JP4552700B2 - Engine fuel injection control device - Google Patents

Description

  The present invention controls the time for which the injector for supplying fuel to the engine to perform the fuel injection operation under various control conditions, so that the air-fuel ratio of the air-fuel mixture is set to an appropriate value in accordance with the surrounding environment and the engine operating condition. The present invention relates to a fuel injection control device for an engine that controls a fuel injection amount so as to keep the current at a constant value.

  As is well known, an engine fuel injection device includes an injector (electromagnetic fuel injection valve) attached to an intake pipe of an engine, a fuel pump that supplies fuel from a fuel tank to the injector, and a fuel pump that supplies the injector to the injector. And a fuel injection control device for controlling the amount of fuel injected from the injector (fuel injection amount) in order to maintain the air-fuel ratio of the air-fuel mixture at an appropriate value. In the engine fuel injection device, since the pressure of the fuel supplied to the injector is kept constant as described above, the fuel injection amount is managed by the time (injection time) during which the injector performs the fuel injection operation. .

  In an engine fuel control device, it is necessary to determine the intake air amount when determining the fuel injection time. An air flow meter is used as a means for obtaining the intake air amount. However, when it is necessary to reduce the cost or when the installation space of the air flow meter cannot be secured due to the structure of the engine, the air flow meter is used. Is often required to be omitted. Therefore, the intake air amount is estimated from the engine rotation speed, the intake pipe pressure, and the volumetric efficiency of the engine, and the injection time required to keep the air-fuel ratio at an appropriate value with respect to the estimated intake air amount is determined. The fuel injection control method, the throttle opening α of the engine, and the rotational speed N are used to estimate the intake air amount, and the injection required to keep the air-fuel ratio at an appropriate value for the estimated intake air amount. A fuel injection control method for determining time is used.

  The method of estimating the intake air amount using the engine speed and the intake pipe pressure and calculating the injection time required to keep the air-fuel ratio at an appropriate value for the estimated intake air amount is as follows: It is called a density system (hereinafter also referred to as an SD system). Further, a method for estimating the intake air amount from the throttle opening α of the engine and the rotational speed N and determining the injection time required to keep the air-fuel ratio at an appropriate value with respect to the estimated intake air amount is as follows: This is called a throttle speed method (hereinafter also referred to as α-N method).

  FIG. 2 shows the relationship between the intake pipe pressure P and throttle opening α of the 4-cycle engine and the load fluctuation. In the same figure, Pa and Pb indicate the intake pipe pressure during low-speed rotation and high-speed rotation of the engine, respectively, and αa and αb indicate the throttle opening during low-speed rotation and high-speed rotation of the engine, respectively.

  FIG. 3 shows the waveform of the intake pipe pressure observed during one combustion cycle of the engine. FIG. 3A shows the intake pipe pressure waveform when the engine is rotating at high speed under a high load. FIG. 4B shows an intake pipe pressure waveform when the engine is rotating at a high speed with a low load. As is apparent from these figures, during high-speed engine rotation, the pulsation of the intake pipe pressure is small when the load is small, but the pulsation of the intake pipe pressure is large when the load is large.

  In order to control the fuel injection amount with high accuracy by the SD method, the intake pipe pressure needs to show a large change with respect to the load fluctuation, and the pulsation of the intake pipe pressure detected during one combustion cycle is small. It is necessary. As is apparent from FIG. 2, the intake pipe pressure shows a linear change with respect to the load fluctuation both when the engine is rotating at a low speed and when the engine is rotating at a high speed. Even when the engine is rotating at high speed, the pulsation of the intake pipe pressure is small when the load is light. Therefore, at the time of low speed rotation and light load high speed rotation, the fuel injection amount can be controlled with high accuracy by the SD method. However, when the engine is rotating at a high speed in a high load state, as shown in FIG. 3A, the pulsation of the intake pipe pressure waveform increases throughout one combustion cycle. In the control, the fuel injection amount cannot be controlled with high accuracy.

  On the other hand, in the control by the α-N method, the fuel injection amount can be controlled with high accuracy when the amount of change of the throttle opening with respect to the load fluctuation is large. As is clear from FIG. 2, the throttle opening is small in the engine idling region and increases exponentially as the load increases. The injection amount can be accurately controlled. However, when the engine load is light, the amount of change in the throttle opening with respect to the load fluctuation is small, and it is difficult to accurately control the fuel injection amount by the control using the α-N method.

Therefore, as disclosed in Patent Document 1, it has been proposed to switch between the control based on the SD method and the control based on the α-N method according to the operating state of the engine. In the control disclosed in Patent Document 1, the fuel injection control is performed by the SD method when the engine load is small, and the fuel injection control is performed by the α-N method when the engine load is large.
JP-A-56-96132

  As described in Patent Document 1, if the control by the SD method and the control by the α-N method are switched according to the operating state of the engine, the engine can be operated at a low load or a high load. The fuel injection amount can be accurately controlled without using an air flow meter. However, when such control is performed, control by both methods may be switched in a state where there is a large difference in the injection time calculated by the SD method and α-N method. When the engine is switched, the fuel injection amount changes, and the output torque of the engine changes abruptly. As a result, the engine rotation changes abruptly, resulting in poor driving feeling.

  An object of the present invention is to provide a fuel injection control device for an engine that can smoothly switch between control using a speed density method and control using a throttle speed method without causing sudden torque fluctuations in the engine. There is to do.

  The present invention relates to an injection time determination unit that determines the actual injection time with respect to various control conditions, with the time during which the injector attached to the engine performs fuel injection at each injection timing as the actual injection time, and the injection time determination The present invention is applied to an engine fuel injection control device including an injector driving unit that drives an injector at each injection timing so as to cause the injector to perform fuel injection for an actual injection time determined by the unit.

In the present invention, the injection time determining unit is an injection time (speed density method) for setting the air-fuel ratio of the air-fuel mixture to an appropriate value with respect to the intake air amount estimated using the engine speed and the intake pipe pressure. The first injection time calculation means for calculating the first injection time as the first injection time, and the air-fuel ratio of the air-fuel mixture with respect to the intake air amount estimated using the throttle opening and the rotational speed of the engine A second injection time calculating means for calculating an injection time (an injection time calculated by the throttle speed method) for making the appropriate value as a second injection time, and a first injection time and a second injection time And an addition ratio determining means for determining an addition ratio used to calculate the actual injection time with respect to the throttle opening and the rotational speed of the engine, the first injection time and the second injection ratio. injection And the actual injection time calculating means for calculating a real-injection time at each injection timing by adding in addition ratio determined by the addition ratio determining means and between the addition ratio determined in order to calculate the actual injection time in each injection timing Whether the difference between the addition ratio newly determined by the means and the addition ratio determined by the addition ratio determination means in order to calculate the actual injection time at the previous injection timing exceeds a set limit value. When the addition ratio change amount determination means and the addition ratio change amount determination means determine that the difference of the addition ratio exceeds the limit value, the difference of the addition ratio is newly suppressed so as to be less than the limit value. Addition ratio adjusting means for adjusting the value of the determined addition ratio .

  Based on the results of the tests performed on the applied engine, the above-mentioned addition ratio is determined accurately regardless of the engine operating state, and does not show a rapid change. Set as follows. That is, in the process where the engine speed changes from low speed to high speed, and in the process where the throttle opening of the engine changes from the fully closed position to the fully open position at each rotational speed, the actual injection time is abrupt. A relationship among the rotational speed, the throttle opening degree, and the addition ratio is set so that an accurate value is determined without showing a change.

  In a preferred aspect of the present invention, when the engine speed is low and the throttle opening is small, the ratio of the first injection time to the actual injection time is increased and the ratio of the second injection time is decreased. When the engine speed is low and the throttle opening is large, the ratio of the first injection time to the actual injection time is reduced to increase the ratio of the second injection time, and the engine speed is When the throttle opening is small, the ratio of the first injection time to the actual injection time is increased to reduce the ratio of the second injection time, the engine speed is high, and the throttle opening is When the engine speed is large, the ratio of the engine speed, the throttle opening, and the addition ratio are reduced so that the ratio of the first injection time to the actual injection time is reduced and the ratio of the second injection time is increased. Is provided with map storage means for storing an addition ratio calculation map that defines the relationship between and the addition ratio determining means is configured to calculate the addition ratio by searching the addition ratio calculation map. .

  As described above, the actual injection time is determined by adding the injection time calculated by the speed density method and the injection time calculated by the throttle speed method at a predetermined addition rate. If the addition ratio is determined to an appropriate value with respect to the throttle opening and the rotational speed of the engine, the process of changing the rotational speed of the engine from a low speed to a high speed and when the throttle opening is fully closed at each rotational speed. In the process of changing from the opening degree to the opening degree when fully opened, the actual injection time can be adjusted to an appropriate value without a sudden change.

  If an addition ratio calculation map is created so that the engine addition ratio is properly determined with respect to the engine throttle opening and rotation speed, the injection time will change drastically and the engine output torque will change suddenly. In order to reliably prevent a sudden change in output torque due to a large change in the injection time, the injection time determination unit is provided with an addition ratio determination means for calculating the actual injection time at each injection timing. It is determined whether the difference between the newly added addition ratio and the addition ratio determined by the addition ratio determining means for calculating the actual injection time at the previous injection timing exceeds a set limit value. When the addition ratio change amount determining means and the addition ratio change amount determining means determine that the difference of the addition ratio exceeds the limit value, the difference of the addition ratio is less than the limit value. Further it is preferable to provide the addition ratio adjustment means for adjusting the newly determined value of the addition ratio so as to suppress.

  If configured in this way, even if the addition ratio shows a significant change, it is possible to prevent a significant change in the injection time, so the SD method and the α-N method are switched. In this case, it is possible to prevent a situation in which the output torque of the engine changes suddenly and cause discomfort to the driver.

  In another preferable aspect of the present invention, the injection time determining unit estimates the amount of air sucked into the engine using the engine speed and the intake pipe pressure as the first intake air amount. Estimating means; second intake air amount estimating means for estimating the amount of air sucked into the engine as the second intake air amount using the throttle opening and rotation speed of the engine; and the first intake air amount And the second intake air amount are added at a predetermined ratio to determine the addition ratio used to calculate the actual injection time calculation intake air amount with respect to the throttle opening and the rotational speed of the engine. The actual intake time calculating intake air by calculating the actual injection time calculating intake air amount by adding the first intake air amount and the second intake air amount at the adding ratio determined by the adding ratio determining means. Air amount calculation means; And a real injection time calculating means for calculating a real-injection time at each injection timing with respect to the injection time calculation intake air amount.

  As described above, the intake air amount for calculating the actual injection time is determined by adding the intake air amount calculated by the speed density method and the intake air amount calculated by the throttle speed method at a predetermined addition rate. In addition, even when the addition ratio is determined to be an appropriate value for the throttle opening and the rotational speed of the engine, the process of changing the rotational speed of the engine from a low speed to a high speed and each rotational speed In the process in which the throttle opening changes from the fully open position to the fully open position, the actual injection time can be adjusted to an appropriate value without a sudden change.

  As described above, the injection is performed even when the first intake air amount and the second intake air amount are added at a predetermined addition ratio to obtain the intake air amount used for calculating the actual injection time. The time determination unit is configured to calculate the actual injection time for calculating the actual injection time at each injection timing, the addition ratio newly determined by the addition ratio determination means to calculate the actual injection time calculation intake air amount, and the previous injection timing. It is determined whether or not the difference from the addition ratio determined by the addition ratio determining means for calculating the actual injection time calculating intake air amount used when calculating the actual injection time exceeds a set limit value. When the addition ratio change amount determination means and the addition ratio change amount determination means determine that the difference in the addition ratio exceeds the limit value, a new determination is made to suppress the difference in the addition ratio below the limit value. Taca Preferably, a structure in which an adding ratio adjusting means for adjusting the value of the ratio.

  In a preferred aspect of the present invention, when the engine speed is low and the throttle opening is small, the ratio of the first intake air amount to the actual intake time calculation intake air amount is increased to increase the second intake air. The ratio of the first intake air amount to the intake air amount for calculating the actual injection time is decreased when the ratio of the air amount is reduced, the engine speed is low, and the throttle opening is large. Increasing the proportion of the intake air amount, increasing the proportion of the first intake air amount relative to the intake air amount for calculating the actual injection time when the engine speed is high and the throttle opening is small. When the engine speed is high and the throttle opening is large, the ratio of the first intake air amount to the intake air amount for calculating the actual injection time is reduced. 2 A map storage means for storing an addition rate calculation map that defines the relationship among the engine speed, the throttle opening, and the addition rate so as to increase the proportion of the intake air amount is provided. The addition rate determining means is configured to calculate the addition rate by searching for.

  As described above, the addition ratio used for calculating the intake air amount for calculating the actual injection time by adding the first intake air amount and the second intake air amount at a predetermined ratio is also different for the engine to be applied. Based on the results of the tests performed in this way, the actual injection time calculation intake air amount is accurately determined and set so as not to show a sudden change, regardless of the engine operating state. That is, in the process of changing the engine speed from low speed to high speed, and in the process of changing the throttle opening of the engine from the fully open position to the fully open position at each rotational speed, the actual injection time calculation intake The relationship between the rotational speed, the throttle opening, and the addition ratio is set so that the air amount is determined to an appropriate value without showing a rapid change.

  As described above, according to the present invention, the first injection time calculated for the intake air amount estimated by the speed density method and the intake air amount estimated by the throttle speed method are calculated. A ratio of addition to the determined second injection time is determined with respect to the throttle opening and the rotational speed of the engine, and the first injection time and the second injection time are added at the determined addition ratio. To determine the actual injection time or to determine the addition ratio of the first intake air amount estimated by the speed density method and the second intake air amount estimated by the throttle speed method to the throttle opening of the engine And the rotation speed, and the actual injection time is calculated using the intake air amount obtained by adding the first intake air amount and the second intake air amount at the determined addition rate. Therefore, by setting the addition ratio to an appropriate value for each rotational speed and throttle opening, the throttle opening is fully adjusted in the process of changing the engine rotational speed from low to high and at each rotational speed. In the process of changing from the opening degree at the time of closing to the opening degree at the time of full opening, the actual injection time can be adjusted to an appropriate value without accompanying a sudden change. Therefore, according to the present invention, high engine performance is achieved by accurately controlling the fuel injection amount from low load and low speed to high load and high speed without causing a shock that causes the driver to feel uncomfortable. Can be pulled out.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 schematically shows a configuration of an embodiment of the present invention, in which 1 is an engine and 2 is a fuel injection control device. The engine 1 includes a cylinder 101 and a crankcase 102, a piston 103 disposed in the cylinder 101, a crankshaft 105 connected to the piston 103 via a connecting rod 104, an intake pipe 106, and an exhaust pipe 107. A throttle valve 108 is attached to the intake pipe 106. A spark plug 109 is attached to the cylinder head of the engine, and an injector 110 is attached to the intake pipe 106. The injector 110 is attached so as to inject fuel into a space downstream of the throttle valve in the intake pipe 106, and fuel is supplied to the injector 110 from a fuel tank (not shown) via a fuel pump. The pressure of the fuel supplied to the injector is kept constant by a pressure regulator.

  The engine crankshaft 105 is provided with a flywheel 111 having a reluctator r formed on the outer periphery, and detects a front end edge and a rear end side edge in the rotation direction of the reluctator r in the vicinity of the flywheel 111 to generate pulses. A signal generator 3 for generating a signal is arranged. Further, the pressure sensor 4 for detecting the internal pressure (intake pipe pressure) is attached to the intake pipe 106, and the throttle sensor 5 for detecting the throttle opening is attached to the throttle valve 108.

  The fuel injection control device 2 has an injection time determination unit 2A for determining the actual injection time with respect to various control conditions, with the time for causing the injector attached to the engine to perform fuel injection at each injection timing as the actual injection time; And an injector driving unit 2B that drives the injector 110 at each injection timing so as to cause the injector 110 to inject fuel during the actual injection time determined by the injection time determining unit.

  The injection time determination unit 2A includes a rotation speed calculation unit 200 configured by causing a microprocessor to execute a predetermined program, a first injection time calculation unit 201, a second injection time calculation unit 202, and an addition ratio. Determination means 203 and actual injection time calculation means 204 are provided.

The rotational speed calculation means 200 calculates the rotational speed N of the engine by measuring the generation interval of the pulse signal generated by the signal generator 3.

  The first injection time calculation means 201 is estimated (by the SD method) using the rotation speed N of the engine 1 calculated by the rotation speed calculation means 200 and the intake pipe pressure P detected by the pressure sensor 4. The injection time for setting the air-fuel ratio of the air-fuel mixture to an appropriate value with respect to the intake air amount is calculated as the first injection time Ti1.

  Further, the second injection time calculation means 202 sets the air-fuel ratio of the air-fuel mixture to an appropriate value with respect to the intake air amount estimated using the throttle opening α and the rotational speed N of the engine 1 (by the α-N method). The injection time for this is calculated as the second injection time Ti2.

  In the present invention, instead of selectively switching between the first injection time Ti1 and the second injection time Ti2 calculated as described above, these injection times Ti1 and Ti2 are used as the throttle opening. The actual injection time is obtained by adding the α and the rotation speed N at an addition ratio determined to an appropriate value.

In FIG. 1, the addition ratio determining means 203 adds the first injection time Ti1 and the second injection time Ti2 at a predetermined ratio to calculate the addition ratio β used to calculate the actual injection time Ti. The actual injection time calculation means 204 adds the first injection time Ti1 and the second injection time Ti2 at the addition ratio determined by the addition ratio determination means. This is a means for calculating the actual injection time Ti at each injection timing. The addition ratio determination means 203 of the present embodiment calculates the ratio of the second injection time Ti2 to the actual injection time Ti as the addition ratio β, and the actual injection time calculation means 204 The actual injection time Ti is calculated by the following equation using the ratio β.
Ti = (1-.beta.). Ti1 + .beta..Ti2 (1)

  In the present embodiment, as shown in FIG. 6, there is provided map storage means for storing an addition rate calculation map that defines the relationship among the engine speed N, the throttle opening α, and the addition rate β in the ROM. It has been. This map shows rotational speeds N1, N2,... (N1 <N2 <...), throttle openings α1, α2,... (Α1 <α2 <...) and additions corresponding to these rotational speeds and throttle openings. The ratios β11, β12,..., Β21, β22,..., Β31, β32,..., Β41, β42,. The addition ratio β is calculated with respect to the engine speed and the throttle opening by searching the map for interpolation.

  , Β21, β22,..., Β31, β32,..., Β41, β42,... Constituting the addition ratio calculation map shown in FIG. It is determined appropriately based on

  As described above, when the intake air amount is estimated by the SD method, when the engine is rotating at a low speed and when the engine is rotating at a high speed with a light load, the fuel injection amount is accurately determined. However, when the engine is rotating at high speed with a high load, the pulsation of the intake pipe pressure waveform increases throughout the combustion cycle. become unable.

  On the other hand, when the intake air amount is estimated by the α-N method, the control of the fuel injection amount is accurately performed when the change amount of the throttle opening with respect to the load fluctuation is large, that is, at a high engine load. Can be done.

  Therefore, the addition ratios β11, β12,..., Β21, β22,..., Β31, β32,..., Β41, β42, etc. constituting the addition ratio calculation map have a low engine speed N and a small throttle opening. Occasionally, the ratio (1-β) of the first injection time Ti1 to the actual injection time Ti is increased and the ratio β of the second injection time Ti2 to the actual injection time is decreased, and the engine rotation When the speed N is low and the throttle opening α is large, the ratio (1-β) of the first injection time Ti1 to the actual injection time Ti is reduced so that the second injection time Ti2 is smaller than the actual injection time. The ratio (1-β) occupied by the first injection time Ti1 with respect to the actual injection time Ti is increased when the engine speed N is high and the throttle opening α is small. 2 Reduce the ratio β of the injection time Ti2 to the actual injection time, The ratio (1-β) of the first injection time Ti1 to the actual injection time Ti when the rotational speed N of the engine is high and the throttle opening α is large is reduced to the ratio of the second injection time Ti2 It is preferable to set β to be large.

  The injector drive unit 2B includes an injection command pulse generating means for generating an injection command pulse having a pulse width necessary for injecting fuel from the injector during the actual injection time Ti calculated by the actual injection time calculating means 204, and the injection An injector drive circuit that allows a drive current to flow through the solenoid of the injector 110 while the command pulse is generated opens the valve of the injector 110 and injects fuel from the injector during the actual injection time Ti.

  In order to constitute the first injection time calculation means 201, the second injection time calculation means 202, the addition ratio determination means 203, and the actual injection time calculation means 204, a microprocessor is used once per combustion cycle of the engine. FIG. 4 shows a flowchart showing an algorithm of the injection time calculation process to be executed.

  In the case of this algorithm, in step 01, the injection time required to keep the air-fuel ratio of the air-fuel mixture at an appropriate value with respect to the intake air amount estimated by the SD method is calculated as the first injection time Ti1. Then, the injection time required to maintain the air-fuel ratio of the air-fuel mixture at an appropriate value with respect to the intake air amount estimated by the α-N method in step 02 is calculated as the second injection time Ti2. Next, in step 03, the addition rate β is calculated by searching the addition rate calculation map for the throttle opening α and the rotational speed N, and in step 04, the previously calculated addition rate β is calculated. Using the absolute value of the difference from the ratio β as the addition ratio change amount, it is determined whether or not the addition ratio change amount exceeds the limit value LMT. As a result, when it is determined that the addition rate change amount exceeds the limit value, the process proceeds to step 05, where it is determined whether or not the currently calculated addition rate β is larger than the previously calculated addition rate β. When it is determined by this determination that the addition ratio β calculated this time is larger than the addition ratio β calculated last time, the process proceeds to step 06 and the value obtained by adding the limit value LMT to the addition ratio calculated last time is calculated. Let the addition ratio β. If it is determined in step 05 that the addition ratio β calculated this time is equal to or less than the addition ratio β calculated last time, a value obtained by subtracting the limit value LMT from the addition ratio β calculated last time is set as the current addition ratio. . After the current addition ratio β is obtained in step 06 or 07, the process proceeds to step 08, where the actual injection time Ti is calculated by the above equation (1) and this process is terminated.

  In the case of the algorithm shown in FIG. 4, in step 01, the injection time required to keep the air-fuel ratio of the air-fuel mixture at an appropriate value with respect to the intake air amount estimated by the SD method is the first injection time. The first injection time calculation means 201 that calculates as Ti1 is configured, and in step 02, the injection time necessary for maintaining the air-fuel ratio of the air-fuel mixture at an appropriate value with respect to the intake air amount estimated by the α-N method is set. Second injection time calculation means for calculating as the second injection time Ti2 is configured.

  Further, in step 03, the first injection time Ti1 and the second injection time Ti2 are added at a predetermined ratio, and the addition ratio used for calculating the actual injection time is calculated with respect to the engine throttle opening and the rotational speed. In step 08, the first injection time and the second injection time are added at the addition ratio determined by the addition ratio determination means, and the actual injection at each injection timing is determined. An actual injection time calculating means 204 for calculating the time Ti is configured.

  Further, in the example shown in FIG. 4, in step 04, the addition ratio newly determined by the addition ratio determining means 203 for calculating the actual injection time at each injection timing and the actual injection time at the previous injection timing are calculated. Therefore, an addition rate change amount determination unit is configured to determine whether or not the difference from the addition rate determined by the addition rate determination unit exceeds a set limit value, and the addition rate change amount determination unit determines the addition rate. When it is determined that the difference between the two exceeds the limit value, the addition ratio adjusting means adjusts the value of the newly determined addition ratio so as to suppress the difference between the addition ratios below the limit value in steps 05 to 07. Is configured.

  As described above, the actual injection time is determined by adding the injection time calculated by the speed density method and the injection time calculated by the throttle speed method at a predetermined addition ratio. If the ratio is determined appropriately with respect to the throttle opening and the rotational speed of the engine, the process of changing the rotational speed of the engine from low speed to high speed and the opening of the throttle opening when fully closed at each rotational speed. Since the actual injection time can be adjusted to an appropriate value without a sudden change in the process of changing from the degree of opening to the fully opened position, it is possible to reduce the load without causing a shock to the driver. It is possible to bring out the high performance of the engine by accurately controlling the fuel injection amount from the low rotation time to the high load high rotation time.

  Further, as in the example shown in FIG. 4, when the addition ratio change amount determination means determines that the difference in the addition ratio exceeds the limit value, the difference in the addition ratio is newly set to be less than the limit value. If an addition rate adjustment means is provided to adjust the value of the determined addition rate, an operating condition that was not expected in the actual machine test when creating the addition rate calculation map will occur, and the addition rate will change significantly. Therefore, the change can be suppressed, so that it is possible to more reliably prevent the engine output torque from fluctuating due to a significant change in the injection time.

In the above example, the ratio of the second injection time Ti2 to the actual injection time Ti is calculated as the addition ratio β, and the actual injection time is calculated by the above equation (1). The ratio of the injection time Ti1 to the actual injection time Ti may be calculated as the addition ratio β, and the actual injection time Ti may be calculated by the following equation.
Ti = β · Ti1 + (1−β) · Ti2 (2)

  In the above embodiment, the first injection time calculated with respect to the intake air amount estimated by the speed density method and the second injection time calculated with respect to the intake air amount estimated by the throttle speed method. An addition ratio with the injection time is determined with respect to the throttle opening and the rotational speed of the engine, and the actual injection time is obtained by adding the first injection time and the second injection time with the determined addition ratio. The ratio of addition of the first intake air amount estimated by the speed density method and the second intake air amount estimated by the throttle speed method is determined as the throttle opening and the rotational speed of the engine. And the actual injection time is calculated using the intake air amount obtained by adding the first intake air amount and the second intake air amount at the determined addition ratio. It may be.

  An addition ratio between the first intake air amount estimated by the speed density method and the second intake air amount estimated by the throttle speed method is determined with respect to the throttle opening and the rotational speed of the engine, An algorithm of processing executed by the microprocessor when the intake air amount used for the calculation of the actual injection time is obtained by adding the first intake air amount and the second intake air amount at the determined addition ratio A flowchart showing the above is shown in FIG.

In the case of the algorithm shown in FIG. 5, in step 11, the intake air amount of the engine is estimated with respect to the intake air amount estimated by the SD method, and this intake air amount is referred to as the first intake air amount A1. To do. In step 12, the intake air amount is estimated by the α-N method, and this intake air amount is set as a second intake air amount A2. Next, at step 13, an addition ratio β is calculated by searching an addition ratio calculation map for the throttle opening α and the rotation speed N, and at step 14, the addition ratio β calculated this time and the previously calculated addition ratio are calculated. Using the absolute value of the difference from the ratio β as the addition ratio change amount, it is determined whether or not the addition ratio change amount exceeds the limit value LMT. As a result, when it is determined that the addition rate change amount exceeds the limit value, the process proceeds to step 15 to determine whether or not the currently calculated addition rate β is larger than the previously calculated addition rate β. When it is determined by this determination that the addition ratio β calculated this time is larger than the addition ratio β calculated last time, the process proceeds to step 16 and the value obtained by adding the limit value LMT to the addition ratio calculated last time is calculated. Let the addition ratio β. When it is determined in step 15 that the addition ratio β calculated this time is less than or equal to the previously calculated addition ratio β, a value obtained by subtracting the limit value LMT from the previously calculated addition ratio β in step 17 is added to the current addition. A percentage. After the current addition ratio β is obtained in step 16 or 17, the process proceeds to step 18, and the actual injection time calculating intake air amount A is calculated by the following equation.
A = (1-β) A1 + βA2 (3)
Next, at step 19, the actual injection time Ti is calculated for the intake air amount A, and this process is terminated.

  In the case of the algorithm shown in FIG. 5, in step 11, the intake air amount of the engine is estimated as the first intake air amount by the SD method (using the engine rotational speed and the intake pipe pressure). The first intake air amount estimation means is configured, and in step 12, the intake air amount of the engine is estimated as the second intake air amount by the α-N method (using the throttle opening and the rotational speed of the engine). Two intake air amount estimation means are configured.

  Further, at step 13, the first intake air amount and the second intake air amount are added at a predetermined ratio, and the addition ratio used for calculating the actual injection time calculation intake air amount is set as the engine throttle opening. An addition ratio determining means for determining the rotational speed is configured. Further, in step 18, an actual injection time calculation for calculating the intake air amount for calculating the actual injection time by adding the first intake air amount and the second intake air amount at the addition ratio determined by the addition ratio determining means. The intake air amount calculating means is configured, and the actual injection time calculating means for calculating the actual injection time at each injection timing with respect to the intake air amount for calculating the actual injection time is constituted by step 19.

  Further, in the example shown in FIG. 5, in step 14, the addition newly determined by the addition ratio determining means for calculating the actual injection time calculating intake air amount used when calculating the actual injection time at each injection timing. A limit value in which a difference between the ratio and the addition ratio determined by the addition ratio determination means for calculating the actual injection time calculation intake air amount used when calculating the actual injection time at the previous injection timing is set. An addition ratio change amount determination means for determining whether or not the addition ratio has been configured, and when the addition ratio change amount determination means determines in steps 15 to 16 that the difference in addition ratio exceeds the limit value, the addition ratio Addition ratio adjusting means for adjusting the newly determined addition ratio value so as to keep the difference between the two values below the limit value is configured.

In the above example, the ratio of the second intake air amount A2 to the actual injection time calculation intake air amount A is calculated as the addition ratio β, and the actual injection time calculation intake air amount is calculated according to the equation (3). A is calculated, but the ratio of the first intake air amount A1 to the actual injection time calculation intake air amount A is calculated as an addition ratio β, and the actual injection time calculation intake is calculated according to the following equation. The air amount A may be calculated.
A = β · A1 + (1−β) · A2 (4)

  In the above embodiment, a single cylinder engine is taken as an example, but the present invention can of course be applied to a multi-cylinder engine.

It is the block diagram which showed schematically the structure of one Embodiment of this invention. 3 is a graph showing the relationship between intake pipe pressure and load and the relationship between throttle opening and load of a 4-cycle engine. (A) and (B) are waveform diagrams showing intake pipe pressure waveforms when the engine is at high load and high speed and at high load and low speed, respectively. 3 is a flowchart showing an example of an algorithm for an injection time calculation process executed by a microprocessor in the embodiment of the present invention. 6 is a flowchart showing an example of an algorithm of an injection time calculation process executed by a microprocessor in another embodiment of the present invention. It is the chart which showed the structure of the map for addition ratio calculation.

DESCRIPTION OF SYMBOLS 1 Engine 108 Throttle valve 110 Injector 2 Fuel injection control apparatus 3 Signal generator 4 Pressure sensor 5 Throttle sensor 2A Injection time determination part 201 1st injection time calculation means 202 2nd injection time calculation means 203 Addition ratio determination means 204 Actual Injection time calculation means

Claims (5)

An injection time determination unit that determines the actual injection time with respect to various control conditions, with the time during which the injector attached to the engine performs fuel injection at each injection timing as the actual injection time, and the injection time determination unit A fuel injection control device for an engine comprising an injector driving unit that drives the injector at each injection timing so as to cause the injector to inject fuel during the actual injection time;
The injection time determination unit is
First injection time calculation for calculating, as a first injection time, an injection time for setting the air-fuel ratio of the air-fuel mixture to an appropriate value with respect to the intake air amount estimated using the rotation speed of the engine and the intake pipe pressure Means,
Second injection time calculation for calculating, as a second injection time, an injection time for setting the air-fuel ratio of the air-fuel mixture to an appropriate value with respect to the intake air amount estimated using the throttle opening and the rotational speed of the engine Means,
An addition for determining an addition ratio used to calculate the actual injection time by adding the first injection time and the second injection time at a predetermined ratio to the throttle opening and the rotational speed of the engine. A ratio determining means;
Actual injection time calculation means for calculating the actual injection time at each injection timing by adding the first injection time and the second injection time at an addition ratio determined by the addition ratio determination means ;
The addition ratio newly determined by the addition ratio determination means for calculating the actual injection time at each injection timing and the addition determined by the addition ratio determination means for calculating the actual injection time at the previous injection timing An addition ratio change amount determination means for determining whether or not the difference with the ratio exceeds a set limit value;
A value of the addition ratio newly determined so as to suppress the difference of the addition ratio below the limit value when the addition ratio change amount determination unit determines that the difference of the addition ratio exceeds the limit value. An addition ratio adjusting means for adjusting
An engine fuel injection control device comprising: When the rotational speed of the engine is low and the throttle opening is small, the ratio of the first injection time to the actual injection time is increased to reduce the ratio of the second injection time, When the engine speed is low and the throttle opening is large, the ratio of the first injection time to the actual injection time is reduced to increase the ratio of the second injection time, and the engine When the rotation speed of the engine is high and the throttle opening is small, the ratio of the first injection time to the actual injection time is increased to decrease the ratio of the second injection time, and the rotation of the engine When the speed is high and the throttle opening is large, the ratio of the first injection time to the actual injection time is reduced to increase the ratio of the second injection time. Map storage means for storing addition ratio calculation map defining the relationship between the rotational speed and the throttle opening and the addition ratio of the engine is provided,
The engine fuel injection control device according to claim 1, wherein the addition ratio determining means is configured to calculate the addition ratio by searching the addition ratio calculation map. An injection time determination unit that determines the actual injection time with respect to various control conditions, with the time during which the injector attached to the engine performs fuel injection at each injection timing as the actual injection time, and the injection time determination unit A fuel injection control device for an engine comprising an injector driving unit that drives the injector at each injection timing so as to cause the injector to inject fuel during the actual injection time;
The injection time determination unit includes a first intake air amount estimation unit that estimates an amount of air sucked into the engine as a first intake air amount using a rotation speed of the engine and an intake pipe pressure; Second intake air amount estimating means for estimating the amount of air sucked into the engine as a second intake air amount using the throttle opening and the rotational speed of the engine; and the first intake air amount and the first intake air amount 2 is added to the intake air amount at a predetermined rate to determine the addition rate used to calculate the intake air amount for calculating the actual injection time with respect to the throttle opening and the rotational speed of the engine. And an actual injection time calculation for calculating the actual injection time calculation intake air amount by adding the first intake air amount and the second intake air amount at the addition rate determined by the addition rate determination means Intake air volume Calculation means and the actual injection time for calculating the intake air amount to calculate the actual injection time in each injection timing actual injection time calculation means and the fuel injection control apparatus for an engine equipped with. The injection time determination unit is
  The addition ratio newly determined by the addition ratio determination means for calculating the actual injection time calculation intake air amount used when calculating the actual injection time at each injection timing, and the actual injection time at the previous injection timing Addition rate change for determining whether or not the difference from the addition rate determined by the addition rate determining means for calculating the actual injection time calculation intake air amount used for the calculation exceeds a set limit value A quantity determination means;
A value of the addition ratio newly determined so as to suppress the difference of the addition ratio below the limit value when the addition ratio change amount determination unit determines that the difference of the addition ratio exceeds the limit value. An addition ratio adjusting means for adjusting
The engine fuel injection control device according to claim 3, further comprising: When the rotational speed of the engine is low and the throttle opening is small, the ratio of the first intake air amount to the actual intake time calculation intake air amount is increased to increase the second intake air amount. The ratio of the first intake air amount to the actual injection time calculation intake air amount is reduced when the engine speed is low and the throttle opening is large. The ratio of the first intake air amount to the intake air amount for the actual injection time calculation when the ratio of the second intake air amount is increased, the engine speed is high, and the throttle opening is small Is increased to reduce the proportion of the second intake air amount, and when the engine speed is high and the throttle opening is large, the first intake air amount for the actual injection time calculation is large. Addition ratio calculation defining the relationship between the engine speed, the throttle opening, and the addition ratio so that the ratio occupied by the intake air amount is reduced and the ratio occupied by the second intake air amount is increased. Map storage means for storing a map for use is provided,
The engine fuel injection control device according to claim 3 or 4, wherein the addition ratio determining means is configured to calculate the addition ratio by searching the addition ratio calculation map.

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