Patent Description:
In the related art, there has been known a so-called series hybrid vehicle including an electric motor that drives the vehicle and an engine that drives a generator that generates electric power to be supplied to the electric motor. In the case of this series hybrid vehicle, the engine is stopped or operated in accordance with a state of charge of the battery and required electric power of the vehicle.

However, since the air density is low and an engine output is reduced at a high altitude, the electric power generated by the engine is reduced more than at a level ground. Therefore, for example, <CIT> discloses an engine operation control device for a hybrid vehicle that performs correction such that a set rotation speed of an engine increases as the atmospheric pressure at a current position of a vehicle decreases. An engine operation control device for a hybrid vehicle is also disclosed in <CIT>.

In the above-described related art, since the set rotation speed of the engine is increased as the atmospheric pressure decreases, it is possible to ensure a certain amount of electric power generated by the engine even at a high altitude. However, when a state in which the output of the electric motor is large continues as in a case where the vehicle travels on an expressway at a high altitude, an SOC of the battery may decrease, and a travel distance of the vehicle may become short.

An object of the present invention is to prevent a decrease in SOC of a battery and to extend a travel distance of a vehicle even when an output of an engine is limited.

The invention relates to a method for controlling a vehicle according to claim <NUM> and to a system for controlling a vehicle according to claim <NUM>. The method for controlling a vehicle according to claim <NUM> is a method for controlling a vehicle, the vehicle including an electric motor configured to drive the vehicle, an engine configured to drive a generator that generates electric power to be supplied to the electric motor, and a battery configured to be charged by the generator and electrically connected to the electric motor, and the method for controlling a vehicle including, a control step of limiting a driving force of the electric motor in a case where the vehicle is traveling in an environment in which an output of the engine is limited.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

<FIG> is a block diagram illustrating a configuration example of a vehicle <NUM> according to a first embodiment of the present invention.

The vehicle <NUM> includes an engine <NUM>, a generator <NUM>, a battery <NUM>, an electric motor <NUM>, an inverter <NUM>, a drive system controller <NUM>, and a power generation system controller <NUM>. The vehicle <NUM> also includes a kickdown switch (not illustrated) that is actuated when an accelerator pedal is depressed to a predetermined position. The kickdown switch may also be referred to as a depression force step pedal.

Each of the drive system controller <NUM> and the power generation system controller <NUM> is a control device that controls various devices, and is implemented by a microcomputer including, for example, a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input/output interface (I/O interface).

The drive system controller <NUM> functions as a control unit that controls operations of various devices such as the battery <NUM>, the electric motor <NUM>, and the inverter <NUM> provided in the vehicle <NUM> by executing a specific program.

The power generation system controller <NUM> functions as a control unit that controls operations of various devices such as the engine <NUM>, the generator <NUM>, and the battery <NUM> provided in the vehicle <NUM> by executing a specific program.

Each of the drive system controller <NUM> and the power generation system controller <NUM> may be implemented by a plurality of microcomputers instead of being implemented by one microcomputer. In addition, the drive system controller <NUM> and the power generation system controller <NUM> may be implemented by a single microcomputer. In this way, the drive system controller <NUM> and the power generation system controller <NUM> implement a system for controlling the vehicle <NUM>.

The vehicle <NUM> is implemented as a so-called series hybrid vehicle in which electric power generated by the generator <NUM> using power of the engine <NUM> is supplied to the battery <NUM> via the inverter <NUM>, and the electric motor <NUM> is caused to rotate based on the electric power of the battery <NUM> to drive drive wheels (not illustrated) of the vehicle <NUM>. Therefore, in the vehicle <NUM>, the engine <NUM> is used not as a power source for causing the vehicle <NUM> to travel but as a power source for causing the generator <NUM> to generate electric power.

The engine <NUM> is a so-called internal combustion engine using gasoline or the like as fuel, and is mechanically connected to the generator <NUM>. The engine <NUM> is used as a drive source for rotationally driving the generator <NUM> when the battery <NUM> is charged or the like.

The generator <NUM> generates electric power by rotating in accordance with the power from the engine <NUM>, and is able to charge the battery <NUM>. The generator <NUM> also causes the engine <NUM> to perform a power running operation (motoring) by being rotationally driven by the electric power of the battery <NUM>. As described above, by executing a motoring control for causing the engine <NUM> to rotate by using power of the generator <NUM>, it is possible to crank the engine <NUM> at the time of starting the engine <NUM>, or to close a throttle valve to generate a negative pressure in an intake passage when a negative pressure for brake pedal assist is required. As described above, the generator <NUM> functions as both a power generation motor and an engine starter.

The drive system controller <NUM> includes a target driving force calculation unit <NUM>, a torque conversion unit <NUM>, a high altitude determination unit <NUM>, a K/D determination unit <NUM>, a driving torque limiting unit <NUM>, and a selection unit <NUM>.

The target driving force calculation unit <NUM> calculates a driving force (torque command value of the electric motor <NUM>) required by the vehicle <NUM> based on an accelerator position (accelerator opening degree) (APO) and a vehicle speed, and outputs a calculation result thereof to the selection unit <NUM>. Incidentally, the driving force is also referred to as a driving torque. The accelerator position can be acquired based on an operation amount of the accelerator pedal in the vehicle <NUM>, and the vehicle speed can be acquired by a vehicle speed sensor in the vehicle <NUM>.

The torque conversion unit <NUM> calculates a driving force that can be supplied from the battery <NUM> to the electric motor <NUM> based on a maximum suppliable electric power of the battery <NUM>, and outputs a calculation result thereof to the selection unit <NUM>.

The high altitude determination unit <NUM> determines whether the vehicle <NUM> is traveling in an environment in which the output of the engine <NUM> is limited, and outputs a determination result thereof to the driving torque limiting unit <NUM>. Here, the environment in which the output of the engine <NUM> is limited is, for example, an environment in which the air density is low. That is, the environment in which the output of the engine <NUM> is limited is, for example, an environment in which an intake air amount of the engine <NUM> decreases. In addition, the environment in which the output of the engine <NUM> is limited can also be considered as an environment in which an amount of electric power generated by the engine <NUM> cannot be sufficiently ensured. The environment in which the output of the engine <NUM> is limited means, for example, a place exceeding a predetermined elevation, that is, a high altitude. In addition, the environment in which the output of the engine <NUM> is limited means, for example, a place of a predetermined temperature or higher, for example, a region in a tropical zone. However, in the first embodiment, for ease of description, an example, in which a case where the vehicle <NUM> reaches an elevation TH1 (see <FIG>) is determined as the environment in which the output of the engine <NUM> is limited, will be described. The elevation TH1 can be set to, for example, about <NUM>,<NUM>.

Specifically, the high altitude determination unit <NUM> acquires an atmospheric pressure from an atmospheric pressure sensor that measures an atmospheric pressure of air taken in by the engine <NUM>, and acquires a temperature from a temperature sensor that measures a temperature of the air taken in by the engine <NUM>. Then, the high altitude determination unit <NUM> obtains the air density at a place where the vehicle <NUM> is present based on the acquired atmospheric pressure and temperature, and determines whether the vehicle <NUM> has reached the elevation TH1 based on the air density. Specifically, when the air density is equal to or greater than a predetermined value, the high altitude determination unit <NUM> determines that the vehicle is not present at a high altitude, and when the air density is less than the predetermined value, the high altitude determination unit <NUM> determines that the vehicle is present at a high altitude. In the present embodiment, an example in which high altitude determination is performed using the atmospheric pressure and the temperature is described, but the high altitude determination may be performed using at least one of the atmospheric pressure and the temperature. A determination example will be described in detail with reference to <FIG>.

The K/D determination unit <NUM> determines whether the kickdown switch is turned on by a driver based on a signal from the kickdown switch, and outputs a determination result thereof to the driving torque limiting unit <NUM>.

The driving torque limiting unit <NUM> sets a limit value for limiting the driving force of the electric motor <NUM> based on the determination result output from the high altitude determination unit <NUM> and the determination result output from the K/D determination unit <NUM>, and outputs the limit value to the selection unit <NUM>. A method of setting the limit value of the driving force will be described in detail with reference to <FIG>, and <FIG>.

The selection unit <NUM> selects a driving force (torque command value of the electric motor <NUM>) required by the vehicle <NUM> based on the driving force output from the target driving force calculation unit <NUM>, the driving force output from the torque conversion unit <NUM>, and the limit value output from the driving torque limiting unit <NUM>, and outputs a selection result thereof to the inverter <NUM> and a power conversion unit <NUM>. Specifically, the selection unit <NUM> selects a minimum value among values output from the target driving force calculation unit <NUM>, the torque conversion unit <NUM>, and the driving torque limiting unit <NUM>. The selection unit <NUM> outputs the selected value to the power conversion unit <NUM> of the power generation system controller <NUM> as information indicating how much driving torque is required as the driving torque of the electric motor <NUM>.

The power generation system controller <NUM> includes a power conversion unit <NUM>, a high altitude determination unit <NUM>, a normal state charge/discharge map holding unit <NUM>, a high altitude charge/discharge map holding unit <NUM>, a map selection unit <NUM>, an addition unit <NUM>, a shift speed holding unit <NUM>, an α-line rotation speed calculation unit <NUM>, a minimum value selection unit <NUM>, a high altitude rotation speed calculation unit <NUM>, a rotation speed selection unit <NUM>, and a maximum value selection unit <NUM>.

The power conversion unit <NUM> converts the driving force (torque command value of the electric motor <NUM>) output from the selection unit <NUM> into a power value (output power value of the battery <NUM>), and outputs the converted power value to the addition unit <NUM>.

The high altitude determination unit <NUM> determines whether the vehicle <NUM> is traveling in an environment in which the output of the engine <NUM> is limited, and outputs a determination result thereof to the map selection unit <NUM> and the rotation speed selection unit <NUM>. A determination method thereof is the same as that of the high altitude determination unit <NUM>. In addition, in the power generation system controller <NUM>, the high altitude determination unit <NUM> may be omitted, and the determination result from the high altitude determination unit <NUM> may be used.

The normal state charge/discharge map holding unit <NUM> holds a normal state charge/discharge map to be used when it is determined that the vehicle <NUM> is in a place (normal place) other than the high altitude, and supplies the held charge/discharge map to the map selection unit <NUM>. The normal state charge/discharge map will be described in detail with reference to <FIG>.

The high altitude charge/discharge map holding unit <NUM> holds a high altitude charge/discharge map to be used when it is determined that the vehicle <NUM> is present at a high altitude, and supplies the held charge/discharge map to the map selection unit <NUM>. The high altitude charge/discharge map will be described in detail with reference to <FIG>.

The map selection unit <NUM> selects a charge/discharge map to be used for charging/discharging the battery <NUM> based on the determination result obtained by the high altitude determination unit <NUM>, and supplies the selected charge/discharge map to the addition unit <NUM>. Specifically, the map selection unit <NUM> selects a high altitude charge/discharge map when the high altitude determination unit <NUM> determines that the vehicle is present at a high altitude, and selects a normal state charge/discharge map when the high altitude determination unit <NUM> does not determine that the vehicle is present at a high altitude.

The addition unit <NUM> adds the power value output from the power conversion unit <NUM> and a value specified by the charge/discharge map output from the map selection unit <NUM>, and outputs an addition result to the α-line rotation speed calculation unit <NUM> and the high altitude rotation speed calculation unit <NUM>. That is, calculations by the α-line rotation speed calculation unit <NUM> and the high altitude rotation speed calculation unit <NUM> are performed in consideration of the power value (output power value of the battery <NUM>) corresponding to the torque command value of the electric motor <NUM> and the charge/discharge map corresponding to the result of the high altitude determination.

The shift speed holding unit <NUM> holds a shift speed (rotation speed for each vehicle speed) in which an optimum rotation speed of the engine <NUM> is set for each vehicle speed in consideration of the fuel efficiency and a generated sound of the engine <NUM>, and supplies the held shift speed to the minimum value selection unit <NUM>.

The α-line rotation speed calculation unit <NUM> calculates an α-line rotation speed based on an addition value output from the addition unit <NUM>, and outputs a calculation result thereof to the minimum value selection unit <NUM>. Here, the α-line indicates a rotation speed at which the engine <NUM> has the highest fuel efficiency for each engine output. That is, the rotation speed of the engine <NUM> with the highest fuel efficiency can be obtained for each addition value by the α-line.

The minimum value selection unit <NUM> selects a smaller value from the calculation result obtained by the α-line rotation speed calculation unit <NUM> and the shift speed held in the shift speed holding unit <NUM>, and supplies the selected value to the maximum value selection unit <NUM>. That is, the minimum value selection unit <NUM> selects a smaller value from the α-line rotation speed obtained in accordance with the addition value output from the addition unit <NUM> and the optimum rotation speed corresponding to the vehicle speed of the vehicle <NUM>.

The high altitude rotation speed calculation unit <NUM> calculates a rotation speed of the engine <NUM> for high altitude based on the addition value output from the addition unit <NUM>, and outputs a calculation result thereof to the rotation speed selection unit <NUM>. The rotation speed of the engine <NUM> for high altitude is a value used for obtaining a torque required at a high altitude at a rotation speed as low as possible in consideration of the environment at the high altitude.

The rotation speed selection unit <NUM> selects one from "<NUM>" and the calculation result obtained by the high altitude rotation speed calculation unit <NUM> as the rotation speed of the engine <NUM> that drives the generator <NUM> based on the determination result obtained by the high altitude determination unit <NUM>, and supplies the selected value to the maximum value selection unit <NUM>. Specifically, the rotation speed selection unit <NUM> selects the calculation result obtained by the high altitude rotation speed calculation unit <NUM> when it is determined that the vehicle is present at a high altitude, and selects "<NUM>" when it is not determined that the vehicle is present at a high altitude.

The maximum value selection unit <NUM> selects a larger value from the value selected by the minimum value selection unit <NUM> and the value selected by the rotation speed selection unit <NUM>, and outputs the selected value to the engine <NUM>. That is, the rotation speed of the engine <NUM> is controlled based on the value selected by the maximum value selection unit <NUM>.

<FIG> is a diagram illustrating an example of a normal state charge/discharge map. <FIG> is a diagram illustrating an example of a high altitude charge/discharge map. In <FIG>, the vertical axis represents an additional charge amount "kW" of the battery <NUM>, and the horizontal axis represents states of charge (SOC) "%". Here, the additional charge amount means an amount of electric power to be charged in the battery <NUM> among the electric power generated by the generator <NUM>. For example, when the value of the additional charge amount is a positive value, charging is performed, and when the value of the additional charge amount is a negative value, discharging is performed. That is, in the case of discharging, the electric motor <NUM> is driven by using the electric power of the battery <NUM>. In addition, <FIG> illustrate examples in which a lower limit value of the additional charge amount of the battery <NUM> is controlled. That is, <FIG> illustrates an example of a lower limit line of the additional charge amount in a normal state, and <FIG> illustrates an example of a lower limit line of the additional charge amount at a high altitude.

Regarding the charge/discharge map, although a plurality of maps are held in accordance with the vehicle speed, <FIG> illustrate an example of a map when the vehicle speed is V1 (kilometer per hour (kph)) for ease of description. V1 is, for example, a vehicle speed at the time of high speed traveling.

As illustrated in <FIG>, the addition unit <NUM> adds the value of the power conversion unit <NUM> (power value corresponding to the torque command value of the electric motor <NUM>) and the value of the charge/discharge map illustrated in <FIG>. In this case, the normal state charge/discharge map illustrated in <FIG> is used when it is not determined that the vehicle is present at a high altitude (normal state), and the high altitude charge/discharge map illustrated in <FIG> is used when it is determined that the vehicle is present at a high altitude. In addition, based on the information from the battery <NUM>, the value of the additional charge amount "kW" (vertical axis) corresponding to the current SOC of the battery <NUM> is to be added.

As illustrated in <FIG>, in a case where it is not determined that the vehicle is present at a high altitude (normal state) and the vehicle speed is V1, when the SOC is less than So1, the additional charge amount "kW" becomes a positive value. In addition, in the case where the vehicle is in the normal state and the vehicle speed is V1, when the SOC becomes So1 or more, the additional charge amount "kW" becomes a negative value. In this way, in the case where the vehicle is in the normal state and the vehicle speed is V1, the SOC of the battery <NUM> is set to be at least So1 or more.

As illustrated in <FIG>, in a case where it is determined that the vehicle is present at a high altitude and the vehicle speed is V1, when the SOC is less than So2, the additional charge amount "kW" becomes a positive value. In addition, in the case where it is determined that the vehicle is present at a high altitude and the vehicle speed is V1, when the SOC becomes So2 or more, the additional charge amount "kW" becomes a negative value. In this way, in the case where it is determined that the vehicle is present at a high altitude and the vehicle speed is V1, the SOC of the battery <NUM> is set to be at least So2 or more.

Here, as illustrated in <FIG>, So1 is a value smaller than So2. That is, the SOC at which the additional charge amount illustrated in <FIG> (vertical axis of <FIG>) is <NUM> kW is smaller than the SOC at which the additional charge amount illustrated in <FIG> (vertical axis of <FIG>) is <NUM> kW. In the present embodiment, the SOC (So1 illustrated in <FIG> and So2 illustrated in <FIG>) at which the additional charge amount illustrated in <FIG> is <NUM> kW will be referred to as an "SOC center". The SOC center (So1 and So2) can be set using various types of experimental data such as performances of the battery, the engine, and the generator.

In the present embodiment, an example in which only the lower limit value of the additional charge amount of the battery <NUM> is controlled is described, but the upper limit value of the additional charge amount of the battery <NUM> may be controlled. In addition, in the present embodiment, an example in which control is performed in two stages corresponding to whether it is determined that the vehicle is present at a high altitude is described, but the control may be performed in three or more stages corresponding to the elevation of the vehicle <NUM>.

<FIG> illustrate examples of limitations of the driving force when a high altitude determination threshold TH1 is used as a reference. In <FIG>, each relation is illustrated in a simplified manner for ease of description.

<FIG> is a diagram illustrating an example of a relation between an air density correction coefficient and an elevation [m]. The air density can be obtained based on the atmospheric pressure and the temperature. In addition, the elevation can be determined based on the air density. In <FIG>, for ease of description, the relation between the air density correction coefficient and the elevation [m] is simplified by a straight line AD1.

The air density correction coefficient is a value indicating a ratio of an air amount that can be taken in by the engine <NUM> when a case, where the elevation of the vehicle <NUM> is <NUM>, is set as "<NUM>". For example, when the engine <NUM> having a maximum output of <NUM> kw is taken as an example, an engine output of <NUM> kw is possible when the air density correction coefficient is <NUM>, and an engine output of <NUM> kw is possible when the air density correction coefficient is <NUM>. That is, as indicated by the straight line AD1, the value of the air density correction coefficient decreases as the elevation of the vehicle <NUM> increases.

As described above, in the first embodiment, an example in which it is determined that the vehicle is present at a high altitude when the vehicle <NUM> reaches the elevation TH1, for example, <NUM>,<NUM>, is described. That is, an example in which the elevation TH1 is set as the high altitude determination threshold TH1 is described. The high altitude determination threshold TH1 can be set using various types of experimental data such as the performances of the battery, the engine, and the generator corresponding to the elevation.

As described above, it is possible to provide the high altitude determination threshold TH1 for the air density, determine whether the vehicle is present at a high altitude, and perform control related to limiting the driving force of the electric motor <NUM> at the high altitude and ensuring the SOC of the battery <NUM>.

<FIG> is a diagram illustrating an example of a relation between an engine output [kw] and the elevation [m]. In <FIG>, for ease of description, the relation between the engine output [kw] and the elevation [m] is simplified by a straight line EP1.

As described above, an engine output corresponding to the elevation can be obtained by multiplying the maximum output of the engine <NUM> by the air density correction coefficient illustrated in <FIG>. That is, the engine output decreases as the elevation increases.

<FIG> is a diagram illustrating an example of a relation between a driving output upper limit [kw] of the electric motor <NUM> and the elevation [m].

As indicated by a line DL1 in <FIG>, when the elevation of the vehicle <NUM> is less than the high altitude determination threshold TH1, the driving force of the electric motor <NUM> is not limited. That is, a minimum value of driving forces obtained by the target driving force calculation unit <NUM> and the torque conversion unit <NUM> is set as the driving force of the electric motor <NUM>.

As indicated by a line DL3 in <FIG>, when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, the upper limit value of the driving force of the electric motor <NUM> is limited. A limit amount thereof is gradually increased until the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1 and reaches a threshold TH2 (here, TH1 < TH2). In addition, when the elevation of the vehicle <NUM> exceeds the threshold TH2, the limit amount thereof is set to be constant. As described above, by limiting the upper limit value of the driving force of the electric motor <NUM>, it is possible to prevent the SOC of the battery <NUM> from being excessively used.

Here, when the driver depresses the accelerator with an intention of acceleration, the kickdown switch is turned on. In this case, when the upper limit value of the driving force of the electric motor <NUM> is limited, the driver may not be able to obtain an intended acceleration feeling, and the driver may feel uncomfortable. Therefore, even in a case where the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, when the kickdown switch is turned on, the limitation of the driving force of the electric motor <NUM> is relaxed as indicated by a line DL2 in <FIG>.

In this way, when the kickdown switch is turned on, the driving force is limited by a driving force for kickdown pedaling. As a result, it is possible to reflect the intention of acceleration of the driver even at a high altitude. In addition, it is possible to determine the intention of acceleration of the driver using an existing kickdown switch, and use the determination result thereof for the control related to limiting the driving force of the electric motor <NUM>.

As described above, in the first embodiment, when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, the limit amount of the driving force of the electric motor <NUM> is set as indicated by the line DL3. However, when the kickdown switch is turned on, the limit amount of the driving force of the electric motor <NUM> is set based on the turn-on operation of the kickdown switch (example of the acceleration operation of the vehicle <NUM>) as indicated by the line DL2.

<FIG> is a diagram illustrating an example of a relation between the elevation [m] and a total value [kw] of the engine output and a battery output. The vertical axis in <FIG> indicates an output that can be used in driving the vehicle <NUM>. That is, an example of a relation in a case where information on outputs of the engine <NUM> and the battery <NUM> is viewed on a power axis is illustrated.

A straight line EB1 illustrated in <FIG> indicates a value obtained by adding the value of the straight line EP1 illustrated in <FIG> and the value of the line DL1 illustrated in <FIG>. Similarly, a line EB2 illustrated in <FIG> indicates a value obtained by adding the value of the straight line EP1 illustrated in <FIG> and the value of the line DL2 illustrated in <FIG>. Similarly, a line EB3 illustrated in <FIG> indicates a value obtained by adding the value of the straight line EP1 illustrated in <FIG> and the value of the line DL3 illustrated in <FIG>.

In addition, a dotted line EB4 illustrated in <FIG> indicates a value in a case where it is assumed that the limitation illustrated in <FIG> (limitation of the upper limit value of the driving force of the electric motor <NUM>) is not performed when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1.

A dotted line BT1 illustrated in <FIG> indicates an amount of electric power generated by the engine output corresponding to the straight line EP1 in <FIG>. In <FIG>, as indicated by a relation between the dotted line BT1 and the line EB3, when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1 and further reaches the vicinity of the threshold TH2, the value of the line EB3 becomes smaller than the value of the dotted line BT1. That is, by limiting the upper limit value of the driving force of the electric motor <NUM>, an amount of electric power that is not used for driving the electric motor <NUM> among the electric power that can be generated by the engine output is generated. That is, a reserve charging capacity is generated. Therefore, when the elevation of the vehicle <NUM> exceeds the threshold TH2 and the kickdown switch is not turned on, the battery <NUM> can be charged with the electric power generated by the engine output, and exhaustion of the battery <NUM> can be prevented. The exhaustion of the battery <NUM> means that the SOC of the battery <NUM> is less than a predetermined value. For example, when the SOC of the battery <NUM> is less than <NUM>%, it is determined that the SOC of the battery <NUM> is exhausted.

As described above, when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1 and further exceeds the threshold TH2, the battery <NUM> can be charged by setting the line EB3 to be lower than the dotted line BT1, and thus the SOC of the battery <NUM> can be prevented from being exhausted. However, when the upper limit value of the driving force of the electric motor <NUM> is limited such that the line EB3 is lower than the dotted line BT1 immediately after the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, the driver may feel uncomfortable due to a rapid change in the driving force. Therefore, until the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1 and reaches the threshold TH2, the upper limit value of the driving force of the electric motor <NUM> is gradually limited in accordance with the elevation of the vehicle <NUM> as indicated by the line EB3 in <FIG>. When the elevation of the vehicle <NUM> exceeds the threshold TH2, the upper limit value of the driving force of the electric motor <NUM> is limited such that the line EB3 is lower than the dotted line BT1.

Here, for example, in a case where the vehicle is traveling on an expressway in a state where the engine output is reduced at a high altitude, when an output supply from the battery <NUM> to the electric motor <NUM> is performed without limitation in accordance with a depression amount of the accelerator pedal by the driver, the battery <NUM> may be exhausted immediately. That is, when a driving output is performed without limitation even though the engine output is reduced at a high altitude, the SOC of the battery <NUM> may be exhausted immediately. In this way, when the battery <NUM> is exhausted, it is necessary to cover the output of the electric motor <NUM> only by the electric power generated by the engine <NUM>, and thus it is necessary to significantly limit the driving force of the electric motor <NUM>, which leads to a feeling of insufficient acceleration. For example, when such a limitation occurs on an expressway, the driver may feel dissatisfaction.

Therefore, in the first embodiment, the upper limit value of the driving force of the electric motor <NUM> is limited based on the high altitude determination threshold TH1. When the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, setting is made such that the reserve charging capacity is generated with reference to the vicinity of the threshold TH2. That is, when the elevation of the vehicle <NUM> is from the high altitude determination threshold TH1 to the vicinity of the threshold TH2, the setting is made such that the reserve charging capacity is not generated, and when the elevation of the vehicle <NUM> exceeds the threshold TH2, the setting is made such that the reserve charging capacity is generated. As described above, in the first embodiment, the control of the driving force of the electric motor <NUM> and the control of the reserve charging capacity of the battery <NUM> are changed based on the high altitude determination threshold TH1 and the threshold TH2.

As described above, in the first embodiment, the SOC center of the battery <NUM> can be shifted to a high level at a high altitude. Specifically, a high altitude charge/discharge map is prepared, and when it is determined that the vehicle is present at a high altitude, the charge/discharge map is switched to the high altitude charge/discharge map. That is, a target value of the SOC of the battery <NUM> is switched from a value for the level ground to a value for the high altitude for use.

In addition, in order to ensure the electric power generated by the battery <NUM>, when it is determined that the vehicle is present at a high altitude, the rotation speed for high altitude and the α-line rotation speed for high altitude are calculated, and the rotation speed required for the high altitude can be indicated. As described above, in the first embodiment, when it is determined that the vehicle is present at a high altitude, the driving force of the electric motor <NUM> is limited, and the SOC center of the battery <NUM> is shifted to a high level, and thus it is possible to ensure an SOC that can withstand the intention of acceleration at a high altitude.

In <FIG>, as indicated by the relation between the dotted line BT1 and the line EB2, even when the elevation of the vehicle <NUM> exceeds the threshold TH2, the value of the line EB2 is larger than the value of the dotted line BT1. That is, when the limitation of the upper limit value of the driving force of the electric motor <NUM> is relaxed, the electric power of the battery <NUM> may be required for driving the electric motor <NUM> in addition to the electric power generated by the engine output. When such a state continues, the battery <NUM> may be exhausted. However, when the kickdown switch is not turned on, the driving force of the electric motor <NUM> is limited, so that when the limitation is continued until the driver intends to accelerate the vehicle, the driver may have a feeling of insufficient acceleration. Therefore, when the kickdown switch is turned on, the control as indicated by the line EB2 is executed.

<FIG> is a diagram illustrating an example of a relation between a required driving force and a vehicle speed. In <FIG>, the vertical axis represents the required driving force "N", and the horizontal axis represents the vehicle speed "kph". Here, since the vehicle speed and the rotation speed of the electric motor <NUM> have a proportional relation, the example of the relation between the required driving force and the vehicle speed illustrated in <FIG> can also be understood as an example of a relation between the required driving force and the rotation speed of the electric motor <NUM>.

A line RD1 indicates an example of a relation between the required driving force and the vehicle speed in an environment in which it is not determined that the vehicle is present at a high altitude. Here, in a low rotation speed region R1 in which the rotation speed of the electric motor <NUM> is equal to or lower than a first rotation speed NR1, the required driving force takes a substantially constant value with respect to a change in the rotation speed of the electric motor <NUM>. Therefore, the region R1 can be referred to as a motor torque constant region.

In a middle rotation speed region R2 in which the rotation speed of the electric motor <NUM> is between the first rotation speed NR1 and a second rotation speed NR2 (here, NR1 < NR2), the output of the electric motor <NUM> takes a substantially constant value with respect to the change in the rotation speed of the electric motor <NUM>. Therefore, the region R2 can be referred to as a motor output constant region.

In a region R3 in which the rotation speed of the electric motor <NUM> exceeds the second rotation speed NR2, the required driving force and the output of the electric motor <NUM> rapidly decrease with respect to the change in the rotation speed of the electric motor <NUM>. That is, the second rotation speed NR2 corresponds to an upper limit rotation speed at which the electric motor <NUM> can exhibit a practical performance.

A line RD3 indicates an example of a relation between the required driving force and the vehicle speed when the elevation of the vehicle <NUM> is the high altitude determination threshold TH <NUM>. A line RD2 indicates an example of a relation between the required driving force and the vehicle speed when the kickdown switch is turned on in a case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH1.

As illustrated in <FIG>, until the vehicle speed reaches S6, the driving force is not limited regardless of whether it is determined that the vehicle is present at a high altitude. For example, a series hybrid vehicle can provide a comfortable acceleration feeling. In addition, it is considered that a frequency of depression of the accelerator pedal is often low on an expressway, and the frequency of depression of the accelerator pedal is relatively high in an urban area. In this way, when the vehicle travels at a vehicle speed less than S6, such as in an urban area or the like, appropriate acceleration is often required. Therefore, in an urban area or the like where the vehicle is assumed to travel at a relatively low speed, the driving force is set not to be limited in order to take advantage of characteristics of the series hybrid vehicle. That is, normal control is performed in the urban area where the vehicle speed is lower than a predetermined vehicle speed.

When the vehicle speed exceeds S6, the driving force is limited when it is determined that the vehicle is present at a high altitude. In <FIG>, S6 is indicated as a vehicle speed threshold TH11, and S8 is indicated as a vehicle speed threshold TH12. S6 is a vehicle speed when the vehicle travels in an urban area or the like, and S8 is a value higher than S6 by about several tens of (kph). S6 and S8 can be set using various types of experimental data such as the performances of the battery, the engine, and the generator corresponding to the elevation and the vehicle speed.

That is, in the motor torque constant region R1, the driving force is not limited regardless of whether it is determined that the vehicle is present at a high altitude. In addition, in the motor output constant region R2, the driving force is limited when it is determined that the vehicle is present at a high altitude.

A dotted line DD1 indicates a limit value of the driving force of the electric motor <NUM> when it is determined that the SOC of the battery <NUM> is exhausted in a case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH1. That is, the dotted line DD1 indicates a driving force when the electric motor <NUM> is driven using only the electric power generated by the engine output in a case where the SOC of the battery <NUM> is determined to be exhausted and the electric power of the battery <NUM> cannot be used.

In the example illustrated in <FIG>, even when the SOC of the battery <NUM> is determined to be exhausted in a case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH1, it is possible to ensure the driving force of the electric motor <NUM> up to the value of the dotted line DD1. In addition, by setting the relation between the required driving force and the vehicle speed of the vehicle <NUM> to be lower than the dotted line DD1, it is possible to charge the battery <NUM> with the electric power generated by the engine output.

As described above, in the first embodiment, when the elevation of the vehicle <NUM> is the high altitude determination threshold TH1, the driving force of the electric motor <NUM> is limited based on the electric power generated by the engine <NUM> under the environment thereof. In other words, the driving force of the electric motor <NUM> is limited such that the electric power generated by the engine <NUM> under the environment becomes larger than the required electric power of the electric motor <NUM>.

As described above, when the elevation of the vehicle <NUM> is the high altitude determination threshold TH1, the battery <NUM> can be charged by setting the relation between the required driving force and the vehicle speed of the vehicle <NUM> to be lower than the dotted line DD1, and thus the SOC of the battery <NUM> can be prevented from being exhausted. However, when the driving force of the electric motor <NUM> is limited such that the relation is lower than the dotted line DD1 immediately after the vehicle speed exceeds the vehicle speed threshold TH11, the driver may feel uncomfortable due to a rapid change in the driving force. Therefore, until the vehicle speed exceeds the vehicle speed threshold TH11 and reaches the vehicle speed threshold TH12, the driving force of the electric motor <NUM> is gradually limited in accordance with an increase in the vehicle speed as indicated by the line RD3 in <FIG>. When the vehicle speed exceeds the vehicle speed threshold TH12, the driving force of the electric motor <NUM> is limited such that the line RD3 is lower than the dotted line DD1.

However, in a case where the kickdown switch is turned on, even when the vehicle speed exceeds the vehicle speed threshold TH12, the limitation of the driving force of the electric motor <NUM> is relaxed as indicated by the line RD2.

As described above, in the first embodiment, when the elevation of the vehicle <NUM> exceeds the high altitude determination threshold TH1, the limit amount of the driving force of the electric motor <NUM> is set based on the vehicle speed of the vehicle <NUM> as indicated by the lines RD2 and RD3. As indicated by the line RD2, the limit amount of the driving force of the electric motor <NUM> is set based on the vehicle speed of the vehicle <NUM> and the acceleration operation (turn-on operation of the kickdown switch) of the vehicle <NUM>.

<FIG> is a flowchart illustrating an example of a processing procedure of a vehicle control process executed by a system for controlling the vehicle <NUM>. The processing procedure is executed based on a program stored in a storage unit (not illustrated) of the system for controlling the vehicle <NUM>.

In step S501, the high altitude determination unit <NUM> and the high altitude determination unit <NUM> perform high altitude determination. When it is determined that the vehicle is present at a high altitude, the process proceeds to step S505, and when it is determined that the vehicle is not at a high altitude, the process proceeds to step S502.

In step S502, the power generation system controller <NUM> sets a normal state target SOC center. Specifically, the map selection unit <NUM> selects the normal state charge/discharge map held in the normal state charge/discharge map holding unit <NUM>, and charging/discharging of the battery <NUM> is set based on the normal state charge/discharge map. The normal state target SOC center means an SOC center which is a target (SOC at which the additional charge amount becomes <NUM> kW) in the normal state.

In step S503, the power generation system controller <NUM> sets a normal state engine rotation speed. Specifically, the α-line rotation speed calculation unit <NUM> calculates an α-line rotation speed based on the normal state charge/discharge map. In addition, the rotation speed selection unit <NUM> selects "<NUM>". Then, the maximum value selection unit <NUM> selects a value selected by the minimum value selection unit <NUM> (the smaller value of the α-line rotation speed based on the normal state charge/discharge map and the optimum rotation speed corresponding to the vehicle speed of the vehicle <NUM>) as the engine rotation speed.

In step S504, the drive system controller <NUM> outputs an instruction for controlling the driving force of the vehicle <NUM> to the inverter <NUM> based on a value selected by the selection unit <NUM>. Since it is not determined that the vehicle is present at a high altitude, the selection unit <NUM> selects the minimum value of the driving forces obtained by the target driving force calculation unit <NUM> and the torque conversion unit <NUM>.

In step S505, the power generation system controller <NUM> sets a high altitude target SOC center. Specifically, the map selection unit <NUM> selects the high altitude charge/discharge map held in the high altitude charge/discharge map holding unit <NUM>, and the charging/discharging of the battery <NUM> is set based on the high altitude charge/discharge map. The high altitude target SOC center means an SOC center which is a target (SOC at which the additional charge amount becomes <NUM> kW) when it is determined that the vehicle is present at a high altitude. As described above, in the first embodiment, when it is determined that the vehicle is present at a high altitude, the target SOC center of the battery <NUM> is set to a larger value than that before it is determined that the vehicle is present at a high altitude.

In step S506, the power generation system controller <NUM> sets a high altitude engine rotation speed. Specifically, the α-line rotation speed calculation unit <NUM> calculates the α-line rotation speed based on the high altitude charge/discharge map. The minimum value selection unit <NUM> selects a smaller value from the α-line rotation speed based on the high altitude charge/discharge map and the optimum rotation speed corresponding to the vehicle speed of the vehicle <NUM>. In addition, the rotation speed selection unit <NUM> selects a rotation speed of the engine <NUM> for high altitude calculated by the high altitude rotation speed calculation unit <NUM>. Then, the maximum value selection unit <NUM> selects a larger value from the value selected by the minimum value selection unit <NUM> and the value selected by the rotation speed selection unit <NUM> (rotation speed of the engine <NUM> for high altitude) as the engine rotation speed.

In step S507, the K/D determination unit <NUM> performs K/D determination to determine whether the kickdown switch is turned on. When the kickdown switch is turned on, the process proceeds to step S509, and when the kickdown switch is not turned on, the process proceeds to step S508.

In step S508, the driving torque limiting unit <NUM> sets a limit value of the driving force for high altitude. Specifically, the limit value of the driving force for high altitude is set as indicated by the line DL3 in <FIG> and the line RD3 in <FIG>.

In step S509, the driving torque limiting unit <NUM> sets a driving force limit for high altitude to be released by a predetermined value. Specifically, the limit value of the driving force for high altitude when the kickdown switch is turned on is set as indicated by the line DL2 in <FIG> and the line RD2 in <FIG>.

In step S510, the selection unit <NUM> performs vehicle speed determination to determine whether the vehicle speed is equal to or higher than a predetermined value. When the vehicle speed is equal to or higher than the predetermined value, the selection unit <NUM> selects the limit value of the driving force for high altitude set by the driving torque limiting unit <NUM> in step S508 or S509, and the process proceeds to step S508. However, when the value set by the driving torque limiting unit <NUM> is larger than the value obtained by the target driving force calculation unit <NUM> or the torque conversion unit <NUM>, a minimum value of the driving forces obtained by the target driving force calculation unit <NUM> and the torque conversion unit <NUM> is selected. On the other hand, when the vehicle speed is less than the predetermined value, the selection unit <NUM> selects the minimum value of the driving forces obtained by the target driving force calculation unit <NUM> and the torque conversion unit <NUM>, and the process proceeds to step S504.

That is, when the vehicle speed is less than the predetermined value, for example, S6 (kph) illustrated in <FIG>, the driving force is not limited even when it is determined that the vehicle is present at a high altitude. However, regardless of whether the vehicle speed is less than the predetermined value, when it is determined that the vehicle is present at a high altitude, the high altitude target SOC center is set, and the high altitude engine rotation speed is set.

In step S511, the drive system controller <NUM> outputs an instruction for controlling the driving force of the vehicle <NUM> to the inverter <NUM> based on the value selected by the selection unit <NUM>.

Here, a technique of executing control for limiting the driving force of the vehicle after the SOC of the battery decreases is assumed. In this technique, electric power generated by the engine is used to increase the SOC of the battery after the SOC of the battery has decreased. In this way, since a part of the electric power generated by the engine is used to increase the SOC of the battery, the electric power to be used as the driving force when driving the electric motor is limited. That is, in order to increase the SOC of the battery, the driving force of the vehicle is further limited. In this way, when the driving force of the vehicle is significantly limited, the driving force of the vehicle greatly differs before and after the SOC of the battery decreases, and thus the driver may feel dissatisfaction.

On the other hand, in the first embodiment, when it is determined that the vehicle is present at a high altitude, the control for limiting the driving force of the vehicle <NUM> is executed even in a state where the SOC of the battery <NUM> does not decrease. That is, when it is determined that the vehicle is present at a high altitude, the control for limiting the driving force of the vehicle <NUM> is executed regardless of the SOC of the battery <NUM>. As a result, a distance over which the vehicle can travel at a high output can be extended. That is, since the driving force of the vehicle <NUM> is limited even in a state where the SOC of the battery <NUM> is large, the decrease in the SOC of the battery <NUM> can be made more gradual than in the above-described technique. Accordingly, a time until the vehicle gets into a low SOC state in which the driving force of the vehicle <NUM> is significantly limited can be extended, and the distance (time) over which the vehicle <NUM> can travel at a high output can be extended.

In the first embodiment, when it is determined that the vehicle is present at a high altitude and there is no intention of acceleration (that is, when the kickdown switch is not turned on), the driving force of the electric motor <NUM> is limited. On the other hand, when it is determined that the vehicle is present at a high altitude and there is an intention of acceleration (that is, when the kickdown switch is turned on), the limitation of the driving force of the electric motor <NUM> is relaxed. In this way, while responding to the intention of acceleration of the driver, it is possible to extend the time until the vehicle gets into the low SOC state in which the driving force of the vehicle <NUM> is significantly limited, and it is possible to extend the distance (time) over which the vehicle <NUM> can travel at a high output.

As described above, according to the first embodiment, in a case where the vehicle <NUM> is present at a high altitude, the driving force of the electric motor <NUM> can be limited in accordance with a decrease in the engine output. The SOC of the battery <NUM> can be maintained by limiting the driving force of the electric motor <NUM>. The SOC center of the battery <NUM> can be shifted to a higher level by switching to the high altitude charge/discharge map or by calculating the high altitude engine rotation speed. In addition, whether the driver has an intention of acceleration is determined, and when the driver has the intention of acceleration, the limitation of the driving force of the electric motor <NUM> can be relaxed. Thus, when the vehicle <NUM> is present at a high altitude, it is possible to perform control such that a minimum vehicle speed continues for a long time by depressing the accelerator pedal while preventing a decrease in the SOC of the battery <NUM>.

As described above, according to the first embodiment, even in an environment in which the output of the engine <NUM> is limited, a decrease in the SOC of the battery <NUM> can be prevented and the travel distance of the vehicle <NUM> can be extended.

The method for controlling a vehicle according to the first embodiment is a method for controlling the vehicle <NUM>, the vehicle <NUM> includes the electric motor <NUM> that drives the vehicle <NUM>, the engine <NUM> that drives the generator <NUM> that generates electric power to be supplied to the electric motor <NUM>, and the battery <NUM> that is chargeable by the generator <NUM> and electrically connected to the electric motor <NUM>. This control method includes a control step (steps S505 to S511) of limiting the driving force of the electric motor <NUM> when the vehicle <NUM> is traveling in an environment in which the output of the engine <NUM> is limited.

According to such a method for controlling a vehicle, the driving force of the electric motor <NUM> is limited in accordance with a decrease in the engine output at a high altitude, so that a decrease in the SOC of the battery <NUM> can be prevented and the travel distance of the vehicle <NUM> can be extended.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S510 and S511), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the limit amount of the driving force of the electric motor <NUM> is set based on the vehicle speed of the vehicle <NUM>.

According to such a method for controlling a vehicle, the driving force of the electric motor <NUM> can be adjusted based on the vehicle speed of the vehicle <NUM>, and a comfortable operation environment can be provided to the driver.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S510 and S511), in a case where the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the driving force of the electric motor <NUM> is limited when the vehicle speed of the vehicle <NUM> is higher than a predetermined value (for example, S6 (kph) illustrated in <FIG>), and the driving force of the electric motor <NUM> is not limited when the vehicle speed of the vehicle <NUM> is lower than the predetermined value.

According to such a method for controlling a vehicle, the driving force of the electric motor <NUM> is not limited in an urban area or the like where the vehicle is assumed to travel at a low speed, and the driving force of the electric motor <NUM> is limited on an expressway or the like where the vehicle is assumed to travel at a high speed. In this way, the driving force of the electric motor <NUM> can be adjusted based on the vehicle speed of the vehicle <NUM>.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S507 and S509), in a case where the vehicle <NUM> travels in the environment in which the output of the engine <NUM> is limited and the vehicle speed of the vehicle <NUM> is higher than the predetermined value, when a turn-on operation (example of a predetermined acceleration operation) of the kickdown switch is performed, the limitation of the driving force of the electric motor <NUM> is relaxed.

According to such a method for controlling a vehicle, whether the driver has an intention of acceleration can be determined, and the driving force of the electric motor <NUM> can be adjusted based on the intention of acceleration of the driver and the vehicle speed.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S507 and S509), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the limit amount of the driving force of the electric motor <NUM> is set based on the turn-on operation (example of the predetermined acceleration operation) of the kickdown switch of the vehicle <NUM>.

According to such a method for controlling a vehicle, whether the driver has an intention of acceleration can be determined, and the driving force of the electric motor <NUM> can be adjusted.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S507 to S511), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the limit amount of the driving force of the electric motor <NUM> is set based on the vehicle speed of the vehicle <NUM> and the acceleration operation of the vehicle <NUM>.

In the method for controlling a vehicle according to the first embodiment, in the control step (step S505), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the SOC at which the additional charge amount of the battery <NUM> becomes <NUM> kW is set to a larger value than that before the vehicle <NUM> travels in the environment. That is, the target SOC center of the battery <NUM> is set to be higher than that before the vehicle <NUM> travels in the environment. The SOC at which the additional charge amount of the battery <NUM> becomes <NUM> kW includes So1 illustrated in <FIG> and So2 illustrated in <FIG>, and is also referred to as an SOC center.

According to such a method for controlling a vehicle, in order to prevent the SOC exhaustion of the battery <NUM> at a high altitude, the driving force of the electric motor <NUM> is limited and the SOC center of the battery <NUM> is controlled to be high at the same time in accordance with a decrease in the engine output at a high altitude.

In the method for controlling a vehicle according to the first embodiment, in the control step (step S508), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the driving force of the electric motor <NUM> is limited based on the electric power generated by the engine <NUM> under the environment.

According to such a method for controlling a vehicle, since the amount of electric power generated by the engine <NUM> decreases at a high altitude, by setting an output value of the electric motor <NUM> based on a maximum output value of the engine <NUM> at the high altitude, a decrease in the SOC of the battery <NUM> can be prevented and the travel distance of the vehicle <NUM> can be extended.

In the method for controlling a vehicle according to the first embodiment, in the control step (step S508), the driving force of the electric motor <NUM> is limited such that the electric power generated by the engine <NUM> under the environment in which the output of the engine <NUM> is limited is larger than the required electric power of the electric motor <NUM>.

According to such a method for controlling a vehicle, since the amount of electric power generated by the engine <NUM> decreases at a high altitude, by setting the output value of the electric motor <NUM> to be smaller than the maximum output value of the engine <NUM> at the high altitude, a decrease in the SOC of the battery <NUM> can be prevented and the travel distance of the vehicle <NUM> can be extended.

In the method for controlling a vehicle according to the first embodiment, in the control step (steps S510 and S511), when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited, the driving force is limited in the output constant region of the electric motor <NUM>.

According to such a method for controlling a vehicle, a comfortable operation environment can be provided for the driver by adjusting the driving force of the electric motor <NUM> in the output constant region.

The system for controlling the vehicle <NUM> according to the first embodiment includes: the electric motor <NUM> that drives the vehicle <NUM>; the engine <NUM> that drives the generator <NUM> that generates electric power to be supplied to the electric motor <NUM>; the battery <NUM> that is chargeable by the generator <NUM> and electrically connected to the electric motor <NUM>; and the drive system controller <NUM> (example of a controller) that controls the electric motor <NUM>. The drive system controller <NUM> limits the driving force of the electric motor <NUM> when the vehicle <NUM> is traveling in the environment in which the output of the engine <NUM> is limited.

According to such a system for controlling the vehicle <NUM>, the driving force of the electric motor <NUM> is limited in accordance with a decrease in the engine output at a high altitude, so that a decrease in the SOC of the battery <NUM> can be prevented and the travel distance of the vehicle <NUM> can be extended.

In the first embodiment, an example in which the upper limit value of the driving force of the electric motor is limited when the elevation of the vehicle exceeds the high altitude determination threshold TH1 is described. That is, an example in which the control when it is determined that the vehicle is present at a high altitude is performed in one stage is described. However, the control may be performed by setting a plurality of high altitude determination thresholds in advance, and executing limitation corresponding to each high altitude determination threshold at a timing when the elevation of the vehicle exceeds these high altitude determination thresholds. Therefore, in the second embodiment, an example in which the upper limit value of the driving force of the electric motor is limited by setting a plurality of high altitude determination thresholds will be described. The second embodiment is an example in which a part of the first embodiment is modified, and illustration and description are partially omitted for a part common to the first embodiment.

<FIG> is a diagram illustrating an example of a relation between a required driving force and a vehicle speed according to the second embodiment. <FIG> is an example in which a part of <FIG> is modified, and the same reference numerals are given and a part of the description thereof is omitted for a part common to <FIG>.

In the second embodiment, an example in which two high altitude determination thresholds, that is, the high altitude determination threshold TH1 (for example, about <NUM>,<NUM>) and a high altitude determination threshold TH3 (for example, about <NUM>,<NUM>) are set is described.

A line RD5 indicates an example of a relation between the required driving force and the vehicle speed in a case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH3. A line RD4 indicates an example of a relation between the required driving force and the vehicle speed when the kickdown switch is turned on in the case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH3.

As illustrated in <FIG>, in a case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH3, when the vehicle speed exceeds the vehicle speed threshold TH11, the driving force of the electric motor <NUM> is limited. However, the limit value in the case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH3 is set to a value smaller than the limit value in the case where the elevation of the vehicle <NUM> is the high altitude determination threshold TH1.

In the second embodiment, an example in which the upper limit value of the driving force of the electric motor is limited by setting the two high altitude determination thresholds TH1 and TH3 is described, but three or more high altitude determination thresholds may be set to limit the upper limit value of the driving force of the electric motor.

As described above, according to the second embodiment, the driving force of the electric motor can be limited in accordance with a high altitude degree at a high altitude.

In the first and second embodiments, the vehicle <NUM> equipped with the kickdown switch has been described as an example. The first and second embodiments can also be applied to a vehicle in which a kickdown switch is not mounted. Therefore, in the third embodiment, a vehicle in which a kickdown switch is not mounted will be described as an example. The third embodiment is an example in which a part of the first and second embodiments is modified, and illustration and description are partially omitted for a part common to the first and second embodiments.

In the vehicle according to the third embodiment, the K/D determination unit <NUM> illustrated in <FIG> is omitted. In the third embodiment, when the driving force of the electric motor <NUM> is limited, the limitation considering the kickdown switch is not relaxed. Specifically, the limit values corresponding to the line DL2 illustrated in <FIG>, the line EB2 illustrated in <FIG>, the line RD2 illustrated in <FIG>, and the line RD4 illustrated in <FIG> are not selected. Therefore, a decrease in the SOC of the battery <NUM> can be further prevented and the travel distance of the vehicle <NUM> can be further extended.

<FIG> is a flowchart illustrating an example of a processing procedure of a vehicle control process executed by a system for controlling a vehicle according to the third embodiment. The example illustrated in <FIG> is an example in which a part of <FIG> is modified, and the same reference numerals are given and a part of the description thereof is omitted for a part common to <FIG>. Specifically, <FIG> is different from <FIG> in that steps S507 and S509 illustrated in <FIG> are omitted.

As described above, according to the third embodiment, in an environment in which the output of the engine <NUM> is limited for a vehicle on which the kickdown switch is not mounted, a decrease in the SOC of the battery <NUM> can be further prevented and the travel distance of the vehicle <NUM> can be further extended.

Claim 1:
A method for controlling a vehicle (<NUM>), wherein:
- the vehicle (<NUM>) includes:
- an electric motor (<NUM>) configured to drive the vehicle (<NUM>),
- an engine (<NUM>) configured to drive a generator (<NUM>) that generates electric power to be supplied to the electric motor (<NUM>), and
- a battery (<NUM>) configured to be charged by the generator (<NUM>) and electrically connected to the electric motor (<NUM>), and
- the method comprises a control step of limiting a driving force of the electric motor (<NUM>) in a case where the vehicle (<NUM>) is traveling in a place exceeding a predetermined elevation or a place of a predetermined temperature or higher, in which an output of the engine (<NUM>) is limited, and
- in the control step, in a case where the vehicle (<NUM>) is traveling in the place exceeding the predetermined elevation or in the place of the predetermined temperature or higher, the driving force of the electric motor (<NUM>) is limited and a limit amount of the driving force of the electric motor (<NUM>) is set based on a vehicle speed of the vehicle (<NUM>) when the vehicle speed of the vehicle (<NUM>) is equal to or higher than a predetermined value, and the driving force of the electric motor (<NUM>) is not limited when the vehicle speed of the vehicle (<NUM>) is lower than the predetermined value.