Hybrid vehicle

Abstract

To suppress delay in supercharging when switching series running to parallel running.SOLUTION: A hybrid vehicle 1 is equipped with: an engine 3 with a supercharger that can drive a driving wheel W and generate electricity through a generator 5; a motor 2 that can drive the driving wheel W with electricity of at least either of a battery 6 and the generator 5; and a control device 11 that switches between series running in which the motor 2 drives the driving wheel W and parallel running in which the engine 3 with a supercharger drives the driving wheel W, according to vehicle speed. When vehicle speed reaches predetermined parallel set-up vehicle speed in the series running, the control device 11 controls a state to a series supercharging state where a power generation load of the generator is increased and supercharging-pressure of the engine 3 with a supercharger is increased, and when vehicle speed reaches predetermined parallel transition vehicle speed in the series supercharging state, the control device switches the series running to the parallel running.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to hybrid vehicles. [Background technology]

[0002] Hybrid vehicles are equipped with an engine (internal combustion engine) and a motor (electric motor) as their driving power sources, and are broadly classified as series, parallel, or series-parallel depending on how they are used. The series system uses engine power to generate electricity in a generator to charge the battery, and the battery power is used to drive the motor to run the vehicle. The parallel system runs the vehicle primarily using engine power, with motor power providing additional driving assistance. The series-parallel system can switch between series and parallel modes depending on the vehicle's driving conditions.

[0003] In particular, the series-parallel system is advantageous in terms of fuel economy, as it runs on the motor when starting or running at low speeds, when engine efficiency is low, and on the engine when under high load or running at high speeds, when motor efficiency is low.Furthermore, by installing a supercharged engine, series-parallel hybrid vehicles can increase maximum output and improve acceleration performance in parallel running, even when the driver demands high acceleration.

[0004] However, turbochargers can experience a so-called turbo lag between when they start operating and when the engine's output torque increases, and this turbo lag can reduce acceleration performance immediately after switching from series to parallel driving, particularly when the turbocharger starts operating at the timing of switching from series to parallel driving. Furthermore, when the torque required of the motor is relatively high or when the battery's SOC (State of Charge) is low, it can be difficult to compensate for the turbo lag by driving the motor using battery power.

[0005] In response to such a situation, for example, a hybrid vehicle disclosed in Patent Document 1 increases the engine speed along the engine's optimum fuel efficiency line in response to the driver's acceleration request, making it easier for the engine to enter the supercharging range and suppressing supercharging response delays. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-131535 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the above-mentioned conventional technology, supercharging only begins after switching to parallel running, which requires time for air to be transported to the engine, for pressure to increase in the intake manifold, and for the turbo turbine to accelerate, so there is a risk that supercharging delay cannot be prevented.Furthermore, with the above-mentioned conventional technology, there is a possibility that the engine speed will temporarily drop due to axle rotation synchronization when switching from series running to parallel running, so there is a risk that supercharging delay cannot be suppressed by controlling the engine speed.

[0008] The present invention has been made in consideration of these problems, and its purpose is to provide a hybrid vehicle that can suppress supercharging delay when switching from series running to parallel running. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the hybrid vehicle of the present invention comprises a supercharged engine capable of driving drive wheels and generating electricity via a generator, a motor capable of driving the drive wheels using power from at least one of a battery and the generator, and a control device that switches between series driving, in which the drive wheels are driven by the motor, and parallel driving, in which the drive wheels are driven by the supercharged engine, depending on the vehicle speed, and when the vehicle speed in the series driving reaches a predetermined parallel preparation vehicle speed, the control device controls the vehicle to a series supercharged state in which the power generation load of the generator is increased to increase the supercharging pressure of the supercharged engine, and when the vehicle speed in the series supercharged state reaches a predetermined parallel transition vehicle speed, the control device switches to parallel driving. [Effects of the Invention]

[0010] The present invention provides a series-parallel hybrid vehicle that increases the boost pressure of a supercharged engine during a preparation period before switching from series running to parallel running, thereby preventing so-called turbo lag, which is a temporary drop in engine output during the switch. Furthermore, the hybrid vehicle of the present invention can prevent turbo lag by preparing a boost pressure sufficient for the engine output after the switch during the preparation period before switching running modes. Therefore, the hybrid vehicle and control method thereof of the present invention can suppress a boost delay when switching from series running to parallel running. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a main configuration of a hybrid vehicle according to the present invention; [Figure 2] 4 is a flowchart showing a control procedure of the control device. [Figure 3] 10 is a waveform showing vehicle information etc. when the first supercharging mode is selected in a series supercharging state. [Figure 4] 10 is a waveform showing vehicle information etc. when the second supercharging mode is selected in a series supercharging state. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the contents described below, and can be implemented with any modifications within the scope that does not change the gist of the disclosure. Furthermore, all drawings used to explain the embodiments are schematic representations of components, and may be partially emphasized, enlarged, reduced, or omitted to facilitate understanding, and may not accurately represent the scale, shape, etc. of the components.

[0013] 1 is a block diagram showing the main configuration of a hybrid vehicle 1 according to the present invention. The hybrid vehicle 1 runs by driving drive wheels W with at least one of a motor 2 (electric motor) and a supercharged engine 3 (internal combustion engine), and employs a series-parallel system that can switch between series running and parallel running depending on the running state, as will be described later.

[0014] In addition to the above configuration, the hybrid vehicle 1 according to this embodiment also includes a clutch 4, a generator 5, a battery 6, an inverter 7, an accelerator sensor 8, a brake sensor 9, a vehicle speed sensor 10, and a control device 11. The control device 11 includes an HV-ECU 12 and an engine ECU 13.

[0015] The motor 2 is a traction electric motor that can drive the drive wheels W via the axles when supplied with electric power. The motor 2 may also be a motor generator (electric generator) that can generate regenerative power when the hybrid vehicle 1 decelerates.

[0016] The supercharged engine 3 is an internal combustion engine that outputs power using fuel such as gasoline, and is a so-called turbo engine that is equipped with a supercharger that uses the flow of exhaust gas to increase the density of the air it takes in, allowing it to increase output as needed.

[0017] The clutch 4 is a power transmission device that transmits or cuts off power from the supercharged engine 3 to the drive wheels W, and controls whether or not the driving force of the supercharged engine 3 is used to drive the hybrid vehicle 1.

[0018] The generator 5 is a generator capable of generating electricity using the power output from the supercharged engine 3, and controls the amount of power generation within the range of the output of the supercharged engine 3 by controlling the power generation load.

[0019] The battery 6 is an electricity storage device made up of a lithium ion battery or a nickel-metal hydride battery, and outputs the electric power required to drive the motor 2, as well as supplies electric power to various electrical devices (not shown) mounted on the hybrid vehicle 1.

[0020] The inverter 7 is a power conversion device that converts DC power and AC power, and can drive the motor 2 by supplying the motor 2 with power output from at least one of the generator 5 and the battery 6, and can charge the battery 6 by supplying the battery 6 with power output from the generator 5. Furthermore, if the motor 2 is capable of regenerative power generation, the inverter 7 may charge the battery 6 with the generated power.

[0021] The accelerator sensor 8 is a so-called APS (accelerator position sensor) that detects accelerator operation by the driver of the hybrid vehicle 1. The brake sensor 9 is a sensor that detects brake operation by the driver of the hybrid vehicle 1. The vehicle speed sensor 10 is a sensor that detects the vehicle speed in order to determine the traveling state of the hybrid vehicle 1.

[0022] The control device 11 is composed of, for example, a microcomputer control circuit, and performs integrated control of the entire vehicle by receiving status signals and transmitting control signals to and from each drive system of the hybrid vehicle 1 shown in FIG. 1 as well as various electrical devices and auxiliary equipment not shown.

[0023] More specifically, the HV-ECU 12 receives various vehicle information from, for example, the accelerator sensor 8, the brake sensor 9, and the vehicle speed sensor 10 to grasp the acceleration request and the driving state, and controls the motor 2, the battery 6, and the inverter 7 based on this information, thereby mainly performing power interchange via the inverter 7 and driving management using the motor 2. In other words, the HV-ECU 12 controls the output (rotation speed and / or torque) of the motor 2 by managing the power supply to the motor 2 via the inverter 7 while monitoring the SOC (State Of Charge) of the battery 6.

[0024] Furthermore, the HV-ECU 12 performs cooperative control with the engine side by mutually transmitting and receiving control information to and from the engine ECU 13 connected via vehicle communication such as a CAN (Controller Area Network).

[0025] The engine ECU 13 controls the output (rotation speed and / or torque) of the supercharged engine 3, and also controls the power generation load of the generator 5. The engine ECU 13 also controls the supercharging pressure in the engine by adjusting the opening of a wastegate valve (not shown) in the supercharger of the supercharged engine 3.

[0026] The drivetrain configuration described above allows the hybrid vehicle 1 to selectively switch between multiple driving states. For example, when the hybrid vehicle 1 starts moving, the supercharged engine 3 and the generator 5 are stopped, and the HV-ECU 12 controls the drive of the motor 2 using power from the battery 6, thereby enabling energy-efficient EV driving at low speeds.

[0027] In addition, when driving with relatively low acceleration requirements, the power generated by the generator 5 using the power of the turbocharged engine 3 can be allocated to charging the battery 6 via an inverter, and the vehicle can be switched to series driving, in which the motor 2 is driven and controlled using the power of the battery 6.

[0028] Furthermore, when driving with a relatively high acceleration requirement, the clutch 4 can be connected to control the drive using the power of the turbocharged engine 3, and if necessary, the drive can be switched to parallel driving, which uses the power of the battery 6 to drive the motor 2 and assist the drive.

[0029] Next, a control method for the hybrid vehicle 1 relating to switching of the driving mode will be described. FIG. 2 is a flowchart showing the control procedure of the control device 11. Here, a description of EV driving will be omitted. The control device 11 switches between series driving and parallel driving depending on the driving state by repeatedly executing the control procedure shown in FIG. 2 while the hybrid vehicle 1 is driving. It is assumed that the control procedure is started during series driving and when the supercharged engine 3 has a supercharging mode, which will be described later, turned off.

[0030] When the control procedure is started in series running, the control device 11 acquires vehicle information from each sensor of the hybrid vehicle 1 (step S1). More specifically, the HV-ECU 12 calculates an acceleration request based on APS information from the accelerator sensor 8, acquires the vehicle speed from the vehicle speed sensor 10, and acquires the SOC from the battery 6.

[0031] The control device 11 also determines whether the vehicle speed of the hybrid vehicle 1 has reached a predetermined parallel preparation vehicle speed (step S2). Here, the parallel preparation vehicle speed is a vehicle speed threshold that is arbitrarily set in advance to determine the start of a switching preparation period before switching from series running to parallel running, and is set to 60 km / h in this embodiment.

[0032] If it is determined that the vehicle speed is less than the parallel preparation vehicle speed (No in step S2), the control device 11 maintains the supercharging mode of the supercharged engine 3 in the OFF state (step S3) and continues series driving of the hybrid vehicle 1 (step S4).

[0033] On the other hand, if it is determined that the vehicle speed has reached the parallel preparation vehicle speed (Yes in step S2), the control device 11 determines whether the vehicle speed has reached a predetermined parallel transition vehicle speed (step S5). Here, the parallel transition vehicle speed is a vehicle speed threshold that is arbitrarily set in advance to determine the timing to switch from series running to parallel running upon completion of the above-mentioned preparation period, and is set to 70 km / h in this embodiment.

[0034] During the preparation period between the parallel preparation speed and the parallel transition speed, a preparatory operation is performed to increase the supercharging pressure in advance so that the supercharger of the supercharged engine 3 can provide output assistance when switching to parallel running later, as will be described below.

[0035] If it is determined that the vehicle speed is less than the parallel transition vehicle speed (No in step S5), the control device 11 determines whether the acceleration request calculated in step S1 is equal to or greater than a predetermined acceleration threshold (step S6). Here, the acceleration threshold is a threshold for the APS information for selecting an operation mode of the supercharged engine 3 so that the vehicle can travel in accordance with the acceleration request made by the driver.

[0036] If it is determined that the acceleration request is less than the predetermined acceleration threshold (No in step S6), the control device 11 determines whether the SOC of the battery 6 is equal to or greater than a predetermined SOC threshold (step S7). Here, the SOC threshold is a threshold that is set in advance to determine whether the remaining power of the battery 6 is sufficient for driving the vehicle and for operating various electrical devices.

[0037] If it is determined that the SOC is equal to or greater than the SOC threshold (Yes in step S7), the control device 11 determines that there is sufficient time until the parallel transition vehicle speed and sufficient remaining power in the battery 6, and sets the operating mode of the supercharged engine 3 to the first supercharging mode (step S8).

[0038] Here, the first supercharging mode is an operating mode in which the supercharger of the supercharged engine 3 increases the supercharging pressure in the engine within a predetermined first supercharging pressure range, i.e., a relatively low supercharging pressure range. In other words, when the acceleration request is relatively low, preparation for transition to parallel running is performed by relatively gradually increasing the supercharging pressure of the supercharged engine 3 during the preparation period until the vehicle speed reaches the parallel transition vehicle speed. At this time, surplus electric power generated by the supercharged engine 3 via the generator 5 is used to charge the battery 6.

[0039] On the other hand, if it is determined that the acceleration request is equal to or greater than a predetermined acceleration threshold (Yes in step S6), or if it is determined that the SOC is less than the SOC threshold (No in step S7), the control device 11 determines that there is insufficient margin for either the time until the parallel transition vehicle speed or the remaining power of the battery 6, and sets the operating mode of the supercharged engine 3 to the second supercharging mode (step S9).

[0040] Here, the second supercharging mode is an operating mode in which the supercharger of the supercharged engine 3 increases the supercharging pressure in the engine to a predetermined second supercharging pressure range that is higher than the above-mentioned first supercharging pressure range, i.e., a relatively high supercharging pressure range. In other words, in the second supercharging mode, the supercharging pressure of the supercharged engine 3 is increased as quickly as possible in preparation for the case in which the parallel transition vehicle speed is reached in a short period of time. At this time, the amount of power generated by the generator 5 also increases as the output of the supercharged engine 3 increases, so that charging the battery 6 can prevent depletion of power for driving.

[0041] Furthermore, when the second supercharging mode is set, there is a possibility that the amount of power generated by the generator 5 may be excessive, so the HV-ECU 12 adjusts the power output distribution (step S10). More specifically, the HV-ECU 12 supplies part of the power from the generator 5 to the inverter 7 to the motor 2 as driving power, and also supplies it to the battery 6 and various electrical devices of the hybrid vehicle 1, but distributes the power so that the power supplied to the battery 6 is not excessive and so that the output of the motor 2 is not excessive or insufficient relative to the required output.

[0042] In this way, during the preparation period when the vehicle speed is from the parallel preparation vehicle speed to the parallel transition vehicle speed, the hybrid vehicle 1 is controlled to a series supercharged state in which series running continues while the supercharger of the supercharged engine 3 is operating.

[0043] Then, when the vehicle speed reaches the parallel transition vehicle speed (Yes in step S5), the control device 11 synchronizes the rotation of the motor 2 and the supercharged engine 3, and performs control to switch the output of the supercharged engine 3 to driving power by directly connecting the clutch 4 to the drive wheels W (step S11). As a result, the hybrid vehicle 1 switches to parallel running, which is highly fuel-efficient at high speeds, and runs.

[0044] The control device 11 also calculates the deviation between the required torque during parallel running and the actual torque being output for running, and determines whether the deviation is equal to or greater than a predetermined torque threshold (step S12). Here, the predetermined torque threshold is a torque threshold that is set in advance to determine whether the output torque for running is sufficient in the parallel running state.

[0045] If the deviation is less than the torque threshold value (No in step S12), the control device 11 determines that sufficient torque for driving is being output, and stops the supercharging pressure control of the supercharged engine 3. This causes the hybrid vehicle 1 to enter a cruising state using parallel driving.

[0046] On the other hand, if the deviation is equal to or greater than the torque threshold value (Yes in step S12), the control device 11 determines that the driving torque is not being output sufficiently, and performs parallel driving while continuing control to increase the supercharging pressure of the supercharged engine 3 (step S14). Furthermore, the control device 11 may limit power generation by reducing the power generation load of the generator 5 in order to preferentially allocate the output of the supercharged engine 3 to acceleration of the hybrid vehicle 1 (step S15).

[0047] The above series of steps are then repeated, and if the vehicle speed again drops below the parallel vehicle speed, the first supercharging mode or the second supercharging mode is stopped and the vehicle switches to series running (steps S3 and S4). This allows the hybrid vehicle 1 to switch between series running and parallel running according to the vehicle speed, and by providing a series supercharging state as a preparation period before switching to parallel running, it is possible to prevent a drop in output at the timing of the switch.

[0048] Next, we will explain the changes in the state of the drivetrain when switching from series running to parallel running. Figure 3 shows waveforms that represent vehicle information, etc. when the first supercharging mode is selected in series supercharging. Figure 4 shows waveforms that represent vehicle information, etc. when the second supercharging mode is selected in series supercharging.

[0049] As shown in Figure 3, when the driver requests acceleration of hybrid vehicle 1 running in series at approximately 20 km / h, the APS increases as shown at timing t1, causing the drivetrain parameters to increase and vehicle speed to also increase. However, because the vehicle speed at this point does not reach the parallel preparation vehicle speed described above, the boost pressure of supercharged engine 3 remains at a pressure corresponding to the engine speed. Also, even if the APS reaches 100% during this period, the vehicle will remain in series running unless it reaches the parallel preparation vehicle speed.

[0050] On the other hand, when the vehicle speed reaches or exceeds 60 km / h, which is the parallel running preparation speed, at timing t2, the generator 5's power generation load is increased and the supercharging pressure of the supercharged engine 3 is increased, thereby entering a series supercharged state, which is a preparation period for switching to parallel running. At this time, the rotation speed of the supercharged engine 3 will decrease due to axle rotation synchronization.

[0051] Then, at timing t3, when the vehicle speed reaches or exceeds 70 km / h, which is the parallel transition speed, the drive system switches from series running to parallel running, and the power generation load of generator 5 is adjusted to achieve a smooth transition to the running load.The previously increased boost pressure can suppress a decrease in engine output, preventing a delay in boost response.

[0052] Furthermore, as shown in Figure 4, if the APS increased at time t1 is maintained thereafter, the vehicle speed reaches the parallel preparation vehicle speed at time t2 while the acceleration request remains relatively large. At this time, the second supercharging mode is selected in response to the magnitude of the acceleration request, causing a rapid increase in the power output of the generator 5 and the supercharging pressure of the supercharged engine 3. In this case, the rotation speed of the supercharged engine 3 temporarily increases to increase the intake volume, and then decreases a short time after time t2 due to axle rotation synchronization.

[0053] Furthermore, in the second supercharging mode, the surplus electric power from the generator 5, which is generated by the power of the supercharged engine 3, is used to run the hybrid vehicle 1, so that the output of the battery 6 can be suppressed.

[0054] Then, at timing t3, when the vehicle speed reaches or exceeds the parallel transition vehicle speed, the drivetrain switches from series running to parallel running, and the previously increased boost pressure suppresses a decrease in engine output, thereby preventing a delay in boost response.

[0055] As described above, the series-parallel hybrid vehicle 1 according to the present invention can prevent so-called turbo lag, which is a temporary drop in engine output at the time of switching from series running to parallel running, by increasing the boost pressure of the supercharged engine 3 during the preparation period before switching from series running to parallel running. Furthermore, the hybrid vehicle 1 according to the present invention can prevent turbo lag even if the rotation speed of the supercharged engine 3 temporarily drops due to axle rotation synchronization, by preparing a boost pressure sufficient for the engine output after switching during the preparation period before switching running modes. Therefore, the hybrid vehicle 1 according to the present invention can suppress a boost delay when switching from series running to parallel running.

[0056] Although the description of the embodiment is now complete, the hybrid vehicle 1 according to the present invention is not limited to the above embodiment. For example, in the above embodiment, as shown in Fig. 2, the second supercharging mode is selected when it is determined that the SOC is less than the SOC threshold value in the series supercharging state (No in step S7), but the second supercharging mode may be selected on the condition that the output of the battery 6 is less than the electric power required for traveling. In other words, the second supercharging mode may be forcibly selected when the battery 6 is extremely hot or cold and cannot supply electric power.

[0057] In addition, in the above embodiment, the parallel preparation speed and the parallel transition speed are fixed values ​​that are set in advance, but if the output of the supercharged engine 3 is transmitted via a transmission, for example, they may be variable values ​​that include the gear ratio of the transmission during driving as a variable. Also, adjustments may be made to reduce the values ​​of the parallel preparation speed and the parallel transition speed in response to a decrease in output due to an abnormal temperature of the battery 6 or a decrease in SOC, in which case the output of the supercharged engine 3 can be increased before it becomes difficult to provide a stable power supply from the battery 6.

[0058] Furthermore, in the above embodiment, an example was given of switching to parallel running when the vehicle speed reaches or exceeds the parallel transition vehicle speed, but it is also possible to switch to parallel running regardless of the vehicle speed when the output torque of motor 2 reaches the upper limit of the torque characteristics. [Explanation of symbols]

[0059] 1 Hybrid vehicle 2 motors 3. Supercharged engine 4. Clutch 5. Generator 6 Battery 7 inverters 8 Accelerator Sensor 9 Brake Sensor 10 Vehicle speed sensor 11 Control device 12 HV-ECU 13 Engine ECU W drive wheels

Claims

1. a supercharged engine capable of driving drive wheels and generating electricity via a generator; a motor capable of driving the drive wheels using electric power from at least one of a battery and the generator; a control device that switches between series running in which the drive wheels are driven by the motor and parallel running in which the drive wheels are driven by the supercharged engine in accordance with vehicle speed; The control device When the vehicle speed reaches a predetermined parallel preparation vehicle speed during the series running, the generator is controlled to a series supercharged state in which the power generation load of the generator is increased to increase the supercharging pressure of the supercharged engine, The hybrid vehicle switches to the parallel running when the vehicle speed reaches a predetermined parallel transition vehicle speed in the series supercharging state.

2. The control device, in the series supercharging state, When the acceleration request is less than a predetermined acceleration threshold, a first supercharging mode is set in which the supercharging pressure is increased to a predetermined first supercharging pressure range; 2. The hybrid vehicle according to claim 1, wherein when the acceleration request is equal to or greater than the acceleration threshold, the hybrid vehicle is set to a second supercharging mode in which the supercharging pressure is increased to a predetermined second supercharging pressure range that is higher than the first supercharging pressure range.

3. 3. The hybrid vehicle according to claim 2, wherein the control device sets the hybrid vehicle to the second supercharging mode regardless of the acceleration request when the SOC of the battery is lower than a predetermined SOC threshold.

4. In the first supercharging mode, the motor is driven by electric power from the battery, 3. The hybrid vehicle according to claim 2, wherein in the second supercharging mode, the motor is driven by electric power from the generator.

5. 3. The hybrid vehicle according to claim 2, wherein the control device sets the hybrid vehicle to the second supercharging mode regardless of the acceleration request when the output of the battery is less than the electric power required for traveling.

6. 3. The hybrid vehicle according to claim 1, wherein the control device reduces the parallel preparation vehicle speed in response to a decrease in the output of the battery.

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