Control device for hybrid vehicle

Abstract

The present invention addresses the problem of improving both trafficability on so-called severe roads and drivability when traveling at a high gear ratio. A controller for a hybrid vehicle control device according to the present invention is provided with: a gear ratio determination unit (step S1) that determines that a gear ratio set by a transmission is limited to a prescribed low gear ratio; a mode determination unit (step S2) that determines that the second mode has been selected; and an intermittent operation control unit (steps S3, S4) that permits intermittent operation when the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the prescribed low gear ratio and the mode determination unit determines that the second mode has been selected. When the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the predetermined low gear ratio and the mode determination unit does not determine that the second mode has been selected, the intermittent operation is prohibited.

Description

Technical Field

[0001] This invention relates to a control device for a hybrid vehicle equipped with an engine and a motor as driving power sources, and more particularly to a device for controlling the driving force of a hybrid vehicle that can simultaneously transmit the driving force output by the engine and the driving force output by the motor to the drive wheels for driving. Background Technology

[0002] As a form of hybrid vehicle, parallel hybrid and series-parallel hybrid are known. In such hybrid vehicles, driving can be achieved by the engine (temporarily referred to as engine driving), driving by the motor (temporarily referred to as motor driving), or driving by both the engine and the motor (temporarily referred to as hybrid driving). Therefore, by selecting these driving modes (or drive modes) according to the conditions of the road, acceleration, quietness, or ability to handle rough roads can be improved.

[0003] Patent Document 1 describes a control device that includes a mechanism that, when the engine and motor are driven to meet driving requirements, increases the motor output to a level sufficient for the vehicle to travel using only the motor when a high passability is specified. According to the vehicle control device described in Patent Document 1, when traveling on unpaved roads, the motor output can be increased by specifying the passability, thereby increasing the chance of driving with the engine off.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-125068 Summary of the Invention

[0005] The ratio of driving force borne by the engine and motor during hybrid driving is typically determined based on driving demand, such as throttle opening, or the remaining charge (SOC) in the charging device. The control device described in Patent Document 1 adds a specified passability as a control condition to this typical control, increasing the proportion of driving force borne by the motor during hybrid driving when the passability is specified. In typical hybrid driving control, the engine is driven along with the motor because a larger driving force can be obtained by driving the engine. Therefore, in the control device described in Patent Document 1, even if the proportion of driving force borne by the motor is increased, the engine may still start. Thus, while maintaining a large gear ratio to obtain a larger driving force, the change in output torque of the driving force source accompanying the engine restart manifests as a large change in driving force at the wheels due to the large gear ratio. As a result, a large change in driving force or a shock accompanying engine startup may occur, thereby deteriorating the vehicle's ride comfort or driving performance. Furthermore, since there is an unavoidable delay in the increase of output torque when the engine is started, temporary insufficient driving force or delay in the increase of driving force may become the cause of deterioration in driving performance.

[0006] The present invention was made in view of the above-mentioned technical problems, and its purpose is to provide a control device for a hybrid vehicle that can improve the passability of so-called bad roads and improve driving performance while maintaining a large gear ratio.

[0007] To achieve the above objectives, the present invention provides a control device for a hybrid vehicle, the hybrid vehicle having an engine and a motor as driving power sources, a transmission connected to the output side of the driving power sources, and in hybrid driving mode, using torque output from the engine and torque output from the motor, the engine intermittently operates when predetermined conditions are met, and can select a first mode for controlling the driving force for driving and a second mode for limiting the driving force according to driving states including vehicle speed or required driving force. The control device for the hybrid vehicle is characterized by having a controller for controlling the operation of the engine. The controller includes: a gear ratio determination unit that determines that the gear ratio set by the transmission is limited to a predetermined low-speed gear ratio; a mode determination unit that determines that the second mode is selected; and an intermittent operation control unit that allows intermittent operation when the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the predetermined low-speed gear ratio and the mode determination unit determines that the second mode is selected, and prohibits intermittent operation when the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the predetermined low-speed gear ratio and the mode determination unit does not determine that the second mode is selected.

[0008] In the second mode of the present invention, the driving force can be limited by either a speed limit that limits the vehicle speed to below a predetermined speed or a differential limit that limits the differential rotation of the left and right wheels or the front and rear wheels.

[0009] Invention Effects

[0010] According to the present invention, when the gear ratio is limited to a predetermined low gear ratio and the second mode is selected to limit the driving force, intermittent engine operation is permitted. The driving force limitation based on the second mode includes limiting the driving force when the vehicle speed is below a predetermined speed, or limiting the differential rotation of the left and right or front and rear wheels, etc. Furthermore, intermittent operation involves stopping the engine and controlling driving via a motor when predetermined conditions are met. Therefore, when driving while maintaining a low gear ratio and limiting vehicle speed or differential wheel rotation, driving is performed by the motor even when the engine is stopped. As a result, even if the driving force is stable or changes, the changes are smooth, thus improving driving performance. On the other hand, even when the low gear ratio is limited, intermittent engine operation is prohibited and engine operation continues even when the second mode is not selected, thus preventing engine starting or accompanying changes or shocks in driving force, resulting in improved driving performance. Attached Figure Description

[0011] Figure 1This is a schematic diagram illustrating the drive system in an embodiment of the present invention.

[0012] Figure 2 This is a skeleton diagram representing an example of the hybrid drive mechanism.

[0013] Figure 3 This is a block diagram representing the functional structure of the controller.

[0014] Figure 4 This is a flowchart used to illustrate an example of control performed by a controller. Detailed Implementation

[0015] Next, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the embodiments described below are merely examples of implementing the present invention and do not limit the scope of the invention.

[0016] The vehicle in this embodiment of the invention is a hybrid vehicle equipped with an engine (internal combustion engine) and a motor (electric motor or motor with power generation function) as driving power sources, capable of transmitting the torque output by the engine and the torque output by the motor to the drive wheels. Figure 1 The drive system of the hybrid vehicle 1 is schematically shown in the diagram. The drive power source 2 includes an engine 3 (such as a gasoline engine) and a motor 4, enabling driving based on the engine 3 (engine driving), driving based on the motor 4 (EV driving), and driving based on both the engine 3 and the motor 4 (hybrid driving). The hybrid drive mechanism capable of this driving is illustrated in a skeletal diagram. Figure 2 .

[0017] Figure 2 The symbol "5" in the diagram represents a planetary gear mechanism constituting the power distribution mechanism. This is a differential mechanism in which the sun gear 6, ring gear 7, and a gear carrier 9 that maintains the pinion 8 meshing with the sun gear 6 and ring gear 7 are rotating elements. An engine 3 is connected to the gear carrier 9, and a first motor 10 is connected to the sun gear 6. The ring gear 7 serves as the output element, and an output component 11 is connected to the ring gear 7. Furthermore, a second motor 12 is connected to the output component 11. These first motors 10 and second motors 12 constitute motor 4. Additionally, the connection between the ring gear 7 and the gear carrier 9 is configured, and a clutch or similar mechanism is provided between the ring gear 7 and the output component 11. Selectively connecting specific components or providing a mechanism to stop rotation is arbitrary.

[0018] The power output from engine 3 is divided into a sun gear 6 and a ring gear 7 via planetary gear mechanism 5, with a portion of the power output to output component 11 via ring gear 7. Conversely, to control engine speed, torque is input from first motor 10 to sun gear 6. Under stable hybrid driving conditions, first motor 10 functions as a generator, inputting a reaction torque to sun gear 6. As a result, the torque of ring gear 7 becomes greater than the torque output from engine 3. The electricity generated by the reaction torque applied to sun gear 6 by first motor 10 is sent to second motor 12, which functions as a motor, outputting its torque from output component 11. Additionally, first motor 10 and second motor 12 can also be driven by electricity from an energy storage device (not shown).

[0019] A transmission 13 is connected to the output side of the drive power source 2. As an example, the transmission 13 is a gear transmission configured to allow setting multiple gear ratios for forward driving, reverse driving, and neutral (no torque output). Furthermore, the gear ratio switching, i.e., the shifting of gears, is configured to be electrically controlled and executed. A transfer case 14 is connected to the transmission 13. The transfer case 14 is a mechanism that divides the torque output from the transmission 13 and transmits it to the rear wheel 15 and the front wheel 16. For example, it can be configured as a differential mechanism including three rotating elements. The differential mechanism is, for example, a mechanism in which a pinion composed of bevel gears meshes between a pair of side gears composed of bevel gears, causing it to revolve and rotate, or a planetary gear mechanism. Furthermore, a differential limiting clutch (not shown) is provided to limit or prohibit its differential action.

[0020] A rear wheel output shaft 17 and a front wheel output shaft 18 are provided on the transfer case 14. The rear wheel output shaft 17 is connected to a rear differential (hereinafter referred to as rear differential 19), which serves as a final reduction gear, and the left and right rear wheels 15 are connected to the rear differential 19. In addition, the rear differential 19 is equipped with a differential limiting clutch (not shown) that restricts or prohibits differential rotation of the left and right rear wheels 15.

[0021] Furthermore, the front wheel output shaft 18 is connected to the front differential (hereinafter referred to as the front differential) 21, which serves as a final reduction gear, via a 2-4 switching clutch 20. The left and right front wheels 16 are connected to the front differential 21. Similar to the rear differential 19 described above, the front differential 21 has a differential limiting clutch (not shown) that restricts or prohibits the differential rotation of the left and right front wheels 16.

[0022] The 2-4 switching clutch 20 is a clutch that selectively disengages torque transmission via the front differential 21 or the front wheels 16 through the front wheel output shaft 18. Engaging the 2-4 switching clutch 20 enables four-wheel drive, and conversely, disengaging it enables two-wheel drive. Furthermore, in two-wheel drive mode, the differential limiting clutch in the transfer case 14 is engaged to ensure torque output to the rear wheel output shaft 17. The 2-4 switching clutch 20 can be integrated into the transfer case 14.

[0023] The transmission 13 is a conventionally known automatic transmission, equipped with a shifting device 22 for switching the gear ratios based on the transmission 13. The shifting device 22 is configured to allow selection of positions via a shift lever, including Park (P), Reverse (R), Neutral (N), and Drive (D). Figure 1 The hybrid vehicle 1 shown, equipped with a transmission 13, a transfer case 14, and final drive units 19 and 21 with differential limiting clutches, can switch between two-wheel drive, four-wheel drive, or a state with limited driving force, and is provided with a switch 23 to select these driving states. The driving states that can be selected by the switch 23 are two-wheel drive state H2 without limited driving force, four-wheel drive state H4 without limited driving force, and four-wheel drive state L4 with limited upshifts and more use of a specified low gear ratio.

[0024] Furthermore, the hybrid vehicle 1 is equipped with a Multi Terrain Select (MTS) system that sets the driving state to suit the road conditions. Selectable road conditions include, for example, "SAND" for sandy roads, "MUD" for muddy roads, and "ROCK" for rocky roads. An MTS switch 24 is provided for manually selecting these driving states. In driving states suitable for the road conditions listed here, differential limiting is performed to maintain four-wheel drive, or driving force limiting is implemented to keep the vehicle speed below a predetermined speed. This control can be performed using conventionally known power control computers, braking computers, four-wheel drive computers, etc. Therefore, the "driving force limiting" in this embodiment of the invention includes control of the hybrid vehicle 1's driving state, such as limiting the gear ratio set by the transmission 13 to a predetermined high gear ratio (i.e., low gear ratio) and limiting the output torque of the power source 2 to keep the vehicle speed below a predetermined speed, or control of limiting the differential rotation of the four front and rear wheels.

[0025] in addition, Figure 1 The hybrid vehicle 1 shown has operating equipment typically found in vehicles, such as a steering wheel 25, an accelerator pedal 26, and a brake pedal (not shown).

[0026] In the hybrid vehicle 1 operating in hybrid mode, with the engine 3 and motor 4 driving in a hybrid manner, the engine 3 is stopped and motor operation is initiated when the remaining charge (SOC) in the battery (not shown) connected to the motor 4 is sufficiently high and the throttle opening is small, allowing the motor 4 to meet the driving requirements. Furthermore, the engine 3 is restarted when the required driving force increases by pressing the accelerator pedal 26 or when the SOC of the battery decreases. This control that stops the operation of the engine 3 during driving is called intermittent operation. The intermittent operation of the engine 3 during hybrid driving is essentially as described above, conditioned on the condition that the motor 4 can meet the driving requirements. In the control device of this embodiment of the invention, in addition to this condition, intermittent operation is also performed conditioned on the limitation of driving force or driving state.

[0027] A controller 27 is provided to control the intermittent operation. The controller 27 is an electronic control device primarily composed of a microcomputer consisting of a processing unit (CPU), storage units (RAM, ROM), and interfaces. It is configured to perform calculations according to a predetermined program using input data or pre-stored data, and output the result of the calculation as a control command signal. The input data includes signals indicating the drive state selected by the aforementioned switch 23, road surface conditions selected by the MTS switch 24, etc. Based on this input data, the controller 27 outputs command signals indicating whether intermittent operation is permitted or prohibited.

[0028] The functional structure of the controller 27 used for this control is illustrated in the block diagram. Figure 3 The controller 27 includes a gear ratio determination unit 27a. The gear ratio determination unit 27a determines that the gear ratio set by the aforementioned transmission 13 is limited to a predetermined high gear ratio (low gear ratio). This determination can be made based on the drive state selected by the switch 23. For example, if a four-wheel drive state L4, which restricts upshifting and uses a predetermined low gear ratio, is selected, the determination that the gear ratio is limited to a low gear ratio is established.

[0029] Furthermore, the controller 27 includes a mode determination unit 27b. Here, the mode is a drive state suitable for the road surface condition selected by the MTS switch 24. When any of the aforementioned "SAND", "MUD", or "ROCK" is selected, the mode determination unit 27b determines that the second mode has been selected. In particular, in the embodiment described here, the mode determination unit 27b determines that the second mode has been selected when "ROCK" is selected. Additionally, when the MTS switch 24 is not operated and no drive state is selected, especially when "ROCK" is not selected, it corresponds to the first mode in this embodiment of the invention.

[0030] Furthermore, the controller 27 includes an intermittent operation control unit 27c. The intermittent operation control unit 27c is a control unit that prohibits and allows the intermittent operation of the engine 3. When the gear ratio is limited to a low gear ratio and "ROCK" is selected as the drive state, intermittent operation (stopping the engine 3) is allowed. In other drive states, intermittent operation is prohibited.

[0031] An example of the control based on controller 27 is illustrated in the flowchart below. Figure 4 . Figure 4 The routine shown is repeatedly executed by the controller 27 while the hybrid vehicle 1 is in operation. First, in step S1, it is determined whether the L4 gear position has been selected. This determination is made based on the signal output by selecting the specified drive state via the aforementioned switch 23.

[0032] If the result of the determination in step S1 is "yes", then in step S2, it is determined whether "ROCK" has been selected by the MTS switch 24. This determination can be made based on the signal output by selecting the specified drive state (mode) by the aforementioned MTS switch 24.

[0033] If the result of step S2 is "yes", then proceed to step S3, make an intermittent permission request, and return. That is, if the result of step S2 is "yes", the gear ratio is limited to a specified low gear ratio or below, the vehicle speed is below a specified vehicle speed, and it is a driving or traveling state with differential limitation of the four front and rear wheels. Therefore, an instruction signal is output to allow intermittent operation of the engine 3. Thus, in this case, the drive motor 4 (especially the second motor 12) is driven, but since the gear ratio is limited to a specified large gear ratio, a sufficiently large driving force can be output. Furthermore, the torque output by the motor 4 (second motor 12) is a smooth torque that varies according to the current, so even when driving on rough roads such as rocky roads, a linearly varying driving force can be obtained, thereby improving driving performance. Moreover, since there is almost no abrupt change in driving force, stable operation can be achieved.

[0034] Conversely, if the result of step S2 is "no", then proceed to step S4 to request intermittent prohibition and return. That is, output an intermittent operation prohibition command signal to prevent stopping engine 3 and continue engine 3 operation. Therefore, there will be no situation where engine 3 restarts after stopping, thus avoiding the change or impact of driving force accompanying the restart of engine 3, thereby improving driving performance.

[0035] Furthermore, if the result of the determination in step S1 is "no", then in step S5, an intermittent permission request is made. That is, an intermittent permission command signal is output, and then the process returns. This control is the typical control method used in hybrid vehicles.

[0036] The present invention has been described above as an embodiment of the invention, but the invention is not limited to the structure of the above embodiment. The powertrain, hybrid drive mechanism, and transmission can be any suitable structure known in the past. Therefore, the hybrid vehicle can be a four-wheel drive vehicle based on front-wheel drive, rather than a four-wheel drive vehicle based on rear-wheel drive. Furthermore, the device for switching the drive state can be a lever type, rather than the aforementioned switch.

[0037] Symbol Explanation

[0038] 1-Hybrid vehicle, 2-Drive power source, 3-Engine, 4-Motor, 5-Planetary gear mechanism, 6-Sun gear, 7-Ring gear, 8-Pin gear, 9-Wheel carrier, 10-First motor, 11-Output component, 12-Second motor, 13-Transmission, 14-Transfer transfer case, 15-Rear wheel, 16-Front wheel, 17-Rear wheel output shaft, 18-Front wheel output shaft, 19-Rear differential, 20-Switching clutch, 21-Front differential, 22-Shifting device, 23-Switching switch, 24-MTS switch, 25-Steering wheel, 26-Accelerator pedal, 27-Controller, 27a-Gear ratio determination unit, 27b-Mode determination unit, 27c-Intermittent operation control unit.

Claims

1. A control device for a hybrid vehicle, the hybrid vehicle having an engine and a motor as driving power sources, a transmission connected to the output side of the driving power sources, wherein during hybrid driving using torque output from the engine and torque output from the motor, the engine is intermittently operated when predetermined conditions are met, and the control device is capable of selecting a first mode for controlling the driving force for driving and a second mode for limiting the driving force based on a driving state including vehicle speed or required driving force, the control device for the hybrid vehicle being characterized by having: A controller that controls the operation of the engine. The controller has: The gear ratio determination unit determines that the gear ratio set by the transmission is limited to a specified low-speed gear ratio; The mode determination unit selects the second mode; and The intermittent operation control unit allows intermittent operation when the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the predetermined low-speed gear ratio and the mode determination unit determines that the second mode has been selected; and prohibits intermittent operation when the gear ratio determination unit determines that the gear ratio set by the transmission is limited to the predetermined low-speed gear ratio and the mode determination unit does not determine that the second mode has been selected.

2. The control device for a hybrid vehicle according to claim 1, characterized in that, In the second mode, the driving force is limited by either a speed limit that restricts the vehicle speed to below a predetermined speed or a differential limit that restricts the differential rotation of the left and right wheels or the front and rear wheels.

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