Vehicle transmission control device

Abstract

To provide a shift control device for a vehicle, which can continuously supply fuel which is divided in the number of times required.SOLUTION: Provided is a shift control device for a vehicle, which can execute division injection control to supply fuel which is divided in a plurality of times in a stroke for supplying the fuel to an internal combustion engine, comprising a controller for changing a transmission gear ratio of a transmission mechanism. The controller, in a cold condition in which the temperature of the internal combustion engine is a predetermined temperature or lower, and when the division injection control is executed, sets an upper limit rotation speed of the internal combustion engine to a predetermined rotation speed allowing the division injection control, and executes up-shift operation for reducing a transmission gear ratio of the transmission mechanism before the rotation speed of the internal combustion engine exceeds the upper limit rotation speed (step S5).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a shift control device for a vehicle equipped with a transmission mechanism for controlling the rotational speed of an internal combustion engine, and more particularly to a device for controlling the rotational speed of an internal combustion engine that can set the number of fuel injection times to a plurality of times.

Background Art

[0002] Patent Document 1 describes a fuel injection control device configured to execute split fuel injection control in which fuel is injected into a cylinder in a plurality of times during a compression process in order to suppress deterioration of emissions due to fuel adhering to the wall surface or piston in the cylinder. This fuel injection control device is configured to set a required injection amount of fuel, the number of splits for injecting fuel during the compression stroke, and a pause interval time, which is a period between the supply timings of the split fuel, based on the engine rotational speed and the intake air amount. Further, when the engine rotational speed increases while such split fuel injection control is being executed and a sufficient interval time cannot be ensured, the number of split injections is configured to be reduced. Specifically, by excluding one interval, the injection time in a predetermined fuel injection is configured to be lengthened.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the engine speed increases while the fuel injection control device described in Patent Document 1 is executing split fuel injection control, the injection time in a predetermined fuel injection is lengthened to reduce the number of split injections. However, since the fuel injection amount per time is set to an amount that suppresses the adhesion of fuel to the cylinder wall surface and the piston, if the fuel injection time is lengthened as in the fuel injection control device described in Patent Document 1, the fuel may not be sufficiently vaporized at the lengthened timing, and there is a possibility that deterioration of emissions cannot be suppressed.

[0005] The present invention has been made paying attention to the above technical problems, and an object thereof is to provide a vehicle transmission control device capable of continuously supplying fuel divided into the required number of divisions.

Means for Solving the Problems

[0006] In order to achieve the above object, the present invention is a vehicle transmission control device including an internal combustion engine and a transmission mechanism capable of changing a transmission ratio between the internal combustion engine and drive wheels, and during a stroke of supplying fuel to the internal combustion engine, the fuel can be supplied by being divided into a plurality of times. A split injection control is executed, and the vehicle transmission control device includes a controller that changes the transmission ratio of the transmission mechanism. When the temperature of the internal combustion engine is in a cold state below a predetermined temperature and the split injection control is being executed, the controller sets the upper limit rotational speed of the internal combustion engine to a predetermined rotational speed at which the split injection control is possible, and before the rotational speed of the internal combustion engine exceeds the upper limit rotational speed, an upshift for reducing the transmission ratio of the transmission mechanism is executed.

[0007] In the present invention, the controller may obtain a reduction amount of the output of the internal combustion engine due to execution of the upshift, obtain a compensation torque for increasing the torque of the internal combustion engine in order to compensate for the reduction amount of the output of the internal combustion engine, and execute a compensation control for increasing the intake air amount of the internal combustion engine based on the compensation torque.

[0008] In the present invention, the drive wheels are further provided with a motor connected thereto so as to be able to transmit torque, and the controller calculates a decrease in driving force corresponding to a decrease in the output of the internal combustion engine due to execution of the upshift, calculates a compensation torque required for the motor to compensate for the decrease in driving force, and may execute compensation control for increasing the output torque of the motor based on the compensation torque.

Advantages of the Invention

[0009] According to the present invention, when the temperature of the internal combustion engine is at or below a predetermined temperature and split injection control is being executed, the upper limit rotational speed of the internal combustion engine is set to a predetermined rotational speed at which split injection control is possible. Also, the transmission mechanism is upshifted before the rotational speed of the internal combustion engine exceeds the upper limit rotational speed. Therefore, when the engine rotational speed increases to the predetermined rotational speed at which split injection control is possible due to an increase in vehicle speed or the like while split injection control is being executed, an upshift is executed at that time, so that the rotational speed of the internal combustion engine can be maintained at or below the rotational speed at which split injection control is possible. As a result, it is possible to suppress interruption or cancellation of the split injection control under conditions where split injection control is required to be executed. Also, in order to continue such split injection control, it is not necessary to change the number of injections. That is, it is possible to continue supplying fuel divided into the required number of injections. Therefore, it is possible to suppress deterioration of emissions due to fuel adhering to the inner wall surface of the cylinder or the piston in the internal combustion engine.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] The present invention will be described based on the embodiments shown in the drawings. Note that the embodiments described below are merely examples when the present invention is embodied, and do not limit the present invention.

[0012] FIG. 1 shows a schematic diagram for explaining an example of a vehicle in an embodiment of the present invention. The vehicle Ve shown in FIG. 1 includes an internal combustion engine (hereinafter referred to as an engine) 1 as a driving force source. This engine 1 is a direct injection spark ignition engine. That is, the engine 1 is formed with a plurality of cylinders 2, and each cylinder 2 is provided with an injector 3 that injects fuel directly into the cylinder 2 and a spark plug (not shown) that ignites the air-fuel mixture in the cylinder 2.

[0013] The above injector 3 can be configured in the same manner as a conventional injector. That is, it includes a valve body that opens and closes the injection port, an elastic body that presses the valve body toward the injection port side, and a solenoid that generates an electromagnetic force in a direction to separate the valve body from the injection port. Further, the injector communicates with a pump that pressurizes fuel. Therefore, by controlling the electric power supplied to the solenoid to separate the valve body from the injection port, the fuel output from the pump is injected into the cylinder 2 through the injector 3. On the contrary, by stopping the power supply to the solenoid, the valve body abuts against the injection port, and the fuel injection is configured to stop.

[0014] This solenoid is connected to an electric circuit that includes a capacitor charged by a power source (not shown) and a switch that selectively connects the capacitor and the solenoid. Therefore, after the capacitor has charged the power corresponding to the electromagnetic force capable of opening the valve body, by connecting the capacitor and the solenoid with the switch, the valve body can be separated from the injection port and fuel can be injected into the cylinder 2.

[0015] In addition, an intake pipe 5 is connected to each cylinder 2 via an intake manifold 4, and a throttle valve 6 for controlling the amount of air flowing through the intake pipe 5 is provided in the intake pipe 5. Note that a throttle opening sensor 7 for detecting the opening degree of the throttle valve 6 is provided.

[0016] A pair of drive wheels 11 are connected to the above-described engine 1 via a transmission mechanism (T / M) 8, a differential gear unit 9, and a drive shaft 10. This transmission mechanism 8 is configured to change the transmission ratio between the engine 1 and the drive wheels 11, similar to various conventional transmission mechanisms. Specifically, it can be configured by a stepped transmission mechanism capable of setting a plurality of transmission speeds (transmission ratios) or a continuously variable transmission mechanism capable of continuously changing the transmission ratio. Note that the continuously variable transmission mechanism may be a mechanical continuously variable transmission such as a belt-type continuously variable transmission that changes the transmission ratio by changing the winding radius of a belt or a toroidal-type continuously variable transmission that changes the transmission ratio by changing the inclination angle of a power roller, or an electric continuously variable transmission that includes a differential mechanism and a motor and changes the transmission ratio by changing the rotation speed of the motor. In the following description, a vehicle equipped with a stepped transmission mechanism will be described as an example.

[0017] When the multi-injection control (split injection control) described later is not being executed, this transmission mechanism 8 performs shift control based on a shift map using vehicle speed and accelerator opening as parameters, in the same manner as the shift control of a conventional stepped transmission. When the transmission mechanism 8 is a continuously variable transmission mechanism, target engine torque and target engine speed are determined based on a predetermined optimal fuel consumption line and the required power of the engine 1, in the same manner as the shift control of a conventional continuously variable transmission, and shift control is performed to achieve the target engine speed.

[0018] An electronic control unit (hereinafter referred to as ECU) 12 for controlling the engine 1 and the transmission mechanism 8 is provided. This ECU 12 corresponds to the "controller" in the embodiment of the present invention. The ECU 12 is mainly composed of a microcomputer, and signals are input from various sensors provided in the vehicle Ve, and it is configured to control the engine 1 and the transmission mechanism 8 based on the input signals and maps, arithmetic expressions, etc. stored in advance. In the example shown in FIG. 1, signals are input to the ECU 12 from a vehicle speed sensor 13 that detects vehicle speed, an engine speed sensor 14 that detects engine speed, a throttle opening sensor 7, an engine temperature sensor 15 that detects engine coolant temperature, and an accelerator opening sensor 16 that detects the operation amount of an accelerator pedal (not shown).

[0019] Then, the ECU 12 sets the intake air amount to the engine 1, the fuel injection amount, the ignition timing by the spark plug, and the gear position of the transmission mechanism 8 based on the above input signals, and outputs signals corresponding to the set parameters to the throttle valve 6, the injector 3, the spark plug, and an actuator (not shown) for setting the gear position of the transmission mechanism 8.

[0020] FIG. 2 shows a flowchart for explaining an example of control executed by the ECU 12. In the control example shown in FIG. 2, first, it is determined whether the engine 1 is cold (step S1). This step S1 is a step for determining whether the warm-up of the engine 1 is completed. Therefore, in step S1, it may be determined whether the temperature detected by the engine temperature sensor 15 is equal to or higher than a predetermined temperature at which it can be determined that the warm-up is completed.

[0021] If it is negatively determined in step S1 because the engine 1 is not cold, this routine is once terminated as it is. On the contrary, if it is positively determined in step S1 because the engine 1 is cold, it is determined whether the integrated air amount after starting the engine 1 is equal to or greater than a predetermined amount (step S2). This step S2 is a step for determining whether the temperature in the cylinder 2 of the engine 1 is equal to or higher than a temperature at which the particulate (or mist-like) fuel injected from the injector 3 can be rapidly vaporized. Therefore, in step S2, the integrated air amount corresponding to the work amount of the engine 1 is used as a parameter. This is because it is possible to determine the temperature in the cylinder 2 more quickly and accurately by using the integrated air amount of the engine 1 as a parameter to determine the temperature in the cylinder 2 than by using the engine water temperature as a parameter to determine the temperature in the cylinder 2. However, the temperature in the cylinder 2 may also be determined based on the engine water temperature or other parameters. Note that the predetermined amount in step S2 can be set to a value obtained by experiments or simulations, which is the integrated air amount at which the temperature in the cylinder 2 is equal to or higher than the temperature at which the particulate fuel can be rapidly vaporized.

[0022] On the contrary, when it is negatively determined in step S2 because the integrated air quantity is less than a predetermined amount after the engine 1 is started, the temperature in the cylinder 2 is low, and the fuel is in a state where it is difficult to vaporize. In such a case, if the fuel amount required for one injection of fuel is injected into the cylinder 2 at once, a part of the supplied fuel may adhere to the inner wall surface or the piston head of the cylinder 2 without vaporizing before being ignited by the spark plug. When the fuel adheres to the inner wall surface or the piston head of the cylinder 2 in this way, there is a possibility that the exhaust emissions may deteriorate, for example, due to not achieving the intended air-fuel ratio, or there is a possibility that the intended driving force cannot be obtained.

[0023] Therefore, when it is negatively determined in step S2, multi-injection control is configured to be executed to suppress fuel from adhering to the wall surface or the piston head in the cylinder 2 without vaporizing by reducing the fuel amount for one injection. Specifically, during the compression stroke in which the air-fuel mixture is compressed, the fuel to be mixed with the air supplied to the cylinder 2 is divided and injected a predetermined number of times.

[0024] Therefore, when it is negatively determined in step S2, subsequently, it is determined whether multi-injection control is being executed (step S3). When it is negatively determined in step S3 because multi-injection control is not being executed, multi-injection control is executed (step S4), and this routine is terminated once.

[0025] On the other hand, since the multi-injection control is a control that performs multiple injections during the compression stroke as described above, as the engine speed increases, the time (interval) between injections becomes shorter. That is, the charging time of the capacitor that supplies power to the injector 3 becomes shorter.

[0026] FIG. 3 shows a graph in which the amount of energy (electric energy) that can be charged to the capacitor, i.e., the amount of energy that can be consumed by injector 3, is plotted for each engine speed when four fuel injections are performed. In FIG. 3, the engine speed is taken on the vertical axis and the amount of energy that can be consumed by injector 3 (INJ consumption E) is taken on the horizontal axis. As shown in FIG. 3, as the engine speed increases, the amount of energy that can be consumed by injector 3 decreases.

[0027] As described above, in injector 3, the valve body is pressed toward the injection port side by an elastic body, and an electromagnetic force acting against it is applied to the valve body to open the valve. The electromagnetic force does not depend on the engine speed. FIG. 3 shows the amount of energy E1 required to open the valve. As shown in FIG. 3, when the engine speed is equal to or higher than a predetermined speed, the amount of energy that can be charged to the capacitor becomes equal to or less than the amount of energy E1 required to open injector 3. That is, the predetermined speed becomes the limit speed of the multi-injection that performs four fuel injections.

[0028] Therefore, the shift control device in the embodiment of the present invention is configured to set the upper limit speed of engine 1 to the above-described predetermined speed (hereinafter referred to as the multi-injection limit speed) during multi-injection control so that multi-injection control can be continuously executed, and to upshift the transmission mechanism 8 before exceeding the multi-injection limit speed. Specifically, when it is positively determined in step S3 that multi-injection control is being executed, a gear stage at which the engine speed becomes equal to or less than the multi-injection limit speed is set (step S5). That is, the gear stage of the transmission mechanism 8 is controlled based on the engine speed.

[0029] When an upshift is performed so as to limit the engine speed to less than the multi-injection limit speed as described above, there is a possibility that the driving torque may become insufficient as the reduction ratio decreases. Therefore, in the control example shown in FIG. 1, torque compensation control is executed for step S5 (step S6), and this routine is once terminated.

[0030] FIG. 4 shows a flowchart for explaining an example of torque compensation control. In the example shown in FIG. 4, first, a compensation torque for compensating for a driving torque that becomes insufficient as the reduction ratio decreases is calculated (step S61). Specifically, the output of engine 1 (hereinafter referred to as the output at the time of limitation) output in a state where the engine speed is limited to the multi-injection limit speed is subtracted from the target output of engine 1 determined based on the accelerator opening and the vehicle speed. The output at the time of limitation of this engine 1 can be obtained by multiplying the target torque of engine 1 determined based on the accelerator opening and the vehicle speed in the same manner as normal engine control by the multi-injection limit speed. Then, the compensation torque is calculated by dividing the output reduction amount obtained by subtracting the output at the time of limitation from the target output of engine 1 by the multi-injection limit speed.

[0031] Next, a target torque at the time of limitation in a state where the engine speed is limited to the multi-injection limit speed is calculated (step S62). Specifically, the compensation torque calculated in step S61 is added to the target torque of engine 1 determined based on the accelerator opening and the vehicle speed in the same manner as normal engine control to calculate the target torque at the time of limitation.

[0032] Then, the throttle opening at the time when the engine speed is limited to the multi-injection limit speed is calculated (step S63), and this routine is temporarily terminated. That is, in step S63, the throttle opening that can achieve the target torque at the time of limitation obtained in step S62 is obtained. Note that in step S63, the throttle opening is obtained by setting the same fuel injection amount as in the normal state (when the engine speed is not limited).

[0033] FIG. 5 shows a time chart for explaining an example of changes in engine speed, gear position, multi-injection flag, air amount, throttle opening, and target torque when the control examples shown in FIGS. 2 and 4 are executed. When the control examples shown in FIGS. 2 and 4 are executed, that is, when shift control is performed so that the engine speed is equal to or lower than the multi-injection limit speed, changes in each parameter are indicated by solid lines. When shift control is performed based on conventional shift control, that is, when shift control is performed based on the accelerator opening and vehicle speed, changes in each parameter are indicated by broken lines.

[0034] In the example shown in FIG. 5, at time t0, the vehicle is stopped and engine 1 is stopped. Therefore, at this time t0, the temperature of engine 1 is low, and a positive determination is made in step S1 in FIG. 2.

[0035] At time t1, engine 1 starts, for example, by switching the ignition on, and the engine speed increases step by step. Also, when engine 1 starts, since the integrated air amount is less than a predetermined amount, a negative determination is made in step S2 in FIG. 2. On the other hand, at time t1, since multi-injection control is not being executed, a negative determination is made in step S3 in FIG. 2, and multi-injection control is executed. That is, the multi-injection flag is switched to ON.

[0036] At time t2, when the depression amount of the brake pedal decreases, the vehicle starts to move by creep torque at time t3, and accordingly, the engine speed and engine output start to increase. Further, when the accelerator pedal is depressed at time t4, a target torque is set based on the accelerator opening and vehicle speed, and the intake air amount and throttle opening start to increase. At time t4, since the engine speed is less than the multi-injection limit speed, the compensation torque obtained in step S61 in FIG. 4 is 0. Therefore, regardless of whether the engine speed is limited to the multi-injection limit speed, the target torque of engine 1 is obtained based on the accelerator opening and vehicle speed in the same manner as normal engine control.

[0037] As the vehicle speed increases, the engine speed gradually increases and reaches the multi-injection limit speed at time t5. Therefore, an upshift is executed at time t5 and the engine speed is decreasing. Since the upshift is performed so that the engine speed becomes less than the multi-injection limit speed, in the example shown in FIG. 5, upshifts are performed at time t6 and time t7. Then, at time t8, since the integrated air amount becomes equal to or more than a predetermined amount, it is positively determined in step S2 in FIG. 2, and the multi-injection control ends. As a result, even when the engine speed increases beyond the multi-injection limit speed, no upshift is performed. Therefore, the multi-injection control is continuously executed until time t8 when it is determined that the multi-injection control ends.

[0038] On the other hand, when the engine speed is not limited to the multi-injection limit speed, in other words, when determined based on the conventional shift control for setting the gear stage of the transmission mechanism 8 based on the accelerator opening and the vehicle speed, no upshift is determined at time t5. Therefore, the engine speed continues to increase beyond the multi-injection limit speed, an upshift is determined at time t9, and the engine speed decreases to below the multi-injection limit speed. Also, the engine speed that once decreased at time t9 increases, exceeds the multi-injection limit speed at time t6, and an upshift is determined again at time t10 and the engine speed is decreasing. In that case, the engine speed decreased by the upshift is equal to or more than the multi-injection limit speed, and from that state, the engine speed is increasing again.

[0039] Therefore, when the gear position of the transmission mechanism 8 is set based on the conventional shift control, since the engine speed exceeds the multi-injection limit speed at time t5, the multi-injection control is interrupted (the flag is OFF) at that time, and since the engine speed becomes equal to or lower than the multi-injection limit speed at time t9, the multi-injection control is restarted (the flag is ON). Further, since the engine speed exceeds the multi-injection limit speed at time t6, the multi-injection control is interrupted (the flag is OFF) again at that time. Note that at time t10, even if an upshift is performed, since the engine speed is equal to or higher than the multi-injection limit speed, the multi-injection control is not restarted.

[0040] As described above, the shift control device according to the embodiment of the present invention is shift-controlled so that the engine speed does not exceed the multi-injection limit speed under the condition where multi-injection control is required to be executed. Therefore, it is possible to suppress the interruption and cancellation of the multi-injection control under the condition where multi-injection control is required to be executed. Further, in order to continue such multi-injection control, it is not necessary to change the number of injections. That is, it is possible to continue to supply fuel in the required number of divided times. Therefore, it is possible to suppress the deterioration of emissions due to fuel adhering to the inner wall surface of the cylinder 2 and the piston.

[0041] Further, in order to suppress a decrease in the output of the engine 1 by maintaining the engine speed at or below the multi-injection limit speed as described above, torque compensation control is executed. That is, the target torque of the engine 1 is set higher than when the engine speed is not controlled to be at or below the multi-injection limit speed, and the intake air amount is increased so as to achieve the target torque. Therefore, as shown in FIG. 5, from time t5 to time t8, the target torque, the throttle opening, and the air amount are higher than when the engine speed is not controlled to be at or below the multi-injection limit speed.

[0042] By controlling the intake air amount of Engine 1 so as to suppress a decrease in the output of Engine 1 due to controlling the engine speed below the multi-injection limit speed, it is possible to suppress a decrease in the driving force.

[0043] Note that the vehicle in the embodiment of the present invention is not limited to a vehicle having only Engine 1 as a driving force source, and may be a hybrid vehicle having Engine 1 and a motor as driving force sources. In that case, a decrease in the output of Engine 1 due to controlling the engine speed of Engine 1 below the multi-injection speed may be configured to be compensated by increasing the output of the motor connected to be torque-transmittable to the drive wheels 11. Specifically, first, a decrease amount of the driving force corresponding to a decrease amount of the output of Engine 1 due to a decrease in the engine speed of Engine 1 is obtained, the decrease amount of the driving force is converted into torque, and a compensation torque is obtained by dividing the converted torque by the gear ratio between the motor and the drive wheels 11. Further, the output torque required for the motor may be increased by the amount of the compensation torque. By compensating for the decrease in the driving force by the motor in this way, it is possible to suppress a decrease in the driving force in the same manner as above.

Explanation of Reference Numerals

[0044] 1 Engine 2 Cylinder 3 Injector 6 Throttle Valve 7 Throttle Opening Sensor 8 Transmission Mechanism 11 Drive Wheels 12 ECU (Electronic Control Unit) Ve Vehicle

Claims

1. A vehicle transmission control device comprising an internal combustion engine and a transmission mechanism capable of changing the gear ratio between the internal combustion engine and the drive wheels, and capable of executing split injection control for supplying fuel in multiple divisions during the process of supplying fuel to the internal combustion engine, comprising a controller for changing the gear ratio of the transmission mechanism, wherein the controller, when it is cold and the temperature of the internal combustion engine is below a predetermined temperature and the split injection control is being executed, sets the upper limit rotational speed of the internal combustion engine to a predetermined rotational speed at which the split injection control is possible, and executes an upshift for reducing the gear ratio of the transmission mechanism before the rotational speed of the internal combustion engine exceeds the upper limit rotational speed. A vehicle transmission control device characterized by the above.

2. The vehicle transmission control device according to Claim 1, wherein the controller, obtains the amount of decrease in the output of the internal combustion engine due to the execution of the upshift, obtains a compensation torque for increasing the torque of the internal combustion engine in order to compensate for the amount of decrease in the output of the internal combustion engine, and executes compensation control for increasing the intake air amount of the internal combustion engine based on the compensation torque. A vehicle transmission control device characterized by the above.

3. The vehicle transmission control device according to Claim 1, further comprising a motor connected to the drive wheels so as to be capable of torque transmission, wherein the controller, obtains the amount of decrease in the driving force corresponding to the amount of decrease in the output of the internal combustion engine due to the execution of the upshift, obtains the compensation torque required for the motor in order to compensate for the amount of decrease in the driving force, and executes compensation control for increasing the output torque of the motor based on the compensation torque. A vehicle transmission control device characterized by the above.

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