Control device for internal combustion engines

Abstract

The present invention provides a control device for an internal combustion engine that can suppress abnormal combustion caused by an excessively long fuel injection period. [Solution] The control device for the internal combustion engine calculates a torque upper limit such that the lower the fuel pressure in the fuel tank detected by the tank pressure sensor, the smaller the torque upper limit becomes. The control device for the internal combustion engine compares the requested torque with the torque upper limit, and if the requested torque is less than or equal to the torque upper limit (step S140: YES), it sets the fuel injection period to inject the amount of fuel necessary to generate the torque corresponding to the requested torque. On the other hand, if the requested torque is greater than the torque upper limit (step S140: NO), the control device for the internal combustion engine sets the fuel injection period to inject the amount of fuel necessary to generate the torque corresponding to the torque upper limit. The control device for the internal combustion engine controls the injector based on the set fuel injection period (step S120).

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a control device for an internal combustion engine that burns a fuel containing hydrogen. The control device for the internal combustion engine detects the temperature and pressure of the fuel supplied from the fuel tank to the injector, and adjusts the valve opening time of the injector that injects fuel into the cylinder in one cycle of one cylinder according to the temperature and pressure. That is, the injection period of the fuel by the injector is adjusted. When the fuel tank pressure is low, the control device for the internal combustion engine lengthens the injection period to ensure the injection amount, so that a desired amount of fuel can be injected from the injector.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the injection period becomes excessively long, an ideal mixture of hydrogen and air cannot be formed in the combustion chamber, and abnormal combustion may occur.

Means for Solving the Problems

[0005] Hereinafter, the means for solving the above problems and their effects will be described. The control device for an internal combustion engine to solve the above problems includes a processing circuit. The processing circuit calculates a torque upper limit such that the lower the fuel pressure in the fuel tank detected by a tank pressure sensor that detects the fuel pressure in the fuel tank, the smaller the torque upper limit becomes. The processing circuit compares the requested torque with the torque upper limit and sets the fuel injection period of the internal combustion engine's injector so that if the requested torque is less than or equal to the torque upper limit, it injects the amount of fuel necessary to generate the torque equivalent to the requested torque. On the other hand, if the requested torque is greater than the torque upper limit, the processing circuit sets the fuel injection period of the internal combustion engine's injector so that it injects the amount of fuel necessary to generate the torque equivalent to the torque upper limit. The injector of the internal combustion engine is controlled based on the fuel injection period set by the processing circuit. [Effects of the Invention]

[0006] The control device for the internal combustion engine described above can prevent the fuel injection period from becoming excessively long, thereby suppressing abnormal combustion. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram illustrating a fuel injection system for a vehicle equipped with a control device for an internal combustion engine according to an embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating the process that determines the fuel injection duration of the internal combustion engine injector in a vehicle's fuel injection system. [Figure 3] Figure 3 is a schematic diagram illustrating the process of determining the torque upper limit using the control device for the internal combustion engine according to the embodiment. [Figure 4] Figure 4 is a flowchart illustrating the sequence of processes involved in controlling the injector by the control device for the internal combustion engine according to this embodiment. [Modes for carrying out the invention]

[0008] The control device 40 for the internal combustion engine 30 according to the embodiment will be described below with reference to Figures 1 to 4. <Vehicle fuel injection system> The control device 40 for the internal combustion engine 30 according to this embodiment is mounted on a vehicle and constitutes the vehicle's fuel injection system. The control device 40 includes a processing circuit 41. The processing circuit 41 performs various processes for controlling the internal combustion engine 30. As shown in Figure 1, the vehicle's fuel injection system includes, in order from the fuel tank 10 side, a tank shut-off valve 11, a pressure reducing valve 14, a relief valve 20, a delivery shut-off valve 21, and the internal combustion engine 30 in the fuel supply line. The internal combustion engine 30 includes a delivery pipe 31, an injector 34, and an output shaft 35.

[0009] The fuel tank 10 is a container for storing hydrogen, which is used when the vehicle operates under high pressure. The tank shut-off valve 11 is a valve that controls the flow of hydrogen from the fuel tank 10. When the vehicle starts operating, the tank shut-off valve 11 opens and hydrogen is released from the fuel tank 10.

[0010] The hydrogen supplied from the fuel tank 10 is under very high pressure, and the pressure reducing valve 14 is a valve that reduces this high pressure to an appropriate level. The pressure reducing valve 14 reduces the pressure of the hydrogen from the fuel tank 10, adjusting it to a pressure suitable for fuel injection from the injector 34. A tank pressure sensor 12 is installed in the fuel supply line between the tank shut-off valve 11 and the pressure reducing valve 14 to monitor the pressure of the hydrogen in the fuel tank 10. A tank temperature sensor 13 is also installed in the fuel supply line between the tank shut-off valve 11 and the pressure reducing valve 14 to monitor the temperature of the hydrogen in the fuel tank 10.

[0011] The relief valve 20 is closed during normal operation, but opens to release excess pressure if the pressure in the fuel injection line becomes abnormally high. In this way, the pressure in the fuel injection system is ensured to remain within a safe range.

[0012] The delivery shut-off valve 21 shuts off the hydrogen supply when the engine is stopped. On the other hand, when the engine starts, the delivery shut-off valve 21 opens and supplies hydrogen to the delivery pipe 31. The delivery shut-off valve 21 also shuts off the hydrogen supply in emergencies. The delivery pipe 31 is a passage for transporting hydrogen to the injector 34. The delivery pipe 31 is fitted with a delivery pressure sensor 32 that monitors the hydrogen pressure inside the delivery pipe 31, and a delivery temperature sensor 33 that monitors the hydrogen temperature inside the delivery pipe 31.

[0013] The injector 34 opens and closes according to the operating state of the internal combustion engine 30, supplying hydrogen to the combustion chamber. The internal combustion engine 30 generates power by mixing hydrogen and air and burning it. When hydrogen is supplied from the injector 34, the combustion process in the internal combustion engine 30 begins. The energy generated by this combustion becomes the driving force of the vehicle as the rotational force of the output shaft 35. The engine rotation speed sensor 36 measures the engine rotation speed. The engine rotation speed is the rotational speed of the output shaft 35. The engine rotation speed is used for output control and fuel supply adjustment of the internal combustion engine 30.

[0014] The control device 40 of the internal combustion engine 30 processes information from sensors from the fuel tank 10 to the injector 34, and controls the optimization of hydrogen supply, adjustment of the operation of the internal combustion engine 30, and activation of safety functions. In this way, the process of supplying hydrogen from the fuel tank 10 to the combustion chamber via the injector 34 and using it as power for the vehicle is completed.

[0015] <Process for determining the fuel injection interval of the injector 34 of the internal combustion engine 30> Figure 2 shows the process by which the processing circuit 41 of the control device 40 determines the fuel injection period of the injector 34 of the internal combustion engine 30. As shown in Figure 2, the processing circuit 41 uses the accelerator opening, vehicle speed, and gear position to calculate how much torque the internal combustion engine 30 is required to generate. This calculation determines the "required torque." The required torque is the torque that the internal combustion engine 30 should generate according to the current driving conditions of the vehicle, such as the accelerator opening, vehicle speed, and gear position.

[0016] Next, the processing circuit 41 calculates the required injection amount, which is the amount of fuel to be injected from the injector 34, based on the required torque calculated as described above. The required injection amount is the amount of fuel injected in one cycle of one cylinder necessary to achieve the required torque. After calculating the required injection amount, the processing circuit 41 uses the calculated required injection amount, the fuel pressure in the delivery pipe 31, the fuel temperature, and the engine rotation speed to determine the fuel injection period corresponding to the required injection amount. The fuel injection period is determined by the opening and closing times of the injector 34. By determining the opening and closing times of the injector 34, the processing circuit 41 determines when fuel injection occurs and the fuel injection period, which is the duration of fuel injection.

[0017] In this way, the processing circuit 41 controls the operation of the injector 34 using information from multiple sensors, such as the delivery pressure sensor 32, the delivery temperature sensor 33, and the engine rotation speed sensor 36. Furthermore, the processing circuit 41 also uses information from the tank pressure sensor 12 and the tank temperature sensor 13 to finely control the operation of the injector 34. The control of the injector 34 using information from the tank pressure sensor 12 will be described later.

[0018] The control device 40 of the internal combustion engine 30 ensures optimal fuel supply according to the vehicle's operating conditions. As described above, starting from the calculation of the required torque, the injection timing and fuel injection period of the injector 34 are finally determined. By operating the injector 34 so as to realize the determined injection timing and fuel injection period, the internal combustion engine 30 generates a torque corresponding to the required torque.

[0019] Also, the control device 40 of the internal combustion engine 30 sets a torque upper limit value and generates torque within a range not exceeding the torque upper limit value. <Process of determining the torque upper limit value by the control device 40 of the internal combustion engine 30> FIG. 3 shows a process of determining the torque upper limit value by the control device 40 of the internal combustion engine 30. This process is executed by the processing circuit 41 of the control device 40.

[0020] As shown in FIG. 3, first, the processing circuit 41 calculates a flow rate upper limit value using the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 and the fuel pressure in the delivery pipe 31 detected by the delivery pressure sensor 32. The control device 40 stores a flow rate upper limit value calculation map designed to be able to output a flow rate upper limit value by inputting the pressure in the fuel tank 10 and the pressure in the delivery pipe 31. The flow rate upper limit value is the maximum fuel flow rate that can be supplied to the injector 34 estimated from the fuel pressure in the fuel tank 10 and the fuel pressure in the delivery pipe 31. The flow rate upper limit value calculation map is an arithmetic map that stores the flow rate upper limit value corresponding to the combination of the fuel pressure in the fuel tank 10 and the fuel pressure in the delivery pipe 31. The flow rate upper limit value calculation map is designed based on the results of experiments or simulations performed at the design stage such that the lower the fuel pressure in the fuel tank 10, the smaller the output flow rate upper limit value, and the lower the fuel pressure in the delivery pipe 31, the smaller the output flow rate upper limit value.

[0021] Next, the processing circuit 41 calculates the injection amount limit using the calculated flow rate limit and engine rotation speed. The control device 40 stores an injection amount limit calculation map that is designed to output the injection amount limit by inputting the flow rate limit and engine rotation speed. The injection amount limit is the maximum amount of fuel that can be injected from the injector 34, estimated from the flow rate limit and engine rotation speed. The injection amount limit calculation map is designed based on the results of experiments or simulations conducted during the design phase, such that the injection amount limit decreases as the flow rate limit decreases and as the engine rotation speed increases.

[0022] The processing circuit 41 then calculates the torque limit using the calculated injection amount limit and engine rotation speed. The control device 40 stores a torque limit calculation map that is designed to output the torque limit by inputting the injection amount limit and engine rotation speed. The torque limit is the maximum torque that the engine can generate, estimated from the injection amount limit and engine rotation speed. The torque limit calculation map is designed based on the results of experiments or simulations conducted during the design phase, such that the torque limit decreases as the injection amount limit decreases and as the engine rotation speed increases.

[0023] <Control of the injector 34 by the control device 40> The control of the injector 34 by the control device 40 will be described below with reference to Figure 4. The processing circuit 41 performs the series of processes shown in Figure 4 each time the required torque is calculated in the process described with reference to Figure 2.

[0024] First, in step S100, the processing circuit 41 determines whether the fuel pressure in the fuel tank 10 is above a predetermined value. The predetermined value is, for example, the lower limit of the pressure range that can be adjusted by the pressure reducing valve 14. In this case, the predetermined value is set to determine that the amount of fuel remaining in the fuel tank 10 has decreased and the pressure reducing valve 14 can no longer maintain the pressure downstream of the pressure reducing valve 14. The magnitude of the predetermined value is set so that it can be determined that the pressure downstream of the pressure reducing valve 14 can no longer be maintained based on the fuel pressure in the fuel tank 10 being below the predetermined value.

[0025] If the processing circuit 41 determines in step S100 that the fuel pressure in the fuel tank 10 is above a predetermined value (step S100: YES), it proceeds to step S110. In step S110, the processing circuit 41 calculates the fuel injection period of the injector 34 of the internal combustion engine 30 according to the process described with reference to Figure 2, so as to inject the amount of fuel necessary to generate a torque corresponding to the requested torque. Then, in step S120, the processing circuit 41 controls the injector 34 to realize the fuel injection period calculated through step S110. After controlling the injector 34 in this way, the processing circuit 41 terminates this series of processes.

[0026] On the other hand, if the processing circuit 41 determines in step S100 that the fuel pressure in the fuel tank 10 is lower than a predetermined value (step S100: NO), it proceeds to step S130. In step S130, the processing circuit 41 calculates the upper torque limit using the fuel pressure in the fuel tank 10 and the fuel pressure in the delivery pipe 31, according to the process described with reference to Figure 3. Then, the processing circuit 41 proceeds to step S140 and compares the requested torque with the upper torque limit calculated in step S130.

[0027] If the processing circuit 41 determines in step S140 that the requested torque is less than or equal to the upper torque limit (step S140: YES), it proceeds to step S110 and calculates the fuel injection period of the injector 34 of the internal combustion engine 30 according to the process described with reference to Figure 2, so as to inject the amount of fuel necessary to generate a torque equivalent to the requested torque. Then, in step S120, the processing circuit 41 controls the injector 34 to realize the fuel injection period calculated through step S110. After controlling the injector 34 in this way, the processing circuit 41 terminates this series of processes.

[0028] On the other hand, if the processing circuit 41 determines in step S140 that the requested torque is greater than the torque upper limit (step S140: NO), it proceeds to step S150. In step S150, the processing circuit 41 calculates the fuel injection period of the injector 34 of the internal combustion engine 30 so as to inject the amount of fuel necessary to generate a torque corresponding to the torque upper limit. At this time, the processing circuit 41 calculates the fuel injection period of the injector 34 by changing the requested torque to the torque upper limit in the process described with reference to Figure 2. Then, the processing circuit 41 proceeds to step S120 and controls the injector 34 to realize the fuel injection period calculated through step S150. After controlling the injector 34 in this way, the processing circuit 41 terminates this series of processes.

[0029] <Operation of this embodiment> The control device 40 of the internal combustion engine 30 is equipped with a processing circuit 41. The processing circuit 41 calculates a torque upper limit such that the lower the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 that detects the fuel pressure in the fuel tank 10, the smaller the torque upper limit becomes. The processing circuit 41 compares the requested torque with the torque upper limit and, if the requested torque is less than or equal to the torque upper limit (step S140: YES), sets the fuel injection period of the injector 34 of the internal combustion engine 30 to inject the amount of fuel necessary to generate the torque corresponding to the requested torque (step S110). On the other hand, if the requested torque is greater than the torque upper limit (step S110: NO), the processing circuit 41 sets the fuel injection period of the injector 34 of the internal combustion engine 30 to inject the amount of fuel necessary to generate the torque corresponding to the torque upper limit (step S150). The processing circuit 41 controls the injector 34 based on the fuel injection period set by the processing in step S110 or step S150 (step S120).

[0030] The fuel injection period set according to the upper torque limit is shorter than the fuel injection period set according to the required torque. Therefore, in situations where the fuel pressure in the fuel tank 10 is low and abnormal combustion would occur if the fuel injection period were set according to the required torque, a shorter fuel injection period than the one set according to the required torque will be set.

[0031] <Effects of this embodiment> (1) The control device 40 of the internal combustion engine 30 can prevent the fuel injection period from becoming excessively long, and thus can suppress abnormal combustion.

[0032] (2) In the control device 40 of the internal combustion engine 30, the processing circuit 41 uses the engine rotation speed in addition to the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 to calculate the torque upper limit value such that it decreases as the engine rotation speed increases.

[0033] The higher the engine rotational speed, the shorter the fuel injection period suitable for forming an ideal air-fuel mixture. The control device 40 of the internal combustion engine 30 calculates the torque limit using the engine rotational speed in addition to the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12. In this way, by taking the engine rotational speed into account for the torque limit, the control device 40 of the internal combustion engine 30 can correctly calculate the torque limit even when the engine rotational speed changes.

[0034] As a result, the control device 40 of the internal combustion engine 30 can limit the requested torque to an upper torque limit value according to the vehicle's driving conditions, thereby enabling more appropriate control of the fuel injection period of the injector 34.

[0035] (3) In the control device 40 of the internal combustion engine 30, the processing circuit 41 uses the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12, as well as the fuel pressure in the delivery pipe 31 detected by the delivery pressure sensor 32, which detects the fuel pressure in the delivery pipe 31 that supplies fuel from the fuel tank 10 to the injector 34, to calculate the upper limit of the torque such that it becomes smaller as the fuel pressure in the delivery pipe 31 decreases.

[0036] Fluctuations in the fuel pressure within the delivery pipe 31 cause changes in the amount of fuel injected from the injector 34. Because the fuel pressure within the delivery pipe 31 is taken into account when calculating the torque upper limit, the control device 40 of the internal combustion engine 30 can correctly calculate the torque upper limit even when the fuel pressure within the delivery pipe 31 changes.

[0037] As a result, the control device 40 of the internal combustion engine 30 can calculate an appropriate torque upper limit that reflects the fuel pressure in the fuel tank 10 and the fuel pressure in the delivery pipe 31, and control the fuel injection period of the injector 34.

[0038] (4) In the control device 40 of the internal combustion engine 30, the processing circuit 41 uses the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 and the fuel pressure in the delivery pipe 31 detected by the delivery pressure sensor 32, which detects the fuel pressure in the delivery pipe 31 that supplies fuel from the fuel tank 10 to the injector 34, to calculate the maximum flow rate limit, which is the maximum amount of fuel that can be injected from the injector 34 in one cycle. The processing circuit 41 uses the calculated flow rate limit and the engine rotation speed to calculate the injection amount limit, which is the maximum amount of fuel that can be injected from the injector 34 in one cycle. The processing circuit 41 uses the calculated injection amount limit and the engine rotation speed to calculate the torque limit.

[0039] When the fuel pressure in the fuel tank 10 and the fuel pressure in the delivery pipe 31 decrease, the maximum flow rate limit, which is the maximum amount of fuel that can be supplied to the injector 34, decreases. If the flow rate limit is small, the maximum injection amount limit, which is the maximum amount of fuel that can be injected from the injector 34 in one cycle, also decreases accordingly.

[0040] The control device 40 of the internal combustion engine 30 calculates the upper limit of the flow rate and the upper limit of the injection amount using the fuel pressure in the fuel tank 10, the fuel pressure in the delivery pipe 31, and the engine rotation speed. After estimating the upper limit of the injection amount according to the fuel pressure in the fuel tank 10, the control device 40 of the internal combustion engine 30 calculates the upper limit of the torque using the engine rotation speed.

[0041] As a result, the control device 40 of the internal combustion engine 30 can calculate a torque upper limit that takes into account the fuel pressure in the fuel tank 10 and the current operating state of the internal combustion engine 30. (5) In the control device 40 of the internal combustion engine 30, the processing circuit 41 does not calculate the upper limit of the torque when the fuel pressure in the fuel tank 10 is above a predetermined value, and sets the fuel injection period of the injector 34 to inject the amount of fuel necessary to generate a torque equivalent to the required torque.

[0042] If the fuel pressure in the fuel tank 10 is sufficiently high, the injector 34 can inject the required amount of fuel even with a short fuel injection period. Therefore, if the fuel pressure in the fuel tank 10 is sufficiently high, the control device 40 of the internal combustion engine 30 does not need to limit the required torque by a torque upper limit. If the fuel pressure in the fuel tank 10 is above a predetermined value, the control device 40 of the internal combustion engine 30 does not calculate a torque upper limit and sets the fuel injection period according to the required torque.

[0043] This prevents the control device 40 of the internal combustion engine 30 from limiting the required torque by the torque upper limit more than necessary. <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0044] In this embodiment, the fuel injection line of the vehicle's fuel injection system is equipped with a delivery pipe 31, but it is not necessarily required, and the pressure reducing valve 14 and the delivery pipe 31 may be omitted. In this case, the control device 40 of the internal combustion engine 30 only needs to use the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 to calculate the torque upper limit so that it decreases as the fuel pressure in the fuel tank 10 decreases. In this case, the processing circuit 41 uses the requested injection amount, the fuel pressure in the fuel tank 10, the fuel temperature, and the engine rotation speed to determine the fuel injection period corresponding to the requested injection amount.

[0045] In the control device 40 of the internal combustion engine 30 according to the embodiment, the torque upper limit is calculated using the engine's rotational speed, such that the torque upper limit decreases as the engine's rotational speed increases. However, the control device 40 of the internal combustion engine 30 described above can calculate the torque upper limit using the fuel pressure in the fuel tank 10 detected by the tank pressure sensor 12 and the fuel pressure in the delivery pipe 31 detected by the delivery pressure sensor 32, without using the engine's rotational speed. [Explanation of symbols]

[0046] 10…Fuel tank 11... Tank shut-off valve 12... Tank pressure sensor 13... Tank temperature sensor 14… Pressure Reducing Valve 20…Relief valve 21... Delivery shutoff valve 30... Internal combustion engine 31…Delivery pipe 32…Delivery pressure sensor 33…Delivery temperature sensor 34... Injector 35…Output shaft 36... Engine rotation speed sensor 40…Control device 41…Processing circuit

Claims

1. A control device for an internal combustion engine, which is mounted on a vehicle and controls an internal combustion engine that supplies fuel using fuel pressure, Equipped with a processing circuit, The processing circuit calculates a torque upper limit such that the lower the fuel pressure in the fuel tank detected by the tank pressure sensor, the lower the fuel pressure in the fuel tank, The processing circuit compares the requested torque with the torque upper limit and, if the requested torque is less than or equal to the torque upper limit, sets the fuel injection period of the injector of the internal combustion engine to inject the amount of fuel necessary to generate a torque equivalent to the requested torque, while if the requested torque is greater than the torque upper limit, sets the fuel injection period of the injector of the internal combustion engine to inject the amount of fuel necessary to generate a torque equivalent to the torque upper limit. The injector of the internal combustion engine is controlled based on the fuel injection period set by the processing circuit. Control device for internal combustion engines.

2. The aforementioned processing circuit In addition to the fuel pressure in the fuel tank detected by the tank pressure sensor, the engine rotation speed is used to calculate the torque upper limit such that it decreases as the engine rotation speed increases. A control device for an internal combustion engine according to claim 1.

3. The processing circuit described above In addition to the fuel pressure in the fuel tank detected by the tank pressure sensor, the torque upper limit is calculated using the fuel pressure in the delivery pipe detected by a delivery pressure sensor that detects the fuel pressure in the delivery pipe supplying fuel from the fuel tank to the injector, such that the lower the fuel pressure in the delivery pipe, the lower the torque upper limit becomes. The control device for an internal combustion engine according to claim 2.

4. The aforementioned processing circuit Using the fuel pressure in the fuel tank detected by the tank pressure sensor and the fuel pressure in the delivery pipe detected by the delivery pressure sensor that supplies fuel from the fuel tank to the injector, the maximum flow rate limit, which is the maximum amount of fuel flowing to the injector in one cycle, is calculated. Using the calculated flow rate upper limit and engine rotation speed, the injection amount upper limit, which is the maximum amount of fuel that can be injected from the injector in one cycle, is calculated. The torque limit is calculated using the calculated injection volume limit and engine rotation speed. The control device for an internal combustion engine according to claim 3.

5. The aforementioned processing circuit If the fuel pressure in the fuel tank is above a predetermined value, the upper limit of the torque is not calculated, and the fuel injection period of the injector is set to inject the amount of fuel necessary to generate the torque equivalent to the requested torque. A control device for an internal combustion engine according to claim 1.

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