JPH07158482A - Fuel injection control device for multiple cylinder internal combustion engine - Google Patents

Abstract

PURPOSE:To attempt compatibility between starting property and exhaust purifying property in a multiple cylinder internal combustion engine by selecting and deciding sequential injection and simultaneous injection on the basis of a crank angle position at the time of stopping according to the high and low degrees of an engine temperature when the engine is started. CONSTITUTION:In a control circuit 6, each fuel injection valve 7 for each cylinder is controlled on the basis of each signal which is detected from each sensor 1 to 5 for detecting operating condition of a multiple cylinder internal combustion engine. In the control circuit 6, a crank angle position is detected by a means 62 on the basis of a reference signal which is outputted from the crank angle sensor 1, and also the crank angle position at the time of engine stopping is memorized by a means 63. Engine starting is judged by a means 65 on the basis of an on-signal which is outputted from the engine key switch 3. A water temperature is judged by a means 66 on the basis of a signal which is outputted from the water temperature sensor 2. Sequential injection and simultaneous injection are selected and decided by a means 67 on the basis of the crank angle position at the time of stopping according to the high and low degrees of the engine temperature at the time of engine starting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device at the time of starting in a multi-cylinder internal combustion engine, and more particularly, by switching the fuel injection system at the time of starting to ensure startability and to improve exhaust purification performance. Regarding the technology

[0002]

In an electronically controlled fuel injection device for a multi-cylinder internal combustion engine, a signal that is output at a predetermined crank angle position of a specific cylinder and is capable of discriminating the cylinder.
(So-called cylinder determination signal) to determine the specific cylinder, other cylinders perform the cylinder determination by counting the number of times the reference signal is output at each predetermined crank angle position,
Fuel injection is controlled in the corresponding cylinder.

In this case, at the time of starting (at the time of cranking), the cylinders cannot be discriminated until the cylinder discrimination signal of the specific cylinder is input, so that the fuel injection control is performed unconditionally for all the cylinders simultaneously. Was common. However, in such a method in which all cylinders are simultaneously injected unconditionally, a plurality of fuel injections are performed for each combustion stroke of each cylinder, so a single fuel injection ensures sufficiently good startability. In such a case, there is a problem that the fuel supply becomes excessive and the exhaust gas purification performance deteriorates.

On the other hand, there is a system in which the crank angle position state of each cylinder is stored when the engine is stopped, and the crank angle position state of each cylinder at the time of starting can be detected based on the stored data (Japanese Patent Laid-Open No. 2000-242242). (See Sho 60-240875). In this engine as well, it is disclosed that fuel is simultaneously injected into all cylinders at the time of starting, but so-called fuel injection is performed once per combustion stroke for each cylinder according to the combustion stroke sequence from the beginning of the start based on stored data. It is possible to perform sequential injection control.

However, performing unconditional sequential injection control at the time of starting causes the following problems in terms of startability. When starting at an extremely low temperature (for example, a low temperature of -10 ° C or less), most of the supplied fuel remains in the intake port as a wall flow, and flows into the combustion chamber in time for the combustion stroke corresponding to the injection timing. The amount to be used is extremely small, and it will take a certain amount of time before the first explosion. That is, startability is significantly deteriorated.

The present invention has been made in view of such a conventional situation. By detecting the crank angle position state of each cylinder at the time of starting, the fuel injection system is switched according to the temperature state of the engine. An object of the present invention is to provide a fuel injection control device for a multi-cylinder internal combustion engine that achieves both a starting performance and an exhaust purification performance.

[0007]

Therefore, a fuel injection control device for a multi-cylinder internal combustion engine according to the present invention, as shown in FIG. 1, is a fuel injection control for a multi-cylinder internal combustion engine having a fuel injection valve for each cylinder. In the apparatus, a reference signal is output at a predetermined crank angle position of each cylinder, and the reference signal of a specific cylinder is based on the reference signal output means formed so that the cylinder can be discriminated. Crank angle position state storage means for storing the crank angle position state of each cylinder when the engine is stopped, sequential injection control means for injecting fuel once for each combustion stroke according to the combustion stroke sequence for each cylinder, and for each cylinder. A simultaneous injection control means for simultaneously injecting fuel into a plurality of cylinders so that a plurality of fuel injections are performed per fuel stroke; and a start determination means for determining a start state of the engine,
Engine temperature detecting means for detecting the temperature state of the engine, and when the engine temperature at the time of starting detected by the engine temperature detecting means is above a predetermined level, each detected by the crank angle position state detecting means during stop. Sequential injection is performed by the sequential injection control means based on the crank angle position state of the cylinder, and simultaneous injection is performed by the simultaneous injection control means when the engine temperature at startup is a low temperature state below the predetermined value. And an injection method switching means for switching the fuel injection method.

[0008]

The crank angle position state of each cylinder can be detected by the reference signal of the specific cylinder output by the reference signal output means and the reference signal of the other cylinder. The crank angle position state of each cylinder detected at the time of stop is stored.

Then, the crank angle position state of each cylinder at the time of starting is detected based on the crank angle position state of each cylinder stored at the time of stop and the reference signal of each cylinder newly input. On the other hand, when the engine temperature state at the time of starting is detected by the engine temperature detecting means and the engine temperature is room temperature or higher than a predetermined temperature, the sequential injection control means determines the crank angle position state of each cylinder at the time of starting. Fuel injection is performed by a sequential injection method. In such a temperature state, good vaporization of the fuel is performed, so that good startability can be ensured, and the amount of fuel injection can be suppressed to the required minimum amount, so that exhaust purification performance is also satisfied.

Further, when the engine temperature at the time of starting is lower than a predetermined temperature, the simultaneous injection control means simultaneously injects a plurality of fuels into a plurality of cylinders per combustion stroke. As a result, surplus fuel for filling the wall flow can be injected in advance, and the necessary amount of fuel to be injected thereafter can reach the combustion chamber in time for the combustion stroke. Startability can be secured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of a fuel injection control device for a multi-cylinder internal combustion engine according to the present invention. In the figure, a crank angle sensor 1 is provided on a camshaft or the like that rotates in synchronization with engine rotation of a 4-cycle 4-cylinder engine. The crank angle sensor 1 outputs a reference signal at a predetermined crank angle position of each cylinder (outputs at every crank angle of 180 °). Where specific cylinder
The reference signal of (for example, the first cylinder) has a larger pulse width than the other reference signals, so that it can be identified as the specific cylinder. Therefore, the crank angle sensor 1 constitutes a reference signal output means. The crank angle sensor 1 also outputs a unit angle signal for each unit crank angle (for example, 1 °).

Then, in addition to the reference signal and the unit angle signal from the crank angle sensor 1, an engine cooling water temperature signal detected by a water temperature sensor 2 as an engine temperature detecting means,
The ON / OFF signal of the engine key switch 3, the intake air flow rate Q signal detected by the air flow meter 4, the ON / OFF signal of the starter switch 5, and the like are supplied to the control circuit 6.
Is output to.

The control circuit 6 performs calculation / processing / determination by the following means based on the various detection signals, and drives the fuel injection valve 7 provided in each cylinder according to the determined fuel injection method to drive the fuel. Injection control is performed. The outline of the function of each means will be described below. The engine speed detecting means 61 is
By calculating the number of inputs of the unit angle signal per unit time,
The engine speed N proportional to this is calculated and detected. Alternatively, the engine rotation speed N may be calculated as a value inversely proportional to the period between the inputs of the respective reference signals.

The crank angle position detecting means 62 receives the reference signal and the unit angle signal and detects the crank angle position of each cylinder. Here, not only is the crank angle position detected as the piston position, but intake-compression-explosion (combustion)
-It can be detected including the crank angle position in any stroke of the exhaust gas. Specifically, it is possible to know the stroke of the cylinder by inputting the reference signal of the specific cylinder, and to know the strokes of the other cylinders by inputting the reference signal thereafter.

The stop crank angle position detection state means 63 is
Crank angle position state of each cylinder detected by the crank angle position detection means 62 when the engine is stopped (including stroke)
Memorize The basic fuel injection amount calculation means 64 is an amount proportional to the amount of air taken into the cylinder based on the engine rotation speed N calculated by the engine rotation speed detection means 61 and the intake air flow rate Q detected by the air flow meter 4. The basic fuel injection amount T _P is calculated as

The start determination means 65 determines the start by inputting the ON signal of the engine key switch 3, and immediately after the start determination, the water temperature determination means 66 determines whether or not the temperature is extremely low based on the signal from the water temperature sensor 2. The determination information is sent to the injection method / injection order determining means 67. Injection method / injection sequence determination means
67 determines either the sequential injection method or the simultaneous injection method according to the water temperature, and also determines the injection order to each cylinder corresponding to the determined injection method.

The injection pulse width calculating means 68 calculates the injection pulse width T _i finally obtained by correcting the basic fuel injection amount T _P with the cooling water temperature or the like,
The injection pulse signal is output to the injection valve driving means 69. The injection valve driving means 69 controls the driving transistor 70 connected to the fuel injection valve 7 of the cylinder corresponding to the combustion timing according to the injection method / injection order determined by the injection method / injection order determining means 67 to inject the injection pulse width. By energizing for a time corresponding to, the fuel injection valve 7 is driven to open, and a set amount of fuel is injected and supplied.

The fuel injection control at the time of starting will be described in detail with reference to the flow chart shown in FIG. This routine is started at the same time when the starter switch 5 is turned on, that is, the cranking is started. In step (denoted as S in the figure. The same applies hereinafter) 1, the value of the cylinder counter CYLCNT stored when the engine was stopped last time and the crank angle θ of the cylinder corresponding to this value are read by another routine described later. This makes it possible to know the crank angle position state of each cylinder when the engine is stopped.

In step 2, it is determined whether the cooling water temperature T detected by the water temperature sensor 2 is equal to or lower than a predetermined value T ₀ (for example, -10 ° C) set as an extremely low temperature. Then, when the temperature is extremely low, which is equal to or lower than the predetermined value T ₀ , the process proceeds to step 3 and thereafter, and the fuel injection is performed by the simultaneous injection method. First, in step 3, it is determined whether the value of the cylinder counter CYLCNT read in step 1 is 0 or 2.

If it is 0 or 2, the process proceeds to step 4 and fuel injection is performed simultaneously for all cylinders at a predetermined fuel injection timing. This embodiment is a four-cycle four-cylinder engine, and therefore fuel injection is performed once per one revolution of the engine, and twice per cylinder per cycle. Here, the fuel injection timing is detected while measuring the current crank angle by counting and adding the unit angle signals input from the crank angle sensor 1 with the crank angle θ read in step 1 as a reference. It should be noted that if the fuel injection timing has already passed, the process may proceed to step 5 as it is, but it is also possible to make an unconditional injection at the first time by emphasizing the injection delay.

Next, in step 5, the crank angle sensor 1
Waits for a new reference signal to be input from, and when the reference signal is input, in step 6, the reference signal is changed to the specific cylinder.
It is determined whether the signal corresponds to (first cylinder in this embodiment). If it is determined that the cylinder is a specific cylinder, the process proceeds to step 7, and the value of the cylinder counter CYLCNT is set to a corresponding value, here, 0, and if it is determined that the cylinder is not the specific cylinder, the process proceeds to step 8. , Step 9 after incrementing the cylinder counter CYLCNT
Go to.

In step 9, the starter switch 4 is turned off.
It is determined whether or not it remains N, and if it remains ON,
Returning to step 3, fuel injection by the simultaneous injection method is repeated. When the start by the simultaneous injection is completed and the starter switch 4 is turned off, the process proceeds from step 9 to step 10 and subsequent steps, and the fuel injection is switched to the sequential injection system.

When the cooling water temperature T exceeds the predetermined value T ₀ in step 2, the process proceeds from step 10 to step 10 and thereafter, and fuel injection is performed by the sequential injection method. First, in step 10, the cylinder counter CYLC
The cylinder to be next injected with fuel is determined according to the value of NT.
Specifically, in the case of the present embodiment, CYL is assumed that the combustion stroke sequence is the first cylinder → the third cylinder → the fourth cylinder → the second cylinder.
Since the fuel injection cylinders corresponding to CNT = 0, 1, 2, and 3 are the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder, respectively, go to any of steps 11A to 11D corresponding to each value. After advancing, the fuel injection is performed from the fuel injection valve 7 of the corresponding cylinder after waiting a predetermined injection timing. In such a sequential injection method, fuel injection is sequentially performed in the intake stroke of each cylinder. That is, fuel injection is sequentially performed for each cylinder once per cycle (one combustion stroke).

Next, in step 12, the input of a new reference signal is awaited. When the reference signal is input, it is determined in step 13 whether or not the reference signal is a signal corresponding to a specific cylinder. If there is, the process proceeds to step 13 and the value of the cylinder counter CYLCNT is set to 0. If it is not a specific cylinder, the process proceeds to step 14 and the cylinder counter CYLCNT.
After returning to step 10, the sequential injection control is repeated until the operation is stopped.

Next, a routine for storing the crank angle position state of each cylinder when the operation is stopped will be described with reference to FIG.
In step 21, it is determined whether the rotation of the engine has completely stopped. This may be performed by observing a lapse of a predetermined time after the key switch 3 is turned off or by detecting the stop of the input of the unit angle signal from the crank angle sensor 1.

After confirming that the engine has completely stopped, the routine proceeds to step 22, where the current cylinder counter CY
The value of LCNT and the corresponding crank angle θ of the cylinder are stored in the RAM with a backup function. This stored value is read at the start of starting as described above. With such a configuration, by switching between the simultaneous injection method and the sequential injection method according to the water temperature at the time of start-up, while ensuring the startability at extremely low temperatures at which fuel is difficult to vaporize, it is only necessary to start at normal temperature and high temperature. The fuel can be supplied to maintain good exhaust gas purification performance. Figure 5
Shows the experimental results comparing the time required from the start to the complete explosion in the sequential injection method and the simultaneous injection method with the cooling water temperature as the horizontal axis parameter.

As shown in the figure, as the temperature becomes extremely low, the simultaneous injection method has the result that the start is completed in a shorter time.
The main reason for this is that if the sequential injection method is used immediately after the start of injection, most of the initial injected fuel remains as a wall flow in the intake port, and it is not possible to expect fuel to reach the combustion chamber. It can be interpreted that the tendency becomes stronger as the temperature shifts to lower temperatures.
(This is considered to be a phenomenon caused by changes in the properties of fuel volatility and viscosity). On the other hand, when the simultaneous injection method is used at low temperature, the time required until complete explosion shows a significant improvement effect. This factor is a paradox of the above contents, but when considering, for example, a cylinder whose intake stroke (requested fuel injection point) is later immediately after the start of start, unnecessary fuel injection is performed at the moment of start, Before the injected injection amount T _i acts (synchronously with the intake stroke),
Excess fuel will be present in the intake port. That is, the surplus fuel acts as a flow on the inner wall of the intake port, and the fuel corresponding to the next-related normal injection pulse width is added to the wall flow to be supplied to the intake port. It appears as an effect of accelerating the fuel arrival time to the chamber, and as a result, it can be a major factor of improving the startability as compared with the case of sequential injection.

In other words, when performing sequential injection from the beginning, the fuel is supplied from the first in synchronism with the intake stroke, but the number of injections 1 to 2 acts as a wall flow,
It can be said that the arrival of fuel in the fuel chamber is delayed compared to the simultaneous injection method. FIG. 6 shows the HC emission amount at the time of starting, which was measured when the experimental data shown in FIG. 5 was obtained. However, since the starting time can be shortened, the HC injection amount in the case of the simultaneous injection method is higher.
The C emission level is low, and compared to the sequential injection method,
The reproducibility of the discharge level is also stable and the effect of the present invention can be seen.

On the other hand, in FIG. 6, the room temperature starting region is the starting property.
No significant difference was found in the time required to complete the explosion. It is considered that this is because the amount of the wall flow is not so large in view of the volatility and viscosity of the fuel described above, and the fuel reaches the combustion chamber relatively easily. Therefore, the simultaneous injection method that supplies unnecessary fuel in the normal temperature starting region is not appropriate from the viewpoint of exhaust performance (especially HC reduction). A sequential injection method in which only a sufficient amount of fuel is injected is preferable. That is, it is possible to understand the features of the present invention in which the sequential injection method is used at room temperature or higher and the simultaneous injection method is used at low temperature.

In the above-described embodiment of the present invention, the simultaneous injection system is a system in which all cylinders are simultaneously injected once for each revolution of the engine. However, the injection is performed twice per revolution of the engine, that is, in the sequential injection system. A so-called group injection method in which two cylinders are simultaneously injected at each time may be adopted, and two injection timings of each cylinder may be made equal (injection in the same stroke), and one injection may be performed normally.

Further, in the above-described embodiment, the value of θ obtained by counting the unit crank angle is stored at the same time as the cylinder counter CYLCNT at the time of stop, so that the fuel injection can be performed after the start is started and before the reference signal is input. However, for simplicity, only the value of the cylinder counter CYLCNT may be stored, and the fuel injection may be started after the reference signal is input once after the start. However, in this method, when the reference signal is not injected first in the all-cylinder simultaneous injection method (in the case of the embodiment, the value of the cylinder counter CYLCNT is 1, 3).
In this case, since the injection is delayed, it is possible to adopt the group injection described above, or to perform simultaneous injection for all cylinders in accordance with the reference signal input first.

[0032]

As described above, according to the present invention, the crank angle position state when the engine is stopped is stored,
Based on the temperature condition of the engine at the time of starting, it is configured to switch to the sequential injection method at room temperature or higher and the simultaneous injection method at low temperature below a predetermined value, so that it is possible to ensure good startability at low temperature and unnecessary fuel at room temperature or higher. The injection can be stopped and the exhaust purification performance can be favorably maintained, and both startability and exhaust purification performance can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing the configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing a fuel injection control routine of the above embodiment.

FIG. 4 is a flow chart showing a crank angle position state storage routine when the engine is stopped.

FIG. 5 is a diagram showing the relationship between the water temperature and the required start time.

FIG. 6 is a graph showing the relationship between the HC emission concentration and the elapsed time after starting.

[Explanation of symbols]

 1 Crank angle sensor 2 Water temperature sensor 3 Engine key switch 5 Starter switch 6 Control circuit 7 Fuel injection valve 63 Crank angle position state storage means 65 Stop determination means 66 Water temperature determination means 67 Injection method / injection sequence switching means

Claims (1)

[Claims] 1. A fuel injection control device for a multi-cylinder internal combustion engine having a fuel injection valve for each cylinder, wherein a reference signal is output at a predetermined crank angle position of each cylinder, and the reference signal of a specific cylinder is the reference signal. Reference signal output means formed so that the cylinder can be discriminated, stop crank angle position state storage means for storing the crank angle position state of each cylinder when the engine is stopped based on the reference signal, and combustion stroke for each cylinder A sequential injection control means for injecting fuel once per combustion stroke in accordance with the order; a simultaneous injection control means for simultaneously injecting fuel into a plurality of cylinders so that a plurality of fuel injections are performed per fuel stroke for each cylinder; Starting determination means for determining the starting state of the engine, engine temperature detection means for detecting the temperature state of the engine, and engine temperature at the time of startup detected by the engine temperature detection means are predetermined. In the above state, based on the crank angle position state of each cylinder detected by the stop crank angle position state detection means, the sequential injection control means causes the sequential injection to be performed, and the engine temperature at the start is Fuel injection for a multi-cylinder internal combustion engine, characterized in that when the temperature is lower than a predetermined temperature, the injection method switching means switches the fuel injection method so that the simultaneous injection is performed by the simultaneous injection control means. Control device.