Hybrid vehicle power saving method

Abstract

To provide a hybrid vehicle power saving method that can improve fuel efficiency by power saving of an on-vehicle battery in an EV mode of a hybrid vehicle and ensure high responsiveness at the time of restarting of an engine in a compatible manner.SOLUTION: Provided is a power saving method of a hybrid vehicle which includes an engine 12 and a travel motor 14 as driving sources, and in which a torque converter 16 and an engine separation clutch 18 are disposed between the engine 12 and the travel motor 14 in a power transmission path from the engine 12 to driving wheels W, and a transmission 20 is disposed between the travel motor 14 and the driving wheels W, and which is configured to turn ON / OFF a lock-up clutch 16a provided at the torque converter 16 by hydraulic pressure supplied from an electric oil pump 24 or a mechanical oil pump 26. In a case where it is determined that a driver does not intend to start the vehicle when the hybrid vehicle is stopped in a travel mode and the brake is in an OFF state, power supply to the electric oil pump 24 is blocked and the lock-up clutch 16a is turned OFF.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a power saving method for a hybrid vehicle, and more particularly to a power saving method for a hybrid vehicle having an engine, a torque converter, a traction motor disposed between an engine disconnect clutch and a transmission, and in which the engine and the traction motor are disconnected when the hybrid vehicle is running in an electric vehicle mode. [Background technology]

[0002] Hybrid vehicles, which run on an engine and a traction motor as drive sources, have the advantage of being able to reduce exhaust gas and improve fuel efficiency by assisting the driving force of the engine with the traction motor. In such hybrid vehicles, the sharing of power between the engine and the traction motor is controlled by detecting the vehicle's running conditions, such as the accelerator opening and vehicle speed.

[0003] Some hybrid vehicles are equipped with a drive system that includes, from the engine to the drive wheels, a torque converter, an engine disconnect clutch, a drive motor, and a transmission, in that order from the engine side.While a torque converter has two advantages, namely a smooth clutch function and a torque amplification function, it has a problem in that it transmits power using oil as a medium, resulting in lower power transmission efficiency compared to mechanical clutches such as friction clutches.

[0004] Therefore, in the region where the torque amplification effect of the torque converter is weakened, i.e., the region where the torque amplification function is not required because the rotational speeds of the pump impeller and turbine runner are close to each other, the torque converter is provided with a lock-up clutch (LC) to directly connect the input and output shafts and ensure high power transmission efficiency.

[0005] This lock-up clutch is turned on (engaged) / off (disengaged) by hydraulic pressure supplied from an electric oil pump (EOP) or a mechanical oil pump (MOP).The electric oil pump is driven by electricity supplied from an on-board battery (auxiliary battery) that is installed separately from the driving motor, and the mechanical oil pump is driven by part of the engine power.

[0006] Furthermore, when the hybrid vehicle is in an EV mode in which the vehicle runs on electricity alone, the torque converter lockup clutch is kept ON even when the engine is stopped, in consideration of the responsiveness of the engine to be restarted. In this case, since the engine is stopped, a mechanical oil pump cannot be used, and the torque converter lockup clutch is operated by hydraulic pressure supplied from an electric oil pump. If the torque converter lockup clutch is kept ON in this manner, when the engine is restarted, the engine can be started by engaging the engine disconnect clutch.

[0007] However, if the electric oil pump is driven to keep the lock-up clutch of the torque converter in the ON state even when the engine is stopped in this manner, there is a problem that excessive power is consumed from the vehicle battery.

[0008] In relation to the above-mentioned problems, for example, Patent Document 1 discloses a vehicle equipped with an engine, an automatic transmission connected to the engine, and an electric oil pump for supplying hydraulic pressure to the automatic transmission. This vehicle is an engine automatic stop / restart vehicle (eco-run vehicle) that can automatically stop the engine when a predetermined driving condition is satisfied, and is provided with an oil pump control device for the automatic transmission. This control device is provided with a stopped state determination means that predicts whether the vehicle stop and engine stop states will continue for a long period of time, and a technology is proposed in which, when the stopped state determination means predicts that the stopped state will continue for a long period of time, the operation of the electric oil pump is stopped.

[0009] According to this, when it is fully predicted that the vehicle and engine stopped states will continue for a long period of time, control is performed to stop operation of the electric oil pump without compromising the time lag at restart, thereby improving the durable life of the motor that drives the electric oil pump and improving fuel efficiency by reducing power consumption during eco-driving.

[0010] Patent document 2 also proposes a vehicle control device that is equipped with a drive unit that can select between a driving position and a non-driving position, and has an engagement device that transmits driving force or an engagement device that sets a gear ratio, and an oil pump that is driven by an electric motor and supplies hydraulic pressure for engaging the engagement device, and that can reduce the drive of the oil pump by the electric motor when there is a request to stop the vehicle.

[0011] Specifically, this vehicle control device includes a stop request determination means for determining whether a request to stop the vehicle has occurred, and a delay means for reducing the drive of the oil pump by the electric motor after a predetermined time has elapsed during which it can be determined that the request to stop the vehicle is an intention to stop the vehicle continuously, if a request to stop the vehicle has occurred. This makes it possible to match the state of the electric oil pump with the intention of the driver and road conditions as much as possible. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2002-372139 A [Patent Document 2] Patent No. 4055297 Summary of the Invention [Problem to be solved by the invention]

[0013] The technologies of Patent Documents 1 and 2 are equipped with an electric oil pump for supplying hydraulic pressure to an automatic transmission and an electric oil pump for supplying hydraulic pressure for engaging an engagement device, and control the electric pump in relation to stopping the vehicle, but both are vehicles driven only by the engine. Therefore, in a hybrid vehicle, there is no premise that a traction motor is disposed between the engine and the transmission, and there is no premise that the engine and the traction motor are separated when traveling in EV mode.

[0014] Furthermore, Patent Documents 1 and 2 do not take into account the unique configuration in which a torque converter equipped with a lock-up clutch is disposed between the engine and the transmission (connected to the axle), and therefore cannot address the issue of conserving power from the onboard battery when driving in EV mode (when the engine is stopped) in a hybrid vehicle with this unique configuration.

[0015] The present invention has been made in consideration of the above problems, and its object is to provide a power saving method for a hybrid vehicle that can achieve both improved fuel efficiency by saving power from the on-board battery when the hybrid vehicle is in EV mode and high responsiveness when the engine is restarted. [Means for solving the problem]

[0016] In order to achieve the above object, a power saving method for a hybrid vehicle according to one embodiment of the present invention comprises the steps of: Equipped with an engine and a driving motor as a drive source, a torque converter and an engine disconnect clutch are disposed between the engine and the drive motor from the engine side in a power transmission path from the engine to the drive wheels, and a transmission is disposed between the drive motor and the drive wheels, A power saving method for a hybrid vehicle, comprising: an electric oil pump driven by an auxiliary battery and a mechanical oil pump driven by engine power, for supplying hydraulic pressure to a lock-up clutch provided in the torque converter, and when an electric vehicle mode in which the engine is stopped is selected, hydraulic pressure is supplied from the electric oil pump, When an electric vehicle mode is selected in which the engine is stopped, When the parking range is selected and the foot brake is in the OFF state, if it is determined that the driver has no intention of starting in a short time, the power supply from the auxiliary battery to the electric oil pump is cut off and the lock-up clutch is turned OFF. Effect of the Invention

[0017] According to the present invention, in a hybrid vehicle having a torque converter (equipped with a lock-up clutch) disposed between an engine and a transmission connected to an axle, power saving of the on-board battery can be achieved when the EV mode is selected. That is, while ensuring a quick response when restarting the engine, power saving of the on-board battery (auxiliary battery) for operating the lock-up clutch of the torque converter can be achieved. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing the configuration of a power transmission system of a hybrid vehicle in which a method of the present invention is implemented; [Diagram 2] 2 is a flowchart showing a processing procedure of the method of the present invention. [Diagram 3] FIG. 2 is a diagram showing ON / OFF states of various elements (engine, engine disconnect clutch, driving motor, electric oil pump, and mechanical oil pump) when the hybrid vehicle is stopped in EV mode P range. [Figure 4]FIG. 2 is a diagram showing ON / OFF states of various elements (engine, engine disconnect clutch, driving motor, electric oil pump, and mechanical oil pump) when the hybrid vehicle is stopped in EV mode D range. [Diagram 5] FIG. 2 is a diagram showing ON / OFF states of various elements (engine, engine disconnect clutch, driving motor, electric oil pump, and mechanical oil pump) when the engine of a hybrid vehicle is restarted in an EV mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] [Configuration of the power transmission system of the hybrid vehicle to which the present invention is applied] First, the configuration of a power transmission system of a hybrid vehicle to which the method of the present invention is applied will be described below with reference to FIG.

[0021] 1 is a block diagram showing the overall configuration 10 of a power transmission system of a hybrid vehicle in which the method of the present invention is implemented, and includes an engine 12 and a traction motor 14 as drive sources. A torque converter 16 and an engine disconnect clutch 18 are arranged in this order from the engine 12 side in the power transmission path between the engine 12 and the traction motor 14. A transmission 20 is arranged in the power transmission path between the traction motor 14 and the drive wheels W, and the transmission 20 is connected to the drive wheels W side.

[0022] Furthermore, the torque converter 16 is provided with a lock-up clutch (LC) 16a for directly connecting the input and output shafts to ensure high power transmission efficiency in the region where the torque amplification function is not required as described above.

[0023] Here, the torque converter 16 is connected to an electric oil pump 24 connected to the auxiliary battery 22 and a mechanical oil pump 26 driven by part of the power of the engine 12, and the lock-up clutch 16a is switched between ON (engaged) and OFF (disengaged) by the oil pressure supplied from the EPO 24 or MPO 26.

[0024] In addition, the engine disconnection clutch 18 disconnects the engine 12 and the traction motor 14 when the hybrid vehicle is running in EV mode, that is, when the vehicle is running only on the power of the traction motor 14 with the engine 12 stopped, and is engaged and disengaged by hydraulic pressure supplied from an electric oil pump 24 or a mechanical oil pump 26.

[0025] The traction motor 14 generates the power required for the hybrid vehicle to run, and is driven by electric power supplied from a high-voltage battery 28 via an inverter 30. A lithium-ion battery or the like is used for the high-voltage battery 28, and direct current from the high-voltage battery 28 is converted to alternating current by the inverter 10 and supplied to the traction motor 14.

[0026] The transmission 20 changes the rotation input from the output shaft of the drive motor 14 at a predetermined gear ratio according to the driving state of the hybrid vehicle. A continuously variable transmission (CVT) capable of continuously changing the gear ratio is widely used for this transmission 5. This continuously variable transmission is configured by wrapping an endless metal belt or chain between a drive pulley on the driving side and a driven pulley on the driven side, and by adjusting the axial thrust acting on the drive pulley and the driven pulley by hydraulic pressure, the winding diameter of the metal belt or the like around these drive pulley and driven pulley is changed to continuously change the gear ratio. Here, hydraulic pressure is supplied to the drive pulley and the driven pulley by an electric oil pump 24 or a mechanical oil pump 26. The transmission 20 may be a stepped type in which the gear ratio is changed in stages by changing the meshing of multiple transmission gears. Even in this stepped transmission 20, the gears are switched by hydraulic pressure supplied from the electric oil pump 24 or the mechanical oil pump 26.

[0027] A power saving method according to an embodiment of the present invention will be described in detail below.

[0028] First, when the EV mode is selected, the vehicle is stopped, the parking range is selected, and the brake is OFF (the driver is not stepping on the brake pedal), which is the basic condition for determining that the driver does not intend to start immediately. If this is not met, that is, if it is determined that the parking range is not selected or the brake is ON (the brake pedal is being stepped on), the control according to the present invention is not performed and power is supplied to the EOP 24 from the auxiliary battery 22 as usual. That is, the lock-up clutch 16a of the torque converter 16 is turned ON by the power of the auxiliary battery 22.

[0029] Next, when the basic conditions that the parking range is selected and the brake is in the OFF state are satisfied, in this embodiment, the following six judgments are made to determine that the driver has no intention of starting immediately. Hazard lights on or not? Is the blinker on or not? 3) Is the door open? 4) Is the handbrake on or not? 5) Is the navigation system in operation? 6)Audio operation in progress or not?

[0030] In the method of the present invention, the above six requirements 1) to 6) are OR conditions, and if any one of them is satisfied, it is determined that the driver does not intend to immediately start the vehicle, and the power supply from the auxiliary battery 22 to the electric oil pump 24 is cut off to stop the supply of oil, and the lock-up clutch 16a of the torque converter 16 is turned off. In other words, if the driver does not intend to start the vehicle (if there is no possibility of the engine 1 being restarted immediately), there is no need to consider the responsiveness of the engine 1 at the time of restart, so the power supply to the electric oil pump 24 is cut off and the lock-up clutch 16a of the torque converter 16 is turned off. Note that when the hybrid vehicle is stopped in the EV mode and the parking range is selected, the engine 1 is stopped, and therefore the lock-up clutch 16a cannot be operated by the mechanical oil pump 26.

[0031] On the other hand, if all of the six requirements 1) to 6) above are not met, it is determined that the driver intends to start the vehicle, and the lock-up clutch 16a is kept ON by the power of the auxiliary battery 22. This improves the responsiveness to the immediate restart of the engine 12.

[0032] Next, the above control procedure will be described with reference to the flowchart shown in Fig. 2. The drive control of the electric oil pump 24 and the mechanical oil pump 26 is performed by an ECU (Electronic Control Unit) (not shown).

[0033] When the hybrid vehicle is stopped in EV mode, it is first determined whether the shift range is in the P (parking) range and the brake is OFF (step S1 in FIG. 2). When the hybrid vehicle is stopped in EV mode, as shown in FIG. 3, the engine 1 is OFF (stopped), the engine disconnect clutch 4 is OFF (disconnected), the driving motor 2 is OFF (stopped), and the mechanical oil pump 26 is OFF (stopped).

[0034] In this embodiment, if the shift range is in the P (parking) range and the brake is OFF (step S1: Yes), it is determined whether the hazard lamps are on (step S2), and if the hazard lamps are not on (step S2: No), it is determined whether the turn signal is on (step S3). If the turn signal is not on (step S3: No), it is determined whether the door is open (step S4), and if the door is not open (step S4: No), it is determined whether the parking brake is ON (step S5).

[0035] In the above judgment, if the handbrake is not ON (step S5: No), it is judged whether or not the driver is operating the navigation (step S6), and if the driver is not operating the navigation (step S6: No), it is judged whether or not the driver is operating the audio (step S7).

[0036] Here, "in operation" does not mean that the navigation or audio is ON, but rather that a switch or the like is actually being operated to adjust the navigation or audio.

[0037] In the judgments in steps S2 to S7 above, that is, when the hybrid vehicle is stopped in EV mode and the brake is in the OFF state (step S1: Yes), if at least one of the six requirements 1) to 6) above is satisfied and at least one of the judgments in steps S2 to S7 is Yes, it is determined that the driver has no intention of starting, power supply to electric oil pump 24 is cut off (step S8), and because no hydraulic pressure is supplied from electric oil pump 24 to lock-up clutch 16a of torque converter 16, lock-up clutch 16a of torque converter 16 is turned OFF (disconnected) (see FIG. 3), and the series of controls ends (step S10).

[0038] In addition, the judgment may be made in combination. For example, conditions such as door open? (step S4), handbrake on? (step S5), navigation operation in progress? (step S6), etc. may be combined. For example, by using the AND conditions of turn signal on? (step S3) and door open? (step S4), When the turn signal is on and the door is open, the power supply to the electric oil pump 24 is cut off, thereby making it possible to increase the reliability of the determination.

[0039] As described above, according to the power saving method of the present invention, when the hybrid vehicle is stopped in EV mode and the brake is OFF, if it is determined that the driver has no intention of starting, that is, if there is no need to consider the responsiveness of the engine 12 when restarting, the power supply to the electric oil pump 24 is cut off and the lock-up clutch 16a of the torque converter 16 is turned OFF (disconnected), thereby realizing power saving and improving fuel efficiency.

[0040] On the other hand, if all of the six requirements are not met and the determinations in steps S2 to S7 are all No, or if the hybrid vehicle is in EV mode and the brake is not OFF (step S1: No), it is determined that the driver intends to start, and power is supplied to the electric oil pump 24 to drive the electric oil pump 24 (step S9), and the series of controls ends (step S10). In this way, when the electric oil pump 24 is driven (see FIG. 3), the lock-up clutch 16a of the torque converter 16 is turned ON (engaged) by the hydraulic pressure supplied from the electric oil pump 24, and the engine 12 and the torque converter 16 are directly connected, thereby improving the responsiveness when the engine 12 is restarted.

[0041] In this embodiment, six conditions are listed as conditions for determining that the driver does not intend to start, namely, hazard lamps are on, blinkers are on, doors are open, the handbrake is on, navigation is being operated, and audio is being operated, but other conditions may be added to these conditions. Also, in this embodiment, when at least one of the six conditions for determining that the driver does not intend to start is satisfied, it is determined that the driver does not intend to start and power supply to the electric oil pump 24 is cut off, but power supply to the electric oil pump 24 may be cut off after a predetermined time has elapsed since at least one of the six conditions is satisfied.

[0042] As is clear from the above explanation, the power saving method of the present invention has the effect of improving fuel efficiency through power saving and ensuring high responsiveness when the engine is restarted when the hybrid vehicle is stopped in EV mode and the shift range is set to the parking range (P range).

[0043] [Reference example 1] Next, as a reference example 1, FIG. 4 shows the ON / OFF states of various elements (engine 12, engine disconnect clutch 18, driving motor 14, electric oil pump 24, mechanical oil pump 26) when the hybrid vehicle is stopped in EV mode D range.

[0044] When the hybrid vehicle is stopped with the driving mode set to EV mode and the shift range set to D (drive) range, the engine 12 is OFF (stopped), the engine disconnect clutch 18 is OFF (disconnected), and the driving motor 14 is OFF (stopped), as shown in Fig. 4. At this time, since the engine 12 is OFF (stopped), the mechanical oil pump 26 is also OFF (stopped), but the electric oil pump 24 is ON (driven), and the lock-up clutch 16a of the torque converter 16 is turned ON (engaged) by the hydraulic pressure supplied from the electric oil pump 24, thereby improving the responsiveness when the engine is restarted.

[0045] [Reference example 2] Next, as a second reference example, FIG. 5 shows the ON / OFF states of each element (engine 12, engine disconnect clutch 18, traction motor 14, electric oil pump 24, mechanical oil pump 26) when the engine is restarted in the EV mode of a hybrid vehicle.

[0046] When the engine 12 is restarted with the hybrid vehicle's driving mode set to the EV mode, as shown in Fig. 5, the engine disconnect clutch 18 is turned ON (engaged) to connect the engine 12 and the traction motor 14, and the traction motor 14 is turned ON (driven). The electric oil pump 24 is turned ON (driven) by power supplied from the auxiliary battery 22. At this time, the engine 12 has not yet started, so the mechanical oil pump 26 is OFF (stopped), but the electric oil pump 24 is turned ON (driven) as described above, and the lock-up clutch 16 of the torque converter 16 is turned ON (engaged).

[0047] In the above state, when the traveling motor 14 is turned on (driven), a part of the power is transmitted to the engine 12 via the engine disconnect clutch 18 and the lock-up clutch 16a of the torque converter 16, and is used to restart the engine 12. In other words, the traveling motor 14 functions as a starter motor that starts the engine 12.

[0048] Then, when the engine 12 is restarted, the power of the engine 12 and the power of the traction motor 14 are transmitted to the transmission 20, the speed ratio of the rotations input to the transmission 20 is set to an appropriate value corresponding to the driving conditions of the hybrid vehicle, and the rotation changed by the transmission 20 is transmitted to the drive wheels W, which are driven to rotate at a predetermined rotational speed, so that the hybrid vehicle runs at a predetermined speed.

[0049] It should be noted that the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0050] 10 Overall configuration of hybrid vehicle power transmission system 12 Engine 14. Driving motor 16 Torque converter 16a Lock-up clutch 18 Engine disconnect clutch 20 Transmission 22 Auxiliary battery 24 Electric Oil Pump (EOP) 26 Mechanical Oil Pump (MOP) 28 High Voltage Battery 30 Inverter W Drive wheel

Claims

1. Equipped with an engine and a driving motor as a drive source, a torque converter and an engine disconnect clutch are disposed between the engine and the drive motor from the engine side in a power transmission path from the engine to the drive wheels, and a transmission is disposed between the drive motor and the drive wheels, A power saving method for a hybrid vehicle, comprising: an electric oil pump driven by an auxiliary battery and a mechanical oil pump driven by engine power, for supplying hydraulic pressure to a lock-up clutch provided in the torque converter, and when an electric vehicle mode in which the engine is stopped is selected, hydraulic pressure is supplied from the electric oil pump, When an electric vehicle mode is selected in which the engine is stopped, A power saving method for a hybrid vehicle, characterized in that when the parking range is selected and the foot brake is in the OFF state, if it is determined that the driver has no intention of starting within a short period of time, the power supply from the auxiliary battery to the electric oil pump is cut off and the lock-up clutch is turned OFF.

2. The judgement of whether the driver intends to leave the vehicle within a short period of time is as follows:

2. The power saving method for a hybrid vehicle according to claim 1, further comprising determining that the driver has no intention of starting the vehicle when at least one of the following conditions is satisfied: hazard lights are on, turn signals are on, a door is open, the handbrake is on, a navigation system is being operated, or an audio system is being operated.

3. The judgement of whether the driver intends to leave the vehicle within a short period of time is as follows:

3. The power saving method for a hybrid vehicle according to claim 2, further comprising the step of determining that the driver has no intention of starting the vehicle when any combination of the following requirements is met: hazard lights are on, turn signals are on, a door is open, the handbrake is on, navigation is being operated, and audio is being operated.

4. 3. The power saving method for a hybrid vehicle according to claim 2, further comprising the step of cutting off power supply to the electric oil pump and turning off the lock-up clutch after a predetermined time has elapsed since at least one of the following conditions is satisfied: hazard lights are on, turn signals are on, a door is open, the parking brake is on, a navigation system is being operated, or an audio system is being operated.

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