JP3047633B2 - Fuel injection device for two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device used for a two-cycle engine.

[0002]

2. Description of the Related Art Recently, a two-stroke engine in which a fuel injection device is controlled by a computer to maintain an optimum operating state has been widely used.

[0003] A fuel injection device is an injector (fuel injection valve) attached to an intake passage of an engine, a fuel pump for supplying fuel to the injector at a constant pressure, and controls the injector according to operating conditions and surrounding environmental conditions. And a control device. The injector includes, for example, a Neildle valve and an electromagnetic coil for driving the valve, and the valve is opened only while a drive signal is applied to the coil. Since the pressure (fuel pressure) of the fuel supplied from the fuel pump to the injector is constant, the amount of injected fuel is proportional to the time during which the valve of the injector is opened, that is, the time during which the drive signal is given. A fuel injection pulse having a rectangular wave shape is generally used as a drive signal, and the pulse width (injection time) is controlled to control the fuel injection amount.

A fuel injection device controlled by a computer includes, for example, an engine speed N calculated from an interval of generation of a pulse signal obtained from a signal generator mounted on the engine and a throttle opening detected by a throttle opening sensor. The basic fuel injection time setting means for setting the basic fuel injection time Tp using the degree α as a parameter, and correcting the basic fuel injection time Tp according to various control conditions such as cooling water temperature, atmospheric pressure, intake air temperature, etc. A fuel injection time setting means for setting the injection time Ti, and injector driving means for giving a fuel injection pulse Pi having a pulse width equal to the fuel injection time Ti set by the fuel injection time setting means to the injector.

The basic fuel injection time setting means uses a three-dimensional map which gives a relationship among the engine speed, the throttle opening, and the basic fuel injection time (the fuel injection time which is the base of calculation), and detects the detected fuel. By searching the three-dimensional map using the engine speed N and the throttle opening α as parameters, the basic fuel injection time Ti at each speed is obtained from the map directly or by an interpolation method.

In the fuel injection time setting means, the atmospheric pressure,
An operation for correcting the basic fuel injection time Tp in accordance with various control conditions such as the intake air temperature is performed to obtain an actual fuel injection time at each rotation speed. The injector driving means includes:
At a predetermined injection timing determined by measuring a predetermined number of clock pulses (depending on the number of revolutions) from the time when the signal generator generates a specific signal, the fuel injection time Ti
Is given to the injector.

In a two-cycle engine, the air-fuel mixture is supplied to a cylinder through a crankcase.
The air-fuel ratio is affected by the temperature of the crankcase. In particular, in engines mounted on vehicles used in cold regions, such as snowmobiles, the temperature of the crankcase during startup is-
Since the temperature drops to an extremely low temperature of 30 ° C. or less, the range of change in the temperature of the crankcase becomes very large. Therefore, if the fuel injection amount is controlled in accordance with the temperature of the cooling water, etc. ignoring the temperature of the crankcase, the air-fuel ratio cannot be controlled accurately. Inevitably gets worse.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 3-175121, a fuel injection device has been proposed in which the amount of fuel injected is controlled in accordance with the temperature of the crankcase. In this fuel injection device, the low-speed basic fuel injection pulse width set based on the crankcase temperature is corrected by a correction coefficient that corrects the pulse width to decrease with time. In addition to setting the pulse width (injection time during low rotation), the basic fuel injection pulse width during normal operation (basic fuel injection time during steady operation) set according to the throttle opening and engine speed is controlled by various control conditions. The fuel injection pulse width at the time of steady operation is corrected and the fuel injection pulse width at the time of low rotation is compared with the fuel injection pulse width at the time of steady operation, and the larger pulse width is supplied to the injector. The pulse width is used.

In this fuel injection device, the low-speed fuel injection pulse width at the start of the engine is larger than the normal operation fuel injection pulse width. Therefore, at the time of starting, a fuel injection pulse having a pulse width equal to the low-speed fuel injection pulse width is supplied to the injector. As a result, the amount of fuel supplied at the time of starting is increased, and starting of the engine is facilitated. After a lapse of time after the start, the low-speed fuel injection pulse width becomes smaller, so that the steady-state fuel injection pulse width eventually becomes larger than the low-speed fuel injection pulse width. Therefore a certain amount of time elapses after startup (when the warm-up operation is completed), equal fuel injection pulse when the fuel injection pulse width steady operation is to be supplied to the injector, the process proceeds to the control during the steady operation.

[0010]

In the above conventional fuel injection system, the basic fuel injection pulse width at the time of low rotation is determined only by the temperature of the crankcase on the assumption that the accelerator is not operated at the time of starting and warm-up operation. Therefore, during the warm-up operation in which the low-speed fuel injection pulse width is larger than the steady-state fuel injection pulse width, the fuel injection width is set irrespective of the air intake amount.

For this reason, when the accelerator of the engine is operated at the time of engine start and warm-up operation, and the amount of air intake changes, the air-fuel ratio deviates from an appropriate value, and the engine fails to start or the engine rotation becomes unstable. As a result, there is a problem that an engine stall occurs.

An object of the present invention is to make it possible to set the fuel injection time in consideration of the amount of air intake even at a low rotation, thereby improving the startability of the engine and reducing the rotation at the low rotation. It is an object of the present invention to provide a fuel injection device for a two-cycle engine, which is capable of performing a stable and smooth operation.

[0013]

According to the present invention, as shown in FIG. 1 showing an embodiment of the present invention, a basic fuel injection time Tp is set by using a rotation speed N of a two-cycle engine and a throttle opening α as parameters. Basic fuel injection time setting means 1
And a fuel injection time setting means 2 for correcting the basic fuel injection time Tp according to various conditions to set the fuel injection time Ti.
And a fuel injection pulse Pi having a pulse width equal to the fuel injection time Ti set by the fuel injection time setting means 2.
And a fuel injection device for a two-stroke engine provided with an injector driving means 4 for supplying the fuel to the injector 3.

In the present invention, in order to achieve the above object, a basic injection time increment at low rotation Tfi corresponding to an increase in fuel injection time at low rotation is set according to the rotational speed N and the throttle opening α. The low-rotation basic injection time increment setting means 5 and the low-rotation basic injection time increment Tfi are multiplied by a predetermined correction coefficient obtained by using the engine crankcase temperature Tcc and the elapsed time t as parameters.
A low-rotational injection time increment setting means 6 is provided for obtaining a low-rotational injection time increment TiL whose value decreases as the temperature of the engine crankcase increases and decreases with time.

The fuel injection time setting means 2 further corrects the injection time TP + TiL obtained by adding the low-rotation time injection time increment TiL to the basic fuel injection time TP in accordance with various conditions to set the fuel injection time Ti. Calculate.

The starting point of the elapsed time t may be a fixed time. For example, the time when the first fuel injection pulse is output from the injector driving means after the start operation of the engine is performed can be set as the starting point of the elapsed time. In this case, the low-rotation-time injection time increment setting means 6 includes a low-rotation-time crankcase temperature correction coefficient setting means 7 for setting the low-rotation-time crankcase temperature correction coefficient KLc using the engine crankcase temperature Tcc as a parameter. Revolution N
Alternatively, duration setting means 8 for setting the duration Tcon of the injection amount increase control at low rotation using the throttle opening α and the crankcase temperature Tcc as parameters, and the time when the first fuel injection pulse is output from the injector driving means. The time correction coefficient Kt = 1− (t / Tco) is obtained from the elapsed time t measured by measuring the elapsed time t from
n), and a calculation Tfi × KLc × for multiplying the low rotation basic injection time increment Tfi by the low rotation crankcase temperature correction coefficient KLc and the time correction coefficient Kt.
Kt is performed, and the calculation result is added to the injection time increment TiL at low rotation.
And the low rotation time injection time increment calculating means 10.

The time at which the ignition spark first flew to the engine may be used as the starting point of the elapsed time t, or the time at which the starter of the engine is started may be used as the starting point of the elapsed time.

In the present invention, a steady-state crankcase temperature correction coefficient setting means 11 for setting a steady-state crankcase temperature correction coefficient Kcc using the engine crankcase temperature Tcc as a parameter, and an atmospheric pressure sensor for detecting the crankcase temperature correction coefficient. Pressure correction coefficient setting means 12 for setting an air pressure correction coefficient Kap using the measured atmospheric pressure as a parameter, and intake temperature correction coefficient setting means for setting an intake temperature correction coefficient Kar using an engine intake temperature Tar detected by an intake temperature sensor as a parameter. 13, the fuel injection time setting means 2 may calculate (Tp + TiL) .times.Kar.times.Kcc.times.Kap, and set the calculation result as the fuel injection time Ti.

The power supply voltage VB of the injector driving means
And the injection time correction amount T according to the detected power supply voltage.
The fuel injection time setting means 2 further comprises (Tp + TiL) × Kar.
The calculation of × Kcc × Kap + Ts may be performed, and the calculation result may be used as the fuel injection time Ti.

The injection time correction amount setting means 14 may set the injection time correction amount Ts using the engine speed as a parameter.

[0021]

As described above, the crankcase temperature Tcc and the elapsed time t are determined by using the crankcase temperature Tcc and the elapsed time t in the low-rotation basic injection time increment Tfi set in accordance with the engine speed N and the throttle opening α. By multiplying by the correction coefficient of
The low-speed injection time increment TiL, which decreases as the crankcase temperature increases and decreases with time, is calculated.
If the injection time TP + TiL is obtained by adding iL to the basic fuel injection time TP, and the injection time is further corrected in accordance with various conditions to calculate the fuel injection time Ti, the fuel injection at the time of low rotation is performed. The time is also based on the throttle opening (air intake amount).

Note that the basic fuel injection time Tp at low rotation is
Indicates the basic fuel injection, although the throttle opening is reflected
Injection during low rotation, reflecting throttle opening only in time
If the throttle opening is not reflected in the time increment
Is the throttle opening when the accelerator is operated during warm-up operation.
When the air pressure changes, the air
Change the increase in fuel injection amount according to the change in inflow amount
Because the fuel injection amount is
The air-fuel ratio of the mixture is outside the appropriate range
As a result, the rotation of the engine may become unstable.

On the other hand, as in the present invention, the basic fuel injection
In addition to setting the firing time according to the throttle opening,
Throttle opening is also used to increase the basic fuel injection time at low rotations
Is set in accordance with the
Is operated to change the inflow of air,
By properly changing the fuel injection amount, the air-fuel ratio of the air-fuel mixture
It can be kept in an appropriate range.

[0024] As of this, according to the present invention, involved in combustion
Air-fuel ratio of the mixture can be kept always appropriate range that
So it can only improve the startability of the engine
The accelerator is operated during warm-up operation, and
Even when the amount changes, the rotation of the engine can be stabilized.

Further, since the injection time increment TiL at the time of low rotation decreases as the crankcase temperature rises and the time elapses, the control is shifted to the control in the steady operation when a predetermined time elapses after the start. Since the increase in the injection time at low rotation decreases with an increase in the temperature of the crankcase, when the temperature of the crankcase is low, the time (warm-up operation time) required to shift to the control during the steady operation increases. On the other hand, when the temperature of the crankcase is high, the time required to shift to the control during the steady operation is reduced. Therefore, the warm-up operation can be performed for an appropriate time according to the temperature of the crankcase, and wasteful fuel consumption can be prevented.

[0026]

FIG. 1 shows an overall configuration of an embodiment of the present invention. In FIG. 1, reference numeral 20 denotes a crankcase temperature sensor attached to a crankcase of a two-stroke engine. And outputs an electric signal proportional to the detected temperature Tcc.

Reference numeral 21 denotes a throttle opening sensor for detecting an opening α of a throttle valve provided in an intake manifold connected to an intake port of the engine. This sensor comprises, for example, a potentiometer provided so as to be linked with the rotational movement of the throttle valve, and outputs an electric signal proportional to the throttle opening α.

Reference numeral 22 denotes an atmospheric pressure sensor for detecting the atmospheric pressure Ap, and reference numeral 23 denotes an intake air temperature sensor for detecting the temperature (intake air temperature) Tar of the air flowing into the intake manifold. The intake air temperature sensor 23 is provided at an appropriate position on the upstream side of the intake manifold,
For example, it is attached to an appropriate location between the intake manifold and the air cleaner, and outputs an electric signal proportional to the intake air temperature Tar.

The outputs of the crankcase temperature sensor 20, the throttle opening sensor 21, the atmospheric pressure sensor 22, and the intake air temperature sensor 23 are converted into digital signals by an A / D converter and input to the CPU of the microcomputer.
Stored in RAM.

The injector 3 is mounted so as to inject fuel into a space downstream of the throttle valve in the intake manifold.

In FIG. 1, reference numeral 24 denotes engine speed detecting means for detecting the engine speed N. The engine speed detecting means calculates the engine speed from the output of a signal generator attached to the engine. The signal generator includes, for example, a rotor formed by forming a reluctor (a protrusion or a recess extending in the circumferential direction) on the outer periphery of a flywheel attached to an engine, and an electromagnetic pickup opposed to the rotation. When the reactor starts to oppose the magnetic pole of the electromagnetic pickup and ends, the magnetic flux changes in the electromagnetic pickup, and the electromagnetic pickup generates pulse-like signals (rotation pulses) Vp1 and Vp2 having different polarities. . The engine speed detecting means 24 measures the time Tpd from the generation of the signal Vp1 to the generation of the signal Vp2 (the time required for the reluctor to pass through the electromagnetic pickup), and measures the measured time Tpd and the pole of the reluctor. From the arc angle θ, the engine speed N is calculated by the following equation.

N = θ / (6 × Tpd) (1) The engine speed detecting means 24 is realized by a microcomputer.

The basic fuel injection time setting means 1 searches the basic fuel injection time map 1a using the throttle opening α detected by the throttle opening sensor 21 and the rotation speed N detected by the engine speed detection means 24 as parameters. Then, a basic fuel injection time Tp corresponding to the throttle opening α and the rotational speed N [rpm] is obtained directly or by an interpolation method from the map. The basic fuel injection time Tp is a base time for the calculation of the fuel injection time during steady-state operation. The basic fuel injection time multiplied by a predetermined correction coefficient or added with the correction time is the time during steady-state operation. Fuel injection time.

The basic fuel injection time map is a three-dimensional map that gives a relationship between the throttle opening α and the number of revolutions N and the basic fuel injection time Tp. Data defining the map is obtained by experiments for each engine. And stored in the ROM of the microcomputer.

The low-rotation basic injection time increment setting means 5 comprises:
Using the engine speed N and the throttle opening α as parameters, the basic injection time increment map 5a at low rotation is searched, and the throttle opening α and the rotation speed N [rpm] are directly or interpolated from the map 5a. A corresponding low-rotation basic injection time increment Tfi is determined. This map 5a shows the rotation speed N, the throttle opening α, and the basic injection time increment T at low rotation.
The data defining the map 5a in a three-dimensional map giving a relationship with fi is obtained in advance by experiments or the like. Data defining this map 5a is stored in the ROM of the computer.

The low-speed basic injection time increment Tfi is an amount serving as a basis for calculating the increment of the fuel injection time when the engine is low, and takes a smaller value as the engine speed increases. The relationship between the basic injection time increment Tfi during low rotation and the throttle opening is determined by the amount of fuel adhering to the inner wall of the intake system,
It depends on the load characteristics of the engine. The relationship between the basic injection time increment Tfi during low rotation and the throttle opening is not necessarily a simple relationship such as increasing or decreasing as the throttle opening increases or decreases. Depending on the characteristics of the engine, the throttle opening may be different. In a range where the throttle opening increases up to a certain angle θs, Tfi may decrease with an increase in the throttle opening, and in a range where the throttle opening increases beyond a certain angle θs, Tfi may increase with an increase in the throttle opening. . The increment of the fuel injection time at the time of low rotation is obtained by multiplying the basic injection time increment at low rotation Tfi by a predetermined correction coefficient.

The low-speed injection time increment setting means 6 includes a low-speed crankcase temperature correction coefficient setting means 7, a duration setting means 8, a time correction coefficient setting means 9, and a low-speed injection time increment calculation means. It consists of ten.

The low-speed crankcase temperature correction coefficient setting means 7 sets the low-speed crankcase temperature correction coefficient KLc using the engine crankcase temperature Tcc as a parameter.
Set. The setting of the correction coefficient KLc may be based on a map created based on data obtained through experiments or the like, or may be performed using an arithmetic expression obtained from experimental results or the like.

The duration setting means 8 searches the duration map 8a using the number of revolutions N and the crankcase temperature Tcc as parameters, and directly or by interpolation from the map 8a performs the control for increasing the injection amount at low revolutions. The duration time Tcon is obtained. The duration map 8a is a three-dimensional map that gives a relationship between the number of revolutions N, the crankcase temperature Tcc, and the duration Tcon. Data defining this map (determined in advance by experiments) is stored in the ROM of the computer. Have been. The duration Tcon has a smaller value as the crankcase temperature Tcc is higher, and has a smaller value as the rotation speed N is higher. That is, the higher the crankcase temperature during the warm-up operation, the shorter the duration (time of the warm-up operation) Tcon,
The higher the engine speed during warm-up operation, the longer the duration T
shorten con.

When supplying fuel by injecting fuel from the injector into the intake system of the engine, the amount of fuel adhering to the inner wall of the intake system (in this example, the inner wall of the intake manifold) changes depending on the amount of intake air. The amount of fuel taken into the combustion chamber is affected by the amount of fuel attached to the inner wall of the intake system. That is, when the amount of intake air is small, a large amount of fuel adheres to the inner wall of the intake system (in this example, the inner wall of the intake manifold), but when the amount of intake air increases, the amount of fuel that adheres to the inner wall of the intake system decreases. At the same time, a part of the fuel that has adhered to the inner wall up to that time becomes droplets and is taken into the combustion chamber, so that the amount of fuel taken into the combustion chamber increases as the amount of intake air increases. For this reason, in the present embodiment, the duration Tcon of the injection amount increase control is shortened as the rotational speed increases.

In the present embodiment, the engine speed N and the crankcase temperature Tcc are used as parameters to set the duration T
Although con is set, the duration Tcon may be set using the throttle opening α and the crankcase temperature Tcc as parameters. That is, the longer the crankcase temperature is, the shorter the duration (time of warm-up operation) Tcon is, and the larger the throttle opening α is, the longer the duration Tcon is.
Shorten.

The time correction coefficient setting means 9 includes a time measuring means for measuring an elapsed time t from the time when the first fuel injection pulse is output from the injector driving means 4, an elapsed time t measured by the time measuring means, and a continuation time. And a calculating means for calculating a time correction coefficient Kt = 1- (t / Tcon) from Tcon. As shown in FIG. 3, the time correction coefficient Kt takes a value of 1.0 at the time when the first injection pulse is output, decreases linearly with time, and the duration Tcon has elapsed. It becomes 0 at the time.

The low-rotation-time injection time increment calculating means 10 calculates the low-rotation basic injection time increment Tfi by multiplying the low-rotation crankcase temperature correction coefficient KLc and the time correction coefficient Kt.
fi × KLc × Kt is performed, and the calculation result is set as a low rotation time injection time increment TiL.

The atmospheric pressure correction coefficient setting means 12 calculates the atmospheric pressure correction coefficient Kap by calculating or searching a map based on the atmospheric pressure Ap detected by the atmospheric pressure sensor 22.
Ask for. The atmospheric pressure correction coefficient Kap takes a large value when the atmospheric pressure is high, and the value decreases as the atmospheric pressure decreases.

The intake temperature correction coefficient setting means 13 obtains an intake temperature correction coefficient Kar based on the intake temperature Tar detected by the intake temperature sensor 23. This intake temperature correction coefficient K
ar takes a small value when the intake air temperature is high, and increases as the intake air temperature decreases.

In this embodiment, the injection time correction amount setting means 1 detects the power supply voltage VB of the injector driving means 4 and sets the injection time correction amount Ts according to the detected power supply voltage.
4 is provided, and the injection time correction amount T obtained by the means is provided.
s is given to the fuel injection time setting means 2.

The fuel injection time setting means 2 calculates the fuel injection time Ti by the following equation, and gives data of the calculated fuel injection time Ti to the injector driving means 4.

Ti = (Tp + TiL) × Kar × Kcc × Kap + Ts (2) The injector driving means 4 operates from the time when the signal generator attached to the engine generates a specific signal (for example, Vp2) to the injection start time. Is calculated for each rotation speed as the injection timing measurement time, the measurement of the injection timing measurement time is started each time a specific signal is generated, and the injection is completed when the measurement of the injection timing measurement time is completed. A fuel injection pulse Pi having a pulse width equal to the time Ti is applied to a switching element such as a transistor. The switching element conducts while the fuel injection pulse Pi is given, and applies a power supply voltage to the drive coil of the injector 3. After a power supply voltage is applied to the injector, when a predetermined drive current flows, the injector valve opens and fuel is injected.

In general, when the voltage of the power supply for driving the injector is lowered, the rise of the driving voltage of the injector tends to be delayed.
It is shorter than the pulse width of i. In this embodiment, the fluctuation of the injection time due to the change of the power supply voltage is corrected by detecting the power supply voltage for driving the injector and adding an appropriate injection time correction amount Ts according to the power supply voltage.

The injector 3 opens its valve to inject fuel into the intake manifold while the fuel injection pulse Pi is being given.

FIG. 2 is a flow chart showing a routine executed by the computer for each rotation of the engine to control the fuel injection system. This routine is executed by a signal generator attached to the engine. Executed every time a signal is generated.

The signal generator generates a specific signal (for example, signal V
When p1) occurs, step S1 is first performed. In this step S1, the rotational speed N of the engine is calculated from the polar arc angle θ of the reluctor of the signal generator and the generation interval Tpd of the signals Vp1 and Vp2 based on the above equation (1), and the calculation result is stored in the RAM. Let it. By this step S1, the rotation speed detecting means 24 is realized.

In step S2, the throttle opening α given from the throttle opening sensor is read. Then, in step S3, a low-rotation basic injection time increment map is searched (by reading directly from the map or by using an interpolation method) by using the throttle opening α and the already calculated rotation speed N as parameters. The rotation-time basic injection time increment Tfi is set, and the set increment Tfi is stored in the RAM. The steps S2 and S3 implement the low-rotation basic injection time increment setting means 5.

In the next step S4, the crankcase temperature Tcc is read. In step S5, a low-speed crankcase temperature correction coefficient KLc is set by searching or calculating a map using the crankcase temperature Tcc as a parameter. The coefficient KLc is stored in the RAM. By the steps S4 and S5, the low-speed crankcase temperature correction coefficient setting means 7 is realized.

In step S6, the crankcase temperature Tcc
The duration Tcon is calculated by searching the duration map using the parameters and the rotation speed N as parameters, and the calculation result is stored in the RAM. This step S6 implements the duration setting means 8.

In step S7, a time correction coefficient Kt is calculated by the equation (2) based on the duration Tcon and the elapsed time t from the time when the first injection pulse was output, and the calculation result is stored in the RAM. By this step S7, the time correction coefficient setting means 9 is realized.

In the next step S8, the already set R
Basic negative injection time increment Tfi at low rotation stored in AM
And the crankcase temperature correction coefficient KLc and the time correction coefficient Kt are read, and the low rotation speed injection time increment TiL is calculated by the following equation, and the calculation result is stored in the RAM.

TiL = Tfi × KLc × Kt (3) By this step, the low-rotational injection time increment calculating means 1
0 is realized.

In step S9, the basic fuel injection time Tp is obtained by searching the basic fuel injection time map using the throttle opening α and the rotation speed N as parameters, and the basic fuel injection time Tp is stored in the RAM. By this step, the basic fuel injection time setting means 1 is realized.

After setting the basic fuel injection time Tp, the intake air temperature Tar is read in step S10, and then, in step S10.
At 11, the intake temperature correction coefficient Kar is set and stored in the RAM. The setting of the correction coefficient Kar is performed by searching a map or using an arithmetic expression. Steps S10 and S11 implement the intake air temperature correction coefficient setting means 13.

In step S12, the crankcase temperature Tcc provided from the crankcase temperature sensor is read, and a crankcase temperature correction coefficient Kcc for steady operation is set by searching or calculating a map. By this step, the crankcase temperature correction coefficient setting means 11 at the time of steady operation is realized.

In the next step S13, the atmospheric pressure Ap given from the atmospheric pressure sensor is read, and in step S14, an atmospheric pressure correction coefficient Kap is set by a map search or calculation to obtain R.
Store in AM. The steps S13 and S14 implement the atmospheric pressure correction coefficient setting means 12.

In step S15, the power supply voltage VB of the injector driving means is read, and in step S16, the injection time correction amount Ts is set by map search or calculation. By this step, the injection time correction amount setting means 14 is realized.

In step S17, the basic fuel injection time Tp that has already been set, the low-speed injection time increment TiL,
The intake temperature correction coefficient Kar, the crankcase temperature correction coefficient Kcc, the atmospheric pressure correction coefficient Kap, and the injection time correction amount Ts are read from the RAM, and the fuel injection time Ti is calculated by the above equation (2). By this step, the fuel injection time setting means 2 is realized.

In the next step S18, when the signal generator generates a specific signal (for example, the signal Vp2), the measurement of the injection timing measurement time already calculated in the main routine is started, and the measurement is completed. At this time, a fuel injection pulse Pi having a pulse width equal to the fuel injection time Ti is given to a control terminal of a switching element for turning on and off the power supply to the injector. The switching element conducts when the fuel injection pulse Pi is given, and applies the power supply voltage to the injector. As a result, a drive current flows through the injector. The injector opens the valve and injects fuel during a period when a drive current equal to or higher than a predetermined operation level flows.
After the fuel injection pulse Pi is output, the process returns to the start.

FIG. 4 shows an example of a temporal change of the fuel injection time Ti. In FIG. 4, the hatched portion A in the lower right part indicates the injection time during normal operation (= Tp × Kar ×
Kcc.times.Kap + Ts), and a portion B hatched to the lower left indicates an increment of the injection time (= TiL.times.Kar.times.Kcc.times.Kap) added to the injection time Tp at the time of low rotation.

In the above embodiment, the order of steps S1 to S18 shown in FIG. 2 can be appropriately changed. For example, step S9 can be brought before step S3.

When the injection time correction amount setting means 14 is provided as in the above embodiment, it is possible to prevent the actual fuel injection time from fluctuating due to a change in the power supply voltage, but there is no fluctuation in the power supply voltage. In this case, this means can be omitted. Further, in the above-described embodiment, in addition to the crankcase temperature, the intake air temperature and the atmospheric pressure are used as control conditions, and the correction coefficient according to each condition is obtained.
Other control conditions can be added as needed.

[0069]

As described above, according to the present invention, the crankcase temperature T is added to the basic injection time increment Tfi at low rotation set according to the engine speed N and the throttle opening α.
By multiplying a predetermined correction coefficient obtained by using cc and the elapsed time t as parameters, the value decreases as the crankcase temperature increases, and the value decreases over time. The injection time TP + TiL is calculated by adding the low rotation speed injection time increment TiL to the basic fuel injection time TP, and the injection time is further corrected according to various conditions to obtain the fuel injection time TL.
Since i is calculated, the fuel injection time during low rotation can be based on the throttle opening (air intake amount). Therefore, the air-fuel ratio of the air-fuel mixture involved in combustion can be always kept at an appropriate value during low rotation, which not only improves the startability of the engine, but also improves the warm-up operation.
If the accelerator is operated to change the inflow of air
Also, the rotation of the engine can be stabilized.

[0070] According to the present invention, accompanied with low rotation time injection time increment TiL over rise and time crankcase temperature
Therefore, when the temperature of the crankcase is low, the time (warming-up operation time) until the control shifts to the steady operation is extended, and when the temperature of the crankcase is high, the steady operation is performed. By reducing the time required to shift to the time control, the warm-up operation can be performed for an appropriate time according to the temperature of the crankcase, and wasteful fuel consumption can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing an algorithm of a program used to realize each function realizing means of the present invention by a computer.

FIG. 3 is a diagram illustrating an example of a change with respect to an elapsed time of a time correction coefficient set in an embodiment of the present invention.

FIG. 4 is a diagram showing an example of a change of a fuel injection time with respect to an elapsed time in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Basic fuel injection time 2 Fuel injection time setting means 3 Injector 4 Injector driving means 5 Low rotation basic injection time increment setting means 6 Low rotation injection time increment setting means 7 Low rotation crankcase temperature correction coefficient setting means 8 Duration Setting means 9 Time correction coefficient setting means 10 Injection time increment calculation means at low rotation speed 11 Crankcase temperature correction coefficient setting means during steady operation 12 Atmospheric pressure correction coefficient setting means 13 Intake air temperature correction coefficient setting means 14 Injection time correction amount setting means 20 Crank Case temperature sensor 21 Throttle opening degree sensor 22 Atmospheric pressure sensor 23 Intake air temperature sensor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02D 41/02 330 F02D 41/06 330

Claims (5)

(57) [Claims] 1. A basic fuel injection time Tp using a rotation speed N of a two-cycle engine and a throttle opening α as parameters.
, A fuel injection time setting means for correcting the basic fuel injection time Tp according to various conditions to set the fuel injection time Ti, and a fuel injection time setting means. A fuel injection pulse having a pulse width equal to the fuel injection time Ti to the injector. 2. A fuel injection system for a two-stroke engine, comprising: A low-rotation basic injection time increment setting means for setting a low-rotation basic injection time increment Tfi corresponding to an increase in fuel injection time at the time of rotation; By multiplying the elapsed time t by a predetermined correction coefficient obtained as a parameter, the temperature of the engine crankcase rises. Value each is reduced,
Low-rotation-time injection time increment setting means for obtaining a low-rotation-time injection time increment TiL whose value decreases even with the passage of time.
The fuel injection time Ti is calculated by further correcting the injection time TP + TiL obtained by adding the low-rotation-time injection time increment TiL to P in accordance with various conditions. apparatus. 2. The low-rotation-time crankcase temperature correction coefficient setting means for setting a low-rotation-time crankcase temperature correction coefficient KLc using the crankcase temperature Tcc of the engine as a parameter, Duration setting means for setting the duration Tcon of the injection amount increasing control at low rotation using the rotation speed N or the throttle opening α and the crankcase temperature Tcc as parameters, and outputting the first fuel injection pulse from the injector driving means. The time correction coefficient Kt is calculated from the elapsed time t measured by measuring the elapsed time t from the time when the time has elapsed and the duration Tcon.
= 1− (t / Tcon), and a calculation Tfi × KLc × Kt for multiplying the low-rotation basic injection time increment Tfi by a low-rotation crankcase temperature correction coefficient KLc and a time correction coefficient Kt. 2. A low-rotation-time injection time increment calculating means for calculating a low-rotation-time injection time increment TiL as a result of the calculation.
Fuel injection device for cycle engines. 3. A steady-state operation crankcase temperature correction coefficient setting means for setting a steady-state operation crankcase temperature correction coefficient Kcc using an engine crankcase temperature Tcc as a parameter, and an atmospheric pressure detected by an atmospheric pressure sensor as a parameter. Air pressure correction coefficient setting means for setting an air pressure correction coefficient Kap as: and an intake air temperature T of the engine detected by an intake air temperature sensor.
an intake temperature correction coefficient setting means for setting an intake temperature correction coefficient Kar using ar as a parameter, wherein the fuel injection time setting means includes (Tp + TiL) × Kar ×
3. The fuel injection device for a two-stroke engine according to claim 1, wherein a calculation of Kcc.times.Kap is performed, and the calculation result is used as the fuel injection time Ti. 4. A power supply voltage V of said injector driving means.
The fuel injection time setting means further comprises an injection time correction amount setting means for setting an injection time correction amount Ts according to the power supply voltage detected by detecting B.
4. The fuel injection device for a two-stroke engine according to claim 3, wherein a calculation of Kcc * Kap + Ts is performed, and a result of the calculation is defined as the fuel injection time Ti. 5. An injection time correction amount setting means for setting an injection time correction amount Ts using an engine speed as a parameter, wherein the fuel injection time setting means comprises (Tp + TiL) × Kar ×
4. The fuel injection device for a two-stroke engine according to claim 3, wherein a calculation of Kcc * Kap + Ts is performed, and a result of the calculation is defined as the fuel injection time Ti.