Internal combustion engine control device

Abstract

A control device for an internal combustion engine is provided, which can reduce PN emissions at low temperatures. The control device of the present invention reduces the load on the internal combustion engine and increases its rotational speed when the cooling water temperature is low, compared to when the water temperature is high.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] Patent document 1 discloses a technology that uses low-temperature cooling water to cool an engine and suppresses engine load to reduce emissions during catalyst preheating delay.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2010 / 079609. Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Under engine operating conditions, at low temperatures where fuel volatility deteriorates (conditions where the engine block, lubricating oil, and cooling water all become cold) and when the engine load is high, there is a problem of increased particulate number (PN) in the exhaust gas.

[0008] The present invention was made in view of the above-mentioned problems, and its object is to provide a control device for an internal combustion engine that can reduce PN (particulate number) emissions at low temperatures.

[0009] Methods for solving problems

[0010] In order to solve the above-mentioned problems and achieve the objectives, the control device for an internal combustion engine of the present invention is characterized in that, when the temperature of the cooling water for cooling the internal combustion engine is low, compared with when the water temperature is high, the control is performed to reduce the load of the internal combustion engine and increase the speed of the internal combustion engine.

[0011] Therefore, at low temperatures where fuel volatility deteriorates, by reducing the engine load, operation in high-load areas with higher PN emissions can be avoided, thereby reducing PN emissions at such low temperatures.

[0012] Furthermore, as described above, the control can avoid operating the internal combustion engine in a specified low-speed, high-load region where the PN discharge from the internal combustion engine is above a specified amount.

[0013] Therefore, by avoiding the specified low-speed and high-load range and minimizing the increase in engine speed, the noise associated with the increase in engine speed can be suppressed.

[0014] Furthermore, in the above, it is possible that the control uses the engine's operating point mapping, which represents the relationship between the water temperature and the engine's load and speed, to determine the engine's load and speed.

[0015] Therefore, it is possible to determine the load and speed of the internal combustion engine corresponding to the water temperature of the cooling water used to cool the engine.

[0016] Invention Effects

[0017] The control device for the internal combustion engine of the present invention has the following effect: by reducing the load at low temperatures where the volatility of fuel deteriorates, it can avoid operation in high-load areas where the PN emission is large, and can reduce the PN emission at low temperatures. Attached Figure Description

[0018] Figure 1 This is a control system diagram of the engine involved in the implementation method.

[0019] Figure 2 This is a diagram showing the region of PN discharge when the engine coolant is at a low temperature.

[0020] Figure 3 This is a diagram showing the region of PN discharge when the engine coolant is at a medium temperature.

[0021] Figure 4 This is a diagram showing the region of PN discharge when the engine is fully warmed up.

[0022] Figure 5 This is a diagram showing the engine action line in the first control example of PN suppression control.

[0023] Figure 6 This is a diagram showing the engine action line in the second control example of PN suppression control.

[0024] Figure 7 This is a diagram illustrating a general control flow for PN suppression control.

[0025] Figure 8 This is a graph showing the time diagrams of the first control example with PN suppression control, the second control example, and the control without PN suppression control.

[0026] Figure 9 This is a graph showing the time curves for catalyst preheating control only and PN suppression control.

[0027] Figure 10 This is a flowchart illustrating an example of PN suppression control implemented by an electronic control device. Detailed Implementation

[0028] The following describes embodiments of the control device for an internal combustion engine according to the present invention. It should be noted that this invention is not intended to be limited by these embodiments.

[0029] Figure 1 This is a control system diagram of engine 1 according to the implementation method. For example... Figure 1 As shown, in the internal combustion engine 1 installed in the vehicle, the intake passage 21 and the exhaust passage 22 are respectively connected. The intake passage 21 is equipped with an air filter 6 for filtering the intake air, an air volume detection unit (air flow sensor 5) for detecting the amount of intake air, and a throttle valve (not shown) for adjusting the amount of intake air (engine load). The exhaust passage 22 is equipped with a catalytic converter 7 for purifying the exhaust gas discharged from the engine 1 and a muffler 8.

[0030] Furthermore, the engine 1 is equipped with a rotation sensor 4 for detecting the engine speed and a water temperature sensor 3 for detecting the temperature of the engine coolant cooling the engine 1. The rotation sensor 4 detects the engine speed, for example, based on the rotation angle or rotation speed of the flywheel 12 provided at the end of the crankshaft 11 of the engine 1. The water temperature sensor 3 detects, for example, the temperature of the engine coolant flowing in a cooling device (not shown) provided in the engine 1.

[0031] Engine speed signals from rotation sensor 4 and coolant temperature signals from coolant temperature sensor 3 are input to electronic control unit 2, which controls engine 1. Additionally, intake air volume signals from airflow sensor 5 and throttle opening signals from a throttle sensor (not shown) that detects throttle opening are also input to electronic control unit 2. Furthermore, electronic control unit 2 can control the operating state (speed and load) of engine 1 based on these various signals.

[0032] Next, use Figure 2 , Figure 3 as well as Figure 4 This section provides a summary of the PN discharge volume when engine 1 is running. Figure 2 This is a diagram showing the region of PN discharge when the engine coolant is at a low temperature. Figure 3 This is a diagram showing the region of PN discharge when the engine coolant is at a medium temperature. Figure 4 This is a diagram showing the region of PN discharge when engine 1 is fully preheated. It should be noted that... Figure 2 as well as Figure 3 The label L1 indicates the boundary line between regions with particularly high PN discharge and regions with low PN discharge at low water temperatures. Furthermore, Figure 2 as well as Figure 3The label L2 in the diagram shows the boundary line between the region with particularly high PN discharge and the region with relatively low PN discharge at medium water temperature.

[0033] like Figure 2 as well as Figure 3 As shown, there is a tendency for the PN discharge to increase as the engine 1 operates at lower speeds and higher loads. It is known that increasing the load on engine 1 increases PN discharge, but conversely, increasing the engine speed can reduce PN discharge. Furthermore, as... Figure 2 , Figure 3 as well as Figure 4 As shown, the lower the engine coolant temperature, the larger the area of ​​PN discharge that is particularly large on the low speed side and high load side of engine 1. As engine 1 preheats, the area with a large PN discharge shrinks as the engine coolant temperature rises.

[0034] Therefore, the electronic control unit 2 can perform PN suppression control to reduce the amount of PN emitted during engine operation. This PN suppression control limits the load on the engine 1 based on the engine coolant temperature, controlling the engine 1 to operate in a manner that avoids areas with particularly high PN emissions when the engine coolant temperature is low. In other words, the electronic control unit 2, as PN suppression control, can perform the following control: when the engine coolant temperature is low, compared to when the engine coolant temperature is high, it reduces the load on the engine 1 and increases the engine speed, thus avoiding a predetermined low-speed, high-load area where the amount of PN emitted from the engine 1 exceeds a specified amount, thereby enabling the engine 1 to operate.

[0035] Figure 5 This is a diagram showing the operating point mapping of engine 1 in the first control example of PN suppression control. Electronic control unit 2, for example, serves as the first control example of PN suppression control, such as... Figure 5 As shown, regardless of the engine speed, the load on engine 1 is consistently reduced to a level that avoids areas with excessive PN discharge, based on the engine coolant temperature. Furthermore, to ensure the required output of engine 1, the engine speed is controlled at actuation point P1 at low coolant temperature, at actuation point P2 at medium coolant temperature, and at actuation point P3 during full preheating. In the first example of PN suppression control, the lower the engine coolant temperature, the smaller the load on engine 1, thus increasing the engine speed to achieve the same required output.

[0036] Figure 6 This is a diagram illustrating the engine action lines in the second control example of PN suppression control. It should be noted that... Figure 6 The required output is shown. Figure 5 The output requirements are the same. As a characteristic of PN discharge, when the engine speed of engine 1 is increased, the PN discharge can be reduced even under high load conditions. Therefore, the electronic control device 2 can control the operating state of engine 1 as follows: That is, the electronic control device 2 can be used, for example, as a second control example for PN suppression control. Figure 6 The following controls are implemented as shown: Low speed and high load are avoided in a manner that minimizes the increase in engine speed and reduces PN discharge; the speed and load of engine 1 are limited based on the engine coolant temperature. Figure 6 In this system, the electronic control unit 2 controls the load and speed of engine 1 at actuation point P11 when the water temperature is low, at actuation point P12 when the water temperature is medium, and at actuation point P13 when the engine is fully preheated. It should be noted that actuation point P11 is... Figure 5 Compared to the action point P1 with high load and low speed, the action point P12 is... Figure 5 Compared to the action point P2 with high load and low speed, action point P13 is... Figure 5 The operating point P3 shown is the same as the operating point with the same load and speed.

[0037] Thus, in the second control example of PN suppression control, compared with the first control example, for the same required output of engine 1, the load of engine 1 can be increased in the region with less PN discharge. Therefore, in the second control example of PN suppression control, by suppressing the increase in engine speed to a minimum, the deterioration of noise caused by the increase in engine speed can be suppressed.

[0038] Figure 7 This is a diagram illustrating a general control flow for PN suppression control. (As shown...) Figure 7As shown, the electronic control unit 2 determines the load (torque) and speed of the engine 1 based on the user's output request generated by the amount of accelerator pedal depressing, and the engine coolant temperature (engine water temperature). This determination utilizes an engine 1 operating point mapping, which represents the relationship between the engine coolant temperature, the engine load, and the engine speed, and can reduce PN discharge. It should be noted that multiple engine 1 operating point mappings are pre-determined through experiments according to the coolant temperature or temperature range of each engine, and these multiple obtained operating point mappings are pre-stored in a storage device provided in the electronic control unit 2. Furthermore, in hybrid vehicles that have an electric motor in addition to the engine 1 to generate drive force for vehicle propulsion, the output request to the engine 1 can be reduced by the assistance of the electric motor.

[0039] Figure 8 This is a time graph showing the first control example with PN suppression control, the second control example, and the time graph without PN suppression control. It should be noted that... Figure 8 In the first control example and the second control example of PN suppression control and the control without PN suppression, the required output of engine 1 is the same.

[0040] like Figure 8 As shown, in the PN suppression control, the engine speed of engine 1 can be made to the lowest possible speed, thus suppressing noise the most. However, the engine 1 is operated at the engine operating point in the region where the PN emission is particularly high on both the low and high speed sides, resulting in the highest PN emission. On the other hand, in the first and second control examples of PN suppression control, engine 1 is operated at the engine operating point that avoids the region where the PN emission is particularly high, therefore... Figure 8 As shown, both methods can reduce PN emissions compared to the case without PN suppression control. Furthermore, in the first and second control examples of PN suppression control, the PN emissions are approximately the same; however, it is evident that the second control example, which increases the load on engine 1 and reduces the speed of engine 1, is better at suppressing noise than the first control example.

[0041] Next, the points of change between emission reduction controls and emission control will be explained.

[0042] Catalyst preheating is used to limit engine speed and load when the engine is cold. The differences and distinctions between the control methods and catalyst preheating control involved in this embodiment are defined.

[0043] Figure 9 This is a graph showing the timelines of control with only catalyst preheating and control with PN suppression.

[0044] The electronic control unit 2 effectively purifies HC, CO, and NOx (hereinafter referred to as the three components) contained in the exhaust gas through the catalyst, and therefore can perform catalyst preheating control, which is used to improve the activity of the catalyst provided in the catalyst unit 7 by preheating it with exhaust gas. In catalyst preheating control, the temperature of the catalyst is measured or estimated, and the control of "load suppression" and "ignition timing delay" continues until the temperature of the catalyst reaches the activity temperature Tc, and the engine 1 is operated. Furthermore, after the temperature of the catalyst reaches the activity temperature Tc and the catalyst becomes active, the load of the engine 1 is not suppressed, and the engine 1 is operated with a load corresponding to the output requirements. On the other hand, since PN cannot be purified in the catalyst, the amount of PN emitted cannot be reduced in catalyst preheating control. Therefore, as Figure 9 As shown, under the condition of catalyst preheating suppression only, if the required load at the end of catalyst preheating is high, the engine 1 is run at a higher load, and the PN discharge increases.

[0045] The higher the temperature of engine 1, in other words, the higher the temperature of the engine coolant, the lower the PN discharge rate. Therefore, in PN suppression control, the engine coolant temperature is monitored, and control continues until it exceeds the temperature Tp that reduces the PN discharge rate and eliminates the need for output suppression of engine 1.

[0046] It should be noted that, typically, the catalyst reaches its activation temperature (Tc) earlier than the engine coolant temperature rises to the point where PN discharge decreases. Furthermore, prolonged catalyst preheating control is not preferable due to a significant deterioration in fuel economy. Therefore, as... Figure 9 As shown in the PN suppression control example, when both catalyst preheating control and PN suppression control are required simultaneously, it is preferable to prioritize catalyst preheating control and perform PN suppression control after catalyst preheating control has ended. It should be noted that during catalyst preheating control, the load on engine 1 is generally low, and essentially does not reach the load required for increased PN emissions. Therefore, even if catalyst preheating control is implemented before PN suppression control, PN emissions can still be reduced.

[0047] Figure 10This is a flowchart illustrating an example of PN suppression control implemented by the electronic control unit 2. First, the electronic control unit 2 determines whether the engine is on (step S1). If the electronic control unit 2 determines that the engine is not on (no in step S1), it terminates a series of control steps. On the other hand, if the electronic control unit 2 determines that the engine is on (yes in step S1), it determines whether the catalyst preheating control is off (step S2). If the electronic control unit 2 determines that the catalyst preheating control is not off (no in step S2), it terminates a series of control steps. On the other hand, if the electronic control unit 2 determines that the catalyst preheating control is off (yes in step S2), it obtains the engine coolant temperature (step S3). Next, the electronic control unit 2 obtains the output requirements of the engine 1 (step S4). Then, the electronic control unit 2 determines the engine load and speed based on the engine 1's operating point mapping, which represents the relationship between the engine coolant temperature, engine 1 load, and engine 1 speed, which can reduce PN discharge (step S5). Next, the electronic control unit 2 controls the operation of the engine 1 based on the determined load and speed (step S6). Then, the electronic control unit 2 terminates a series of control operations.

[0048] The electronic control unit 2 reduces the load on the engine 1 at low temperatures where fuel volatility deteriorates by implementing PN suppression control, thereby avoiding the operation of the engine 1 in high-load areas where PN emissions are high, and reducing PN emissions at the low temperatures.

[0049] Explanation of reference numerals in the attached figures

[0050] 1. Engine

[0051] 2 Electronic control device

[0052] 3. Water temperature sensor

[0053] 4. Rotation sensor

[0054] 5. Air Flow Sensor

[0055] 6. Air Filter

[0056] 7. Catalyst Unit

[0057] 8. Muffler

[0058] 11 Crankshaft

[0059] 12 Flywheel

[0060] 21. Intake passage

[0061] 22. Exhaust passage.

Claims

1. A control device for an internal combustion engine, characterized in that, Capable of executing: Catalyst preheating control improves activity by preheating the catalyst in a catalyst device with exhaust gas, wherein the catalyst device purifies the exhaust gas discharged from the internal combustion engine. as well as When the cooling water temperature of the internal combustion engine is low, particulate number suppression control reduces the load on the internal combustion engine and increases its speed compared to when the water temperature is high. When both catalyst preheating control and particulate number suppression control are required simultaneously, catalyst preheating control is prioritized, and particulate number suppression control is performed after catalyst preheating control has ended.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The particulate number suppression control avoids operating the internal combustion engine in a specified low-speed, high-load region where the particulate number emitted from the internal combustion engine exceeds a specified amount.

3. The control device for an internal combustion engine according to claim 1 or 2, characterized in that, The particulate number suppression control utilizes an engine operating point mapping that represents the relationship between the water temperature and the engine load and engine speed to determine the engine load and engine speed.

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