Vehicle control device

Abstract

To suppress deterioration of drivability caused by difficulty in obtaining a torque amplification action of a torque converter at a start of a vehicle involved in turning on of an accelerator.SOLUTION: When a traveling state of a vehicle has entered a prescribed traveling state where a torque amplification action of a torque converter is difficult to obtain due to increase in an output rotational speed of the torque converter after a start of the vehicle involved in turning on of an accelerator, a required torque value for an engine is increased from a value corresponding to an amount of acceleration operation by a driver until the traveling state enters a second prescribed traveling state where acceleration feeling is less likely to deteriorate. So, a drop of vehicle acceleration due to torque converter characteristics involved in an increase in vehicle speed can be suppressed. Thus, at the start of the vehicle involved in turning on of the accelerator, deterioration of drivability caused by difficulty in obtaining a torque amplification action of the torque converter can be suppressed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle equipped with an engine and a torque converter. [Background technology]

[0002] There is a well-known control device for a vehicle that includes an engine and a power transmission device that has a torque converter connected to the engine and is provided in a power transmission path between the engine and drive wheels. For example, there is a vehicle control device described in Patent Document 1. Patent Document 1 discloses that the output of the engine is input to a torque converter, and then input from the torque converter to a continuously variable transmission, and that the output of the continuously variable transmission is transmitted to a differential gear or the like and distributed to the left and right drive wheels. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-188639 Summary of the Invention [Problem to be solved by the invention]

[0004] When the driver starts accelerating, i.e., when the accelerator pedal is depressed, the torque converter's output rotational speed increases as the vehicle speed increases. As the torque converter's differential rotational speed (= input rotational speed - output rotational speed) decreases, i.e., as the torque converter's speed ratio (= output rotational speed / input rotational speed) increases, the torque converter's torque ratio (= output torque / input torque) decreases, making it difficult for the torque converter to amplify its torque, resulting in a decrease in vehicle acceleration. Particularly in vehicles with a large gear ratio in the power transmission device downstream of the torque converter, which is used when starting, the torque converter's output rotational speed increases significantly as the vehicle speed increases, which makes it more likely for the torque converter's differential rotational speed to decrease, further hindering the torque converter's ability to amplify its torque. This can significantly reduce vehicle acceleration as the vehicle speed increases, potentially resulting in a deterioration in drivability.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can suppress deterioration of drivability caused by the torque amplification effect of the torque converter becoming difficult to obtain when the vehicle starts moving by pressing the accelerator. [Means for solving the problem]

[0006] The gist of the first invention is that a power transmission device includes: (a) an engine; and a torque converter connected to the engine and provided in a power transmission path between the engine and drive wheels; a lock-up clutch connecting an input and output rotary member of the torque converter; (b) after the vehicle starts moving in response to the start of an acceleration operation by the driver, when the running state of the vehicle reaches a predetermined running state in which it becomes difficult to obtain torque amplification effect in the torque converter as the output rotation speed of the torque converter increases, the control device increases the required torque value of the engine from a value corresponding to the acceleration operation amount by the driver until the running state reaches a second predetermined running state in which it becomes difficult to obtain a deterioration in acceleration feeling. (c) the torque increase control is not performed during a transition of execution of lockup clutch engagement control that switches the lockup clutch from a released state to an engaged state including a slip state. The reason is that. [Effects of the Invention]

[0007] According to the first aspect of the present invention, when the vehicle starts moving in response to accelerator depression and the vehicle travels in a predetermined driving state in which the torque converter's torque amplification effect becomes difficult to obtain as the torque converter's output rotational speed increases, the required engine torque value is increased from a value corresponding to the driver's acceleration operation amount until the vehicle reaches a second predetermined driving state in which the acceleration feel becomes difficult to deteriorate, thereby suppressing a drop in vehicle acceleration due to the torque converter's characteristics as the vehicle speed increases. Thus, when the vehicle starts moving in response to accelerator depression, it is possible to suppress a deterioration in drivability due to the torque converter's torque amplification effect becoming difficult to obtain. [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. 4 is a diagram showing an example of a predetermined relationship between a speed ratio and a torque ratio among torque converter characteristics. [Figure 3] This is a flowchart explaining the main control operations of the electronic control device, and is a flowchart explaining the control operations for suppressing deterioration of drivability due to the torque amplification effect of the torque converter becoming difficult to obtain when the vehicle starts with the accelerator depressed. [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. [Figure 5] FIG. 10 is a flowchart illustrating the main control operations of the electronic control device, and is a flowchart illustrating the control operations for suppressing deterioration of drivability due to difficulty in obtaining the torque amplification effect of the torque converter when the vehicle starts moving with the accelerator depressed, and is an embodiment different from that of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] In an embodiment of the present invention, the power transmission device includes, for example, an automatic transmission in a power transmission path between the torque converter and the drive wheels. The automatic transmission is, for example, a known planetary gear type automatic transmission, a known continuously variable transmission, or a known automatic transmission in which multiple power transmission paths are provided in parallel, such as a first power transmission path via a gear mechanism and a second power transmission path via a continuously variable transmission.

[0010] The continuously variable transmission is, for example, a continuously variable transmission in which a transfer element is wound between a primary pulley and a secondary pulley. The primary pulley, which is an input pulley, and the secondary pulley, which is an output pulley, each have, for example, a fixed sheave, a movable sheave, and a hydraulic actuator that applies thrust to change the groove width between the fixed sheave and the movable sheave. The vehicle is equipped with a hydraulic control circuit that independently controls pulley hydraulic pressure as hydraulic pressure supplied to the hydraulic actuator. This hydraulic control circuit may be configured to generate pulley hydraulic pressure as a result, for example, by controlling the flow rate of hydraulic oil to the hydraulic actuator. Such a hydraulic control circuit controls each of the thrust forces (= pulley hydraulic pressure × pressure-receiving area) at the primary pulley and the secondary pulley, thereby performing gear shift control to achieve a target gear shift while preventing slippage of the transfer element. The transmission element may be an endless, annular compression-type power transmission belt having an endless, annular hoop and elements, which are thick, plate-like blocks connected in the thickness direction along the hoop, or a tension-type power transmission belt comprising an endless, annular link chain in which the ends of alternately stacked link plates are connected to each other by connecting pins. The continuously variable transmission is a well-known belt-type continuously variable transmission. In a broad sense, the concept of this belt-type continuously variable transmission includes a chain-type continuously variable transmission.

[0011] Furthermore, the speed ratio (also called gear ratio) in the power transmission device, the continuously variable transmission, etc. is "rotational speed of the input side rotating member / rotational speed of the output side rotating member." For example, the speed ratio of the continuously variable transmission is "rotational speed of the primary pulley / rotational speed of the secondary pulley." The high side of the speed ratio is the high vehicle speed side where the speed ratio is small. The low side of the speed ratio is the low vehicle speed side where the speed ratio is large. For example, the lowest side speed ratio is the minimum vehicle speed side where the speed ratio is the lowest, and is the maximum speed ratio where the speed ratio is the largest.

[0012] The engine is a known internal combustion engine that generates power by burning fuel, such as a gasoline engine or a diesel engine, and the vehicle may be equipped with a rotary machine or the like in addition to the engine.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0014] Fig. 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 is equipped with an engine 12 that functions as a power source, drive wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

[0015] The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. An electronic control device 90 (described later) controls an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, and the like provided in the vehicle 10, thereby controlling the engine torque Te of the engine 12.

[0016] The power transmission device 16 includes a torque converter 20, an input shaft 22, a continuously variable transmission mechanism 24, a forward / reverse switching device 26, a gear mechanism 28, an output shaft 30, a countershaft 32, a reduction gear mechanism 34, a gear 36, a differential gear 38, and other components housed within a case 18, which is a non-rotating member attached to the vehicle body. The power transmission device 16 also includes left and right axles 40 connected to the differential gear 38. The input side of the torque converter 20 is connected to the engine 12. The input shaft 22 is integrally connected to a turbine shaft, which is the output rotating member of the torque converter 20, and is a rotating member that connects the output side of the torque converter 20 to the input side of the continuously variable transmission mechanism 24 and also connects the output side of the torque converter 20 to the input side of the forward / reverse switching device 26. The input side of the continuously variable transmission mechanism 24 is connected to the input shaft 22, and the output side is connected to the output shaft 30 via a second clutch C2, which will be described later. The gear mechanism 28 has an input side connected to the input shaft 22 via the forward / reverse switch 26 and an output side connected to the output shaft 30. The input shaft 22 is an input rotating member to which the power of the engine 12 is transmitted and is a common input rotating member for the continuously variable transmission mechanism 24 and the gear mechanism 28. The output shaft 30 is an output rotating member that outputs the power of the engine 12 to the drive wheels 14 and is a common output rotating member for the continuously variable transmission mechanism 24 and the gear mechanism 28. The continuously variable transmission mechanism 24 and the gear mechanism 28 are provided in parallel in a power transmission path between the input shaft 22 and the output shaft 30. The continuously variable transmission mechanism 24 and the gear mechanism 28 form an automatic transmission provided in a power transmission path between the torque converter 20 and the drive wheels 14. The reduction gear unit 34 is a reduction mechanism comprising a pair of gears that are provided on the output shaft 30 and the countershaft 32, respectively, and mesh with each other so as not to rotate relative to each other. The gear 36 is provided on the counter shaft 32 so as not to rotate relative to the counter shaft 32, and is connected to the input side of the differential gear 38. The power is also the same as driving force, torque, and force unless otherwise specified.

[0017] In the power transmission device 16 configured in this manner, the power output from the engine 12 is transmitted to the left and right drive wheels 14 via the torque converter 20, forward / reverse switch 26, gear mechanism 28, reduction gear device 34, differential gear 38, axles 40, etc. in this order. Alternatively, in the power transmission device 16, the power output from the engine 12 is transmitted to the left and right drive wheels 14 via the torque converter 20, continuously variable transmission 24, reduction gear device 34, differential gear 38, axles 40, etc. in this order.

[0018] The torque converter 20 includes a pump wheel 20p connected to the engine 12 and a turbine wheel 20t connected to an input shaft 22. The torque converter 20 is a fluid transmission device that transmits power from the engine 12 to the input shaft 22 via fluid. The torque converter 20 includes a lock-up clutch 20lu, which is a known direct-coupled clutch that connects the pump wheel 20p and the turbine wheel 20t, i.e., that connects the input and output rotary members of the torque converter 20.

[0019] The lockup clutch 20lu is a hydraulic friction engagement device constituted by, for example, a multi-plate or single-plate clutch. The lockup clutch 20lu switches its operating state, i.e., its control state, by changing the LU torque Tlu, which is the torque capacity of the lockup clutch 20lu, using the LU oil pressure PRlu, which is a regulated oil pressure supplied from a hydraulic control circuit 52 provided in the vehicle 10. The control states of the lockup clutch 20lu include a released state (also called a fully released state) in which the lockup clutch 20lu is released, a slip state in which the lockup clutch 20lu is engaged with slippage, and an engaged state (also called a fully engaged state) in which the lockup clutch 20lu is engaged.

[0020] The power transmission device 16 includes a plurality of power transmission paths arranged in parallel between the input shaft 22 and the output shaft 30, each capable of transmitting the power of the engine 12 from the input shaft 22 to the output shaft 30. The plurality of power transmission paths are a first power transmission path PT1 that transmits the power of the engine 12 from the input shaft 22 via a gear mechanism 28 to the output shaft 30 and then to the drive wheels 14, and a second power transmission path PT2 that transmits the power of the engine 12 from the input shaft 22 via a continuously variable transmission mechanism 24 to the output shaft 30 and then to the drive wheels 14.

[0021] In the power transmission device 16, the power transmission path that transmits power from the engine 12 to the drive wheels 14 is switched between a first power transmission path PT1 and a second power transmission path PT2 depending on the driving state of the vehicle 10. To this end, the power transmission device 16 includes a plurality of engagement devices that selectively form the first power transmission path PT1 and the second power transmission path PT2. The plurality of engagement devices include a first clutch C1, a first brake B1, and a second clutch C2. The first clutch C1 is provided in the first power transmission path PT1 and selectively connects and disconnects the first power transmission path PT1. When the vehicle is traveling forward, the first power transmission path PT1 is formed by engaging the first clutch C1 or the first brake B1. When the vehicle is traveling backward, the first power transmission path PT1 is formed by engaging the first clutch C1 or the first brake B1. The second clutch C2 is provided in the second power transmission path PT2 and is an engagement device that selectively connects and disconnects the second power transmission path PT2, and is an engagement device that forms the second power transmission path PT2. The second power transmission path PT2 is formed by engagement of the second clutch C2. The first clutch C1, the first brake B1, and the second clutch C2 are all known hydraulic wet-type friction engagement devices that are frictionally engaged by their respective hydraulic actuators. The first clutch C1 is a first friction engagement device for forward travel, the second clutch C2 is a second friction engagement device, and the first brake B1 is a first friction engagement device for reverse travel. As will be described later, the first clutch C1 and the first brake B1 are each one of the elements that make up the forward / reverse switching device 26. The control states of the first clutch C1, the first brake B1, and the second clutch C2 are switched by changing the torque capacity of the engagement devices using regulated hydraulic pressure supplied from the hydraulic control circuit 52.

[0022] The forward / reverse switching device 26 includes a double-pinion planetary gear set 26p, a first clutch C1, and a first brake B1. The planetary gear set 26p is a differential mechanism having three rotational elements: a carrier 26c as an input element, a sun gear 26s as an output element, and a ring gear 26r as a reaction element. The carrier 26c is connected to the input shaft 22. The ring gear 26r is selectively connected to the case 18 via a first brake B1. The sun gear 26s is connected to a small-diameter gear 60 that is provided around the input shaft 22 and coaxially rotatable relative to the input shaft 22. The carrier 26c and the sun gear 26s are selectively connected to each other via the first clutch C1.

[0023] The gear mechanism 28 includes a small-diameter gear 60, a gear mechanism counter shaft 62, and a large-diameter gear 64 that is coaxially mounted around the gear mechanism counter shaft 62 and non-rotatable relative to the gear mechanism counter shaft 62 and meshes with the small-diameter gear 60. The large-diameter gear 64 has a larger diameter than the small-diameter gear 60. The gear mechanism 28 also includes an idler gear 66 that is coaxially mounted around the gear mechanism counter shaft 62 and non-rotatable relative to the gear mechanism counter shaft 62, and an output gear 68 that is coaxially mounted around the output shaft 30 and non-rotatable relative to the output shaft 30 and meshes with the idler gear 66. The output gear 68 has a larger diameter than the idler gear 66. Therefore, the gear mechanism 28 forms one gear stage in the power transmission path between the input shaft 22 and the output shaft 30. The gear mechanism 28 is a gear mechanism having gear stages, i.e., a stepped gear mechanism with a fixed speed ratio (also referred to as gear ratio). The gear mechanism 28 further includes a dog clutch D1 disposed around the gear mechanism countershaft 62 between the large-diameter gear 64 and the idler gear 66 to selectively connect and disconnect the power transmission path therebetween. The dog clutch D1 is an engagement device that selectively connects and disconnects the first power transmission path PT1 and is an engagement device that forms the first power transmission path PT1 by being engaged together with the first clutch C1 or the first brake B1, and is included in the plurality of engagement devices. The dog clutch D1 is switched between an engaged state and a released state by actuating a hydraulic actuator 54 provided on the vehicle 10 with regulated hydraulic pressure supplied from the hydraulic control circuit 52.

[0024] The first power transmission path PT1 is formed by engaging both the dog clutch D1 and the first clutch C1 or the first brake B1, which is provided closer to the input shaft 22 than the dog clutch D1. In the first power transmission path PT1, a forward power transmission path is formed by engaging the first clutch C1 and the dog clutch D1, while a reverse power transmission path is formed by engaging the first brake B1 and the dog clutch D1. When the first power transmission path PT1 is formed, the power transmission device 16 is placed in a power transmittable state in which power from the engine 12 can be transmitted from the input shaft 22 to the output shaft 30 via the gear mechanism 28. On the other hand, when the first clutch C1 and the first brake B1 are both released, or when the dog clutch D1 is released, the first power transmission path PT1 is placed in a neutral state in which power transmission is disabled.

[0025] The continuously variable transmission mechanism 24 includes a primary shaft 70 that is coaxial with the input shaft 22 and integrally connected thereto, a primary pulley 72 with a variable effective diameter that is connected to the primary shaft 70, a secondary shaft 74 that is coaxial with the output shaft 30, a secondary pulley 76 with a variable effective diameter that is connected to the secondary shaft 74, and a transmission belt 78 that serves as a transmission element and is wound between the pulleys 72, 76. The continuously variable transmission mechanism 24 is a known belt-type continuously variable transmission in which power is transmitted via friction between the pulleys 72, 76 and the transmission belt 78, and transmits power from the engine 12 to the drive wheels 14. The friction force is also referred to as clamping pressure and is also referred to as belt clamping pressure. This belt clamping pressure is the belt torque capacity, which is the torque capacity of the transmission belt 78 in the continuously variable transmission mechanism 24.

[0026] The primary pulley 72 includes a fixed sheave 72a connected to the primary shaft 70, a movable sheave 72b that is not rotatable relative to the fixed sheave 72a about the axis of the primary shaft 70 but is movable in the axial direction, and a hydraulic actuator 72c that applies a primary thrust Wpri to the movable sheave 72b. The primary thrust Wpri is the thrust of the primary pulley 72 (=primary pressure Ppri × pressure-receiving area) that changes the V-groove width between the fixed sheave 72a and the movable sheave 72b. In other words, the primary thrust Wpri is the thrust of the primary pulley 72 that is applied by the hydraulic actuator 72c to clamp the transmission belt 78. The primary pressure Ppri is hydraulic pressure supplied to the hydraulic actuator 72c by the hydraulic control circuit 52 and is the pulley hydraulic pressure that generates the primary thrust Wpri. The secondary pulley 76 includes a fixed sheave 76a connected to the secondary shaft 74, a movable sheave 76b that is movable in the axial direction but not rotatable relative to the fixed sheave 76a around the axis of the secondary shaft 74, and a hydraulic actuator 76c that applies a secondary thrust Wsec to the movable sheave 76b. The secondary thrust Wsec is the thrust of the secondary pulley 76 (= secondary pressure Psec × pressure-receiving area) that changes the width of the V-groove between the fixed sheave 76a and the movable sheave 76b. In other words, the secondary thrust Wsec is the thrust of the secondary pulley 76 that is applied by the hydraulic actuator 76c to clamp the transmission belt 78. The secondary pressure Psec is hydraulic pressure supplied to the hydraulic actuator 76c by the hydraulic control circuit 52 and is the pulley hydraulic pressure that generates the secondary thrust Wsec.

[0027] In the continuously variable transmission mechanism 24, the primary pressure Ppri and the secondary pressure Psec are respectively regulated and controlled by a hydraulic control circuit 52 driven by an electronic control device 90 (described later), thereby controlling the primary thrust Wpri and the secondary thrust Wsec. As a result, in the continuously variable transmission mechanism 24, the V-groove width of each pulley 72, 76 is changed to change the loop diameter (= effective diameter) of the power transmission belt 78, changing the speed ratio γcvt (= primary rotation speed Npri / secondary rotation speed Nsec), and controlling the belt clamping pressure so as not to cause slippage of the power transmission belt 78. In other words, by controlling the primary thrust Wpri and the secondary thrust Wsec, belt slippage of the power transmission belt 78 is prevented, and the speed ratio γcvt of the continuously variable transmission mechanism 24 is set to the target speed ratio γcvttgt. The primary rotation speed Npri is the rotational speed of the primary shaft 70, which is the input rotational speed of the continuously variable transmission mechanism 24 and is equivalent to the rotational speed of the primary pulley 72. The primary rotation speed Npri is the same as the input shaft rotation speed Nin, which is the rotation speed of the input shaft 22, and is also the same as the turbine rotation speed, which is the rotation speed of the turbine shaft of the torque converter 20, i.e., the output rotation speed of the torque converter 20. The secondary rotation speed Nsec is the rotation speed of the secondary shaft 74, which is the output rotation speed of the continuously variable transmission mechanism 24, and is the same as the rotation speed of the secondary pulley 76.

[0028] In the continuously variable transmission mechanism 24, when the primary pressure Ppri is increased, the V-groove width of the primary pulley 72 is narrowed and the speed ratio γcvt is reduced. Reducing the speed ratio γcvt means that the continuously variable transmission mechanism 24 is upshifted. On the other hand, in the continuously variable transmission mechanism 24, when the primary pressure Ppri is decreased, the V-groove width of the primary pulley 72 is widened and the speed ratio γcvt is increased. Reducing the speed ratio γcvt means that the continuously variable transmission mechanism 24 is downshifted. In the continuously variable transmission mechanism 24, the lowest speed ratio γmax is formed when the V-groove width of the primary pulley 72 is at its maximum. In the continuously variable transmission mechanism 24, belt slippage is prevented by the primary thrust force Wpri and the secondary thrust force Wsec, and the target gear ratio γcvttgt is realized by the relationship between the primary thrust force Wpri and the secondary thrust force Wsec; the target gear ratio is not realized by only one thrust force. The gear ratio γcvt of the continuously variable transmission mechanism 24 is changed by changing the thrust ratio τ (=Wsec / Wpri), which is the ratio between the primary thrust force Wpri and the secondary thrust force Wsec, based on the relationship between the primary pressure Ppri and the secondary pressure Psec. The thrust ratio τ is the ratio of the secondary thrust force Wsec to the primary thrust force Wpri. For example, the larger the thrust ratio τ, the larger the gear ratio γcvt, i.e., the continuously variable transmission mechanism 24 is downshifted.

[0029] The output shaft 30 is disposed coaxially with the secondary shaft 74 so as to be rotatable relative to the secondary shaft 74. The second clutch C2 is provided in a power transmission path between the secondary pulley 76 and the output shaft 30. The second power transmission path PT2 is formed by engaging the second clutch C2. When the second power transmission path PT2 is formed, the power transmission device 16 is placed in a power transmittable state in which power from the engine 12 can be transmitted from the input shaft 22 to the output shaft 30 via the continuously variable transmission mechanism 24. On the other hand, when the second clutch C2 is released, the second power transmission path PT2 is placed in a neutral state. The speed ratio γcvt of the continuously variable transmission mechanism 24 corresponds to the speed ratio in the second power transmission path PT2.

[0030] In the power transmission device 16, the gear ratio EL of the gear mechanism 28, which is the gear ratio γgear (=input shaft rotation speed Nin / output shaft rotation speed Nout) in the first power transmission path PT1, is set to a value greater than the lowest gear ratio γmax of the continuously variable transmission mechanism 24, which is the maximum gear ratio in the second power transmission path PT2. In other words, the gear ratio EL is set to a gear ratio lower than the lowest gear ratio γmax. The gear ratio EL of the gear mechanism 28 corresponds to the first-speed gear ratio γ1 in the power transmission device 16, and the lowest gear ratio γmax of the continuously variable transmission mechanism 24 corresponds to the second-speed gear ratio γ2 in the power transmission device 16. In this way, the second power transmission path PT2 has a gear ratio higher than that of the first power transmission path PT1. The output shaft rotation speed Nout is the rotation speed of the output shaft 30.

[0031] The vehicle 10 can selectively travel in a gear traveling mode or a belt traveling mode. The gear traveling mode is a traveling mode in which the first power transmission path PT1 is formed in the power transmission device 16. The belt traveling mode is a traveling mode in which the second power transmission path PT2 is formed in the power transmission device 16. In the gear traveling mode, when forward traveling is possible, the first clutch C1 and the dog clutch D1 are engaged and the second clutch C2 and the first brake B1 are disengaged. In the gear traveling mode, when reverse traveling is possible, the first brake B1 and the dog clutch D1 are engaged and the second clutch C2 and the first clutch C1 are disengaged. In the belt traveling mode, the second clutch C2 is engaged and the first clutch C1 and the first brake B1 are disengaged. In this belt traveling mode, forward traveling is possible.

[0032] The gear driving mode is selected in a relatively low vehicle speed range, including when the vehicle is stopped. The belt driving mode is selected in a relatively high vehicle speed range, including a medium vehicle speed range. In the belt driving mode in the medium vehicle speed range of the belt driving mode, the mesh clutch D1 is engaged, while in the belt driving mode in the high vehicle speed range of the belt driving mode, the mesh clutch D1 is disengaged. The mesh clutch D1 is disengaged in the belt driving mode in the high vehicle speed range to, for example, eliminate drag of the gear mechanism 28 and the like during driving in the belt driving mode and to prevent components of the gear mechanism 28 and the planetary gear set 26p, such as the pinion, from rotating at high speeds in the high vehicle speed range. Preventing the gear mechanism 28 from rotating at high speeds prevents the differential rotation speed between the input side rotation speed and the output side rotation speed of the first clutch C1 from increasing, thereby improving the durability of the friction material of the first clutch C1.

[0033] The vehicle 10 is equipped with a mechanical oil pump 56. The oil pump 56 is connected to the pump impeller 20p and is driven to rotate 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 56 is supplied to the hydraulic control circuit 52. The hydraulic control circuit 52 supplies the LU hydraulic pressure PRlu, hydraulic pressure for controlling the speed change of the continuously variable transmission mechanism 24, hydraulic pressure for generating belt clamping pressure in the continuously variable transmission mechanism 24, hydraulic pressure for switching the control states of the first clutch C1, first brake B1, second clutch C2, and dog clutch D1, and the like, which are each adjusted based on the hydraulic oil OIL discharged by the oil pump 56.

[0034] The vehicle 10 further includes an electronic control device 90 as a controller including a control device for the vehicle 10. The electronic control device 90 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc., and the CPU executes various controls of the vehicle 10 by performing signal processing in accordance with a program stored in the ROM in advance while utilizing the temporary storage function of the RAM. The electronic control device 90 is configured to be divided into components for engine control, hydraulic control, etc. as necessary.

[0035] The electronic control device 90 is supplied with various signals based on detection values ​​from various sensors provided on the vehicle 10 (for example, an engine rotation speed sensor 80, an input shaft rotation speed sensor 81, a secondary rotation speed sensor 82, an output shaft rotation speed sensor 83, an accelerator opening sensor 84, a throttle valve opening sensor 85, a brake switch 86, a G sensor 87, an operation position sensor 88, etc.) (for example, an engine rotation speed Ne which is the rotation speed of the engine 12, an input shaft rotation speed Nin which is the same value as the primary rotation speed Npri, a secondary rotation speed Nsec, an output shaft rotation speed Nout corresponding to the vehicle speed V, an accelerator opening θacc which is the amount of acceleration operation by the driver indicating the magnitude of the driver's acceleration operation, i.e., the amount of accelerator operation, a throttle valve opening θth which is the opening of the electronic throttle valve, a brake-on signal Bon which is a signal indicating a state in which the brake pedal for operating the wheel brakes is being operated by the driver, a vehicle acceleration G which is the longitudinal acceleration of the vehicle 10, an operation position (=operation position) POSop which indicates the position to which a shift lever 89 provided on the vehicle 10 has been operated, etc.).

[0036] In addition, the electronic control device 90 outputs various command signals (for example, an engine control command signal Se for controlling the engine 12, a CVT hydraulic control command signal Scvt for controlling the speed changes and belt clamping pressure of the continuously variable transmission mechanism 24, a CBD hydraulic control command signal Scbd for controlling each of the first clutch C1, first brake B1, second clutch C2, and dog clutch D1, an LU hydraulic control command signal Slu for controlling the lock-up clutch 20lu, etc.) to each device (for example, the engine control device 50, the hydraulic control circuit 52, etc.) provided in the vehicle 10.

[0037] The shift lever 89 is a shift operation member operated by the driver to one of a plurality of operation positions POSop. The operation position POSop is a signal indicating the selected power transmission state of the power transmission device 16, and includes, for example, P, R, N, and D operation positions. The P operation position is a parking operation position that selects the P position of the power transmission device 16, in which the power transmission device 16 is in a neutral state and the output shaft 30 is mechanically fixed so as not to rotate. The neutral state of the power transmission device 16 is achieved, for example, by disengaging the first clutch C1, the first brake B1, and the second clutch C2. In other words, the neutral state of the power transmission device 16 is a state in which neither the first power transmission path PT1 nor the second power transmission path PT2 is formed. The R operation position is a reverse travel operation position that selects the R position of the power transmission device 16, which enables reverse travel in gear travel mode. The N operating position is a neutral operating position that selects the N position of the power transmission device 16, which places the power transmission device 16 in a neutral state. The D operating position is a forward running operating position that selects the D position of the power transmission device 16, which enables forward running in the gear running mode, or executes automatic speed change control of the continuously variable transmission mechanism 24 in the belt running mode, enabling forward running.

[0038] In order to realize various controls in the vehicle 10, the electronic control device 90 includes an engine control means, i.e., an engine control section 92, a gear change control means, i.e., a gear change control section 94, and a lock-up clutch control means, i.e., a lock-up clutch control section 96.

[0039] The engine control unit 92 calculates the amount of driving demanded by the driver for the vehicle 10, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand map. The driving demand map is a relationship for calculating the amount of driving demand that is determined and stored in advance experimentally or by design, i.e., a predetermined relationship. The amount of driving demand is, for example, the required driving force Frdem [N] at the drive wheels 14. The amount of driving demand can also be the required driving torque Trdem [Nm] at the drive wheels 14, the required output shaft torque at the output shaft 30, or the like.

[0040] The engine control unit 92 calculates the required value of the engine torque Te, i.e., the required engine torque Tedem, for obtaining the engine torque Te that realizes the required driving force Frdem, using, for example, the following predetermined equation (1). In the following equation (1), "Te" is the engine torque. "F" is the driving force Fr at the driving wheels 14. "rw" is the tire dynamic load radius of the driving wheels 14. "γ" is the actual speed ratio γcvt (=Npri / Nsec) of the continuously variable transmission mechanism 24 calculated by the transmission control unit 94 based on the primary rotation speed Npri and the secondary rotation speed Nsec in the belt driving mode, and is the predetermined speed ratio EL (=γgear) of the gear mechanism 28 in the gear driving mode. "i" is the reduction ratio of the reduction gear unit 34, the differential gear 38, etc. "t" is the torque ratio of the torque converter 20 (=turbine torque Tt / pump torque Tp). The turbine torque Tt is the torque output from the torque converter 20 and is equivalent to the torque input to the continuously variable transmission mechanism 24, i.e., the input shaft torque Tin. The pump torque Tp is the torque input to the torque converter 20 and is equivalent to the engine torque Te. The torque ratio t is a function of the speed ratio e (= turbine rotation speed / pump rotation speed) of the torque converter 20. The engine control unit 92 calculates the torque ratio t by applying the actual speed ratio e to a predetermined relationship between the speed ratio e and the torque ratio t, for example, as shown in FIG. 2. The engine control unit 92 calculates the actual speed ratio e (= Nin / Ne) based on the input shaft rotation speed Nin, which is the same as the turbine rotation speed, which is the rotation speed of the turbine wheel 20t, and the engine rotation speed Ne, which is the same as the pump rotation speed, which is the rotation speed of the pump wheel 20p. The engine control unit 92 calculates "Te" as the required engine torque Tedem by, for example, substituting the required driving force Frdem for "F." The engine control unit 92 calculates the requested engine torque Tedem according to the accelerator opening θacc, that is, the driver requested engine torque Tedemd, by performing a predetermined torque calculation using a predetermined engine torque calculation formula such as the following formula (1).

[0041] Te = (F × rw) / (γ × i × t) … (1)

[0042] The engine control unit 92 calculates a target throttle valve opening θthtgt at which the required engine torque Tedem is obtained, using a predetermined relationship, for example, an engine torque map. The engine control unit 92 sets the actual throttle valve opening θth to the target throttle valve opening θthtgt so that the required engine torque Tedem is obtained, and outputs an engine control command signal Se to the engine control device 50 to control an injection signal, an ignition timing signal, etc.

[0043] When the operating position POSop is in the P operating position or the N operating position while the vehicle is stopped, the shift control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to engage the dog clutch D1 in preparation for transition to the gear driving mode. When the operating position POSop is changed from the P operating position or the N operating position to the D operating position while the vehicle is stopped, the shift control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to engage the first clutch C1. This transition causes the driving mode to be shifted to the gear driving mode, which enables forward driving. When the operating position POSop is changed from the P operating position or the N operating position to the R operating position while the vehicle is stopped, the shift control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to engage the first brake B1. This transition causes the driving mode to be shifted to the gear driving mode, which enables reverse driving.

[0044] When the operating position POSop is the D operating position, the transmission control unit 94 executes switching control to switch between the gear driving mode and the belt driving mode. Specifically, the transmission control unit 94 determines whether a gear shift is necessary by applying the vehicle speed V and the accelerator opening θacc to upshift lines and downshift lines as a stepped transmission map that has a predetermined relationship and has a predetermined hysteresis for switching between the first gear corresponding to the gear ratio EL of the gear mechanism 28 in the gear driving mode and the second gear corresponding to the lowest gear ratio γmax of the continuously variable transmission mechanism 24 in the belt driving mode, and switches the driving mode based on the determination result.

[0045] When the shift control unit 94 determines an upshift while traveling in the gear traveling mode and switches to the belt traveling mode, it outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to perform a clutch-to-clutch shift that disengages the first clutch C1 and engages the second clutch C2 while the dog clutch D1 is in an engaged state. In this way, the shift control unit 94 performs an upshift of the power transmission device 16 that switches from the gear traveling mode to the belt traveling mode, i.e., a stepped upshift, by means of stepped transmission control that releases the first clutch C1 and engages the second clutch C2.

[0046] When the vehicle speed V increases in the belt driving mode after a stepped upshift, the shift control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to disengage the dog clutch D1. On the other hand, when the vehicle speed V decreases in the belt driving mode after disengaging the dog clutch D1, the shift control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to engage the dog clutch D1.

[0047] When determining a downshift while traveling in the belt driving mode and switching to the gear driving mode, the transmission control unit 94 outputs a CBD hydraulic control command signal Scbd to the hydraulic control circuit 52 to perform a clutch-to-clutch shift that switches the clutches so that the second clutch C2 is released and the first clutch C1 is engaged, while the dog clutch D1 is in an engaged state. In this way, the transmission control unit 94 performs a downshift of the power transmission device 16 that switches from the belt driving mode to the gear driving mode, i.e., a stepped downshift, by means of stepped speed change control that releases the second clutch C2 and engages the first clutch C1.

[0048] In the belt driving mode, the shift control unit 94 outputs a CVT hydraulic control command signal Scvt to the hydraulic control circuit 52 to control the primary pressure Ppri and the secondary pressure Psec so as to achieve the target speed ratio γcvttgt of the continuously variable transmission mechanism 24 while preventing belt slippage of the continuously variable transmission mechanism 24, thereby performing a gear shift of the continuously variable transmission mechanism 24.

[0049] Specifically, the shift control unit 94 calculates the target primary rotation speed Npritgt (=target input shaft rotation speed Nintgt) by applying the accelerator opening θacc and the vehicle speed V to, for example, a CVT shift map, which has a predetermined relationship. The shift control unit 94 calculates the target gear ratio γcvttgt (=Npritgt / Nsec) based on the target primary rotation speed Npritgt. The shift control unit 94 calculates the estimated engine torque Tee, which is an estimated value of the engine torque Te, by applying the throttle valve opening θth and the engine rotation speed Ne to, for example, the engine torque map. The shift control unit 94 calculates the estimated input shaft torque Tine (=Tee×torque ratio t), which is an estimated value of the input shaft torque Tin (=turbine torque Tt), based on the estimated engine torque Tee. The gear shift control unit 94 uses a thrust ratio map, which is a predetermined relationship, to calculate a thrust ratio τ for achieving the target gear ratio γcvttgt while preventing belt slippage, based on the target gear ratio γcvttgt and the estimated input shaft torque Tine. The gear shift control unit 94 calculates a target primary thrust Wpritgt and a target secondary thrust Wsectgt for achieving this thrust ratio τ. The gear shift control unit 94 converts the target primary thrust Wpritgt and the target secondary thrust Wsectgt into a target primary pressure Ppritgt (= Wpritgt / pressure-receiving area) and a target secondary pressure Psectgt (= Wsectgt / pressure-receiving area), respectively. The gear shift control unit 94 outputs a CVT hydraulic pressure control command signal Scvt to the hydraulic control circuit 52, which controls the primary pressure Ppri and the secondary pressure Psec so as to obtain the target primary pressure Ppritgt and the target secondary pressure Psectgt. For convenience, the thrust for maintaining a constant target speed ratio γcvttgt has been described in the above description of the speed change control of the continuously variable transmission mechanism 24. During the speed change transition of the continuously variable transmission mechanism 24, the thrust for achieving the target upshift or downshift is added to the thrust for maintaining the constant speed ratio.

[0050] The lockup clutch control unit 96 controls the control state of the lockup clutch 20lu. For example, the lockup clutch control unit 96 determines which region the lockup clutch 20lu is in by applying the vehicle speed V and accelerator pedal position θacc to a lockup region diagram, which has a predetermined relationship between a release region corresponding to a release state, a slip region corresponding to a slip state, and an engagement region corresponding to an engagement state, and outputs an LU hydraulic pressure control command signal Slu to the hydraulic control circuit 52 to supply the lockup clutch 20lu with an LU hydraulic pressure PRlu that achieves a control state corresponding to the determined region. By placing the lockup clutch 20lu in a release state, the torque converter 20 is placed in a torque converter state in which torque amplification is achieved. By placing the lockup clutch 20lu in an engagement state, the torque converter 20 is placed in a lockup state in which the pump wheel 20p and the turbine wheel 20t rotate integrally. When the lockup clutch 20lu is in a slip state, the lockup clutch 20lu is slipped so that the slip amount Nslp of the lockup clutch 20lu becomes the target slip amount Nslptgt. The slip amount Nslp is the differential rotational speed between the input and output of the lockup clutch 20lu (=Ne-Nin), which is the difference between the input and output rotational speeds. By placing the lockup clutch 20lu in a slip state, when the vehicle 10 is in a driving state, an increase in the engine rotational speed Ne is suppressed and muffled noise inside the vehicle is suppressed. On the other hand, when the vehicle 10 is in a driven state, the engine 12 is rotated at the target slip amount Nslptgt relative to the input shaft 22, thereby expanding the fuel cut region, for example.

[0051] Incidentally, the power transmission device 16 is equipped with a gear mechanism 28 to improve fuel economy, and the gear ratio EL is set lower than the lowest gear ratio γmax of the continuously variable transmission mechanism 24. When the vehicle 10 accelerates from a standstill, the gear ratio EL causes the increase in the input shaft rotation speed Nin relative to an increase in vehicle speed V to be greater than the lowest gear ratio γmax. Therefore, the speed ratio e (= Nin / Ne) of the torque converter 20 increases, which tends to decrease the torque ratio t of the torque converter 20 (see FIG. 2), and it may become difficult to obtain the torque amplification effect of the torque converter 20. This may result in a significant decrease in vehicle acceleration G relative to an increase in vehicle speed V, which may deteriorate drivability. It is desirable to suppress the drop in vehicle acceleration G due to torque converter characteristics as the vehicle speed V increases.

[0052] In response to this, when the driver starts accelerating, i.e., when the vehicle 10 starts moving in response to depression of the accelerator pedal, the engine control unit 92 executes torque increase control CTtup to increase the requested engine torque Tedem more than the driver requested engine torque Tedemd. However, at the beginning of the start of the vehicle 10, the increase in the input shaft rotation speed Nin is small relative to the increase in the engine rotation speed Ne, so the torque amplification effect of the torque converter 20 is likely to be obtained, and the vehicle acceleration G is likely to increase. Therefore, after the vehicle 10 starts moving, in a region where the input shaft rotation speed Nin is still low and where the vehicle acceleration G is likely to increase, it is not necessary to execute torque increase control CTtup. Furthermore, after the vehicle speed V increases in response to depression of the accelerator pedal, the acceleration feeling, i.e., the acceleration sensation, is unlikely to deteriorate even if the vehicle acceleration G does not increase. Therefore, after the vehicle 10 starts moving, in a region where the vehicle speed V increases and where the acceleration feeling is unlikely to deteriorate, i.e., where the input shaft rotation speed Nin increases, it is not necessary to execute torque increase control CTtup.

[0053] Therefore, when performing the torque increase control CTtup, if the running state of the vehicle 10 after the accelerator is depressed and the vehicle 10 starts moving, becomes a predetermined running state in which it becomes difficult to obtain the torque amplification effect of the torque converter 20 as the input shaft rotation speed Nin increases, the engine control unit 92 increases, for example, gradually increases (i.e., sweeps up), the requested engine torque Tedem from the driver requested engine torque Tedemd until the vehicle 10 enters a second predetermined running state in which the acceleration feeling is unlikely to deteriorate. In the torque increase control CTtup, the engine control unit 92 sweeps up the requested engine torque Tedem from the driver requested engine torque Tedemd, for example, at a predetermined gradient. When the running state of the vehicle 10 enters the second predetermined running state, the engine control unit 92 ends the sweep up of the requested engine torque Tedem, and thereafter sets the requested engine torque Tedem by, for example, adding the increase up to that point to the driver requested engine torque Tedemd.

[0054] The electronic control device 90 further includes a state determination means, that is, a state determination unit 98, in order to realize the function of torque increase control CTtup.

[0055] The state determination unit 98 determines whether the accelerator pedal is depressed. If the state determination unit 98 determines that the accelerator pedal is depressed, it determines whether the input shaft rotation speed Nin is within a predetermined range RNGf. The predetermined range RNGf is a predetermined range of the input shaft rotation speed Nin from a predetermined driving state until the driving state of the vehicle 10 changes to a second predetermined driving state. The state determination unit 98 determines whether the input shaft rotation speed Nin is within the predetermined range, for example, based on whether the input shaft rotation speed Nin is equal to or greater than a first predetermined rotation speed Ninf1 and less than a second predetermined rotation speed Ninf2. The first predetermined rotation speed Ninf1 is, for example, a predetermined threshold value for determining whether the driving state of the vehicle 10 has changed to a predetermined driving state. Because the torque increase control CTtup is deactivated at the beginning of acceleration of the vehicle 10 from a standstill, the first predetermined rotation speed Ninf1 corresponds to a lower limit value of the input shaft rotation speed Nin at which the torque increase control CTtup is implemented, i.e., started. The second predetermined rotation speed Ninf2 is, for example, a predetermined threshold value for determining whether the running state of the vehicle 10 has entered the second predetermined running state. Since the torque increase control CTtup is deactivated when the vehicle 10 is accelerating from a standstill, the second predetermined rotation speed Ninf2 corresponds to the upper limit of the input shaft rotation speed Nin at which the torque increase control CTtup is implemented, i.e., terminated.

[0056] The engine control unit 92 performs the torque increase control CTtup when the state determination unit 98 determines that the input shaft rotation speed Nin is within the predetermined range RNGf. On the other hand, the engine control unit 92 does not perform the torque increase control CTtup when the state determination unit 98 determines that the input shaft rotation speed Nin is not within the predetermined range RNGf.

[0057] When the lockup clutch engagement control CTlu, which switches the lockup clutch 20lu from a released state to an engaged state including a slip state, is being executed, it is preferable, in consideration of control accuracy, not to interfere with the torque increase control CTtup, which increases the engine torque Te input to the lockup clutch 20lu. In other words, it is preferable that the torque increase control CTtup be executed when the lockup clutch 20lu is in a released state, where the torque converter 20 can obtain a torque amplification effect.

[0058] If it is determined that the accelerator has been depressed, the state determination unit 98 determines whether or not the lock-up clutch engagement control CTlu has been started.

[0059] The engine control unit 92 performs the torque increase control CTtup when the state determination unit 98 determines that the input shaft rotation speed Nin is within the predetermined range RNGf and that the lockup clutch engagement control CTlu has not been started. On the other hand, the engine control unit 92 does not perform the torque increase control CTtup when the state determination unit 98 determines that the lockup clutch engagement control CTlu has been started.

[0060] Fig. 3 is a flowchart illustrating the main part of the control operation of the electronic control unit 90, which is a control operation for suppressing deterioration of drivability due to difficulty in obtaining the torque amplification effect of the torque converter 20 when the vehicle 10 starts moving due to accelerator depression, and is executed, for example, repeatedly. 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.

[0061] In FIG. 3 , first, in step S10 (hereinafter, the step will be omitted) corresponding to the function of the state determination unit 98, it is determined whether the accelerator has been pressed. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive, it is determined in S20, corresponding to the function of the state determination unit 98, whether the input shaft rotation speed Nin is within a predetermined range RNGf. If the determination in S20 is negative, this S20 is repeatedly executed. If the determination in S20 is positive, it is determined in S30, corresponding to the function of the state determination unit 98, whether the lock-up clutch engagement control CTlu has been initiated. If the determination in S30 is negative, the torque increase control CTtup is implemented in S40, corresponding to the function of the engine control unit 92. Next, in S50, corresponding to the function of the state determination unit 98, it is determined whether the input shaft rotation speed Nin is within a predetermined range RNGf. If the determination in S50 is positive, the routine returns to S30. If the determination in S30 above is positive, or if the determination in S50 above is negative, the torque increase control CTtup is not performed in S60, which corresponds to the function of the engine control unit 92. If the torque increase control CTtup is being performed, the torque increase control CTtup is terminated.

[0062] FIG. 4 is a diagram illustrating an example in which the accelerator is depressed while the vehicle 10 is stopped, and the vehicle 10 accelerates from a standstill with the lock-up clutch 20lu in a disengaged state. In FIG. 4, time t1 indicates the time when the accelerator is depressed. After the accelerator is depressed, the vehicle 10 accelerates from a standstill while the accelerator opening θacc is kept substantially constant, and the vehicle speed V increases. Specifically, the engine 12 is controlled to obtain a required engine torque Tedem corresponding to the accelerator opening θacc, i.e., a driver-requested engine torque Tedemd. The engine speed Ne is increased, and the input shaft rotation speed Nin is increased in accordance with the increase in vehicle speed V due to the acceleration of the vehicle 10 from a standstill (see time t1 and onward). In this embodiment, when the input shaft rotation speed Nin increases and enters the predetermined range RNGf, the torque increase control CTtup is initiated (see time t2). In the torque increase control CTtup, as shown by the solid line, the requested engine torque Tedem is swept up from the driver requested engine torque Tedemd (see time t2-t3). In the comparative example shown by the dashed line, the torque increase control CTtup is not performed, so the increase in engine speed Ne stagnates. This, combined with the increase in input shaft rotation speed Nin, makes it difficult for the torque converter 20 to achieve torque amplification, resulting in a significant decrease in vehicle acceleration G. In the present embodiment shown by the solid line, the execution of the torque increase control CTtup increases the engine rotation speed Ne, making it easier for the torque converter 20 to achieve torque amplification, thereby suppressing a decrease in vehicle acceleration G. In this embodiment, when the input shaft rotation speed Nin further increases and falls outside the predetermined range RNGf, the torque increase control CTtup is terminated (see time t3). In addition, in Figure 4, an increase in vehicle speed V causes an upshift from the first gear in gear driving mode to the second gear in belt driving mode, and the lockup clutch engagement control CTlu is performed to switch the lockup clutch 20lu to an engaged state (see time t3 and onwards).

[0063] As described above, according to this embodiment, after the vehicle 10 starts moving in response to accelerator depression, if the driving state of the vehicle 10 reaches a predetermined driving state in which it becomes difficult to obtain the torque amplification effect of the torque converter 20 as the input shaft rotation speed Nin increases, the requested engine torque Tedem is increased from the driver requested engine torque Tedemd until the vehicle reaches a second predetermined driving state in which it becomes difficult to obtain a deterioration in the acceleration feel, thereby suppressing a drop in the vehicle acceleration G due to the torque converter characteristics that accompanies an increase in the vehicle speed V. Therefore, when the vehicle 10 starts moving in response to accelerator depression, it is possible to suppress a deterioration in drivability that would be caused by it becoming difficult to obtain the torque amplification effect of the torque converter 20.

[0064] The power transmission device 16 is equipped with a gear mechanism 28 to improve fuel economy, and by implementing the torque increase control CTtup, it becomes easier to achieve both fuel economy and drivability.

[0065] Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments will be given the same reference numerals and the description thereof will be omitted. [Example]

[0066] In the first embodiment described above, whether the vehicle 10 has transitioned from a predetermined running state to a second predetermined running state is determined based on whether the input shaft rotation speed Nin is within the predetermined range RNGf. When the increase in the engine rotation speed Ne stagnates and the input shaft rotation speed Nin increases, the speed ratio e of the torque converter 20 increases, making it easier for the torque ratio t of the torque converter 20 to decrease. Therefore, in this embodiment, whether the vehicle 10 has transitioned from a predetermined running state to a second predetermined running state is determined based on whether the torque ratio t of the torque converter 20 decreases after the vehicle speed V increases due to accelerator depression.

[0067] When it is determined that the accelerator has been depressed, the state determination unit 98 determines whether the vehicle speed V has increased. The state determination unit 98 determines whether the vehicle speed V has increased, for example, based on whether the vehicle speed V has reached or exceeded a predetermined vehicle speed Vf. The predetermined vehicle speed Vf is, for example, a predetermined threshold value for determining the vehicle speed range at the beginning of the start of the vehicle 10 where the vehicle acceleration G is likely to increase.

[0068] When the state determination unit 98 determines that the vehicle speed V has increased, it determines whether or not the torque ratio t of the torque converter 20 has decreased. The state determination unit 98 determines whether or not the torque ratio t has decreased based on whether, for example, the rate of change α (= dt / dt) of the torque ratio t calculated based on the speed ratio e of the torque converter 20 is a negative value and the absolute value of the rate of change α is equal to or greater than a predetermined rate of change αf.

[0069] When the state determination unit 98 determines that the torque ratio t of the torque converter 20 is decreasing, the engine control unit 92 performs the torque increase control CTtup to compensate for the decrease in the torque ratio t. When the state determination unit 98 determines that the torque ratio t of the torque converter 20 is not decreasing, that is, when it determines that the decrease in the torque ratio t of the torque converter 20 has converged, the engine control unit 92 does not perform the torque increase control CTtup.

[0070] When the lockup clutch 20lu is switched from a released state to an engaged state including a slip state, the speed ratio e of the torque converter 20 is converged to "1" and the change in the torque ratio t of the torque converter 20 is converged. Therefore, determining whether the torque ratio t of the torque converter 20 is decreasing can be seen as including a determination whether the lockup clutch engagement control CTlu has been started.

[0071] 5 is a flowchart illustrating the main control operations of the electronic control device 90, which are executed repeatedly, for example, to suppress deterioration of drivability caused by difficulty in obtaining the torque amplification effect of the torque converter 20 when the vehicle 10 starts moving due to accelerator depression. The flowchart in FIG. 5 illustrates an embodiment different from the flowchart in FIG. 3 in the first embodiment described above.

[0072] In FIG. 5, first, in S10B, which corresponds to the function of the state determination unit 98, it is determined whether the accelerator has been depressed. If the determination in S10B is negative, this routine is terminated. If the determination in S10B is positive, in S20B, which corresponds to the function of the state determination unit 98, it is determined whether the vehicle speed V has increased. If the determination in S20B is negative, this S20B is repeatedly executed. If the determination in S20B is positive, in S30B, which corresponds to the function of the state determination unit 98, it is determined whether the torque ratio t of the torque converter 20 has decreased. If the determination in S30B is positive, in S40B, which corresponds to the function of the engine control unit 92, the torque increase control CTtup is performed. Next, the routine returns to S30B. If the determination in S30B is negative, in S50B, which corresponds to the function of the engine control unit 92, the torque increase control CTtup is not performed. If the torque increase control CTtup is currently being performed, the torque increase control CTtup is terminated.

[0073] As described above, according to this embodiment, similar to the first embodiment, it is possible to suppress a drop in vehicle acceleration G due to the torque converter characteristics that accompanies an increase in vehicle speed V. Therefore, when starting the vehicle 10 by pressing the accelerator pedal, it is possible to suppress a deterioration in drivability that would otherwise be caused by the torque amplification effect of the torque converter 20 becoming difficult to obtain. Furthermore, by performing the torque increase control CTtup, it becomes easier to achieve both fuel economy and drivability.

[0074] 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.

[0075] For example, in the first embodiment described above, in implementing the present invention, S30 in the flowchart of Fig. 3 does not necessarily have to be provided. In the flowchart of Fig. 3, if S30 is not provided, S40 is executed when the determination in S20 is affirmative, and if the determination in S50 is affirmative, the process returns to S40. Even in this case, a certain effect of suppressing a drop in vehicle acceleration G due to torque converter characteristics accompanying an increase in vehicle speed V can be obtained.

[0076] In the above-described embodiment, the vehicle 10 is equipped with the power transmission device 16 in which the continuously variable transmission mechanism 24 and the gear mechanism 28 are arranged in parallel in the power transmission path between the input shaft 22 and the output shaft 30, but this is not limited to this. The present invention can be applied to any vehicle equipped with an engine and a power transmission device having a torque converter connected to the engine and arranged in the power transmission path between the engine and the drive wheels. Also, although the torque converter 20 is equipped with the lock-up clutch 20lu, the lock-up clutch 20lu is not necessarily provided in order to implement the present invention.

[0077] 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]

[0078] 10: Vehicle 12: Engine 14: Drive wheel 16: Power transmission device 20: Torque converter 90: Electronic control device (control device)

Claims

[Claim 1] A control device for a vehicle including an engine, a power transmission device having a torque converter connected to the engine and provided in a power transmission path between the engine and drive wheels, and a lock-up clutch connecting input and output rotary members of the torque converter, When the vehicle starts moving in response to the start of an acceleration operation by the driver, and the running state of the vehicle reaches a predetermined running state in which it becomes difficult to obtain torque amplification effect in the torque converter as the output rotation speed of the torque converter increases, torque increase control is implemented to increase the required value of torque of the engine from a value corresponding to the acceleration operation amount by the driver until the vehicle reaches a second predetermined running state in which it becomes difficult to obtain deterioration in acceleration feeling, A vehicle control device, characterized in that the torque increase control is not performed during a transition of lock-up clutch engagement control that switches the lock-up clutch from a released state to an engaged state including a slip state.

Images