Control system for hybrid vehicles

Abstract

This system aims to achieve both improved off-road capability and enhanced drivability when maintaining a large gear ratio. [Solution] The controller includes a gear ratio determination unit (step S1) that determines whether the gear ratio set in the transmission is limited to a predetermined low gear ratio, a mode determination unit (step S2) that determines whether the second mode is 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 in the transmission is limited to a predetermined low 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 in the transmission is limited to a predetermined low gear ratio and the mode determination unit does not determine that the second mode is selected.

Description

Technical Field

[0001] The present invention relates to a control device for a hybrid vehicle having an engine and a motor as driving power sources, and more particularly to a device for controlling the driving power of a hybrid vehicle capable of transmitting both the driving power output from the engine and the driving power output from the motor to drive wheels for running.

Background Art

[0002] As hybrid forms of vehicles, parallel hybrids and series-parallel hybrids are known. In this type of hybrid vehicle, running by the driving power of the engine (temporarily referred to as engine running), running by the driving power of the motor (temporarily referred to as motor running), and running by the driving powers of both the engine and the motor (temporarily referred to as hybrid running) are possible. Therefore, by selecting these running modes (or driving modes) according to the state of the road surface, acceleration performance, quietness, or rough-road running performance can be improved.

[0003] Patent Document 1 describes a control device provided with means for increasing the output of the motor to such an extent that it can run only by the motor when a high running ability is specified in a situation where the engine and the motor are driven to satisfy a driving request. According to the vehicle control device described in this Patent Document 1, when running on an unpaved road surface or the like, since the running performance is specified, the output of the motor is increased, so that the opportunity to stop the engine and run can be increased.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The proportion of driving force borne by the engine and motor during hybrid driving is generally determined based on factors such as the driving demand amount, which is expressed as the accelerator opening, and the remaining charge (SOC) in the charging device. The control device described in Patent Document 1 adds the specification of off-road capability as a control condition to these general control conditions, and when off-road capability is specified, it increases the proportion of driving force borne by the motor during hybrid driving. In general control of hybrid driving, the engine is driven together with the motor because a large driving force can be obtained by driving the engine. Therefore, even if the control device described in Patent Document 1 increases the proportion of driving force borne by the motor, the engine may be started, and in a state where a large gear ratio is maintained in order to obtain a large driving force, the change in output torque at the driving force source due to the engine restart will appear as a large change in driving force at the wheels due to the large gear ratio, and as a result, a large change in driving force and shock due to engine starting may occur, which may worsen the ride comfort or drivability of the vehicle. Furthermore, there is an unavoidable delay in the increase in output torque when the engine is started, so a temporary shortage of driving force or a delay in the increase of driving force may be factors that worsen drivability.

[0006] This invention was made in view of the above-mentioned technical problems, and aims to provide a control device for a hybrid vehicle that can achieve both improved off-road capability and improved drivability when driving while maintaining a large gear ratio. [Means for solving the problem]

[0007] To achieve the above objective, this invention provides a control device for a hybrid vehicle equipped with an engine and a motor as driving force sources, a transmission connected to the output side of the driving force sources, and during hybrid driving where the vehicle is driven by the torque output by the engine and the torque output by the motor, the device performs intermittent operation of the engine when predetermined conditions are met, and selects between a first mode that controls the driving force for driving based on the driving state including vehicle speed or required driving force, and a second mode that limits the driving force, wherein the device has a controller that controls the operation of the engine, and the controller sets the gear ratio set in the transmission to a predetermined low speed The device is characterized by comprising: a gear ratio determination unit that determines that the gear ratio is limited; a mode determination unit that determines that the second mode is selected; and an intermittent operation control unit that permits intermittent operation when the gear ratio determination unit determines that the gear ratio set in the transmission is limited to the predetermined low gear ratio and the second mode is selected, and prohibits intermittent operation when the gear ratio determination unit determines that the gear ratio set in the transmission is limited to the predetermined low gear ratio and the second mode is not selected.

[0008] In this invention, in the second mode, the driving force may be limited by a limiting control that includes either a vehicle speed limit that restricts the vehicle speed to a predetermined vehicle speed or less, or a differential limit that restricts the differential rotation of the left and right wheels or the front and rear wheels. [Effects of the Invention]

[0009] According to this invention, intermittent engine operation is permitted when the gear ratio is limited to a predetermined low gear ratio and the second mode is selected to limit the driving force. The limiting of the driving force by the second mode is such as limiting the driving force so that the vehicle speed falls below a predetermined vehicle speed, or limiting the differential rotation of the left and right or front and rear wheels. Intermittent operation is a control that stops the engine and drives the vehicle using the motor when predetermined conditions are met. Therefore, when driving while maintaining a low gear ratio and limiting the vehicle speed or differential rotation of the wheels, the engine stops, but the vehicle is driven by the motor. As a result, the driving force is stable, or if the driving force changes, it changes smoothly, thus improving driving performance. On the other hand, when the gear ratio is limited to a low gear ratio but the second mode is not selected, intermittent engine operation is prohibited and the engine continues to run, so there is no engine starting and no accompanying changes in driving force or shocks, as a result, drivability can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing the drive system in an embodiment of the present invention. [Figure 2] This is a skeleton diagram showing an example of the hybrid drive mechanism. [Figure 3] This is a block diagram showing the functional configuration of the controller. [Figure 4] This is a flowchart illustrating an example of the control performed by the controller. [Modes for carrying out the invention]

[0011] Next, embodiments of this invention will be described with reference to the attached drawings. It should be noted that the embodiments described below are merely examples of how to implement this invention and do not limit it.

[0012] 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 forces, and capable of transmitting the torque output by the engine and the torque output by the motor to the drive wheels. Figure 1 schematically shows the drive system of the hybrid vehicle 1. The driving force source 2 is equipped with an engine 3 such as a gasoline engine and a motor 4, and is capable of driving using engine 3 (engine driving), driving using motor 4 (EV driving), and driving using engine 3 and motor 4 (hybrid driving). A skeleton diagram of the hybrid drive mechanism that enables such driving is shown in Figure 2.

[0013] In Figure 2, the symbol "5" indicates a planetary gear mechanism that constitutes the power split mechanism. This differential mechanism has a sun gear 6, a ring gear 7, and a carrier 9 that holds the pinion gear 8 meshing with the sun gear 6 and ring gear 7 as its rotating elements. The engine 3 is connected to the carrier 9, and the first motor 10 is connected to the sun gear 6. The ring gear 7 is the output element, and the output member 11 is connected to the ring gear 7. Furthermore, the second motor 12 is connected to the output member 11. These first motor 10 and second motor 12 constitute the motor 4. It is optional to provide a clutch between the ring gear 7 and the carrier 9, or a clutch between the ring gear 7 and the output member 11, or to provide a mechanism to selectively connect certain members or to stop rotation.

[0014] The power output from engine 3 is divided by the planetary gear mechanism 5 between the sun gear 6 and the ring gear 7, and some of the power is output to the output member 11 via the ring gear 7. In contrast, torque is input to the sun gear 6 from the first motor 10 to control the engine speed, and in the case of steady-state hybrid driving, the first motor 10 functions as a generator and a reaction torque is input to the sun gear 6. As a result, the torque of the ring gear 7 becomes greater than the torque output by engine 3. The electricity generated by the first motor 10 applying a reaction torque to the sun gear 6 is sent to the second motor 12, which functions as a motor, and its output torque is output from the output member 11. Note that the first motor 10 and the second motor 12 can also be driven by power from an energy storage device (not shown).

[0015] A transmission 13 is connected to the output side of the drive force source 2. The transmission 13 is, for example, a gear transmission and is configured to allow setting multiple gear ratios for forward travel, a reverse travel state, and a neutral position that does not output torque. The gear ratio switching, i.e., the gear shifting, 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 and transmits the torque output from the transmission 13 to the rear wheel 15 side and the front wheel 16 side, and can be configured, for example, by a differential mechanism consisting of three rotating elements. An example of a differential mechanism is a mechanism in which a pinion gear made of bevel gears is meshed between a pair of side gears made of bevel gears, and the pinion gear is made to revolve and rotate, or a planetary gear mechanism. A differential limiting clutch (not shown) is also provided to limit or prohibit the differential action.

[0016] The transfer case 14 is equipped with a rear output shaft 17 and a front output shaft 18. The rear output shaft 17 is connected to a rear differential (hereinafter referred to as rear differential) 19, which is the final reduction gear, and the left and right rear wheels 15 are connected to this rear differential 19. The rear differential 19 is equipped with a differential limiting clutch (not shown) that limits or prohibits the differential rotation of the left and right rear wheels 15.

[0017] Furthermore, the front wheel output shaft 18 is connected to the front differential (hereinafter referred to as the front differential) 21, which is the final reduction gear, via a 2-4 switching clutch 20. The left and right front wheels 16 are connected to the front differential 21. The front differential 21 is equipped with a differential limiting clutch (not shown) that limits or prohibits the differential rotation of the left and right front wheels 16, similar to the rear differential 19 described above.

[0018] The 2-4 switching clutch 20 is a clutch that selectively interrupts the transmission of torque to the front differential 21 or the front wheels 16 via the front wheel output shaft 18. Engaging the 2-4 switching clutch 20 results in a four-wheel drive state, and conversely, disengaging the 2-4 switching clutch 20 results in a two-wheel drive state. In the two-wheel drive state, the differential limiting clutch in the transfer case 14 is engaged to ensure torque is output to the rear wheel output shaft 17. The 2-4 switching clutch 20 may also be integrated into the transfer case 14.

[0019] The transmission 13 is a conventionally known automatic transmission, and a shift device 22 is provided for switching the gear shift state of the transmission 13. The shift device 22 is configured to allow the user to select a position using a shift lever, and these positions include parking (P), reverse (R), neutral (N), and drive (D). Furthermore, the hybrid vehicle 1 shown in Figure 1 is equipped with the transmission 13, transfer case 14, and final reduction gears 19 and 21 with differential limiting clutches, allowing it to switch between two-wheel drive, four-wheel drive, or a state with limited driving force, and a changeover switch 23 is provided to select these drive states. The drive states that can be selected by the changeover switch 23 are a two-wheel drive state H2 with no limit on driving force, a four-wheel drive state H4 with no limit on driving force, and a four-wheel drive state L4 that restricts upshifts and frequently uses a predetermined low gear ratio.

[0020] Furthermore, the hybrid vehicle 1 is equipped with a Multi Terrain Select (MTS) system that sets the driving state to perform driving suitable for the road surface conditions. The selectable road surface conditions are, for example, "SAND" suitable for driving on sandy roads, "MUD" suitable for driving on muddy roads, "ROCK" suitable for driving on rocky roads, and the like. An MTS switch 24 is provided for manually selecting these driving states. In the driving states respectively suitable for the road surface conditions listed here, differential restriction is performed to maintain the four-wheel drive state, or driving force restriction for restricting the vehicle speed to a predetermined vehicle speed or less is executed. Such control can be executed by a conventionally known power control computer, brake computer, four-wheel drive computer, and the like. Therefore, the "restriction of driving force" in the embodiment of this invention means restricting the gear ratio set by the transmission 13 to a predetermined large gear ratio (that is, a low-speed gear ratio), and controlling the output torque of the power source 2 so that the vehicle speed becomes less than a predetermined vehicle speed, or control for restricting the differential rotation of the front and rear four wheels, and the like, which is control for restricting the driving state of the hybrid vehicle 1.

[0021] Note that the hybrid vehicle 1 shown in FIG. 1 is equipped with operating devices such as a steering wheel 25, an accelerator pedal 26, and a brake pedal (not shown) that a normal vehicle has.

[0022] When the above hybrid vehicle 1 is in a state of hybrid driving with the engine 3 and the motor 4 being driven, if the remaining charge (SOC) in a power storage device (not shown) connected to the motor 4 is sufficiently large and the motor 4 can satisfy the driving requirement, for example, when the accelerator opening is small, the engine 3 is stopped and motor driving is performed. Also, when the required driving force increases due to the accelerator pedal 26 being depressed or the SOC of the power storage device decreases, the engine 3 is restarted. The control of stopping the operation of the engine 3 during such driving is referred to as intermittent operation. The intermittent operation of the engine 3 during hybrid driving is basically performed on the condition that the motor 4 can satisfy the driving requirement as described above. In the control device according to an embodiment of this invention, in addition to that condition, the intermittent operation is performed on the condition that the driving force or the driving state is restricted.

[0023] A controller 27 for controlling the intermittent operation is provided. The controller 27 is an electronic control device mainly composed of a microcomputer including an arithmetic element (CPU), a storage element (RAM, ROM), and an interface, etc. It is configured to perform arithmetic operations according to a predetermined program using the input data and the data stored in advance, and output the result of the arithmetic operation as a control command signal. The input data includes the signal of the driving state selected by the above switching switch 23, the signal of the road surface state selected by the MTS switch 24, etc. The controller 27 outputs a command signal for permitting or prohibiting the intermittent operation based on these input data.

[0024] The functional configuration of the controller 27 for performing this control is shown in a block diagram in Figure 3. The controller 27 is equipped with a gear ratio determination unit 27a. The gear ratio determination unit 27a determines that the gear ratio set by the transmission 13 described above is limited to a predetermined large gear ratio (low gear ratio). This determination can be made based on the drive state selected by the changeover switch 23. For example, if the four-wheel drive state L4, which restricts upshifts and frequently uses a predetermined low gear ratio, is selected, the determination that the gear ratio is limited to a low gear ratio is made.

[0025] Furthermore, the controller 27 includes a mode determination unit 27b. Here, the mode is a driving state suitable for the road surface condition selected by the MTS switch 24, and the mode determination unit 27b determines that the second mode is selected when any of the aforementioned "SAND," "MUD," or "ROCK" is selected. In particular, in the embodiment described here, the mode determination unit 27b determines that the second mode is selected when "ROCK" is selected. Note that when the MTS switch 24 is not operated and no driving state is selected, the state in particular when "ROCK" is not selected corresponds to the first mode in this embodiment of the invention.

[0026] Furthermore, the controller 27 is equipped with an intermittent operation control unit 27c. The intermittent operation control unit 27c is a control unit that prohibits and permits intermittent operation of the engine 3. It permits intermittent operation (stopping the engine 3) when the gear ratio is limited to a low gear ratio and "ROCK" is selected as the drive state, and prohibits intermittent operation in all other drive states.

[0027] An example of the control performed by the controller 27 described above is shown in a flowchart in Figure 4. The routine shown in Figure 4 is repeatedly executed by the controller 27 when the hybrid vehicle 1 is running. First, in step S1, it is determined whether or not the L4 range is selected. This determination can be made based on the signal output when a predetermined drive state is selected by the changeover switch 23 mentioned above.

[0028] If the result of the determination in step S1 is "yes," then in step S2, it is determined whether or not "ROCK" is selected by the MTS switch 24. This determination can be made based on the signal output when a predetermined drive state (mode) is selected by the aforementioned MTS switch 24.

[0029] If the result of the judgment in step S2 is "yes," the system proceeds to step S3, requests intermittent operation permission, and returns. That is, if the result of the judgment in step S2 is "yes," the gear ratio is limited to a predetermined low gear ratio or lower, the vehicle speed is below a predetermined vehicle speed, and the differential limiting of the front and rear four wheels is in place, so a command signal is output to permit intermittent operation, which prohibits the operation of engine 3. In this case, the vehicle will be driven by motor 4 (especially the second motor 12), but since the gear ratio is limited to a predetermined large gear ratio, a sufficiently large driving force can be output. Furthermore, since the torque output by motor 4 (second motor 12) is a smooth torque that changes according to the current, a linearly changing driving force can be obtained even when driving on rough roads such as rocky roads, and the driving performance is improved accordingly. Moreover, since there are almost no sudden changes in driving force, stable driving can be performed.

[0030] If the result of the judgment in step S2 is "no", the system proceeds to step S4, where an intermittent operation prohibition request is made and the system returns. In other words, a command signal prohibiting intermittent operation is output, preventing the engine 3 from stopping and allowing the engine 3 to continue operating. Therefore, since the situation of restarting the engine 3 after stopping does not occur, fluctuations in driving force or shocks associated with restarting the engine 3 can be avoided, and drivability can be improved.

[0031] If the result of the judgment 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 system returns. This control is the normal control in hybrid vehicles.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration of the embodiment described above, and the configuration of the powertrain, hybrid drive mechanism, and transmission may be any conventionally known configuration. Therefore, the hybrid vehicle may be a front-wheel drive-based four-wheel drive vehicle instead of a rear-wheel drive-based four-wheel drive vehicle. Furthermore, the device for switching the drive state may be a lever type instead of the aforementioned switch. [Explanation of Symbols]

[0033] 1. Hybrid vehicle 2. Power source 3 Engines 4 motors 5 Planetary gear mechanism 6 Sangiya 7 Ring Gear 8 pinion gears 9 Carrier 10 First Motor 11 Output component 12. Second motor 13. Transmission 14 Transfer 15 Rear wheel 16 Front Wheel 17 Rear wheel output axle 18 Front wheel output axle 19 Rear differential 20 Switching clutch 21 Front Differential 22 Shift device 23 Changeover switch 24 MTS Switch 25 Steering Wheel 26. Accelerator pedal 27 Controllers 27a Gear ratio determination unit 27b Mode determination unit 27c Intermittent Operation Control Unit

Claims

1. A control device for a hybrid vehicle equipped with an engine and a motor as driving force sources, a transmission connected to the output side of the driving force sources, and during hybrid driving where the vehicle is driven by the torque output by the engine and the torque output by the motor, the control device performs intermittent operation of the engine when predetermined conditions are met, and selects between a first mode that controls the driving force for driving based on the driving state including vehicle speed or required driving force, and a second mode that limits the driving force, It has a controller that controls the operation of the engine, The aforementioned controller, A gear ratio determination unit that determines that the gear ratio set in the transmission is limited to a predetermined low gear ratio, A mode determination unit that determines whether the second mode is selected, The intermittent operation control unit permits intermittent operation when the gear ratio determination unit determines that the gear ratio set in the transmission is limited to the predetermined low gear ratio and the mode determination unit determines that the second mode is selected, and when the gear ratio determination unit determines that the gear ratio set in the transmission is limited to the predetermined low gear ratio and the mode determination unit does not determine that the second mode is selected. It is equipped with A control device for a hybrid vehicle characterized by the following features.

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

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