Idle stop control device

Abstract

Provided is an idle stop control device that can suppress body vibration at the time of automatic engine restart (at the time of recovery) from an idle stop state. An ECU (20) that constitutes the idle stop control device (1) is provided with an auxiliary machine control section (21) that controls the power generation amount of an alternator (25) that is driven by an engine (10). The auxiliary machine control section (21) sets a target engine speed in such a manner that the time differential value of the engine speed becomes constant at the time of engine restart, and increases the power generation amount of the alternator (25) in such a manner that the time differential value of the engine speed becomes constant in the case where the actual engine speed is higher than the target engine speed.

Description

Technical Field

[0001] This invention relates to an idle stop control device. Background Technology

[0002] In recent years, from the perspective of improving vehicle fuel efficiency and / or reducing emissions, vehicles with idle stop functions (idle stop systems) that automatically stop the engine when waiting at traffic lights (when stopped) have been widely used. In an idle stop system, when the engine is in an idle stop state, for example, if the release of the brake pedal is detected, a request to restart the engine is output, causing the engine to restart (see, for example, Patent Document 1).

[0003] However, in the past, there have been instances where the vehicle body vibrates when the engine automatically restarts from an idle stop (during recovery), causing discomfort to the vehicle occupants. Therefore, it is desirable to suppress (reduce) the vehicle body vibration during the automatic restart of the engine from an idle stop.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-329039 Summary of the Invention

[0007] Technical issues

[0008] The purpose of this invention is to provide an idle stop control device that can suppress vehicle body vibration when the engine automatically restarts (resumes operation) from an idle stop state.

[0009] Technical solution

[0010] Therefore, an idle stop control device according to one embodiment of the present invention is characterized by comprising: an idle stop control mechanism that automatically stops the engine and puts it in an idle stop state when a predetermined idle stop condition is met, and automatically restarts the engine when a predetermined restart condition is met; and an auxiliary machine control mechanism that controls the driving state of an auxiliary machine driven by the engine, wherein when the engine is automatically restarted from the idle stop state by the idle stop control mechanism, the auxiliary machine control mechanism controls the driving state of the auxiliary machine driven by the engine in a manner that keeps the time derivative of the engine speed constant.

[0011] Technical effect

[0012] According to the present invention, engine vibration can be suppressed when the engine automatically restarts (resumes) from an idle stop state, and vehicle body vibration can be suppressed. Attached Figure Description

[0013] Figure 1 This is a block diagram illustrating the configuration of the idle stop control device according to an embodiment.

[0014] Figure 2 This is a flowchart illustrating the processing sequence of the engine restart process (vibration suppression control) of the idle stop control device according to an embodiment.

[0015] Figure 3 This is a graph showing the relationship between the target engine speed (under vibration suppression control) when the engine restarts and the previous actual engine speed (under non-control).

[0016] Symbol Explanation

[0017] 1: Idle stop control device

[0018] 10: Engine

[0019] 17: Crankshaft Angle Sensor

[0020] 20: Engine Control Unit (ECU)

[0021] 21: Auxiliary Machine Control Department

[0022] 22: Throttle opening sensor

[0023] 23: Water temperature sensor

[0024] 25: Alternating current generator (generator / auxiliary machine)

[0025] 26: Start the motor (starter)

[0026] 30: Vehicle Dynamics Control Unit (VDCU)

[0027] 31: Brake hydraulic sensor

[0028] 40: Idle Speed ​​Stop Control Unit (ISCU)

[0029] 41: Idle Speed ​​Stop Control Unit

[0030] 50: CAN Detailed Implementation

[0031] The inventors, through repeated and in-depth research, have arrived at the following insights: When the engine automatically restarts from an idle stop, if the differential value of the engine speed changes, the forces acting along the lateral (y-direction) and vertical (z-direction) directions of the engine (horizontally opposed engine) change, thereby causing the engine block to vibrate. This engine block vibration, especially in the engine speed range that becomes an inherent resonance point of the vehicle body, causes the vehicle body to sway.

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same or equivalent parts in the drawings are represented by the same symbols. Furthermore, in each drawing, the same elements are labeled with the same symbols, and repeated descriptions are omitted.

[0033] First, use Figure 1 The configuration of the idle stop control device 1 in the embodiment will be described. Figure 1 This is a block diagram showing the configuration of the idle stop control device 1.

[0034] The idle stop control device 1 is responsible for the idle stop function, which, for example, automatically stops the engine 10 when the vehicle is temporarily stopped due to waiting for a signal, and automatically restarts the engine 10 upon starting, detecting the release of the driver's brake pedal. In particular, the idle stop control device 1 has the function of suppressing vehicle body vibration during the automatic restart of the engine from the idle stop state (during recovery). Details of this function will be described later.

[0035] Engine 10 is, for example, a horizontally opposed four-cylinder gasoline engine. Furthermore, engine 10 is a cylinder injection engine that directly injects fuel into the cylinders. In engine 10, air drawn in from the air filter is throttled by a throttle valve located in the intake manifold and drawn into each cylinder formed in engine 10 through the intake manifold 11.

[0036] Each cylinder of the engine 10 is equipped with an injector 12 for injecting fuel into the cylinder. The injector 12 directly injects fuel pressurized by the high-pressure fuel pump into the combustion chamber of each cylinder.

[0037] Additionally, spark plugs 13 for igniting the air-fuel mixture and ignition coils 14 for applying high voltage to the spark plugs 13 are installed in the cylinder heads of each cylinder of the engine 10. In each cylinder of the engine 10, the air-fuel mixture drawn in and fuel injected by the injectors 12 is ignited by the spark plugs 13 and combusted. The exhaust gases after combustion are discharged through the exhaust pipe 15.

[0038] A belt (not shown) for transmitting driving force is attached to a pulley at one end of the crankshaft 10a of the engine 10. An alternator 25 (equivalent to the generator described in the claims) is connected via this belt in a drivable manner. The driving force output from the engine 10 is transmitted to the alternator 25 via the belt, and the alternator 25 is driven.

[0039] Alternator 25 is driven by engine 10 to generate electricity. The amount of electricity generated by alternator 25 is controlled (regulated) by engine control unit (hereinafter referred to as "ECU") 20, as described later, based on, for example, the operating state of electric components (electrical load). In addition, when the engine is restarted from an idle stop state, alternator 25 controls the amount of electricity generated in a manner that keeps the time derivative of engine speed constant (or approximately constant).

[0040] A cam angle sensor 16 for determining the cylinder position of the engine 10 is installed near the camshaft of the engine 10. Additionally, a crankshaft angle sensor 17 for detecting the rotational position of the crankshaft 10a is installed near the crankshaft 10a of the engine 10. Here, a timing rotor 17a with, for example, two missing teeth and 34 teeth protrusions spaced at 10° intervals is installed at the end of the crankshaft 10a. The crankshaft angle sensor 17 detects the rotational position of the crankshaft 10a by detecting the presence or absence of these protrusions on the timing rotor 17a.

[0041] These sensors are connected to the ECU 20. Additionally, the ECU 20 is also connected to a throttle opening sensor 22 that detects the amount of throttle pedal pressure (opening) and / or a coolant temperature sensor 23 that detects the coolant temperature (water temperature). The ECU 20 is configured to include a microprocessor for performing calculations, an EEPROM storing programs for executing various processes by the microprocessor, RAM storing various data such as calculation results, backup RAM that stores the stored content via a battery, and input / output circuitry (I / F). Furthermore, the ECU 20 includes an injector driver for driving the injector 12 and an output circuit for outputting ignition signals. The ECU 20 also includes circuitry that allows for variable power generation from the alternator 25.

[0042] In ECU 20, the cylinder is determined based on the output of camshaft angle sensor 16, and the engine speed (engine RPM) is calculated based on the output of crankshaft angle sensor 17. Furthermore, ECU 20 acquires various information such as intake air volume, intake manifold pressure, throttle pedal opening, air-fuel ratio, and engine coolant and / or oil temperature based on detection signals input from various sensors. Based on this acquired information, ECU 20 comprehensively controls engine 10 by controlling fuel injection quantity and / or ignition timing, as well as various other devices.

[0043] The ECU 20 is connected to the Vehicle Dynamics Control Unit (VDCU) 30 and the Idle Stop Control Unit (ISCU) 40 via an in-vehicle communication line 50, such as CAN (Controller Area Network), in a manner that enables mutual communication. The ECU 20 transmits information such as the engine speed (engine RPM) it acquires to the ISCU 40 via CAN 50.

[0044] The VDCU30 is connected to a brake hydraulic pressure sensor 31 that detects the master cylinder pressure (brake hydraulic pressure) of the brake actuator 33, and an acceleration sensor 32 that detects acceleration in all directions. The brake hydraulic pressure sensor 31 detects the brake hydraulic pressure, which serves as an indicator of the magnitude (braking intensity) of the braking force applied to the vehicle based on the driver's braking operation. The VDCU30 brakes the vehicle by actuating the brake actuator 33 according to the amount of brake pedal operation, and detects vehicle behavior through various sensors (such as wheel speed sensors, steering angle sensors, acceleration sensors, yaw rate sensors, etc.). It suppresses sideslip and ensures vehicle stability during cornering through automatic pressure-adjusting brake control and engine torque control of the engine 10. The VDCU30 transmits the detected master cylinder pressure (brake hydraulic pressure) and other braking information to the ISCU40 via the CAN 50.

[0045] To improve fuel efficiency and reduce emissions, ISCU40 automatically stops the engine 10 by outputting an engine stop request signal to ECU20 via CAN50 when predetermined idle stop conditions are met. Subsequently, when predetermined idle stop release conditions are met, ISCU40 restarts the engine 10 by outputting an engine restart request signal to ECU20 via CAN50. It should be noted that instead of ISCU40, a configuration that gives the TCU (Transmission Control Unit) idle stop functionality can also be used.

[0046] More specifically, when conditions such as the brake pedal being depressed (i.e., the brake hydraulic pressure is greater than the restart-allowed brake hydraulic pressure (restart-allowed threshold)), the vehicle speed being zero, and / or the gear being in D (drive) or N (neutral) are met, ISCU40 sends an engine stop request signal to ECU20 via CAN50 to stop fuel injection and ignition of engine 10, thereby stopping engine 10 and performing idle stop. On the other hand, when conditions such as the brake pedal being released (i.e., the brake hydraulic pressure becomes below the restart-allowed brake hydraulic pressure), and / or the gear being in P (park) or R (reverse) are met, ISCU40 sends an engine restart request signal to ECU20 via CAN50 to restart engine 10.

[0047] Therefore, the ISCU40 functionally includes an idle stop control unit 41. The ISCU40 is configured to include: a microprocessor for performing calculations, an EEPROM storing programs for executing various processes by the microprocessor, RAM storing various data such as calculation results, a backup RAM that maintains the stored content via a battery, and input / output (I / F) circuits. In the ISCU40, the idle stop control unit 41 is implemented by the microprocessor executing the program stored in the EEPROM.

[0048] During the idle stop process, when the brake pedal is released and the brake hydraulic pressure is below the restart-allowed brake hydraulic pressure, the idle stop control unit 41 outputs an engine restart request signal to the ECU 20, requesting the engine 10 to restart.

[0049] When the ECU 20 receives an engine restart request signal from the ISCU 40, it restarts the engine 10. Specifically, the ECU 20 starts the engine 10 by activating, for example, the starter motor 26 (equivalent to the starter described in technical solutions 3 and 4). Then, it drives the injector 12 to inject fuel at a predetermined fuel injection timing, and subsequently ignites the fuel-air mixture at a predetermined ignition timing, thus restarting the engine. In other words, the idle stop control unit 41 and the ECU 20 function as the idle stop control mechanism described in technical solution 1.

[0050] In particular, ECU20 has the function of suppressing vehicle body vibration when the engine automatically restarts from an idle stop.

[0051] Therefore, the ECU20 functionally includes an auxiliary control unit 21. Within the ECU20, the auxiliary control unit 21 is implemented by having a microprocessor execute a program stored in an EEPROM or similar memory.

[0052] The auxiliary control unit 21 controls the driving state (power generation) of the alternator 25 (auxiliary machine) driven by the engine 10. That is, the auxiliary control unit 21 functions as an auxiliary control mechanism as described in any of technical solutions 1 to 5. In particular, when the engine 10 automatically restarts from the idle stop state, the auxiliary control unit 21 controls the driving state (power generation) of the alternator 25 driven by the engine 10 in a manner that keeps the time derivative of the engine speed constant (i.e., suppresses the variation of forces acting in the lateral (y-direction) and vertical (z-direction) directions of the engine 10, respectively).

[0053] It should be noted that the force acting in the y direction is represented by the following equation (1).

[0054] The force acting along the y-direction is ∝ m × r z ×(dω e / dt)···(1)

[0055] In addition, the force acting along the z direction is represented by the following equation (2).

[0056] The force acting along the z-direction is ∝ m × r y ×(dω e / dt)···(2)

[0057] It should be noted that m is the mass [kg] of crankshaft 10a, and r y The crankshaft rotation radius [m] in the y-axis direction is r. z The crankshaft rotation radius [m] is in the z-axis direction, ω e It refers to the engine speed [rpm].

[0058] More specifically, such as Figure 3 As shown, when the engine 10 restarts (in the region where the engine speed is increasing), the auxiliary engine control unit 21 sets the target engine speed (ω) in a manner that keeps the time derivative of the engine speed constant. e (Target). Furthermore, when the actual engine speed (actual engine speed) is higher than the target engine speed, the auxiliary engine control unit 21 increases the power generation (i.e., load) of the alternator 25 by keeping the time derivative of the engine speed constant. It should be noted that if the time derivative of the engine speed is constant, its magnitude (the magnitude of the slope) is not a problem. In addition, the target engine speed is preset to associate, for example, 0 rpm (during idle stop) with the idle speed after complete combustion (e.g., 600 rpm).

[0059] At this time, the auxiliary machine control unit 21 calculates the target power generation of the alternator 25 based on the product of the torque of the engine 10, the torque of the starter motor 26 that starts the engine 10, the frictional force (resistance) acting on the engine 10, the inertia of the crankshaft 10a of the engine 10 and the time derivative of the target engine speed.

[0060] Here, when the engine is restarted, the equation of motion of the rotating system on the engine crankshaft 10a is given by equation (3).

[0061] I×(dω e / dt)=T engine +T starter -T friction +T alternater ···(3)

[0062] I represents the crankshaft inertia of the engine [kg*m^2]

[0063] T engine Engine torque [Nm]

[0064] T starter Starter torque [Nm]

[0065] T friction Frictional torque [Nm]

[0066] T alternater Torque generated by an AC generator [Nm]

[0067] Therefore, in the region where the actual engine speed exceeds the target engine speed, by making the differential value of the engine speed (dω) e / dt) becomes a constant so that the alternator 25 generates electricity (producing T) alternater (<0[Nm])), thereby reducing the overshoot (i.e. force change) of engine speed.

[0068] More specifically, the auxiliary control unit 21 calculates the generating torque T indicated to the alternator 25 based on the following formula (4). alternater Indication (target power generation torque = target power generation).

[0069] T alternater Indicator = min{-T engine -T starter +T friction +I×(dω e Target / dt), 0[Nm]}···(4)

[0070] That is, the auxiliary machine control unit 21 will (-T engine -T starter +T friction +I×(dω e Let the smaller of the target / dt) and 0 be T. alternater Instructions (target generating torque = target generating output). Furthermore, the auxiliary control unit 21 instructs the alternator 25 to output the target torque (target generating torque = target generating output). alternater The indicator corresponds to the excitation current (= target power generation).

[0071] At this time, the auxiliary control unit 21 calculates T based on, for example, the intake air volume (g / s) of the engine 10, or the throttle valve opening and engine speed. engine (Torque of engine 10).

[0072] In addition, the auxiliary control unit 21 calculates T based on, for example, engine speed. starter (Torque of starter motor 26). For example, the EEPROM of ECU 20 stores information such as the engine speed and torque. starterThe mapping between the torque of starter motor 26 and other torques (starter torque mapping) is used to obtain T by retrieving this starter torque mapping based on engine speed. starter (Torque of starter motor 26). It should be noted that in the starter torque mapping, above a predetermined engine speed (the region after initial detonation), the mapping value (torque of starter motor 26) is set to 0 [Nm].

[0073] Similarly, the auxiliary control unit 21 calculates T based on, for example, engine speed and water or oil temperature. friction (The frictional force acting on engine 10). For example, the EEPROM of ECU 20 stores information such as engine speed, water temperature or oil temperature, and T. friction The mapping of the relationship between (friction forces acting on engine 10) (friction force mapping) is used to obtain T by retrieving this friction force mapping based on engine speed and water temperature or oil temperature. friction (The frictional force acting on engine 10). It should be noted that T friction The frictional force acting on engine 10 can also be calculated based solely on engine speed. Additionally, examples of frictional forces acting on engine 10 include the frictional forces (resistance) of the transmission and / or compressor.

[0074] As a result, engine speed overshoot is suppressed, and engine vibration is suppressed (reduced). However, since the alternator 25 cannot generate drive-side torque (torque greater than 0), it is impossible to control the actual engine speed to increase in the region where the actual engine speed is lower than the target engine speed.

[0075] Furthermore, when the engine speed reaches a predetermined speed (e.g., 600 rpm) or higher (i.e., when it is determined that the engine 10 is completely detonated), the auxiliary control unit 21 terminates the control (vibration suppression control) that controls the drive state (power generation) of the alternator 25 in a manner that keeps the time derivative of the engine speed constant.

[0076] Next, refer to Figure 2 At the same time, the operation of the idle speed stop control device 1 will be explained. Figure 2 This is a flowchart illustrating the processing sequence of the engine restart process (vibration suppression control) of the idle stop control device 1. This process is mainly executed repeatedly in the ECU 20 at predetermined intervals.

[0077] In step S100, during the idling stop process (engine automatic stop process), it is determined whether an engine restart request for restarting the engine 10 has been received (i.e., whether the restart conditions from the idling stop state are met). If no engine restart request for restarting the engine 10 is received, the process temporarily exits this step and continues in the idling stop state. On the other hand, if an engine restart request for restarting the engine 10 is received, the process proceeds to step S102.

[0078] In step S102, the restart of engine 10 is initiated. That is, the starter motor 26 is started to initiate the start of engine 10. Then, fuel is injected by driving injector 12 at a predetermined fuel injection timing, and thereafter, the fuel-air mixture is ignited at a predetermined ignition timing, thereby initiating the restart of engine 10.

[0079] Next, in step S104, the target engine speed is set in a manner that makes the time derivative of the engine speed constant. It should be noted that the method for setting the target engine speed is as described above, therefore a detailed explanation is omitted here.

[0080] Next, in step S106, it is determined whether the actual engine speed (actual engine speed) is higher than the target engine speed. If the actual engine speed is lower than the target engine speed, the process proceeds to step S110. Conversely, if the actual engine speed is higher than the target engine speed, the process proceeds to step S108.

[0081] In step S108, the target power generation of the alternator 25 is determined, and the drive state of the alternator 25 is controlled in a manner that makes the power generation of the alternator 25 consistent with the target power generation. That is, the drive state (power generation) of the alternator 25 is controlled in a manner that makes the time derivative of the engine speed constant. It should be noted that the method for determining the target power generation of the alternator 25 is as described above, so a detailed explanation is omitted here.

[0082] In step S110, it is determined whether the engine speed is above a predetermined speed (e.g., 600 rpm). If the engine speed is below the predetermined speed, the process proceeds to step S104, and steps S104 to S110 are repeatedly executed until the engine speed reaches or exceeds the predetermined speed. Conversely, when the engine speed reaches or exceeds the predetermined speed (i.e., when it is determined that the engine has completely detonated), this process ends and exits.

[0083] As explained above, according to this embodiment, when the engine 10 automatically restarts from an idle stop state, a target engine speed is set in a manner that keeps the time derivative of the engine speed constant. Furthermore, if the actual engine speed is higher than the target engine speed, the power output of the alternator 25 driven by the engine 10 is increased in a manner that keeps the time derivative of the engine speed constant. In other words, the time derivative of the engine speed can be adjusted to keep it constant by increasing the power output of the alternator 25 (increasing the load). As a result, engine vibration during automatic restart from an idle stop state can be suppressed, and vehicle body vibration can be suppressed.

[0084] According to this embodiment, since the target power generation of the alternator 25 is calculated based on the product of the torque of the engine 10, the torque of the starter motor 26 that starts the engine 10, the frictional force (resistance) acting on the engine 10, and the inertia of the crankshaft 10a of the engine 10 and the time derivative of the target engine speed, the target power generation of the alternator 25 can be accurately determined in a way that keeps the time derivative of the engine speed constant.

[0085] According to this embodiment, since the torque of the starter motor 26 is determined based on the engine speed, the torque of the starter motor 26 can be determined (estimated) with good accuracy.

[0086] Similarly, according to this embodiment, since the frictional force acting on the engine 10 is determined based on the engine speed and the water temperature or oil temperature, the frictional force acting on the engine can be determined (estimated) with good accuracy.

[0087] According to this embodiment, when the engine speed reaches or exceeds a predetermined speed (i.e., when it is determined that the engine 10 has completely detonated), the control (vibration suppression control) of the drive state (power generation) of the alternator 25 in a manner that keeps the time derivative of the engine speed constant is terminated. Therefore, the above-mentioned control (vibration suppression control) can be terminated at an appropriate time.

[0088] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the application of the present invention to a gasoline engine vehicle was described as an example, but the present invention can also be applied to vehicles with a driving power source other than a gasoline engine, such as hybrid electric vehicles (HEVs) with an engine and an electric generator (MG) as driving power sources. In this case, the electric generator (MG) functions as the generator described in the claims. In addition, other electric generators (MG) function as the starter described in the claims.

[0089] In the above embodiment, in order to keep the time derivative of the engine speed constant, the drive state (power generation) of the alternator 25 driven by the engine 10 is controlled. However, instead of the alternator 25, a configuration can be adopted to control the drive state (load state) of other auxiliary machines driven by the engine 10.

[0090] Furthermore, the system configuration described above is an example, and the system configuration of the present invention is not limited to the above-described embodiment. For example, ECU20 and ISCU40 can be integrated into one unit. Alternatively, a configuration that enables TCU (Transmission Control Unit) to have an idle stop function can be used instead of ISCU40.

Claims

1. An idle speed stop control device, characterized in that, have: An idle stop control mechanism that automatically stops the engine and puts it in an idle stop state when a predetermined idle stop condition is met, and automatically restarts the engine when a predetermined restart condition is met. as well as An auxiliary machine control mechanism controls the driving state of the auxiliary machine driven by the engine. When the auxiliary machine control mechanism automatically restarts the engine from the idle stop state via the idle stop control mechanism, it controls the driving state of the auxiliary machine driven by the engine in a manner that keeps the time derivative of the engine speed constant. The auxiliary machine is a generator. When the engine restarts, the auxiliary control mechanism sets a target engine speed in a manner that keeps the time derivative of the engine speed constant, and if the actual engine speed is higher than the target engine speed, it increases the generator's output in a manner that keeps the time derivative of the engine speed constant.

2. The idle speed stop control device according to claim 1, characterized in that, The auxiliary engine control mechanism calculates the target power generation of the generator based on the product of the engine torque, the starter torque that starts the engine, the friction force acting on the engine, the inertia of the engine crankshaft, and the time derivative of the target engine speed.

3. The idle speed stop control device according to claim 2, characterized in that, The auxiliary control mechanism calculates the starter torque based on the engine speed.

4. The idle speed stop control device according to claim 2 or 3, characterized in that, The auxiliary control mechanism calculates the frictional force acting on the engine based on the engine speed.

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