JP3329659B2 - Engine fuel injection device - 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 for an engine.

[0002]

2. Description of the Related Art In recent years, fuel injection devices have been widely used in engines of small vehicles such as motorcycles and snowmobiles. The fuel injection device includes an injector installed in an intake pipe of an engine, a fuel pump for pressure-feeding fuel from a fuel tank to the injector, and control means for controlling opening and closing of an injector of the injector.

A small computer is often used as the control means, and various data necessary for fuel injection control such as atmospheric pressure, engine temperature, throttle opening, intake air temperature, and engine speed are used for this control means. Is input through each sensor as needed. The control means always calculates an optimal air-fuel ratio using these data as parameters,
The fuel is injected by controlling the opening and closing of the injector of the injector to match this air-fuel ratio.

When the engine is started, not all of the fuel injected from the injector is directly supplied to the combustion chamber, but some of the fuel is consumed to form a liquid film of fuel on the inner wall of the fuel supply passage. Is done. Therefore, the engine is difficult to start unless the compensation is made. Therefore, when the engine is started, the control means is programmed to perform the start-up increasing injection control for increasing the fuel injection amount of the injector.

[0005] For example, in the case of a two-cycle engine, the fuel supply passage corresponds to the entire interior of the intake pipe and the crankcase. Is set to be larger than that in the four-cycle engine. The fuel injection amount is increased by setting a long valve opening time of the injector of the injector that opens and closes in a fine cycle.

FIG. 5 is a diagram showing an example of a startup increased injection control in a two-cycle engine. In this figure, the vertical axis represents the total amount Ti of the fuel injection amount, and the horizontal axis represents the control time t. The line TU in the figure represents the amount of fuel injection required for steady operation of the engine, and the line TB represents the amount of fuel injection required for engine startup. The sum of TU and TB is Ti.

[0007] The initial injection amount of the start increasing injection amount TB is set to the maximum value TBA at the time of engine start tc0, and thereafter, the start increasing fuel injection amount TB is reduced with the lapse of time to a predetermined start increasing amount control end time tc. Then it becomes zero. The start increasing amount control end time tc is set at the time when the formation of the fuel liquid film in the fuel supply passage is completed.

FIG. 6 is a diagram showing a start increasing injection amount TB in FIG.
FIG. 3 is a diagram showing only a part of FIG. The initial injection amount of the startup increase injection amount TB and the start increase control end time are set based on a temperature representing the engine temperature such as the cooling water temperature Tw. For example, when the cooling water temperature Tw is −20 ° C., the initial injection amount is set to TB3, and the startup increasing control end time is set to tc3. As the cooling water temperature Tw increases, the initial injection amount becomes TB3.
2 → TB1 and the end time of the startup increase control is tc2 →
It will be shortened to tc1.

Incidentally, the starting increased injection amount TB also changes depending on the atmospheric pressure. For example, as shown in FIG. 7, even if the engine cooling water temperature Tw is the same -20 ° C., the atmospheric pressure Pa
When the pressure is 760 mmHg, 650 mmHg, and 500 mmHg, the value of the initial injection amount of the startup increased injection amount TB is significantly different from TBa to TBc. As shown in this figure, as the atmospheric pressure Pa becomes lower, it is necessary to reduce the starting increased injection amount from TBa to TBc.

[0010]

However, in the conventional fuel injection device, since the starting increased injection amount TB is not set based on the difference between the atmospheric pressures as described above, the altitude of the place where the engine is started, Depending on weather conditions, starting the engine was sometimes very difficult.

For example, in the case of an engine of a vehicle used at both low altitude and high altitude such as a snowmobile, if the starting increased injection amount TB is set for low altitude with high atmospheric pressure, the engine is operated at high altitude with low atmospheric pressure. At the time of starting, the amount of fuel increase is too large and the mixture becomes rich (over-rich), which may cause ignition plug fogging or engine stall.

Conversely, if the starting increased injection amount TB is set for a high altitude where the atmospheric pressure is low, when the engine is started in a low altitude where the atmospheric pressure is high, the amount of the increased fuel is likely to be insufficient. At the same time, the engine speed may drop or the engine may stop.

Such a problem becomes a serious problem particularly in the case of a two-stroke engine in which the inner area of the fuel supply passage is larger than that of a four-stroke engine.

The present invention has been made in order to solve this problem, and an object of the present invention is to provide an engine fuel injection device which can provide a good startability regardless of a change in atmospheric pressure.

[0015]

In order to achieve the above object, a fuel injection device for an engine according to the present invention controls a fuel injection amount of an injector so that an optimum air-fuel ratio is always obtained, and at the time of starting the engine, In the fuel injection device for an engine including control means programmed to perform a start-up fuel injection control for increasing a fuel injection amount until a liquid film of the fuel is formed on the inner wall of the supply passage, Atmospheric pressure was added to the parameters for setting the start-up increasing injection amount and the start-up control end time in the above, and the control means was programmed such that the lower the atmospheric pressure, the smaller the start-up increasing injection amount and the start-up increase control end time became longer. It is characterized by the following.

As described above, as the atmospheric pressure becomes lower, the start-up increasing injection amount becomes smaller and the start-up increasing control end time is set longer, so that when the atmospheric pressure is lower, the fuel film gradually decreases due to the smaller increase fuel. It is formed on the inner wall of the supply passage. For this reason, there is no fear that the ignition plug is fogged or the engine is stalled due to an excessive amount of fuel increase, and the startability is improved.

When the atmospheric pressure is high, the start-up increasing injection amount is large and the start-up increasing control end time is set short, so that
A liquid film of the fuel is rapidly formed on the inner wall of the fuel supply passage due to the increased amount of the fuel. For this reason, there is no fear that the engine speed decreases or the engine stops at the same time when the start-up increasing injection control ends, and the startability is improved.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example in which a fuel injection device according to the present invention is applied to a two-cycle engine mounted on a motorcycle, a snowmobile, or the like.

The fuel injection device 1 includes a control unit 2 using a small computer as control means. The control unit 2 includes a fuel injection device such as an injector 3 and a fuel pump 4, an atmospheric pressure sensor 5, Detection units such as a cooling water temperature sensor 6, a throttle opening sensor 7, an air temperature sensor 8, and an electromagnetic pickup coil 9 are connected.

The injector 3 is provided in the intake pipe 12 of the two-stroke engine 11, and is configured to receive a drive signal from the control unit 2 and to control the opening and closing of the injection valve 3a in a fine cycle. Since the fuel from the fuel tank 13 is always pumped to the injector 3 via the fuel pump 4, the fuel is injected into the intake pipe 12 each time the injector 3 a of the injector 3 is opened. Adjustment of the fuel injection amount is performed by changing the valve opening time of the injection valve 3a.

On the other hand, the atmospheric pressure sensor 5 detects the atmospheric pressure and inputs the detected atmospheric pressure to the control unit 2, and the cooling water temperature sensor 6
Detects the temperature of the cooling water circulating in the cylinder 14 of the two-stroke engine 11 as the engine temperature and inputs it to the control unit 2. Further, the throttle opening sensor 7
Detects the opening of the throttle valve 15 for opening and closing the intake pipe 12 and inputs the same to the control unit 2. The air temperature sensor 8 detects the temperature of the intake air and inputs it to the control unit 2.

On the other hand, the electromagnetic pickup coil 9 is provided in the flywheel magneto 16 of the two-cycle engine 11, and is configured to detect the rotation speed of the crankshaft 17 of the two-cycle engine 11 and input the detected rotation speed to the control unit 2. Have been. The flywheel magneto 16 supplies AC power to the entire vehicle body such as a motorcycle or a snowmobile, and controls the control unit 2 and the injector 3.
And the power supply of the fuel pump 4 is provided.

The control unit 2 always calculates an optimum air-fuel ratio using the various data input from the detection units 5 to 9 as parameters, and opens and closes the injection valve 3a of the injector 3 so as to match the air-fuel ratio. To control the fuel injection amount.

Further, the control unit 2 performs a start-up increasing injection control for increasing the fuel injection amount until the liquid film of the fuel is formed on the inner wall of the fuel supply passage when the two-cycle engine 11 is started, as described later. Be programmed. The fuel supply passage described here is the entire inside of the intake pipe 12 and the crankcase 18.

Further, the control unit 2 controls the driving of the fuel pump 4 and controls the ignition of the ignition plug 20 via the ignition coil 19. In FIG. 1, reference numeral 21 denotes a fuel pressure regulator, and reference numeral 22 denotes a high-speed and low-speed exciter.

FIG. 2 shows an embodiment of the starting increased injection control executed by the control unit 2. In this figure, the vertical axis represents the starting increased injection amount TB, and the horizontal axis represents the control time t.

The parameters for setting the start increasing injection amount TB and the start increasing control end time tc during the start increasing injection control include an engine temperature (cooling water temperature), a throttle opening, an intake air temperature, an engine speed, and the like. But,
Here, the atmospheric pressure is added to these parameters, and the lower the atmospheric pressure is, the smaller the start increasing injection amount TB is,
The control unit 2 is programmed such that the start increasing control end time tc becomes longer. FIG. 2 shows a change in the startup increasing injection amount TB when the cooling water temperature Tw is constant at, for example, −20 ° C.

For example, when the atmospheric pressure pa is 760 mmHg,
The initial injection amount of the start increasing injection amount TB is the engine start time tc.
At 0, it is set to TBA. Thereafter, the start-up increasing injection amount TB is reduced with time and becomes zero when a predetermined start-up increasing control end time tc1 is reached.

When the atmospheric pressure pa drops to 650 mmHg, the initial injection amount is set to TBB which is smaller than TBA, and the start increasing control end time is set to tc2 which is longer than tc1. Further, when the atmospheric pressure pa drops to 500 mmHg, the initial injection amount is set to TBC smaller than TBB, and the start increasing control end time is set to tc3 longer than tc2.

FIG. 3 is a flow chart showing a flow of a calculation process for obtaining the starting increased injection amount TB executed by the control unit 2. In this flowchart, each calculation step is represented by S1, S2,.

The flow of this flowchart will be described.
First, after the calculation process is started, the throttle opening α is determined in S1.
From the [α-N] three-dimensional map including the engine speed N and the basic startup increased injection amount TB0 (not shown in FIG. 2).

Next, a cooling water temperature correction coefficient Kw is obtained in S2, and an atmospheric pressure correction coefficient Kp is obtained in S3. Then, in S4, the cooling water temperature Tw and the engine speed N
The basic start increasing control end time t _cont is obtained from the [Tw-N] three-dimensional map (not shown in FIG. 2).

Subsequently, in S5, an atmospheric pressure correction coefficient Ktcp of the start increasing control end time is obtained. The atmospheric pressure correction coefficient Ktcp is, for example, as shown in the table of FIG.
It is set to 1.0 at 760 mmHg, 1.5 at 650 mmHg, and 2.0 at 500 mmHg, and the value between them is determined by interpolation calculation.

Thereafter, at S6, the start increasing control end time tc
Is calculated. The start increase control end time tc is calculated by multiplying the basic start increase control end time t _cont obtained in S4 by the start increase control end time atmospheric pressure correction coefficient Ktcp obtained in S5.

Then, in step S7, the elapsed time ts from the engine start time tc0 is read, and in step S8, the starting increased injection amount T
B is calculated. The formula for calculating the starting increased injection amount TB is:

(Equation 1) Becomes Since tc is calculated based on the atmospheric pressure correction coefficient Ktcp of the start increasing control end time, it becomes longer as the atmospheric pressure becomes lower. In addition, TB decreases as the atmospheric pressure decreases. When S8 ends, the operation is returned.

As described above, as the atmospheric pressure becomes lower, the starting increasing injection amount TB decreases, and the starting increasing control end time tc
Therefore, at high altitudes where the atmospheric pressure is low, a small amount of increased fuel gradually forms a liquid film of fuel on the inner wall of the fuel supply passage. For this reason, there is no fear that the ignition plug 20 is fogged or the engine is stalled due to an excessive amount of fuel increase, and the startability of the two-cycle engine 11 is improved.

When the atmospheric pressure is high, a fuel film is rapidly formed on the inner wall of the fuel supply passage due to a large amount of increased fuel, so that the engine speed decreases at the same time as the end of the startup increasing injection control. There is no concern that the engine stops or the engine stops, and the startability is improved.

In this way, a good startability can be obtained irrespective of changes in the atmospheric pressure. For example, by mounting this fuel injection device 1 on an engine of a vehicle used at both low altitude and high altitude such as a snowmobile, The engine can be started quickly without causing engine malfunction.

[0039]

As described above, the fuel injection device for an engine according to the present invention controls the fuel injection amount of the injector so as to always obtain an optimum air-fuel ratio, and the fuel injection amount is controlled by the inner wall of the fuel supply passage when the engine is started. In a fuel injection device for an engine comprising control means programmed to perform a start-up fuel injection control for increasing a fuel injection amount until a liquid film of fuel is formed, a start-up fuel injection amount at the time of the above-mentioned start fuel injection control. Atmospheric pressure is added to the parameters for setting TB and the start increasing control end time tc, and the control means is programmed so that the lower the atmospheric pressure, the smaller the start increasing injection amount TB and the longer the start increasing control end time tc. It is characterized by the following.

In this manner, when the atmospheric pressure is low, a small amount of fuel is added to gradually increase the liquid film of the fuel on the inner wall of the fuel supply passage. At the same time, when the atmospheric pressure is high, a large amount of increased fuel causes a liquid film of fuel to be rapidly formed on the inner wall of the fuel supply passage. There is no concern that the engine will drop or the engine will stop. Therefore, good startability can be provided regardless of changes in the atmospheric pressure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example in which a fuel injection device according to the present invention is applied to a two-cycle engine mounted on a motorcycle, a snowmobile, or the like.

FIG. 2 is a diagram showing one embodiment of a startup increased injection control executed by a control unit.

FIG. 3 is a flowchart showing a flow of a calculation process for obtaining a starting increased injection amount executed by a control unit.

FIG. 4 is a diagram showing a relationship between an atmospheric pressure and an atmospheric pressure correction coefficient of a start increasing control end time.

FIG. 5 is a diagram showing an example of a startup increased injection control in a two-cycle engine.

FIG. 6 is a diagram showing a conventional technique, and is a diagram showing only a portion of a starting increased injection amount in FIG. 5;

FIG. 7 is a diagram showing a startup increasing injection amount that changes according to the atmospheric pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection device 2 Control unit as control means 3 Injector 11 2 cycle engine 12 Intake pipe which is a fuel supply passage 18 Crankcase which is a fuel supply passage TB Start increasing fuel injection amount tc Start increasing control end time

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Yoichi Tokomura (56) References JP-A-54-111021 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/06 330 F02D 41/04 330 F02D 45/00 360

Claims (1)

(57) [Claims] 1. The fuel injection amount of the injector 3 is controlled so that an optimum air-fuel ratio is always obtained. When the engine is started, fuel injection is performed until a liquid film of fuel is formed on the inner wall of the fuel supply passage (12, 18). In a fuel injection device for an engine including a control means (2) programmed to perform a start-up increasing injection control for increasing the amount, a start-up increasing injection amount TB and a start-up increasing control end time tc at the time of the start-up increasing injection control. Atmospheric pressure is added to a parameter for setting the fuel injection amount of the engine, and the control means is programmed such that the lower the atmospheric pressure, the smaller the increased start-up injection amount TB and the longer the start-up increase control end time tc is. Apparatus 1.