CN1328496C - Fuel injection control device - Google Patents

Abstract

A fuel injection control device can detect the quality of the intake air without using an air flow meter and calculate the fuel injection amount. A compression/exhaust time calculation unit (3) calculates the time Tc1, Tc2 at the start and end of the compression stroke and the time Te1, Te2 at the start and end of the exhaust stroke, respectively, in accordance with the cycle of the pulse signal generated by the crank angle sensor (2). An intake air mass calculating unit (4) for calculating the intake air mass [ { (1/Tc1) ]²-(1/Tc2)²}-{(1/Te1)²-(1/Te2)²}]And the quality of the sucked air is calculated. The obtained intake air mass is input to a fuel injection amount calculation unit (5), and a fuel injection amount corresponding to the intake air mass is calculated in accordance with a set air-fuel ratio. The fuel injection valve (1b) is driven at a valve opening load corresponding to the calculated fuel injection amount, and appropriate fuel is supplied to the engine (1).

Description

Fuel Injection Control

technical field

The present invention relates to a fuel injection control device, in particular to a fuel injection control device capable of determining the fuel injection amount of a single-cylinder four-cycle engine according to estimated intake air quality.

Background technique

The fuel injection control device determines the fuel injection amount corresponding to the operating state based on the intake air mass and according to the set air-fuel ratio. In order to measure the amount of intake air, an air flow meter is generally used. Japanese Unexamined Patent Publication No. 58-17317 discloses an example of an air flow meter for detecting the amount of intake air for determining the fuel injection amount. In addition, instead of using an air flow meter, the amount of intake air can be estimated from the intake negative pressure and the engine speed using a map of the intake negative pressure-engine speed. In addition, the amount of intake air can also be estimated from the throttle opening.

FIG. 9 shows a method of determining a basic injection quantity in conventional fuel injection control. In this figure, the region determined by the throttle opening θTH and the engine speed Ne is divided into two parts, that is, the low-load region LLZ where the engine speed Ne is relatively low and the throttle opening θTH is relatively small, and the engine speed Ne is relatively high and the throttle valve opening θTH is relatively large in the high load region HLZ.

In the low load region LLZ, the basic injection amount is determined using a PB-NE map in which the basic injection amount is set as a function of the intake pipe negative pressure PB and the engine speed Ne. On the other hand, in the high load region HLZ, the basic injection amount is determined using a θTH-NE map that sets the basic injection amount as a function of the throttle valve opening θTH and the engine speed Ne. Then, after engine temperature correction, intake air temperature correction, atmospheric pressure correction, etc. are performed on the numerical value of the map, the fuel injection amount is finally determined.

When using an air flow meter, although it is possible to detect the correct amount of intake air, the air flow meter is indispensable, and the number of parts cannot be reduced. Similarly, the suction negative pressure sensor (PB sensor) for detecting the negative pressure of the suction pipe is also indispensable, and the number of parts cannot be reduced. In addition, when estimating the intake air amount from the throttle opening degree, it is desired to improve the estimation accuracy of the intake air amount in the low throttle opening degree region.

Contents of the invention

In view of the above problems, an object of the present invention is to provide a fuel injection control device capable of determining a fuel injection amount based on an accurate intake air mass without using components such as a sensor.

In order to solve the above-mentioned problems, the first feature of the fuel injection control device of the single-cylinder four-cycle engine of the present invention is to include: an intake air mass calculation unit, which uses the energy loss generated in the compression stroke and the energy loss generated in the exhaust stroke function to calculate the intake air mass of the intake stroke; the first fuel injection quantity calculation unit calculates the fuel injection quantity corresponding to the intake air mass according to the set air-fuel ratio.

According to a first feature, the intake air mass is calculated based on energy losses in the compression and exhaust strokes.

In addition, the second feature of the present invention is that it includes a time calculation unit that calculates the elapsed time within the crankshaft angle preset at the start and end of the compression stroke and the preset crankshaft angle at the start and end of the exhaust stroke. The elapsed time in the rotation angle is calculated separately, and the intake air mass calculation unit uses the elapsed time of the crankshaft rotation at the start and end of the compression stroke and the time elapsed for the crankshaft rotation at the start and end of the exhaust stroke The energy loss is calculated as a function of the difference in elapsed time for a predetermined crank angle.

According to the second feature, since the energy loss is represented by the function of the time difference between the start and end of the compression stroke and the exhaust stroke, for example, in a commonly available four-cycle engine, the compression stroke and the exhaust stroke can be detected according to From the output of the crank angle sensor at the time of the air stroke, the time required for a change in the crank angle within a predetermined range can be obtained to calculate the energy loss.

In addition, the third feature of the present invention is that the intake air mass calculation unit uses the elapsed time Tc1 and Tc2 for the crankshaft at the beginning and end of the compression stroke to rotate through the preset crank angle and the time Tc2 for the crankshaft at the beginning and end of the exhaust stroke. The time Te1 and Te2 elapsed after turning the preset crank angle, use the following function to find the intake air mass,

Inhaled air mass ∝[{(1/Tc1) ² -(1/Tc2) ² }-{(1/Te1) ² -(1/Te2) ² }].

According to the third feature, input the calculated start and end time of the compression stroke and the start and end time of the exhaust stroke, and use the above formula to calculate the intake air mass.

The fourth feature of the present invention to solve the above-mentioned problem is that, in addition to the first fuel injection amount calculation unit, it also includes: a second fuel injection amount calculation unit that determines the basic fuel as a function of the throttle opening and the engine speed. Injection amount, and perform at least air density correction on the basic fuel injection amount, so as to determine fuel injection amount; control switching unit, which selects the first fuel injection amount calculation unit in a predetermined low load area, and in the low load area Otherwise select the second fuel injection amount calculation unit. In addition, a fifth feature of the present invention is to include an air density calculation unit that calculates an air density for performing the air density correction based on the intake air mass and the standard air flow rate.

According to the fourth feature, in the low load region, the fuel injection amount is calculated using the intake air mass calculated from the energy loss in the compression stroke and the exhaust stroke.

In addition, the sixth feature of the present invention is that the low-load region is an idling region, and the control switching means includes means for determining the idling region and the constant-operating region based on a rotational change rate of the engine.

Since the switching between the idling operation range and the constant operation range is performed according to the clutch opening and closing, engagement of the clutch causes a change in the moment of inertia of the engine system, resulting in a difference in the rotational change rate. In the sixth feature, the clutch disengagement, that is, the switching in the low load region and other load regions can be judged from the difference in the rotational change rate.

Description of drawings

FIG. 1 is a block diagram showing the configuration of a fuel injection control device according to an embodiment of the present invention.

Figure 2 shows the energy produced by each stroke in a four-cycle engine.

FIG. 3 is a flowchart showing a calculation procedure of a fuel injection amount.

4 is a block diagram showing a main hardware configuration of a fuel injection control device according to a second embodiment.

FIG. 5 shows division of engine load regions.

FIG. 6 shows a load range judgment map formed by clutch judgment.

7 is a block diagram showing the configuration of a fuel injection control device according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing the calculation procedure of the fuel injection amount in the high load region.

FIG. 9 shows division of load areas in the prior art.

Detailed ways

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a fuel injection control device according to a first embodiment of the present invention. In this figure, a four-cycle single-cylinder engine 1 is provided with a crank angle sensor 2 . The crank angle sensor 2 is composed of a sensor for detecting a plurality of detected objects (such as magnetic materials such as iron) arranged at equal angular intervals around the crankshaft or the shaft 1a combined with the crankshaft, and generates a pulse signal corresponding to the crankshaft angle. The output signal of the crank angle sensor 2 is input to a compression/exhaust time calculation unit 3 . The compression/exhaust time calculation part 3 calculates the time required for the change of the preset crank angle at the beginning and end of the compression stroke and the time required for the change of the crank angle at the beginning and end of the exhaust stroke according to the period of the pulse signal output by the crank angle sensor 2. The time required for the change of the preset crank angle at the end end, for example, the preset crank angle is 30°. The calculated start and end times of the compression stroke and the start and end times of the exhaust stroke are input to the intake air mass calculation unit 4 . The air mass calculation unit 4 calculates the intake air mass using a calculation formula described later, based on the time of the start and end of the compression stroke and the time of the start and end of the exhaust stroke.

The calculated intake air mass is input to the fuel injection amount calculation unit 5, and multiplied by the excess ratio λ determined based on the set air-fuel ratio to calculate the fuel injection amount corresponding to the intake air mass. The excess ratio λ is determined according to the set air-fuel ratio. The calculated fuel injection amount is also corrected in the correction unit 6 with a correction coefficient corresponding to the acceleration state (throttle opening degree change rate). The corrected fuel injection amount is input to the fuel injection valve drive unit 7 for driving the fuel injection valve 16 . The fuel injection valve driver 7 drives the fuel injection valve 16 with a valve opening duty corresponding to the fuel injection amount. The calculation units 3, 4, 5 and the correction unit 6 may be constituted by microcomputers.

Next, the formula for calculating the intake air mass will be described. The intake air mass is calculated on the premise of the following principle. Figure 2 shows the energy produced by each stroke of a four-cycle engine. A large amount of combustion energy is generated in the combustion stroke. On the contrary, in the exhaust, suction and compression strokes, energy is consumed due to exhaust resistance, suction resistance and compression resistance, that is, negative energy is generated. And, mechanical frictional resistance, such as the frictional resistance generated between the piston and the cylinder, is also used as negative energy.

Here, since the compression of the intake air requires energy, that is, compression resistance, the energy loss in the compression stroke is larger than that in the exhaust stroke. Since the exhaust loss is very small in the low load region, that is, low output operation, the energy loss in the exhaust stroke is basically frictional resistance. The compression resistance increases with the increase of the intake air mass, that is, the energy loss of the compression stroke is considered to be a function of the intake air mass.

The energy loss of the compression stroke and the energy loss of the exhaust stroke can be calculated from the time of the start and end of the compression stroke and the time of the start and end of the exhaust stroke, respectively. This is due to the loss of energy reducing the engine speed. Therefore, the inhaled air quality can be calculated by the following formula, inhaled air quality=K×[{(1/Tc1) ² -(1/Tc2) ² }

-{(1/Te1) ² -(1/Te2) ² }]……………(Formula 1)

In formula 1, Tc1 and Tc2 are the predetermined crank angle change time at the start and end of the compression stroke, Te1 and Te2 are the predetermined crank angle change time at the start and end of the exhaust stroke, and K is the time used to convert the compression energy loss into the intake air mass correction factor.

FIG. 3 is a flowchart showing a calculation procedure of the fuel injection amount. In step S1, delta times (delta times) Te1 and Te2 at the start and end of the exhaust stroke are calculated. In step S2, delta times (delta times) Tc1 and Tc2 at the start and end of the compression stroke are calculated. In step S3, the intake air mass is calculated in the intake air mass calculation unit 10 using the above formula (Formula 1). In step S4, the fuel injection amount calculation unit 11 calculates the fuel injection amount by multiplying the air excess ratio λ by the intake air mass. The excess air ratio λ is determined by the set air-fuel ratio A/F. The calculated fuel injection amount can be obtained by determining the valve opening time of the fuel injection valve 6 , that is, the valve opening load.

4 is a block diagram showing the structure of a fuel injection control device according to a second embodiment of the present invention. Specifically, in this figure, signals detected by a crank angle sensor 2 , a throttle opening sensor 13 , an atmospheric temperature (TA) sensor 14 , and an engine temperature (TE) sensor 15 are input to an ECU 11 described later. The crank angle sensor 2 will be described with reference to FIG. 1 .

The throttle opening sensor 13 is connected to the throttle valve provided in the throttle body on the intake pipe of the engine 1, and outputs the throttle opening θTH. The TE sensor 15 can be installed on the oil pan of the engine, for example, and sense the temperature of the engine oil with a probe immersed in the engine oil. The sensed oil temperature is input to the ECU 11 as a signal representing the engine temperature.

ECU11 is composed of a microcomputer and its peripheral equipment, receives the output of the sensors 2, 13, 14, 15, processes them according to a predetermined algorithm, and outputs instructions as the processing results to the injector (fuel injection valve) 16. Ignition coil 17 and fuel pump 18, etc.

Next, fuel injection control performed by the ECU 11 will be described. In the second embodiment, it is assumed that the no-load operation region is a low-load region, and the operation region other than the no-load operation region is a high-load region. That is, the load range is divided by the engine speed Ne. FIG. 5 shows the division of load regions with the engine speed as a parameter. As shown in this figure, the load region is divided into a low load region LLZ and a high load region HLZ according to the engine speed. That is, regardless of the throttle opening θTH, the idling region where the engine speed Ne is low is defined as the low load region LLZ, and the region where the engine speed Ne is high is defined as the high load region HLZ.

And, in each load range, in order to calculate the fuel injection amount, the algorithm is switched as follows. For example, in an engine having a centrifugal clutch, it may be changed in accordance with the determination result of whether the engine speed Ne exceeds the clutch engagement speed. That is, when the engine rotation speed Ne exceeds the clutch engagement rotation speed, the engine switches to the high load region due to changing from the idling operation to the constant running. Therefore, the calculation algorithm of the fuel injection amount also becomes an algorithm for the high load region.

However, it is judged whether the engine speed exceeds the clutch engagement speed. Since it is not done by directly detecting the engagement of the centrifugal clutch, the accuracy is very low. Therefore, other methods of more reliably detecting engagement of the centrifugal clutch may be employed. For example, the engagement and disengagement of the clutch can be detected from the rate of change of engine rotation when the clutch is engaged and when the clutch is disengaged. This is due to the change in the moment of inertia caused by clutch clutching, thereby changing the rate of change of engine rotation.

The rotational change rate can be calculated from the time required for the compression stroke and the exhaust stroke, for example. Since the time difference between the compression stroke and the exhaust stroke changes significantly due to clutch disengagement, the rate of change of rotation can be represented as a function of the ratio of the time difference to the time of one cycle (two revolutions of the crankshaft).

Fig. 6 shows the clutch clutch line with the engine rotational change rate and the engine rotational speed as parameters. In the figure, the vertical axis represents the engine rotational speed change rate TSRAT, and the horizontal axis represents the engine rotational speed Ne, and the clutch is disengaged within the range in which the rotational speed change rate TSRAT is larger than the clutch clutch line CCL. That is, in the no-load state, the engine load is small. On the other hand, the clutch is engaged in the range where the rotation rate TSRAT is smaller than the clutch line CCL. That is, the engine is in a high-load region other than idling.

The rate of change of rotation TSRAT is, for example, a function of the difference between the compression stroke time and the exhaust stroke time. Therefore, monitor the engine rotation rate TSRAT and the engine speed Ne, judge the load according to whether the engine rotation rate TSRAT is above the clutch line CCL, and switch the fuel injection amount calculation algorithm.

Next, the procedure for calculating the fuel injection amount will be described. The calculation of the fuel injection amount in the low load region LLZ is performed by the following equation (Equation 2),

Fuel injection amount=intake air mass/set air-fuel ratio A/F... (Formula 2) The set air-fuel ratio A/F is determined based on the theoretical air-fuel ratio, taking into consideration the acceleration state and the like. Here, the intake air mass is not detected by an air flow meter, but is calculated from the time required for rotation in a predetermined range (for example, a crank angle of 30°) at the start and end ends of the compression stroke and the exhaust stroke, as described below.

The calculation principle and calculation formula of the inhaled air mass have been described in the first embodiment.

In the high load region HLZ, a value (map value) preset as a function of the throttle opening θTH and the engine speed Ne is read out using the throttle opening θTH and the engine speed Ne as keywords, and the map value is calculated. Temperature correction, intake air temperature correction, and atmospheric pressure correction are performed to obtain the fuel injection amount.

7 is a block diagram showing the functions of main parts of fuel injection control in a second embodiment. The output signal of the crank angle sensor 2 provided on the four-cycle single-cylinder engine in this figure is input to the compression/exhaust time calculation part 103, and the compression/exhaust time calculation part 103 is based on the output signal of the crank angle sensor 2. The predetermined crank angle change times Tc1, Tc2, Te1, and Te2 at the start and end ends of the compression stroke and the exhaust stroke are periodically calculated. The calculated time is input to intake air mass calculation unit 104 . The intake air mass calculation unit 104 calculates the intake air mass using the calculation formula (Formula 1) based on the predetermined crank angle change time.

The calculated intake air mass is input to the fuel injection amount calculation unit 105, and the fuel injection amount corresponding to the intake air mass is calculated in consideration of the set air-fuel ratio A/F.

In the fuel injection amount map 106, the basic fuel injection amount is set as a map value by using the function of the engine speed Ne and the throttle opening θTH, when the output of the crank angle sensor 2 representing the engine speed Ne and the output of the throttle opening sensor 13 When the represented throttle opening θTH is input into the fuel injection amount map 106, the map is searched using these inputs as keywords, and the basic fuel injection amount is output.

The basic fuel injection amount is input to the correction unit 107, and the map value is multiplied by an engine temperature correction coefficient, an intake air temperature correction coefficient, and an atmospheric pressure correction (air density correction) coefficient to determine the fuel injection amount. The correction unit 107 has a table including correction coefficients corresponding to the engine temperature, the intake air temperature, and the air density, respectively. When the engine temperature TE, the intake air temperature TA, and the air density AD are provided, the basic fuel injection amount is corrected with coefficients corresponding to them.

In addition, the air density can be obtained by dividing the intake air mass by the standard air flow rate in the air density calculation unit 108 . The standard air flow rate can be obtained from the map value of the standard air flow rate measured under the condition of one atmospheric pressure. That is, the standard air flow rate that is a function of the throttle valve opening θTH and the engine speed Ne may be mapped in advance, and the map may be searched to obtain the standard air flow rate.

The switching unit 109 selects according to the determination of whether the load range judging unit 110 is in the low load range or the high load range, and if it is in the low load range, selects the output of the fuel injection calculation unit 105, and if it is in the high load range, selects the corrected output of section 107. The load area determination unit 110 searches the above-mentioned graph 6 based on the engine speed change rate, and determines the load area.

The fuel injection amount selected and output from the switching unit 109 is input to the fuel injection valve drive unit 7 that drives the fuel injection valve 16 . The fuel injection valve driver 7 drives the fuel injection valve 16 with a valve opening load corresponding to the fuel injection amount.

The calculation procedure of the fuel injection amount for the low-load range can use the processing of the flowchart described with reference to FIG. 3 .

FIG. 8 is a flowchart of a fuel injection amount calculation procedure for a high load region. In step S10, the engine speed Ne is read, and in step 11, the throttle opening θTH is read. In step S12, the fuel injection amount map 12 is searched using the engine θTH and the throttle opening θTH as keywords to obtain the basic fuel injection amount. In step 13, the basic fuel injection amount is multiplied by the engine temperature correction coefficient, the intake air temperature correction coefficient, and the atmospheric pressure correction coefficient to calculate the fuel injection amount.

As can be seen from the above description, according to the first to sixth features of the present invention, the intake air mass can be calculated from the energy loss in the engine cycle. In particular, according to the third and fourth features of the present invention, the intake air mass can be calculated from the elapsed time of the predetermined range in the compression stroke and the exhaust stroke, that is, the predetermined crank angle change time. Since these times can be detected by sensors such as a crank angle sensor, which are usually equipped with a four-cycle engine, the intake air mass necessary to determine the fuel injection amount can be calculated even without an air flow meter or an intake pressure sensor.

According to the second, fifth or sixth feature of the present invention, the intake air mass is calculated from the energy loss of the engine cycle, and the fuel injection quantity in the low load area is calculated based on the intake air mass, and at the same time, the air in areas other than the low load area A density correction can also be determined from the calculated intake air mass.

According to the sixth feature of the present invention, it is possible to switch the injection amount calculation means with high accuracy in judging the low load region and other regions based on the rate of change of engine rotation.

Claims (6)

1. fuel injection control system, it is the fuel injection control system of one-cylinder four-circulation motor, it is characterized in that, comprising:

Suck air quality and calculate unit (104), its function calculation with the energy loss that produces in energy loss that produces in the compression stroke and the exhaust stroke goes out the suction air quality of suction stroke;

The first fuel injection amount computing unit (105), it calculates the fuel injection amount of corresponding described suction air quality according to the air fuel ratio of setting.

2. fuel injection control system according to claim 1 is characterized in that, also comprises:

The second fuel injection amount computing unit (106,107) is determined the basic fuel injection amount as the function of throttle opening and engine speed, and this basic fuel injection amount is carried out air density at least proofread and correct, thereby determines fuel injection amount;

Control switching unit (109), it selects the described first fuel injection amount computing unit (105) in predetermined low-load region, selects the described second fuel injection amount computing unit (106,107) beyond described low-load region.

3. fuel injection control system according to claim 1 and 2 is characterized in that,

Have time calculating unit (103), it will be in the beginning of compression stroke, finish the transit time in the predefined crank angle of end and calculate respectively in the beginning of exhaust stroke, the transit time that finishes in the predefined crank angle of end;

Described suction air quality is calculated unit (104), begins, finishes to hold bent axle to turn over the loss that function calculation that predefined crank angle institute's elapsed time and exhaust stroke begin, finish to hold bent axle to turn over the difference of predefined crank angle institute elapsed time goes out energy with described compression stroke.

4. fuel injection control system according to claim 3 is characterized in that,

Described suction air quality is calculated the unit, the beginning of use compression stroke, end end bent axle turn over the predefined crank angle elapsed time Tc1 of institute, Tc2 and exhaust stroke begins, finishes to hold bent axle to turn over the predefined crank angle elapsed time Te1 of institute, Te2, obtains the suction air quality with following function: suck air quality ∝ [{ (1/Tc1) ²-(1/Tc2) ²}-{ (1/Te1) ²-(1/Te2) ²].

5. fuel injection control system according to claim 2 is characterized in that,

Also comprise: calculate the unit (108) that is used to carry out the air density that described air density proofreaies and correct according to described suction air quality and normal air flowmeter.

6. fuel injection control system according to claim 2 is characterized in that,

Described low-load region is the no-load running zone, and control switching unit (109) comprises according to the rotation variance ratio of motor judges described no-load running zone and as the unit of the constant operation range beyond the low-load region.

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