Engine control unit

Abstract

To provide an engine control device capable of making an ignition timing suitable even if the number of injection stages is increased according to an engine state.SOLUTION: A control system of an engine control device, as an ignition timing map in which an ignition timing is set for each engine operation point, stores a first ignition timing map corresponding to the number of first injection stages of an injector, and a second ignition timing map corresponding to the number of second injection stages more than the number of first injection stages. The control system determines the number of injection stages of the injector (S15 and S16), if the number of injection stages is the number of first injection stages, controls the ignition timing of an ignition plug on the basis of the first ignition timing map (S17, S20, and S21), and if the number of injection stages is the number of second injection stages, controls the ignition timing of the injection plug on the basis of the second ignition timing map (S18 or S19, S20, and S21).SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to an engine control device for controlling an engine.

Background Art

[0002] Conventionally, a gasoline direct injection engine is known in which fuel is multi-stage injected into a combustion chamber, and the compression ratio is increased by lowering the temperature in the combustion chamber with the latent heat of vaporization of the fuel. In this engine, the number of fuel injection stages is set according to the engine operating point determined by the engine speed and the engine load, and the ignition timing for the fuel is also set according to the engine operating point, so that it is controlled to have an ignition timing suitable for the number of injection stages. Patent Documents 1 to 4 describe an engine control device that shifts the ignition timing to the advance side or the retard side when switching the number of injection stages.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it was found that increasing the number of injection stages according to the engine condition (e.g., coolant temperature) shifts the MBT (Minimum advance for the Best Torque). Figure 10 is a graph with torque on the vertical axis and crank angle on the horizontal axis, showing the relationship between ignition timing and torque when a stoichiometric air-fuel mixture is supplied under constant throttle opening and constant engine speed. In Figure 10, the MBT for single-stage injection (L1) is MBT1, which is advanced from the piston's top dead center (TDC). When this becomes multi-stage injection (L2), the MBT becomes MBT2, which is shifted further forward than MBT1. In this multi-stage injection case, if ignition is performed at the same timing as in single-stage injection, it will be retarded from the ignition timing that results in MBT2, and therefore will not be a suitable ignition timing. The objective of the present invention is to provide an engine control device that can optimize ignition timing even when the number of injection stages is increased according to the engine state. [Means for solving the problem]

[0005] One embodiment of the engine control device is an engine control device that controls an engine comprising an injector for injecting fuel into the combustion chamber and a spark plug for igniting the fuel-air mixture in the combustion chamber. The engine control device is It has a memory and processor that are connected to each other in a manner that allows them to communicate with each other, and a control system that controls the ignition timing of the spark plug. do. The control system stores an ignition timing map in which the ignition timing is set for each engine operating point, which includes a first ignition timing map corresponding to the first injection stage of the injector, and a second ignition timing map corresponding to a second injection stage that is greater than the first injection stage. The ignition timing of the second ignition timing map is set to be more advanced than the ignition timing of the first ignition timing map. The control system is When the coolant temperature of the engine exceeds a threshold, Number of injection stages of the injector If the number of injection stages is the first injection stage Determine, When the coolant temperature of the engine falls below the threshold, the system determines that the injection stage of the injector is the second injection stage.When the number of injection stages of the injector is the first injection stage, the ignition timing of the spark plug is controlled based on the first ignition timing map, and when the number of injection stages of the injector is the second injection stage, the ignition timing of the spark plug is controlled based on the second ignition timing map. [Effects of the Invention]

[0006] According to one embodiment of the engine control device, the ignition timing is controlled based on an ignition timing map corresponding to the number of injection stages, so the ignition timing can be optimized even when the number of injection stages is increased according to the engine state. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows an example of a vehicle equipped with an engine. [Figure 2] This is a diagram showing an example of an engine. [Figure 3] This figure shows an example of a control system. [Figure 4] This diagram shows an example of the basic structure of an engine control unit. [Figure 5A] This figure shows an example of an injection stage map during normal operation. [Figure 5B] This figure shows an example of an injection stage map at low water temperatures. [Figure 6A] This figure shows an example of an ignition timing map for single-stage injection. [Figure 6B] This figure shows an example of an ignition timing map for two-stage injection. [Figure 6C] This figure shows an example of an ignition timing map for a three-stage injection system. [Figure 7] This is a flowchart showing an example of ignition control. [Figure 8] This figure shows the relationship between the crank angle in each cylinder and the precise timing of injection and ignition. [Figure 9A] This figure shows a modified version of the injection stage map at low water temperatures. [Figure 9B]It is a figure showing a modified example of an ignition timing map for three-stage injection. [Figure 10] It is a figure showing the relationship between ignition timing and torque.

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described in detail based on the drawings. In the following description, the same or substantially the same configurations and elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0009] [Vehicle] FIG. 1 is a diagram showing an example of a vehicle 11 on which an engine 10 is mounted. As shown in FIG. 1, the vehicle 11 is equipped with a power train 12 having an engine 10. The engine 10 is provided with a fuel injection device 13. The vehicle 11 is provided with a fuel tank 14 for storing fuel such as gasoline. The fuel tank 14 and the engine 10 are connected to each other via a fuel supply path 15. The illustrated engine 10 is a horizontally opposed engine, but it is not limited thereto, and it may be an in-line engine or a V-type engine. Further, the engine 10 is a four-cylinder engine, but it is not limited thereto, and it may be an engine with five or more cylinders or an engine with three or fewer cylinders (including a single-cylinder engine).

[0010] [Engine] FIG. 2 is a diagram showing an example of the engine 10. As shown in FIG. 2, the engine 10 has a cylinder block 20 constituting one cylinder bank, a cylinder block 21 constituting the other cylinder bank, and a crankshaft 22 supported by the pair of cylinder blocks 20 and 21. Cylinders (cylinders) 23 are formed in each of the cylinder blocks 20 and 21, and pistons 24 are accommodated in each of the cylinders 23. The crankshaft 22 and the piston 24 are connected to each other via a connecting rod 25.

[0011] Each cylinder block 20, 21 is fitted with a cylinder head 31 equipped with a valve train mechanism 30, etc. The cylinder head 31 has a combustion chamber 32 for each cylinder 23. The cylinder head 31 also has an intake port 33 that communicates with the combustion chamber 32, and an intake valve 34 that opens and closes the intake port 33 is assembled thereto. The cylinder head 31 also has an exhaust port 35 that communicates with the combustion chamber 32, and an exhaust valve 36 that opens and closes the exhaust port 35 is assembled thereto. Furthermore, the cylinder head 31 is provided with an injector 37 that injects fuel into the combustion chamber 32, and an ignition plug 38 that ignites the fuel mixture in the combustion chamber 32. The fuel tank 14 and the injector 37 are connected to each other via the fuel supply path 15.

[0012] [Control System] Figure 3 shows an example of the control system 80. As shown in Figure 3, the fuel injection unit 13 is equipped with a control system 80 consisting of an engine control unit 83. Sensors connected to the engine control unit 83 include a vehicle speed sensor 84 for detecting vehicle speed, an accelerator sensor 85 for detecting the amount of accelerator pedal operation, and a brake sensor 86 for detecting the amount of brake pedal operation. Sensors connected to the engine control unit 83 also include a crank rotation sensor 87 for detecting the rotation angle of the crankshaft, a water temperature sensor 88 for detecting the coolant temperature of the engine 10, an airflow sensor 89 for detecting the intake air amount of the engine 10, and an air-fuel ratio sensor 90 for detecting the air-fuel ratio from the oxygen concentration of the exhaust gas. Furthermore, the engine control unit 83 is equipped with a start switch 91 that is manually operated when starting or stopping the control system 80.

[0013] Figure 4 shows an example of the basic structure of the engine control unit 83. As shown in Figure 4, the engine control unit 83, which is an electronic control unit, has a microcontroller 102 that incorporates a processor 100 and a main memory (memory) 101, etc. A predetermined program is stored in the main memory 101, and the program is executed by the processor 100. The processor 100 and the main memory 101 are connected to each other so as to be able to communicate with each other. Note that the microcontroller 102 may incorporate multiple processors 100, and the microcontroller 102 may also incorporate multiple main memories 101.

[0014] The engine control unit 83 also includes an input circuit 103, a drive circuit 104, a communication circuit 105, an external memory 106, and a power supply circuit 107. The input circuit 103 converts signals input from various sensors into signals that can be input to the microcontroller 102. The drive circuit 104 generates drive signals for various devices such as injectors 37 and spark plugs 38 based on signals output from the microcontroller 102. The communication circuit 105 converts signals output from the microcontroller 102 into communication signals for other electronic control units. The communication circuit 105 also converts communication signals received from other electronic control units into signals that can be input to the microcontroller 102. The power supply circuit 107 supplies a stable power supply voltage to the microcontroller 102, input circuit 103, drive circuit 104, communication circuit 105, and external memory 106. The external memory 106, which consists of non-volatile memory, stores programs and various data.

[0015] [Ignition control] The engine control device according to this embodiment is characterized by its ability to optimize ignition timing even when the number of injection stages is increased according to the engine state. Engine state can be described as, for example, the coolant temperature.

[0016] As background, engine exhaust gases contain particulate matter (PM), and there is a need to reduce the number of particulate matter particles (PN) in the exhaust gas. Conventionally, when the engine coolant temperature is low, fuel injection is performed in a single stage, but there has been a demand to increase the number of injection stages in order to reduce PN.

[0017] However, with conventional control methods, when multi-stage injection is used to reduce PN, the number of injection stages changes depending on the water temperature even if the engine operating point is the same, making it impossible to set the ignition timing according to whether or not multi-stage injection is used. In addition, with conventional control methods, the timing of switching between injection and ignition cannot be synchronized, so there was a possibility that the ignition timing would not be appropriate for the first few cycles immediately after switching the injection stage. Furthermore, as described in "Problems that the invention aims to solve" above, the MBT shifting results in retardation, which also presented the problem of not achieving optimal ignition timing.

[0018] Therefore, in the engine control device according to the present invention, in order to achieve both PN reduction by increasing the number of injection stages and combustion stability, the control system 80 stores two types of injection stage maps corresponding to the coolant temperature of the engine 10 (Figures 5A and 5B) and three types of ignition timing maps corresponding to the number of injection stages of the injector 37 (Figures 6A, 6B, and 6C), and performs ignition control (Figure 7) by selecting one of these maps (i.e., switching between these maps).

[0019] Figure 5A shows an example of an injection stage map during normal operation, and Figure 5B shows an example of an injection stage map at low water temperature. The injection stage map is a graph with engine load on the vertical axis and engine speed on the horizontal axis, and the injection stage of the injector 37 is determined for each engine operating point determined by the engine load and engine speed. Although not shown in the injection stage map, the injection pulse width, which represents the time for fuel injection, is also determined for each engine operating point.

[0020] Figure 5A is the map selected after the warm-up period is complete, i.e., when the coolant temperature of the engine 10 has risen. Figure 5B is the map selected during the warm-up period, i.e., when the coolant temperature of the engine 10 is low. The coolant temperature of the engine 10 is detected by the water temperature sensor 88. The switching timing between the two maps (i.e., at what temperature to switch) can be set arbitrarily.

[0021] During normal operation, as shown in Figure 5A, three-stage injection is performed at each engine operating point in region E3 where the engine load is high and the engine speed is high. In addition, two-stage injection is performed at each engine operating point in region E2 (excluding region E3) where the engine load is moderate or higher and the engine speed is moderate or higher. Furthermore, one-stage injection is performed at each engine operating point in region E1 (i.e., the region where the engine load is low and the engine speed ranges from low to high, and the region where the engine speed is low and the engine load ranges from low to high), excluding regions E3 and E2.

[0022] On the other hand, at low water temperatures, as shown in Figure 5B, three-stage injection is performed in region E3 and two-stage injection in region E2, but in region E1, two-stage injection is performed in order to achieve both PN reduction and combustion stability. In other words, comparing Figure 5A and Figure 5B, at low water temperatures, the number of injection stages is increased in region E1.

[0023] Figure 6A shows an example of an ignition timing map for single-stage injection, Figure 6B shows an example of an ignition timing map for two-stage injection, and Figure 6C shows an example of an ignition timing map for three-stage injection. The ignition timing map is a table with engine load on the vertical axis and engine speed on the horizontal axis, and the ignition timing of the spark plug 38 is determined for each engine operating point determined by these engine load and engine speed values. The ignition timing is expressed as the number of degrees advanced from top dead center.

[0024] As shown in Figure 6A, the ignition timing for single-stage injection is set to X°. Figure 6A is the first ignition timing map corresponding to the first injection stage. As shown in Figure 6C, the ignition timing for triple-stage injection is set to Z°.

[0025] As shown in Figure 6B, in the case of two-stage injection, the ignition timing is set to Y° for region E2, and for region E1, which is multi-staged in two-stage injection, it is set to advance α° from X° in Figure 6A. Figure 6B is the second ignition timing map corresponding to the second injection stage, which is greater than the first injection stage. Thus, the ignition timing in region E1, where the number of injection stages is multi-stage, is set to advance more than the ignition timing in the first ignition timing map, resulting in a suitable ignition timing.

[0026] Figure 7 is a flowchart showing an example of ignition control. Each step shown in the flowchart of Figure 7 represents a process performed by the processor 100 that constitutes the control system 80.

[0027] In step S11, the processor 100 determines whether the coolant temperature of the engine 10 is low. Specifically, the processor 100 determines whether the detection result of the water temperature sensor 88 is a preset water temperature. (Threshold) The following is determined: If it is determined in S11 that the water temperature is low (Yes), the low water temperature injection stage map shown in Figure 5B is selected as the injection stage map, and the process proceeds to step S14. On the other hand, if it is determined in S11 that the water temperature is not low (No), the normal operation injection stage map shown in Figure 5A is selected as the injection stage map, and the process proceeds to step S14.

[0028] In step S14, the processor 100 identifies the cylinder whose ignition will be confirmed next. Figure 8 shows the relationship between the crank angle and the injection and ignition confirmation timings for each cylinder. In each of the four cylinders 23 (1st to 4th cylinders), injection by the injector 37 is confirmed midway through the exhaust stroke (BTDC 390°), as indicated by the white arrows, and ignition by the spark plug 38 is confirmed before the compression stroke (BTDC 180°), as indicated by the black arrows. Therefore, based on the detection result of the crank rotation sensor 87, the cylinder whose ignition will be confirmed next can be identified. For example, at the timing shown on line AA, the cylinder whose ignition will be confirmed next is the 3rd cylinder. In this way, for cylinders whose injection has already been confirmed, the ignition timing can be determined according to the injection stage.

[0029] In steps S15 and S16, the processor 100 determines whether the number of injection stages for the cylinder identified in step S14 is 1 stage, 2 stages, or something else. Specifically, the processor 100 determines the number of injection stages based on the injection pulse width set for each engine operating point in the injection stage map selected in step S12 or step S13.

[0030] In step S15, the processor 100 determines whether the injection stage of the cylinder identified in step S14 is 1 stage. If it is determined in step S15 that it is 1-stage injection (Yes), in step S17, it selects the 1-stage injection ignition map shown in Figure 6A, in step S20, it identifies the ignition timing at the current engine operating point based on the 1-stage injection ignition map, and in step S21, it commands the spark plug 38 to ignite at the identified ignition timing, and terminates the process.

[0031] If the processor 100 determines in step S15 that it is not a single-stage injection (No), then in step S16 it determines whether the number of injection stages for the cylinder identified in step S14 is two. If it determines in step S16 that it is not a two-stage injection (No), then in step S19 it selects the ignition map for three-stage injection shown in Figure 6C, and in step S20 it identifies the ignition timing at the current engine operating point based on the ignition map for three-stage injection, and in step S21 it commands the spark plug 38 to ignite at the identified ignition timing, and then terminates the process.

[0032] If the processor 100 determines in step S16 that it is a two-stage injection system (Yes), in step S18 it selects the two-stage injection ignition map shown in Figure 6B, in step S20 it identifies the ignition timing at the current engine operating point based on the two-stage injection ignition map, and in step S21 it commands the spark plug 38 to ignite at the identified ignition timing, thus ending the process. In the case of this two-stage injection system, as shown in Figure 6B, the ignition timing during normal operation is Y° in region E2, and the ignition timing at low water temperature is advanced by α° from X° in region E1.

[0033] As described above, the control system 80 of this embodiment determines the number of injection stages of the injector 37 (S15, S16), controls the ignition timing of the spark plug 38 based on the first ignition timing map (Figure 6A) when the number of injection stages is the first injection stage (1st stage) (S17, S20, S21), and controls the ignition timing of the spark plug based on the second ignition timing map (Figure 6B) when the number of injection stages is the second injection stage (2nd stage) (S18 or S19, S20, S21).

[0034] According to this, the ignition timing is controlled based on an ignition timing map corresponding to the number of injection stages, so even if the number of injection stages is increased according to the engine condition, the ignition timing can be optimized. In addition, since the ignition timing of the second ignition timing map is set to be more advanced than the ignition timing of the first ignition timing map, unintentional retardation is prevented, and an optimal ignition timing can be achieved. Furthermore, since the number of injection stages of the injector 37 is controlled according to the coolant temperature of the engine 10, both PN reduction and combustion stability can be achieved. In addition, since the number of injection stages is determined for each of the multiple cylinders, precise control can be performed.

[0035] [Differentiation] The present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the invention.

[0036] In the above embodiment, as shown in Figure 5B, an example was described in which the number of injection stages is multi-staged (changed from 1 stage to 2 stages) throughout the entire region E1. However, the multi-staged injection may be applied only to a part of region E1.

[0037] In the above embodiment, as shown in Figure 5B, an example was described in which the number of injection stages in region E1 was changed from one stage to two stages. However, this increase in stages may also be changed to three stages.

[0038] In the above embodiment, as shown in Figure 6B, we have described an example where the ignition timing in region E1 is uniformly advanced by α° regardless of the engine operating point. However, the degree of advance may differ for each engine operating point.

[0039] In the above embodiment, as shown in Figure 6B, an example was described in which region E1 changes from one-stage injection to two-stage injection at low water temperature. However, as shown in Figure 9A, region E2 may also change from two-stage injection to three-stage injection. Figure 9A shows a modified example of the injection stage map at low water temperature.

[0040] In this case, as shown in Figure 9B, the ignition timing in region E2 is advanced by β° from X°. Figure 9B shows a modified example of the ignition timing map for three-stage injection. Note that the ignition timing in region E2 is not limited to the example where it is uniformly advanced by β° regardless of the engine operating point; the degree of advance may differ for each engine operating point.

[0041] In this case, the ignition timing map for two-stage injection shown in Figure 6B is the first ignition timing map, and the ignition timing map for three-stage injection shown in Figure 9B is the second ignition timing map corresponding to a second injection stage that is greater than the first injection stage.

[0042] In the above embodiment, an example was described in which the control of the injection stage according to the state of the engine 10 is performed according to the coolant temperature, but it may also be performed according to other states, for example. [Explanation of symbols]

[0043] 10 Engines 11 vehicles 32 Combustion chamber 37 Injectors 38 Spark plugs 80 Control Systems 83 Engine control unit 87 Crank rotation sensor 88 Water temperature sensor 100 processors 101 Main memory (memory)

Claims

1. An engine control device for controlling an engine that includes an injector for injecting fuel into a combustion chamber and a spark plug for igniting the fuel-air mixture in the combustion chamber, It has a memory and a processor that are connected to each other in a manner that allows them to communicate with each other, and a control system that controls the ignition timing of the spark plug, The control system stores an ignition timing map in which the ignition timing is set for each engine operating point, which includes a first ignition timing map corresponding to the first injection stage of the injector, and a second ignition timing map corresponding to a second injection stage that is greater than the first injection stage. The ignition timing of the second ignition timing map is set to be more advanced than the ignition timing of the first ignition timing map. The control system is When the coolant temperature of the engine exceeds a threshold, it is determined that the injection stage of the injector is the first injection stage. When the coolant temperature of the engine falls below the threshold, it is determined that the injection stage of the injector is the second injection stage. When the number of injection stages of the injector is the first injection stage, the ignition timing of the spark plug is controlled based on the first ignition timing map. When the injection stage number of the injector is the second injection stage number, the ignition timing of the spark plug is controlled based on the second ignition timing map. Engine control device.

2. In the engine control device according to claim 1, The engine comprises a plurality of cylinders having the combustion chambers, The control system determines the number of injection stages of the injector for each cylinder. Engine control device.

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