JP2014111413A - Travel control device of hybrid electric automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a travel control device of a hybrid electric automobile capable of preventing degradation in durability of a battery due to enlargement of a control range of an SOC (State Of Charge), and improving fuel economy by effectively utilizing an enlarged region of the control range.SOLUTION: When a descending road is predicted ahead of a vehicle 1, a control range of an SOC of a battery is enlarged at a point before the descending road. While the vehicle is traveling until it reaches the descending road, the SOC of the battery is lowered to a lower limit SOCloex of the enlarged control range through power running control of a motor. While the vehicle is traveling the descending road thereafter, the SOC is raised to an upper limit SOCupex of the enlarged control range through regenerative control of the motor. Within the enlarged region on the side of the lower limit, a current to be fed to the motor is suppressed. Within an expansion domain on the side of the upper limit, a current to be generated by the motor is suppressed. Thus, the raising and lowering of the SOC are moderated in order to prevent deterioration of the battery.

Description

  The present invention relates to a travel control device for a hybrid electric vehicle, and more particularly to a travel control device for a hybrid electric vehicle equipped with an engine and a motor as a driving power source.

In this type of hybrid electric vehicle, at the time of deceleration or traveling on a downhill road, the motor is regeneratively controlled to collect the kinetic energy of the vehicle as generated power and charge the battery. Also, during acceleration and traveling on an uphill road, the motor is controlled by the power discharged from the battery to generate driving force, thereby reducing the burden on the engine and reducing fuel consumption.
When the battery is fully charged, the motor cannot be regeneratively controlled, and when the battery is overdischarged, the motor cannot be controlled for power running. Excessive charging / discharging of the battery also reduces durability. For this reason, in general, by controlling the battery within a predetermined state of charge (SOC) range, it is possible to always secure a room for regenerative control of the motor and power running control, and excessive charging / discharging of the battery. It is preventing.

  Accordingly, for example, when the SOC of the battery reaches the upper limit of the control range by regenerative control of the motor while traveling on a downhill road, the regenerative control of the motor must be stopped even if the downhill road continues. Therefore, after that, the kinetic energy of the vehicle cannot be recovered as electric power, and is wasted as heat energy due to the operation of the engine brake or service brake.

As a countermeasure against such a problem, for example, the technique of Patent Document 1 has been proposed. In the technique of Patent Document 1, the SOC control range is expanded when a downhill road is predicted ahead of a running vehicle, and the battery SOC is expanded by motor power running control before reaching the downhill road. It is lowered to the lower limit of the later control range. Further, when the vehicle travels downhill thereafter, the SOC of the battery is increased to the upper limit of the expanded control range by regenerative control of the motor.
Therefore, during traveling downhill, extra power is discharged from the battery and used to drive the motor, thereby reducing the burden on the engine and saving fuel consumption. Further, since the regenerative electric power of the motor is charged to the battery during traveling on the downhill road, fuel consumption can be reduced by using the electric power for driving the motor later.

JP 2005-160269 A

ここに、αはバッテリの特性によって定まる係数である。 However, the SOC control range is originally set based on the knowledge of battery protection, and if the control range is expanded every downhill as in the technique of Patent Document 1, the durability of the battery due to excessive charging and discharging. There is a concern that will decrease.
Even if the SOC control range is expanded, the expanded area may not be used effectively due to another restriction. That is, there is a thermal limitation on the current when the battery is charged / discharged, and the charge / discharge current exceeding the limit is consumed for the temperature rise of the battery and causes damage. Therefore, based on the current I and charge / discharge time Δt of the battery, an index H corresponding to the heat generation amount is calculated from the following equation (1), and when the index H reaches a preset upper limit allowable value, Measures are taken to limit the discharge current.

Here, α is a coefficient determined by the characteristics of the battery.

However, since the expansion of the SOC control range leads to an extension of the charge / discharge time, the power running control and regenerative control of the motor are interrupted due to the limitation of the charge / discharge current based on the equation (1). For this reason, the area in which the control range is expanded cannot be used effectively, and as a result, the operational effect due to the expansion of the SOC control range cannot be obtained.
The present invention has been made to solve such a problem, and the object of the present invention is to prevent deterioration of the battery durability due to the expansion of the SOC control range before the control range. An object of the present invention is to provide a travel control device for a hybrid electric vehicle that can effectively improve the fuel consumption by effectively using an enlarged region.

  In order to achieve the above object, the invention according to claim 1 is equipped with an engine and a motor as a driving power source, travels by the driving force of the engine and the driving power of the motor, and regeneratively controls the motor on the downhill road. Driving control means for controlling the operating state of the engine and the motor during traveling of the vehicle while keeping the charging rate of the battery in a preset control range in the traveling control device of the hybrid electric vehicle for charging the generated power to the battery; When the downhill road prediction means for predicting the downhill road ahead of the vehicle and the downhill road ahead is predicted by the downhill road prediction means, the control range of the charging rate is expanded at a point before the downhill road. Control range expansion means, and when the operation control means expands the control range of the charging rate by the control range expansion means, the motor until the vehicle reaches the downhill road. Together reduced to powering controlled by the enlarged area of the lower side of the control range of the charging rate of the battery, in the enlarged region is to suppress the current supplied to the motor.

  According to a second aspect of the present invention, in the first aspect, when the operation control means reaches the downhill road and is traveling on the downhill road, the charge rate of the battery is set to the upper limit side of the control range by the regeneration control of the motor. While increasing to the inside of an expansion area, the electric power generated by a motor is suppressed in an expansion area.

As described above, according to the traveling control apparatus for a hybrid electric vehicle according to the first aspect of the present invention, when a downhill road is predicted in front of the vehicle, the control range of the charging rate of the battery at a point before the downhill road. The battery charging rate is reduced to the lower limit side of the control range by the power running control of the motor until the vehicle reaches the downhill road, and the current supplied to the motor is suppressed in the enlarged range. I made it.
Accordingly, during traveling until the vehicle reaches the downhill road, the electric power discharged from the battery is expended to drive the motor, thereby reducing the burden on the engine and reducing fuel consumption. And since the charging rate of a battery falls gradually within the expansion area on the lower limit side, it is possible to minimize the deterioration of the battery due to the control of the charging rate exceeding the normal control range. In addition, since the current when the battery is discharged is reduced, it is possible to avoid a situation where the powering control of the motor is interrupted in order to prevent damage caused by the heat generated by the battery, and to extend the control range to reduce fuel consumption. It can be used effectively.

According to the traveling control apparatus for a hybrid electric vehicle of the invention of claim 2, in addition to claim 1, when the vehicle is traveling on a downhill road, the battery charging rate is set to the upper limit side of the control range by regenerative control of the motor. In the enlarged region, the current generated by the motor is suppressed in the enlarged region.
Accordingly, when traveling on a downhill road, fuel consumption can be reduced by charging the battery with extra power by regenerative control of the motor and using the power for driving the motor later. And since the charging rate of a battery increases gently in the expansion area | region on the upper limit side, the deterioration of the battery resulting from control of the charging rate exceeding the normal control range can be suppressed to the minimum. In addition, since the current during charging of the battery is reduced, it is possible to avoid a situation where the regenerative control of the motor is interrupted in order to prevent damage due to the heat generation of the battery, and the expansion range of the control range can be saved to reduce fuel consumption. It can be used effectively.

1 is an overall configuration diagram showing a hybrid truck on which a travel control device of an embodiment is mounted. It is a flowchart which shows the downhill road corresponding motor control routine which vehicle ECU performs. It is a time chart which shows the execution situation of motor control when a descending slope is predicted.

Hereinafter, an embodiment in which the present invention is embodied in a travel control device for a hybrid truck will be described.
FIG. 1 is an overall configuration diagram showing a hybrid truck on which the travel control device of this embodiment is mounted.
The hybrid truck 1 is configured as a so-called parallel hybrid electric vehicle, and may be referred to as a vehicle in the following description. A vehicle 1 is equipped with a diesel engine (hereinafter referred to as an engine) 2 as a driving power source and a motor 3 that can also operate as a generator such as a permanent magnet synchronous motor. A clutch 4 is connected to the output shaft of the engine 1, and an input side of the automatic transmission 5 is connected to the clutch 4 via a rotating shaft of the motor 3. A differential device 7 is connected to the output side of the automatic transmission 5 via a propeller shaft 6, and left and right drive wheels 9 are connected to the differential device 7 via a drive shaft 8.

  The automatic transmission 5 is based on a general manual transmission and automates the engagement / disengagement operation of the clutch 4 and the switching operation of the shift speed. In this embodiment, the automatic transmission 5 has a forward speed 6-speed reverse-speed 1 speed. ing. Of course, the configuration of the transmission 5 is not limited to this, and can be arbitrarily changed. For example, the transmission 5 may be embodied as a manual transmission, or a so-called dual clutch automatic transmission having two power transmission systems. It may be embodied as a machine.

  A battery 11 is connected to the motor 3 via an inverter 10. The DC power stored in the battery 11 is converted into AC power by the inverter 10 and supplied to the motor 3 (power running control), and the driving force generated by the motor 3 is transmitted to the drive wheels 9 after being shifted by the automatic transmission 5. The vehicle 1 is made to travel. Further, for example, when the vehicle 1 is decelerated or regeneratively traveling on a downhill road, the motor 3 operates as a generator by reverse driving from the drive wheel 9 side (regenerative control). The negative driving force generated by the motor 3 is transmitted to the driving wheel 9 side as a braking force, and the AC power generated by the motor 3 is converted into DC power by the inverter 10 and charged to the battery 11.

  The driving force generated by the motor 3 is transmitted to the driving wheel 9 regardless of the state of connection / disconnection of the clutch 4, and the driving force generated by the engine 2 is driven only when the clutch 4 is connected. 9 side. Therefore, when the clutch 4 is disengaged, the positive or negative driving force generated by the motor 3 as described above is transmitted to the driving wheel 9 side, and the vehicle 1 travels. When the clutch 4 is connected, the driving force of the engine 2 and the motor 3 is transmitted to the driving wheel 9 side, or only the driving force of the engine 2 is transmitted to the driving wheel side, so that the vehicle 1 travels.

The vehicle ECU 13 is a control circuit for integrated control of the entire vehicle. For this purpose, the vehicle ECU 13 includes an accelerator sensor 15 that detects the operation amount θacc of the accelerator pedal 14, a brake switch 17 that detects the depression operation of the brake pedal 16, a vehicle speed sensor 18 that detects the speed V of the vehicle 1, and the rotation of the engine 2. An engine rotation speed sensor 19 that detects the speed Ne, a motor rotation speed sensor 20 that detects the rotation speed Nt of the motor 3, a navigation device 31 (downhill road prediction means), a communication device 32 (downhill road prediction means), and the like are connected. Yes.
The vehicle ECU 13 is connected with an actuator (not shown) for connecting / disconnecting the clutch 4 and an actuator for shifting the automatic transmission 5, and an engine ECU 22 for engine control and an inverter ECU 23 for inverter control. And a battery ECU 24 for managing the battery 11 are connected.

The vehicle ECU 13 calculates a required torque necessary for the vehicle 1 to travel based on the accelerator operation amount θacc by the driver, and selects the travel mode of the vehicle 1 based on the required torque, the SOC of the battery 11, and the like. In this embodiment, an E / G mode that uses only the driving force of the engine 2, an EV mode that uses only the driving force of the motor 3, and an HEV mode that uses both the driving force of the engine 2 and the motor 3 are set as the traveling mode. The vehicle ECU 13 selects one of the travel modes.
The vehicle ECU 13 converts the required torque into a torque command value to be output by the engine 2 or the motor 3 based on the selected travel mode. For example, in the HEV mode, the required torque is distributed to the engine 2 side and the motor 3 side, and torque command values for the engine 2 and the motor 3 are calculated based on the gear position at that time. In the E / G mode, the required torque is converted into a torque command value for the engine 2 based on the gear position, and in the EV mode, the required torque is converted into a torque command value for the motor 3 based on the gear speed.

  Then, the vehicle ECU 13 disconnects the clutch 4 in the EV mode and connects the clutch 4 in the E / G mode and HEV mode in order to execute the selected travel mode, and then sends a torque command value to the engine ECU 22 and the inverter ECU 23. Output as appropriate. Further, during traveling of the vehicle 1, the vehicle ECU 13 calculates a target gear position from a shift map (not shown) based on the accelerator operation amount θacc, the vehicle speed V, and the like, and the actuator 4 connects and disconnects the clutch 4 to achieve this target gear position. Executes operation and gear change operation.

  On the other hand, the engine ECU 22 executes injection amount control and injection timing control of the engine 2 so as to achieve the travel mode and torque command value input from the vehicle ECU 13. For example, in the E / G mode and the HEV mode, the driving force is generated in the engine 2 with respect to the positive torque command value, and the engine brake is generated with respect to the negative torque command value. Further, in the EV mode, the engine 2 is stopped and held by stopping the fuel injection or is set in an idle operation state.

Further, the inverter ECU 23 drives and controls the inverter 10 so as to achieve the travel mode and the torque command value input from the vehicle ECU 13. For example, in the EV mode or HEV mode, the motor 3 is power-running for the positive torque command value to generate a positive driving force, and the motor 3 is power-running for the negative torque command value. Generate negative driving force. In the E / G mode, the driving force of the motor 3 is controlled to zero.
Further, the battery ECU 24 detects the temperature of the battery 11, the voltage of the battery 11, the current flowing between the inverter 10 and the battery 11, etc., calculates the SOC of the battery 11 from these detection results, and detects this SOC. It outputs to vehicle ECU13 with a result.

With the above control, the vehicle 1 always travels with the driving force of the engine 2 and the motor 3 according to the required torque, and the SOC of the battery 11 is set in a preset control range, in this embodiment, the control range of 25 to 75%. (Operation control means).
On the other hand, the navigation device 31 specifies the vehicle position on the map while the vehicle 1 is traveling, based on the map data stored in its own storage area, the GPS information received via the antenna, and the like. The communication device 32 performs road-to-vehicle communication with a roadside communication system of a data center that is appropriately installed on the roadside, and performs vehicle-to-vehicle communication with other vehicles that are traveling around.

Examples of information to be communicated include map information not owned by the own vehicle, road information (such as road curves and gradients), traffic information (such as traffic jam information, accident information, and construction information). The communication device 32 acquires these information from the roadside communication system and other vehicles, or conversely supplies these information to other vehicles.
The vehicle ECU 13 predicts whether there is a downhill road ahead of the host vehicle based on the host vehicle position specified by the navigation device 31, the road information acquired by the communication device 32, and the like. When the presence of the downhill road is predicted, the SOC control range of the battery 11 is expanded at a point before the downhill road as in the technique of Patent Document 1, and the power running control of the motor 3 is performed based on the expanded control range. And fuel consumption is reduced by performing regenerative control.

However, as described in [Problems to be Solved by the Invention], if the control range set for protection of the battery 11 is expanded, there is a concern that the durability of the battery 11 may be reduced due to excessive charging and discharging. On the other hand, even if the control range is expanded, if the charge / discharge current is limited based on Equation (1) in order to prevent damage due to heat generation, the expanded region of the control range cannot be used effectively.
In view of such a problem, in the present embodiment, measures for suppressing currents due to power running control and regenerative control of the motor 3 are taken in the enlarged range of the upper and lower limits of the control range. The process executed by will be described.

FIG. 2 is a flowchart showing a downhill road corresponding motor control routine executed by the vehicle ECU 13, and FIG. 3 is a time chart showing a motor control execution state when a downhill road is predicted. In FIG. 3, the control status of the embodiment is indicated by a solid line, and the control status of the technology of Patent Document 1 which is the prior art is indicated by a broken line.
The vehicle ECU 13 executes the routine of FIG. 2 at a predetermined control interval while the vehicle 1 is traveling. First, in step S <b> 2, the vehicle position is input from the navigation device 31 and road information is acquired from the communication device 32. In the following step S4, it is predicted based on these information whether or not a downhill road exists within a predetermined distance (for example, 2 km) ahead of the host vehicle (downhill road prediction means), and once the determination is No (No), End the routine.

  When the determination in step S4 is Yes (positive), the process proceeds to step S5, and it is determined whether or not the SOC range needs to be expanded. The determination of the necessity of expansion of the SOC range is performed based on, for example, the prediction of regenerative energy obtained from a downhill road, and when there is a possibility that regenerative energy exceeding the SOC control range is obtained, the SOC range is expanded. In other cases, the SOC range is not expanded. This is for the protection of the battery 11, and the effect of maintaining the battery performance for a long time can be expected.

When the determination in step S5 is No, the routine is temporarily terminated. When the determination in step S5 is Yes, the process proceeds to step S6, and the SOC control range is expanded (control range expansion means). In the present embodiment, the upper and lower limits of the control range are equally increased by 5% and changed to 20 to 80%. However, the present invention is not limited to this, and the enlargement width may be changed, and the upper limit and the lower limit may be unevenly enlarged.
Hereinafter, for convenience of explanation, the upper limit of the normal control range is the normal upper limit SOCup, the lower limit is the normal lower limit SOClo, the upper limit of the control range after expansion is the expansion upper limit SOCupex, and the lower limit is the expansion lower limit SOCloex. Further, a region from the normal upper limit SOCup to the expansion upper limit SOCupex and a region from the normal lower limit SOClo to the expansion lower limit SOCloex are respectively referred to as an expansion region.

  Thereafter, the vehicle ECU 13 executes power running control of the motor 3 in step S8 with normal control contents. For example, the HEV mode is selected as the travel mode at this time, and the SOC of the battery 11 gradually decreases due to the power consumption for driving the motor 3 as shown in FIG. In step S8, in order to reliably lower the SOC of the battery 11 to the enlarged region on the lower limit side of the control range, for example, torque distribution on the motor 3 side is increased (torque on the engine 2 side) instead of normal control content. Control may be performed to reduce the distribution.

In step S10, the vehicle ECU 13 determines whether or not the SOC of the battery 11 is less than the normal lower limit SOClo, and returns to step S6 if No. As indicated by point a in FIG. 3, when the SOC of the battery 11 decreases to the normal lower limit SOClo, the vehicle ECU 13 makes a Yes determination in step S10 and proceeds to step S12. In step S12, the power running control of the motor 3 is continued with the control content that suppresses the current supplied to the motor 3 (operation control means).
For this reason, as shown in FIG. 3, the SOC of the battery 11 continues to decrease while relaxing the decrease rate within the lower limit side expansion region, and is maintained at the expansion lower limit SOCloex after reaching the expansion lower limit SOCloex at point b. Therefore, thereafter, the power running control of the motor 3 is stopped, and the driving of the engine 2 continues the traveling of the vehicle 1.

  When the vehicle 1 reaches the downhill road, the driver's accelerator operation is stopped, and the vehicle 1 starts traveling on the downhill road while consuming potential energy. For this reason, vehicle ECU13 transfers to step S14 from step S12, and starts regenerative control. In step S <b> 14, regenerative control is performed with control contents that suppress the current generated by the motor 3 (operation control means). For this reason, when the vehicle 1 reaches the downhill road at the point c in FIG. 3, the SOC of the battery 11 starts to gradually increase within the enlarged region on the lower limit side.

  In step S16, the vehicle ECU 13 determines whether or not the SOC of the battery 11 is equal to or higher than the normal lower limit SOClo, and returns to step S14 if No. When the SCO reaches the normal lower limit SOClo as indicated by a point d in FIG. 3, a Yes determination is made in step S16, and regenerative control of the motor 3 is executed with normal control contents in step S18. Thereafter, in step S20, it is determined whether or not the SOC of the battery 11 is equal to or higher than the normal upper limit SOCup. If NO, the process returns to step S18.

By the process of step S18, the motor 3 continues the regenerative control without being suppressed in current, and the SOC rapidly increases and reaches the normal upper limit SOCup as indicated by a point e in FIG. The vehicle ECU 13 makes a Yes determination in step S20 and proceeds to step S22. As in step S14, the vehicle ECU 13 performs regenerative control of the motor 3 with the control content that suppresses the generated current (operation control means), and then executes the routine. finish.
Therefore, as shown in FIG. 3, the SOC of the battery 11 continues to increase while slowing the increase speed within the upper limit side expansion region, and reaches the expansion upper limit SOCupex at the point f. Thereafter, the regenerative control of the motor 3 is stopped, and an increase in the vehicle speed V on the downhill road is suppressed by using an engine brake or the like instead of the regenerative braking.

  As described above, when the presence of a downhill road is predicted in front of the vehicle 1, the SOC control range is expanded at the front point. During traveling until the vehicle 1 reaches the downhill road, the SOC of the battery 11 is lowered to the lower limit of the control range, and the discharged electric power is expended to drive the motor 3, thereby burdening the engine 2. This reduces fuel consumption. Further, when the vehicle travels on a downhill road thereafter, the SOC of the battery 11 is increased to the expansion upper limit SOCupex by regenerative control of the motor 3, and fuel consumption is saved by using the extra charged power for driving the motor later.

In the present embodiment, the input / output current due to the power running control and the regenerative control of the motor 3 is suppressed in the enlarged regions on the upper limit side and the lower limit side of the SOC control range. For this reason, as is clear from the comparison with the prior art indicated by the broken line in FIG. 3, according to the present embodiment, the SOC of the battery 11 increases or decreases more slowly in the enlarged region. For this reason, deterioration of the battery 11 resulting from the control of the SOC exceeding the normal control range can be suppressed to the minimum.
Further, as a result, the current at the time of charging / discharging of the battery 11 is reduced, so that the possibility that H calculated from the above equation (1) exceeds the upper limit allowable value is reduced. Therefore, when the SOC is controlled in the upper limit side or lower limit side enlarged region, the power running control and regenerative control of the motor 3 are interrupted due to the limitation of the charge / discharge current based on the formula (1). Can be prevented. As a result, the SOC can be controlled by always effectively using the expansion range of the control range, and the above-described effect of fuel economy can be reliably achieved.

  This is the end of the description of the embodiment, but the aspect of the present invention is not limited to this embodiment. For example, in the above-described embodiment, the present invention is embodied in the travel control device for the hybrid truck 1, but is not limited thereto, and may be embodied in, for example, a hybrid passenger car or a bus.

2 Engine 3 Motor 11 Battery 13 Vehicle ECU (Operation control means, downhill road prediction means, control range expansion means)
31 Navigation device (descent slope prediction means)
32 Communication device (descent slope prediction means)

Claims (2)

A hybrid electric vehicle equipped with an engine and a motor as a driving power source, driven by the driving force of the engine and the powering control of the motor, and regeneratively controlling the motor on a downhill road to charge the generated power to a battery In the travel control device of
Driving control means for controlling the operating state of the engine and motor while the vehicle is running, while maintaining the charging rate of the battery in a preset control range;
Downhill road prediction means for predicting downhill road existing in front of the vehicle,
When the downhill road ahead is predicted by the downhill road prediction means, the control range expansion means for expanding the control range of the charging rate at a point before the downhill road,
The driving control means controls the charging rate of the battery by powering control of the motor until the vehicle reaches the downhill road when the control range of the charging rate is expanded by the control range expanding unit. A travel control device for a hybrid electric vehicle, wherein the travel control device reduces the current to be supplied to the motor in the enlarged region while lowering it to the enlarged region on the lower limit side of the range.   When the vehicle reaches the downhill road and is traveling on the downhill road, the operation control means increases the charging rate of the battery to within an enlarged region on the upper limit side of the control range by regenerative control of the motor. And a travel control device for a hybrid electric vehicle characterized by suppressing current generated by the motor in the enlarged region.

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