Control device

Abstract

To provide a control device which can improve the fuel consumption of a hybrid vehicle.SOLUTION: An engine is basically controlled to operate at an operation point on an optimum fuel consumption line. When the operation point of the engine according to the power generation request power is not included in a highest thermal efficiency region, a direction in which the total of the engine loss and the electric loss of each electric unit becomes low is read such that the electric loss does not exceed the engine loss on the basis of an engine output-loss difference relation and an engine output-electric loss relation, and the operation point (output) of the engine is moved in the direction.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control device for use in a hybrid vehicle (HV). [Background technology]

[0002] In series hybrid vehicles, the engine's power is converted into electricity by a generator motor (generator), which drives a drive motor, which then transmits the power of the drive motor to the drive wheels. Because the engine is separated from the drive wheels, the engine speed and engine torque can be freely controlled.

[0003] FIG. 5 is a diagram showing the optimum fuel economy line and the region of maximum thermal efficiency of the engine.

[0004] The optimal fuel economy line is a characteristic line that indicates a set of operating points (engine speed and engine torque) at which fuel consumption is minimized for the engine shaft output. The maximum thermal efficiency region is the region where the engine's maximum thermal efficiency is achieved.

[0005] In a series-type hybrid vehicle, depending on the driving conditions, the vehicle can be switched between an EV (Electric Vehicle) drive mode, in which the drive motor is driven only by the output of the battery, and a hybrid drive mode, in which the generator motor generates electricity using engine power, and the drive motor is driven by the combined power of the generator motor's output and the battery's output.

[0006] In the hybrid drive mode, a driving power requirement required for traveling and a power generation requirement, which is the amount of power required for the generator motor, are calculated, and the driving motor and the generator motor are controlled so that the driving power requirement and the power generation requirement are realized by the driving motor and the generator motor, respectively. The power generation requirement includes the power consumed by the driving motor, i.e., the driving power requirement, and a battery power requirement, which is the amount of charge and discharge required to keep the SOC (State Of Charge), which indicates the state of charge of the battery (the ratio of the remaining charge to the charge capacity), within the usage range.

[0007] At this time, the engine is controlled to operate at an operating point on the optimal fuel efficiency line. When the required power for generating electricity is high and the operating point of the engine corresponding to the required power for generating electricity is in a region higher than the maximum thermal efficiency region, the engine speed is reduced (the engine output is reduced) so that the operating point of the engine moves to the maximum thermal efficiency region, and the battery outputs the insufficient power. When the required power for generating electricity is low and the operating point of the engine corresponding to the required power for generating electricity is in a region lower than the maximum thermal efficiency region, the engine speed is increased (the engine output is increased) so that the operating point of the engine moves to the maximum thermal efficiency region, and the battery is charged with the surplus power output from the generator motor. This allows the engine to always be operated in the maximum thermal efficiency region. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2013-189113 A Summary of the Invention [Problem to be solved by the invention]

[0009] However, it has been found that by moving the engine's operating point from an operating point corresponding to the required power generation to an operating point included in the region of maximum thermal efficiency, losses may actually increase, increasing the engine's fuel consumption and worsening fuel economy.

[0010] An object of the present invention is to provide a control device that can improve the fuel efficiency of a hybrid vehicle. [Means for solving the problem]

[0011] In order to achieve the above-mentioned object, the control device of the present invention is a control device used in a hybrid vehicle equipped with a battery that charges and discharges electric power, an engine that outputs power, a generator motor that generates power using the power of the engine, and a drive motor that generates power for traveling, and has an engine output-loss difference relationship between the engine output and a loss difference between the engine loss that occurs when the engine is operated at a high thermal efficiency operating point where the thermal efficiency is equal to or higher than a predetermined value and the engine loss that occurs when the engine is operated at a low thermal efficiency operating point where the thermal efficiency is lower than that, and an engine output-electrical loss relationship between the engine output and the electrical loss that occurs when the loss difference is replaced with the electrical output of the battery, and changes the engine output based on the engine output-loss difference relationship and the engine output-electrical loss relationship.

[0012] According to this configuration, the output of the engine is changed based on the engine output-loss difference relationship and the engine output-electrical loss relationship.

[0013] For example, the engine output-loss difference relationship and the engine output-electrical loss relationship are compared, and the engine operating point is moved so that the electrical loss does not exceed the loss difference, thereby reducing the loss and improving the fuel efficiency of the hybrid vehicle. The engine output-loss difference relationship may be the relationship between the engine output and the loss difference between the engine loss occurring when the engine is operated at the maximum thermal efficiency operating point and the engine loss occurring when the engine is operated at another thermal efficiency operating point. Effect of the Invention

[0014] According to the present invention, the fuel economy of a hybrid vehicle can be improved. [Brief description of the drawings]

[0015] [Figure 1] 1 is a block diagram showing a configuration of a main part of a hybrid vehicle to which a control device according to an embodiment of the present invention is applied; [Diagram 2] FIG. 2 is a diagram showing the relationship between engine output and the loss difference between the engine loss occurring when the engine is operated at the maximum thermal efficiency operating point and the engine loss occurring when the engine is operated at another thermal efficiency operating point; [Diagram 3] 3 is a diagram showing the relationship between battery output and electrical loss in the case where the loss difference shown in FIG. 2 is replaced with battery output. FIG. [Figure 4] 5A and 5B are diagrams illustrating a relationship between an engine output and an engine loss difference, and a relationship between an engine output and an electrical loss. [Diagram 5] FIG. 2 is a diagram showing an optimum fuel economy line and a region of maximum thermal efficiency of an engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] <Main components of hybrid vehicles> FIG. 1 is a block diagram showing the configuration of a main part of a hybrid vehicle 1 to which a control device according to an embodiment of the present invention is applied.

[0018] The hybrid vehicle 1 is a vehicle equipped with a series hybrid system. The hybrid vehicle 1 is equipped with an engine 2, a generator motor (MG1) 3, and a drive motor (MG2) 4.

[0019] The engine 2 is, for example, a three-cylinder, four-stroke reciprocating engine. The engine 2 is provided with an electronic throttle valve for adjusting the amount of intake air into the combustion chamber, an injector (fuel injection device) for injecting fuel into the intake air, and an ignition plug for generating an electric discharge in the combustion chamber.

[0020] The generator motor 3 and the drive motor 4 are, for example, permanent magnet synchronous motors (PMSMs).

[0021] The generator motor 3 is a generator motor that generates electricity using the power of the engine 2, and is directly connected to the engine 2, for example, by being provided so that its rotating shaft rotates integrally with the crankshaft of the engine 2.

[0022] The drive motor 4 serves as a drive motor that generates power for driving the hybrid vehicle 1, and its rotating shaft is connected to a driving system of the hybrid vehicle 1. The driving system includes, for example, a differential gear 5, and a ring gear 6 of the differential gear 5 is meshed with a drive motor gear 7 that is provided so as to rotate integrally with the rotating shaft of the drive motor 4. The power generated by the drive motor 4 is transmitted from the drive motor gear 7 to the ring gear 6 of the differential gear 5, and is transmitted from the differential gear 5 to left and right drive wheels 9 via left and right drive shafts 8. This causes the drive wheels 9 to rotate, causing the hybrid vehicle 1 to travel forward or backward.

[0023] In addition, the hybrid vehicle 1 is equipped with a battery (BAT) 11 and a PCU (Power Control Unit) 12.

[0024] Battery 11 is an assembled battery made up of a combination of multiple secondary batteries. The secondary batteries are, for example, lithium ion batteries. Battery 11 outputs, for example, DC power of approximately 200 to 150 V (volts).

[0025] The PCU 12 is a unit for controlling the driving of the generator motor 3 and the drive motor 4, and includes inverters 13 and 14, a converter (CONV) 15, and an MGECU 16.

[0026] The inverter (INV1) 13 is a three-phase voltage type inverter that drives the generator motor 3, and has a configuration in which a series circuit of two IGBTs (Insulated Gate Bipolar Transistors) is provided corresponding to each of the U-phase, V-phase, and W-phase, and these series circuits are connected in parallel between a positive wiring and a negative wiring. When the generator motor 3 is in power running operation, the inverter 13 converts DC power to AC power and supplies the AC power to the generator motor 3. Furthermore, when the generator motor 3 is in regenerative operation (power generation operation), the inverter 13 converts the AC power generated by the generator motor 3 into DC power.

[0027] The inverter (INV2) 14 is a three-phase voltage type inverter that drives the drive motor 4, and similarly to the inverter 13, has a configuration in which two IGBT series circuits are provided corresponding to each of the U, V, and W phases, and these series circuits are connected in parallel to each other between a positive wiring and a negative wiring. When the drive motor 4 is in a power running operation, the inverter 14 converts DC power to AC power and supplies the AC power to the drive motor 4. Furthermore, when the drive motor 4 is in a regenerative operation (power generation operation), the inverter 14 converts the AC power generated by the drive motor 4 into DC power.

[0028] The converter 15 boosts the DC power output from the battery 11 and supplies it to the inverters 13, 14 when the generator motor 3 and the drive motor 4 are in power running mode. In addition, the converter 15 lowers the DC power output from the inverters 13, 14 and supplies it to the battery 11 when the generator motor 3 and the drive motor 4 are in regenerative running mode.

[0029] The hybrid vehicle 1 is equipped with a plurality of ECUs (Electronic Control Units), and the MGECU 16 is one of the plurality of ECUs. Each ECU is equipped with a microcontroller, and the microcontroller includes, for example, a CPU, a non-volatile memory such as a flash memory, and a volatile memory such as a dynamic random access memory (DRAM). The plurality of ECUs are connected to each other so as to enable two-way communication according to a CAN (Controller Area Network) communication protocol.

[0030] The multiple ECUs include an HVECU 17. The HVECU 17 is a unit that performs overall control of a hybrid system including the engine 2, the generator motor 3, and the drive motor 4. In controlling the generator motor 3 and the drive motor 4, the HVECU 17 transmits motor control commands to the MGECU 16, and the MGECU 16 controls the operations of the inverters 13, 14 and the converter 15 in accordance with the motor control commands.

[0031] In the hybrid vehicle 1, when starting the engine 2, power is supplied from the battery 11 to the generator motor 3, and the generator motor 3 is powered, thereby motoring (cranking) the engine 2 by the generator motor 3. When the rotation speed of the engine 2 has increased to a rotation speed required for firing due to motoring, the ignition plug of the engine 2 is sparked, and the engine 2 fires.

[0032] When the hybrid vehicle 1 is running, the drive motor 4 is powered and generates power. With the engine 2 stopped and the generator motor 3 not generating power, the drive motor 4 is driven by the output of the battery 11, causing the hybrid vehicle 1 to run as an EV (Electric Vehicle). With the engine 2 in operation (firing) and the generator motor 3 in a generating operation (regenerative operation), the drive motor 4 is driven by the combined power of the output (generated power) of the generator motor 3 and the output of the battery 11, causing the hybrid vehicle 1 to run as an HV.

[0033] When the hybrid vehicle 1 decelerates, the drive motor 4 is operated in a regenerative manner, and the power transmitted from the drive wheels to the drive motor 4 is converted into AC power. At this time, the drive motor 4 acts as a resistance in the traveling drive system, and this resistance acts as a braking force (regenerative braking force) that brakes the hybrid vehicle 1. At this time, the generated power of the drive motor 4 is also supplied to the battery 11, thereby charging the battery 11.

[0034] <Shifting the engine operating point> FIG. 2 is a diagram showing the relationship between engine output and the loss difference between the engine loss that occurs when engine 2 is operated at the maximum thermal efficiency operating point over the entire output range and the engine loss that occurs when engine 2 is operated at another thermal efficiency operating point.

[0035] In Fig. 2, the thick line indicates the maximum efficiency point loss, which is the engine loss that occurs in the engine 2 when the engine 2 operates in the maximum thermal efficiency region over the entire power range. Also, the thin line indicates the engine loss that occurs in the engine 2 when the engine 2 operates in a region other than the maximum thermal efficiency region over the entire power range. The engine loss when the engine 2 operates in a region other than the maximum thermal efficiency region is larger than the maximum efficiency point loss over the entire power range of the engine 2.

[0036] FIG. 3 is a diagram showing the relationship between the battery output and the electrical loss when the loss difference shown in FIG. 2 is replaced with the battery output.

[0037] The relationship shown in Fig. 3 is created from the relationship shown in Fig. 2. That is, a loss difference (engine loss difference) that is the difference between the engine loss and the maximum efficiency point loss is calculated, and when this loss difference is replaced with the battery output of battery 11, the total electrical loss occurring in each electrical unit including battery 11, inverters 13, 14, and converter 15 is calculated. Then, the battery output of battery 11 is associated with the electrical loss, thereby creating the relationship between the battery output and the electrical loss shown in Fig. 3.

[0038] FIG. 4 is a diagram showing the relationship between the engine output and the engine loss difference, and the relationship between the engine output and the electrical loss.

[0039] The engine output-loss difference relationship between the engine output and the engine loss difference is created by determining the loss difference, which is the difference between the engine loss and the maximum efficiency point loss for each engine output, and correlating the determined loss difference with each engine output.

[0040] The engine output-electrical loss relationship between the engine output and electrical loss is created by converting the relationship between the battery output and electrical loss shown in FIG. 3 into the relationship between the engine output and electrical loss.

[0041] The engine output-loss differential relationship and the engine output-electrical loss relationship are stored in the non-volatile memory of the HVECU 17.

[0042] In a mode in which the hybrid vehicle 1 runs as an HV (hybrid drive mode), a required driving power required for running and a required power generation power, which is the amount of power generation required of the generator motor 3, are calculated, and the generator motor 3 and the drive motor 4 are controlled so that the required driving power and the required power generation power are respectively realized by the drive motor and the generator motor 3. The required power generation includes the power consumed by the drive motor 4, i.e., the required driving power, and a required battery power, which is the amount of charge and discharge required to keep the SOC (State Of Charge) indicating the charge state of the battery 11 within a usage range.

[0043] At this time, the engine 2 is controlled to operate at an operating point on the optimal fuel efficiency line. If the operating point of the engine 2 according to the required power generation is not included in the maximum thermal efficiency region (see FIG. 5), the HVECU 17 moves the operating point (output) of the engine 2 based on the engine output-loss difference relationship and the engine output-electrical loss relationship.

[0044] Specifically, in regions A and B where the slope of the engine output-loss difference relationship is greater than the slope of the engine output-electrical loss relationship, there is a possibility that the electrical loss will fall below the engine loss if the engine output is reduced, and when the slope of the engine output-loss difference relationship is smaller than the slope of the engine output-electrical loss relationship, there is a possibility that the electrical loss will exceed the engine loss if the output of the battery 11 is increased. In regions A and B, the direction in which the engine loss and the sum of the electrical losses of each electrical unit are reduced is detected, and the operating point (output) of the engine 2 is moved in that direction so that the electrical loss does not exceed the engine loss.

[0045] <Effects> As described above, by shifting the operating point of the engine 2, the loss in the entire hybrid system can be reduced, and the fuel efficiency of the hybrid vehicle 1 can be improved.

[0046] <Modification> Although one embodiment of the present invention has been described above, the present invention can be embodied in other forms.

[0047] For example, the generator motor 3 does not have to be directly connected to the engine 2, and the rotating shaft of the generator motor 3 and the crankshaft of the engine 2 may be connected via a gear.

[0048] In addition, in the above-described embodiment, a hybrid vehicle 1 equipped with a series type hybrid system was given as an example of an electric vehicle, but the electric vehicle may be a hybrid vehicle equipped with a hybrid system of a type other than the series type.

[0049] In addition, various design modifications can be made to the above-described configuration within the scope of the claims. [Explanation of symbols]

[0050] 1: Hybrid vehicle 2: Engine 3: Generator motor 4: Drive motor 11:Battery 17: HVECU (control unit)

Claims

[Claim 1] A control device used in a hybrid vehicle equipped with a battery that charges and discharges electric power, an engine that outputs power, a power generation motor that generates power using the power of the engine, and a drive motor that generates power for traveling, comprising: An engine output-loss difference relationship between the output of the engine and a loss difference between an engine loss occurring when the engine is operated at a high thermal efficiency operating point where the thermal efficiency is equal to or higher than a predetermined value and an engine loss occurring when the engine is operated at a low thermal efficiency operating point where the thermal efficiency is lower than the high thermal efficiency operating point; and an engine output-electrical loss relationship between the output of the engine and an electrical loss that occurs when the loss difference is replaced with the electrical output of the battery; A control device that changes an output of the engine based on the engine output-loss difference relationship and the engine output-electrical loss relationship so that the electrical loss does not exceed the loss difference.

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