CONTROL UNIT FOR ELECTRIC VEHICLES

Abstract

[Objective] To create a control device for an electric vehicle that is capable of reducing battery load even during a long uphill drive. [Solvent] There is: a generator motor (3); a traction motor (4); a battery (9) to be charged with the electrical power generated by the generator motor, which supplies the electrical power to the traction motor; a gradient sensor (93) to detect gradient information about a road on which the electric vehicle (1) is currently traveling; and an ECU (10) to limit an output power of the traction motor in order to limit a maximum speed while the electric vehicle is traveling on an uphill road while the gradient is equal to or greater than a predetermined threshold.

Description

Technical field

[0001] The present invention relates to a control unit of an electric vehicle. Technical background

[0002] Patent specification 1 discloses a series hybrid vehicle comprising an internal combustion engine, a generator motor driven by the internal combustion engine, a battery charged by electrical power generated by the generator motor, and a traction motor for driving the drive wheels with the electrical power generated by the generator motor or supplied by the battery.

[0003] In such a series hybrid vehicle, the generator motor supplies electrical power to drive the traction motor by generating electrical power using the internal combustion engine. Any shortage of electrical power is compensated for by the battery. List of printed materials Patent specification

[0004] Patent specification 1: JP 2013 - 129 313 A Disclosure of the invention Technical problem

[0005] In the case of a prolonged uphill journey, where the vehicle travels on an incline for an extended period of time, the amount of electrical power drawn from the battery increases, which may lead to the battery's state of charge (SOC) becoming low or the battery temperature rising.

[0006] If the state of charge (SOC) drops significantly or the battery temperature exceeds a set limit, the output power for driving the vehicle must be severely restricted, which may result in the vehicle not being able to be operated according to the driver's requirements for a longer period of time.

[0007] Consequently, the aim of the invention is to create a control device for an electric vehicle that is able to suppress battery load even during a prolonged uphill drive. Solution to the problem

[0008] According to one aspect of the invention, a control device for an electric vehicle is provided, comprising: a generator motor for generating electrical power; a traction motor for propelling the electric vehicle; and a battery that is to be charged with the electrical power generated by the generator motor and is configured to supply the electrical power to the traction motor, wherein the control device comprises: a control unit for detecting a gradient of a road on which the electric vehicle is currently traveling in order to limit a maximum speed of the electric vehicle based on the detected gradient, wherein, while the electric vehicle is traveling on the road, the control unit limits an output power of the traction motor in order to limit the maximum speed if the detected gradient is equal to or greater than a predetermined threshold. Advantageous modes of operation of the invention

[0009] Consequently, it is possible to suppress battery load even during a prolonged uphill drive. Brief description of the drawings Fig. Figure 1 is a diagram of an electric vehicle in which a control device according to an embodiment of the invention is installed. Fig. Figure 2 is a diagram illustrating a relationship between a throttle opening and a vehicle speed, characteristic of an example in which a maximum speed is limited according to a gradient of a roadway by the control device according to the embodiment of the invention. Fig. Figure 3 is a flowchart of procedures of a drive power limitation process that is executed by the control device according to the embodiment of the invention. Fig. Figure 4 is a time sequence diagram of an example of a vehicle state transition during the drive power limitation process to be carried out by the control unit according to the embodiment of the invention. Description of exemplary implementations

[0010] A control device according to an embodiment of the invention is installed in an electric vehicle, which includes: a generator motor for generating electrical power; a traction motor for driving the electric vehicle; and a battery that is to be charged with the electrical power generated by the generator motor and is configured to supply the electrical power to the traction motor, wherein the control device comprises: a control unit for detecting a gradient of a road on which the electric vehicle is currently traveling in order to limit a maximum speed of the electric vehicle based on the detected gradient, wherein, while the electric vehicle is traveling on the road, the control unit limits an output power of the traction motor in order to limit the maximum speed if the detected gradient is equal to or greater than a predetermined threshold.

[0011] Consequently, it is possible to suppress battery overload even during a prolonged uphill drive. Examples of implementation

[0012] The following describes a control unit of an electric vehicle according to an embodiment of the invention with reference to the drawings.

[0013] As in Fig. As shown in Figure 1, an electric vehicle 1 equipped with the control device according to the embodiment comprises an internal combustion engine 2 (hereinafter simply referred to as: machine), a generator motor 3, a traction motor 4, a differential 5, drive wheels 6, an inverter 7 for the generator motor (hereinafter referred to as "first inverter"), an inverter 8 for the traction motor (hereinafter referred to as "second inverter"), a battery 9 and an ECU 10 (Electronic Control Unit) as a control unit.

[0014] Machine 2 has multiple cylinders. Machine 2 is configured here such that each cylinder performs a series of four strokes: an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0015] The generator motor 3 contains a rotating shaft that is connected to an output shaft of the machine 2. Therefore, the generator motor 3 can generate electrical power through the driving force of the machine 2. The generator motor 3 supplies the generated electrical power to the traction motor 4 and / or the battery 9.

[0016] The traction motor 4 contains a rotating shaft that is connected to the left and right drive wheels 6 via the differential 5. Therefore, the traction motor 4 has a motor function for driving the drive wheels 6 with electrical power supplied by the generator motor 3 and / or the battery 9, and it also has a generator function for converting electrical power into a counter-drive force input from the differential 5.

[0017] The first inverter 7 for the generator motor is controlled by the ECU 10 to convert the three-phase alternating current generated by the generator motor 3 into direct current power in order to supply it to the second inverter 3 for the traction motor and / or to charge the battery 9.

[0018] The second inverter 8 for the traction motor is controlled by the ECU 10 to convert the DC power supplied by the generator motor 3 via the first inverter 7 or from the battery 9 into DC power in order to supply the traction motor 4 with the converted power. Furthermore, the second inverter 8 is configured for control by the ECU 10 so that the AC power supplied by the traction motor 4 is converted into DC power in order to charge the battery 9.

[0019] The battery 9 is a secondary battery, for example a lithium-ion battery, it is electrically connected to both the motor generator 3 and the traction motor 4 in order to be charged by the electrical power generated by the generator motor 3 or by the electrical power generated in the traction motor 4 (that is, by the regenerated electrical power).

[0020] The electric vehicle 1 also includes an accelerator pedal 90, which is operated by the driver. An accelerator pedal opening sensor 91 detects the actuation stroke of the accelerator pedal 90 (i.e., the degree of depressurization).

[0021] The accelerator pedal opening sensor 91 is connected to the ECU 10, which detects the extent of depressing the accelerator pedal 90 as accelerator pedal opening and sends a corresponding signal to the ECU 10.

[0022] The ECU 10 is formed by a computer unit that includes a central processing unit (CPU), a read / write memory (RAM), a solid-state memory (ROM), a flash memory for storing backup data and the like, an input port and an output port.

[0023] The computer unit's ROM stores a program to instruct the computer unit to function as the ECU 10; it also stores various constants, maps, and the like.

[0024] This means that the CPU uses RAM as working memory to execute the program stored in the ROM, thereby causing the computer unit to function as the ECU 10.

[0025] The input port of the ECU 10 is connected to various sensors, including the accelerator pedal opening sensor 91 mentioned above, a speedometer (vehicle speed sensor) 92 and a gradient sensor 93.

[0026] The speedometer 92 is configured to detect the speed of vehicle 1 (hereinafter referred to simply as "vehicle speed").

[0027] The gradient sensor 93, for example in the form of a gyroscope or an accelerometer, is configured to detect the angle of the electric vehicle 1's forward direction relative to a horizontal plane (i.e., the tilt angle of the electric vehicle 1 with respect to the horizontal plane, where the value is either positive or negative) as the gradient of a road (hereinafter: "road gradient") on which the electric vehicle 1 is currently stopped or driving. Sensor information (namely a voltage signal) is transmitted (sent) to the ECU 10, which is characteristic of the detected angle.

[0028] For example, the gradient sensor 23 can determine a positive / negative angle as a road gradient when the vehicle 1 is driving on an uphill or downhill roadway.

[0029] The ECU 10 is configured to regulate vehicle speed according to the accelerator pedal opening (i.e., the extent to which the accelerator pedal is depressed), but to limit a maximum speed (a vehicle speed limit) of the electric vehicle 1 according to the road gradient.

[0030] For example, if electric vehicle 1 is traveling on an uphill road with a constant gradient, the ECU 10 increases the vehicle speed as the accelerator pedal is opened until it reaches a predetermined opening value. However, once the accelerator pedal opening exceeds the predetermined opening value, the ECU 10 maintains the vehicle speed at a certain level to avoid exceeding the maximum speed determined by the road gradient (i.e., a limit for the maximum speed).

[0031] In other words, the ECU 10 maintains the vehicle speed at a limit depending on the road gradient, even when the accelerator pedal is fully depressed.

[0032] In particular, when the electric vehicle 1 is driving on a road and its determined gradient (for example, a positive value) corresponds to or is greater than a determination threshold (a positive value), the ECU 10 limits the output power of the traction motor 4 according to the determined road gradient in order to limit the maximum speed.

[0033] This means: while the electric vehicle 1 is driving on an incline with predetermined gradients or greater, the ECU 10 sets the limit value for the maximum speed according to the size of the road gradient and causes the traction motor 4 to deliver a drive torque according to the opening of the drive lever in order to increase the vehicle speed, however, the output power of the traction motor 4 is limited in such a way that the vehicle speed does not exceed the set limit.

[0034] For example, the ECU 10 does not limit the maximum speed (that is, the vehicle speed limit preset for the electric vehicle 1) when the electric vehicle 1 is traveling on a road surface with a gradient smaller than a predetermined one (for example, on a substantially level road surface or on a sloping road surface), but it does lower the maximum speed limit (that is, it sets the maximum speed to a smaller value) when the road surface gradient is greater, while the electric vehicle 1 is traveling on a road surface with a predetermined gradient or an even steeper gradient.

[0035] To limit the maximum speed, the ECU 10 controls the second inverter 8 in such a way as to limit the electrical drive power for the motor 4 in order to limit motor torque in contrast to a driver requirement.

[0036] The predetermined threshold is a lower limit (positive value) for the road gradient, above which the state of charge (SOC) may drop drastically and / or the battery temperature may rise. Such a threshold can be determined experimentally in advance, for example.

[0037] When the electric vehicle 1 travels on an incline with the predetermined gradient or an even greater gradient, the gradient sensor 93 determines the road gradient of the determination threshold value or above.

[0038] Furthermore, while the electric vehicle 1 is traveling on an uphill road with a predetermined gradient or above, the ECU 10 can limit the output power of the traction motor 4 in order to limit the maximum speed, provided that the detected road gradient reaches or exceeds the determination threshold for a predetermined time period (time threshold) or above (i.e., provided that the gradient sensor 93 detects the road gradient as being equal to or greater than the determination threshold for the minimum predetermined time period). In other words, under such a condition, the ECU 10 can limit the output power of the traction motor 4.

[0039] The time threshold is a lower limit for the duration of continuous driving on a road with a determined gradient equal to or exceeding the threshold (i.e., an uphill section with a predetermined gradient or greater). This means that if a period of such continuous driving equals or exceeds the time threshold, the state of charge (SOC) is likely to decrease and / or the battery temperature is likely to increase.

[0040] Such a time threshold can, for example, be determined experimentally in advance.

[0041] During the power output limitation for the traction motor 4, the ECU 10 limits the maximum speed according to the gradient of an uphill section on which the electric vehicle 1 is currently traveling (that is, the current value of the road gradient determined by the gradient sensor 93). The ECU 10 then sets the maximum speed to a value that decreases as the road gradient increases.

[0042] As in Fig. As shown in Figure 2, for example, the ECU 10 changes a maximum speed (that is, the upper limit of the vehicle speed) for a vehicle speed depending on the accelerator pedal opening, according to the gradient of the rising road surface on which the electric vehicle 1 is currently driving. Fig. Figure 2 shows an example of a relationship between accelerator pedal opening and vehicle speed for each of the three following cases: - the electric vehicle 1 travels continuously on a level roadway (dashed line); - The electric vehicle 1 travels on a level roadway and then on an ascending roadway with a gentle gradient (colon-dash line); and - The electric vehicle 1 travels on a level road and then travels on an incline with a steep gradient (solid line).

[0043] In particular, when the accelerator lever opening increases, the ECU 10 increases the drive torque to increase the vehicle speed. However, it limits the vehicle speed (i.e., the drive torque) to prevent exceeding the maximum speed, which depends on the road gradient (limit for the maximum speed). For example, if the limit to which the vehicle speed is restricted is 40 km / h while driving uphill with a certain gradient, then the maximum speed of the electric vehicle 1 will be 40 km / h (i.e., the electric vehicle 1 is allowed to travel at 40 km / h or less).

[0044] If according to Fig. 2. If the electric vehicle 1 travels on a road surface with a gentle gradient that is greater than that of a level road surface, the maximum speed is limited so that it is lower than if the vehicle 1 were traveling on a level road surface with a gentle gradient. Similarly, if the electric vehicle 1 travels on a road surface with a steep gradient that is greater than the gradient of a gently sloping road surface, the maximum speed is further limited so that it is lower than if the electric vehicle 1 were traveling on a road surface with a moderate gradient.

[0045] Next, we will use the Fig. Section 3 describes the drive output power limitation process, which is executed by the control unit of this embodiment. This drive output power limitation process is to begin when the vehicle is started and be repeated at a predetermined interval during driving.

[0046] In step S1, the ECU 10 determines gradient information (hereinafter referred to as "road gradient") from the gradient sensor 93, which is characteristic of a gradient of the road on which the electric vehicle 1 is currently driving.

[0047] After step S1, the ECU 10 goes to step S2.

[0048] In step S2, the ECU 10 determines whether the determined road gradient in step S1 corresponds to or exceeds the predetermined threshold.

[0049] For example, while the electric vehicle 1 is driving on an uphill road with a predetermined gradient or steeper, the ECU 10 determines that the determined road gradient is equal to or greater than the determination threshold.

[0050] If the determined road gradient corresponds to or is greater than the determination threshold value (“YES” in step S2), the ECU 10 goes to step S3.

[0051] Otherwise (“NO” in step S2), the ECU 10 goes to step S6.

[0052] In step S3, the ECU 10 increments a continuous time voltage determination counter by one.

[0053] After step S3, the ECU 10 goes to step S4.

[0054] In step S4, the ECU 10 determines whether the increased continuous time voltage determination counter according to step S3 corresponds to or exceeds a counter value threshold.

[0055] Such a counter threshold corresponds to a time threshold, as explained above. In other words, step S4 determines whether an elapsed time after the road gradient became equal to or greater than the set threshold (that is, a continuous travel time while driving uphill with a predetermined gradient or steeper) reaches the time threshold or not.

[0056] If it is determined that the continuous time span determination counter is equal to or greater than the counter threshold (“YES” in step S4), the ECU 10 goes to step S5.

[0057] Otherwise (“NO” in step S4) the ECU 10 terminates this drive output power limitation process.

[0058] In step S5, the ECU 10 limits an output power of the traction motor 4 (for example, the drive torque of the traction motor 4) according to the road gradient (that is, it sets the limit value for the maximum speed according to the road gradient and limits the drive torque or the like so that the vehicle speed does not exceed the set limit).

[0059] After step S5, the ECU 10 terminates the drive power output process.

[0060] In step S6, the ECU 10 resets the continuous time span determination counter to zero.

[0061] After step S6, the ECU 10 ends this drive power limitation process.

[0062] Next, we will use the Fig. 4. An example of a vehicle state transition during such a restriction process for drive power will be explained.

[0063] According to Fig. At time t1, the road gradient reaches the determination threshold, thus starting the countdown for the continuous travel time period. Subsequently, at time t1, the predetermined time period elapses during which the road gradient equals or exceeds the determination threshold (i.e., the continuous time period determination counter reaches the counter threshold), thereby activating a maximum speed limiter to limit the output power of the traction motor 4 according to the road gradient.

[0064] Simultaneously with step S2, the drive lever 90 is depressed to increase the drive lever opening. Subsequently, when the electrical power to drive the traction motor 4 is increased (i.e., when the power consumption of the traction motor 4 increases), the electrical power generated by the generator motor 3 increases; however, the electrical power stored in the battery 9 is also consumed to compensate for a decrease in the electrical power generated by the generator motor 3.

[0065] The in Fig. The four dashed lines shown represent a comparison example, namely the case without the drive power limitation process. The two dashed lines in a graph, representing the relationship between electrical power and time, indicate traction motor power consumption and battery power consumption in a comparison example.

[0066] As shown by the dashed lines, without the power limitation for the traction motor 4, the vehicle speed should increase when the accelerator pedal 90 is pressed down according to the road gradient, i.e. the power consumption at the traction motor 4 should increase, while the electrical power stored in the battery 9 is consumed constantly.

[0067] In the exemplary embodiment (shown with solid lines, dashed lines and double-dotted lines in Fig. 4) The output power of the traction motor 4 is limited, thus enabling the electrical power generated by the generator motor 3 to cover the power consumption of the traction motor 4. That is, due to the limited maximum speed, the consumption of electrical power from the battery 9 (hereinafter also referred to as "battery power consumption") is reduced, even when the accelerator pedal 90 is depressed.

[0068] In the present embodiment, while the electric vehicle 1 is on a road with a road gradient that corresponds to or is greater than a determination threshold, the output power of the traction motor 4 is limited by the ECU 10 in order to limit the maximum speed of the electric vehicle 1.

[0069] For example, while the electric vehicle 1 is driving on an uphill road with the predetermined gradient or steeper, the output power of the traction motor 4 should be limited, which reduces the battery power consumption for the traction motor 4 and thus prevents the battery SOC value or the battery temperature from dropping or increasing sharply within a short time.

[0070] While the vehicle is traveling on the road, the ECU 10 can limit the output power of the traction motor 4 in order to restrict the maximum speed for as long as a predetermined period of time elapses while the road gradient is equal to or greater than the determining threshold.

[0071] During driving, provided that the ECU 10 continuously determines the set threshold value or an even higher value for the road gradient for a minimum period of time, the ECU 10 can allow the power limitation for the traction motor 4 in order to limit the output power of the traction motor 4 according to the road gradient (that is, it can set the limit for the maximum speed according to the road gradient and can regulate the output power of the traction motor 4 so that the vehicle speed does not exceed the set limit).

[0072] In this case, the power limitation for the traction motor 4 is necessary to suppress a drop in battery charge or a rise in battery temperature if the battery charge level or temperature is likely to drop or rise sharply within a short period of time.

[0073] The ECU 10 can adjust the maximum speed according to the road gradient so that it is limited together with the power limit for the traction motor 4.

[0074] For example, the ECU 10 can reduce the maximum speed (that is, set the maximum speed to a lower value) if the road gradient is greater.

[0075] In this case, a sharp drop in battery charge or a significant increase in battery temperature can easily occur; if the battery power consumption decreases, the battery charge can be effectively managed while minimizing any impact on driving behavior.

[0076] The ECU 10 can determine whether the restriction for the traction motor 4 should be executed, based on the battery SOC (%).

[0077] For example, the ECU 10 can prevent the power limitation for the traction motor 4 unless the battery SOC value is below a predetermined battery threshold.

[0078] Instead of the gradient sensor 93, map information from a navigation system can be used to obtain gradient information for the current position of electric vehicle 1. Alternatively, this value can be obtained from a server outside of electric vehicle 1 as gradient information (i.e., map information) regarding the current position of electric vehicle 1.

[0079] In the above embodiment, the ECU performs 10 different determinations and calculations based on information from different sensors, but there is no limitation to this.

[0080] The electric vehicle 1 can contain a communication unit that communicates with an external device, such as an external server, to operate based on information from various sensors transmitted by the communication unit. The communication unit receives the determination and calculation results from the external device. Different control functions can be executed using the received determination and calculation results.

[0081] While one or more embodiments of the invention have been disclosed, it is apparent to those skilled in the art that modifications are possible without deviating from the scope of protection of the invention. All such modifications and equivalents are covered by the appended claims. Reference symbol list 1 electric vehicle 2 Engine 3 Generator motor 4 traction motor 9 Battery 10 ECU control unit 90 Driving lever 91 Driving lever opening sensor 92 speedometer 93 Gradient sensor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2013 - 129 313 A

[0004]

Claims

[1] Control unit of an electric vehicle (1) which includes: a generator motor (3) for generating electrical power; a traction motor (4) for powering the electric vehicle (1); and a battery (9) which is to be charged with the electrical power generated by the generator motor (3) and is configured to supply the electrical power to the traction motor (4), the control unit features: a control unit (10) for detecting a gradient of a road on which the electric vehicle (1) is currently driving, in order to limit a maximum speed of the electric vehicle (1) on the basis of the detected gradient, wherein While the electric vehicle (1) is driving on the road, the control unit (10) limits the output power of the traction motor (4) in order to limit the maximum speed if the detected gradient is equal to or greater than a predetermined threshold. [2] Control device according to claim 1, wherein during the driving of the electric vehicle (1) the control unit (10) permits the output power limitation for the traction motor (4) under the condition that a predetermined time period or a longer time period elapses during which the detected gradient corresponds to the determined threshold value or more. [3] Control device according to claim 1 or 2, wherein the control unit (10): establishes a limit value for the maximum speed according to the detected gradient; and the output power of the traction motor (4) is limited in such a way that the vehicle speed does not exceed the established limit.

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