Control method for electric vehicle and electric vehicle

Abstract

To store mechanical energy into a fly wheel when continuously performing high load travel.SOLUTION: A control method of an electric vehicle is given in which the electric vehicle includes: a power storage device; a first motor which is driven by electric energy of the power storage device as a main driving force; a fly wheel as an auxiliary drive source; and a controller which controls driving force. The controller performs energy storing operation where the first motor rotates the fly wheel to store rotation energy into the fly wheel when output of the power storage device is lower than the maximum output.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control method for an electric vehicle and an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle that includes a motor as a first driving force source for driving the vehicle and a flywheel as a second driving force source for recovering and storing the vehicle's kinetic energy as mechanical energy. The document also discloses control in which the vehicle's kinetic energy is recovered and stored in the flywheel as mechanical energy when the vehicle decelerates, and the mechanical energy is used to drive the vehicle when the vehicle subsequently accelerates. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-116106 Summary of the Invention [Problem to be solved by the invention]

[0004] The control described in the above document requires deceleration in order to store mechanical energy in the flywheel, which creates the problem that mechanical energy cannot be stored in the flywheel when the vehicle is continuously driven under high load, such as when driving on a highway in North America.

[0005] Therefore, an object of the present invention is to enable the storage of mechanical energy in the flywheel even under conditions where high load running is performed continuously. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a control method for an electric vehicle including a power storage device, a first motor as a main drive source operated by electric energy from the power storage device, a flywheel as a sub-drive source, and a controller for controlling drive force. In this control method, the controller performs an energy storage operation of rotating the flywheel by the first motor and storing rotational energy in the flywheel when the output of the power storage device is lower than the maximum output. After the energy storage operation is performed, whether or not acceleration is necessary is determined while the vehicle is traveling based on at least information about the position and speed of the vehicle itself and information about a vehicle ahead, and if acceleration is not necessary, the rotational energy is stored as electrical energy in the power storage device. . [Effects of the Invention]

[0007] According to the above aspect, it is possible to store rotational energy (mechanical energy) in the flywheel even in a situation where high load running is performed continuously. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a powertrain of an electric vehicle according to the first embodiment. [Figure 2] FIG. 2 is a time chart of the vehicle speed and battery output when a typical electric vehicle is running. [Figure 3] FIG. 3 is a flowchart showing a control routine according to the first embodiment. [Figure 4] FIG. 4 is a timing chart when the control routine according to the first embodiment is executed. [Figure 5] FIG. 5 is a schematic configuration diagram of a powertrain of an electric vehicle according to the second embodiment. [Figure 6] FIG. 6 is a schematic configuration diagram of a powertrain of an electric vehicle according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0010] [First embodiment] The first embodiment will be described with reference to FIGS.

[0011] 1 is a schematic diagram of the powertrain of an electric vehicle 1 (hereinafter simply referred to as "vehicle 1") according to this embodiment. In the following description, the forward direction of the vehicle 1 is referred to as "front," the backward direction as "rear," the left side of the forward direction of the vehicle 1 as "left," and the right side as "right."

[0012] The vehicle 1 includes a first motor 2 as a main drive source, a battery 3 as an electricity storage device that supplies power (electrical energy) to the first motor 2, a controller 4 that controls the driving force, and a left front wheel 12FL and a right front wheel 12FR that are driven by the driving force generated by the first motor 2. When there is no need to particularly distinguish between the left front wheel 12FL and the right front wheel 12FR, they may be collectively referred to as the front wheels 12F. In addition, in this embodiment, the electricity storage device is a battery 3, but this is not limited to this and may be any device that has a power storage function, such as a capacitor.

[0013] The first motor 2 is disposed in a motor room provided at the front of the vehicle body. The driving force generated by the first motor 2 is transmitted to a left front wheel 12FL and a right front wheel 12FR via a power transmission mechanism 11, a gearbox 8 including a final gear, and a left front wheel drive shaft 9FL and a right front wheel drive shaft 9FR. The power transmission mechanism 11 may be any mechanism capable of transmitting the power of the first motor 2, and may be, for example, a gear set consisting of a plurality of spur gears.

[0014] The controller 4 includes an inverter that controls the input / output power of the battery 3, and controls the input / output power of the battery 3 and the output of the first motor 2 according to the required driving force.

[0015] Furthermore, the vehicle 1 is equipped with a flywheel (hereinafter sometimes abbreviated as "FW") 5 as an auxiliary drive source. The rotation axis of FW5 is collinear with the rotation axes of the left rear wheel 12RL and the right rear wheel 12RR, and is connected to the left rear wheel 12RL via the left rear wheel drive shaft 10RL and to the right rear wheel 12RR via the right rear wheel drive shaft 10RR. A second clutch 7 (CL2 in the figure) that connects and disconnects the power transmission between FW5 and the left rear wheel 12RL and the right rear wheel 12RR is also provided between the left rear wheel drive shaft 10RL and the right rear wheel drive shaft 10RR. When there is no need to particularly distinguish between the left rear wheel 12RL and the right rear wheel 12RR, they may be collectively referred to as the rear wheel 12R.

[0016] Furthermore, FW5 is connected to the first motor 2 via an auxiliary power transmission mechanism 11A branching off from the power transmission mechanism 11. A first clutch 6 (CL1 in the figure) that connects and disconnects the power transmission between the first motor 2 and FW5 is installed in the auxiliary power transmission mechanism 11A. The auxiliary power transmission mechanism 11A may be any mechanism that can transmit power from the first motor 2 located at the front of the vehicle body to FW5 located at the rear of the vehicle body, and for example, a transmission mechanism that combines a rotating shaft extending in the fore-and-aft direction of the vehicle body with a bevel gear can be used.

[0017] A known clutch mechanism, such as a friction clutch, having the function of connecting and disconnecting power transmission can be used for the first clutch 6 and the second clutch 7. The first clutch 6 and the second clutch 7 are switched between engaged and disengaged states by the controller 4.

[0018] In the vehicle 1 described above, when the first motor 2 is driven by the power of the battery 3 with the first clutch 6 engaged and the second clutches 7 disengaged, the FW5 rotates. Even if the first clutch 6 is subsequently disengaged, the FW5 continues to rotate by inertia. In other words, the electrical energy of the battery 3 is stored in the FW5 as rotational energy. Rotating the FW5 by the first motor 2 and storing the rotational energy in the FW5 in this manner is also referred to as an energy storage operation.

[0019] When each second clutch 7 is engaged with rotational energy stored in FW5, the left rear wheel 12RL and the right rear wheel 12RR are driven by the stored rotational energy.

[0020] Figure 2 is a time chart of the vehicle speed and battery output when a typical electric vehicle (i.e., an electric vehicle without a FW5) is traveling. This time chart shows a case where high-speed traveling continues for a long period of time, such as on a highway in North America.

[0021] Even when traveling at high speeds, battery output is not very large and remains almost constant if the vehicle speed is constant. On the other hand, battery output increases during acceleration. In particular, when accelerating from a high vehicle speed, as in area A in the figure, battery output increases significantly and reaches its maximum value during traveling. When determining the capacity of the battery to be installed in an electric vehicle, it is necessary to take into account this maximum battery output during traveling. In other words, if the maximum battery output during traveling can be reduced, the battery capacity can be reduced, and as a result, the power unit can be made smaller.

[0022] Therefore, in this embodiment, during high-load driving, such as when accelerating from a high vehicle speed, not only are the front wheels 12F driven by the first motor 2, but the rear wheels 12R are also driven using the rotational energy stored in FW5. In other words, the required output is not provided solely by the first motor 2, but part of it is provided by the rotational energy of FW5. This makes it possible to reduce the output of the battery 3, which is the power source for the first motor 2.

[0023] Incidentally, it has been known in the past to provide a FW5 as an auxiliary power source and utilize the rotational energy of the FW5 during acceleration at start, etc. However, in the conventionally known system, the kinetic energy of the vehicle 1 is stored as rotational energy of the FW5 during deceleration. Therefore, when high-speed traveling continues for a long period of time, it is not possible to store rotational energy in the FW5.

[0024] In contrast, in the vehicle 1 of this embodiment, the FW5 is rotated by the driving force of the first motor 2, so that rotational energy can be stored in the FW5 even when the vehicle is not decelerating. Therefore, rotational energy can be stored in the FW5 even when the vehicle continues to travel at high speed for a long period of time, and the rotational energy of the FW5 can be used when accelerating from a high vehicle speed. The control of the FW5 in this embodiment will be described below.

[0025] 3 is a flowchart showing a control routine for the FW5 executed by the controller 4. This control routine stores rotational energy in the FW5 when the output of the battery 3 is lower than the maximum output and uses that rotational energy for driving during acceleration if future acceleration is predicted during constant-speed driving. For example, if the required output during acceleration is 100 kW, the output of the first motor 2 is set to 70 kW, and the remaining 30 kW is supplied by the rotational energy of the FW5. Then, the FW5 is rotated so that it has enough rotational energy to generate 30 kW.

[0026] The steps in the flowchart will be described in detail below.

[0027] In step S100, the controller 4 determines whether the vehicle is moving based on the vehicle speed, and if the vehicle is moving, executes the process of step S101, and if the vehicle is not moving, ends the current routine. The vehicle speed used for this determination may be a value detected by a vehicle speed sensor (not shown) provided on the vehicle 1, or may be a value calculated based on a signal from an artificial satellite or the like.

[0028] In step S101, the controller 4 reads the position information, speed information, and information about the vehicle in front of the vehicle 1 acquired by radar, sensors, a GPS (Global Positioning System), a car navigation system, and the like (none of which are shown) mounted on the vehicle 1. The information about the vehicle in front includes, for example, the speed of the vehicle in front and the distance between the vehicle 1 and the vehicle in front. The position information about the vehicle 1 includes not only the current position of the vehicle 1 but also the route it will take from here on.

[0029] In step S102, the controller 4 determines whether or not the rotational energy (also referred to as FWE) of the FW 5 is insufficient, and if so, executes the process of step S103, and if not, executes the process of step S104. A case where FWE is insufficient means a case where the output allocated to the FW 5 during acceleration cannot be covered.

[0030] In step S103, the controller 4 determines whether there is a margin in the battery output, and if there is a margin, executes the processing of step S104, and if there is no margin, ends this routine. When there is a margin in the battery output, this means that the current battery output is lower than the maximum output of the battery 3, for example, during constant speed driving. In other words, the determination in step S103 determines whether or not the energy storage operation can be performed.

[0031] In step S104, the controller 4 determines whether acceleration is necessary, and if acceleration is necessary, executes the processing of step S105, or if acceleration is not necessary, executes the processing of step S114. Whether acceleration is necessary is determined based on the information read in step S101. It is determined that acceleration is necessary when, for example, it is predicted that the vehicle 1 will catch up with the vehicle in front and will need to take an overtaking action based on the inter-vehicle distance and relative speed between the vehicle 1 and the vehicle in front. It is also determined that acceleration is necessary when it is known from map information in the car navigation system that the speed limit will increase up ahead.

[0032] In step S105, the controller 4 determines whether or not generation of FWE is necessary, that is, whether or not it is necessary to perform an energy storage operation, and if generation of FWE is unnecessary, the controller 4 executes the process of step S106, and if generation of FWE is necessary, the controller 4 executes the process of step S107. For example, if the current vehicle speed of the vehicle 1 is high (e.g., 80 km / h or higher), the battery output will be at or near maximum output in order to accelerate from there, and therefore it is determined that generation of FWE is necessary.

[0033] In step S106, the controller 4 holds the FWE. That is, if the FW 5 is already rotating, it maintains the rotating state, and if the FW 5 is stopped, it maintains the stopped state.

[0034] In step S107, the controller 4 generates FWE, that is, performs an energy storage operation.

[0035] After completing the processing of step S106 or step S107, the controller 4 determines in step S108 whether or not FWE needs to be released. If release is necessary, the controller 4 executes the processing of step S109. If release is not necessary, the controller 4 returns to the processing of step S101. Here, the controller 4 determines whether or not FWE needs to be used to suppress the peak of the battery output based on various conditions, and determines that release is necessary if FWE needs to be used. For example, the controller 4 determines that release is necessary when starting acceleration from a high vehicle speed, when catching up with a vehicle ahead and starting to overtake, when the accelerator pedal is depressed heavily, etc. Furthermore, if the vehicle is equipped with a switch that allows the driver to select whether or not to use FWE during acceleration, and the switch has selected the use of FWE, the controller 4 also determines that release is necessary.

[0036] If it is determined that the release is necessary, the controller 4 releases the FWE by engaging the second clutch 7 in step S109.

[0037] After releasing FWE in step S109, the controller 4 reads information in step S110 in the same way as in step S101, and determines whether acceleration is necessary in step S111 in the same way as in step S104. If it is determined in step S111 that acceleration is necessary, the process returns to step S102, and if it is determined that acceleration is unnecessary, the process executes step S112.

[0038] In step S112, the controller 4 determines whether or not there is a remaining amount of FWE, and if there is a remaining amount, the process of step S113 is executed, and if there is no remaining amount, the current routine is terminated.

[0039] In step S113, the controller 4 charges the battery 3 with the FWE as electrical energy. Specifically, when the first motor 2 is in a state where it can generate regenerative power, the first clutch 6 is engaged to rotate the first motor 2 using the FWE to generate regenerative power, and the electrical energy thus generated is charged into the battery 3. This stops the rotation of the FW 5.

[0040] Steps S114 and S115, which are executed when it is determined in step S104 that acceleration is not required, are the same as steps S112 and S113 described above.

[0041] The reason why the battery 3 is charged using FWE in steps S113 and S115 is as follows.

[0042] When the FW5 rotates, vibrations may occur due to the rotation. Furthermore, when the FW5 rotates, a gyro moment is generated when the vehicle 1 moves up and down in response to unevenness in the road surface or when turning around a curve in the road. This gyro moment acts in a direction that tilts the vehicle body and changes the direction of the vehicle body, thereby reducing the maneuverability and handling stability of the vehicle 1.

[0043] Therefore, when it is determined that acceleration is unnecessary, FW5 is stopped to suppress the effects of vibration and gyro moment caused by rotation. However, simply stopping FW5 would waste FWE, so FWE is converted into electrical energy and charged to battery 3.

[0044] 4 is an example of a timing chart when the above control routine is executed. The dashed lines in the chart of the battery output and the first motor output represent the case where FW5 is not provided.

[0045] The stopped vehicle 1 starts moving at timing T1, and ends acceleration at timing T2, starting constant speed driving. As the vehicle 1 reaches constant speed driving, the battery output and the output of the first motor also become approximately constant. The above information is also read to determine whether or not there will be further acceleration. If it is detected at timing T3 that acceleration is necessary, energy storage operation begins at timing T4. The battery output increases once energy storage operation is performed, but returns to the magnitude before energy storage operation began once FWE is generated.

[0046] When acceleration begins at timing T5, the battery output is increased to increase the output of the first motor 2, and FWE is released. Without FW5, this acceleration would increase the battery output to its maximum. In contrast, in the vehicle 1 of this embodiment, the FWE stored in FW5 is used as driving force, so the same acceleration force can be obtained with a lower motor output than when FW5 is not provided. Because the output of the first motor 2 is lower, the battery output is also lower than when FW5 is not provided.

[0047] Then, at time T6, acceleration ends and constant speed traveling begins again. Note that while Figure 4 shows a case in which FWE is used up during acceleration from time T5 to time T6, if FWE remains at time T6, the remaining FWE is used to charge the battery 3 as described above.

[0048] As described above, this embodiment provides an electric vehicle including a battery 3 (power storage device), a first motor 2 as a main drive source operated by electric energy from the battery 3, a flywheel 5 as a sub-drive source, and a controller 4 that controls drive force. The controller 4 performs an energy storage operation in which the first motor 2 rotates the flywheel 5 and stores rotational energy in the flywheel 5 when the output of the battery 3 is lower than the maximum output. This allows rotational energy to be stored in the flywheel 5 even when not decelerating.

[0049] In this embodiment, for example, during high-load driving, the controller 4 uses the rotational energy for driving in combination with the driving force of the first motor 2. As a result, when accelerating from a state of continuous high-speed driving, for example, the amount of energy taken out from the battery 3 can be reduced by the amount of rotational energy used in the FW5. In other words, the peak of battery output during acceleration can be suppressed while achieving the required acceleration.

[0050] In this embodiment, the controller 4 performs the energy storage operation when the output of the battery 3 is lower than the maximum output and the vehicle is traveling at a constant speed. In this manner, in a situation where there is a margin in the battery output, the energy storage operation can be performed appropriately.

[0051] In this embodiment, the controller 4 may store the rotational energy as electrical energy in the battery 3. For example, this may occur when the rotational energy is no longer needed for driving after the energy storage operation has been performed. This prevents the rotational energy from going to waste even when the rotational energy has been generated but there is no longer an opportunity to use it.

[0052] In this embodiment, the flywheel 5 is connected to a drive shaft (left rear drive shaft 10RL and right rear drive shaft 10RR) different from the drive shaft (left front drive shaft 9FL and right front drive shaft 9FR) driven by the first motor 2. This eliminates the need to place the flywheel 5 in the motor room where the first motor 2 and other components are located, simplifying the vehicle's on-board layout. Furthermore, the vehicle enters four-wheel drive mode during acceleration, improving driving stability.

[0053] [Second embodiment] The second embodiment will be described with reference to FIG.

[0054] 5 is a schematic diagram of the powertrain of a vehicle 1 according to this embodiment. The difference from the first embodiment is that there is no auxiliary power transmission mechanism 11A that transmits the power of the first motor 2 to FW5, and a second motor 13 is provided to drive FW5. Regarding control, the difference is that FW5 is driven by the second motor 13 instead of the first motor 2 when performing the energy storage operation.

[0055] In this embodiment, by providing a second motor 13 separate from the first motor 2 for driving the FW5, controllability is improved compared to the configuration of the first embodiment. That is, in the configuration of the first embodiment, when controlling the output of the first motor 2, it is necessary to calculate a target output that combines the output for driving and the output for energy storage operation, whereas in the configuration of this embodiment, it is sufficient to calculate the target output of each motor 2, 13. Furthermore, in the vehicle 1 of the first embodiment, the processing of steps S113 and S115 of the control routine described above cannot be executed unless the first motor 2 is in a state where regeneration is possible, but in the vehicle 1 of this embodiment, these steps can be executed at any time.

[0056] Furthermore, the battery 3 and the second motor 13 can be connected by electrical wiring, eliminating the need for the auxiliary power transmission mechanism 11A. This eliminates restrictions on the handling of the auxiliary power transmission mechanism 11A, improving the design freedom of the vehicle 1.

[0057] The second motor 13, the FW 5, the first clutch 6, and the second clutch 7 may be integrated into an FW unit. By integrating them, installation on the vehicle 1 becomes easier than when each element is installed separately on the vehicle 1. Furthermore, if the FW unit is housed in a compact housing, the degree of freedom in vehicle layout is improved.

[0058] As described above, this embodiment further includes a second motor 13 separate from the first motor 2. The controller 4 performs an energy storage operation in which the second motor 13, instead of the first motor 2, rotates the flywheel 5 to store rotational energy in the flywheel 5 when the output of the battery 3 is lower than the maximum output. By providing the second motor 13 for driving the flywheel 5 in addition to the first motor 2 as the main drive source, the controllability of output control is improved. Furthermore, by eliminating the need for the auxiliary power transmission mechanism 11A from the first motor 2 to the flywheel 5, the degree of freedom in vehicle layout is improved.

[0059] [Third embodiment] The third embodiment will be described with reference to FIG.

[0060] 6 is a schematic diagram of the powertrain of a vehicle 1 according to this embodiment. The difference from the second embodiment is that there are two FW5s, instead of one in the second embodiment. Hereinafter, the two FW5s will be referred to as a first FW5A and a second FW5B. Note that when there is no particular need to distinguish between them, they will be referred to as FW5s.

[0061] The first FW5A and the second FW5B can generate the same output, but the output they can generate is smaller than that of the FW5 of the second embodiment. However, the total output of the two FW5s is equal to or greater than that of the FW5 of the second embodiment. For example, if the output that the FW5 of the second embodiment can generate is 30 kW, the output that the first FW5A and the second FW5B can generate is 20 kW.

[0062] Dividing the FW5 into two units as described above allows for greater freedom in vehicle layout.

[0063] Furthermore, the greater the output of the FW5, the greater the strength required for each element, such as the bearings of the FW5, the fixing members that fix the FW5 to the vehicle 1, and the mounting portions on the vehicle 1 side. Furthermore, the greater the strength of these elements, the higher the cost. In this regard, by dividing the FW5 into two pieces, as in this embodiment, the strength required for each element can be reduced compared to when there is one piece, and as a result, costs can be reduced.

[0064] As described above, in this embodiment, the flywheel 5 includes a first flywheel 5A connected to one of the left and right drive wheels 12RL, 12RR, and a second flywheel 5B connected to the other. This increases the degree of freedom in vehicle layout. Also, costs can be reduced while ensuring acceleration force equal to or greater than that of a single flywheel 5.

[0065] In the above-described embodiments, the electric vehicle 1 has been described as a so-called battery electric vehicle (BEV) in which the only drive source is the first motor and the only power source is the battery 3, but the electric vehicle 1 to which the embodiments can be applied is not limited to this. For example, the electric vehicle 1 may be a so-called extended range electric vehicle equipped with a power generating engine, or a so-called hybrid electric vehicle equipped with a motor as one of multiple drive sources.

[0066] Furthermore, in each of the above-described embodiments, a configuration has been described in which the first motor 2 drives the front wheel 12F and the FW5 drives the rear wheel 12R, but each of the embodiments can also be applied to a configuration in which the first motor 2 and the FW5 drive the same drive wheel.

[0067] It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical concept described in the claims. [Explanation of symbols]

[0068] 1 Electric vehicle, 2 First motor, 3 Battery, 4 Controller, 5 Flywheel, 6 First clutch, 7 Second clutch, 13 Second motor

Claims

1. an electricity storage device; a first motor as a main drive source that is operated by the electric energy of the power storage device; a flywheel as a secondary drive source; a controller for controlling the driving force; A control method for an electric vehicle comprising: the controller performs an energy storage operation in which the first motor rotates the flywheel to store rotational energy in the flywheel when the output of the power storage device is lower than a maximum output, and after performing the energy storage operation, determines whether acceleration is necessary while the vehicle is traveling based on at least information related to a position and speed of the vehicle and information related to a vehicle in front, and if acceleration is not necessary, stores the rotational energy in the power storage device as electrical energy.

2. 2. The method for controlling an electric vehicle according to claim 1, The controller uses the rotational energy for driving in combination with the driving force of the first motor.

3. 3. The method for controlling an electric vehicle according to claim 1, The controller uses the rotational energy for driving together with the driving force of the first motor during high-load driving.

4. The method for controlling an electric vehicle according to any one of claims 1 to 3, The control method for an electric vehicle, wherein the controller performs the energy storage operation when an output of the power storage device is lower than a maximum output and the vehicle is traveling at a constant speed.

5. an electricity storage device; a first motor as a main drive source that is operated by the electric energy of the power storage device; a flywheel as a secondary drive source; a controller for controlling the driving force; In an electric vehicle equipped with the controller performs an energy storage operation in which the first motor rotates the flywheel to store rotational energy in the flywheel when the output of the power storage device is lower than a maximum output, and after performing the energy storage operation, determines whether acceleration is necessary while the vehicle is traveling based on information related to at least a position and a speed of the vehicle and information related to a vehicle in front, and if acceleration is not necessary, stores the rotational energy in the power storage device as electrical energy.

6. In the electric vehicle described in claim 5, An electric vehicle, wherein the flywheel is connected to a drive shaft different from a drive shaft driven by the first motor.

7. In the electric vehicle according to claim 5 or 6, further comprising a second motor separate from the first motor; the controller performs an energy storage operation of rotating the flywheel using the second motor instead of the first motor to store rotational energy in the flywheel when the output of the power storage device is lower than a maximum output.

8. In the electric vehicle according to any one of claims 5 to 7, The electric vehicle includes, as the flywheels, a first flywheel connected to one of the left and right drive wheels, and a second flywheel connected to the other of the left and right drive wheels.

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