Control device

Abstract

To provide a control device capable of suppressing occurrence of a water hammer phenomenon.SOLUTION: A control device includes: a control section that controls cranking of an internal combustion engine by using an electric motor; a calculation section that calculates a waveform of first cranking torque output from the electric motor to the internal combustion engine during the cranking; and an acquisition section that acquires a waveform of normal second cranking torque during the cranking calculated beforehand on the basis of a temperature of the internal combustion engine. When detecting that the first cranking torque is larger than the second cranking torque by comparing the waveform of the first cranking torque with the waveform of the second cranking torque, the control section stops the cranking.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device. [Background technology]

[0002] Regarding the cranking of an internal combustion engine, for example, Patent Document 1 describes how the cranking torque is appropriately set so as to expand the region in which a hybrid vehicle can run on electric power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-131142 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if heavy rain causes the combustion chamber of an internal combustion engine to become flooded, the pressure of the rainwater will increase excessively when the volume of the combustion chamber shrinks when cranking begins, which could cause the water hammer phenomenon and damage the internal combustion engine.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a control device that can suppress the occurrence of the water hammer phenomenon. [Means for solving the problem]

[0006] The control device of the present invention has a control unit that controls the cranking of an internal combustion engine by an electric motor, a calculation unit that calculates the waveform of a first cranking torque output from the electric motor to the internal combustion engine during the cranking, and an acquisition unit that acquires the waveform of a normal second cranking torque during the cranking that is calculated in advance based on the temperature of the internal combustion engine, and the control unit stops the cranking when it detects that the first cranking torque is greater than the second cranking torque by comparing the waveform of the first cranking torque with the waveform of the second cranking torque. Effect of the Invention

[0007] According to the present invention, the occurrence of the water hammer phenomenon can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a configuration diagram showing an example of a hybrid vehicle system. [Diagram 2] FIG. 2 is a diagram illustrating an example of the cranking stop process. [Diagram 3] FIG. 3 is a flowchart showing an example of an engine start process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Hybrid vehicle system configuration) 1 is a configuration diagram showing an example of a hybrid vehicle system S. The hybrid vehicle system S is mounted on a hybrid vehicle, and includes an ECU (Electronic Control Unit) 1, an engine (ENG) 2, a variable valve timing mechanism (VVT: Variable Valve Timing) 3, a damper 4, a gear mechanism 5, a differential gear 6, an electric motor MG#1, an electric motor MG#2, an ignition switch 90, and a water temperature sensor 91.

[0010] The engine 2 is an example of an internal combustion engine. The symbol G shows a schematic configuration of the engine 2. The engine 2 is a gasoline engine or a diesel engine that outputs power by burning fuel such as gasoline or diesel. The engine 2 has a crankshaft 20, a piston 21, a combustion chamber 22, an intake passage 23, an exhaust passage 24, an intake valve 25, an exhaust valve 26, an ignition plug 27, and a fuel injection valve 28. The engine 2 is also provided with a crank angle sensor 93 that detects the rotation angle of the crankshaft 20, and a combustion pressure sensor 92 that detects the pressure inside the combustion chamber 22.

[0011] The intake passage 23 introduces air into the combustion chamber 22 via an air cleaner (not shown) or the like. The exhaust passage 24 discharges exhaust gas from the combustion chamber 22 via a catalyst (not shown) or the like. When the intake valve 25 opens, the intake passage 23 and the combustion chamber 22 communicate with each other, and when the exhaust valve 26 opens, the exhaust passage 24 and the combustion chamber 22 communicate with each other. The fuel injection valve 28 injects fuel into the combustion chamber 22. A mixture of fuel and air is generated in the combustion chamber 22. The mixture is burned by ignition of the spark plug 27. The piston 21 reciprocates up and down due to the combustion of the mixture. The crankshaft 20 rotates by power transmission from the piston 21.

[0012] The operating cycle of the engine 2 is made up of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The variable valve timing mechanism 3 individually controls the opening and closing timing of the intake valve 25 and the exhaust valve 26 in accordance with the operating cycle of the engine 2. As an example, the variable valve timing mechanism 3 advances or retards the opening and closing timing of the intake valve 25 and the exhaust valve 26 by changing the phase angle of a camshaft (not shown) relative to the crankshaft 20.

[0013] The crankshaft 20 is connected to a gear mechanism 5 via a damper 4. The gear mechanism 5 includes a planetary gear and the like, and divides and transmits the power of the engine 2 to electric motors MG#1, MG#2. The rotating shaft of the electric motor MG#2 is connected to a differential gear 6. The power of the electric motor MG#2 is transmitted to a drive shaft 60 via the differential gear 6.

[0014] The electric motor MG#1 functions as a generator to supply electric power to auxiliary machinery (not shown). Moreover, when the engine 2 is started, the electric motor MG#1 functions as a motor to rotate the crankshaft 20. An ignition switch 90 is turned on when the user starts the engine 2, and is turned off when the user stops the engine 2. The on / off state of the ignition switch 90 is notified to the ECU 1. Moreover, a water temperature sensor 91 detects the temperature of the coolant for the engine 2.

[0015] The ECU 1 is an example of a control device. The ECU 1 is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 1 operates the CPU according to a program stored in the ROM. The ECU 1 controls, for example, the engine 2, the electric motor MG#1, and the variable valve timing mechanism 3.

[0016] The ECU 1 has, as software functions, a control unit (CT) 10, a calculation unit (Pf) 11, an acquisition unit (Aq) 12, and a non-volatile memory 13 such as a flash memory. Note that the control unit 10, the calculation unit 11, and the acquisition unit 12 may be hardware such as an electronic circuit. Also, instead of the memory 13, other storage devices such as a hard disk drive may be used.

[0017] The control unit 10 controls the cranking of the engine 2 by the electric motor MG#1. Specifically, when the ignition switch 90 is turned on from off, the control unit 10 rotates the electric motor MG#1 to rotate the crankshaft 20 and start the engine 2.

[0018] The calculation unit 11 calculates the waveform of the cranking torque output from the electric motor MG#1 to the engine 2 during cranking.

[0019] The calculation unit 11 calculates the friction torque of the engine 2 from, for example, the detection values ​​of the combustion pressure sensor 92 and the crank angle sensor 93, and sets a cranking torque exceeding the friction torque as a target value in the control unit 10 so that the rotation speed of the engine 2 increases according to a predetermined pattern. The cranking torque calculated by the calculation unit 11 is an example of a first cranking torque, and will be referred to as a calculated torque hereinafter. The control unit 10 controls the electric motor MG#1 so that the calculated torque is output from the electric motor MG#1 to the engine 2. The electric motor MG#1 is driven by a three-phase AC current input from an inverter (not shown). The control unit 10 controls the rotation of the electric motor MG#1 by adjusting the duty ratio of a PWM (Pulse Width Modulation) signal output to the inverter according to the calculated torque.

[0020] The acquisition unit 12 acquires from the memory 13 a waveform of a normal cranking torque during cranking, which is calculated in advance based on the temperature of the engine 2. The memory 13 stores in advance a plurality of waveform data corresponding to a plurality of temperatures of the engine 2. Here, the temperature of the engine 2 is, for example, the temperature of the coolant of the engine 2. The acquisition unit 12 selects and acquires waveform data corresponding to a detection value of the water temperature sensor 91. Each waveform data in the memory 13 is an example of a waveform of the second cranking torque.

[0021] Each waveform data indicates, for example, a normal cranking torque in the combustion chamber 22 as a change with respect to the crank angle for each temperature of the engine 2. Each waveform data is generated from the results of a simulation or an experiment using an actual machine and is stored in advance in the memory 13. The acquisition unit 12 acquires a detection value from the water temperature sensor 91, and acquires waveform data corresponding to the temperature, taking the temperature of the cooling water as the temperature of the engine 2. Note that this waveform data may be acquired from another storage device via a communication network such as the Internet, instead of the memory 13. The cranking torque acquired by the acquisition unit 12 will hereinafter be referred to as a reference torque.

[0022] When there is excessive rainfall due to heavy rain, etc., rainwater may flood the combustion chamber 22 of the engine 2. When cranking begins and the piston 21 approaches top dead center and the volume of the combustion chamber 22 decreases, the pressure of the rainwater increases excessively, which may cause a water hammer phenomenon and damage the engine 2.

[0023] Therefore, the control unit 10 compares the waveform of the calculated torque calculated by the calculation unit 11 with the reference torque waveform acquired by the acquisition unit 12, and stops cranking when it detects that the calculated torque is greater than the reference torque. If the combustion chamber 22 is filled with rainwater, there is a risk that the calculated torque will increase excessively due to the pressure of the rainwater when the piston 21 approaches the top dead center after cranking starts. However, the control unit 10 stops cranking when the calculated torque exceeds the reference torque, so that the piston 21 also stops, and damage to the engine 2 can be suppressed. The cranking stop process will be described below.

[0024] (Cranking stop processing) Fig. 2 is a diagram showing an example of the cranking stop process. Fig. 2 shows the correlation between the waveforms of the calculated torque and the reference torque, the operation cycle of the engine 2, and the position of the piston 21 on the operation cycle. The piston 21 changes its position on the operation cycle by moving up and down with the rotation of the crankshaft 20. On the paper surface of Fig. 2, the rightward direction is the direction in which the crankshaft 20 rotates during cranking (cranking direction).

[0025] The operating cycle of the engine 2 repeats an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in this order along the cranking direction, for example, every two revolutions of the crankshaft 20. The piston 21 is located at intake bottom dead center at the boundary between the intake stroke and the compression stroke, at compression top dead center at the boundary between the compression stroke and the expansion stroke, at expansion bottom dead center at the boundary between the expansion stroke and the exhaust stroke, and at exhaust top dead center at the boundary between the exhaust stroke and the intake stroke. An initial position P1 of the piston 21 before cranking is, for example, intake bottom dead center, and during cranking, the piston 21 moves from position P1 in the cranking direction.

[0026] The waveforms of the calculated torque and the reference torque show the change in cranking torque (N m) relative to the cranking angle (degrees), and are represented by a solid line and a dotted line, respectively. The crank angle is detected by a crank angle sensor 93. As an example, crank angles of 0 degrees and 720 degrees correspond to intake bottom dead center, a crank angle of 180 degrees corresponds to compression top dead center, a crank angle of 360 degrees corresponds to expansion bottom dead center, and a crank angle of 540 degrees corresponds to exhaust top dead center.

[0027] The cranking torque indicates a maximum value when the crank angle is 180 degrees or 540 degrees, and indicates a minimum value when the crank angle is 0 degrees, 720 degrees, or 360 degrees. In other words, the smaller the volume of the combustion chamber 22, the larger the cranking torque, and the larger the volume of the combustion chamber 22, the smaller the cranking torque.

[0028] The waveform of the reference torque is calculated as the upper limit of a normal cranking torque when, for example, rainwater (liquid water) is not filled in the combustion chamber 22. During cranking, the control unit 10 controls the electric motor MG#1 so that the piston 21 moves from the initial position P1 toward the compression top dead center.

[0029] The control unit 10 compares the waveforms of the calculated torque and the reference torque in, for example, a crank angle range D where the increase rate of cranking is significantly large. Here, the crank angle range D corresponds to a region of a predetermined width of the crank angle on the compression top dead center side in the compression stroke of the operating cycle of the engine 2. In this way, if the waveform comparison process is limited to the range D, the processing load is reduced, but the comparison process may be performed regardless of the crank angle.

[0030] For example, when the piston 21 reaches a position P2 near the top dead center of the compression stroke, the control unit 10 detects that the calculated torque is greater than the reference torque by the above comparison process. At this time, the pressure of the rainwater in the combustion chamber 22 causes the calculated torque to be greater than the reference torque by a difference ΔTf.

[0031] The control unit 10 stops cranking when the calculated torque>reference torque is established. This stops the rotation of the electric motor MG#1, and therefore the operation of the crankshaft 20 and the piston 21 is also stopped, suppressing the occurrence of the water hammer phenomenon. Therefore, it is possible to prevent damage to the engine 2 before it occurs.

[0032] (Engine start process) 3 is a flowchart showing an example of a start process for the engine 2. This process is executed repeatedly at regular time intervals, for example.

[0033] First, the control unit 10 determines whether the ignition switch (IG-SW) 90 is on or not (step St1). If the IG-SW 90 is off (No in step St1), this process ends. If the IG-SW 90 is on (Yes in step St1), the control unit 10 determines whether the engine 2 has not yet started (step St2). If the engine 2 has already started (No in step St2), this process ends.

[0034] If the engine 2 has not been started (Yes in step St2), the acquisition unit 12 acquires the coolant temperature from the water temperature sensor 91 as the temperature of the engine 2 (step St3). The acquisition unit 12 may acquire the oil temperature of the engine 2 instead of the coolant temperature. Next, the acquisition unit 12 acquires reference torque waveform data corresponding to the temperature of the engine 2 from the memory 13 (step St4). Next, the control unit 10 starts cranking (step St5).

[0035] Next, the calculation unit 11 acquires the detection values ​​of the combustion pressure sensor 92 and the crank angle sensor 93 (step St6). Next, the calculation unit 11 calculates the cranking torque from each detection value and the like (step St7). As a result, a calculated torque waveform is calculated. Note that the cranking torque may be calculated using the angular velocity of the crankshaft 20 or the torque of the electric motor MG#1.

[0036] Next, the control unit 10 compares the calculated torque with the reference torque (step St8). If the calculated torque>the reference torque holds (Yes in step St8), the control unit 10 stops cranking (step St9). After that, this process ends.

[0037] On the other hand, if the calculated torque≦reference torque is established (No in step St8), the control unit 10 controls the electric motor MG#1 with the calculated torque as a target value (step St10), whereby the crankshaft 20 rotates and cranking is performed.

[0038] Next, the control unit 10 determines whether or not cranking has ended (step St11). At this time, the control unit 10 determines that cranking has ended, for example, when the rotation speed of the crankshaft 20 calculated from the detection value of the crank angle sensor 93 is equal to or lower than a predetermined value.

[0039] If cranking has ended (Yes in step St11), this process ends. If cranking has not ended (No in step St11), each process from step St6 onwards is executed again. In this manner, the ECU 1 executes the start process of the engine 2. If the engine 2 has multiple cylinders, the calculated torque is compared with the reference torque for each cylinder. Also, although a hybrid vehicle has been given in this example, the present invention is not limited to this, and the above-mentioned cranking stop process can also be applied to engine vehicles.

[0040] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this embodiment and can be modified in various ways without departing from the scope of the present invention. [Explanation of symbols]

[0041] 1 ECU (control device), 2 engine (internal combustion engine), 10 control unit, 11 calculation unit, 12 acquisition unit, 20 crankshaft, 21 piston, 22 combustion chamber, 91 water temperature sensor, 92 combustion pressure sensor, 93 crank angle sensor, MG#1,#2 electric motor

Claims

[Claim 1] A control unit that controls cranking of the internal combustion engine by the electric motor; A calculation unit that calculates a waveform of a first cranking torque output from the electric motor to the internal combustion engine during the cranking; an acquisition unit that acquires a waveform of a normal second cranking torque during the cranking, the waveform being calculated in advance based on a temperature of the internal combustion engine, The control unit stops the cranking when detecting that the first cranking torque is greater than the second cranking torque by comparing a waveform of the first cranking torque with a waveform of the second cranking torque. Control device.

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