Vehicle control device

Abstract

To provide a vehicle control device that can improve re-acceleration performance during FC (Fuel Cut) control at high revolutions.SOLUTION: When it is determined that an engine rotation speed is approaching a predetermined high-speed range, a lock-up clutch is controlled to a slip state, and when it is determined that the engine rotation speed is within the predetermined high-speed range, an engagement pressure of the lock-up clutch is reduced based on predetermined conditions as compared with that when it is determined that the engine rotation speed is approaching the predetermined high-speed range. As a result, when the execution of FC control at high revolutions is expected, an engaged state of the lock-up clutch is released in advance, and when the FC control at high revolutions is executed, the engaged state of the lock-up clutch is reliably released, so that a decrease in durability of dampers, etc., is suppressed. Furthermore, since the release of the engaged state of the lock-up clutch is achieved within a range in which the slip state can be maintained, the lock-up clutch can be quickly returned to an engaged state as required.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that has a lock-up clutch in a power transmission path between an engine and an automatic transmission. [Background technology]

[0002] There are well-known control devices for vehicles that include an engine, an automatic transmission provided in a power transmission path between the engine and drive wheels, and a direct-coupled clutch provided in the power transmission path between the engine and the automatic transmission. For example, Patent Document 1 discloses a vehicle computer that disengages a lock-up clutch as a direct-coupled clutch when a high engine rotation speed and a high vehicle speed state have continued for a predetermined time, and then, after a second predetermined time or more has passed since the high engine rotation speed and the high vehicle speed state, executes a maximum speed fuel cut to stop fuel supply to the engine when the vehicle speed exceeds the predetermined vehicle speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-65839 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, when driving on a circuit, automatic transmission shift control may be performed to target a maximum engine speed that is acceptable for engine durability. In this case, high-speed fuel cutoff (FC) control may be performed, which stops fuel supply to the engine when the engine speed enters a predetermined high-speed range that includes the maximum engine speed. During high-speed FC control, the engine torque fluctuates over a short period of time due to repeated activation and deactivation caused by fluctuations in engine speed resulting from the fuel cutoff. This may reduce the durability of dampers and other components in the power transmission path between the engine and the automatic transmission. To address this issue, a lockup clutch may be disengaged during high-speed FC control to protect the dampers and other components. In this case, when re-accelerating after the high-speed FC control ends, the lockup clutch is released, which requires time to engage the lockup clutch, potentially preventing the desired acceleration.

[0005] The present invention has been made in light of the above circumstances, and its purpose is to provide a vehicle control device that can improve re-acceleration performance during FC control at high revolutions. [Means for solving the problem]

[0006] The gist of a first aspect of the present invention is a control device for a vehicle including: (a) an engine; an automatic transmission provided in a power transmission path between the engine and drive wheels; and a direct-coupled clutch provided in the power transmission path between the engine and the automatic transmission for connecting the engine and the automatic transmission, the control device including: (b) an engine control unit that stops fuel supply to the engine when the rotation speed of the engine is in a predetermined high rotation range; and (c) a control unit that determines whether the rotation speed of the engine is approaching the predetermined high rotation range and whether the rotation speed of the engine is within the predetermined high rotation range. and (d) a direct-coupled clutch control unit that, when controlling the direct-coupled clutch to an engaged state, controls the direct-coupled clutch to a slip state if it is determined that the engine rotation speed is approaching the predetermined high rotation speed region, and, when it is determined that the engine rotation speed is in the predetermined high rotation speed region, reduces the engagement pressure of the direct-coupled clutch based on predetermined conditions to a level that is lower than when it is determined that the engine rotation speed is approaching the predetermined high rotation speed region, within a range that allows the torque capacity of the direct-coupled clutch to be quickly increased and maintains a slip state. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when the direct-coupled clutch is engaged and it is determined that the engine speed is approaching a predetermined high-speed range in which high-speed FC control is performed, the direct-coupled clutch is controlled to a slip state. Additionally, when it is determined that the engine speed is in the predetermined high-speed range, the engagement pressure of the direct-coupled clutch is reduced based on predetermined conditions to a level lower than when it is determined that the engine speed is approaching the predetermined high-speed range, within a range in which a slip state in which torque capacity is rapidly increased can be maintained. This allows the direct-coupled clutch to be released in advance when high-speed FC control is anticipated. Furthermore, when high-speed FC control is performed, the direct-coupled clutch is reliably released, thereby suppressing a decrease in durability of components such as dampers. Furthermore, the direct-coupled clutch is released from its engaged state within a range in which a slip state in which torque capacity is rapidly increased can be maintained, rather than being completely released. This allows the direct-coupled clutch to be quickly returned to an engaged state as needed. This improves re-acceleration performance during high-speed FC control. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram illustrating main parts of control functions and control systems for various controls in the vehicle. [Figure 2] FIG. 10 is a diagram illustrating an example of a transition of a control phase for improving re-acceleration performance during FC control at high rotation speeds. [Figure 3] 1 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for improving re-acceleration performance during FC control at high revolutions. [Figure 4] 4 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 3 is executed. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0010] 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrates the main parts of the control functions and control systems for various controls in the vehicle 10. In FIG. 1, the vehicle 10 includes an engine 12, drive wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0011] The engine 12 is a known internal combustion engine, and the engine torque Te, which is the torque of the engine 12, is controlled by an electronic control device 80 described later, which controls an engine control device 50 including a fuel injection device and the like provided on the vehicle 10.

[0012] The power transmission device 16 includes, within a case 18, which is a non-rotating member, a torque converter 20 connected to the engine 12, an automatic transmission 22 connected to the torque converter 20, and the like. The power transmission device 16 also includes, within a case 18, a propeller shaft 26 connected to a transmission output shaft 24, a differential gear 28 connected to the propeller shaft 26, a pair of drive shafts 30 connected to the differential gear 28, and the like. The transmission output shaft 24 is an output member of the automatic transmission 22. The power transmission device 16 also includes, within a case 18, an engine connecting shaft 32 that connects the engine 12 and the torque converter 20, and the like.

[0013] The torque converter 20 includes a pump wheel 20a connected to an engine connecting shaft 32 and a turbine wheel 20b connected to a transmission input shaft 34. The transmission input shaft 34 is an input member of the automatic transmission 22. The torque converter 20 is a fluid-type power transmission device that transmits power from the engine 12 from the engine connecting shaft 32 to the transmission input shaft 34 via fluid.

[0014] The torque converter 20 includes an LU clutch 36 that connects the pump wheel 20a and the turbine wheel 20b. The LU clutch 36 is a direct-coupled clutch that is provided in a power transmission path between the engine 12 and the automatic transmission 22 and connects the engine 12 and the automatic transmission 22. The LU clutch 36 is a known lock-up clutch, such as a hydraulic friction engagement device. The control state of the LU clutch 36 is switched by changing the LU torque Tlu, which is the torque capacity of the LU clutch 36, using the LU oil pressure PRlu. The LU oil pressure PRlu is a regulated engagement pressure that is supplied to the LU clutch 36 from a hydraulic control circuit 52 provided in the vehicle 10.

[0015] The control states of the LU clutch 36 include a released state (also referred to as a fully released state), a slip state in which the LU clutch 36 is engaged with slippage, and an engaged state (also referred to as a fully engaged state). When the LU clutch 36 is in the released state, the torque converter 20 is in a torque converter state in which torque amplification is achieved. When the LU clutch 36 is in the engaged state, the torque converter 20 is in a lockup state (also referred to as a fully locked up state) in which the pump wheel 20a and the turbine wheel 20b rotate together.

[0016] The power transmission device 16 also includes a damper 38 disposed in the power transmission path between the LU clutch 36 and the transmission input shaft 34. The damper 38 is, for example, a pulsation absorbing damper. The damper 38 may be disposed in the power transmission path between the engine 12 and the automatic transmission 22.

[0017] The automatic transmission 22 is, for example, a known planetary gear type automatic transmission equipped with engagement devices CB. The engagement devices CB include a plurality of known hydraulic friction engagement devices. Each of the engagement devices CB has its torque capacity, or CB torque Tcb, changed by the CB oil pressure PRcb, thereby switching between control states such as an engaged state, a slip state, and a disengaged state. The CB oil pressure PRcb is a regulated engagement pressure supplied to the engagement devices CB from the hydraulic control circuit 52.

[0018] The automatic transmission 22 is a stepped transmission in which one of a plurality of gear stages (also referred to as gear ratios) with different speed ratios (also referred to as gear ratios) γ (=AT input rotation speed Ni / AT output rotation speed No) is formed by engaging one of the engagement devices CB. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 34, and is the input rotation speed of the automatic transmission 22. The AT input rotation speed Ni is equal to the turbine rotation speed Nt, which is the output rotation speed of the torque converter 20. The AT output rotation speed No is the rotation speed of the transmission output shaft 24, and is the output rotation speed of the automatic transmission 22.

[0019] The vehicle 10 is equipped with a mechanical oil pump 54. The oil pump 54 is connected to the pump impeller 20a, and is rotationally driven by the engine 12 to discharge hydraulic oil OIL for use in the power transmission device 16. The hydraulic oil OIL discharged by the oil pump 54 is supplied to the hydraulic control circuit 52. The hydraulic control circuit 52 supplies the CB hydraulic pressure PRcb, the LU hydraulic pressure PRlu, and the like, each of which is adjusted based on the hydraulic oil OIL discharged by the oil pump 54.

[0020] The vehicle 10 further includes an electronic control device 80 as a controller including control devices for the vehicle 10 related to the control of the engine 12 and the automatic transmission 22. The electronic control device 80 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various controls of the vehicle 10 by performing signal processing in accordance with a program stored in advance in the ROM while utilizing, for example, the temporary storage function of the RAM.

[0021] The electronic control device 80 receives various signals (e.g., engine rotation speed Ne, AT input rotation speed Ni (= turbine rotation speed Nt), AT output rotation speed No, accelerator opening θacc, throttle valve opening θth, brake-on signal Bon, hydraulic oil temperature THoil, etc.) based on detected values ​​from various sensors provided on the vehicle 10 (e.g., engine rotation speed sensor 60, input rotation speed sensor 62, output rotation speed sensor 64, accelerator opening sensor 66, throttle valve opening sensor 68, brake sensor 70, oil temperature sensor 72, etc.). The engine rotation speed Ne is the rotation speed of the engine 12. The AT output rotation speed No is the rotation speed corresponding to the vehicle speed V. The accelerator opening θacc is the amount of accelerator operation by the driver, which indicates the magnitude of the driver's acceleration operation. The throttle valve opening θth is the opening of the electronic throttle valve. The brake-on signal Bon is a signal indicating a state in which the brake pedal for activating the wheel brakes is being operated by the driver. The hydraulic oil temperature THoil is the temperature of the hydraulic oil OIL.

[0022] The electronic control device 80 outputs various command signals (e.g., engine control command signal Se, CB hydraulic control command signal Scb, LU hydraulic control command signal Slu, etc.) to each device (e.g., engine control device 50, hydraulic control circuit 52, etc.) provided in the vehicle 10. The engine control command signal Se is a command signal for controlling the engine 12. The CB hydraulic control command signal Scb is a command signal for controlling the engagement device CB. The LU hydraulic control command signal Slu is a command signal for controlling the LU clutch 36.

[0023] Each hydraulic control command signal S will be described using the LU hydraulic control command signal Slu as an example. The electronic control device 80 calculates the LU command hydraulic pressure Splu, which is the command hydraulic pressure of the LU clutch 36 for causing the hydraulic control circuit 52 to supply the LU hydraulic pressure PRlu as the command value of the LU hydraulic pressure PRlu. The electronic control device 80 converts the LU command hydraulic pressure Splu into an LU command current value Silu for driving the LU solenoid SLlu, which is provided in the hydraulic control circuit 52 and outputs the LU hydraulic pressure PRlu. The LU command current value Silu is a command current for a solenoid driver provided in the electronic control device 80 that drives the LU solenoid SLlu. The LU hydraulic control command signal Slu is a drive current or drive voltage for the solenoid driver to drive the LU solenoid SLlu based on the LU command current value Silu. In other words, the LU command hydraulic pressure Splu is converted into the LU hydraulic control command signal Slu and output to the hydraulic control circuit 52. In this embodiment, for convenience, the LU command hydraulic pressure Splu and the LU hydraulic control command signal Slu are treated as the same.

[0024] In order to realize various controls in the vehicle 10, the electronic control device 80 includes an engine control means, i.e., an engine control section 82, a transmission control means, i.e., a transmission control section 84, and an LU clutch control means, i.e., an LU clutch control section 86.

[0025] The engine control unit 82 calculates a drive demand amount from the driver for the vehicle 10, such as a demanded drive torque Trdem at the drive wheels 14, by applying the accelerator opening θacc and the vehicle speed V to a drive demand amount map, which is a relationship that has been obtained in advance experimentally or by design and stored, i.e., a predetermined relationship. The engine control unit 82 outputs an engine control command signal Se to the engine control device 50 to control the engine 12 so as to obtain a demanded engine torque Tereq for realizing the demanded drive torque Trdem, which has been calculated in consideration of transmission loss, accessory load, gear ratio γ, etc.

[0026] When the engine rotation speed Ne is in the FC rotation speed region ARfc, the engine control unit 82 executes high rotation FC control CNfc to stop fuel supply to the engine 12. The FC rotation speed region ARfc is a predetermined high rotation region that is equal to or lower than the FC rotation speed Nefc and is in the vicinity of the FC rotation speed Nefc. The FC rotation speed Nefc is an engine rotation speed Ne that is predetermined as a high rotation speed that should not be exceeded in terms of durability of the engine 12. The engine rotation speed Ne in the vicinity of the FC rotation speed Nefc is a region of the engine rotation speed Ne that is predetermined as a range of high rotation speeds that are undesirable in terms of durability of the engine 12.

[0027] The FC rotation speed Nefc may be changed based on, for example, the engine water temperature, the warm-up state of the engine 12, the learning state of the engine 12, etc. For example, when the engine water temperature is low, a lower FC rotation speed Nefc is set compared to when the engine water temperature is high. Also, when the engine 12 is warming up, a lower FC rotation speed Nefc is set compared to when the warm-up of the engine 12 is complete. Also, when learning of the engine torque Te is not in progress, a lower FC rotation speed Nefc is set compared to when learning of the engine torque Te is in progress.

[0028] The transmission control unit 84 determines whether to shift the automatic transmission 22 using, for example, a shift map having a predetermined relationship, and outputs a CB hydraulic control command signal Scb to the hydraulic control circuit 52 as necessary, that is, in accordance with the result of the shift determination, to execute shift control of the automatic transmission 22.

[0029] The LU clutch control unit 86 is a direct-coupled clutch control unit that controls the control state of the LU clutch 36. That is, the LU clutch control unit 86 controls the LU clutch 36 to be in one of the control states of a released state, a slip state, and an engaged state. For example, the LU clutch control unit 86 determines the control region using a lock-up region diagram, which is a predetermined relationship, and outputs an LU hydraulic control command signal Slu to the hydraulic control circuit 52 to supply the LU clutch 36 with an LU hydraulic pressure PRlu that achieves the control state corresponding to the determined control region. The lock-up region diagram is a predetermined relationship that has a release region corresponding to the released state, a slip region corresponding to the slip state, and a lock-up region corresponding to the engaged state on a two-dimensional coordinate system with vehicle speed V and required drive torque Trdem as variables, for example.

[0030] When the LU clutch control unit 86 determines that the control region is the lockup region, it controls the LU clutch 36 to an engaged state, i.e., executes lockup control CNluon. The lockup control CNluon is control that sets the LU hydraulic pressure PRlu so that an LU torque Tlu capable of transmitting the LU input torque Tinlu is obtained, and brings the LU clutch 36 into a fully engaged state. The LU input torque Tinlu is the input torque to the LU clutch 36 and is the same as, for example, the engine torque Te. The LU torque Tlu capable of transmitting the LU input torque Tinlu is, for example, a torque value obtained by multiplying the LU input torque Tinlu by a safety factor (>1). On the other hand, when the LU clutch control unit 86 determines that the control region is the release region, it sets the LU hydraulic pressure PRlu to zero, and brings the LU clutch 36 into a fully released state.

[0031] On the other hand, if the LU torque Tlu is small relative to the LU input torque Tinlu, slippage occurs in the LU clutch 36. When the LU clutch control unit 86 determines that the control region is the slip region, it controls the LU clutch 36 to a slip state, i.e., executes LU slip control CNlusp. The LU slip control CNlusp controls the LU clutch 36 to a slip state by setting the LU hydraulic pressure PRlu to achieve the target LU slip amount Nslplut relative to the LU input torque Tinlu, i.e., slip control of the LU clutch 36. The target LU slip amount Nslplut is the slip amount of the LU clutch 36, i.e., the target value of the LU slip amount Nslplu. The LU slip amount Nslplu is the input / output rotational speed difference of the LU clutch 36, i.e., the rotational speed difference (= Ne - Nt) between the LU input rotational speed (= engine rotational speed Ne) and the LU output rotational speed (= turbine rotational speed Nt). The target LU slip amount Nslplut is a predetermined input / output rotational speed difference that is set in advance. In the lockup region diagram, the slip region is set, for example, in a lower vehicle speed region compared to the lockup region. The slip region is a region where it is difficult to execute lockup control CNluon, and is set to improve energy efficiency and drivability by creating a slip state. The slip region is also a region set in consideration of drivability, muffled noise, etc. (for example, NV (noise and vibration) performance).

[0032] During execution of the LU slip control CNlusp, the LU clutch control unit 86 corrects the LU hydraulic pressure PRlu, i.e., the LU torque Tlu, by feedback (FB) control so that the LU slip amount Nslplu becomes the target LU slip amount Nslplut. The LU clutch control unit 86 corrects the LU torque Tlu by adding the FB LU hydraulic pressure PRlufb, which serves as the FB amount, to the FF LU hydraulic pressure PRluff, which serves as the feedforward (FF) amount of the LU hydraulic pressure PRlu. The FB LU hydraulic pressure PRlufb is a correction amount for the LU hydraulic pressure PRlu that corrects the FF LU hydraulic pressure PRluff. The LU clutch control unit 86 calculates the FF LU hydraulic pressure PRluff using, for example, a map or function in which values ​​corresponding to the LU input torque Tinlu and the target LU slip amount Nslplut are predetermined. The map or function is predetermined so that, for example, the FF LU hydraulic pressure PRluff becomes a larger value as the LU input torque Tinlu becomes larger. The LU clutch control unit 86 calculates the FB LU oil pressure PRlufb using a predetermined FB control equation having a proportional term (P component), an integral term (I component), and a derivative term (D component) based on, for example, the slip amount difference. The slip amount difference is the difference between the LU slip amount Nslplu and the target LU slip amount Nslplut (=Nslplu-Nslplut). In this way, the LU clutch control unit 86 executes LU slip control CNlusp by FB control, which controls the LU clutch 36 to a slip state according to the LU input torque Tinlu so that the LU slip amount Nslplu becomes the target LU slip amount Nslplut. Examples of the LU slip control CNlusp include acceleration slip control executed when accelerating with the accelerator on and deceleration slip control executed when decelerating with the accelerator off.

[0033] Here, when the high revolution FC control CNfc is being executed, the LU input torque Tinlu, i.e., the engine torque Te, is generated intermittently, so it is conceivable to control the LU clutch 36 to a released state in order to protect hardware such as the damper 38. However, when re-accelerating after the high revolution FC control CNfc has ended, acceleration occurs from the released state of the LU clutch 36. Therefore, a considerable amount of time is required before the LU clutch 36 is controlled to an engaged state, and there is a risk that the desired acceleration will not be achieved.

[0034] Therefore, when it is expected that the engine rotation speed Ne will approach the FC rotation speed region ARfc, the LU clutch control unit 86 executes the LU slip control CNlusp before the high rotation speed FC control CNfc is executed, that is, executes the pre-FC slip control CNspbfc. This makes it possible to achieve hardware protection when the high rotation speed FC control CNfc is executed while maintaining a power transmission state equivalent to when the torque converter 20 is in a lockup state. Furthermore, because the LU clutch 36 is not in a completely released state, it is possible to control the LU clutch 36 to a quickly engaged state when it is expected that the engine rotation speed Ne will move away from the FC rotation speed region ARfc.

[0035] Furthermore, when the engine rotation speed Ne enters the FC rotation speed region ARfc, the LU clutch control unit 86 executes FC slip control CNspfc, which switches the LU oil pressure PRlu in the LU slip control CNlusp from the pre-FC slip control CNspbfc. This makes it possible to achieve hardware protection equivalent to that achieved when the LU clutch 36 is in a fully released state while the high rotation FC control CNfc is being executed. Also, because the LU clutch 36 is not in a fully released state, when re-accelerating after the high rotation FC control CNfc ends, the LU clutch 36 accelerates from its slip state, and the LU clutch 36 can be quickly controlled to an engaged state, making it easier to achieve the desired acceleration.

[0036] FIG. 2 is a diagram illustrating an example of a control phase transition for improving re-acceleration performance during high-speed FC control CNfc. In FIG. 2, phase [0] and phase [4] are both steady-state control phases in which lockup control CNluon is executed. If transition condition [1] is satisfied during phase [0], a transition to phase [1] occurs. Phase [1] is a control phase in which pre-FC slip control CNspbfc is executed. Transition condition [1] is, for example, a condition in which it is determined that the engine speed Ne is approaching the FC speed region ARfc. If transition condition [2] is satisfied during phase [1], a transition to phase [2] occurs. Phase [2] is a control phase in which FC slip control CNspfc is executed. Transition condition [2] is, for example, a condition in which it is determined that the engine speed Ne has entered the FC speed region ARfc. If transition condition [3] is satisfied during phase [2], a transition to phase [3] occurs. Phase [3] is a control phase in which pre-FC slip control CNspbfc is executed. Transition condition [3] is, for example, a condition in which it is determined that the engine rotation speed Ne has deviated from the FC rotation speed region ARfc. If transition condition [4] is satisfied during phase [3], the system transitions to phase [4]. Transition condition [4] is, for example, a condition in which it is determined that the engine rotation speed Ne is moving away from the FC rotation speed region ARfc.

[0037] The electronic control unit 80 further includes a rotation range determining means, that is, a rotation range determining unit 88, in order to realize a control operation that improves re-acceleration performance during high rotation FC control CNfc.

[0038] The rotation region determination unit 88 determines whether the engine rotation speed Ne is approaching the FC rotation speed region ARfc. The rotation region determination unit 88 determines whether the engine rotation speed Ne is approaching the FC rotation speed region ARfc, for example, based on whether the engine rotation speed Ne is equal to or higher than a rotation speed that is lower than the FC rotation speed region ARfc by a predetermined rotation speed. The rotation region determination unit 88 determines whether the engine rotation speed Ne is equal to or higher than a rotation speed that is lower than the FC rotation speed region ARfc by a predetermined rotation speed, for example, based on whether the engine rotation speed Ne is equal to or higher than a value (=Nefc-α) obtained by subtracting a predetermined rotation speed α from the FC rotation speed Nefc. The predetermined rotation speed α is, for example, a predetermined threshold value for determining whether the increasing engine rotation speed Ne is approaching the FC rotation speed region ARfc. Note that the predetermined rotation speed α may be predetermined as a threshold value to be subtracted from the lower limit value of the FC rotation speed region ARfc.

[0039] The rotation region determination unit 88 sets the predetermined rotation speed α to a larger value when the engine rotation speed Ne is likely to reach the FC rotation speed region ARfc compared to when the engine rotation speed Ne is unlikely to reach the FC rotation speed region ARfc. The state in which the engine rotation speed Ne is likely to reach the FC rotation speed region ARfc is, for example, when the accelerator opening θacc is large, when the automatic transmission 22 is in a low gear, or when the driving mode is a driving mode that prioritizes power performance over fuel economy. The state in which the engine rotation speed Ne is unlikely to reach the FC rotation speed region ARfc is, for example, when the accelerator opening θacc is small, when the automatic transmission 22 is in a high gear, or when the driving mode is a driving mode that prioritizes fuel economy over power performance. The low gear of the automatic transmission 22 is the gear with a larger gear ratio γ, i.e., a gear on the low vehicle speed side.

[0040] Further, the rotation region determination unit 88 determines whether or not the engine rotation speed Ne is within the FC rotation speed region ARfc.

[0041] When the rotation region determination unit 88 determines that the engine rotation speed Ne is approaching the FC rotation speed region ARfc while the lock-up control CNluon is being executed, the LU clutch control unit 86 executes pre-FC slip control CNspbfc. The pre-FC slip control CNspbfc is executed by the LU slip control CNlusp based on the FB control.

[0042] If the rotation region determination unit 88 determines that the engine rotation speed Ne is in the FC rotation speed region ARfc while pre-FC slip control CNspbfc is being executed, the LU clutch control unit 86 executes FC slip control CNspfc. FC slip control CNspfc may be executed by LU slip control CNlusp using FB control. Alternatively, FC slip control CNspfc may be executed by LU slip control CNlusp using FB control based on whether a predetermined condition CDsp is met, or by LU slip control CNlusp that reduces the LU hydraulic pressure PRlu compared to FB control.

[0043] When determining whether the engine rotation speed Ne is within the FC rotation speed region ARfc, the rotation region determination unit 88 determines whether a predetermined condition CDsp is satisfied. If the LU input torque Tinlu is large, even if FC slip control CNspfc is executed by LU slip control CNlusp through FB control, it may be difficult to achieve hardware protection for the damper 38 and the like. Therefore, the predetermined condition CDsp is a condition that the LU input torque Tinlu is equal to or greater than a predetermined input torque Tinluf. The predetermined input torque Tinluf is a predetermined threshold value for determining whether the LU input torque Tinlu is so high that it becomes difficult to achieve hardware protection for the damper 38 and the like. Alternatively, if the hydraulic oil temperature THoil is low, the controllability of LU slip control CNlusp through FB control is likely to deteriorate, and even if FC slip control CNspfc is executed, it may be difficult to achieve hardware protection for the damper 38 and the like. Therefore, the predetermined condition CDsp is a condition that the hydraulic oil temperature THoil is equal to or less than a predetermined oil temperature THoil. The predetermined oil temperature THoil is a predetermined threshold value for determining whether the hydraulic oil temperature THoil is such that it becomes difficult to protect the hardware such as the damper 38, for example.

[0044] When the rotational region determination unit 88 determines that the engine rotational speed Ne is in the FC rotational speed region ARfc, and when the rotational region determination unit 88 determines that the predetermined condition CDsp is not satisfied, the LU clutch control unit 86 maintains the LU slip control CNlusp by FB control. On the other hand, when the rotational region determination unit 88 determines that the engine rotational speed Ne is in the FC rotational speed region ARfc, and when the rotational region determination unit 88 determines that the predetermined condition CDsp is satisfied, the LU clutch control unit 86 reduces the LU oil pressure PRlu more than when the LU slip control CNlusp by FB control is executed.

[0045] The LU clutch control unit 86 reduces the LU hydraulic pressure PRlu within a range in which the LU slip control CNlusp is maintained. The range in which the LU slip control CNlusp is maintained is, for example, a range in which the LU hydraulic pressure PRlu when the LU slip control CNlusp is being executed by FB control is set to an upper limit hydraulic pressure, and the LU hydraulic pressure PRlu when the LU clutch 36 is in a packing completion state is set to a lower limit hydraulic pressure. The packing completion state of the LU clutch 36 is a state in which the pack clearance in the friction plates of the LU clutch 36 is reduced. The packing completion state of the LU clutch 36 is a state in which the LU clutch 36 begins to have an LU torque Tlu if the LU hydraulic pressure PRlu is increased from the packing completion state. By setting the LU hydraulic pressure PRlu when the LU clutch 36 is in a packing completion state to the lower limit hydraulic pressure, the LU torque Tlu is increased quickly when the LU clutch 36 transitions to an engaged state.

[0046] In this way, when the rotation range determination unit 88 determines that the engine rotation speed Ne is within the FC rotation speed region ARfc, the LU clutch control unit 86 reduces the LU oil pressure PRlu based on the predetermined condition CDsp, within a range that allows the slip state of the LU clutch 36 to be maintained and that allows the LU torque Tlu to be increased more quickly than when the rotation range determination unit 88 determines that the engine rotation speed Ne is approaching the FC rotation speed region ARfc.

[0047] FIG. 3 is a flowchart illustrating the main control operations of the electronic control unit 80, which are executed repeatedly, for example, to improve re-acceleration performance during high-speed FC control CNfc.

[0048] 3, first, in step S10 (hereinafter, the step number will be omitted) corresponding to the function of the LU clutch control unit 86, it is determined whether the torque converter 20 is in a complete lockup state, i.e., whether the lockup control CNluon is being executed. Note that the complete lockup state here also includes a state in which the torque converter 20 is slightly slipping even when the lockup control CNluon is being executed. If the determination in S10 is negative, the routine is terminated. If the determination in S10 is positive, then in S20 corresponding to the function of the rotational region determination unit 88, it is determined whether the engine rotational speed Ne is approaching the FC rotational speed region ARfc. If the determination in S20 is negative, the routine is terminated. If the determination in S20 is positive, then in S30 corresponding to the function of the LU clutch control unit 86, the lockup control CNluon is switched to pre-FC slip control CNspbfc, which is executed by the LU slip control CNlusp using FB control. Since the accelerator is on, the LU slip control CNlusp here is acceleration slip control. Next, in S40, which corresponds to the function of the rotation range determination unit 88, it is determined whether the engine rotation speed Ne is within the FC rotation speed region ARfc and whether a predetermined condition CDsp is met. If the determination in S40 is positive, in S50, which corresponds to the function of the LU clutch control unit 86, FC slip control CNspfc is executed by LU slip control CNlusp, which reduces the LU oil pressure PRlu compared to the LU slip control CNlusp by FB control. If the determination in S40 is negative, in S60, which corresponds to the function of the LU clutch control unit 86, the current slip state is maintained by LU slip control CNlusp by FB control.

[0049] Fig. 4 is a diagram showing an example of a time chart when the control operation shown in the flowchart of Fig. 3 is executed. In Fig. 4, if it is determined that the engine rotation speed Ne is approaching the FC rotation speed region ARfc during execution of the lock-up control CNluon (before time t1, see phase [0]), the pre-FC slip control CNspbfc is started (see time t1). If it is determined that the engine rotation speed Ne has further increased and entered the FC rotation speed region ARfc during execution of the pre-FC slip control CNspbfc (see time t1-t2, see phase [1]), the FC slip control CNspfc is started (see time t2). If the predetermined condition CDsp is not satisfied during execution of the FC slip control CNspfc (see time t2-t3, see phase [2]), the LU slip control CNlusp using FB control is maintained, as shown by the solid line. When a predetermined condition CDsp is satisfied during execution of the FC slip control CNspfc, LU slip control CNlusp is executed, which reduces the LU hydraulic pressure PRlu compared to the LU slip control CNlusp under FB control, as shown by the dashed line. If it is determined that the engine speed Ne has decreased and deviated from the FC speed region ARfc during execution of the FC slip control CNspfc, the FC slip control CNspfc is terminated, and LU slip control CNlusp equivalent to the pre-FC slip control CNspbfc is initiated (see time t3). If it is determined that the engine speed Ne has further decreased and is moving away from the FC speed region ARfc during execution of the LU slip control CNlusp equivalent to the pre-FC slip control CNspbfc (see time t3-t4, phase [3]), the LU slip control CNlusp is terminated, and lockup control CNluon is initiated (see time t4). This returns to steady-state control in which lockup control CNluon is executed (see time t4 and thereafter, phase [4]).

[0050] As described above, according to this embodiment, when the lock-up control CNluon is being executed and it is determined that the engine speed Ne is approaching the FC speed region ARfc, the pre-FC slip control CNspbfc is executed. Additionally, when it is determined that the engine speed Ne is within the FC speed region ARfc, the LU oil pressure PRlu is reduced, based on the predetermined condition CDsp, to a range in which a slip state of the LU clutch 36 can be maintained and in which the LU torque Tlu is rapidly increased, compared to when it is determined that the engine speed Ne is approaching the FC speed region ARfc. This allows the LU clutch 36 to be released from its engaged state in advance when the high-speed FC control CNfc is expected to be executed. Furthermore, when the high-speed FC control CNfc is executed, the LU clutch 36 is reliably released from its engaged state, thereby suppressing a decrease in the durability of the damper 38 and the like. Furthermore, the LU clutch 36 is released from its engaged state within a range in which a slip state can be maintained and in which the LU torque Tlu is rapidly increased, rather than being completely released. This allows the LU clutch 36 to be quickly returned to its engaged state as needed. Therefore, re-acceleration performance can be improved during high rotation FC control CNfc.

[0051] Furthermore, according to this embodiment, it is determined whether the engine speed Ne is approaching the FC rotation speed region ARfc based on whether the engine speed Ne is equal to or greater than a rotation speed that is a predetermined rotation speed lower than the FC rotation speed region ARfc, thereby appropriately executing the pre-FC slip control CNspbfc.

[0052] Furthermore, according to this embodiment, when the engine rotation speed Ne is likely to reach the FC rotation speed region ARfc, the predetermined rotation speed α is set to a larger value than when the engine rotation speed Ne is unlikely to reach the FC rotation speed region ARfc. This allows the execution of the high rotation speed FC control CNfc to be appropriately predicted.

[0053] Furthermore, according to this embodiment, the engine rotation speed Ne is likely to reach the FC rotation speed region ARfc when the accelerator opening θacc is large, when the automatic transmission 22 is in a low gear, or when the driving mode prioritizes power performance over fuel economy. This allows for a more appropriate prediction of when the high rotation speed FC control CNfc will be performed.

[0054] Furthermore, according to this embodiment, the pre-FC slip control CNspbfc is executed by the LU slip control CNlusp based on the FB control. Furthermore, when it is determined that the engine rotation speed Ne is within the FC rotation speed region ARfc, if the predetermined condition CDsp is not satisfied, the LU slip control CNlusp based on the FB control is maintained. On the other hand, when the predetermined condition CDsp is satisfied, the LU oil pressure PRlu is reduced more than when the LU slip control CNlusp based on the FB control is executed. As a result, the pre-FC slip control CNspbfc is appropriately executed when the execution of the high-speed FC control CNfc is expected. Furthermore, when the high-speed FC control CNfc is executed, the engaged state of the LU clutch 36 is reliably released. Additionally, the LU clutch 36 is not completely released, but is appropriately released within a range in which a slip state in which the LU torque Tlu is rapidly increased can be maintained.

[0055] Furthermore, according to this embodiment, the predetermined condition CDsp is a condition that the LU input torque Tinlu is equal to or greater than a predetermined input torque Tinluf. This appropriately suppresses a decrease in durability of the damper 38 and the like when the high-speed FC control CNfc is executed.

[0056] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0057] For example, in the above-described embodiment, the automatic transmission 22 may be a known belt-type continuously variable transmission, a known synchronous mesh parallel two-shaft automatic transmission, a known DCT (Dual Clutch Transmission), or the like.

[0058] In the above-described embodiment, the torque converter 20 may be replaced with a fluid-type power transmission device such as a fluid coupling that does not have a torque amplifying function. Alternatively, the fluid-type power transmission device may be replaced with a starting clutch. In this case, the starting clutch functions as a direct-coupled clutch that is provided in the power transmission path between the engine and the automatic transmission and connects the engine and the automatic transmission.

[0059] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0060] 10: Vehicle 12: Engine 14: Drive wheels 22: Automatic transmission 36: LU clutch (direct coupling clutch) 80: Electronic control unit (control unit) 82: Engine control unit 86: LU clutch control unit (direct coupling clutch control unit) 88: Rotation range determination unit

Claims

1. A control device for a vehicle including an engine, an automatic transmission provided in a power transmission path between the engine and drive wheels, and a direct coupling clutch provided in the power transmission path between the engine and the automatic transmission for connecting the engine and the automatic transmission, an engine control unit that stops fuel supply to the engine when the engine speed is in a predetermined high rotation speed range; a rotation region determination unit that determines whether the rotation speed of the engine is approaching the predetermined high rotation region and whether the rotation speed of the engine is within the predetermined high rotation region; a direct coupling clutch control unit that, when controlling the direct coupling clutch to an engaged state, controls the direct coupling clutch to a slip state if it is determined that the rotation speed of the engine is approaching the predetermined high rotation speed region, and, when it is determined that the rotation speed of the engine is in the predetermined high rotation speed region, reduces the engagement pressure of the direct coupling clutch based on predetermined conditions to a level that is lower than when it is determined that the rotation speed of the engine is approaching the predetermined high rotation speed region, within a range that allows the slip state in which the torque capacity of the direct coupling clutch can be quickly increased to be maintained; A vehicle control device comprising:

2. the rotation region determination unit determines whether the rotation speed of the engine is approaching the predetermined high rotation region based on whether the rotation speed of the engine is equal to or higher than a rotation speed that is lower than the predetermined high rotation region by a predetermined rotation speed, 2. The vehicle control device according to claim 1, wherein the rotation range determination unit sets the predetermined rotation speed to a larger value when the engine rotation speed is in a state where it is easy for the engine rotation speed to reach the predetermined high rotation range, compared to when the engine rotation speed is in a state where it is difficult for the engine rotation speed to reach the predetermined high rotation range.

3. 3. The vehicle control device according to claim 2, wherein the state in which the engine rotation speed is likely to reach the predetermined high rotation range is a state in which the accelerator operation amount is large, or a state in which the automatic transmission is in a gear position on the low vehicle speed side, or a state in which the driving mode is a driving mode that emphasizes power performance.

4. when it is determined that the rotational speed of the engine is approaching the predetermined high rotational speed region, the direct coupling clutch control unit executes slip control of the direct coupling clutch by feedback control that controls the direct coupling clutch to a slip state in accordance with an input torque to the direct coupling clutch so that an input / output rotational speed difference of the direct coupling clutch becomes a predetermined input / output rotational speed difference, 4. The vehicle control device according to claim 1, wherein the direct coupling clutch control unit, when it is determined that the engine rotation speed is within the predetermined high rotation range, maintains the slip control by the feedback control when the predetermined condition is not satisfied, while, when the predetermined condition is satisfied, reduces the engagement pressure of the direct coupling clutch compared to when the slip control by the feedback control is executed.

5. 5. The vehicle control device according to claim 4, wherein the predetermined condition is that the input torque is equal to or greater than a predetermined input torque.

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