Hybrid vehicle

Abstract

The disclosed hybrid vehicle (1) comprises an engine (2), a motor (3) for driving vehicle wheels and performing regenerative braking, a generator (4) for generating power by means of the driving force of the engine (2) and for driving the engine (2), and a battery (5) connected to the motor (3) and the generator (4). The hybrid vehicle also comprises a control device (10) that carries out regenerative motoring control in which regenerated electric power of the motor (3) is supplied to the generator (4) and the engine (2) is motored at a predetermined target rotation speed when the accelerator is off while the vehicle is traveling. The control device (10) calculates a required power generation amount in accordance with the traveling state, and if the required power generation amount is less than a threshold value when regenerative motoring control is stopped by an accelerator ON operation, the control device (10) carries out continuous motoring control in which the power of the battery (5) is supplied to the generator (4) to continue the motoring of the engine (2).

Description

Technical Field

[0001] The present invention relates to a hybrid vehicle that performs regenerative motoring control.

Background Art

[0002] Conventionally, there has been known a hybrid vehicle configured to obtain a regenerative braking force by charging a battery with regenerative power generated in a driving motor. In this type of hybrid vehicle, when the charging of the battery is restricted (for example, when the battery is nearly fully charged or when the battery fails), there is a risk that the regenerative braking force cannot be obtained. Therefore, a control (regenerative motoring control) has been proposed in which the regenerative power is consumed by a motor separate from the driving motor to rotate the engine idly, thereby balancing the power balance. By such control, it is possible to secure the regenerative braking force while restricting the charging of the battery (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described regenerative motoring control, the rotational speed when the engine is idling is set according to the magnitude of the regenerative power. On the other hand, when the accelerator pedal is depressed during the regenerative motoring control and regenerative power generation ends, if the starting condition of the engine is satisfied, the engine is controlled to self-rotate at a rotational speed according to the accelerator opening. As a result, there is a problem that the rotational speed of the engine fluctuates sharply, which may give a driver a sense of discomfort.

[0005] For example, in a situation where the engine rotation speed during regenerative motoring control is relatively high, when the accelerator pedal is lightly depressed, the engine rotation speed may suddenly decrease, and the engine noise and vibration may become extremely small. At this time, although the driver is trying to accelerate the vehicle, they feel as if the engine has become quiet. Therefore, it feels to the driver that the operation of the vehicle does not match the actual behavior, and a good driving feeling cannot be obtained.

[0006] One of the objectives of the present case is to be devised in light of the above problems, and to provide a hybrid vehicle capable of improving the driving feeling. In addition to this objective, any operational effects derived from each configuration shown in the "Mode for Carrying Out the Invention" described later and not achievable with conventional technologies are also regarded as other objectives of the present case.

Means for Solving the Problems

[0007] The disclosed hybrid vehicle can be realized as the modes or application examples disclosed below, and solves at least some of the above problems. The disclosed hybrid vehicle includes an engine, a motor that performs driving and regenerative braking of wheels, a generator that generates electricity by the driving force of the engine and drives the engine, a battery connected to the motor and the generator, and a control device that implements regenerative motoring control for supplying the regenerative power of the motor to the generator and motoring the engine at a predetermined target rotation speed during running and when the accelerator is off. The control device calculates a required power generation amount according to the running state, and when stopping the regenerative motoring control by an accelerator-on operation during the implementation of the regenerative motoring control, if the required power generation amount is less than a threshold value, it implements continuous motoring control for supplying the power of the battery to the generator and continuing the motoring of the engine.

Effects of the Invention

[0008] According to the disclosed hybrid vehicle, when regenerative motor control is stopped by an accelerator on operation, if the required power generation amount is less than the threshold value, continuous motor control is implemented. Continuous motor control is control in which power from the battery is supplied to the generator without regenerative braking the motor to continue the motoring of the engine. By implementing such control, it is possible to reduce the change in the engine rotation speed immediately after the end of regenerative motor control, and suppress sudden changes in the engine operating sound and vibration. Therefore, the drive feeling during acceleration from regenerative motor control can be improved.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] The disclosed hybrid vehicle can be implemented by the following embodiments.

Embodiment

[0011] [1. Device Configuration] FIG. 1 is a block diagram illustrating the configuration of a hybrid vehicle 1 as an example. This hybrid vehicle 1 (also simply referred to as vehicle 1) is a hybrid vehicle (hybrid electric vehicle, HEV) or a plug-in hybrid vehicle (plug-in hybrid electric vehicle, PHEV) equipped with an engine 2 and a motor 3 as drive sources, a generator 4 as a power generation device, and a battery 5 as a power storage device. A plug-in hybrid vehicle means a hybrid vehicle capable of external charging of the battery 5 or external power supply from the battery 5. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable through which electric power is supplied from an external charging facility, and an outlet for external power supply.

[0012] The engine 2 is an internal combustion engine such as a gasoline engine or a diesel engine, for example. A generator 4 is connected to the drive shaft of the engine 2. The generator 4 is a generator (motor-generator) having both a function of driving the engine 2 with the power of the battery 5 and a function of generating electricity using the driving force of the engine 2. The generated power of the generator 4 is used for driving the motor 3 or charging the battery 5. A transmission mechanism (not shown) may be interposed on the power transmission path connecting the engine 2 and the generator 4.

[0013] The motor 3 is a motor (motor-generator) having both a function of driving the vehicle 1 using the power of the battery 5 or the generated power of the generator 4 and a function of charging the battery 5 with the power generated by regenerative power generation. The battery 5 is a secondary battery such as a lithium-ion secondary battery or a nickel-metal hydride battery, for example. The drive shaft of the motor 3 is connected to the drive wheels of the vehicle 1. A transmission mechanism (not shown) may be interposed on the power transmission path connecting the motor 3 and the drive wheels.

[0014] A clutch 6 is interposed on the power transmission path connecting the engine 2 and the motor 3. The engine 2 is connected to the drive wheels via the clutch 6, and the motor 3 is disposed on the drive wheel side of the clutch 6. Further, the generator 4 is connected on the engine 2 side of the clutch 6. When the clutch 6 is disengaged (released), the engine 2 and the generator 4 are in a non-connected state with respect to the drive wheels, and the motor 3 is in a connected state with respect to the drive wheels. Therefore, for example, by operating only the motor 3, "EV driving (motor-only driving)" is realized. In addition to this, by operating the engine 2 to generate electricity in the generator 4, "series driving" is realized. Series driving means driving while generating electricity in the generator 4 with the driving force of the engine 2 and driving with the driving force of the motor 3.

[0015] On the other hand, when the clutch 6 is engaged (fastened), the engine 2, the motor 3, and the generator 4 are in a connected state with respect to the drive wheels. Therefore, for example, by operating only the engine 2, "engine driving (engine-only driving)" is realized. In addition to this, by driving the motor 3 or the generator 4, "parallel driving" is realized. The above series driving and parallel driving are both also called "hybrid driving".

[0016] The operating states of the engine 2, the motor 3, the generator 4, the battery 5, and the clutch 6 are controlled by the control device 10. The control device 10 is a computer (electronic control unit, ECU, Electronic Control Unit) having a function of controlling at least the operating states of the engine 2 and the generator 4. The control device 10 incorporates a processor (arithmetic processing unit) and a memory (storage device). The content of the control (control program) implemented by the control device 10 is stored in the memory, and the content is executed by being appropriately read into the processor.

[0017] In the control device 10 of this embodiment, an accelerator opening sensor 7, a brake opening sensor 8, and a vehicle speed sensor 9 are connected. The accelerator opening sensor 7 is a sensor that detects a parameter (such as accelerator opening, accelerator pedal stroke, throttle opening, etc.) corresponding to the depression amount of the accelerator pedal. The brake opening sensor 8 is a sensor that detects a parameter (such as brake opening, brake pedal stroke, brake fluid pressure, etc.) corresponding to the depression amount of the brake pedal. The vehicle speed sensor 9 is a sensor that detects the traveling speed (vehicle speed) of the vehicle 1. The information detected by each of these sensors 7 to 9 is transmitted to the control device 10.

[0018] Figure 2 is a graph illustrating the characteristics defining the relationship between the accelerator opening [%] detected by the accelerator opening sensor 7 and the driver required output [kW] set by the control device 10. The accelerator opening is the depression amount of the accelerator pedal (for example, accelerator pedal stroke or rotation angle with respect to the fulcrum of the accelerator pedal, etc.) expressed as a percentage. Also, the driver required output is a parameter corresponding to the magnitude of the output (in other words, horsepower, electric power, work rate) required by the driver to drive the vehicle 1. The driver required output is generally set to a larger value as the accelerator opening is larger. Note that the output of the drive source of the vehicle 1 is controlled so that it becomes a larger output as, for example, the driver required output or the vehicle speed is larger.

[0019] Figure 3 is a graph illustrating the relationship between the vehicle speed [km / h] detected by the vehicle speed sensor 9 and the target rotational speed [rpm] of the engine 2. The solid line graph in Figure 3 shows the characteristics during motoring of the engine 2 (when the vehicle 1 is decelerating), and the dashed line graph in Figure 3 shows the characteristics during firing of the engine 2 (when the vehicle 1 is accelerating). Motoring means rotating the engine 2 idly using the generator 4 (rotating the engine 2 without burning the fuel-air mixture in the cylinder), and firing means self-rotating the engine 2 by supplying fuel and intake air to the engine 2 (burning the fuel-air mixture in the cylinder). Firing can be carried out at least in a driving mode in which the engine 2 is operating, and can be carried out, for example, during series driving.

[0020] The target rotational speed of engine 2 during motoring is set to increase as the vehicle speed increases, as shown by the solid line graph in FIG. 3. However, in the high-speed region where the vehicle speed is equal to or higher than a predetermined vehicle speed, the target rotational speed of engine 2 is limited (clipped) to a predetermined upper limit rotational speed. Also, the target rotational speed of engine 2 during firing is set to a value smaller than the target rotational speed set during motoring for the same vehicle speed, as shown by the dashed line graph in FIG. 3.

[0021] When strictly adhering to the setting of the target rotational speed as shown in FIG. 3, when the state of engine 2 transitions from the motoring state to the firing state, the target rotational speed will necessarily decrease, and the drive feeling may deteriorate. For example, when the accelerator pedal is depressed during regenerative motoring control and engine 2 enters the firing state, the rotational speed of engine 2 (engine rotational speed) drops rapidly, giving the driver a sense of discomfort. In view of such problems, the control device 10 of this embodiment performs setting and control of a target rotational speed different from the characteristics of the dashed line graph in FIG. 3 when the accelerator is turned on (the accelerator opening exceeds a predetermined opening) during the execution of regenerative motoring control.

[0022] [2. Control Configuration] The control device 10 performs at least regenerative motoring control and continuous motoring control. Continuous motoring control is performed when the regenerative motoring control is stopped by an accelerator-on operation. Also, the control device 10 preferably performs first power generation control and second power generation control in addition to these controls.

[0023] Regenerative motoring control refers to the control in which, when the vehicle is running and the accelerator is off (the state where the accelerator opening is less than or equal to a predetermined opening, or the state where the driver's required torque or driver's required output is less than or equal to a predetermined threshold), the regenerative power of motor 3 is supplied to generator 4, and engine 2 is motored (idled) at a predetermined target rotational speed. The implementation conditions of regenerative motoring control include at least that vehicle 1 is running and the accelerator is off. In addition to this, conditions such as the state of charge of battery 5, the presence or absence of battery failure, battery temperature, brake opening, braking force required for vehicle 1, the operating state of a friction brake device (not shown), and road surface conditions may be included in the implementation conditions of regenerative motoring control. When an accelerator-on operation is performed during regenerative motoring control, the regenerative motoring control stops, and motor 3 enters a state of driving the wheels.

[0024] Each of continuous motoring control, first power generation control, and second power generation control is a control that is implemented in place of regenerative motoring control when the regenerative motoring control is stopped by an accelerator-on operation. Any one of these controls is selected and implemented based on the required power generation amount or driver's required output when the accelerator is on. In this embodiment, the cases where continuous motoring control, first power generation control, and second power generation control are each implemented will be described, but first power generation control and second power generation control can be omitted.

[0025] Table 1 summarizes the typical implementation conditions and control contents for regenerative motoring control, continuous motoring control, first power generation control, and second power generation control. Continuous motoring control is selected when the required power generation amount is relatively small. On the other hand, first power generation control and second power generation control are selected when the required power generation amount is relatively large. Also, first power generation control is selected when the driver's required output is relatively small. In contrast, second power generation control is selected when the driver's required output is relatively large.

[0026]

Table 1

[0027] Continuous motoring control is control that supplies the power of the battery 5 to the generator 4 without performing regenerative braking on the motor 3 and continues the motoring of the engine 2. In other words, continuous motoring control is control that idles the engine 2 while the motor 3 is driving the wheels (in the state of EV running). That is, continuous motoring control is control that wastes the power of the battery 5 with the generator 4 regardless of the running of the vehicle 1, and can be said to be control with a demerit in terms of electricity cost. However, by continuing the motoring instead of immediately starting the firing of the engine 2 at the end of the regenerative motoring control, the change in the rotational speed of the engine 2 can be easily suppressed, and the merit that the driving feeling can be easily improved is obtained.

[0028] The rotational speed of the engine 2 during continuous motoring control is preferably fixed to the target rotational speed at that time (for example, when the accelerator pedal is depressed). Thereby, since the rotational speed of the engine 2 becomes constant before and after the end of the regenerative motoring control and the operating sound (noise) and vibration of the engine 2 do not change, the driver will not feel uncomfortable. When the vehicle speed changes during continuous motoring control, the target rotational speed of the engine 2 may be set based on the characteristics shown by the solid line graph in FIG. 3. That is, similar to during regenerative motoring control, the target rotational speed during continuous motoring control may be set.

[0029] Incidentally, when the target rotational speed of the regenerative motor control is extremely high, if the target rotational speed is carried over as the rotational speed of engine 2 during continuous motor control, there is a risk that the power of battery 5 will be excessively consumed. Therefore, the rotational speed of engine 2 in continuous motor control may be fixed at a predetermined speed (for example, a rotational speed slightly lower than the target rotational speed) different from the target rotational speed to such an extent that the driving feeling is not impaired. In this case, within the range sandwiched between the solid line graph and the broken line graph in FIG. 3, the predetermined speed may be set according to the vehicle speed. The closer the predetermined speed set here is to the solid line graph in FIG. 3, the better the driving feeling becomes, and the closer it is to the broken line graph in FIG. 3, the more the power consumption decreases.

[0030] The start conditions for continuous motor control are exemplified below. In this embodiment, continuous motor control is started when at least both condition 1 and condition 2 are satisfied. Thereafter, if condition 2 is satisfied and an accelerator-on operation is being performed, continuous motor control can be continued. Condition 3 is an additional condition for confirming that there is sufficient battery power. Condition 1. It is the end time of regenerative motor control by an accelerator-on operation. Condition 2. The required power generation amount is less than the threshold value. Condition 3. The charging rate of battery 5 is equal to or higher than a predetermined first charging rate

[0031] The “required power generation amount” included in the above condition 2 will be described in detail. The required power generation amount is the amount of electric power required by various electrical components (in-vehicle electrical components) mounted on the vehicle 1 or the driver for the vehicle 1, and means the amount of electric power to be generated by the generator 4. The required power generation amount is calculated at least according to the driving state of the vehicle 1. For example, it is calculated based on the vehicle speed and the operating states of in-vehicle electrical components (such as an air conditioner, a multimedia device, various electronic control devices, and electrical appliances connected to an external power supply outlet). The required power generation amount increases as the vehicle speed increases and as the power consumption of the in-vehicle electrical components increases. Note that the required power generation amount may be calculated in consideration of the operating state (such as the charge rate and soundness) of the battery 5. For example, when the charge rate or soundness of the battery 5 is low, the required power generation amount may be increased.

[0032] The “threshold value” included in the above condition 2 will be described in detail. The threshold value is an index value for determining whether the operating state of the engine 2 that drives the generator 4 becomes a highly efficient operating state (equal to or higher than a predetermined thermal efficiency set in advance) when generating electric power corresponding to the required power generation amount by the generator 4. In other words, the threshold value is the minimum value of the required power generation amount that allows the engine 2 to operate with high efficiency. If the generator 4 generates electric power with a required power generation amount equal to or higher than the threshold value, the thermal efficiency of the engine 2 will be equal to or higher than the predetermined efficiency, and it will be in a highly efficient operating state. On the other hand, if the generator 4 generates electric power with a required power generation amount less than the threshold value, the thermal efficiency of the engine 2 will be less than the predetermined efficiency, and it will be in a low-efficiency operating state. Therefore, in this embodiment, when the required power generation amount is less than the threshold value, the motoring of the engine 2 is continued (that is, “firing of the engine 2 and power generation by the generator 4” is suspended), thereby preventing a decrease in fuel efficiency.

[0033] FIG. 4 is a graph illustrating the relationship between the rotational speed of the engine 2 and the threshold value of the required power generation amount. The threshold value is set based on at least the rotational speed of the engine 2. The graph showing the change in the threshold value with respect to the rotational speed of the engine 2 can be represented by a curve (high-efficiency power generation line) as shown by the solid line in FIG. 4. Alternatively, by simplifying the shape of this curve, it is also possible to represent the change in the threshold value with respect to the rotational speed of the engine 2 by a broken line or a straight line. If such a relationship is defined in advance, the threshold value at that time can be calculated according to the rotational speed of the engine 2.

[0034] The curve of the threshold value shown in FIG. 4 will be described in detail. FIG. 5 is a graph illustrating the output characteristics (relationship between rotational speed and torque) of the engine 2. The thick solid line in FIG. 5 shows the relationship between the rotational speed of the engine 2 and the maximum torque. The thin solid line in FIG. 5 is a curve connecting the operating points where the same thermal efficiency (fuel consumption) can be obtained at a constant thermal efficiency interval, and is an isothermal line for the level of thermal efficiency. Also, the broken-line graph in FIG. 5 is a line showing the lower limit of torque of the operating points where high efficiency (predetermined thermal efficiency) is achieved. The shape of the broken-line graph in FIG. 5 is reflected in the shape of the solid-line graph in FIG. 4.

[0035] The output (work rate) of the engine 2 at each operating point located on the broken line in FIG. 5 is expressed by the product of the torque and the rotational speed of that operating point. Also, the maximum power generation amount of the generator 4 is generally proportional to the output of the engine 2. Therefore, by calculating the product of the torque, the rotational speed, and a predetermined coefficient at each operating point located on the broken line in FIG. 5 and plotting the relationship between that value and the rotational speed of the engine 2 on the graph, the solid-line graph in FIG. 4 can be obtained. Incidentally, when it is desired to operate the engine 2 with a higher thermal efficiency, a broken-line graph corresponding to that thermal efficiency can be drawn in FIG. 5, and a solid-line graph (high-efficiency power generation line) corresponding to that broken-line graph can be obtained.

[0036] The first power generation control is a control for generating power in the generator 4 while firing the engine 2 while maintaining the rotational speed of the engine 2. Preferably, while fixing the rotational speed of the engine 2 to the target rotational speed at that time, power is generated in the generator 4 while firing the engine 2. In other words, the first power generation control is a control for suspending the setting of the target rotational speed based on the broken line graph in FIG. 3 and maintaining the target rotational speed at that time when the regenerative motor control is stopped by an accelerator-on operation. Thereby, sudden changes in the operating sound and vibration of the engine 2 before and after the accelerator is turned on are suppressed, and the driving feeling is improved. However, when the continuous motor control has been implemented before the start of the first power generation control and the rotational speed of the engine 2 has been fixed to a predetermined speed different from the target rotational speed, the rotational speed of the engine 2 may also be continuously fixed to the predetermined speed even in the first power generation control.

[0037] In the first power generation control, the torque of the engine 2 can be set to be larger as the accelerator opening (or the driver required output corresponding thereto) is larger. On the other hand, the rotational speed of the engine 2 is stably maintained without sudden changes. The rotational speed of the engine 2 can be changed by adjusting the load of the generator 4 on the engine 2 (the power that the generator 4 converts into electric power). Thus, the control device 10 can function to maintain the rotational speed of the engine 2 while increasing the torque of the engine 2 as the accelerator opening is larger during the first power generation control.

[0038] The start conditions of the first power generation control are exemplified below. In this embodiment, the first power generation control is started when condition 1 or condition 4 is satisfied and condition 5 is satisfied. Thereafter, if condition 5 is satisfied and an accelerator-on operation is being performed, the first power generation control can be continued. Condition 6 is an additional condition for implementing the first power generation control only when the driver required output is relatively small. Condition 7 is an additional condition for confirming that there is little remaining power in the battery power, for example, "the second charge rate ≤ the first charge rate". Condition 4. The continuous motor control is being implemented. Condition 5. The required power generation amount is equal to or greater than the threshold value. Condition 6. The driver required output is equal to or less than a predetermined value. Condition 7. The charging rate of the battery 5 is less than a predetermined second charging rate.

[0039] The second power generation control is a control that is implemented instead of the first power generation control when the above-mentioned condition 6 is not satisfied (when the driver required output exceeds the predetermined value), on the premise that the above-mentioned condition 6 is included in the implementation conditions of the first power generation control, and is a control for increasing the rotational speed of the engine 2. In the second power generation control, the fixing of the rotational speed of the engine 2 is released, and the engine 2 can operate at a rotational speed higher than the target rotational speed (or a predetermined speed). In other words, the second power generation control can be said to be a control for restarting the setting of the target rotational speed based on the broken-line graph in FIG. 3 when the driver deeply depresses the accelerator pedal.

[0040] The implementation conditions of the second power generation control are exemplified below. When any one of conditions 1, 4, and 8 is satisfied and condition 9 is satisfied, the second power generation control is started. Thereafter, if condition 9 is satisfied and the accelerator-on operation is being performed, the first power generation control can be continued. Condition 10 is an additional condition for confirming that there is no remaining power in the battery power, and is, for example, "third charging rate ≤ second charging rate". Condition 8. The first power generation control is being implemented. Condition 9. The driver required output exceeds the predetermined value. Condition 10. The charging rate of the battery 5 is less than a predetermined third charging rate.

[0041] In the first power generation control, the rotational speed of the engine 2 is fixed at the target rotational speed (or a predetermined speed). In contrast, in the second power generation control, the operating state of the engine 2 is controlled so that the rotational speed of the engine 2 increases to a value higher than the target rotational speed (or a predetermined speed). The rotational speed of the engine 2 is controlled, for example, according to the vehicle speed. As a result, as the vehicle speed increases with an increase in the accelerator opening, the operating sound and vibration of the engine 2 increase, and a natural and intuitive driving feeling that is easy to understand is realized.

[0042] [3. Flowchart] FIG. 6 is a flowchart illustrating the control flow implemented by the control device 10. The control shown in this flowchart is repeatedly executed at a predetermined cycle inside the control device 10 when, for example, the power switch of the vehicle 1 (not shown) is on and the vehicle is drivable (in the READY state). Steps A1 to A3 mainly correspond to regenerative motor modeling control, and steps A4 to A7 mainly correspond to continuous motor modeling control. Also, steps A8 to A11 mainly correspond to first power generation control, and step A12 corresponds to second power generation control.

[0043] In step A1, it is determined whether the execution condition of the regenerative motor modeling control is satisfied. If this condition is satisfied, the control proceeds to step A2. On the other hand, if the condition in step A1 is not satisfied, the control for this cycle ends. In step A2, based on characteristics such as the solid line graph in FIG. 3, the target rotational speed of the engine 2 is set according to the vehicle speed. Here, the higher the vehicle speed, the higher the target rotational speed of the engine 2 is set. That is, since the higher the vehicle speed, the greater the regenerative power generated by the motor 3, the target rotational speed of the engine 2 driven by the generator 4 is set high so that the generator 4 consumes electric power of a magnitude corresponding to that regenerative power.

[0044] In step A3, the regenerative motor modeling control is implemented based on the target rotational speed set in step A2. That is, the regenerative power of the motor 3 is supplied to the generator 4, and the motor 3 is modeled (idled) by the generator 4 so that the rotational speed of the engine 2 becomes the target rotational speed. In step A4, it is determined whether the accelerator is on. Here, if it is determined that the accelerator is not on, the control for this cycle ends. In subsequent cycles, the regenerative motor modeling control continues as long as the execution condition of the regenerative motor modeling control is satisfied. On the other hand, if it is determined in step A4 that the accelerator is on, the regenerative motor modeling control ends and the control proceeds to step A5.

[0045] In step A5, the required power generation amount and the threshold value are calculated. The required power generation amount is calculated based on, for example, the vehicle speed and the operating state of in-vehicle electrical components. The value of the required power generation amount is calculated to be a larger value as the vehicle speed is higher, for example. Alternatively, the required power generation amount is calculated to be a larger value as the power consumption of the in-vehicle electrical components is larger. The threshold value is calculated as a value corresponding to the rotational speed of the engine 2 at that time based on, for example, the characteristics as shown in FIG. 4.

[0046]

[0045] In step A6, it is determined whether or not the required power generation amount calculated in step A5 is less than the threshold value. Here, when the required power generation amount is less than the threshold value, the control proceeds to step A7, and continuous motor driving control is performed instead of regenerative motor driving control. In the continuous motor driving control, the generator 4 is controlled to a power running state with the power of the battery 5, and the engine 2 is driven to idle. At this time, the motor 3 is also controlled to a power running state so as to generate a driving force corresponding to the accelerator opening degree, and the wheels are driven.

[0047] The rotational speed of the engine 2 during the continuous motor driving control is set according to the vehicle speed at least within the range sandwiched between the solid line graph and the broken line graph in FIG. 3. Thereby, when shifting from the regenerative motor driving control to the continuous motor driving control, the change in the rotational speed of the engine 2 becomes small, and the sense of discomfort given to the driver becomes small. Further, preferably, the rotational speed of the engine 2 is fixed to the target rotational speed during the immediately preceding regenerative motor driving control. Thereby, since the rotational speed of the engine 2 becomes constant, the driver is not given a sense of discomfort.

[0048] In step A6, when the required power generation amount is equal to or greater than the threshold value, it is determined that the engine 2 can operate with high efficiency, and the control proceeds to step A8. In step A8, based on characteristics such as those shown in FIG. 2 for example, the driver required output is calculated based on the accelerator opening. The larger the accelerator opening, the larger the value set for the driver required output. In the subsequent step A9, it is determined whether the driver required output calculated in step A8 is less than or equal to a predetermined value. If this condition is satisfied, the control proceeds to step A10.

[0049] In step A10, while fixing the rotational speed of the engine 2 at the target rotational speed at that time, the first power generation control for generating power in the generator 4 while firing the engine 2 is performed. As a result, the operating state of the engine 2 shifts from the motoring state to the firing state. The torque of the engine 2 is set according to the driver required output. On the other hand, the target rotational speed of the engine 2 in the firing state is maintained at the same speed as the target rotational speed of the engine 2 in the motoring state. Therefore, the operating sound and vibration of the engine 2 hardly change, and the driving feeling is improved.

[0050] In the subsequent step A11, it is determined whether the accelerator is off. Here, if it is determined that the accelerator is not off, the control returns to step A8, and the driver required output is calculated again. Thereafter, as long as the driver required output is less than or equal to the predetermined value, the first power generation control is continued. Also, in step A11, if it is determined that the accelerator is off, the control for this cycle ends. In subsequent cycles, the regenerative motoring control is restarted as long as the conditions for implementing the regenerative motoring control are satisfied.

[0051] If it is determined in step A9 that the driver request output exceeds a predetermined value, the control proceeds to step A12. In step A12, instead of the first power generation control, the second power generation control is implemented, and the rotational speed of engine 2 is changed to a rotational speed higher than the target rotational speed at that time. The torque of engine 2 is set according to the driver request output. During the second power generation control, the output of engine 2 becomes larger compared to that during the first power generation control, and the generated power at generator 4 also increases.

[0052] In the subsequent step A11, it is determined whether the accelerator is off. Here, if it is determined that the accelerator is not off, the control returns to step A8, and the driver request output is calculated again. Thereafter, the second power generation control is continued as long as the driver request output exceeds the predetermined value. Also, in step A11, if it is determined that the accelerator is off, the control for this cycle ends. After the next cycle, the regenerative motor modeling control is restarted as long as the implementation conditions for the regenerative motor modeling control are satisfied.

[0053] [4. Operation] FIG. 7 is a time chart illustrating the operation of the control implemented by the control device 10. Here, it is assumed that the regenerative motor modeling control is being implemented before time t1 and the accelerator is off. When the accelerator pedal is slightly depressed at time t1 to turn the accelerator on, the regenerative motor modeling control stops and the continuous motor modeling control starts. The state of motor 3 changes from the regenerative power generation (regenerative braking) state to the power running state with time t1 as the boundary. On the other hand, the state of engine 2 remains in the motor modeling state even after time t1. At this time, the rotational speed of engine 2 is fixed, for example, at the target rotational speed during the regenerative motor modeling control. Since the power for generator 4 to idle engine 2 is taken out from battery 5, the output of battery 5 slightly increases with time t1 as the boundary.

[0054] Note that if continuous motoring control is not performed, when the firing of engine 2 starts at time t1 and the target rotational speed can be set relatively low, the actual rotational speed of engine 2 will decrease as shown by the dashed line in FIG. 7. However, in this embodiment, since continuous motoring control is performed without starting the firing, it is easy to keep the rotational speed of engine 2 substantially constant without changing it around time t1. Also, if continuous motoring control is not performed, as shown by the two-dot chain line in FIG. 7, when engine 2 starts, its torque can become a slightly large value at time t1. On the other hand, in this embodiment, since engine 2 does not start at time t1, the torque of engine 2 does not change around time t1 and becomes a constant value (a negative value corresponding to the friction torque).

[0055] When the accelerator pedal is depressed further at time t2, as the accelerator opening increases, the driver required output increases. As a result, the output of motor 3 increases, and as the vehicle speed rises, the required power generation amount increases. Also, as shown by the dotted line in FIG. 7, a threshold value is calculated according to the rotational speed of engine 2 being motored. As long as the required power generation amount is less than the threshold value, the continuous motoring control is maintained. The reason is that even if engine 2 is started when the required power generation amount is less than the threshold value, the operating state of engine 2 will not reach a highly efficient (equal to or higher than a predetermined thermal efficiency set in advance) operating state.

[0056] When the required power generation amount becomes equal to or greater than the threshold value at time t3, the first power generation control is performed instead of the continuous motoring control. The state of engine 2 changes from the motoring state to the firing state with time t3 as the boundary. On the other hand, in the first power generation control, the target rotational speed of engine 2 is maintained at the target rotational speed before time t3, and the actual rotational speed of engine 2 also becomes a constant value. Therefore, the operating noise and vibration of engine 2 hardly change, and the driving feeling is improved.

[0057] In the first power generation control, the torque of engine 2 is set to be greater as the accelerator opening is larger. On the other hand, since the target rotational speed of engine 2 is maintained constant even after time t3, as the torque increases, the output of engine 2 (the product of the rotational speed and torque) increases, and the generated power of generator 4 also gradually increases. As a result, the power taken out from battery 5 decreases, and the output of battery 5 decreases as the torque of engine 2 increases within the positive range.

[0058] When the driver required output exceeds a predetermined value at time t4, the second power generation control is implemented instead of the first power generation control. In the second power generation control, the setting of the target rotational speed based on the broken line graph in FIG. 3 is restarted. As a result, the rotational speed of engine 2 increases, and the torque of engine 2 and the generated power of generator 4 also further increase. Therefore, as the accelerator opening is increased, the operating sound and vibration of engine 2 become larger, and a natural and intuitive driving feeling that is easy to understand is realized. Also, the power taken out from battery 5 further decreases, and the output of battery 5 also further decreases. After that, when the increase in the accelerator opening stops at time t5, the increase in the rotational speed and torque of engine 2 also stops, and the output of battery 5 becomes constant.

[0059] Note that point P1 in FIG. 4 represents the rotational speed of engine 2 and the required generated power at time t1 in FIG. 7, and is a state point representing the state of vehicle 1 at the start of the continuous motoring control. Point P1 is located within the motoring continuation region, which is a region below the graph of the threshold value (high efficiency power generation line). In the continuous motoring control, for example, the rotational speed of engine 2 is fixed to the target rotational speed (or a predetermined speed). As a result, the state point of vehicle 1 moves straight upward from point P1 as the required generated power increases, and reaches point P2 when the required generated power becomes equal to the threshold value.

[0060] Point P2 represents the rotational speed of engine 2 and the required power generation amount at time t3 in FIG. 7, and represents the state of vehicle 1 at the start of the first power generation control. In the first power generation control, the rotational speed of engine 2 is fixed at the target rotational speed (or a predetermined speed). Therefore, the state point of vehicle 1 enters the firing power generation region, which is a region above the graph of the threshold value (high-efficiency power generation line). As the required power generation amount increases, the state point of vehicle 1 moves further vertically upward from point P2 and reaches point P3 when the driver required output becomes equal to the predetermined value.

[0061] Point P3 represents the rotational speed of engine 2 and the required power generation amount at time t4 in FIG. 7, and represents the state of vehicle 1 at the start of the second power generation control. In the second power generation control, the rotational speed of engine 2 can rise higher than the target rotational speed (or a predetermined speed). Therefore, as the rotational speed of engine 2 rises, the state point of vehicle 1 moves rightward in FIG. 7, and as the required power generation amount increases, it moves upward in FIG. 7.

[0062] [5. Effects] (1) The hybrid vehicle 1 of this embodiment includes an engine 2, a motor 3 that performs driving of wheels and regenerative braking, a generator 4 that performs power generation by the driving force of engine 2 and driving of engine 2, and a battery 5 connected to motor 3 and generator 4. Further, it includes a control device 10 that implements regenerative motoring control for supplying the regenerative power of motor 3 to generator 4 and motoring engine 2 at a predetermined target rotational speed when the vehicle is running and the accelerator is off. The control device 10 calculates the required power generation amount according to the running state, and if the required power generation amount is less than the threshold value when stopping the regenerative motoring control by an accelerator-on operation, it implements continuous motoring control. Continuous motoring control is control for supplying the power of battery 5 to generator 4 and continuing the motoring of engine 2.

[0063] By implementing such control, it is possible to reduce the change in the rotational speed of the engine 2 immediately after the end of the regenerative motoring control, and suppress sudden changes in the operating sound (noise) and vibration of the engine 2. That is, by continuing motoring instead of immediately starting the firing of the engine 2 at the end of the regenerative motoring control, the change in the rotational speed of the engine 2 can be easily suppressed. Therefore, the drive feeling during acceleration after the regenerative motoring control can be improved.

[0064] Note that the continuous motoring control is implemented only in a situation where the required power generation amount is less than the threshold value. That is, the motoring of the engine 2 will continue only when it is expected that the remaining power of the battery 5 (the power stored in the battery 5) will not decrease significantly. Therefore, the power for running the vehicle 1 will not be insufficient during the implementation of the continuous motoring control, and a good drive feeling can be provided.

[0065] (2) When performing the continuous motoring control, the control device 10 described above can continue the motoring of the engine 2 while fixing the rotational speed of the engine 2 at the target rotational speed at that time. By thus fixing the rotational speed of the engine 2 at the target rotational speed, the fluctuation in the rotational speed of the engine 2 after the end of the regenerative motoring control can be suppressed. That is, when shifting from the regenerative motoring control to the continuous motoring control, since the rotational speed of the engine 2 does not change, the change in the operating sound and vibration of the engine 2 can be suppressed. Therefore, the drive feeling during acceleration from the regenerative motoring control can be improved.

[0066] (3) When the required power generation amount is equal to or greater than the threshold value, the control device 10 described above can perform first power generation control to generate power in the generator 4 while maintaining the rotational speed of the engine 2 and firing the engine 2. By implementing such control, power generation by the generator 4 can be performed while suppressing changes in the operating sound and vibration of the engine 2. Therefore, it is possible to prevent the power of the battery 5 from decreasing while improving the driving feeling. In addition, since the power of the battery 5 is secured, there is no risk of insufficient power for driving the motor 3, and a good acceleration feeling can be realized.

[0067] (4) When performing the first power generation control, the control device 10 described above can perform control to maintain the rotational speed of the engine 2 while increasing the torque of the engine 2 as the accelerator opening degree increases. For example, the driver required output is set based on characteristics as shown in FIG. 2, and the torque of the engine 2 is controlled based on this driver required output. By such control, while increasing the output of the engine 2, changes in the operating sound and vibration of the engine 2 can be suppressed, and the driving feeling can be further improved. In addition, by increasing the output of the engine 2, the power generation amount of the generator 4 can be increased. Therefore, the power for driving the motor 3 can be increased, and a good acceleration feeling can be realized.

[0068] (5) When performing the first power generation control, the control device 10 described above can perform second power generation control to increase the rotational speed of the engine 2 when the driver required output exceeds a predetermined value. For example, when the driver required output increases as after time t4 in FIG. 7, by increasing the rotational speed of the engine 2, a natural behavior of the engine 2 can be realized without a sense of discomfort, and the driving feeling can be improved. In addition, the generated power of the generator 4 can be increased to improve the acceleration performance of the vehicle 1, and the driving feeling can be improved.

[0069] (6) The above required power generation amount can be calculated based on the vehicle speed or the operating state of in-vehicle electrical components. Through such control, the power generation amounts required by various electrical components (in-vehicle electrical components) and the driver for the vehicle 1 can be accurately calculated. Therefore, the timing for shifting the engine 2 from the motoring state to the firing state can be appropriately determined, and a good acceleration feeling can be realized while improving the driving feeling. Also, the above threshold value can be set based on the rotational speed of the engine 2. Through such control, it can be accurately determined whether the engine 2 is in a state where it can operate with high efficiency. Therefore, the fuel consumption during power generation can be improved while improving the driving feeling.

[0070] [6. Others] The above embodiments are merely examples, and there is no intention to exclude various modifications and applications of technologies not explicitly stated in this embodiment. Each configuration of this embodiment can be variously modified and implemented without departing from their gist. Also, each configuration of this embodiment can be selectively used as needed, or can be appropriately combined.

[0071] For example, in the above embodiment, the control device 10 that implements the regenerative motoring control, the continuous motoring control, the first power generation control, and the second power generation control is exemplified, but the first power generation control and the second power generation control can be omitted. At least when stopping the regenerative motoring control during an accelerator-on operation, by determining whether to implement the continuous motoring control using the required power generation amount and the threshold value, the same operational effects as the above-described embodiment can be obtained.

[0072] Note that the rotational speed of the engine 2 during continuous motoring control may be fixed at the target rotational speed, or may be fixed at a predetermined speed other than the target rotational speed (for example, a rotational speed slightly lower than the target rotational speed). Also, within a range where the driving feeling is not impaired, the rotational speed of the engine 2 may be treated as a variable value without being fixed. For example, the rotational speed of the engine 2 may be set so as to fall within a predetermined speed range including the target rotational speed. The same applies to the rotational speed of the engine 2 during the first power generation control, which may be fixed at the target rotational speed, may be fixed at a predetermined speed other than the target rotational speed, or may be a variable value.

Industrial Applicability

[0073] This case is applicable to the manufacturing industry of hybrid vehicles and is also applicable to the manufacturing industry of control devices for hybrid vehicles.

Explanation of Signs

[0074] 1 Vehicle (hybrid vehicle) 2 Engine 3 Motor 4 Generator 5 Battery 6 Clutch 7 Accelerator opening sensor 8 Brake opening sensor 9 Vehicle speed sensor 10 Control device

Claims

1. An engine, a motor that drives and regeneratively brakes wheels, a generator that generates electricity by the driving force of the engine and drives the engine, a battery connected to the motor and the generator, and a control device that performs regenerative motoring control for supplying the regenerative power of the motor to the generator and motoring the engine at a predetermined target rotational speed when the vehicle is running and the accelerator is off. The control device calculates a required power generation amount according to the running state, and when the regenerative motoring control is stopped by an accelerator-on operation and the required power generation amount is less than a threshold value, the control device performs continuous motoring control for supplying the power of the battery to the generator and continuing the motoring of the engine. The control device calculates the required power generation amount based on the vehicle speed or the operating state of in-vehicle electrical components, and sets the threshold value based on the rotational speed of the engine. A hybrid vehicle, characterized by the above.

2. When performing the continuous motoring control, the control device continues the motoring of the engine while fixing the rotational speed of the engine at the target rotational speed at that time. The hybrid vehicle according to claim 1, characterized by the above.

3. When the required power generation amount is greater than or equal to the threshold value, the control device performs first power generation control for generating electricity in the generator while firing the engine while maintaining the rotational speed of the engine. The hybrid vehicle according to claim 1 or 2, characterized by the above.

4. When performing the first power generation control, the control device maintains the rotational speed of the engine while increasing the torque of the engine as the accelerator opening increases. The hybrid vehicle according to claim 3, characterized by the above.

5. When performing the first power generation control, when the driver required output exceeds a predetermined value, the control device performs second power generation control for increasing the rotational speed of the engine. The hybrid vehicle according to claim 3 or 4, characterized by the above.

6. (Deleted)

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