JP6210677B2 - Travel control device for hybrid electric vehicle - Google Patents

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 SOC (State of Charge) range, it is possible to always secure a room for performing the power running control and the regenerative control of the motor, and to charge and discharge the battery excessively. It is preventing.

  In such a hybrid electric vehicle, various techniques have been proposed for efficiently operating the engine and the motor. For example, in the technique disclosed in Patent Document 1, a travel condition (for example, undulation condition) on a planned travel path of a vehicle is acquired using a navigation system, and future engine and motor operation amounts are estimated based on the acquired travel condition. Control each.

JP 2007-126145 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。 To express the technology of Patent Document 1 in a straightforward manner, the engine and motor can be controlled in a highly efficient region by grasping in advance the opportunities for powering control and regenerative control of the motor on the ascending / descending slope based on the traveling conditions of the planned traveling path. Driving to improve the energy efficiency of the entire vehicle. However, since the load on the battery side due to the power running control and regenerative control of the motor is not taken into consideration, there may be a problem caused by this.
In other words, using the motor in a high-efficiency area means that an area with a large input / output is used frequently, which inevitably increases the burden on the battery and promotes deterioration.
In addition, 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 t of the battery, an index corresponding to the heat generation amount H is calculated from the following equation (1), and when the heat generation amount index H reaches a preset upper limit allowable value: Measures have been taken to limit the charge / discharge current.

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

Therefore, even if an attempt is made to use the motor in a highly efficient region as in the technique of Patent Document 1, the charge / discharge current of the battery is limited based on the calorific value index H, and an expected energy efficiency improvement effect can be obtained. There may be no.
The present invention has been made to solve such problems, and the object of the present invention is to prevent the deterioration of durability due to an increase in the burden on the battery and to charge / discharge the battery based on the heat generation amount. It is an object of the present invention to provide a travel control device for a hybrid electric vehicle that makes it possible to improve the energy efficiency of the entire vehicle and achieve fuel savings by making it less likely to be restricted by current.

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; By means of an uphill / downhill road prediction means for predicting an uphill / downhill road that is a traveling section including the uphill road and the downhill road existing in front of the vehicle, and by powering control or regenerative control of the motor in the uphill road section predicted by the uphill / downhill road prediction means a variation pattern estimating means for estimating a variation pattern of the charging rate of the battery, the variation patterns of SOC in the uphill slope section traveling Offset amount calculation means for calculating the offset amount of offsetting the variation pattern of the charging rate so as to substantially coincide with the maximum value to the upper limit of the control range of the offset amount variation pattern of the charging rate in the predicted uphill slope in the interval Offset means for offsetting to the upper limit side based on the above, and when the vehicle is traveling in an uphill / downhill section, the charge rate of the battery follows the fluctuation pattern of the charge rate after offset by the offset means The operating state of the engine and motor is controlled so as to fluctuate.

According to a second aspect of the present invention, in the first aspect, the operation control means increases the battery charging rate by an amount corresponding to the offset while the vehicle travels until the vehicle reaches the starting point of the uphill / downhill road, while the end point of the uphill / downhill road During the subsequent running, the charging rate of the battery is reduced by an amount corresponding to the offset .

As described above, according to the travel control device for a hybrid electric vehicle of the invention of claim 1, when an uphill road is predicted in front of the vehicle, the battery is driven by power running control or regenerative control of the motor in the uphill road section. The charging rate fluctuation pattern is estimated and offset so that the maximum value of the fluctuation pattern approximately matches the upper limit of the charging rate control range. The charging rate of the battery was changed according to the change pattern.
Therefore, by controlling the charging rate in the vicinity of the upper limit within the control range, the battery voltage rises and the charge / discharge current is reduced. For this reason, the burden on the battery is reduced, and it is difficult to be restricted by the charge / discharge current based on the heat generation amount. Accordingly, it is possible to improve the energy efficiency of the entire vehicle and achieve fuel savings while preventing the battery durability from being lowered due to an increase in charge / discharge current.

According to the traveling control apparatus for a hybrid electric vehicle of the invention of claim 2, in addition to claim 1, the battery charging rate is increased by an amount corresponding to the offset during traveling until the vehicle reaches the starting point of the uphill / downhill road. During driving after the end of the uphill / downhill road, the charging rate is reduced by the amount equivalent to the offset.
Therefore, although the charging rate fluctuation patterns are different before and after the offset, the balance of the charging rate can be matched .

1 is an overall configuration diagram showing a hybrid truck on which a travel control device of an embodiment is mounted. It is a characteristic view which shows the relationship between SOC of a battery, and a voltage. It is a flowchart which shows the SOC offset control routine which vehicle ECU performs. It is a time chart which shows the execution condition of SOC offset control when drive | working the up-and-down slope. It is a time chart which shows the test result which compared the restriction | limiting condition based on the emitted-heat amount of SOC offset control and normal SOC control.

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 (regeneration 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 (uphill slope prediction means), a communication device 32 (uphill slope 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, which is 30 to 70% in this embodiment. (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 an uphill / downhill road ahead of the own vehicle based on the own vehicle position specified by the navigation device 31, the road information acquired by the communication device 32, and the like. Hereinafter, the uphill road of the present invention is defined as including a section where a single uphill road is continuous, a section where a single downhill road is continuous, and a section where an uphill road and a downhill road are alternately continuous. To do.

  As described in [Problems to be Solved by the Invention], the technique of Patent Document 1 gives priority to operating the engine 2 and the motor 3 in a high-efficiency region when an uphill / downhill road is predicted. For this reason, there is a concern that the load on the battery 11 is increased and the durability is lowered. Even if the motor 3 is intended to be used in a high efficiency region, the desired energy efficiency improvement effect may not be obtained due to the limitation of the charge / discharge current based on the calorific value index H of the above equation (1).

In view of this problem, the present inventor has focused on the relationship between the SOC of the battery 11 and the voltage. As described above, the SOC of the battery 11 is maintained within a predetermined control range. However, as shown in FIG. 2, even within the control range, the SOC increases as the SOC increases. For this reason, if the SOC is controlled near the upper limit within the control range, the charge / discharge current of the battery 11 can be reduced even if the same torque is generated. If the charge / discharge current is reduced, it means that the burden on the battery 11 is reduced and the charge / discharge current is not easily limited based on the heat generation amount index H.
On the other hand, the control range is set in advance in order to secure room for powering control and regenerative control of the motor 3 and to prevent excessive charging / discharging of the battery 11. Even if the SOC of the battery 11 is controlled to the upper limit side, no problem occurs.

  Under the above viewpoint, in the present embodiment, the SOC of the battery 11 is offset to the upper limit side of the control range in comparison with the normal SOC control during traveling on the uphill / downhill road section. For convenience of explanation, this control is referred to as SOC offset control with respect to normal SOC control, and will be described below.

FIG. 3 is a flowchart showing an SOC offset control routine executed by the vehicle ECU 13, and FIG. 4 is a time chart showing an execution state of the SOC offset control when traveling on an uphill / downhill road. FIG. 4 shows a case where uphill roads and downhill roads continue alternately as uphill / downhill roads, and the normal SOC control status is indicated by a broken line, and the SOC offset control status is indicated by a solid line.
The vehicle ECU 13 executes the routine of FIG. 3 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 subsequent step S4, it is predicted based on these pieces of information whether or not there is an uphill / downhill road within a predetermined distance ahead of the host vehicle (uphill / downhill road prediction means), and when the determination is No (No), the routine is temporarily terminated. .

  When the determination in step S4 is Yes (positive), the process proceeds to step S6, and the vehicle speed V and the SOC of the battery 11 are read. In the subsequent step S8, the travel energy required to travel in the uphill / downhill section and the sections before and after the section (the section from point A to point B in FIG. 4) is calculated. Thereafter, the following requirements 1) to 7) are calculated in step S10 based on various information such as travel energy and the slope of each uphill / downhill road. As will be described later, each of these requirements is for executing the SOC offset control in the uphill / downhill section.

1) SOC fluctuation pattern by normal SOC control 2) SOC fluctuation width W
3) Variation pattern start time a
4) Variation pattern end time b
5) Offset offset of fluctuation pattern Offset
6) Advance SOC adjustment period Aa
7) Subsequent SOC adjustment period b-B
The SOC fluctuation pattern of requirement 1) is an estimation of how the SOC of the battery 11 changes when traveling on an uphill / downhill road by applying normal SOC control (fluctuation pattern estimation means). As shown by a broken line in FIG. 4, since the power running control of the motor 3 is performed on the uphill road and the regenerative control is performed on the downhill road, the SOC repeatedly increases and decreases according to the road surface gradient in the uphill road section. .

The variation width W of requirement 2) is the maximum width (= maximum SOC−minimum SOC) of the variation pattern of the SOC estimated according to requirement 1).
The start time a of requirement 3) corresponds to the start point of the uphill / downhill road, and the end time b of requirement 4) corresponds to the end point of the uphill / downhill road.
The offset amount Offset in requirement 5) is a movement amount when offsetting the SOC fluctuation pattern in the uphill / downhill section (point ab) to the upper limit side of the control range. In the present embodiment, the offset amount Offset is calculated so that the maximum value of the fluctuation pattern of normal SOC control matches the upper limit of the control range (offset amount calculation means) . However, the offset amount Offset is not limited to this as long as the SOC variation pattern is offset to the upper limit side of the control range.

  The adjustment period A-a of requirement 6) is for determining the point A on the basis of the start time a, and for increasing the SOC based on the normal SOC control to a value after offset (corresponding to the offset amount Offset). It is calculated as the period required for. The adjustment period b-B of requirement 7) is for determining the point B with the end time b as a reference, and the offset SOC is reduced to the normal SOC control value (also equivalent to the offset amount Offset). It is calculated as the period required for

According to the above requirements 1) to 7), the SOC fluctuation pattern in the section from point A to point B including the uphill slope shown by the solid line in FIG. 4 is determined. In the uphill / downhill section, the SOC variation pattern is offset to the upper limit side of the control range based on the offset amount Offset (offset means).
Then, the vehicle ECU 13 controls driving of the engine 2 and the motor 3 based on the requirements 1) to 7) in step S12, and thereafter ends the routine. Thereby, the vehicle travels in the section of points A to B, and the SOC of the battery 11 varies according to the variation pattern indicated by the solid line in FIG.

The control status by the SOC offset control will be described in more detail based on FIG.
First, in the preceding SOC adjustment period Aa, since the SOC is preserved by stopping the power running control of the motor 3 (motor torque = 0), the SOC is offset after the offset when reaching the uphill / downhill road (starting time a). Adjusted to the value. In the section of the uphill / downhill road, the SOC repeatedly increases and decreases according to the road surface gradient in the region near the upper limit side of the control range. However, as for the motor torque, a value necessary for driving the vehicle on the uphill / downhill road is output, unlike the case of normal SOC control.
In the subsequent SOC adjustment period b-B after the end of the ascending / descending slope, the SOC is gradually decreased by controlling the motor torque by the power running control to the increasing side, and at the point B, the value is returned to the normal SOC control value.
Therefore, in the section of points A to b, the SOC offset pattern in the SOC offset control is different from that in the normal SOC control, but the SOC balance between points A and B is the same. Specifically, the SOC preserved in the preceding SOC adjustment period Aa is used for running the vehicle 1 without waste in the subsequent SOC adjustment period b-B.

According to the SOC offset control, since the SOC is controlled in the vicinity of the upper limit of the control range in the uphill / downhill section, the voltage of the battery 11 rises as compared with the normal SOC control. Even if the same input / output (the same motor torque) is inevitably generated, the charge / discharge current of the battery 11 is reduced, and the burden on the battery 11 can be reduced to prevent the durability from being lowered.
Moreover, the reduction of the charging / discharging current of the battery 11 means that it becomes difficult to receive the limitation of the charging / discharging current based on the calorific value index H.

FIG. 5 shows a test in which the motor torque is periodically varied between the power running side and the regeneration side, and the restriction status based on the heat generation amount index H is compared between the SOC offset control and the normal SOC control. In the figure, the case of SOC offset control is indicated by a thick line, and the case of normal SOC control is indicated by a thin line.
Depending on the power running control and regenerative control of the motor 3, the charging / discharging current of the battery 11 fluctuates on the positive side and the negative side. The fluctuation values of the discharge current (positive side) from the battery 11 accompanying the power running control are not uniform because of the limitation based on the calorific value index H, respectively. Due to this limitation, the SOC offset control and the normal SOC are performed. The fluctuation value of the discharge current with the control is almost the same. However, since the voltage of the battery 11 is higher in the SOC offset control, it can be estimated that the motor torque is increased and a value close to the required torque is achieved. This tendency can also be seen from the fact that the total discharge power from the battery 11 is higher in the SOC offset control.

Further, each variation of the charging current (negative side) to the battery 11 due to the regenerative control is limited based on the heat generation amount index H in the SOC offset control as in the normal SOC control. However, since the current value is low in the SOC offset control, for example, the timing at which the restriction based on the heat generation amount index H starts to be delayed is equivalent to the period t in FIG. As a result, in SOC offset control, a high regenerative torque can be maintained over a longer period. This tendency can also be seen from the fact that the total charge power to the battery 11 is high.
Therefore, according to the SOC offset control, it is difficult to be restricted based on the calorific value index H on both the discharge side and the charge side of the battery 11, so that it is possible to realize motor control that is more suitable for the required torque. For this reason, more electric power can be charged to the battery 11 at the time of regenerative control of the motor 3, and a higher motor torque can be output at the time of power running control to reduce the load on the engine 2. Therefore, the energy efficiency of the whole vehicle can be improved and it can contribute to fuel consumption reduction.

  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, uphill slope prediction means, fluctuation pattern estimation means, offset means ,
Offset amount calculation means )
31 Navigation device (uphill / downhill road prediction means)
32 Communication device (uphill 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;
An ascending / descending slope prediction means for predicting an ascending / descending slope that is a traveling section including the ascending slope and the descending slope existing in front of the vehicle;
Fluctuation pattern estimation means for estimating a fluctuation pattern of the charging rate of the battery by powering control or regenerative control of the motor in the section of the climbing slope predicted by the climbing slope prediction means;
Offset amount calculation means for calculating an offset amount for offsetting the variation pattern of the charging rate so that the maximum value of the variation pattern of the charging rate during traveling on the ascending / descending slope section substantially matches the upper limit of the control range;
Offset means for offsetting the fluctuation pattern of the charging rate in the predicted uphill / downhill section to the upper limit side based on the offset amount, and
When the vehicle is traveling in the ascending / descending slope section, the operation control means is configured to change the charge rate of the battery according to the fluctuation pattern of the charge rate after offset by the offset means. A traveling control apparatus for a hybrid electric vehicle, characterized by controlling a driving state of a motor.   The driving control means increases the charging rate of the battery by an amount corresponding to the offset during traveling until the vehicle reaches the starting point of the uphill road, while traveling after the end point of the uphill road. 2. The travel control apparatus for a hybrid electric vehicle according to claim 1, wherein the charging rate of the battery is reduced by an amount corresponding to the offset.

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