Fuel injection control device for internal combustion engine

Abstract: A fuel injection control device controls the calculate fuel injection quantity depending upon the load condition of the engine such that the fuel injection quantity demanded by the engine can be established. This fuel injection quantity is determined based upon engine speed, intake air temperature, engine temperature, the atmospheric pressure of the intake air, and the throttle opening. When the detected intake air temperature is high for a high load condition of the engine, an intake air temperature correction factor is set such that the intake air temperature is less influential upon the establishment of the fuel injection quantity. Moreover, during acceleration, an acceleration incremental fuel injection quantity is calculated based upon different water temperature correction factors. When an engine temperature is low, the fuel injection quantity demanded by the engine is very large. Accordingly, the fuel injection control device utilizes a second water temperature correction factor which is set to be larger than a first water temperature correction factor at low engine temperatures. Thus, the fuel injection quantity for acceleration of the engine at low engine temperatures can be established in accordance with the demand by the engine.

Description: Field of the Present Invention The present invention relates to a fuel injection control device and method for an internal combustion engine as set forth in independant claims 1 and 6, and more particularly, to fuel injection control device for an internal combustion engine wherein a fuel injection quantity is controlled according to an intake air temperature. Backaround of the Present Invention Conventionally, various fuel injection control devices for internal combustion engines have been designed. For example, in Japanese Patent Laid Open Publication Number 59-176427, a fuel injection control device has been developed to control a fuel injection quantity according to an intake air temperature. The fuel injection quantity is corrected, so as to compensate for a difference in density of the intake air due to a temperature difference thereof. The correction value of the fuel injection quantity according to the intake air temperature is determined based upon an output signal from an intake air temperature sensor provided in an air cleaner, for example. While idling or running with a very low load with respect to the internal combustion engine, the intake air flow is relatively small, and thus, the temperature of a temperature detecting portion of the intake air temperature sensor accurately corresponds with the actual intake air temperature. On the other hand, when the engine becomes hot as in a high load condition, the temperature of the temperature detecting portion of the intake air temperature sensor can read a very high temperature due to the influence of the high ambient temperature around the sensor even though the actual intake air temperature is not as high due to the large intake air flow. More specifically, when an intake air temperature is detected by the intake air temperature sensor during a high load condition, the detected intake air temperature is actually higher than the actual intake air temperature. As a result, if the corrected value of the fuel injection quantity is determined based upon the detected intake air temperature only, a problem exist such that the fuel injection quantity according to the detected intake air temperature during a high load condition is different from a fuel injection quantity which would be corrected on demand by the engine if the actual intake air temperature was detected. Another example of a fuel injection control device for an internal combustion engine is set forth in Japanese Patent Publication Number 63-14173. This fuel injection control device improves in acceleration performance by increasing a fuel injection quantity during acceleration of an internal combustion engine. This technique utilizes a threshold value for determining acceleration that is variable according to engine temperature. The fuel injection quantity is increased according to the determination of the acceleration. In contrast, another technique for adjusting the acceleration incremental injection quantity according to an engine temperature utilizes a water temperature correction factor. In this technique, a fuel injection quantity, during normal running of an engine, is usually corrected by utilizing a water temperature correction factor set according to an engine temperature. The acceleration incremental injection quantity is corrected utilizing this water temperature correction factor. However, utilizing such a correction technique, the fuel injection quantity for normal running of an internal combustion engine and the acceleration incremental injection quantity are corrected utilizing the same water temperature correction factor. In other words, the temperature correction factor used during normal running of an internal combustion engine is used during acceleration or transient running of the engine. Accordingly, this type of correction technique is not desirable in a motorcycle in which acceleration performance is considered an important feature. More specifically, when utilizing this correction technique, the fuel injection quantity which is computed utilizing the correction factors stated above, it is quite different from the actual fuel injection quantity demanded by the engine. From US-PS 4,495,925 a device for an intake air temperature dependent correction of the air/fuel ratio for internal combustion engines is known. The device of this disclosure is capable of correcting a fundamental air/fuel ratio in dependence on the intake air temperature and the correction is intended to be carried out after the engine warm-up. An intake air temperature correction factor is set such as to decrease with an increase in intake air temperature. However, in this device the air/fuel ratio which is to be injected into the internal combustion engine is corrected with respect to the intake air temperature without taking account of the actual load condition of the internal combustion engine. it is, therefore, an object of the present invention to provide a fuel injection control device for an internal combustion engine which is capable of providing a fuel amount for an internal combustion engine which is in accordance with an actual demand by the engine. This object is solved by the fuel injection control device and method according to independent claims 1 and 6, respectively. According to the present invention, an intake air temperature correction factor is set according to an intake air temperature and whether the internal combustion engine is in a low load condition or a high load condition. Furthermore, after the intake air temperature exceeds a predetermined temperature, the intake air temperature correction factor set for the high load condition is less influenced by the intake air temperature than the intake air temperature correction factor when set for the low load condition. The intake air temperature correction factor set for the high load condition may be a fixed value after the intake air temperature exceeds the predetermined temperature. When an internal combustion engine is at a high load condition, and the intake air temperature is greater than a predetermined temperature, the intake air temperature correction factor is set to be less influenced by the intake air temperature. Brief Description of the Drawings Other objects and advantages of the present invention will become more apparent from the detailed description of the preferred embodiments with reference to the accompanying drawings wherein: Figure 1 is a block diagram of one embodiment of the present invention; Figure 2 is a schematic diagram of the overview of the present invention; Figure 3 is a flow chart illustrating the operations of one preferred embodiment of the present invention; Figure 4 is a block diagram illustrating the various symbols to be utilized in the description of the present invention and schematically illustrating a process for calculating a fuel injection quantity T out ; Figure 5 is a graph illustrating the contents of K tw1 Table, K tw2 Table, and K twt Table; Figure 6 is a flow chart illustrating the process for selecting either the K tw1 Table, or the K tw2 Table; Figure 7 is a graph illustrating the contents of K ta1 Table and K ta2 Table; Figure 8 is a flow chart illustrating the process for selecting either the K a1 Table or the K ta2 Table; Figure 9 is graph illustrating the contents of a K pa Table; Figure 10 is a graph illustrating the contents of a K ast Table; Figure 11 is graph illustrating the contents of an N e-th map; Figure 12 is a graph illustrating the contents of an N e -P b map; Figure 13 is a graph illustrating the relationship between a throttle opening th in an engine speed N e for selecting either the N e-th map or the N e-Pb map; Figure 14 is a graph illustrating the contents of a T v Table; Figure 15 is a block diagram of a preferred embodiment of the present invention; Figure 16 is a block diagram illustrating the details of the load determining means illustrated in Figure 15; Figure 17 is a flow chart illustrating another preferred embodiment for the selection of either the K ta1 Table or the K ta2 Table; and Figure 18 is a block diagram showing a part of the block diagramm of Fig. 15 in a simplified manner. Detailed Description of the Preferred Embodiments of the Present Invention In the drawings, like reference numerals designate like parts throughout the drawings. Figure 2 is schematic drawing of the preferred embodiment of the present invention. In Figure 2, an air cleaner 56 is provided in the vicinity of the engine. Within the air cleaner 56, an intake air temperature sensor 1 is positioned to detect the intake air temperature T a . Also, in the air cleaner 56 is an intake air pressure sensor 7 for detecting the intake air pressure P b . An air inlet for the air cleaner 56 is provided at a side portion of the air cleaner 56. A throttle valve is provided in the intake air passage leading from the air cleaner 56 to the engine. An injector 29 is provided in the vicinity of the throttle valve. A throttle opening sensor 3 for detecting a throttle opening  th is connected to a rotating shaft of the throttle valve. The engine is provided with a cooling water temperature sensor 4 for detecting a cooling water temperature T w . The engine is also provided with a crank pulser to be located in the vicinity of a crank shaft 55 for generating crank pulses to compute the engine speed N e and execute a crank interruption process. Lastly, the engine includes a cam pulser 54 located in the vicinity of a cam shaft 53 for generating T dc pulses. Output signal from the above sensors and pulsers are inputted into an electronic control unit (ECU) 60. Furthermore, an atmospheric pressure P a outputted from an atmospheric pressure sensor 5 and a voltage of a battery 8 (V b ) are also inputted to the electronic control unit 60. The ECU 60 is provided with a microcomputer to compute a fuel injection quantity T out utilizing the method described above and controls the injector 29 through the utilization of the fuel injection quantity T out . Although not directly related to the present invention, the ECU 60 also performs control functions with respect to a fuel pump 52 provided in a fuel tank 51 and control functions with respect to an opening of an intake air duct 57 provided in the air cleaner 56. The operation of a preferred embodiment of the present invention will be described in detail with reference to Figure 3. The process illustrated in Figure 3 is executed upon an interruption of the crank pulses. It is noted that the various symbols referred to below correspond to the following values. More specifically, T out represents a fuel injection quantity; T im represents a fundamental fuel injection quantity; K total represents a first fundamental fuel injection quantity correction factor; K tw represents a first water temperature correction factor; K ta represents an intake air temperature correction factor; K pa represents an atmospheric pressure control factor; K ast represents a second fundamental fuel injection quantity correction factor; T acc represents an acceleration incremental fuel injection quantity; K acc represents an acceleration incremental injection quantity correction factor; K twt represents a second water temperature correction factor; and T v represents a voltage incremental injection quantity. As schematically shown in Figure 4, the fuel injection quantity T out is calculated from the fundamental fuel injection quantity T im , the acceleration incremental fuel injection quantity T acc , and the voltage incremental injection quantity T v . The fundamental fuel injection quantity T im is corrected utilizing the first fundamental fuel injection quantity correction factor K total and the second fundamental fuel injection quantity correction factor K ast . The acceleration incremental fuel injection quantity T acc is corrected by utilizing the acceleration incremental fuel injection quantity correction factor K acc . Furthermore, the first fundamental fuel injection quantity correction factor K total is calculated by using the first water temperature correction factor K tw , the intake air temperature correction factor K ta , and the atmospheric pressure correction factor K pa . The acceleration incremental injection quantity correction factor K acc is calculated by utilizing the second water temperature correction factor K twt , the intake air temperature correction factor K ta , and the atmospheric pressure correction factor K pa . The intake air temperature correction factor K ta is calculated from either a K ta1 Table or a K ta2 Table according to the load condition of the engine. Similarly, the first water temperature correction factor K tw is also calculated from either a K tw1 Table or a K tw2 Table corresponding to the load condition of the engine. Referring to Figure 3, the first water temperature correction factor K tw and the second water temperature correction factor K twt are calculated in step S1. More specifically, a line K tw1 and a line K tw2 shown by solid lines at Figure 5 is selected according to the load condition of the engine (a low load or a high load). K tw1 data and K tw2 data is read according to a cooling water temperature T w from the line K tw1 or the line K tw2 wherein this data is set to the first water temperature correction factor K tw . Similarly, K twt data read according to the cooling water temperature T w from the line K twt shown by the dotted line in Figure 5 is set to the second water temperature correction factor K twt . As illustrated in Figure 5, all the lines K tw1 , K tw2 , and K twt are set so that the values at K tw1 , K tw2 , and K twt decrease with an increase in T w . In a preferred embodiment of the present invention, the slope of the line K twt is set to be larger than the slopes of the lines K tw1 and K tw2 . The selection of the line K tw1 or K tw2 according to a load condition may be carried out in accordance with the process illustrated in Figure 6. In this process, at step S21, it is determined whether or not an engine speed N e is greater than a predetermined speed N e1 . If the engine speed N e is greater than the predetermined speed N e1 , the load condition is determined as a high load condition, and the line K tw2 is selected at step S24. Thus, the data read according to the cooling water temperature T w from the line K tw2 is set to be the first water temperature correction factor K tw . On the other hand, if the engine speed N e is less than the predetermined speed N e1 , it is determined at step S22 whether or not a throttle opening  th is greater than a predetermined opening  th1 . If the throttle opening  th is greater than the predetermined opening  th1 , the load condition is determined as a high load condition, and the program proceeds to step S24. If the throttle opening T h is less than the predetermined opening  th1 the load condition is determined as a low load condition, and the line K tw1 is selected at step S23. Thus, the data read according to the cooling water temperature T w from the line K tw1 is set as the first water temperature correction factor K tw . As illustrated in Figure 3, the intake air temperature correction factor K ta is calculated at step S2. More specifically, either a line K ta1 or a line K ta2 , as shown in Figure 7, is selected according to whether the engine is in a low load condition or a high load condition. K ta1 data or K ta2 data is read according to the intake air temperature T a wherein the data is set to the intake air temperature correction factor K ta . The lines K ta1 and K ta2 , as shown in Figure 7, are common when the intake air temperature T a is not higher than about 50°C, and the slope of the line K ta2 is 0 when the intake air temperature T a is greater than about 50°C. Alternatively, the slope of the line Kta2 can be smaller than the slope of the line K ta1 when the intake air temperature T a is greater than about 50°C. The selection of the line K ta1 or the line K ta2 is based upon a load condition of the engine as illustrated in Figure 8. Since the details of this procedure are similar to those described above with respect to Figure 6, the precise description of this procedure shown in Figure 8 will be omitted for the sake of brevity. As illustrated in Figure 3, the atmospheric pressure correction K pa is calculated at step S3. More specifically, the atmospheric pressure correction factor K pa is calculated according to an atmospheric pressure P a from a Table illustrated in Figure 9. At step S4, the first fundamental fuel injection quantity correction factor K total is calculated utilizing the following equation: K total = K tw x K ta x K pa At step S5, the acceleration incremental fuel injection quantity correction factor K acc is calculated utilizing the following equation: K acc = K twt x K ta x K pa At step S6, the second fundamental fuel injection quantity correction factor K ast is calculated. More specifically, the second fundamental fuel injection quantity correction factor K ast is calculated from a Table as illustrated in Figure 10 according to the number of TDC pulses accumulated from the start of the operations of the engine. At step S7, the fundamental fuel injection quantity T im is calculated. More specifically, either the N e - th map shown in Figure 11 or in N e -P b map illustrated in Figure 12 is selected according to the throttle opening  th and the engine speed N e such that the fundamental fuel quantity T im is read from the selected map according to N e and  th or an intake air pressure P b . The selection of the N c - th map or the N e -P b map can be carried out by utilizing a region selecting Table as illustrated in Figure 13. In the N e -P b map as illustrated in Figure 12, the magnitude relation shown along the axis of the intake air pressure P b is adapted such that the intake air pressure P b is represented as an absolute pressure. If the intake air pressure P b is represented as a negative pressure, the magnitude relation of the intake air pressure P b is reversed. At step S8, the fundamental fuel injection quantity T im calculated above is corrected by utilizing the following equation: T im = T im x K ast x K total At step S9, the acceleration incremental fuel injection quantity T acc is set. The acceleration incremental fuel injection quantity T acc is a fixed value, for example. While the process illustrated in Figure 3 is executed upon the interruption of the crank .. pulses as mentioned above, a predetermined number of times of this execution may be set as a single unit. In this single unit, the acceleration incremental fuel injection quantity T acc may be set to a fixed value for a corresponding number of times that a vehicle accelerates. Moreover, this value may be set to 0 for the remaining number of times. Alternatively, the acceleration incremental fuel injection quantity T acc may be set according to the acceleration of the vehicle. At step S10, the acceleration incremental fuel injection quantity T acc is corrected by utilizing the following equation: T acc = T acc x K acc At step S11, the fuel injection quantity T out , is calculated from the following equation: T out = T im + T acc + T v In equation (5), T im and T acc are the values respectfully corrected at steps S8 and S10. The voltage incremental injection quantity T v is obtained from a Table illustrated in Figure 14 according to the battery voltage V b . The voltage incremental injection quantity T v is calculated for a fixed period of time, for example. In Figure 14, the unit of the voltage incremental fuel injection quantity T v represented by the ordinate access is time, which is an excitation time of the injector 29, and the excitation time corresponds to a fuel injection quantity. The fuel injection quantity T out , upon calculation, is inputted into a driving circuit for the injector 29. The excitation time (or excitation duty ratio) of the injector 29 is controlled according to the fuel injection quantity T out . The intake air temperature T a , the engine speed N e , the throttle opening  th , the cooling water temperature T w , the atmospheric pressure P a , and the intake air pressure P b are detected or computed by known methods by an interruption process. Figure 15 is a block diagram of a preferred embodiment of the present invention, and Figure 16 is a block diagram illustrating the details of the load determining circuit 9 shown in Figure 15. In Figure 15, an engine speed sensor 2 functions as the crank pulser 2a and also functions to determine an engine speed N e by using output pulses from the crank pulser 2a. Further, a TDC pulser 6 functions to output TDC pulses by utilizing output pulses from the crank pulser 2a in the cam pulser 54. As illustrated in Figure 15, the load determining circuit 9 detects a low condition of the engine by using an engine speed N e and a throttle opening  th . More specifically, as illustrated in Figure 16, a comparator 30 compares N e with a predetermined speed N e1 stored in an N e1 memory 31. If N e is greater than N e1 , the compartor determines that the engine is in a high load condition. Then, K ta2 Table 12 and K tw2 Table 14 are selected through an OR gate 34. Furthermore, the comparator 32 compares  th with a predetermined opening  th1 stored in a  th1 memory 33. If  th is greater than  th1 , the compartor 32 determines that the engine is in a high load condition. Then, K ta2 Table 12 and K tw2 Table 14 are selected through the OR gate 34. If both the compartors 30 and 32 determine that the engine is not in a high load condition, K ta1 Table 11 and K tw1 Table 13 are selected through an AND gate 35. K ta1 or K ta2 correspond to an intake air temperature T a read from the K ta1 Table 11 or the K ta2 Table 12 selected above. This data is inset to K ta . Furthermore, K tw1 or K tw2 corresponds to a cooling water temperature T w read from the K tw1 Table 13 or the K tw2 Table 14 selected above and is set to K tw . Furthermore, K twt corresponding to T w is read from a K twt Table 16, and K pa corresponding to an atmospheric pressure P a is read from a K pa Table 17. K total setting circuit computes the first fundamental fuel injection quantity correction factor K total by multiplying K tw , K ta , and K pa . Furthermore, K acc setting circuit 18 computes the acceleration incremental fuel injection quantity correction factor K acc by multiplying K twt , K ta , and K pa . The selecting circuit 10 selects either the N e - th map 23 or N e -P b map 24 according to the relationship shown in Figure 13 by utilizing the engine speed N e and a throttle opening  th . If the N e - th map 23 is selected, the fundamental fuel injection quantity T im corresponding to N e and  th is read from the N e - th map 23. If the N e -P b map 24 is selected, the fundamental fuel injection quantity T im corresponding to N e and an intake air pressure P b is read from the N e -P b map 24. The TDC pulses outputted from the TDC pulser 26 are inputted into a counter 21 such that the total number of TDC pulses is counted by the counter 21. The counted number of TDC pulses is inputted into K ast Table 22, in the second fundamental fuel injection quantity correction factor K ast corresponding to the counted number is read from the K ast Table 22. A T im correcting circuit 25 corrects T im by multiplying the fundamental fuel injection quantity T im by the correction factors K total or K ast read from either map 23 or map 24. A T acc correcting circuit 20 corrects an acceleration incremental fuel injection quantity T acc read from the T acc memory 19 by multiplying the acceleration incremental fuel injection quantity T acc by the acceleration incremental fuel injection quantity correction factor K acc . A voltage incremental fuel injection quantity T v corresponding to a battery voltage V b is read from a T v Table 26. A T out setting circuit 27 sets the fuel injection quantity T out by adding the corrected fundamental fuel injection quantity T im , the corrected acceleration incremental fuel injection quantity T acc , and the voltage incremental fuel injection quantity T v . The fuel injection quantity T out , thus computed, is inputted into an injector driving circuit 28. Figure 1 is a block diagram of the present invention as simplified from Figure 15. In Figure 1, the same reference numerals as shown in Figure 15 designate the same or corresponding powers. As previously mentioned with reference to Figure 15, the intake air temperature correction factor K ta is set according to an intake air temperature T a . The intake air temperature correction factor K ta is different for a low load condition and high load condition for the engine. More specifically, when the engine is in a low load condition, low load intake air temperature correction factor setting circuit 11a is selected while when the engine is in a high load condition, high load intake air temperature correction factor setting circuit 12A is selected. The setting circuits 11A or 12A set K ta1 or K ta2 according to an intake air temperature T a and outputs K ta1 or K ta2 as the intake air temperature correction factor K ta to a fuel injection quantity computing circuit 100. The fuel injection quantity computing circuit 100 computes a fuel injection quantity to be inputted into the injector driving circuit 28 by a suitable method while utilizing the intake air temperature correction factor K ta . A fundamental fuel injection quantity correction factor setting circuit 15A and an acceleration incremental fuel injection quantity correction factor setting circuit 15A and an acceleration incremental fuel injection quantity correction factors setting circuit 18A set a fundamental fuel injection quantity correction factor and an acceleration incremental fuel injection quantity correction factor, respectfully, by using the intake air temperature correction factor K ta . Furthermore, a fundamental fuel injection quantity setting circuit 23A sets a fundamental fuel injection quantity T im by utilizing an engine speed N e , intake air pressure P b , and throttle opening  th . An acceleration incremental fuel injection quantity setting circuit 19A sets an acceleration incremental fuel injection quantity T acc . The fundamental fuel injection quantity correcting circuit 25A and the acceleration incremental fuel injection quantity correcting circuit 20A correct the fundamental fuel injection quantity T im and the acceleration incremental fuel injection quantity T acc , respectfully, by utilizing the fundamental fuel injection quantity correction factor and the acceleration incremental fuel injection quantity correction factor, respectfully, set by the setting circuits 15A and 18A. The fuel injection quantity setting circuit 27A determines a fuel injection quantity T out by utilizing the corrected T im and the corrected T acc . The load condition determining process for the selection of the Table shown in Figure 8 can be carried out by the method as illustrated in Figure 17. When a clutch for the vehicle is in an off condition or the transmission in the vehicle is in the neutral condition (i.e., a no load switch is on), it is determined that the engine is in a low load condition. On the other hand, when the clutch and the transmission are in the engaged condition, it is determined that the engine is in a high load condition. The no load switch mentioned above can be realized by the utilization of a microcomputer in the ECU 60. This load condition determining method may also be applied to the selection of the Table shown in Figure 6. Figure 18 is a block diagram as simplified from Figure 15. In Figure 18, the same reference numerals as those shown in Figure 15 designate the same or corresponding parts. A first water temperature correction factor setting circuit 13A sets a first water temperature correction factor K tw according to a cooling water temperature T w and outputs the first water temperature correction factor K tw to a fuel injection quantity computing circuit 100. Similarly, a second water temperature correction factor setting circuit 16A sets a second water temperature correction factor K twt according to the cooling water temperature T w and outputs the second water temperature correction factor K twt to the fuel injection quantity computing circuit 100. More specifically, the first water temperature correction factor setting circuit 13A sets the first temperature correction factor K tw corresponding to T w by utilizing either K tw1 Table 13 or the K tw2 Table 14 or by utilizing an average between the K tw1 Table 13 and the K tw2 Table 14. The selection of the K tw1 Table 13 and the K tw2 Table 14 is carried out according to a load condition of the engine. The first water temperature correction factor K tw is set by using the selected Table. However, K tw may not be set according to a load condition of the engine. Furthermore, the second water temperature correction factor setting circuit 16A sets the second water temperature correction factor K twt corresponding to T w by utilizing the K tw Table 16. The fuel injection quantity computing circuit 100 computes a fundamental fuel injection quantity T im as a fuel injection quantity during the normal running condition of the engine. The fuel injection quantity computing circuit 100 also computes an acceleration incremental fuel injection quantity T acc as an increment of a fuel injection quantity during acceleration of the engine. The calculation of these quantities are in accordance with the first water temperature correction factor K tw and the second water temperature correction factor K twt . Based upon these calculations, the fuel injection quantity computing circuit 100 computes the proper fuel injection quantity to be inputted into the injector driving circuit 28. More specifically, a fundamental fuel injection quantity correction factor setting circuit 15A sets a fundamental fuel injection quantity correction factor by utilizing the first water temperature correction factor K tw , and an acceleration incremental injection quantity correction factor setting circuit 18A sets an acceleration incremental injection quantity by using the second water temperature correction factor K twt . Furthermore, a fundamental fuel injection quantity setting means 23A sets a fundamental fuel injection quantity T im by utilizing the engine speed N e , intake air pressure P b , and throttle opening  th . An acceleration incremental fuel injection quantity setting circuit 19A sets an acceleration incremental fuel injection quantity T acc . The fundamental fuel injection quantity correcting circuit 25A and the acceleration incremental fuel injection quantity correcting circuit 20A correct the fundamental fuel injection quantity T im and the acceleration incremental fuel injection quantity T acc , respectfully, by utilizing the fundamental fuel injection quantity correction factor and the acceleration incremental fuel injection quantity correction factor, respectfully, set by the setting circuits 15A and 18A. The fuel injection quantity setting circuit 27A determines a fuel injection quantity T out by utilizing the corrected T im and the corrected T acc . The load condition determining process for the selection of the Tables shown in Figure 8 can be carried out as shown in Figure 17. When a clutch for a vehicle is in a off condition or a transmission of the vehicle is in a neutral condition (i.e., a no load switch is on), it is determined that the engine is in a low load condition. When the clutch or the transmission are in an engaged condition, it is determined that the engine is in a high load condition. The no load switch mentioned above can be realized by the microcomputer in the ECU 60. While the present invention is applicable to a motorcycle in the above preferred embodiments, it is to be understood that the present invention is not limited to the preferred embodiments but may be applicable to a fuel injection control device for any internal combustion engine such as an automobile or the like. According to the present invention, when a detected intake air temperature is high for a high load condition of the engine, an intake air temperature correction factor is established such that the intake air temperature is less influential upon the determination of the fuel injection quantity. Thus, even when the detected intake air temperature is higher than an actual intake air temperature, an intake air temperature correction factor similar to a correction factor for the actual intake air temperature can be set such that the measured intake air temperature is less influential. Accordingly, when an engine is experiencing a high load condition, the fuel injection quantity demanded by the engine can be obtained.

Claims: A fuel injection control device of an internal combustion engine, comprising: means for setting a fundamental fuel injection quantity (T im ), means for setting an intake air temperature correction factor (K ta1 , K ta2 ), said intake air temperature correction factor (K ta1 , K ta2 ) decreasing as the intake air temperature increases, means for correcting said fundamental fuel injection quantity (T im ) according to said intake air temperature correction factor (K ta1 , K ta2 ), means for determining a load condition of said internal combustion engine, characterized in that, in case the intake air temperature exceeds a first predetermined temperature value, a rate of decrease of said intake air temperature correction factor (K ta1 , K ta2 ) is set to a first predetermined value in case said means for determining a load condition of said internal combustion engine determines a high load condition of said internal combustion engine, and is set to a second predetermined value in case said means for determining a load condition of said Internal combustion engine determines a low load condition of said internal combustion engine, said first predetermined value being zero or being lower than said second predetermined value. The device as claimed in claim 1, characterized in that said first predetermined value of said rate of decrease of said intake air temperature correction factor (K ta2 ) is set to 0. The device as claimed in claim 1 or 2, characterized in that in case the intake air temperature exceeds a second predetermined temperature value higher than said first predetermined temperature value, the second predetermined value of said rate of decrease of said intake air temperature correction factor (K ta1 ) is set to 0. The device as claimed in any one of the preceding claims, characterized in that said load determining means comprises: engine speed detecting means for detecting a speed of said engine, said load determining means determining the load condition based on a detected engine speed. The device as claimed in any one of the preceding claims, characterized in that said load determining means comprises throttle angle detecting means for detecting an angle of a throttle of said engine, said load determining means determining the load condition based on the detected throttle angle. Method for controlling fuel injection of an internal combustion engine comprising the steps: a) setting a fundamental fuel injection quantity (T im ), b) determining an intake air temperature, c) setting an intake air temperature correction factor (K ta1 , K ta2 ), said intake air temperature correction factor (K ta1 , K ta2 ) decreasing as the intake air temperature increases, d) correcting said fundamental fuel injection quantity (T im ) according to said intake air temperature correction factor (K ta1 , K ta2 ), e) determining a load condition of said internal combustion engine, characterized by the further step of f) in case the intake air temperature exceeds a first predetermined temperature value, setting a rate of decrease of said intake air temperature correction factor (K ta2 ) to a first predetermined value in case the determined load condition is a high load condition, and setting said predetermined rate of decrease of said intake air temperature correction factor (K ta1 ) to a second predetermined value in case the determined load condition is a low load condition, said first predetermined value being zero or being lower than said second predetermined value. The method according to claim 6, characterized in that said first predetermined value of said rate of decrease of said intake air temperature correction factor (K ta2 ) is set to 0. The method according to claims 6 or 7, characterized in that in case the intake air temperature exceeds a second predetermined temperature value higher than the first predetermined temperature value, said second predetermined value of said rate of decrease of said intake air temperature correction factor (K ta1 ) is set to 0. The method according to any one of claims 6 to 8, further comprising the steps of detecting a speed of the engine, said load condition being determined in dependence on said detected speed of said engine. The method according to any one of claims 6 to 9, further comprising the step of detecting an angle of a throttle of said engine, said load condition being determined in dependence on said detected throttle angle.

Inventors: ABE MASAHIKO, IWATA YASUO, MASUDA SHOJI, ABE, MASAHIKO, IWATA, YASUO, MASUDA, SHOJI, Abe, Masahiko, c/o Kabushiki Kaisha Honda, Iwata, Yasuo, c/o Kabushiki Kaisha Honda, Masuda, Shoji, c/o Kabushiki Kaisha Honda
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1992
Main classification: F02D41
IPC codes: F02D41