Control device of vehicle

Abstract

To suppress torque fluctuation at a time of return from fuel cut.SOLUTION: A control device (100) of a vehicle for controlling a vehicle (1) mounted with an internal combustion engine (2) and a motor generator (3) connected to the internal combustion engine (2) includes control means (103) which generates regenerative torque by the motor generator (3) when executing fuel cut of the combustion engine (2) at the time of deceleration, and reduces the regenerative torque after waiting an increase change of a rotation frequency of the internal combustion engine (2) after return from fuel cut, or slowing down of an increase change in angular speed of oscillation generated by a power train including the internal combustion engine (2) or waiting for the angular acceleration of the oscillation being changed from the increase change to a descent change so as to become a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that performs regenerative braking. [Background technology]

[0002] Some vehicles equipped with internal combustion engines implement a fuel cutoff system that stops the supply of fuel to the engine when the accelerator pedal is released to decelerate the vehicle. This can improve fuel economy and exhaust gas purification performance. If regenerative braking is performed when a fuel cut is performed during deceleration, kinetic energy can be recovered as electrical energy. In this case, when the fuel cut is resumed, regenerative braking is terminated. At this time, torque fluctuations occur due to a decrease in regenerative torque and the generation of engine torque due to combustion. If torque in the direction of vehicle forward movement is positive, the regenerative torque is negative and the engine torque is positive. As the negative torque decreases, positive torque is generated, resulting in large torque fluctuations. This large torque fluctuation may cause a feeling of the vehicle jumping out, which may adversely affect the ride comfort of the occupants. Furthermore, shocks caused by torque fluctuations before and after the fuel cut may cause oscillations in the powertrain, which may adversely affect the ride comfort of the occupants. Patent Document 1 discloses a control method in which regenerative braking is performed by a generator while fuel injection is stopped, and the amount of power generated by the generator is gradually reduced for a predetermined period after fuel injection is resumed. By gradually reducing the amount of power generated by the generator, an increase in torque fluctuation is suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6569592 [Patent Document 2] Patent No. 6699373 Summary of the Invention [Problem to be solved by the invention]

[0004] When returning from a fuel cut, if the timing of reducing the regenerative torque is poor, torque fluctuations cannot be suppressed, which may result in a deterioration in the ride comfort (feeling) of the passengers.

[0005] The present invention has been made in view of the above circumstances, and has as its object to suppress torque fluctuations when returning from a fuel cut. [Means for solving the problem]

[0006] The vehicle control device of the present invention is a vehicle control device that controls a vehicle equipped with an internal combustion engine and an electric motor / generator connected to the internal combustion engine, and is characterized in that when a fuel cut is performed on the internal combustion engine during deceleration, a regenerative torque is generated by the electric motor / generator, and after recovery from the fuel cut, the regenerative torque is reduced by waiting for the upward change in the rotation speed of the internal combustion engine or the upward change in the angular velocity of the oscillation generated in the powertrain including the internal combustion engine to slow down, or for the angular acceleration of the oscillation to change from an upward change to a downward change and reach a predetermined value. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress torque fluctuations when returning from a fuel cut. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a main part of an automobile according to an embodiment; [Figure 2] 3 is a flowchart showing an example of processing executed by the ECU 100. [Figure 3] 10A and 10B are characteristic diagrams showing examples of time-series changes in engine speed, swing angular velocity and swing angular acceleration, fuel cut on / off, regenerative torque, and accelerator position. DETAILED DESCRIPTION OF THE INVENTION

[0009] A vehicle control device (100) according to one embodiment of the present invention is a vehicle control device for controlling a vehicle (1) equipped with an internal combustion engine (2) and a motor-generator (3) connected to the internal combustion engine (2), and includes control means (103) that generates regenerative torque in the motor-generator (3) when a fuel cut is performed on the internal combustion engine (2) during deceleration, and reduces the regenerative torque after recovery from the fuel cut, by waiting for the increase in the rotation speed of the internal combustion engine (2) or the increase in the angular velocity of oscillation generated in a power train including the internal combustion engine (2) to slow down, or by waiting for the angular acceleration of the oscillation to change from an increase to a decrease and reach a predetermined value. This makes it possible to suppress torque fluctuations when returning from a fuel cut. [Example]

[0010] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a main part of an automobile 1, which is a vehicle according to the embodiment. As shown in FIG. 1, an automobile 1 is equipped with an engine 2 and a motor generator 3.

[0011] The engine 2 is an internal combustion engine having multiple cylinders, and is configured to output power by performing a series of four strokes for each cylinder, consisting of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. The power output by the engine 2 is speed-changed by a transmission 5 and transmitted to drive wheels (not shown).

[0012] The motor generator 3 is an electric motor / generator connected to the output shaft of the engine 2 via a belt 4 or the like. The motor generator 3 functions as an electric motor that rotates the output shaft of the engine 2 by being driven by power supplied from a battery 6. The motor generator 3 also functions as a generator that generates electricity by being driven by the rotation of the output shaft of the engine 2 and charges the battery 6. The motor generator 3 can vary the amount of electricity generated, thereby changing the regenerative torque during regenerative braking. Note that, although an example configuration in which the motor generator 3 is connected to the engine 2 via a belt 4 has been described, the present invention is not limited to this. For example, the motor generator may be mechanically connected to the output shaft of the engine 2 via a reducer or a clutch.

[0013] The automobile 1 is also equipped with an ECU (Electronic Control Unit) 100 that electronically controls various functions of the automobile 1. Various sensors, including an engine rotation speed sensor 8 and an accelerator position sensor 9, are connected to the ECU 100. The ECU 100 controls engine control such as fuel injection by an injector 7 attached to the engine 2, the opening and closing timing of the intake valves and exhaust valves of the engine 2, and the ignition timing of the spark plugs of the engine 2. Note that, since well-known technology can be applied to engine control, a detailed description thereof will be omitted here. The ECU 100 thus configured is configured by a computer unit including, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), a flash memory for storing backup data, etc., an input port, and an output port.

[0014] In this embodiment, the ECU 100 functions as a control device for a vehicle to which the present invention is applied. The following description will focus on the function of the ECU 100 as a control device for a vehicle to which the present invention is applied. The ECU 100 includes a fuel supply control unit 101 , a fluctuation period calculation unit 102 , and a regeneration control unit 103 .

[0015] The fuel supply control unit 101 executes a fuel cut to stop the fuel supply by the injector 7 when the accelerator is released (the accelerator pedal is released) to decelerate the vehicle while it is running. Furthermore, after the fuel cut, the fuel supply control unit 101 resumes fuel supply by the injector 7 in response to accelerator on, ie, depression of the accelerator pedal (recovery from fuel cut).

[0016] The oscillation period calculation unit 102 calculates the period T of oscillation occurring in the powertrain including the engine 2 (hereinafter referred to as the oscillation period). Oscillation can occur in the powertrain starting from a shock caused by torque fluctuations before and after a fuel cut. As disclosed in Patent Document 2 by the present applicant, the engine oscillates toward the front of the vehicle (in the direction of travel) when a fuel cut occurs, and oscillates toward the rear of the vehicle (in the direction of retreat) when the fuel cut is resumed. For the same vehicle, this oscillation is roughly determined by the total reduction gear ratio. The angular velocity of the oscillation in a fuel supply state (hereinafter referred to as the oscillation angular velocity) can be calculated from the difference between the engine rotation speed and the product of the wheel rotation speed (vehicle speed) and the total reduction gear ratio, and the oscillation period T can be calculated. Furthermore, the angular acceleration of the oscillation (hereinafter referred to as the oscillation angular acceleration) can be calculated from the oscillation angular velocity.

[0017] The regeneration control unit 103 causes the motor generator 3 to generate regenerative torque when a fuel cut is executed under the control of the fuel supply control unit 101. Furthermore, when recovering from a fuel cut under the control of the fuel supply control unit 101, the regeneration control unit 103 waits for the increasing change in engine speed after recovery from the fuel cut to slow down before reducing the regenerative torque. As will be described in detail later, as shown in FIG. 3, when recovery from a fuel cut occurs, engine torque is generated by combustion and the engine speed increases, but at this time, the engine exhibits a behavior in which the increasing and decreasing trends are repeated cyclically. In this embodiment, the regeneration control unit 103 starts reducing the regenerative torque at the timing when the engine speed changes from an increasing trend to a decreasing trend after recovery from the fuel cut. Furthermore, the regenerative control unit 103 stops reducing the regenerative torque in half the time of the oscillation period T calculated by the oscillation period calculation unit 102 after starting to reduce the regenerative torque.

[0018] The processing executed by the ECU 100 and the behavior at that time will be described below with reference to Figures 2 and 3. Figure 2 is a flowchart showing an example of the processing executed by the ECU 100. The flowchart in Figure 2 is executed when fuel cut is performed during deceleration due to release of the accelerator while the vehicle is running, and when regenerative torque is being generated by the motor generator 3. Figure 3 is a characteristic diagram showing an example of time-series changes in engine speed, swing angular velocity and swing angular acceleration, fuel cut on / off, regenerative torque, and accelerator position.

[0019] In step S1, the ECU 100 waits until the accelerator is turned on based on the detection result of the accelerator position sensor 9, and when the ECU 100 detects that the accelerator is turned on, the process proceeds to step S2. In step S2, the fuel supply control unit 101 restarts the fuel supply by the injector 7 (recovery from the fuel cut). As shown in Figure 3, when the vehicle is decelerating due to the accelerator pedal being released while it is running, fuel is cut off and regenerative torque is generated (until timing t1). In this state, when the accelerator pedal is pressed, fuel is restored from the fuel cut (timing t1).

[0020] Returning to the explanation of Figure 2, in step S3, the regeneration control unit 103 waits until the timing at which the engine rotation speed changes from an increasing trend to a decreasing trend (the timing at which the engine rotation speed change from positive to negative) based on the detection result of the engine rotation speed sensor 8, and when the timing at which the engine rotation speed changes from an increasing trend to a decreasing trend arrives, the regeneration control unit 103 proceeds to step S4. In step S4, the regenerative control unit 103 starts reducing the regenerative torque. As shown in Figure 3, when the engine returns from the fuel cut (timing t1), engine torque is generated and the engine speed increases. Here, the characteristic lines of the engine speed and regenerative torque shown by the solid lines represent the characteristics of this embodiment. On the other hand, the characteristic lines of the engine speed and regenerative torque shown by the dotted lines represent the characteristics of a comparative example. The comparative example is an example in which the regenerative torque starts to decrease simultaneously with the return from the fuel cut. In the comparative example, immediately after returning from fuel cut, the regenerative torque decreases and engine torque is generated, causing large torque fluctuations and a sudden change in deceleration. At this time, the torsion in the powertrain system caused by the regenerative torque, which is a negative torque, is released, causing the engine speed to rise sharply and oscillations to occur due to the spring-mass system of the powertrain. As a result, the engine speed cyclically increases and decreases, and these upward and downward changes gradually converge. The period of this increase and decrease in the engine speed roughly coincides with the oscillation period T. To address this issue, in this embodiment, after recovery from fuel cut, the system waits for the increase in engine speed to slow down, specifically, starts reducing the regenerative torque at the timing when the engine speed changes from an increasing trend to a decreasing trend (timing t2). As a result, immediately after recovery from fuel cut, only engine torque due to combustion is generated, suppressing torque fluctuations and preventing a sudden change in deceleration. As a result, a sudden increase in engine speed is suppressed, and the increase and decrease in speed are made gradual, thereby suppressing fluctuations occurring in the powertrain.

[0021] In step S5, the oscillation period calculation unit 102 calculates the oscillation period T, which is the period of the oscillation occurring in the powertrain. For convenience, the oscillation period T is calculated in step S5, but the timing for calculating the oscillation period T is not limited to this, and the oscillation period T may be calculated in parallel with the flowchart of FIG. 2, for example.

[0022] In step S6, the regenerative control unit 103 waits until half the time (T / 2) of the oscillation period T calculated in step S5 has elapsed since starting to reduce the regenerative torque in step S4, and when half the time of the oscillation period T has elapsed, the process proceeds to step S7. In step S7, the regeneration control unit 103 ends the reduction of the regeneration torque. As shown in Fig. 3, after starting to reduce the regenerative torque at timing t2, the reduction of the regenerative torque ends (timing t3) when half the oscillation period T has elapsed. In this way, in order to suppress the oscillation of the powertrain, the regenerative torque is gradually reduced over the time period half the oscillation period T.

[0023] The degree to which the regenerative torque is reduced (the slope of the regenerative torque characteristic line from timing t2 to t3) may be set so that the regenerative torque reaches exactly 0 at the timing that reaches half of the oscillation period T, for example, each time the oscillation period T is calculated. Alternatively, the degree to which the regenerative torque is reduced may be set to a predetermined value. In this case, for example, if the regenerative torque does not reach 0 during the period from the start to the end of the first regenerative torque reduction, the regenerative torque reduction is started again when the engine speed next changes from an increasing trend to a decreasing trend, and the regenerative torque is reduced for half the oscillation period T. This process is repeated until the regenerative torque reaches 0. In this way, by reducing the degree to which the regenerative torque is reduced and reducing the regenerative torque over multiple periods, torque fluctuations can be further suppressed.

[0024] As described above, fuel cut is performed when the vehicle is decelerating due to the accelerator pedal being released while it is running, and while regenerative torque is being generated, the regenerative torque is reduced after the engine resumes from fuel cut and the increase in engine speed slows down. This makes it possible to suppress torque fluctuations when the engine resumes from fuel cut, and prevents a deterioration in the ride comfort for the occupants.

[0025] Furthermore, as in the comparative example of Figure 3, when the regenerative torque starts to be reduced simultaneously with recovery from fuel cut, it is conceivable to forcibly suppress the engine torque by retarding the engine ignition timing in order to suppress torque fluctuations. However, retarding the ignition timing reduces engine efficiency. In this embodiment, torque fluctuations are suppressed by optimizing the timing at which the regenerative torque is reduced, so it is possible to avoid retarding the ignition timing or reduce the amount of retardation, thereby preventing a decrease in engine efficiency.

[0026] In this embodiment, the regenerative torque is reduced when the engine speed changes from an increasing trend to a decreasing trend after the fuel cut is resumed, but this is not limiting. The regenerative torque may be reduced when the rate of change in the engine speed becomes equal to or less than a predetermined value after the fuel cut is resumed.

[0027] In addition, in this embodiment, after recovery from a fuel cut, the regenerative torque is reduced after waiting for the increase in the engine speed to slow down, but the regenerative torque may also be reduced using the vibration angular velocity or vibration angular acceleration related to the engine speed as an index. As described above, the oscillation angular velocity is calculated as the difference between the engine rotation speed and the rotation speed (vehicle speed) of the wheels multiplied by the total reduction ratio. Therefore, as shown in FIG. 3 , the oscillation angular velocity exhibits a behavior in which it periodically increases and decreases with the same cycle (oscillation cycle T) as the engine rotation speed, and the increase and decrease gradually converge. Therefore, after recovery from a fuel cut, the regenerative torque may be reduced after the increase in the oscillation angular velocity becomes gradual. Specifically, the regenerative torque may be reduced at timing t2, when the oscillation angular velocity changes from an increasing trend to a decreasing trend. Note that the oscillation angular velocity in FIG. 3 is illustrated as corresponding to the engine rotation speed indicated by the solid line, but the waveform is schematic and does not represent an exact value. Furthermore, the rocking angular acceleration is the time rate of change of the angular velocity. As shown in FIG. 3, the rocking angular acceleration periodically increases and decreases out of phase with the rocking angular velocity, and the increasing and decreasing trends gradually converge. Between timings t1 and t2, the rocking angular velocity increases, while the rocking angular acceleration changes from increasing to decreasing. Therefore, after recovery from fuel cut, the regenerative torque may be reduced after waiting for the rocking angular acceleration to decrease from increasing to a predetermined value. Specifically, the regenerative torque may be reduced at timing t2, when the rocking angular acceleration becomes zero. Note that the rocking angular acceleration in FIG. 3 is shown as corresponding to the engine speed indicated by the solid line, but the waveform is schematic and does not represent an exact value.

[0028] Furthermore, recovery from fuel cut is not limited to being caused by accelerator operation, but may also be caused by the engine speed dropping below a predetermined value. The timing for releasing the regenerative torque may also be changed depending on accelerator operation. For example, if the accelerator opening is large, the driver is requesting large torque, so the timing period for ending the reduction in regenerative torque may be advanced. Also, if there is a risk of engine stalling, such as during sudden deceleration, regenerative braking may be immediately ended. Furthermore, if there is no sign of an upward or downward trend in engine speed, regenerative braking may be ended after a timeout.

[0029] Although the embodiments of the present invention have been described in detail above with reference to the drawings, each embodiment merely shows a specific example of how the present invention can be implemented. The technical scope of the present invention is not limited to each embodiment. Various modifications of the present invention are possible within the scope of the gist of the present invention, and these modifications are also included within the technical scope of the present invention. A vehicle control device to which the present invention is applied is configured by a computer device equipped with, for example, a CPU, ROM, RAM, etc., and the functions of each means are realized by the CPU executing a predetermined program stored, for example, in the ROM. [Explanation of symbols]

[0030] 1: automobile, 2: engine, 3: motor generator, 100: ECU, 101: fuel supply control unit, 102: oscillation period calculation unit, 103: regeneration control unit

Claims

1. A vehicle control device that controls a vehicle equipped with an internal combustion engine and a motor generator connected to the internal combustion engine, When a fuel cut is performed on the internal combustion engine during deceleration, a regenerative torque is generated by the motor generator, A vehicle control device characterized by comprising a control means for reducing the regenerative torque after recovery from a fuel cut, by waiting for the increase in the rotation speed of the internal combustion engine or the increase in the angular velocity of the oscillation generated in a power train including the internal combustion engine to slow down, or by waiting for the angular acceleration of the oscillation to change from an increase to a decrease and reach a predetermined value.

2. a swing period calculation means for calculating a period of the swing; 2. The vehicle control device according to claim 1, wherein the control means starts reducing the regenerative torque and then finishes reducing the regenerative torque in half the period of the oscillation calculated by the oscillation period calculation means.

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