JP5824650B2 - Regenerative braking control device for vehicle - Google Patents

Description

  The present invention relates to a regenerative braking control device for a vehicle that converts kinetic energy when the vehicle is braked into electric energy and collects it in a storage battery.

  2. Description of the Related Art In recent years, electric vehicles (EVs) and hybrid vehicles (Hybrid vehicles) have attracted attention for the realization of a low-carbon society. Such electric vehicles and hybrid vehicles perform regenerative braking.

  In this regenerative braking, an electric motor normally used as a driving force is operated as a generator, so that energy consumed as heat during vehicle deceleration can be recovered as electric energy. The recovered energy is stored in the storage battery and reused for the driving force and electric load of the vehicle. This reuse improves the “electricity cost”, which is the travel distance per unit capacity of the storage battery in the electric vehicle.

  Moreover, in the hybrid vehicle, the “electricity cost” is improved by the reuse, and this improvement in the electric cost leads to improvement in the fuel consumption of the vehicle.

  By the way, when the vehicle is traveling uphill (hereinafter referred to as “when traveling uphill”), compared to when the vehicle is traveling on a flat road (hereinafter referred to as “when traveling on a flat road”), In addition to running resistance and regenerative braking, gradient resistance is added to the vehicle. If the regenerative braking force is applied too much while the vehicle is traveling uphill, the vehicle speed will drop more than the driver's request, causing the driver to step on the accelerator, which worsens the vehicle's power consumption or fuel consumption. .

  On the other hand, when the vehicle is traveling downhill (hereinafter referred to as “downhill traveling”), the acceleration force associated with the gravitational acceleration is applied compared to when traveling on a flat road, so a large regenerative braking force is applied. Added.

  Therefore, compared to the regenerative braking force when the vehicle is traveling on a flat road, the regenerative braking force is reduced when the vehicle is traveling uphill, and the regenerative braking force is increased when the vehicle is traveling downhill. Good.

  As a conventional technique for performing such control, there is a regenerative braking control device for a vehicle that controls a regenerative braking force according to a road gradient on which the vehicle travels (see, for example, Patent Document 1).

  Specifically, a conventional regenerative braking control device for a vehicle detects the torque of an electric motor that is used as a driving force of the vehicle, and determines the tire to be transmitted to the tire from the transmission efficiency of the driving force and the tire moving radius. A driving force or a tire braking force F is calculated. When the acceleration resistance accompanying the acceleration of the vehicle is Ra and the running resistance is R, the tire driving force (tire braking force) F is expressed as F = Ra + R in terms of vector, and the running resistance R is R = F−Ra. It is expressed.

  Further, the running resistance R is represented by R (θ, V) as a function of the road gradient θ and the vehicle speed V, and includes rolling resistance, air resistance, turning resistance, and gradient resistance. The rolling resistance, air resistance, and turning resistance are calculated based on the vehicle weight, which is the vehicle specification, and the rolling resistance coefficient calculated based on the vehicle specification, the vehicle front projected area, the air resistance coefficient, etc. The gradient resistance is estimated by subtracting from R (θ, V).

Vehicle specifications are elements common to vehicle types (vehicle weight, total length, total width, total height, gear ratio, final gear ratio, tire radius, etc.) and do not include error factors specific to each vehicle. It is.

  As described above, the conventional regenerative braking control device for a vehicle estimates the gradient resistance by calculation based on the balance of the force relating to the traveling of the vehicle, and controls the regenerative braking force according to the road gradient on which the vehicle travels.

International Publication No. 97/10966

  However, since the conventional vehicle regenerative braking control apparatus estimates the gradient resistance based on vehicle specifications, an error factor specific to each vehicle is not taken into consideration. For example, error factors specific to each vehicle include a change in vehicle weight that varies depending on the number of passengers and the load of the vehicle, or a change in rolling resistance coefficient due to a change in tire air pressure. If the rolling resistance coefficient changes due to an error factor unique to each vehicle, the running resistance changes as a result.

  When regenerative braking is performed by obtaining the gradient resistance based on the vehicle specifications, the regenerative braking force is uniformly generated based on the vehicle specifications. , Braking feeling when the driver applies the brakes (feeling the driver feels when the vehicle decelerates after the brakes are applied), or braking feeling (natural when the brakes are not applied and the accelerator is not pressed) The driver feels when decelerating) changes.

  The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a regenerative braking control device for a vehicle that can reduce variation in braking feeling or braking feeling with respect to a driver.

In order to achieve the above object, a regenerative braking control device for a vehicle according to the present invention is an electric motor that generates regenerative braking force by converting kinetic energy, which is coupled to an axle of a drive wheel of a vehicle and decelerating, into electrical energy, A regenerative braking control device for a vehicle comprising a storage battery that is mounted on the vehicle and stores electric energy converted by the electric motor, and a road inclination angle calculation unit that calculates a gradient of a road on which the vehicle is traveling, When it is determined that the vehicle is traveling on a flat road based on the road gradient calculated by the road inclination angle calculation unit, a driving resistance is calculated based on the acceleration of the vehicle, and based on the calculated driving resistance calculating a reference value of the regenerative braking force during running on a flat road of the vehicle, and a control unit that controls the regenerative braking force of said motor based on a regenerative braking force obtained by this calculation, the control unit, the travel resistance Update the reference value of the regenerative braking force each time is calculated, and based on the reference value of the regenerative braking force during running on a flat road that updated, the regenerative braking force of said motor when said vehicle is traveling uphill, Alternatively, control is performed to set the regenerative braking force of the electric motor when traveling downhill according to the road gradient calculated by the road inclination angle calculation unit .

  The regenerative braking control device for a vehicle according to the present invention calculates a running resistance when the vehicle is actually running on a flat road. An error factor peculiar to each vehicle is added to this running resistance, and the regenerative braking control device for a vehicle according to the present invention calculates a regenerative braking force during flat road running based on this running resistance. Based on the power, the regenerative braking force when the vehicle is traveling uphill or the regenerative braking force when traveling downhill is controlled.

  In this way, the running resistance can reduce the brake feeling or the variation in braking feeling for the driver by adding an error factor specific to each vehicle.

The block diagram of the regenerative braking control apparatus for vehicles in one embodiment of this invention The figure explaining each axis of the acceleration which an acceleration sensor detects The figure explaining the method of calculating the inclination angle with respect to the road of the vehicle The figure explaining the angular velocity of the yaw rotation direction of a gyro sensor The flowchart explaining operation | movement of the regenerative braking control apparatus for vehicles in one embodiment of this invention. Diagram for explaining the relationship between vehicle speed and running resistance Diagram for explaining the relationship between motor rotation speed and regenerative torque The flowchart explaining operation | movement of the regenerative braking control apparatus for vehicles in one embodiment of this invention. Diagram for explaining the relationship between road inclination angle and regenerative torque increase / decrease coefficient

  Hereinafter, a regenerative braking control device for a vehicle according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a regenerative braking control device for a vehicle according to an embodiment of the present invention. FIG. 2 is a diagram for explaining each axis of acceleration detected by the acceleration sensor, and FIG. 3 is a diagram for explaining a method of calculating an inclination angle of the vehicle with respect to the road. FIG. 4 is a diagram illustrating the angular velocity in the yaw rotation direction of the gyro sensor.

  As shown in FIG. 1, a regenerative braking control device 1 for a vehicle is a device mounted on a vehicle, and is connected to an axle of a drive wheel of the vehicle to convert kinetic energy when the vehicle is decelerated by a regenerative braking force into electric energy. The electric motor 2 that converts the electric energy into the storage battery and outputs the electric energy is stored in the storage battery 3.

  The magnitude of the regenerative braking force generated by the electric motor 2 is controlled by the control unit 4. The control unit 4 is based on the outputs of the acceleration sensor 5, the vehicle speed detection unit 6, the road inclination angle calculation unit 7, the vehicle turning detection unit 8, the accelerator opening detection unit 9, and the brake depression amount detection unit 10. A running resistance force (hereinafter simply referred to as “running resistance”) is calculated, and the regenerative braking force is controlled based on the running resistance. These calculation methods will be described in detail later.

  Hereinafter, each part will be described in detail.

The electric motor 2 is connected to an axle of a driving wheel of the vehicle, and is used as a generator that converts kinetic energy when the vehicle decelerates by regenerative braking force into electric energy and outputs the electric energy. The electric motor 2 is also used as a traveling motor for rotating the axle. Switching between the use of the electric motor 2 as a generator or the use of a traveling motor is performed by the control unit 4.

  When the rotor of the electric motor 2 is rotated by an external force (the rotational force of the axle of the driving wheel of the vehicle), the electric motor 2 serves as a generator and generates regenerative power. Specifically, when the rotor of the electric motor 2 is rotated by an external force, an electromotive force is generated at both ends of the armature coil of the electric motor 2 due to the interaction of these magnetic fields, and a power generation operation is performed. The electrical energy generated by this power generation operation is output to the storage battery 3.

When the electric motor 2 is performing a power generation operation, the torque required for power generation acts as a torque in a direction to stop the rotation of the drive wheels of the vehicle, thereby generating a braking force (regenerative braking force).

  The control unit 4 controls how much regenerative power is generated, that is, how much regenerative braking force is generated. When the driver depresses the brake pedal to a predetermined level, the control unit 4 controls the regenerative braking force according to the degree of depressing. The control unit 4 adjusts the current flowing in the armature coil on the rotor side of the motor 2 or the field coil on the stator side, and adjusts the rotating magnetic field or the magnitude of the field to regenerate. Control power.

  The storage battery 3 stores electrical energy output from the electric motor 2. The stored electrical energy is stepped down by a DC / DC converter (not shown) and supplied to in-vehicle devices such as audio devices and navigation devices. The stored electrical energy is converted into alternating current by an inverter (not shown) and supplied to an electric compressor for an air conditioner. For the storage battery 3, for example, a nickel metal hydride battery, a lithium ion battery, or a high-capacity capacitor can be used.

  The control unit 4 is based on the outputs of the acceleration sensor 5, the vehicle speed detection unit 6, the road inclination angle calculation unit 7, the vehicle turning detection unit 8, the accelerator opening detection unit 9, and the brake depression amount detection unit 10. The running resistance is calculated, and the regenerative braking force is controlled based on the running resistance.

  The control unit 4 includes a CPU or MPU and ROM / RAM / etc. The CPU or MPU executes various programs, outputs control signals, and the like by executing programs stored in a ROM (not shown).

  The functions performed by the control unit 4 include a “running resistance calculation function”, a “regenerative torque reference value update function”, and a “regenerative braking force calculation function”. Details of these functions will be described later.

  The acceleration sensor 5 detects the acceleration of the vehicle. Each axis of acceleration detected by the acceleration sensor will be described with reference to FIG. The acceleration sensor 5 is an acceleration sensor that detects acceleration in each axial direction with respect to two directions shown in FIG.

  The acceleration sensor 5 detects the acceleration of the longitudinal detection axis (Xb axis in FIG. 2) and the acceleration of the lateral detection axis (Yb axis in FIG. 2).

  The acceleration in the Xb-axis direction detected by the acceleration sensor 5 is output to the road inclination angle calculation unit 7 and used to calculate the road inclination angle. Further, the acceleration in the Xb-axis direction is output to the control unit 4 and is also used for calculating the running resistance during vehicle deceleration.

  The vehicle speed detector 6 detects the speed of the vehicle. As a vehicle speed calculation method, for example, there is a method using a vehicle speed pulse, or a method using an engine speed and a gear ratio.

  The road inclination angle calculation unit 7 calculates the inclination angle θ of the vehicle with respect to the road based on the acceleration detected by the acceleration sensor 5 and the vehicle speed detected by the vehicle speed detection unit 6.

  Specifically, the vehicle inclination angle θ is calculated from the acceleration Ax in the vehicle traveling direction and the acceleration Acc accompanying the movement of the vehicle. The acceleration Acc accompanying the movement of the vehicle is calculated by differentiating the vehicle speed detected by the vehicle speed detector 6 with respect to time.

  FIG. 3 is a diagram for explaining a method of calculating the inclination angle of the vehicle with respect to the road. As shown in FIG. 3, when the acceleration of the traveling direction component of the gravitational acceleration G is Ag, it can be expressed as Ag = G * sin θ. On the other hand, the acceleration Acc accompanying the movement of the vehicle can be expressed as Acc = Ax−Ag. If Ag is eliminated from these two equations, sin θ = (Ax−Acc) / G. The inclination angle θ can be obtained by solving this equation for θ.

  The vehicle turning detection unit 8 determines whether or not the vehicle is turning. As a method for determining whether or not the vehicle is turning, for example, there are the following methods.

  As a first method, there is a method using a steering angle sensor (not shown). Based on the steering angle of the steering wheel detected by the steering angle sensor, it can be determined whether or not the vehicle is turning.

  As a second method, there is a method using a gyro sensor. The gyro sensor detects an angular velocity of rotation about a predetermined axis of the vehicle.

  As an example of the gyro sensor, for example, an angular velocity of rotation about the vehicle longitudinal axis (roll rotational direction), an angular velocity of rotation about the vertical axis of the vehicle (yaw rotational direction), and the left and right sides of the vehicle There is one that detects an angular velocity of rotation about the direction axis (pitch rotation direction).

  In particular, as shown in FIG. 4, the vehicle turning detection unit 8 can determine whether the vehicle is turning based on a change in angular velocity (Wbz) in the yaw rotation direction of the gyro sensor.

  As a third method, there is a method using the acceleration of the left-right direction detection axis (Yb axis in FIG. 2) of the acceleration sensor 5. When the vehicle is turning, the acceleration Ay in the Yb axis direction is detected. On the other hand, when the vehicle is not turning, the acceleration Ay in the Yb-axis direction is substantially zero. When the acceleration Ay exceeds a predetermined value and the vehicle is turning, the vehicle turning detection unit 8 can determine that the vehicle is not turning when the acceleration is less than the predetermined value.

  The accelerator opening detector 9 detects the amount of depression of the accelerator pedal. It is only necessary to set at least a predetermined threshold and determine whether or not the accelerator pedal has been depressed.

  The brake depression amount detection unit 10 detects the depression amount of the brake pedal when the driver applies the brake. The amount of depression can be calculated based on the distance between the brake pedal and the floor, for example, based on the output of an infrared sensor attached to the brake pedal. It is also possible to detect the amount of depression by detecting negative pressure and hydraulic pressure (depression force) generated by depressing the brake pedal.

  The memory | storage part 11 memorize | stores various information, For example, non-volatile memory elements, such as a hard disk and flash memory, can be used. The storage unit 11 reads information stored by the control unit 4. In the storage unit 11, new information is written by the control unit 4.

  As information stored in the storage unit 11, vehicle specifications of the vehicle, information indicating a relationship between a vehicle speed and a running resistance, which will be described later, and information regarding a relationship between a motor rotational speed and a regenerative torque which will be described later are stored in advance.

In addition, the storage unit 11 stores, as information that is updated as needed by the control unit 4, information related to the relationship between vehicle speed and running resistance, which will be described later, and information related to values updated based on driving resistance, which will be described later. To do.

  The notification unit 12 notifies the driver when the running resistance calculated by the control unit 4 is greater than a predetermined value. For example, it is configured by a speaker for notification by sound, or a screen such as an LED or liquid crystal display for notification by light.

  The processing operation of the regenerative braking control device for a vehicle configured as described above will be described. First, the running resistance calculation function and the regenerative torque reference value update function of the control unit 4 will be described with reference to FIGS. Thereafter, the regenerative braking force calculation function of the control unit 4 will be described with reference to FIGS. 8 and 9.

FIG. 5 is a flowchart for explaining the operation of the regenerative braking control device for a vehicle in one embodiment of the present invention.
6 is a diagram for explaining the relationship between the vehicle speed and the running resistance, and FIG. 7 is a diagram for explaining the relationship between the motor rotation speed and the regenerative torque.

  First, in S001, the control unit 4 acquires the inclination angle θ of the vehicle with respect to the road calculated by the road inclination angle calculation unit 7.

  After S001, the control unit 4 determines whether or not the road inclination angle θ acquired in S001 is zero (S002). If the inclination angle θ is not zero (NO in S002), the control unit 4 returns the process to S001. When the inclination angle θ is zero (YES in S002), the control unit 4 advances the process to S003. The control unit 4 determines that the road inclination angle θ is zero if the road inclination angle θ is within ± 0.1 deg. The case where the control unit 4 determines that the road inclination angle θ is zero, that is, when traveling on a flat road.

  When the vehicle is traveling on a flat road (YES in S002), the control unit 4 determines whether or not the accelerator pedal is depressed based on the output of the accelerator opening degree detection unit 9 (S003).

  Following S003, the control unit 4 calculates the running resistance in S004 or S005 (running resistance calculation function which is one of the functions of the control unit 4). This running resistance calculation function will be described with reference to FIG.

  The calculation method of running resistance differs depending on whether the vehicle is accelerating or decelerating. The calculation of the running resistance when the vehicle is decelerating (NO in S003) is S004, and the calculation of the running resistance when the vehicle is accelerating (YES in S003) is S005. Details will be described below.

  When the accelerator opening degree detection unit 9 determines that the accelerator is OFF, the tire driving force (hereinafter, tire braking force F) is set as the running resistance. Here, the tire braking force F is the driving force transmitted from the driving source (engine or electric motor) to the tire of the vehicle. The tire braking force F is calculated by vehicle weight W × acceleration Ax. Since the vehicle is decelerating, the acceleration Ax is a negative value. However, this calculation method is when the brake pedal is not depressed.

  Even when the accelerator opening degree detection unit 9 determines that the accelerator is OFF, when the brake pedal is depressed, the control unit 4 calculates the running resistance from the tire braking force F and the mechanical brake amount (S004).

Here, the mechanical brake amount represents the degree of braking by converting kinetic energy such as a disc brake or a drum brake into thermal energy. The mechanical brake amount represents the degree of braking by the brake, in other words, it can be measured as an acceleration resistance force (acceleration resistance Rb) based on acceleration.

  The running resistance R can be calculated by subtracting the acceleration resistance Rb from the tire braking force F (R = F−Rb).

  As the vehicle acceleration Ax, the acceleration detected by the acceleration sensor 5 or the time differential value of the vehicle speed detected by the vehicle speed detector 6 is used. When the road inclination angle θ is zero, the acceleration detected by the acceleration sensor 5 is equal to the time differential value of the vehicle speed detected by the vehicle speed detector 6.

  When the accelerator pedal is depressed (YES in S003), the control unit 4 calculates the running resistance R from the tire driving force F and the acceleration resistance Ra (S005).

  The acceleration resistance Ra is calculated from the multiplication of the vehicle weight W stored in advance and the vehicle acceleration Ax (Ra = W × Ax). Calculation of the acceleration Ax is the same as S004.

  The running resistance R can be calculated by subtracting the acceleration resistance Ra from the tire driving force F (R = F−Ra).

Next to S004 or S005, the control unit 4 determines whether or not the vehicle is turning when the travel resistance is calculated based on the output of the vehicle turning detection unit 8 (S006).
The control unit 4 causes the storage unit 11 to store the traveling resistance calculated separately when the vehicle is turning (S007) and when the vehicle is not turning (S008). The reason why the running resistance is classified based on whether or not the vehicle is turning is that the turning resistance is added to the running resistance when the vehicle is turning, so the running resistance is calculated by calculating the running resistance based on the data when the vehicle is not turning. This is because the calculation accuracy can be improved.

  Following S007 or S008, the control unit 4 determines whether or not sufficient travel resistance data has been accumulated for each vehicle speed (S009).

  The control unit 4 determines whether or not the calculated running resistance follows a normal distribution, and can determine that sufficient running resistance data has been accumulated when it is determined that the calculated running resistance is a normal distribution. The calculation accuracy of running resistance can be improved by using only the data according to the normal distribution.

  When it is determined that a sufficient amount of travel resistance data has been accumulated for each vehicle speed (YES in S009), the control unit 4 calculates the average value of the collected travel resistance, and this is calculated for the vehicle when traveling on a flat road. The running resistance is unique (S010).

  The control unit 4 can also calculate the standard deviation of the calculated running resistance, and can calculate the average value for the running resistance that falls within a predetermined value from the center value (average value of the collected running resistance). In addition, when the calculated standard deviation of the running resistance is within the standard deviation calculated in advance through experiments or the like, the average value of the collected running resistance may be calculated.

  The calculated running resistance is stored in the storage unit 11 for each vehicle speed [km / h] when the running resistance is calculated. This travel resistance is hereinafter referred to as “vehicle-specific travel resistance”. FIG. 6 is a diagram for explaining the running resistance for each vehicle speed stored in the storage unit 11.

“Running resistance based on vehicle specifications” in FIG. 6 is a running resistance for each vehicle speed stored in the storage unit 11 in advance. This is a running resistance calculated from vehicle specifications, that is, elements common to the vehicle type (vehicle weight, total length, total width, total height, etc.). Since “running resistance based on vehicle specifications” does not include an error factor specific to each vehicle, it can be stored in the storage unit 11 in advance.

  On the other hand, the “vehicle-specific travel resistance” in FIG. 6 represents the travel resistance specific to the vehicle calculated in S010.

  6 is stored in the storage unit 11 separately when the vehicle is turning and when the vehicle is not turning.

  The running resistance includes “rolling resistance”, “air resistance”, “gradient resistance”, “acceleration resistance”, and “turning resistance”. The solid lines in FIG. 6 indicate “rolling resistance” and “air resistance”.

  The rolling resistance can be expressed by μr × W × g (μr is a rolling resistance coefficient, W is a vehicle weight [kg], and g is a gravitational acceleration [m / s ^ 2]). Note that the rolling resistance coefficient is 0.01 to 0.02 in the case of a normal road.

  The air resistance is μd × A × (ρ / 2) × V ^ 2 (μd is the air resistance coefficient, A is the front projection area [m ^ 2], ρ is the air density [kg / cm ^ 2], 1 atm. At the standard atmospheric pressure of ρ = 1.226). V is the vehicle speed [m / s ^ 2]. According to this equation, the air resistance is proportional to the square of the vehicle speed.

  The gradient resistance can be expressed as W × g × sin θ (W is vehicle weight [kg], g is gravitational acceleration [m / s ^ 2], and θ is road inclination angle [deg]).

  The acceleration resistance is (W + ΔW) × g × a (W is the vehicle weight [kg], ΔW is the weight equivalent to the rotating part [kg], g is the gravitational acceleration [m / s ^ 2], and a is the vehicle acceleration [m / s ^ 2]).

  The running resistance calculated in S010 (without vehicle turning) does not include “gradient resistance” because it is during flat road running in S002, and does not include “acceleration resistance” because the acceleration resistance is reduced in S004 and S005. Since the data is when the vehicle is not turning, “turning resistance” is not included. As a result, the running resistance in FIG. 6 is composed of “rolling resistance” and “air resistance”.

  After calculating the vehicle-specific travel resistance in S010, the control unit 4 updates the regenerative torque reference value based on the vehicle-specific travel resistance (regenerative torque reference value update function of the control unit 4) (S011).

  First, the control unit 4 calculates a ratio between “travel resistance based on vehicle specifications” and “vehicle-specific travel resistance” stored in the storage unit 11. This ratio is hereinafter referred to as a vehicle specific coefficient. This vehicle specific coefficient is a coefficient that represents how much the running resistance based on the vehicle specifications changes due to a vehicle specific factor.

  This vehicle specific coefficient is calculated by averaging the vehicle specific coefficients calculated for each speed. For example, in the case of FIG. 6, the “vehicle-specific travel resistance” is about 10% higher than the “travel resistance based on vehicle specifications”, so the vehicle-specific coefficient is 0.9.

  Note that the vehicle specific coefficient can be calculated based on the difference between the “vehicle-specific travel resistance” and the “travel resistance based on vehicle specifications” instead of the ratio.

  Next, the control unit 4 updates the regenerative torque reference value by multiplying the regenerative torque reference value stored in advance in the storage unit 11 by the coefficient. FIG. 7 is a diagram for explaining the relationship between the motor speed and the regenerative torque. The regenerative torque reference value in FIG. 7 represents the relationship between the motor rotation speed calculated based on vehicle specifications and the regenerative torque [Nm]. Since the regenerative torque reference value does not include an error factor unique to each vehicle, it can be stored in the storage unit 11 in advance.

  The control unit 4 multiplies the regenerative torque reference value by the vehicle specific coefficient, and stores the result in the storage unit 11. This multiplication result is the “updated regenerative torque reference value” in FIG. The “updated regenerative torque reference value” is used when correcting the regenerative torque as will be described later.

  The storage unit 11 also stores a regenerative torque limit value with respect to the motor rotation speed. When the regenerative torque reference value is updated, if the regenerative torque limit value is exceeded, the updated value is set to the limit value. This is to prevent the electric motor 2 from being damaged.

  When S011 is ended, the control unit 4 ends the process (end of FIG. 5), and then returns the process to the start (start of FIG. 5) again.

  Next, the regenerative braking force calculation function of the control unit 4 will be described with reference to FIGS. FIG. 8 is a flowchart for explaining the operation of the regenerative braking control device for a vehicle in one embodiment of the present invention. FIG. 9 is a diagram for explaining the relationship between the road inclination angle and the regenerative torque increase / decrease coefficient. The processing in FIG. 5 and the processing in FIG. 8 are executed independently of each other.

  First, the control unit 4 acquires the vehicle inclination angle θ calculated by the road inclination angle calculation unit 7 (S101), and then determines whether or not the accelerator pedal is depressed (S102). When the accelerator pedal is depressed (YES in S102), the control unit 4 executes S101 again.

  When the accelerator pedal is not depressed (NO in S102), the control unit 4 acquires the motor speed of the electric motor 2 (S103). After S103, the control unit 4 reads out the “updated regenerative torque reference value” corresponding to the motor rotation speed of the electric motor 2 acquired in S103 from the storage unit 11 (S104).

  After S104, the control unit 4 calculates a regenerative torque increase / decrease coefficient corresponding to the road inclination angle θ calculated in S101, and multiplies the regenerative torque reference value by this coefficient.

  The regenerative torque increase / decrease coefficient will be described with reference to FIG. FIG. 9 is a diagram for explaining the relationship between the road inclination angle and the regenerative torque increase / decrease coefficient. The regenerative torque increase / decrease coefficient when traveling on a flat road is “1”. Since the “updated regenerative torque reference value” stored in the storage unit 11 is for running on a flat road, it is not necessary to change the regenerative torque reference value when the vehicle is running on a flat road. "

  On the other hand, during uphill running, the regenerative torque increase / decrease coefficient decreases as the road inclination angle θ increases (to the right in the graph of FIG. 9). This is because, when traveling uphill, gradient resistance is added in addition to traveling resistance during traveling on a flat road. It is necessary to set the regenerative torque as small as the gradient resistance is applied. The gradient resistance increases as the inclination angle θ increases. Therefore, since the gradient resistance needs to reduce the regenerative torque as the inclination angle θ increases, the regenerative torque increase / decrease coefficient is decreased.

  On the other hand, when traveling downhill, the regenerative torque increase / decrease coefficient increases as the road inclination angle θ increases (to the left in the graph of FIG. 9). When traveling downhill, an acceleration force associated with gravitational acceleration is applied as compared to when traveling on a flat road, so that the regenerative torque can be set large.

Next to S105, the control unit 4 acquires the brake depression amount from the brake depression amount detection unit 10, and determines whether the brake is ON or OFF based on the brake depression amount.
When the brake depression amount is greater than or equal to a predetermined threshold and when the brake is ON (YES in S106), it is determined that the brake is OFF (NO in S106) if it is smaller than the predetermined threshold. If it is determined that the brake is OFF (NO in S106), the control unit 4 advances the process to S108.

  On the other hand, when it is determined that the brake is ON (YES in S106), the control unit 4 multiplies the regenerative torque increase / decrease coefficient and the regenerative torque reference value according to the brake depression amount acquired from the brake depression amount detection unit 10. Correct the result.

  Specifically, the regenerative torque calculated in S105 (a value obtained by multiplying the regenerative torque increase / decrease coefficient and the regenerative torque reference value) is corrected in accordance with the brake depression amount.

  For example, the regenerative torque calculated in S105 can be multiplied by a coefficient corresponding to the brake depression amount. The coefficient corresponding to the brake depression amount is a coefficient that changes from 1 to 0 as the brake depression amount changes from zero (no depression) to 100% (when fully depressed). As a result, the regenerative torque is set smaller as the brake depression amount increases.

  As another method, without changing the magnitude of the regenerative torque calculated in S105, the braking force of the mechanical brake amount Rb is variably controlled according to the magnitude of the brake depression amount or the magnitude of the regenerative torque. May be.

  The control unit 4 sets the calculated regenerative torque target value and controls the regenerative braking force. Specifically, “regenerative torque to be controlled (current value) = (calculated regenerative torque target value + predetermined coefficient K × regenerative torque to be controlled (previous value)) / predetermined coefficient L”, and the regenerative torque after low-pass filter processing is It is preferable to set and control the regenerative braking force. This is to prevent a sudden regenerative torque change. For example, if the predetermined coefficient K is 9 and the predetermined coefficient L is 10, the regenerative torque to be controlled (current value) is 90% of the regenerative torque to be controlled last time (current value), and the calculated regenerative torque target value is 10%. It becomes the value mixed by the ratio.

  When the brake is ON (YES in S106), the regenerative torque corrected in S107 is the target value. On the other hand, when the brake is OFF (NO in S106), the result of multiplying the regenerative torque increase / decrease coefficient and the regenerative torque reference value is the calculated regenerative torque target value.

  After finishing S108 (end of FIG. 8), the control unit 4 returns the processing to the start (start of FIG. 8) again.

  As described above, the regenerative braking control device for a vehicle according to the embodiment of the present invention calculates the running resistance when the vehicle is actually running on a flat road. An error factor peculiar to each vehicle is added to this running resistance, and the regenerative braking control device for a vehicle according to the present invention calculates a regenerative braking force during flat road running based on this running resistance. Based on the power, the regenerative braking force when the vehicle is traveling uphill or the regenerative braking force when traveling downhill is controlled.

  In this way, by adding an error factor specific to each vehicle to the running resistance, it is possible to reduce the brake feeling or the brake feeling variation for the driver.

  Note that the control unit 4 can calculate the running resistance when neither the accelerator nor the brake is depressed, or when the vehicle is running at a substantially constant speed.

  When the vehicle is traveling at a substantially constant speed, it is not necessary to consider the acceleration resistance, so that the calculation accuracy of the traveling resistance is increased. Further, when neither the accelerator nor the brake is depressed, there is no need to consider the amount of mechanical braking, so that the calculation accuracy of the running resistance is increased.

  The control unit 4 can control the regenerative braking force in S108 when the speed detected by the vehicle speed detection unit 6 is larger than a predetermined value. When the vehicle is traveling at a low speed, the excitation power supplied to the electric motor 2 that generates regenerative braking is larger and energy is not saved. For this reason, it is better not to perform regenerative braking. Therefore, the energy saving effect can be improved by doing the above.

  Further, the control unit 4 controls the regenerative braking force when the speed detected by the vehicle speed detection unit 6 is greater than a predetermined value. It is possible to set a different value depending on the situation. In particular, it is preferable that the control unit 4 sets a predetermined value when traveling uphill to be larger than a predetermined value when traveling downhill.

  When traveling uphill, the deceleration is fast due to the effect of the gradient resistance, so unless the regenerative braking force control update frequency is increased, there is a possibility that the regenerative braking will be applied momentarily below the predetermined value. . Conversely, when traveling downhill, the deceleration is slow due to the influence of the gradient resistance, so that the control can be performed at a predetermined value even if the renewal braking force control update frequency is lower than the predetermined value. For this reason, it is preferable that the predetermined value when traveling uphill is larger than the predetermined value when traveling downhill so as not to fall below the predetermined value.

  The control unit 4 controls the regenerative braking force when the absolute value of the difference between the road gradient calculated by the road inclination angle calculation unit 7 and the road gradient calculated before the calculation is larger than a predetermined value. Can be. This “calculated before this calculation” is, for example, when the regenerative braking force has been previously controlled.

  When the absolute value of the difference from the road gradient calculated this time is smaller than a predetermined value compared to the road gradient when the regenerative braking force was previously controlled, the regenerative braking force is the same as before.

  In addition, the calculation of the road inclination angle calculation unit 7 is sampled every predetermined time to calculate the absolute value of the road gradient, and when the change amount of the absolute value of the road gradient for each sampling is larger than the predetermined value, the regenerative braking force is calculated. It can also be controlled.

  By doing in this way, the regenerative braking force concerning a vehicle can be estimated in advance, and the time delay by the calculation of the control part 4 does not generate | occur | produce. Further, it is not necessary to frequently change the regenerative braking force applied to the vehicle.

Further, the control unit 4 calculates the running resistance of the vehicle when the vehicle turning detection unit 8 determines that the vehicle is turning and when the vehicle turning detection unit 8 does not determine that the vehicle is turning, based on the calculated running resistance. The regenerative braking force of the electric motor 2 is calculated depending on whether the vehicle turning detection unit 8 determines that the vehicle is turning or not based on the calculated regenerative braking force. Can be controlled differently.

  By doing in this way, at the time of vehicle turning, there exists an effect that regenerative braking power can be controlled in consideration of turning resistance.

  Note that the control unit 4 can periodically initialize the running resistance. For example, it can be initialized at the start of travel. In addition, an average value of a predetermined number (for example, 100) of the latest running resistance data is obtained, and this average value and an average value calculated in the past, that is, more than the latest predetermined number of running resistance data. Compared to the average value of the previous data, the running resistance is initialized when the difference is greater than a predetermined value.

  The error factors specific to each vehicle change from time to time. For example, when the number of passengers changes, the vehicle weight changes. By periodically initializing, there is an effect that it is possible to follow changes in errors inherent in the vehicle such as vehicle weight and rolling resistance coefficient.

Although the vehicle regenerative braking control device according to the embodiment of the present invention has been described as calculating the inclination angle θ of the vehicle with respect to the road by the road inclination angle calculation unit 7, the ratio of traveling on a flat road on a general road Therefore, the running resistance may be obtained without using the road inclination angle calculation unit 7. By doing in this way, there exists an effect that it becomes unnecessary to use the sensor for calculating the road gradient which constitutes road inclination angle calculation part 7.

  INDUSTRIAL APPLICABILITY The present invention is useful as a regenerative braking control device for a vehicle that converts kinetic energy when the vehicle is braked into electric energy and collects it in a storage battery.

DESCRIPTION OF SYMBOLS 1 Regenerative braking control apparatus for vehicles 2 Electric motor 3 Storage battery 4 Control part 5 Acceleration sensor 6 Vehicle speed detection part 7 Road inclination angle calculation part 8 Vehicle turning detection part 9 Accelerator opening degree detection part 10 Brake depression amount detection part 11 Storage part 12 Information Part

Claims (11)

A regenerative braking control device for a vehicle, comprising: an electric motor that converts kinetic energy into electric energy to generate a regenerative braking force; and a storage battery that stores electric energy converted by the electric motor,
A road inclination angle calculation unit for calculating the gradient of the road on which the vehicle is traveling;
When it is determined that the vehicle is traveling on a flat road based on the road gradient calculated by the road inclination angle calculation unit, a running resistance is calculated based on the acceleration of the vehicle,
Based on the calculated running resistance, a reference value of the regenerative braking force when the vehicle is running on a flat road is calculated,
A control unit for controlling the regenerative braking force of the electric motor based on the calculated regenerative braking force,
Wherein the control unit, the regenerative braking force of updating the reference value, based on the reference value of the regenerative braking force during running on a flat road that updated each time calculates the running resistance,
The regenerative braking force of the electric motor when the vehicle is traveling uphill, or the regenerative braking force of the electric motor when traveling downhill according to the road gradient calculated by the road inclination angle calculation unit. A regenerative braking control device for a vehicle characterized by performing control to be set . The regenerative braking control device for a vehicle according to claim 1, wherein the control unit calculates a running resistance by subtracting an acceleration resistance based on an acceleration from a tire driving force transmitted to a tire of the vehicle. The vehicle according to claim 1, wherein the control unit calculates a running resistance when neither an accelerator nor a brake is depressed, or when the vehicle is running at a substantially constant speed. Regenerative braking control device. A vehicle speed detection unit for detecting the speed of the vehicle;
The regenerative braking control device for a vehicle according to claim 1, wherein the control unit controls a regenerative braking force when the speed detected by the vehicle speed detection unit is larger than a predetermined value. When the regenerative braking force is controlled when the speed detected by the vehicle speed detection unit is greater than a predetermined value, the control unit travels down and on the predetermined value when the vehicle is traveling uphill. The regenerative braking control device for a vehicle according to claim 4, wherein the value is different depending on when the vehicle is running. The control unit is configured to control the regenerative braking force when the speed detected by the vehicle speed detection unit is greater than a predetermined value. The vehicle regenerative braking control device according to claim 5, wherein the vehicle regenerative braking control device is larger than a predetermined value. The control unit controls the regenerative braking force when the absolute value of the difference between the road gradient calculated by the road inclination angle calculation unit and the road gradient calculated before the calculation is larger than a predetermined value. The regenerative braking control device for a vehicle according to claim 1. A vehicle turning detection unit for determining whether or not the vehicle is turning;
The control unit calculates a running resistance of the vehicle when the vehicle turning detection unit determines that the vehicle is turning and when the vehicle turning detection unit does not determine that the vehicle is turning, and the vehicle is based on the calculated running resistance. Calculate the regenerative braking force when traveling on a flat road,
2. The control of the regenerative braking force of the electric motor is made different when the vehicle turning detection unit determines that the vehicle is turning based on the calculated regenerative braking force and when it is not determined that the vehicle is turning. The regenerative braking control device for a vehicle according to 1. The storage unit further stores a running resistance that is calculated and updated as needed by the control unit,
The regenerative braking control device for a vehicle according to claim 1, wherein the control unit periodically initializes a running resistance stored in the storage unit. The storage unit further stores a running resistance that is calculated and updated as needed by the control unit,
The control unit determines whether or not the running resistance stored in the storage unit follows a normal distribution, and based on the running resistance calculated when the running resistance is determined to be a normal distribution, the regenerative control when the vehicle travels on a flat road The regenerative braking control device for a vehicle according to claim 1, wherein power is calculated. The regenerative braking control device for a vehicle according to claim 1, further comprising a notification unit that notifies a driver when the running resistance calculated by the control unit is greater than a predetermined value.