims. Can be changed.

For example, in the above description, the case of a cylinder injection engine is shown as an example, but the present invention can be applied to other engine forms. Further, in the above description, the embodiment for responding to the torque request has been described, but the present invention can be applied to any other operation as long as it is an operation for the same request.

[0057]

As can be understood from the above description, the control device for an internal combustion engine according to the present invention does not cause a problem that the wall surface temperature of a specific cylinder lowers due to the fuel cut, and restarts the fuel cut cylinder. It is possible to obtain stable combustion even at times, obtain torque generation close to the intended output torque generation state of the internal combustion engine, and perform torque control with good response characteristics.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a cylinder injection internal combustion engine to which an embodiment of a control device for an internal combustion engine of the present invention is applied.

FIG. 2 is a block diagram showing an internal configuration of a control device for an internal combustion engine shown in FIG.

FIG. 3 is an explanatory diagram showing the concept of one method of engine torque control by fuel cut of the control device for the internal combustion engine of FIG. 1.

FIG. 4 is an explanatory view showing the concept of another method of engine torque control by fuel cut of the control device for the internal combustion engine of FIG. 1.

5 is a flowchart of engine torque control by fuel cut of the control device for the internal combustion engine of FIG.

6 is a graph showing the relationship between the number of fuel cut cylinders and the torque change amount / output torque of the control device for the internal combustion engine of FIG.

7A is a graph showing a relationship between ignition timing and output torque in stoichiometric air-fuel ratio combustion, and FIG. 7B is a graph showing a relationship between fuel injection amount and output torque in lean combustion.

FIG. 8 is a graph showing the relationship between the number of cylinders in one cycle, the control accuracy of torque operation by fuel cut, and the time required for one cycle.

FIG. 9 is a graph showing an output torque ratio characteristic of a 6-cylinder internal combustion engine.

10 is a table showing an example of a fuel cut pattern by the control device for the internal combustion engine of FIG. 1. FIG.

11 is a table showing a fuel cut operation by the control device for the internal combustion engine of FIG. 1. FIG.

12 is a table showing another example of the fuel cut pattern by the control device for the internal combustion engine of FIG. 1. FIG.

13 is a table showing a fuel cut operation by the control device for the internal combustion engine of FIG. 1. FIG.

FIG. 14 is a table showing another example of the fuel cut pattern by the control device for the internal combustion engine of FIG. 1.

FIG. 15 is a table showing another example of the fuel cut pattern by the control device for the internal combustion engine of FIG. 1.

16 is a flowchart showing a control flow of fuel cut pattern setting by the control device for the internal combustion engine of FIG. 1. FIG.

17 is a flowchart showing a control flow of fuel cut by the control device for the internal combustion engine of FIG. 1. FIG.

18 is an explanatory diagram showing the concept of a pattern pointer used in the control device for the internal combustion engine of FIG. 1. FIG.

FIG. 19 is a time chart showing control timing in the control device for the internal combustion engine in FIG. 1.

FIG. 20 is a table showing an example of a fuel cut pattern of a conventional device.

[Explanation of symbols]

1 engine body 2 combustion chamber 14 Fuel injector 15 Spark plug 20 fuel tank 21 Low pressure fuel pump 22 Fuel pressure regulator 23 High-pressure fuel pump 50 control unit

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 43/00 301 F02D 43/00 301B 3G301 301H F02P 5/15 F02P 9/00 304B 9/00 304 5/15 F F Terms (Reference) 3G019 AC06 BB20 DA02 GA01 GA09 GA10 GA15 LA11 3G022 AA04 CA04 DA01 DA02 GA01 GA06 GA08 GA12 GA15 3G084 BA02 BA15 BA16 CA04 DA17 EC02 FA07 FA10 FA20 FA29 FA36 FA38 3G092 AA01 BA10 BB10 CA05 GA03 CB12 EA12 FA02 CB04 CB05 CB04 CB02 CB05 HA06Z HB03Z HC08X HD05Z HE03Z HF08Z HF19Z 3G093 BA01 BA20 CA07 CB06 DA05 DA06 DA09 DA11 EA02 EA05 EA13 FB02 3G301 HA01 JA21 JA38 KA12 KA26 LB04 MA11 MA24 NC02 NE06 PA01Z PA11Z PB08Z PD02Z PE03

Claims (6)

[Claims] 1. A control device for an internal combustion engine, which performs a fuel cut on a cylinder having a predetermined ratio with respect to the total number of cylinders of an internal combustion engine having a plurality of cylinders, wherein a fuel cut execution pattern is one cycle for a number of cylinders different from the total number of cylinders. A control device for an internal combustion engine, characterized in that the fuel is cut in a predetermined fuel cut pattern during one cycle. 2. The control device for an internal combustion engine according to claim 1, wherein the fuel cut is performed with different preset fuel cut patterns when the number of cylinders of a predetermined ratio increases and when the number of cylinders decreases. . 3. The control device for an internal combustion engine according to claim 1, wherein the number of cylinders included in one cycle is one less than the total number of cylinders of the internal combustion engine. 4. The control device for an internal combustion engine according to claim 1, wherein the number of cylinders included in one cycle is one more than the total number of cylinders of the internal combustion engine. 5. A fuel injection amount correction or an ignition timing correction in accordance with a fuel cut operation is performed among a plurality of operation modes according to an operating state of an internal combustion engine so that a required torque can be obtained.
The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the control device is operated so as to have an operation responsiveness equivalent to that of an operation mode having the slowest response characteristic. 6. The fuel cut operation is replaced with an operation that does not perform ignition, and the fuel cut operation is performed.
A control device for an internal combustion engine according to the item.