Electronic fuel injection control system and control method

Abstract: It is an object of this invention to provide a system and a method of electronically controlling fuel injection, which prevents discharge of smoke even when a vehicle having a turbo-chargered diesel engine with a system of electronically controlled fuel injection is driven along highland road. A basic fuel injection quantity control map for determining basic fuel injection quantity based on the engine revolution and the accelerator pedal depression, a boost pressure control map for determining first maximum fuel injection quantity based on the engine revolutionand boost pressure, an atmospheric pressure control map for determining second maximum fuel injection quantity based on the engine rotational number and the atmospheric pressure are provided within a controller (7). The smallest quantity out of the three quantities is determined as a final fuel injection quantity. In this invention, a plurality of boost pressure control maps are prepared for different atmospheric pressure levels and, upon determination of the first maximum fuel injection quantity, a proper one corresponding to the detected atmosphere is employed. Thus, injection quantity never becomes excess even when driving along a highland road where the atmospheric pressure is lower than in a low- and flat-land road and therefore the boost pressure increases in a manner different from that in the latter, thus smoke discharge being effectively prevented.

Description: This invention relates to an electronic fuel injection control system for minimizing decrease of power of a turbo-chargered diesel engine electronically controlled as to fuel injection and for avoiding discharge of smoke when vehicles having such engine are driven along a highland road. In addition, this invention also relates to a method for electronically control such system. EP-A-0 059 586 discloses an engine control system which comprises a microprocessor for controlling the fuel delivery rate supplied to the engine. The control system includes several control maps for controlling injection timing and fuel delivery rate. The fuel delivery rate control maps consist of a torque rise limit map, a rack limit position map, a fuel/air limit map, and a single altitude derating map. The torque rise limit map, rack limit position map, and fuel/air limit map receive the actual engine speed as input whereas the altitude derating map is responsive to atmospheric pressure. The outputs of the torque rise limit map and the altitude derating map are applied to an adder. The output of the adder and the output of the rack limit position map are applied to a least-win logic selector which selects the lower of these two outputs for defining the actual fuel amount. JP-A-59-153 931 discloses a fuel injection quantity controller for diesel engine. The controller calculates a basic injection quantity corresponding to engine speed and accelerator opening. The actual fuel injection quantity is obtained by comparing the basic injection quantity and an upper limit therefor obtained in accordance with suction pressure and its variation. Generally, in a vehicle having a turbo-charge diesel engine in which fuel injection is electronically controlled, fuel injection quantity and fuel injection timing are controlled by a controller mainly comprising a computer. The fuel injection quantity is controlled according to various control maps previously installed in the computer. The control maps are roughly grouped into two types: one to be applied upon start of engine; and the other to be applied during driving. Contents of the maps are properly decided depending upon starting characteristics or driving characteristics required. As control maps to be applied during driving, there are prepared, for example, a basic injection quantity control map, a boost pressure control map, an atmospheric pressure control map, etc. An actual injection quantity satisfies the requirements determined by these control maps. Each of these control maps are described in detail by reference to Figs. 3 to 5. Fig. 3 is a graph showing one example of a basic injection quantity control map, with engine revolution (N) as abscissa and basic fuel injection quantity (Q BASE ) as ordinate. Curves of the map are drawn with accelerator pedal depression (c) as a parameter. This map is designed for determining the basic injection quantity based on engine revolution and accelerator pedal depression. For example, when engine revolution is N 1 and accelerator pedal depression is 100 %, the basic injection quantity is determined to be Q 100 . Similarly, when engine revolution is N 1 and accelerator pedal depression is 70 % or 40 %, the basic injection quantity is determined to be Q 70 or Q 40 . Additionally, curve d corresponding to accelerator pedal depress ion of 0 % is a curve when the accelerator pedal is not depressed at all. An actual injection quantity is determined by correcting the thus-determined basic injection quantity using the other control maps shown in Figs. 4 and 5. Fig. 4 is a graph showing one example of the atmospheric pressure control map, with engine revolution as abscissa and maximum injection quantity, Q AFULL (A: Atmosphere), as ordinate. This map is designed for determining maximum injection quantity corresponding to a particular atmospheric pressure at driving spot. In the graph, parameter of the control curve is atmospheric pressure. Curve a is a curve under the atmospheric pressure of P SEA (atmospheric pressure at sea level, i. e., 760mmHg), and curves b, c and d are curves under the atmospheric pressures of P 1 , P 2 and P 3 (provided that P SEA > P 1 > P 2 > P 3 ). The maximum fuel injection quantity Q AFULL is determined on the basis of atmospheric pressure and engine revolution. Additionally, the basic fuel injection quantity map shown in Fig. 3 is usually prepared so that the quantity becomes optimal when the atmospheric pressure is P SEA . Hence, curve a in Fig. 3 of 100 % in accelerator pedal depression (maximum injection quantity) corresponds to curve a in Fig. 4 under the atmospheric pressure of P SEA . The atmospheric pressure control map is prepared in view of the fact that a proper fuel injection quantity varies depending upon atmospheric pressure at a driving spot. For example, during driving along the beach, the basic fuel injection quantity map gives a proper fuel injection quantity but, when driving along a highland road (e.g., roads in Hakone or Mt. Fuji; typical mountaineous roads in Japan) under control of the map, the map fails to give a proper fuel injection quantity since the quantity of intake air introduced into cylnders, or the quantity of oxygen, is decreased. When the atmospheric pressure decreases, the proper injection quantity decreases. Therefore, when driving along highland roads with directly employing the basic fuel injection quantity control map, the fuel injection quantity becomes excess, thus resulting in discharge of smoke. This atmospheric pressure control map is intended to decrease the maximum fuel injection quantity (i.e., injection quantity limit) as the atmospheric pressure decreases. Fig. 5 is a graph showing an example of the boost pressure control map. This graph is designed to determine maximum fuel injection quantity depending upon the super-charged degree of the pressure inside intake air pipes in comparison with ambient atmospheric pressure. The curves are drawn with engine revolution as abscissa and maximum fuel injection quantity, Q BFULL ( B: Boost), as ordinate. Boost pressure is used as a parameter of the control curves. Curve a is a curve when the boost pressure is Pb 1 (e.g., 300 mmHg), and curve b is a curve when the boost pressure is Pb 2 (e.g., 100 mmHg). The maximum fuel injection quantity Q BFULL is determined on the basis of boost pressure and engine revolution. As intake air is super-charged in turbo-chargered diesel engines, pressure inside the air intake pipes is higher than that of ordinary engines (natural-aspirated (NA) engines). Additionally, boost pressure P b is determined by the formula of P B - P A wherein P B represents an inside pressure of air intake pipes detected by a sensor for the inside pressure of air intake pipes, and P A represents an atmospheric pressure detected by an atmospheric pressure sensor. (P B Pressure detected by the sensor for inside pressure of air intake pipes = P A atmospheric pressure + P b boost pressure ). In controlling the fuel injection quantity using the control maps in the above-described manner, the basic fuel injection quantity determined by Fig. 3 is designed not to exceed the maximum injection quantities determined by Figs. 4 and 5. That is, the smallest out of the following three quantities is decided as an actual fuel injection quantity: (1) Basic fuel injection quantity Q BASE determined by the control map in Fig. 3; (2) Maximum fuel injection quantity Q AFULL determined by the control map in Fig. 4; and (3) Maximum fuel injection quantity Q BFULL determined by the control map in Fig. 5. Additionally, as literature on the prior art of electronic fuel injection control system for diesel engines, there is illustrated, for example, Japanese Patent Application Laid-open JP-A- S59-96442. This literature discloses to use absolute pressure within the air intake pipe for determining fuel injection quantity on the basis of control map. However no countermeasures have so far been taken against change of the boost pressure due to change of the ambient atmospheric pressure. Therefore, there has been a problem that, in driving a vehicle having a turbo-chargered diesel engine along a highland road (e.g., 2,000 m above sea level), fuel injection quantity becomes excess, thus smoke being liable to be produced. In the prior art, as the boost pressure control map (Fig. 5), only one map has been prepared that can be most optimally adapted when the atmospheric pressure is the atmospheric pressure of a low- and flat-land of P SEA ( = 760 mmHg). In highlands where the atmospheric pressure is lower, the boost pressure increases in accordance with engine revolution in a different manner from that in a low- and flat-land. Hence, in driving along a highlandroad, the fuel injection quantity becomes excess and severe smoke is liable to be discharged if the injection quantity is controlled according to the boost pressure control map for driving along a low- and flat-land road. Additionally, in the aforesaid Japanese Patent Application Laid-open JP-A- S59-96442, the pressure inside air intake pipe is detected in an absolute pressure, and hence contribution of the atmospheric pressure and the boost pressure to the absolute pressure is unknown. Therefore, when the detected absolute pressure is, for example, 760 mmHg, the same quantity of fuel is to be injected in the following two cases: (1) atmospheric pressure = 560 mmHg and boost pressure = 200 mmHg; and (2) atmospheric pressure = 760 mmHg and boost pressure = 0 mmHg. In the above prior art electronic fuel injection controlling system for a diesel engine, a basic fuel injection quantity control map for determining basic injection quantity on the basis of engine revolution and accelerator pedal depression, a boost pressure control map for determining a first maximum fuel injection quantity on the basis of engine revolution and boost pressure, and an atmospheric pressure control map for determining a second maximum fuel injection quantity on the basis of engine revolution and atmospheric pressure are provided within the controller, the smallest quantity being selected from the three quantities determined by these maps, and fuel injection is effected in the thus determined quantity. Thus, this prior art also fails to meet the fact that boost pressure in highlands increases differently from that in flat-and low-lands. In order to solve the above-described problem, the present invention employs an electronic fuel injection control system as defined in claim 1. In addition, this invention employs a method for electronically controlled fuel injection as defined in claim 2. In the present invention, a plurality of boost pressure control maps are prepared corresponding to different atmospheric pressure levels. In determining the first maximum injection quantity, one of the boost pressure control maps corresponding to a detected atmospheric pressure is employed. Thus, smoke is not discharged even when driving along a highland road where super-charging pressure increases in a different manner from that in driving along a low- and flat-land road, since a fuel is not injected in an excess amount. Brief Description of the Drawings Fig. 1 is a flow chart for illustrating the method of the present invention for electronically controlled fuel injection. Fig. 2 is a block diagram showing the electronic fuel injection control system to which the method of this invention is applied. Fig. 3 is a drawing showing one example of basic fuel injection quantity control map upon driving. Fig. 4 is a drawing showing one example of atmospheric pressure control map. Fig. 5 is a drawing showing one example of boost pressure control map. Fig. 6 is a drawing showing one example of a plurality of boost pressure control maps prepared for different atmospheric pressure levels. Best Mode of Carrying Out of the Invention The present invention is now described in more detail by reference to drawings. Fig. 2 is a block diagram showing the electronic fuel injection controlling system of the present invention. Numeral 1 designates an injection pump, 2 an engine revolution sensor, 3 a fuel pipe, 4 an electric governer, 5 a timing control valve, 6 a fuel pipe, 7 a controller, 8 an accelerator pedal depression sensor, 9 an atmospheric pressure sensor, 10 an alarm lamp, 11 a sensor for pressure inside an air intake pipe, 12 an air intake pipe, 13 an injection nozzle, 14 a diesel engine, 15 an exhaust gas returning pipe, 16 an exhaust pipe, and 17 a turbo-charger. The atmospheric pressure sensor 9 may be provided outside or inside the controller 7. The engine is a turbo-chargered diesel engine. An air intake into the engine 14 is super-charged by the turbo-charger 17. The fuel is fed into the injection pump 1 through the fuel pipe 3, fed into the injection nozzle 13 through the fuel pipe 6, and injected into inside of the diesel engine 14. The injection quantity is controlled by the electric governer 4, and the injection timing is controlled by timing control valve 5. Control signals to the electric governer 4 and the timing control valve 5 are generated in the controller 7 based on signals from various sensors and control maps previously installed in the controller 7. A signal for controlling injection quantity during driving is generated by applying, to various control maps as shown in Figs. 3 to 5, the engine revolution detected by the engine revolution sensor 2, the accelerator pedal depression detected by the accelerator pedal depression amount sensor 8, the atmospheric pressure detected by the atmospheric pressure sensor9, the pressure within the air intake pipe detected by the sensor 11 for pressure within the air intake pipe, etc. In the present invention, however, not only a boost pressure control map shown in Fig. 5 corresponding to the atmospheric pressure of P SEA (760 mmHg) but several additional maps for other different atmospheric pressure levels are provided in the controller 7 for the purpose of meeting the phenomenon that boost pressure corresponding to engine revolution increases in a different manner under different atmospheric pressure. Of the different naps, a proper one is selected to use that corresponds to the actual atmospheric pressure. Thus, even when driving along a highland road, a boost pressure control map corresponding to the driving spot is employed, thereby production of smoke, etc. being prevented. Fig. 6 shows an example of a plurality of boost pressure control maps corresponding to different atmospheric pressure levels. Additionally, for the purpose of saving page space, drawings are reduced in the horizontal axis direction in comparison with Fig. 5. Fig. 6 (A) to (E) respectively represent the following: Fig. 6 (A)···boost pressure control map when P A = P SEA (same as Fig. 5); Fig. 6 (B)···boost pressure control map when P SEA > P A ≧ P 1 ; Fig. 6 (C)···boost pressure control map when P 1 > P A ≧ P 2 ; Fig. 6 (D)···boost pressure control map when P 2 > P A ≧ P 3 ; Fig. 6 (E)···boost pressure control map when P 3 > P A . In this example, 5 boost pressure control maps are prepared. However, more maps may be prepared by dividing the atmospheric pressure into smaller zones. Actual values of P 1 , P 2 , etc. may properly be selected. Fig. 1 is a flow chart for illustrating the method of the present invention for electronically controlled fuel injection quantity. Step 1···Read the following detected signals into controller 7: engine revolution N detected by the engine revolution sensor 2; accelerator pedal depression A C detected by the accelerator pedal depression sensor 8; atmospheric pressure P A detected by the atmospheric pressure sensor 9; and air intake pipe inside pressure P B detected by the sensor 11 for air intake pipe inside pressure. Step 2···Determine basic fuel injection quantity Q BASE by applying the engine revolution N and accelerator pedal depression A c to the basic fuel injection control map shown in Fig. 3. Step 3···Select a proper boost pressure control map among the boost pressure control maps shown in Fig. 6, which corresponds to the detected atmospheric pressure P A . For example, when value of the detected atmospheric pressure is P 2 , select the map of Fig. 6 (C). Step 4···Determine maximum fuel injection quantity Q BFULL by applying the boost pressure ( P b = P B - P A ) and the engine revolution N to the thus selcted boost pressure control map. Step 5···Select a proper atmospheric pressure control curve out of the curves shown in Fig. 4. For example, when value of the detected atmospheric pressure P A is P 2 , select curve (c). Step 6···Determine maximum fuel injection quantity Q AFULL by applying the detected engine revolutionN to the thus selected curve (c) in Fig. 4. Step 7···Compare the thus determined basic fuel injection quantity Q BASE , maximum fuel injection quantity Q AFULL and maximum fuel injection quantity Q BFULL with each other to determine the smallest quantity, and control injection based on the smallest quantity. Additionally, though the basic fuel injection quantity Q BASE , the maximum fuel injection quantity Q BFULL , and the maximum fuel injection quantity Q AFULL are determined in this order in the above description, any of them may be determined first, and the order is not limitative at all. As has been described hereinbefore, in the present invention, a plurality of boost pressure control maps are prepared corresponding to different atmospheric pressure levels and in determining the first maximum injection quantity, one of the boost pressure control maps corresponding to a detected atmospheric pressure is employed. Therefore the system and the method of this invention for electronically controlled fuel injection enable not to feed fuel in excess amount even when driving along a highland road where atmospheric pressure is lower than in a low- and flat-land road and therefore super-charging pressure increases differently from the latter, thus smoke discharge being effectively prevented.

Claims: An electronic fuel injection control system having an engine revolution sensor, an accelerator pedal depression sensor, an atmospheric pressure sensor, an air intake pipe inside pressure sensor, a basic fuel injection quantity control map for determining basic fuel injection quantity based on the engine rotational number and the accelerator pedal depression, boost pressure control map for determining first maximum fuel injection quantity based on the engine revolution and boost pressure, an atmospheric pressure control map for determining second maximum fuel injection quantity based on the engine revolution and the atmospheric pressure, and an injection quantity-controlling means for injecting fuel in the smallest quantity of the three quantities respectively determined by said three maps, wherein a plurality of boost pressure control maps are provided as said boost pressure control map corresponding to different atmospheric pressure levels. A method for electronically controlled fuel injection by selecting the smallest quantity out of three injection quantities of a basic fuel injection quantity, a first maximum fuel injection quantity, and a second maximum fuel injection quantity respectively determined from a basic fuel injection quantity control map for determining the basic fuel injection quantity based on engine revolution and accelerator pedal depression, a boost pressure control map for determining the first maximum fuel injection quantity based on engine rotational number and boost pressure, and an atmospheric pressure control map for determining the second maximum fuel injection quantity based on engine revolution and atmospheric pressure, wherein a proper boost pressure control map is selected in accordance with a detected atmospheric pressure as said boost pressure control map from a plurality of boost pressure control maps for different atmospheric pressure levels.

Inventors: IMAI JUNICHI, INOUE SHINICHI, KURODA KOUICHI, MAKIMOTO TAKASHI, SANADA MASANORI, TAKEUCHI MAKOTO, UCHIYAMA TADASHI, IMAI, JUNICHI, INOUE, SHINICHI, KURODA, KOUICHI, MAKIMOTO, TAKASHI, SANADA, MASANORI, TAKEUCHI, MAKOTO, UCHIYAMA, TADASHI
Applicants: ISUZU MOTORS LTD, ISUZU MOTORS LIMITED
Application year: 1996
Main classification: F02D41
IPC codes: F02D41, A43B7, A43D21, F02D31, A43B5, F02B3