Power generation controller of hybrid vehicle

The present invention relates to a power generation control device for a hybrid vehicle having an engine for driving a generator and an electric motor for driving drive wheels.

In recent years, hybrid vehicles have been developed in which an engine and an electric motor are mounted as power sources. In such a hybrid vehicle, the engine usage area can be narrowed down to an efficient area by using an electric motor that generates high torque from low rotation as a power source at the time of starting or low speed, so that the engine efficiency can be improved. It can be improved to achieve low fuel consumption.

The drive system of this hybrid vehicle is a series system in which the drive wheels are driven using only an electric motor, a parallel system in which the drive wheels are driven using an electric motor and an engine, and a series system and parallel. A series-parallel system has been developed that combines the system with the system.

In series and series parallel type vehicles, a generator driven by the engine is installed, and the electric power generated by driving the generator is used in the electric motor to drive the drive wheels. At the same time as being supplied, the battery, which is a storage means, is charged in preparation for starting or accelerating. Whether or not the engine is started to drive the generator, that is, whether or not the generator is used to generate electricity is often determined according to the state of charge of the battery. For example, the state of charge is preset. A power generation control device has been developed that drives a generator when it falls below the lower limit level and stops the generator when the state of charge exceeds the upper limit level (see, for example, Patent Document 1).

Further, when the generator is driven by the engine, it is preferable to set a long switching cycle between the drive state and the stop state of the generator from the viewpoint of feeling and power generation efficiency. That is, if the switching cycle of the generator is set short, it is necessary to frequently switch the engine between the driving state and the stopped state, which not only gives the driver a sense of discomfort but also reduces the engine efficiency.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-98504 (Page 4, Fig. 6)</text></patcit>

<p> However, in order to set the switching cycle longer, if the lower limit level of the charged state is lowered and set, when the amount of discharge from the battery is small, the battery can be charged without exhausting the power, but the amount of discharge from the battery is high. If the amount is too high, the battery power may be exhausted. On the other hand, if the lower limit level of the charged state is raised and set in order to avoid the power exhaustion of the battery, the switching cycle of the generator will be set short, which will give the driver a sense of discomfort and reduce the engine efficiency. Become. As described above, when the lower limit level of the charged state is set in advance, it is difficult to both avoid the power exhaustion of the battery and set the switching cycle of the generator for a long time.</p><p> An object of the present invention is to avoid power depletion of the power storage means and to set a long switching cycle of the generator.</p>

<p> The power generation control device for a hybrid vehicle of the present invention is a power generation control device for a hybrid vehicle having an engine for driving a generator and an electric motor for driving a drive wheel, and stores power from the generator to store the electric motor. A power storage means for supplying power to the power storage means, a change rate calculation means for calculating the power amount change rate of the power storage means at predetermined intervals, a threshold setting means for setting a power generation threshold based on the power generation change rate, and the power storage. It is characterized by having a power generation control means for starting power generation by the generator when the state of charge of the means falls below the power generation threshold.</p><p> The power generation control device for a hybrid vehicle of the present invention is characterized in that the predetermined period is changed based on a traveling load signal.</p><p> The power generation control device for a hybrid vehicle of the present invention is characterized in that the traveling load signal is a vehicle speed.</p><p> The power generation control device for a hybrid vehicle of the present invention is characterized in that the predetermined period is changed based on the electric energy change rate.</p>

<p> According to the present invention, since the power generation threshold value is set based on the electric energy change rate calculated for each predetermined cycle, the timing of starting power generation can be accurately set according to the traveling situation. For example, when the amount of discharge from the power storage means is large and the rate of change in the amount of power is calculated to be large, power generation can be started early by setting the power generation threshold value high, and power depletion of the power storage means can be avoided. Can be done. On the other hand, when the amount of discharge from the power storage means is small and the rate of change in the amount of power is calculated to be small, the switching cycle between the power generation state and the non-power generation state can be set longer by setting the power generation threshold low. The engine efficiency when driving the generator can be improved, and a good feeling can be given to the driver.</p><p> Further, since the predetermined cycle is changed based on the traveling load signal, the responsiveness until the start of power generation can be improved. For example, in a running situation where the amount of discharge from the power storage means increases due to a large running load, that is, in a running situation where power generation is likely to be required, the running situation is achieved by setting a short predetermined cycle and updating the power generation threshold value at an early stage. It is possible to improve the responsiveness from the change of to the start of power generation.</p><p> Further, since the predetermined cycle is changed based on the rate of change in electric energy, the responsiveness until the start of power generation can be improved. For example, in a driving situation where the amount of discharge from the power storage means rapidly increases, that is, in a driving situation where power generation is likely to be required, the driving situation changes by setting a short predetermined cycle and updating the power generation threshold value at an early stage. It is possible to improve the responsiveness from the time when the power generation is started.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a drive device 10 of a hybrid vehicle. The drive device 10 shown in FIG. 1 is a drive device 10 applied to a hybrid vehicle for front-wheel drive, and has a drive motor 11 which is an electric motor and an engine 12 which is an internal combustion engine as power sources. The drive motor 11 has a motor output shaft 14 to which the motor side drive gear 13a is fixed, and a motor side driven gear 13b that meshes with the motor side drive gear 13a is fixed to the front wheel drive shaft 15 parallel to the motor output shaft 14. There is. Further, a final reduction gear 16 is fixed to the tip of the front wheel drive shaft 15, and a differential mechanism (not shown) is assembled to the final reduction gear 17 that meshes with the final reduction gear 16. The axle 18 extending from the differential mechanism in the vehicle width direction is connected to the front wheels as drive wheels, and the motor power transmitted from the drive motor 11 via the front wheel drive shaft 15 is transmitted to the left and right front wheels via the differential mechanism. It will be transmitted.

A generator, that is, a generator 21, is attached to the crankshaft 20 of the engine 12, and a rotor output shaft 22 is fixed to the rotor 21a of the generator 21. A coupling 24 is provided between the rotor output shaft 22 and the engine output shaft 23 arranged coaxially with the rotor output shaft 22 so as to operate in a engaged state for transmitting engine power and an open state for blocking the engine power. Further, the engine side drive gear 25a is fixed to the engine output shaft 23, and the engine side driven gear 25b that meshes with the engine side drive gear 25a is fixed to the front wheel drive shaft 15, and the coupling 24 is switched to the engaged state. The engine power is transmitted to the front wheels via the front wheel drive shaft 15. As the coupling 24 for transmitting engine power, a meshing type 2-way clutch that operates by energization control of an electromagnetic coil (not shown) is used, but a friction clutch that operates by energization control may be provided.

The generator 21 connected to the crankshaft 20 of the engine 12 has not only a function of generating electricity by engine power but also a function of a starter motor. Therefore, the engine 12 can be started by driving the generator 21 as a starter motor. In addition, the drive motor 11 has a function as a generator, and by operating the drive motor 11 as a generator when the vehicle is braked, kinetic energy can be converted into electrical energy and recovered. There is.

A hybrid vehicle equipped with such a drive motor 11 and an engine 12 has a series driving mode in which only the motor power is transmitted to the drive wheels, an engine driving mode in which only the engine power is transmitted to the drive wheels, and both motor power and engine power. It is equipped with parallel travel modes that transmit to the drive wheels, and these travel modes can be switched according to the travel conditions. Here, FIG. 2 is a characteristic diagram showing an example of the traveling mode switching characteristic. As shown in Fig. 2, the driving mode is set according to the vehicle speed, gradient, load, etc., and the series driving mode is set at low to medium speeds where a large driving torque is required, and the engine 12 is set high. The engine driving mode is set at high speeds (for example, 80km / h or more) that can be driven efficiently in the rotation range, and the parallel driving mode is set at high loads such as when accelerating or climbing a slope. There is.

The switching of these traveling modes is executed by switching and controlling the coupling 24 provided between the engine 12 and the front wheel drive shaft 15. That is, when the engine running mode or the parallel running mode is executed, the engine power is transmitted to the front wheel drive shaft 15, so that the coupling 24 is switched to the engaged state, while the engine power is cut off from the front wheel drive shaft 15. In the series running mode, the coupling 24 is switched to the released state, and the engine 12 is separated from the front wheel drive shaft 15. Then, in this series running mode, when the running situation requires power generation by the generator 21, the engine 12 drives the generator 21 in an efficient rotation speed region after the engine 12 is started by using the generator 21. Become. Even in the engine traveling mode or the parallel traveling mode, if the load applied to the engine 12 is small, the power generation control using the surplus power is executed according to the vehicle state.

FIG. 3 is a block diagram showing an electrical system and a control system of a hybrid vehicle. As shown in FIG. 3, the hybrid vehicle is provided with various control units 30 to 32, and these control units 30 to 32 detect the drive state of each drive unit and output a control signal to each drive unit. ing. These control units 30 to 32 are connected to each other via a communication cable, and a communication network 33 for communicating detection signals and control signals between the control units is constructed in the hybrid vehicle. Each control unit 30 to 32 is provided with a CPU for calculating control signals, a ROM for storing control programs, calculation formulas, map data, etc., and a RAM for temporarily storing data. ..

As shown in FIG. 3, the hybrid vehicle is equipped with a drive battery 34 as a storage means for storing the electric power generated by the generator 21 and supplying the electric power to the drive motor 11. A battery control unit 30 is provided in the drive battery 34, and the battery control unit 30 detects the voltage Vbat, the current Ibat, the cell temperature, and the like of the drive battery 34. Then, the battery control unit 30 calculates the charge state SOC (state of charge) of the drive battery 34 based on the voltage Vbat, the current Ibat, and the cell temperature. Although the drive battery 34 is mounted as the power storage means, a capacitor may be mounted instead of the drive battery 34.

Further, an inverter 35 for the generator is provided between the drive battery 34 and the generator 21, and the alternating current generated by the generator 21 of the AC synchronous motor is converted into a direct current through the inverter 35. After that, the drive battery 34 is charged. Then, when the generator 21 is driven as a starter motor, the direct current from the drive battery 34 is converted into an alternating current via the inverter 35 and then supplied to the generator 21.

Similarly, an inverter 36 for the drive motor is provided between the drive battery 34 and the drive motor 11, and the direct current from the drive battery 34 is converted into an alternating current via the inverter 36. Later, it was supplied to the drive motor 11 of the AC synchronous motor. Then, the alternating current generated by the regenerative brake, that is, the alternating current generated by the drive motor 11 when the vehicle is braked, is converted into a direct current via the inverter 36 and then charged into the drive battery 34. Become.

Further, the hybrid vehicle is provided with an engine control unit 31 for driving and controlling the engine 12, and the driving state of the engine 12 is input to the engine control unit 31 from various sensors. Further, signals such as the accelerator opening degree, the vehicle speed V, and the shift range are input to the engine control unit 31 from the drive system control unit 32, which will be described later, via the communication network 33. Based on these various signals, the engine control unit 31 controls the driving state of the engine 12 by outputting control signals to the throttle valve, the injector, the igniter, and the like.

Further, the hybrid vehicle is provided with a drive system control unit 32 that drives and controls the drive device 10. An accelerator pedal sensor 37 that detects the accelerator opening and a shift position sensor 38 that detects the shift range are connected to the drive system control unit 32, and the rotor output shaft 22, the engine output shaft 23, and the front wheel drive shaft 15 are connected. A rotation speed sensor (not shown) that detects the rotation speed of the above is connected. Further, the drive states of the engine 12, the drive motor 11 and the generator 21, the charge state SOC of the drive battery 34, the current Ibat, the voltage Vbat, and the like are input via the communication network 33. Then, the drive system control unit 32 sets the traveling mode based on the accelerator opening degree input from the accelerator pedal sensor 37 and the vehicle speed V calculated from the rotation speed of the front wheel drive shaft 15, and various input signals. Based on the above, control signals are output to the coupling 24, engine control unit 31, and inverters 35 and 36.

The traveling status of the hybrid vehicle controlled by each of the control units 30 to 32 is displayed on the instrument panel, that is, the instrument panel 39 provided in the vehicle interior, so that the driver can recognize the traveling status. The body integrated control unit 40 is connected to the communication network 33 described above, and the drive state of the engine 12, the drive motor 11, and the generator 21 and the charge state SOC of the drive battery 34 are determined by the body integrated control unit 40. It is output to the instrument panel 39 via.

The hybrid vehicle is equipped with an auxiliary battery 41 (for example, 12V) having a voltage lower than that of the driving battery 34 in order to supply current to electrical components such as auxiliary equipment. In order to charge the auxiliary battery 41, a DC / DC converter 42 is provided between the auxiliary battery 41 and the drive battery 34, and a high voltage current generated for the drive battery 34 is provided. Is converted to a low voltage current for the auxiliary battery 41.

Next, the procedure for determining the start of power generation in the series running mode will be described. FIG. 4 is a diagram showing the fluctuation state of various data in the process up to the start of power generation, and FIG. 5 is a flowchart showing the procedure up to the start of power generation. First, the procedure for starting power generation will be roughly described with reference to FIG. As shown in FIG. 4, the drive system control unit 32 that functions as the rate of change calculation means, the threshold setting means, and the power generation control means is a drive battery 34 based on the current Ibat and the voltage Vbat input from the battery control unit 30. The charge / discharge power Wbat of is calculated, and the integrated power value Ebat obtained by integrating the charge / discharge power Wbat is calculated. Next, after calculating the integrated value change rate DEbat, which is the power amount change rate of the integrated power value Ebat, for each calculation cycle Tpre as a predetermined cycle, the power generation threshold Gsoc is set based on this integrated value change rate DEbat. When it is determined that the charging state SOC is lower than the power generation threshold Gsoc newly set for each calculation cycle Tpre in this way, the engine 12 and the generator 21 are driven and controlled, and the power generation by the generator 21 is started. It has become. Hereinafter, such power generation start determination will be described in detail with reference to the flowchart of FIG.

As shown in FIG. 5, in step S1, the charge / discharge power Wbat of the drive battery 34 is calculated by multiplying the current Ibat and the voltage Vbat, and in step S2, the charge / discharge power Wbat is added for each routine. The integrated power value Ebat is calculated. Then, in step S3, it is determined whether or not the counter Cnt is 0, and if it is determined that the counter Cnt is 0, the integrated initial value Eint is set in step S4, and then the counter Cnt is set in step S5. Is counted. On the other hand, if it is determined in step S3 that the counter Cnt is other than 0, the process proceeds to step S5 as it is, and the counter Cnt is counted.

In step S6, the calculation cycle Tpre is set by referring to the cycle table based on the vehicle speed V which is a traveling load signal. Here, FIG. 6A is a characteristic diagram showing an example of a cycle table, and as shown in FIG. 6A, the calculation cycle Tpre is shortened at high vehicle speeds where the traveling load is higher than at low vehicle speeds. Is set to. In the following step S7, when it is determined that the counter Cnt exceeds the calculation cycle Tpre set based on the cycle table, the calculation cycle Tpre has elapsed since the routine for setting the power generation threshold Gsoc was started. Therefore, the process proceeds to step S8, and the integrated value change rate DEbat is calculated based on the following equation (1). That is, the integrated value change rate DEbat is the average power value of the charge / discharge power Wbat within the calculation cycle Tpre. In the case shown in Fig. 4, the calculation cycle Tpre is almost constant because the vehicle is traveling at a constant vehicle speed, but it is said that the calculation cycle Tpre is changed as the vehicle speed V fluctuates. Not to mention.

DEbat = (Ebat-Eint) / Cnt (1)

When the integrated value change rate DEbat is calculated in step S8, the counter Cnt is reset in step S9, and in the following step S10, the power generation threshold Gsoc is set by referring to the threshold table based on the integrated value change rate DEbat. .. Here, FIG. 6B is a characteristic diagram showing an example of the threshold table, and as shown in FIG. 6B, the more the integrated value change rate DEbat increases, that is, the amount of discharge from the drive battery 34. The larger the number, the higher the power generation threshold Gsoc is set.

Then, in step S11, the power generation threshold Gsoc and the charged state SOC are compared and determined, and if it is determined that the charged state SOC is lower than the power generation threshold Gsoc, the power generation flag is set and the engine 12 is set in the following step S12. A control signal is output to and the generator 21, and power generation by the generator 21 is started. On the other hand, in step S11, when it is determined that the charging state SOC exceeds the power generation threshold Gsoc, the routine is exited with the power generation stopped. A predetermined upper limit level is set for the charged state SOC, and when the charged state SOC reaches the upper limit level due to power generation, the power generation by the generator 21 is stopped.

In this way, since the power generation threshold Gsoc is changed according to the integrated value change rate DEbat, it is possible to accurately set the power generation start timing according to the running condition of the hybrid vehicle. That is, when the amount of discharge from the drive battery 34 is large and the integrated value change rate DEbat is calculated to be large, the power generation threshold Gsoc is set high, so that power generation can be started early and the drive battery 34 can be started. It is possible to avoid power depletion. On the other hand, when the amount of discharge from the drive battery 34 is small and the integrated value change rate DEbat is calculated to be small, the power generation threshold Gsoc is set low, so that the switching cycle between the power generation state and the non-power generation state of the generator 21 is lengthened. It can be set to increase engine efficiency when driving the generator 21 and give the driver a good feeling.

Further, since the calculation cycle Tpre is changed according to the vehicle speed V as the traveling load signal, the responsiveness from the change of the traveling condition to the start of power generation can be improved. That is, in the high vehicle speed range where a large amount of electric power is supplied to the drive motor 11, the power generation by the generator 21 is likely to be required. By updating Gsoc, it is possible to improve the responsiveness from the change in driving conditions to the start of power generation. The traveling load signal is not limited to the vehicle speed V, and an accelerator opening degree or a shift range signal indicating the driver's intention to accelerate may be used.

In the explanation so far, the power generation threshold Gsoc is updated every time the calculation cycle Tpre set according to the vehicle speed V elapses, but depending on the driving situation, it is before the calculation cycle Tpre elapses. Also, the power generation threshold Gsoc will be updated. Next, the running situation in which the power generation threshold value Gsoc is updated before the calculation cycle Tpre elapses will be described.

As shown in FIG. 5, when it is determined in step S7 that the counter Cnt is less than the calculation cycle Tpre, the process proceeds to step S13, and the discharge amount (Ebat-Eint) of the drive battery 34 is set to a predetermined upper limit value Emax. It is judged whether or not it exceeds. If it is determined in step S13 that the discharge amount (Ebat-Eint) exceeds the upper limit value Emax, the discharge amount from the drive battery 34 is rapidly increasing, so the process proceeds to step S8 and the integrated value changes. After the rate DEbat is calculated and the power generation threshold Gsoc is updated in the following step S10, the charged state SOC and the new power generation threshold Gsoc are compared and judged in step S11. That is, when the integrated value change rate DEbat increases sharply, the calculation cycle Tpre is shortened and a new power generation threshold Gsoc is set. On the other hand, if it is determined in step S13 that the discharge amount (Ebat-Eint) is below the upper limit value Emax, a new power generation threshold Gsoc is not set, and the process proceeds to step S11, and the charging state SOC and the previous time are reached. Will be compared and judged with the power generation threshold Gsoc.

Here, FIG. 7 is a diagram showing the fluctuation state of various data in the process up to the start of power generation, and shows the situation where the driver depresses the accelerator pedal in the series driving mode. As shown by the symbol a in FIG. 7, when the discharge amount (Ebat-Eint) exceeds the upper limit value Emax due to the accelerator pedal being depressed and the power supply to the drive motor 11 being increased, the setting is based on the vehicle speed V. Even before the calculated calculation cycle Tpre elapses, a new power generation threshold Gsoc is set, and the power generation threshold Gsoc and the charged state SOC are compared and judged. In this way, in a situation where the amount of discharge from the drive battery 34 suddenly increases, the calculation cycle Tpre is shortened and the power generation threshold Gsoc is updated without waiting for the set calculation cycle Tpre to elapse. Therefore, it is possible to improve the responsiveness from the change in the traveling condition to the start of power generation.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof. For example, the power generation control device of the present invention is applied to a front-wheel drive hybrid vehicle, but is not limited to this, and may be applied to a rear-wheel drive or four-wheel drive hybrid vehicle. Further, the present invention is not limited to the series / parallel hybrid vehicle, and the present invention may be applied to the series / parallel hybrid vehicle. Further, the present invention may be applied to a hybrid vehicle in which a transmission mechanism is provided in a transmission path of engine power.

Further, in the above description, the charge / discharge power Wbat is replaced with the power integrated value Ebat, and the power generation threshold Gsoc is set from the integrated value change rate DEbat of the power integrated value Ebat, but the charge / discharge is not limited to this. The rate of change within the calculation cycle Tpre may be calculated directly from the power Wbat, and the power generation threshold Gsoc may be set based on this rate of change.

Further, although the battery control unit 30 calculates the charge state SOC of the drive battery 34, it goes without saying that the drive system control unit 32 may calculate the charge state SOC.

<figref num="1">It is the schematic which shows the drive device of a hybrid vehicle.</figref><figref num="2">It is a characteristic diagram which shows an example of a traveling mode switching characteristic.</figref><figref num="3">It is a block diagram which shows the electric system and the control system of a hybrid vehicle.</figref><figref num="4">It is a diagram which shows the fluctuation state of various data in the process until the start of power generation.</figref><figref num="5">It is a flowchart which shows the procedure until the start of power generation.</figref><figref num="6">(A) is a characteristic diagram showing an example of a periodic table, and (B) is a characteristic diagram showing an example of a threshold table.</figref><figref num="7">It is a diagram which shows the fluctuation state of various data in the process until the start of power generation.</figref>

Code description

11 Drive motor (electric motor) 12 Engine 21 Generator (generator) 32 Drive system control unit (change rate calculation means, threshold setting means, control means) 34 Drive battery (storage means) SOC charge state Wbat Charge / discharge power DEbat integration Value change rate (electric energy change rate) Tpre calculation cycle (predetermined cycle) Gsoc Power generation threshold V Vehicle speed (travel load signal)