JP6631433B2 - Control device for hybrid vehicle - Google Patents

Description

  The present invention relates to a control device for a hybrid vehicle, and more particularly to control of a battery during charging.

  2. Description of the Related Art A hybrid vehicle including a rotating electric machine functioning as an electric motor and a generator and an internal combustion engine as a prime mover is known. The hybrid vehicle is provided with a battery that supplies electric power to the rotating electric machine and is charged with electric power generated by the rotating electric machine. In order to prevent the battery from deteriorating, the charge / discharge power of the battery is controlled based on the amount of stored power and the temperature of the battery at that time so as not to become an excessive value. Also, a hybrid vehicle is known that can run in an electric vehicle mode in which the internal combustion engine is stopped and the vehicle is driven by the power of a rotating electric machine.

  Patent Document 1 below discloses a hybrid vehicle (hybrid vehicle 20) including an internal combustion engine (engine 22), a first rotating electric machine (motor MG1), and a second rotating electric machine (motor MG2) as prime movers. In the hybrid vehicle (20), when the internal combustion engine (22) is started while traveling in the electric vehicle mode, power is generated by the first rotating electrical machine MG1, and the generated power is charged in the battery. If the charging power exceeds the power that the battery can accept (input limit for starting determination), the internal combustion engine cannot be started. Therefore, when it is predicted that the charging power will exceed the start determination input limit, the internal combustion engine (22) is started before exceeding. The reference numerals in parentheses above are used in the following Patent Document 1, and are not related to the reference numerals in the embodiments of the present application.

JP 2014-184893 A

  2. Description of the Related Art In a metal ion battery such as a lithium ion battery, a phenomenon that a metal is deposited in the battery when charging is continued is known. As the duration of charging becomes longer, metal is more likely to be deposited. Therefore, during regenerative braking, the charging power (charging power limit value) that can be accepted by the battery is gradually reduced to prevent metal deposition and protect the battery. . If the charging power limit value becomes smaller than the charging power at the time of starting the internal combustion engine, the internal combustion engine cannot be started thereafter. In order to avoid this unstartable state, the internal combustion engine is started before the charging power limit value becomes smaller than the charging power at the time of starting the internal combustion engine. When the internal combustion engine is started due to the decrease in the charge power limit value of the battery while traveling in the electric vehicle mode, the electric vehicle mode is canceled at that time, and the traveling distance in the electric vehicle mode is reduced.

  It is an object of the present invention to reduce the frequency of starting the internal combustion engine during regenerative braking and to suppress a reduction in the traveling distance in the electric vehicle mode.

  The hybrid vehicle according to the present invention supplies power to the power unit in which the internal combustion engine, the first rotating electric machine and the second rotating electric machine are connected to the three elements of the planetary gear mechanism, and to the first rotating electric machine and the second rotating electric machine. And a battery that is charged with electric power from the first rotating electric machine and the second rotating electric machine, and is capable of traveling in an electric vehicle mode in which the internal combustion engine is stopped and the second rotating electric machine travels. The control device of the present invention is a control device for the hybrid vehicle, and performs operation control of the first rotating electric machine and the second rotating electric machine and charge / discharge control of the battery. Further, in the electric vehicle mode, the control device of the present invention calculates a charge power limit value for preventing metal deposition in the battery based on the charge current to the battery from the start of braking, and determines a predetermined charge power limit value from the charge power limit value. The regenerative power limit value is calculated by subtracting the value margin, and the generated power of the second rotating electrical machine is limited to the regenerative power limit value or less during regenerative braking.

  Since charging is performed with a value smaller than the charging power limit value by a margin, the increase in the concentration of metal ions is suppressed, and the reduction in the charging power limit value for preventing metal deposition is suppressed.

  By suppressing the reduction in the charging power limit value, the frequency of starting the internal combustion engine during regenerative braking is reduced, and the reduction in the traveling distance in the electric vehicle mode is suppressed.

FIG. 2 is a diagram illustrating a main configuration of a plug-in hybrid vehicle. FIG. 4 is a diagram for explaining a speed relationship of each prime mover at the time of starting the internal combustion engine. It is a figure for explaining the limit value of charge electric power and regenerative electric power. It is a control flowchart concerning charge power limitation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main configuration of plug-in hybrid vehicle 10. A plug-in hybrid vehicle is a hybrid vehicle that can charge a battery mounted on the vehicle with electric power from the outside. In a plug-in hybrid vehicle and a hybrid vehicle having no external charging function (hereinafter, referred to as a normal hybrid vehicle), a traveling mode in which the internal combustion engine is stopped and the vehicle is driven only by the rotating electric machine is set. For example, in a plug-in hybrid vehicle, at the beginning of operation, the vehicle is basically driven only by the rotating electric machine until the charged amount of the battery reaches a predetermined lower limit, and after reaching the lower limit, the internal combustion engine and the rotating electric machine are thereafter driven. To drive the vehicle. Hereinafter, a traveling mode in which the internal combustion engine is stopped and the traveling by the rotating electric machine is prioritized is referred to as an “electric vehicle mode”. On the other hand, a mode in which the internal combustion engine and the rotating electric machine are used in combination or switched according to a driver's request for acceleration / deceleration and a battery state such as a charged amount is referred to as a “hybrid vehicle mode”. In a plug-in hybrid vehicle, the vehicle travels in the electric vehicle mode from the beginning of operation until the charged amount of the battery reaches a predetermined lower limit, and shifts to the hybrid vehicle mode when the lower limit is reached.

  The power unit 12 of the plug-in hybrid vehicle 10 includes three prime movers of one internal combustion engine 14 and two rotating electric machines 16 and 18 for driving the vehicle. Each of the two rotating electric machines 16 and 18 can operate as a motor and a generator. The three prime movers 14, 16, 18 are connected to three elements (a carrier element, a sun element, and a ring element) of the planetary gear mechanism 20, respectively. In the power unit 12, one rotating electric machine 16 is connected to a sun gear 22 which is a sun element, and the other rotating electric machine 18 is connected to a ring gear 24 which is a ring element. Hereinafter, the rotating electric machine connected to the sun gear 22 is referred to as a first rotating electric machine 16, and the rotating electric machine connected to the ring gear 24 is referred to as a second rotating electric machine 18. A planetary carrier 26 as a carrier element rotatably supports a planetary pinion 28 meshing with the sun gear 22 and the ring gear 24. The internal combustion engine 14 is connected to the planetary carrier 26. The correspondence between the three prime movers and the three elements of the planetary gear mechanism to which they are connected may be a combination other than the above. The rotational speeds of the three prime movers 14, 16, and 18 have a predetermined relationship determined by the gear ratio of the planetary gear mechanism. When the rotational speeds of the two prime movers are determined, the rotational speeds of the remaining ones are determined. The ring gear 24 is provided with an output gear 30, from which power is output to drive wheels 36 via a reduction gear train 32 and a differential device 34.

  Power is supplied to the first and second rotating electric machines 16 and 18 from a battery 40 as a secondary battery via a power converter 38. In this plug-in hybrid vehicle 10, battery 40 is a lithium ion battery. The first and second rotating electric machines 16 and 18 can be three-phase AC synchronous rotating electric machines, and when these function as electric motors, the DC power from the battery 40 is converted into three-phase AC power by the power converter 38. Then, it is supplied to these rotating electric machines 16 and 18. When the first and second rotary electric machines 16 and 18 function as generators, the generated AC power is converted into DC power by the power converter 38 and supplied to the battery 40. One rotating electric machine, for example, the first rotating electric machine 16 can be made to function as a generator, and power can be supplied to the other second rotating electric machine 18. Further, an external connection plug 42 for connecting to an external power supply such as a commercial power supply is connected to the power converter 38. The battery 40 can be charged from the outside by connecting the external connection plug 42 to an external power supply. The charging from the external power supply is hereinafter referred to as “external charging”.

  The plug-in hybrid vehicle 10 further has a control device 44 for controlling the power unit 12. The control device 44 has a hybrid vehicle electronic control device (hereinafter, referred to as HV-ECU) 46 that controls the entire vehicle. The HV-ECU 46 obtains an acceleration / deceleration request from the driver's operation of the accelerator pedal 48, the brake pedal 50, and the like, and further obtains a vehicle speed, a driving state of each of the prime movers 14, 16, 18 and a power storage amount of the battery 40. The operation state of the vehicle is grasped, and an appropriate operation state of the vehicle is determined. Based on the determination of the operation state, each corresponding device is controlled via an electronic control unit (ECU) of each device. The internal combustion engine ECU 52 controls the throttle opening, the fuel injection amount, the valve timing, and the like of the internal combustion engine 14 to control the internal combustion engine 14 to the target rotation speed and output. The rotating electrical machine ECU 54 controls the power converter 38 to control the first and second rotating electrical machines 16 and 18 to have target rotation speeds and outputs. The battery ECU 56 monitors the charged amount of the battery 40 and sets an upper limit value and a lower limit value of the charged amount. In general, the deterioration of a battery progresses when the state of low charge and the state of high charge continue. In order to prevent this deterioration, an upper limit value and a lower limit value are set, and control is performed so that the charged amount falls within a certain range. In a plug-in hybrid vehicle, the upper limit may be set higher than that of a normal hybrid vehicle without an external charging function in order to extend the cruising distance in the electric traveling mode.

  Generally, in a hybrid vehicle, the internal combustion engine is started when the vehicle is running only with the rotating electric machine or when the amount of stored power in the battery is reduced. FIG. 2 is a diagram showing the speeds of the prime movers 14, 16, 18 when the internal combustion engine 14 is started during traveling. The three vertical axes indicate the rotational speeds of the internal combustion engine 14, the first rotating electric machine 16 and the second rotating electric machine 18, respectively. The abscissa indicates the stationary state (0), above which indicates normal rotation and below indicates reverse rotation. The interval between the vertical axes is determined based on the geometric dimensions of the planetary gear mechanism 20 (such as the ratio of the number of gear teeth). The rotation speeds of the motors 14, 16, 18 are always arranged on one straight line.

In the plug-in hybrid vehicle 10, traveling is performed by the second rotating electric machine 18 in the electric vehicle mode. The second rotating electric machine 18 rotates at a rotation speed N ₂ determined by the rotation speed of the drive wheels 36 and the gear ratio of the reduction gear train 32. The internal combustion engine 14 is stopped, that is, the rotation speed N _E e is zero. The rotation speed N ₁ e of the first rotating electric machine 16 at this time is on a straight line (dashed line in FIG. 2) passing through the rotation speeds (N ₁ , N _E e) of the internal combustion engine 14 and the second rotating electric machine 18.

When starting the internal combustion engine 14 rotates the internal combustion engine 14 at a predetermined rotational speed N _E i, performs ignition. Setting the rotation speed of the first rotating electric machine 16 to N ₁ i is a control to reduce the rotation of the first rotating electric machine 16 rotating in the reverse rotation direction. It will generate electricity. If the battery 40 cannot accept the generated power, the internal combustion engine 14 cannot be started. In a metal ion battery such as a lithium ion battery, when the charging current is large and the continuous charging time is long, metal (lithium) precipitates in the battery. In order to prevent this deposition, charging power is limited, which may cause the battery to be unable to accept power. If the charging power is limited, the internal combustion engine 14 cannot be started when necessary. If the internal combustion engine 14 is started before the internal combustion engine 14 cannot be started due to the limitation of charging power in order to avoid such a state that the internal combustion engine 14 cannot be started, the traveling distance in the electric vehicle mode is reduced.

  FIG. 3 is a diagram showing the relationship between the electric power generated by the first and second rotating electric machines 16 and 18, the electric power charged in the battery 40, and the limitation of the charging electric power. The vertical axis represents the charging power and the generated power, with the downward direction being positive. Therefore, the value of charging / generating power is larger as shown below in FIG. The horizontal axis is time. The solid line with “x” indicates the maximum value of the charging power when starting the internal combustion engine 14 (the internal combustion engine starting power Ps). The internal combustion engine starting power Ps is the sum of the maximum power that can be generated by the second rotary electric machine 18 during regenerative power generation and the power generated by the first rotary electric machine 16 for setting the internal combustion engine 14 to a rotational speed at which ignition is performed. It is determined based on. That is, the internal combustion engine starting power Ps is the maximum value of the charging power when the internal combustion engine 14 is started during the regenerative braking. If this value is secured, the internal combustion engine 14 can be started. In the actual control, the margin can be provided by setting the internal combustion engine starting power Ps to a value slightly larger than the maximum value of the charging power when the internal combustion engine 14 is started during the regenerative braking. The solid line with “○” indicates the maximum value of the electric power charged to the battery 40 (maximum charging electric power Pu). The chain line represents the regenerative power Ge, Gh of the second rotating electric machine 18. The thick solid line and the thin solid line represent the power limit values Lce and Lch for preventing metal deposition, and the thick broken line represents the power limit value Lge during regeneration. Hereinafter, the power limit values Lce and Lch are referred to as a charging power limit value, and the power limit value Lge is referred to as a regenerative power limit value Lge. The subscript “e” indicates a case where a control for reducing the frequency of starting the internal combustion engine due to the prevention of metal deposition in the battery (hereinafter referred to as “start frequency reduction control”) is applied. “H” indicates a case where this control is not applied. The regenerative power and charging power limit value when the start frequency reduction control is not applied are referred to as first regenerative power Gh and first charging power limit value Lch. The regenerative power, charging power limit value, and regenerative power limit value when the start frequency reduction control is applied are referred to as a second regenerative power Ge, a second charging power limit value Lce, and a second regenerative power limit value Lge.

  First, a control to which the start frequency reduction control is not applied will be described. During traveling, when a brake operation is performed at time t1, the second rotating electric machine 18 generates electric power, and this electric power (first regenerative electric power Gh) is charged in the battery 40. By this charging, lithium ions in the battery 40 gradually move to the negative electrode side, the ion concentration near the negative electrode increases, and metal lithium is easily deposited. As the current during charging is longer and the charging time is longer, the ion concentration in the vicinity of the negative electrode is higher, and precipitation is more likely. Once deposited lithium does not return to ions, deposition must be avoided. The control device 44 calculates the first charging power limit value Lch based on the charging current after the regenerative charging by the brake operation is started. By limiting the charging power to the first charging power limit value Lch or less, deposition of metallic lithium is prevented, and the battery is protected. The first charging power limit value Lch decreases with time, and the limit becomes stronger. When the first charging power limit value Lch decreases and becomes smaller than the internal combustion engine starting power Ps, the battery 40 cannot receive the power generated by the first rotating electric machine 16 for starting the internal combustion engine. Even if the internal combustion engine needs to be started in this state, it cannot be started. In order to avoid this, when the first charging power limit value Lch reaches the internal combustion engine starting power Ps (time t2), the control device 44 controls the internal combustion engine 14 to start. When the charging power limit value Lch reaches the first regenerative power Gh (time t3), thereafter, the control device 44 controls the first regenerative power Gh to be equal to or less than the first regenerative power limit value Lch. Therefore, the first charging power limit value Lch at this time also functions as a regenerative power limit value (first regenerative power limit value Lgh). At the time point t4, when the braking operation is completed, the ions near the negative electrode gradually diffuse, and accordingly, the control device 44 gradually increases the first charging power limit value Lch (weakens the limit). Between the time point t3 and the time point t4, the first regenerative power Gh is limited by the first charging power limit Lch, that is, the first regenerative power limit Lgh, so that it is not enough to generate the required braking force. Absent. During this time, the shortage of the regenerative braking force is compensated for by the friction brake.

  Next, control to which the start frequency reduction control is applied will be described. This control is applied to traveling in the electric vehicle mode. During traveling, when a brake operation is performed at time t1, the second rotating electric machine 18 generates electric power, and this electric power (second regenerative electric power Ge) is charged in the battery 40. The control device 44 calculates the second charging power limit value Lce based on the charging current from the start of braking, in accordance with the same processing as when the starting frequency reduction control is not applied. In the electric vehicle mode, the second regenerative power Ge is set to a value obtained by subtracting a predetermined constant value from the second charging power limit value Lce. This constant value is described as a margin m, and how to determine it will be described later.

Until the time point t5, the second regenerative power Ge is equal to the first regenerative power Gh, so that the second charging power limit value Lce and the first charging power limit value Lch calculated based on the charging current in each case are also equal. . At time t5, when the value obtained by subtracting the margin m from the second charging power limit value Lce matches the second regenerative power Ge , thereafter, the second regenerative power Ge is limited to the second regenerative power limit Lge . Become. After the time point t5, since the second regenerative power Ge is smaller than the first regenerative power Gh, the second charging power limit value Lce becomes a value larger than the first charging power limit value Lch (downward in FIG. 3). Thereby, the start of the internal combustion engine 14 can be delayed or the start is unnecessary. The braking force corresponding to the shortage of the second regenerative power Ge with respect to the first regenerative power Gh (the shaded region in FIG. 3) is supplemented by the friction brake.

  The margin m can be determined as follows. In the battery 40, when the movement of lithium ions due to charging and the diffusion of ions due to the concentration difference are balanced, the ion concentration near the negative electrode does not increase any more, and no metal is deposited. Such charging power is referred to as non-deposition power. When the second regenerative power Ge reaches the non-deposition power Pn (see FIG. 3), lithium deposition does not occur even if charging is continued thereafter. At this time, the second charging power limit value Lce does not decrease any more. Therefore, if the second regenerative power Ge is smaller than the second charging power limit value Lce by a difference between the internal combustion engine starting power Ps and the non-deposition power Pn, the second charging power limit value Lce becomes It does not reach the starting power Ps. That is, by setting the margin m to a value larger than the difference between the internal combustion engine starting power Ps and the precipitation-free power Pn, the second charging power limit value Lce does not reach the internal combustion engine starting power Ps, and the internal combustion engine 14 is started. Can be prevented. Further, even when the margin m is set to a value equal to or less than the difference between the internal combustion engine starting power Ps and the precipitation-free power Pn, the starting of the internal combustion engine 14 can be delayed, and if the braking period is short, the starting can be prevented. The frequency of starting can be reduced.

  FIG. 4 is a flowchart showing control of the plug-in hybrid vehicle 10, particularly control of the power unit 12 and the battery 40. The control device 44 determines whether the internal combustion engine 14 is stopped (S100). If the internal combustion engine 14 is not stopped, it is not necessary to start the engine, and the process exits from this flow. Further, it is determined whether or not the accelerator pedal 48 is depressed (accelerator off) (S102). If the accelerator is not off, that is, if the accelerator is on, the flow exits because regenerative power generation is not performed. It is determined whether the brake pedal 50 is depressed (brake-on) (S104), and whether the vehicle is running in the electric vehicle mode (S106).

  When the brake is not on or in the electric vehicle mode in steps S104 and S106, the control device 44 sequentially calculates the first charging power limit value Lch based on the charging current to the battery 40 from the start of the braking (S108). Based on this, the first regenerative power limit value Lgh is set as the regenerative power limit value, and the second rotating electric machine 18 is controlled so as to perform regenerative power generation at or below this limit value (S110). The first regenerative power limit Lgh is equal to the first charge power limit Lch for preventing lithium from being precipitated in the battery 40.

  In steps S104 and S106, when the brake is on and the electric vehicle mode is set, the control device 44 sequentially calculates the second charging power limit value Lce based on the charging current to the battery 40 from the start of braking (S112). Based on this, the second regenerative power limit value Lge is set as the regenerative power limit value, and the second rotating electric machine 18 is controlled so as to perform regenerative power generation at or below this limit value (S114). The second regenerative power limit Lge is a value obtained by subtracting a margin m from the second charge power limit Lce for preventing lithium from being precipitated in the battery 40. Since the second regenerative power limit value Lge is smaller than the first regenerative power limit value Lgh, the regenerative power, that is, the power for charging the battery 40 is reduced. Therefore, an increase in the concentration of lithium ions near the negative electrode is suppressed, and the limitation by the second charging power limit value Lce is relaxed compared to the limitation by the first charging power limit value Lch. In step S112, the control device 44 determines whether the charging power limit value (Lce or Lch) set at that time is smaller than the internal combustion engine starting power Ps (S116). (S118) If it is not small, the process goes through this flow. The above flow is repeated at a predetermined cycle.

  Battery 40 is not limited to a lithium ion battery, and may be another metal ion battery such as a sodium ion battery. The control device 44 is not limited to the HV-ECU 46, the internal combustion engine ECU 52, the rotating electric machine ECU 54, and the battery ECU 56, but may be configured integrally with a part or all of each ECU.

  Although the plug-in hybrid vehicle 10 has been described above, the present invention is not limited to this, and the above-described control can be applied to a normal hybrid vehicle having no external charging function. In a normal hybrid vehicle, there is a vehicle in which a driver can select a mode in which the vehicle runs only by the rotating electric machine, and such a mode can be said to be an electric vehicle mode. For example, the driver can select this electric vehicle mode in order to suppress the traveling sound of the vehicle from affecting the surroundings. Also in this electric vehicle mode, if the internal combustion engine is started to protect the battery, that is, when the power limit value is reduced, an undesirable start of the internal combustion engine is executed. In this case, in the above example, the expected low-noise running cannot be achieved.

  Reference Signs List 10 plug-in hybrid vehicle, 12 power unit, 14 internal combustion engine, 16 first rotating electric machine, 18 second rotating electric machine, 20 planetary gear mechanism, 22 sun gear, 24 ring gear, 26 planetary carrier, 28 planetary pinion, 30 output gear, 32 reduction gear train, 34 differential gear, 36 drive wheels, 38 power converter, 40 battery, 42 external connection plug, 44 control device, 46 HV-ECU, 48 accelerator pedal, 50 brake pedal, 52 internal combustion engine ECU, 54 Rotating electric machine ECU, 56 battery ECU, Ps Internal combustion engine starting power, Pu maximum charging power, Gh first regenerative power, Ge second regenerative power, Lgh first regenerative power limit, Lge second regenerative power limit, Lch first Charge power limit value, Lce Second charge power limit value.

Claims (1)

A power unit in which an internal combustion engine, a first rotating electric machine and a second rotating electric machine are respectively connected to three elements of a planetary gear mechanism;
A battery that is a metal ion battery, which supplies power to the first rotating electrical machine and the second rotating electrical machine and is charged with power from the first rotating electrical machine and the second rotating electrical machine;
A control device for a hybrid vehicle having an internal combustion engine stopped and capable of running in an electric vehicle mode in which the vehicle is driven by a second rotating electric machine,
The control device performs operation control of the first rotating electric machine and the second rotating electric machine and charge / discharge control of the battery,
In the electric vehicle mode, the control device includes:
A charge power limit value (Lce) for preventing metal deposition in the battery is calculated based on the charge current to the battery from the start of braking,
It is larger than the difference between the internal combustion engine starting power (Ps), which is the maximum value of the charging power when starting the internal combustion engine, and the deposition-free power (Pn), which is the charging power at which the concentration of metal ions near the negative electrode of the battery does not increase. margin (m) is a value, calculates the regenerative power limit value (Lge) was calculated charge power limit value (Lce) or al down,
Limiting the power generated by the second rotating electric machine to a regenerative power limit value (Lge) or less during regenerative braking
Control device for hybrid vehicle.

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