Cranking device control device

Abstract

To provide a control device for a cranking device that suppresses deterioration of startability of an engine while suppressing electric power consumption through cranking.SOLUTION: A control device for a cranking device is for cranking of a crank shaft of an engine at start of the engine. The control device for the cranking device includes: a first torque control section that performs control so that for a waste time from driving start of the cranking device to start of rotation of the crank shaft, torque of the cranking device lowers as a time from the driving start of the cranking device elapses; and a second torque control section that performs control so that after the waste time passes, the torque lowers as rotational frequency of the cranking device increases.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] A cranking device that cranks the crankshaft of an engine is known. In such a cranking device, the torque is controlled to decrease as the rotation speed of the cranking device increases. This allows the engine to start while suppressing power consumption due to cranking (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-188800 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a dead time between when the cranking device starts to operate and when the crankshaft actually starts to rotate. During this dead time, the rotation speed of the cranking device may rise sharply, which may cause a sudden drop in torque. This temporary drop in torque immediately after the cranking device starts to operate may reduce the startability of the engine.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a control device for a cranking device that suppresses deterioration in engine startability while suppressing power consumption due to cranking. [Means for solving the problem]

[0006] The above object can be achieved by a control device for a cranking device that cranks the crankshaft of the engine when the engine is started, the control device for the cranking device comprising: a first torque control unit that controls the torque of the cranking device to decrease as the time elapses from the start of operation of the cranking device until the crankshaft starts rotating during the dead time from the start of operation of the cranking device until the crankshaft starts rotating; and a second torque control unit that controls the torque to decrease as the rotation speed of the cranking device increases after the dead time has elapsed.

[0007] The motor may further include a switching unit that switches control of the torque from the first torque control unit to the second torque control unit when the rotation speed exceeds an upper limit during the dead time. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a control device for a cranking device that suppresses deterioration in engine startability while suppressing power consumption due to cranking. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of the engine system. [Figure 2] FIG. 2 is a flowchart illustrating the cranking control. [Figure 3] FIG. 3A is a view showing an example of a map that defines the torque of the starter in the first torque control, and FIG. 3B is a view showing an example of a map that defines the torque of the starter in the second torque control. [Figure 4] FIG. 4 is a timing chart illustrating the cranking control. [Figure 5] FIG. 5 is a timing chart illustrating the cranking control. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Engine system overview] FIG. 1 is a schematic diagram of an engine system 1. The engine system 1 is mounted on, for example, a vehicle, but may also be mounted on a vessel other than a vehicle. The engine system 1 includes an engine 10, a starter 20, an endless belt 30, a battery 40, and an ECU (Electronic Control Unit) 50. The engine 10 is, for example, a gasoline engine, but may also be a diesel engine or a hydrogen engine. The starter 20 is a motor that cranks the engine 10 and is an example of a cranking device. A crankshaft 11 of the engine 10 and an output shaft 21 of the starter 20 are connected by an endless belt 30. Rotational power of the output shaft 21 of the starter 20 is transmitted to the crankshaft 11 via the endless belt 30. This allows the starter 20 to rotate the crankshaft 11. Instead of the endless belt 30, for example, multiple gears may be used. The starter 20 includes a rotation speed sensor 22 that detects the rotation speed of the output shaft 21. A battery 40 supplies power to the starter 20.

[0011] The ECU 50 is an electronic control unit that performs control processing related to the engine 10 and the starter 20. The ECU 50 is mainly composed of a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The ECU 50 is an example of a control device for a cranking device, and functionally realizes a first torque control unit, a second torque control unit, and a switching unit, which will be described in detail later. The ECU 50 controls the torque of the starter 20 based on the detection result of the rotation speed sensor 22.

[0012] [Cranking control] FIG. 2 is a flowchart illustrating cranking control. The ECU 50 determines whether or not there is an engine start request (step S1). If the answer is No in step S1, this control ends. If the answer is Yes in step S1, the ECU 50 starts driving the starter 20 to start cranking the engine 10 (step S2). Next, the ECU 50 determines whether or not the dead time from when the starter 20 starts driving to when the crankshaft 11 starts rotating is in progress (step S3). The dead time is a response delay time from when the output shaft 21 of the starter 20 starts rotating to when the crankshaft 11 starts rotating, due to the flexing of the endless belt 30. The dead time is stored in advance in the ROM of the ECU 50 based on experimental results. Note that even when multiple gears are used instead of the endless belt 30, such dead time exists due to backlash.

[0013] If the answer is Yes in step S3, the ECU 50 determines whether the rotation speed of the starter 20 is equal to or lower than an upper limit value (step S4). The upper limit value is set to a rotation speed of the starter 20 at which the power consumption of the starter 20 increases excessively during execution of a first torque control, which will be described later. If the answer is Yes in step S4, the ECU 50 executes a first torque control, which controls the torque of the starter 20 based on the elapsed time since the start of driving of the starter 20 (step S5).

[0014] 3A is an example of a map that defines the torque of starter 20 under first torque control. As shown in FIG. 3A, the torque is defined to decrease as the elapsed time increases. Step S5 is an example of processing executed by the first torque control. In the example of FIG. 3A, the torque decreases linearly as the elapsed time increases, but it may decrease in a curved manner.

[0015] If the answer is No in step S3, the ECU 50 executes second torque control, which controls the torque of the starter 20 based on the rotation speed of the starter 20 (step S6). FIG. 3B is an example of a map that defines the torque of the starter 20 in the second torque control. As shown in FIG. 3B, the torque of the starter 20 is controlled so that it decreases as the rotation speed of the starter 20 increases. In detail, the torque is defined so that the value obtained by multiplying the rotation speed and torque of the starter 20 is substantially constant. This reduces the power consumption of the starter 20. Step S6 is an example of processing that is executed by the second torque control. Furthermore, if the answer is No in step S4, the ECU 50 executes the second torque control (step S6). Step S4 is an example of processing that is executed by a switching unit.

[0016] Next, the ECU 50 determines whether the engine 10 has reached a complete combustion state (step S7). For example, if the engine 10 speed reaches or exceeds a predetermined complete combustion determination speed, the engine 10 is deemed to have reached a complete combustion state. If the answer is No in step S7, the processing from step S3 onward is executed again. If the answer is Yes in step S7, this control ends.

[0017] 4 and 5 are timing charts illustrating cranking control. These figures show the transitions of torque and rotation speed of the starter 20. First, FIG. 4 will be described. When the starter 20 starts to be driven (time t0), the first torque control is executed until the dead time has elapsed since the start of driving of the starter 20. When the dead time has elapsed since the start of driving of the starter 20 (time t1), the first torque control is switched to the second torque control.

[0018] In Figure 4, the dotted line indicates the torque when the second torque control is executed even during the dead time. As described above, the rotation speed of the starter 20 rises sharply during the dead time, and therefore the torque of the starter 20 drops sharply when the second torque control is executed. This may result in a deterioration in the startability of the engine 10. In this embodiment, the first torque control is executed during the dead time, and therefore the deterioration in the startability of the engine 10 can be suppressed. Note that, as described above, the first torque control is stipulated so that the torque of the starter 20 decreases as the elapsed time from the start of driving of the starter 20 increases. This is to suppress an excessive increase in power consumption of the starter 20 while the first torque control is being executed.

[0019] Next, Fig. 5 will be described. When the drive of the starter 20 starts (time t0), the first torque control is executed. When the rotation speed of the starter 20 becomes equal to or greater than the upper limit value while the first torque control is being executed (time t1), the control is switched from the first torque control to the second torque control. This significantly reduces the torque of the starter 20. When the rotation speed of the starter 20 becomes equal to or less than the upper limit value again during the dead time, the control is switched from the second torque control to the first torque control (time t2). After the dead time has elapsed, the control is switched from the first torque control to the second torque control (time t3). By switching to the second torque control when the rotation speed of the starter 20 becomes equal to or greater than the upper limit value during the dead time in this way, an increase in power consumption of the starter 20 can be suppressed.

[0020] In the above embodiment, the starter 20 has been described as an example of a cranking device, but the invention is not limited to this. The cranking device may be, for example, a motor that functions as a driving power source together with the engine 10 by assisting the power of the engine 10. In other words, the cranking device may be a motor that is mounted on a hybrid vehicle and functions as a driving power source.

[0021] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0022] 10 Engine 20 Starter (cranking device) 50 ECU (first torque control unit, second torque control unit, switching unit)

Claims

1. A control device for a cranking device that cranks a crankshaft of an engine when the engine is started, a first torque control unit that controls the torque of the cranking device so that the torque decreases as the elapsed time from the start of driving of the cranking device to the start of rotation of the crankshaft increases during a dead time from the start of driving of the cranking device; a second torque control unit that controls the torque to decrease as the rotation speed of the cranking device increases after the dead time has elapsed.

2. 2. The cranking device control device according to claim 1, further comprising a switching unit that switches control of the torque from the first torque control unit to the second torque control unit when the rotation speed exceeds an upper limit during the dead time.

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