Vehicle control device

Abstract

To provide a vehicle control device capable of suppressing a reduction in durability of an engagement device and a continuously variable transmission, while also suppressing deterioration in energy efficiency.SOLUTION: When execution time of sweep control exceeds predetermined duration, backup control is performed, thereby suppressing heat generation in an engagement device. Additionally, clamping pressure increase control is executed before the initiation of the backup control, and the backup control is started after the completion of the clamping pressure increase control, thereby ensuring that sufficient clamping pressure to suppress or prevent slippage of a transmission element in the continuously variable transmission is secured before the engagement device is promptly engaged. Furthermore, the clamping pressure increase control is executed only before initiating the backup control, that is only when the execution time of the sweep control exceeds the predetermined duration, thereby reducing frequency of clamping pressure increases. Accordingly, reductions in durability of the engagement device and the continuously variable transmission can be suppressed while also suppressing deterioration in energy efficiency.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle provided with an engagement device in a power transmission path between a power source and a belt-type continuously variable transmission.

Background Art

[0002] A control device for a vehicle including a power source, a continuously variable transmission in which a transmission element is wound between a primary pulley and a secondary pulley that transmits the power of the power source to drive wheels, and an engagement device provided in a power transmission path between the power source and the continuously variable transmission is well known. For example, the drive control device for a vehicle described in Patent Document 1 is such a device. Patent Document 1 discloses suppressing the occurrence of belt slip by adding a correction amount calculated based on the difference between the inertia torque based on the target turbine rotation speed and the inertia torque based on the actual turbine rotation speed to the instructed clamping pressure of the belt-type continuously variable transmission.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when switching the engagement device from the released state to the engaged state, sweep control for gradually increasing the engagement pressure of the engagement device is performed. At this time, if the execution time of the sweep control exceeds a predetermined time, in order to prevent deterioration of durability due to heat generation associated with slip of the engagement device, backup control is performed to increase the engagement pressure faster than the sweep control and quickly bring the engagement device into the engaged state. However, when the engagement device is rapidly engaged, a large inertia torque is input to the continuously variable transmission, slippage of the transmission elements of the continuously variable transmission occurs, and there is a risk of deterioration of the durability of the continuously variable transmission. With respect to slippage of the transmission elements, if control for increasing the clamping pressure on the transmission elements is incorporated into the normal control, there is a risk of deterioration of energy efficiency or deterioration of the durability of the continuously variable transmission due to an increase in the load on the transmission elements.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a vehicle control device capable of suppressing deterioration of durability of an engagement device and a continuously variable transmission while suppressing deterioration of energy efficiency.

Means for Solving the Problem

[0006] The gist of the first invention is a control device for a vehicle comprising: (a) a power source, a continuously variable transmission having a transmission element wound between a primary pulley and a secondary pulley for transmitting the power of the power source to drive wheels, and an engagement device provided in a power transmission path between the power source and the continuously variable transmission; (b) a transmission control unit for controlling the clamping pressure on the transmission element in the continuously variable transmission; and (c) an engagement device control unit that performs a sweep control for gradually increasing the engagement pressure of the engagement device when switching the engagement device from a released state to an engaged state, and when the execution time of the sweep control exceeds a predetermined time, performs a backup control for increasing the engagement pressure faster than the sweep control to quickly bring the engagement device into the engaged state. (d) The transmission control unit performs a clamping pressure increase control for increasing the clamping pressure before the start of the backup control more than when the sweep control is executed. (e) When performing the backup control, the engagement device control unit starts the backup control after completion of the clamping pressure increase control.

Advantages of the Invention

[0007] According to the first invention, when the execution time of the sweep control exceeds a predetermined time, backup control is performed. Thereby, heat generation of the engagement device is suppressed. Further, before the start of the backup control, clamping pressure increase control is performed, and the backup control is started after completion of the clamping pressure increase control. Thereby, the clamping pressure for suppressing or preventing slippage of the transmission element of the continuously variable transmission can be ensured, and then the engagement device can be quickly engaged. Further, the clamping pressure increase control is performed only before the start of the backup control, that is, when the execution time of the sweep control exceeds a predetermined time. Thereby, the frequency of clamping pressure increase is reduced. Therefore, it is possible to suppress a deterioration in energy efficiency and suppress a decrease in durability of the engagement device and the continuously variable transmission.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0009] In an embodiment of the present invention, the transmission element is an endless annular compression transmission belt, or a tensile transmission belt constituting an endless annular link chain. The continuously variable transmission is a 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.

[0010] Further, the power source is a known internal combustion engine such as an engine. Also, the vehicle may be provided with a known rotary electric machine such as an electric motor in addition to or instead of this engine as the power source.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

EXAMPLE

[0012] FIG. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining 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 that functions as a power source, drive wheels 14, and a power transmission device 16 provided in the power transmission path between the engine 12 and the drive wheels 14.

[0013] The engine 12 is a known internal combustion engine, and by being controlled by an electronic control unit 90 described later, the engine torque Te, which is the torque of the engine 12, is controlled.

[0014] The power transmission device 16 includes, in a case 18, a torque converter 20, a turbine shaft 22, a forward / reverse switching device 24, an input shaft 26, a continuously variable transmission 28, an output shaft 30, a reduction gear mechanism 32, a differential gear 34, and the like. Further, the power transmission device 16 includes left and right drive shafts 36 and the like connected to the differential gear 34. The case 18 is a non-rotating member attached to the vehicle body. The torque converter 20 is a known fluid transmission device and includes a pump impeller 20p connected to the engine 12 and a turbine impeller 20t connected to the turbine shaft 22. The turbine shaft 22 is a rotating member that connects the output side of the torque converter 20 and the input side of the forward / reverse switching device 24. The input shaft 26 is a rotating member that connects the output side of the forward / reverse switching device 24 and the input side of the continuously variable transmission 28. The output shaft 30 is a rotating member that connects the output side of the continuously variable transmission 28 and the input side of the reduction gear mechanism 32. The reduction gear mechanism 32 has its output side connected to the differential gear 34.

[0015] The power transmission device 16 includes a mechanical oil pump 38 connected to the pump impeller 20p. The oil pump 38 is rotationally driven by the engine 12 to supply oil FLD, which is the source pressure of various operating hydraulic pressures, to a hydraulic control circuit 40 provided in the vehicle 10 (see FIG. 2 described later). The operating hydraulic pressure is the hydraulic pressure of the oil FLD for controlling the shift of the continuously variable transmission 28, controlling the belt clamping pressure in the continuously variable transmission 28, and switching the control states of the clutch C1 and the brake B1 described later. The control states of the clutch C1 and the like are operating states such as an engaged state, a slip state, and a released state.

[0016] The forward and reverse switching device 24 includes a double pinion type planetary gear device 24p, a clutch C1, and a brake B1. The planetary gear device 24p is a differential mechanism having three rotating elements: a sun gear 24s, a carrier 24c, and a ring gear 24r. The sun gear 24s is connected to the turbine shaft 22. The carrier 24c is connected to the input shaft 26. The ring gear 24r is selectively connected to the case 18 via the brake B1. The carrier 24c and the sun gear 24s are selectively connected via the clutch C1. Both the clutch C1 and the brake B1 are known hydraulic wet friction engagement devices that are frictionally engaged by their respective hydraulic actuators. The control state of the clutch C1 is switched by changing the clutch torque Tc1 by the clutch hydraulic pressure Pc1. The clutch hydraulic pressure Pc1 is the regulated operating hydraulic pressure supplied from the hydraulic control circuit 40 to the clutch C1. The clutch torque Tc1 is the torque capacity of the clutch C1. The control state of the brake B1 is switched by changing the brake torque Tb1 by the brake hydraulic pressure Pb1. The brake hydraulic pressure Pb1 is the regulated operating hydraulic pressure supplied from the hydraulic control circuit 40 to the brake B1. The brake torque Tb1 is the torque capacity of the brake B1.

[0017] The power transmission device 16 forms a forward power transmission path when the clutch C1 is engaged and the brake B1 is released. The power transmission device 16 forms a reverse power transmission path when the brake B1 is engaged and the clutch C1 is released. The power transmission device 16 is set to a neutral state in which power transmission is impossible when the clutch C1 is released and the brake B1 is released. The clutch C1 is a forward engagement device provided in the power transmission path between the engine 12 and the continuously variable transmission 28. The brake B1 is a reverse engagement device provided in the power transmission path between the engine 12 and the continuously variable transmission 28.

[0018] The continuously variable transmission 28 includes a primary pulley 50, a secondary pulley 52, and a transmission belt 54. The primary pulley 50 is an input-side pulley with a variable effective diameter connected to the input shaft 26. The secondary pulley 52 is an output-side pulley with a variable effective diameter connected to the output shaft 30. The transmission belt 54 is a transmission element wound between the primary pulley 50 and the secondary pulley 52. The continuously variable transmission 28 is a known belt-type continuously variable transmission in which power transmission is performed through the frictional force between each pulley 50, 52 and the transmission belt 54, and transmits the power of the engine 12 to the drive wheel 14 side. The frictional force is synonymous with the pressure with which each pulley 50, 52 sandwiches the transmission belt 54, that is, the sandwiching pressure on the transmission belt 54 in the continuously variable transmission 28, and is also referred to as the belt sandwiching pressure. This belt sandwiching pressure is synonymous with the torque capacity of the transmission belt 54 in the continuously variable transmission 28, that is, the belt torque capacity Tcvt of the continuously variable transmission 28. The power is synonymous with the driving force, torque, and force when not particularly distinguished.

[0019] The primary pulley 50 includes a fixed sheave 50a, a movable sheave 50b, and a hydraulic actuator 50c. The fixed sheave 50a is a sheave connected to the input shaft 26. The movable sheave 50b is provided relative to the fixed sheave 50a so as not to be relatively rotatable about the axis of the input shaft 26 and movable in the axial direction. The hydraulic actuator 50c is an actuator that applies a primary thrust Wpri for sandwiching the transmission belt 54 to the movable sheave 50b. The primary thrust Wpri is the thrust of the primary pulley 50 (= primary pressure Ppri × pressure receiving area) for changing the groove width between the fixed sheave 50a and the movable sheave 50b. The primary pressure Ppri is a regulated hydraulic pressure supplied from the hydraulic control circuit 40 to the hydraulic actuator 50c, and is the pulley hydraulic pressure that generates the primary thrust Wpri.

[0020] The secondary pulley 52 includes a fixed sheave 52a, a movable sheave 52b, and a hydraulic actuator 52c. The fixed sheave 52a is a sheave connected to the output shaft 30. The movable sheave 52b is provided relative to the fixed sheave 52a so as not to be relatively rotatable about the axis of the output shaft 30 and movable in the axial direction. The hydraulic actuator 52c is an actuator that applies a secondary thrust Wsec for sandwiching the transmission belt 54 to the movable sheave 52b. The secondary thrust Wsec is the thrust of the secondary pulley 52 (= secondary pressure Psec × pressure receiving area) for changing the groove width between the fixed sheave 52a and the movable sheave 52b. The secondary pressure Psec is a regulated hydraulic pressure supplied from the hydraulic control circuit 40 to the hydraulic actuator 52c, and is the pulley hydraulic pressure that generates the secondary thrust Wsec.

[0021] In the continuously variable transmission 28, the primary pressure Ppri and the secondary pressure Psec are respectively regulated and controlled by a hydraulic control circuit 40 driven by an electronic control unit 90 described later, whereby the primary thrust Wpri and the secondary thrust Wsec are respectively controlled. As a result, in the continuously variable transmission 28, the V-groove widths of the respective pulleys 50 and 52 are changed, and the wrap diameter (= effective diameter) of the transmission belt 54 is changed, so that the transmission ratio (also referred to as the gear ratio) γ (= input shaft rotational speed Nin / output shaft rotational speed Nout) is changed. In addition, in the continuously variable transmission 28, the belt clamping pressure is controlled so that belt slip, which is slip of the transmission belt 54, does not occur. That is, by controlling the primary thrust Wpri and the secondary thrust Wsec respectively, belt slip in the continuously variable transmission 28 is prevented while the transmission ratio γ of the continuously variable transmission 28 is set to the target transmission ratio γtgt. The input shaft rotational speed Nin is the rotational speed of the input shaft 26. Also, the output shaft rotational speed Nout is the rotational speed of the output shaft 30.

[0022] When the primary pressure Ppri of the continuously variable transmission 28 is increased, the V-groove width of the primary pulley 50 is narrowed, the transmission ratio γ is decreased, and an upshift is performed. On the other hand, when the primary pressure Ppri of the continuously variable transmission 28 is decreased, the V-groove width of the primary pulley 50 is widened, the transmission ratio γ is increased, and a downshift is performed. In the continuously variable transmission 28, belt slip is prevented by the primary thrust Wpri and the secondary thrust Wsec, and the target transmission ratio γtgt is achieved by the mutual relationship between the primary thrust Wpri and the secondary thrust Wsec. In the continuously variable transmission 28, neither the target shift nor the prevention of belt slip can be achieved by only one of the primary thrust Wpri and the secondary thrust Wsec. By changing the thrust ratio τ (= Wsec / Wpri), which is the value of the ratio between the primary thrust Wpri and the secondary thrust Wsec, due to the mutual relationship between the primary pressure Ppri and the secondary pressure Psec, the transmission ratio γ of the continuously variable transmission 28 is changed. The thrust ratio τ is the value of the ratio of the secondary thrust Wsec to the primary thrust Wpri.

[0023] The vehicle 10 further includes an electronic control unit 90 as a controller that includes a control device for the vehicle 10 related to the control of the engine 12, the continuously variable transmission 28, and the like. The electronic control unit 90 is configured to include a so-called microcomputer having, for example, a CPU, a RAM, a ROM, an input / output interface, and the like.

[0024] Various signals based on detection values by various sensors and the like provided in the vehicle 10 are respectively supplied to the electronic control unit 90. The various sensors and the like are, for example, an engine speed sensor 60, a turbine speed sensor 62, an input speed sensor 64, an output speed sensor 66, an accelerator opening sensor 68, a hydraulic pressure sensor 86 (see FIG. 2 described later), and the like. The various signals and the like are, for example, an engine speed Ne, a turbine speed Nt, an input shaft speed Nin, an output shaft speed Nout, an accelerator opening θacc, a secondary pressure Psec, and the like. The engine speed Ne is the rotational speed of the engine 12. The turbine speed Nt is the rotational speed of the turbine shaft 22. The input shaft speed Nin represents the input rotational speed of the continuously variable transmission 28, that is, the rotational speed of the primary pulley 50. The output shaft speed Nout is a rotational speed corresponding to the vehicle speed V, and represents the output rotational speed of the continuously variable transmission 28, that is, the rotational speed of the secondary pulley 52. The accelerator opening θacc is the driver's accelerator operation amount representing the magnitude of the driver's acceleration operation.

[0025] From the electronic control device 90, various command signals and the like are output to each device and the like provided in the vehicle 10. Each device and the like are, for example, the engine 12, the hydraulic control circuit 40, and the like. The various command signals and the like are, for example, the engine control command signal Se, the transmission control command signal Scvt, the engagement pressure control command signal Scb, and the like. The engine control command signal Se is a command signal for controlling the engine 12. The transmission control command signal Scvt is a command signal for controlling the shift of the continuously variable transmission 28, the belt clamping pressure, etc., and is a command signal for controlling each of the primary pressure Ppri and the secondary pressure Psec. The engagement pressure control command signal Scb is a command signal for controlling the control state of the engagement device CB (clutch C1, brake B1), and is a command signal for controlling the hydraulic pressure supplied to the engagement device CB, that is, the engagement pressure Pcb (clutch hydraulic pressure Pc1, brake hydraulic pressure Pb1).

[0026] Figure 2 is a diagram showing an example of a hydraulic system 70 that controls the operations related to the continuously variable transmission 28, the forward / backward switching device 24, etc., provided in the vehicle 10. In Figure 2, the hydraulic system 70 includes an oil pump 38, a hydraulic control circuit 40, an oil pan 72, a strainer 74, a discharge oil passage 76, and the like. The oil pump 38 sucks up the oil FLD returned to the oil pan 72 provided at the lower part of the case 18 from the strainer 74 and discharges it to the discharge oil passage 76. The discharge oil passage 76 is connected to an oil passage in the hydraulic control circuit 40, for example, the line pressure oil passage 78 through which the line pressure PL flows. The hydraulic control circuit 40 includes a line pressure oil passage 78, a regulator valve 80, a transmission control system 82, an engagement pressure control system 84, and the like. The regulator valve 80 regulates the line pressure PL using the oil FLD discharged from the oil pump 38.

[0027] The transmission control system 82 includes, for example, a control valve for regulating the primary pressure Ppri, a solenoid valve for operating the control valve, a control valve for regulating the secondary pressure Psec, a solenoid valve for operating the control valve, and the like. The transmission control system 82 controls the primary pressure Ppri and the secondary pressure Psec using, for example, the line pressure PL as the source pressure. The transmission control command signal Scvt is, for example, a command signal for driving a solenoid valve or the like included in the transmission control system 82.

[0028] The engagement pressure control system 84 includes, for example, a solenoid valve for regulating and outputting the clutch hydraulic pressure Pc1, a solenoid valve for regulating and outputting the brake hydraulic pressure Pb1, and the like. The engagement pressure control system 84 controls the clutch hydraulic pressure Pc1 and the brake hydraulic pressure Pb1 using, for example, the line pressure PL as the source pressure. The engagement pressure control command signal Scb is, for example, a command signal for driving a solenoid valve or the like included in the engagement pressure control system 84.

[0029] Returning to FIG. 1, the electronic control unit 90 includes an engine control unit 92, a transmission control unit 94, and an engagement device control unit 96 to realize various controls in the vehicle 10.

[0030] The engine control unit 92 calculates the driving requirement amount for the vehicle 10 by the driver by applying the accelerator opening θacc and the vehicle speed V to a driving requirement amount map obtained experimentally or designed in advance, that is, a predetermined map. The driving requirement amount is, for example, the required driving torque Trdem [Nm] at the driving wheels 14, the required driving force Frdem [N], and the like. The engine control unit 92 outputs an engine control command signal Se to the engine 12 to control the engine 12 so as to obtain an engine torque Te that realizes the required driving torque Trdem, taking into account transmission losses, accessory loads, the transmission ratio γ of the continuously variable transmission 28, and the like.

[0031] The transmission control unit 94 controls the transmission ratio γ and the belt clamping pressure of the continuously variable transmission 28. For example, the transmission control unit 94 outputs a transmission control command signal Scvt for controlling the primary pressure Ppri and the secondary pressure Psec so as to achieve the target transmission ratio γtgt of the continuously variable transmission 28 while preventing belt slip in the continuously variable transmission 28 to the hydraulic control circuit 40. For example, the transmission control unit 94 sets an indicated pressure, which is a hydraulic indicated value corresponding to each value of the primary pressure Ppri and the secondary pressure Psec, in order to obtain the target shift operation and the target belt clamping pressure of the continuously variable transmission 28. The transmission control unit 94 outputs a drive current or a drive voltage corresponding to the set indicated pressure to a solenoid valve or the like in the transmission control system 82.

[0032] The engagement device control unit 96 controls the control state of the engagement device CB. For example, the engagement device control unit 96 sets an indicated pressure, which is a hydraulic indicated value corresponding to the value of the engagement pressure Pcb, for controlling the control state of the engagement device CB. The engagement device control unit 96 outputs a drive current or a drive voltage corresponding to the set indicated pressure to a solenoid valve or the like in the engagement pressure control system 84.

[0033] FIG. 3 is a diagram showing an example of the commanded pressure of the engagement pressure Pcb in the control for switching the engagement device CB from the released state to the engaged state, i.e., the engagement control. In FIG. 3, the time point t1 indicates the time when the engagement control of the engagement device CB is started. In the engagement control, first, the packing control is performed. The packing control is a control for setting the engagement device CB to a packed completion state in which the pack clearance in the friction plate or the like of the engagement device CB is packed. The packed completion state of the engagement device CB is a state in which the engagement device CB starts to have a torque capacity if the engagement pressure Pcb is increased from that state. In the packing control, first, quick apply (=QA) is executed (refer to the time point t1 - t2), and then the constant pressure standby for packing is executed (refer to the time point t2 - t3). After a predetermined quick apply time and a constant pressure standby time, which are the times required for the packing control from the start point of the packing control, the sweep control is executed (refer to the time point t3 - t4). In the sweep control, a sweep up in which the commanded pressure is gradually increased is executed in order to suppress the engagement shock or the like. Then, for example, when the completion of synchronization of the engagement device CB is determined based on the differential rotational speed ΔNcb in the engagement device CB, the end control for quickly increasing the commanded pressure toward the full engagement commanded pressure is performed (refer to the time point t4 - t5). The full engagement commanded pressure is the commanded pressure for connecting the input and output rotating members of the engagement device CB to bring the engagement device CB into the full engagement state, that is, the commanded pressure for directly connecting the engagement device CB. The differential rotational speed ΔNcb in the engagement device CB is the rotational speed difference between the input side rotating member and the output side rotating member of the engagement device CB. For example, the differential rotational speed ΔNc1 in the clutch C1 is the rotational speed difference (=Nt - Nin) between the turbine rotational speed Nt and the input shaft rotational speed Nin. When the commanded pressure is set to the full engagement commanded pressure, the engagement control is completed (refer to the time point t5), and the full engagement commanded pressure is maintained (refer to after the time point t5). Thus, when switching the engagement device CB from the released state to the engaged state, the engagement device control unit 96 performs a sweep control in which the engagement pressure Pcb of the engagement device CB is gradually increased.

[0034] On the other hand, in the engagement control of the engagement device CB, for example, when a malfunction occurs in the engagement device CB or the hydraulic system 70, resulting in a poor engagement where the engagement time is longer than expected, there is a concern about a decrease in durability due to heat generation of the engagement device CB. Therefore, when a variation in the turbine rotational speed Nt occurs in the engagement control, for example, after the start of sweep control, and a predetermined time TMf elapses before the determination of synchronization completion, backup control is performed to force the command pressure to the full engagement command pressure (see the dashed line in Fig. 3, at time t6). In this way, when switching the engagement device CB from the released state to the engaged state, the engagement device control unit 96 performs backup control when the execution time of the sweep control exceeds the predetermined time TMf. The backup control is a control that increases the engagement pressure Pcb faster than the sweep control and promptly brings the engagement device CB into the engaged state. The predetermined time TMf is, for example, a threshold value predetermined as the execution time of the sweep control where there is a concern about a decrease in durability due to heat generation of the engagement device CB, and is a predetermined threshold value for determining that a poor engagement of the engagement device CB has occurred.

[0035] By the way, when backup control is performed in the engagement control of the engagement device CB, there is a possibility that an inertia torque accompanying a decrease in the engine rotational speed Ne may occur when the engagement device CB is engaged. Then, when that inertia torque is input to the input side of the continuously variable transmission 28, there is a possibility that belt slip of the continuously variable transmission 28 may occur. On the other hand, as normal control, if the belt clamping pressure of the continuously variable transmission 28 is always increased, there is a possibility that the energy efficiency may deteriorate or the durability of the continuously variable transmission 28 may decrease due to an increased load on the transmission belt 54. Or, when backup control is performed in the engagement control of the engagement device CB, there is a concern that the engagement shock may increase depending on the magnitude of the differential rotational speed ΔNcb in the engagement device CB.

[0036] Therefore, the transmission control unit 94 increases the belt clamping pressure of the continuously variable transmission 28 only when backup control is performed in the engagement control of the engagement device CB. In addition, the engagement device control unit 96 performs backup control in a state where the belt clamping pressure has been increased by the transmission control unit 94.

[0037] That is, before the start of the backup control in the engagement control of the engagement device CB by the engagement device control unit 96, the transmission control unit 94 performs a nip pressure increase control for increasing the belt nip pressure of the continuously variable transmission 28 more than that during the execution of the sweep control in the engagement control. In addition, when performing the backup control in the engagement control of the engagement device CB, the engagement device control unit 96 starts the backup control after the completion of the nip pressure increase control by the transmission control unit 94.

[0038] When performing the nip pressure increase control, the transmission control unit 94 temporarily raises the belt nip pressure above the current value. The temporarily high belt nip pressure is, for example, a predetermined nip pressure higher than that during the execution of the sweep control. The predetermined nip pressure is, for example, a predetermined belt nip pressure for preventing or suppressing the occurrence of belt slip with respect to the inertia torque input to the input side of the continuously variable transmission 28. When performing the nip pressure increase control, the transmission control unit 94 sets the instruction value of the belt nip pressure, that is, the instruction pressures of the primary pressure Ppri and the secondary pressure Psec, as, for example, a transmission control command signal Scvt for making the actual value of the belt nip pressure, that is, the actual belt nip pressure, equal to or higher than the predetermined nip pressure.

[0039] When increasing the belt clamping pressure, that is, when increasing the primary pressure Ppri and the secondary pressure Psec, there is a concern that the flow rate of the oil FLD is insufficient. In contrast, when performing the clamping pressure increase control, the transmission control unit 94 temporarily increases the rotational speed of the oil pump 38 to be higher than the current rotational speed. The temporarily high rotational speed of the oil pump 38 is, for example, a predetermined rotational speed higher than when performing the sweep control. The predetermined rotational speed is, for example, a predetermined rotational speed that can ensure the flow rate of the oil FLD corresponding to the increased belt clamping pressure. When performing the clamping pressure increase control, the transmission control unit 94 outputs a command to set the rotational speed of the oil pump 38 to the predetermined rotational speed to the engine control unit 92. When performing the clamping pressure increase control, the engine control unit 92 sets the indicated value of the rotational speed of the oil pump 38, that is, the indicated value of the engine rotational speed Ne, to, for example, the engine control command signal Se for setting the engine rotational speed Ne to the predetermined rotational speed.

[0040] The transmission control unit 94 determines whether the clamping pressure increase control is completed based on whether the actual belt clamping pressure is equal to or higher than the predetermined clamping pressure. The transmission control unit 94 determines whether the actual belt clamping pressure is equal to or higher than the predetermined clamping pressure based on whether the value of the secondary pressure Psec detected by the hydraulic pressure sensor 86 is equal to or higher than the predetermined secondary pressure Psecf. The predetermined secondary pressure Psecf is a predetermined threshold value for determining that the actual belt clamping pressure is equal to or higher than the predetermined clamping pressure. Incidentally, since the thrust ratio τ is changed by the mutual relationship between the primary pressure Ppri and the secondary pressure Psec, and the gear ratio γ and the belt clamping pressure are changed, it is possible to calculate the estimated value of the actual belt clamping pressure from the detected value of the secondary pressure Psec.

[0041] In the engagement control of the engagement device CB, if the amount of heat generation Qcb in the engagement device CB is small even if an engagement failure of the engagement device CB occurs, the durability of the engagement device CB is unlikely to decrease, so backup control does not have to be performed and sweep control may be continued.

[0042] When the execution time of the sweep control exceeds the predetermined time TMf, if the heat generation amount Qcb in the engagement device CB is less than the predetermined heat generation amount Qcbf, the engagement device control unit 96 continues the sweep control. On the other hand, when the execution time of the sweep control exceeds the predetermined time TMf and the heat generation amount Qcb in the engagement device CB is equal to or greater than the predetermined heat generation amount Qcbf, the backup control is performed. The predetermined heat generation amount Qcbf is a predetermined threshold value for determining, for example, that the heat generation amount Qcb is close to the limit that reduces the durability of the engagement device CB, that is, it is necessary to perform the backup control. The engagement device control unit 96 calculates the heat generation amount Qcb based on, for example, the differential rotation speed ΔNcb, the engagement pressure Pcb, and the execution time of the sweep control in the engagement device CB.

[0043] In the engagement control of the engagement device CB, even if an engagement failure of the engagement device CB occurs, if the differential rotation speed ΔNcb in the engagement device CB at that time is small, it is difficult for the heat generation amount Qcb in the engagement device CB to increase even if the sweep control is continued. The magnitude of the differential rotation speed ΔNcb is synonymous with the magnitude of the change in the turbine rotation speed Nt (here, the engine rotation speed Ne is also synonymous) due to the engagement of the engagement device CB.

[0044] When the execution time of the sweep control exceeds the predetermined time TMf, if the differential rotation speed ΔNcb in the engagement device CB is less than the predetermined differential rotation speed ΔNcbf, the engagement device control unit 96 continues the sweep control. On the other hand, when the execution time of the sweep control exceeds the predetermined time TMf and the differential rotation speed ΔNcb is equal to or greater than the predetermined differential rotation speed ΔNcbf, the backup control is performed. The predetermined differential rotation speed ΔNcbf is a predetermined threshold value for determining, for example, that the differential rotation speed ΔNcb is so small that it is difficult for the heat generation amount Qcb to increase even if the sweep control is continued.

[0045] FIG. 4 is a flowchart for explaining the main part of the control operation of the electronic control device 90, and is a flowchart for explaining the control operation for suppressing a decrease in the durability of the engagement device CB and the continuously variable transmission 28 while suppressing a deterioration in energy efficiency, and is repeatedly executed, for example.

[0046] In FIG. 4, first, in S10 corresponding to the function of the engagement device control unit 96, it is determined whether or not the execution time of the sweep control in the engagement control of the engagement device CB exceeds a predetermined time TMf. That is, it is determined whether or not an engagement failure of the engagement device CB has occurred. If the determination in this S10 is negative, this routine is terminated. If the determination in this S10 is affirmative, in S20 corresponding to the function of the engagement device control unit 96, it is determined whether or not the differential rotation speed ΔNcb in the engagement device CB is equal to or greater than a predetermined differential rotation speed ΔNcbf. That is, it is determined whether or not the change in the turbine rotation speed Nt due to the engagement of the engagement device CB when the backup control is performed is large. If the determination in this S20 is affirmative, in S30 corresponding to the function of the engagement device control unit 96, it is determined whether or not the heat generation amount Qcb in the engagement device CB is equal to or greater than a predetermined heat generation amount Qcbf. That is, it is determined whether or not the heat generation amount Qcb is close to the limit. If the determination in the above S20 is negative, or if the determination in the above S30 is negative, in S40 corresponding to the function of the engagement device control unit 96, the sweep control is continued. If the determination in the above S30 is affirmative, in S50 corresponding to the function of the transmission control unit 94, the indicated value of the rotation speed of the oil pump 38 is increased and the indicated value of the belt clamping pressure is increased, so that the clamping pressure increase control is performed. Next, in S60 corresponding to the function of the transmission control unit 94, it is determined whether or not the actual belt clamping pressure is equal to or greater than a predetermined clamping pressure. That is, it is determined whether or not the clamping pressure increase control has been completed. If the determination in this S60 is negative, this S60 is repeatedly executed. If the determination in this S60 is affirmative, in S70 corresponding to the function of the engagement device control unit 96, the backup control is performed.

[0047] In the flowchart of FIG. 4, S60 was repeated until the actual belt clamping pressure became equal to or higher than the predetermined clamping pressure. After waiting for a certain period until the actual belt clamping pressure becomes equal to or higher than the predetermined clamping pressure, control may be performed to accelerate the increase in the actual belt clamping pressure. That is, when the actual belt clamping pressure cannot be increased to be equal to or higher than the predetermined clamping pressure from the time when the rotational speed of the oil pump 38 is temporarily increased until a predetermined waiting time elapses, the transmission control unit 94 further increases the rotational speed of the oil pump 38. The transmission control unit 94 makes the indicated value of the rotational speed of the oil pump 38 higher by a predetermined increased rotational speed than the indicated value that was temporarily increased. The predetermined waiting time is a threshold value that is predetermined, for example, as the time to wait from when the indicated value of the rotational speed of the oil pump 38 is increased until the actual belt clamping pressure becomes equal to or higher than the predetermined clamping pressure in consideration of the delay in the increase in the actual belt clamping pressure. The predetermined increased rotational speed is, for example, a predetermined increase generation that can further ensure the flow rate of the oil FLD.

[0048] FIG. 5 is a flowchart for explaining the main part of the control operation of the electronic control device 90 in the same manner as the flowchart of FIG. 4. The flowchart of FIG. 5 mainly shows the parts different from the flowchart of FIG. 4. The different parts will be mainly described.

[0049] In FIG. 5, when the determination in S60 is negative, in S63 corresponding to the function of the transmission control unit 94, it is determined whether or not a predetermined waiting time has elapsed since the time when the rotational speed of the oil pump 38 was temporarily increased. When the determination in S63 is affirmative, in S65 corresponding to the function of the transmission control unit 94, the indicated value of the rotational speed of the oil pump 38 is further increased. When the determination in S63 is negative, or after S65, S60 is executed. Note that the time when the rotational speed of the oil pump 38 was temporarily increased in S63 includes the time when the indicated value of the rotational speed of the oil pump 38 was further increased. Also, in S65, the indicated value of the belt clamping pressure may be further increased.

[0050] Alternatively, in the flowchart of FIG. 4, although S60 is repeated until the actual belt clamping pressure becomes equal to or greater than the predetermined clamping pressure, backup control may be forcibly performed when the time runs out. That is, the engagement device control unit 96 starts backup control when the actual belt clamping pressure does not become equal to or greater than the predetermined clamping pressure by the time the time runs out in the clamping pressure increasing control. The time when the time runs out is a threshold value predetermined as the time to wait for the completion of the clamping pressure increasing control.

[0051] FIG. 6 is a flowchart for explaining the main part of the control operation of the electronic control device 90 in the same manner as the flowchart of FIG. 4. The flowchart of FIG. 6 mainly shows the parts different from the flowchart of FIG. 4. The different parts will be mainly explained.

[0052] In FIG. 6, when the determination of S60 is negative, it is determined whether the time has run out in S68 corresponding to the function of the transmission control unit 94. When the determination of S68 is negative, the process returns to S60. When the determination of S60 is positive, or when the determination of S68 is positive, S70 is executed.

[0053] As described above, according to the present embodiment, when the execution time of the sweep control exceeds the predetermined time TMf, backup control is performed. Thereby, heat generation of the engagement device CB is suppressed. Further, the clamping pressure increasing control is performed before the start of the backup control, and the backup control is started after the completion of the clamping pressure increasing control. Thereby, the belt clamping pressure for suppressing or preventing the belt slip of the continuously variable transmission 28 can be ensured, and then the engagement device CB can be quickly engaged. Further, the clamping pressure increasing control is performed only before the start of the backup control, that is, when the execution time of the sweep control exceeds the predetermined time TMf. Thereby, the frequency of increase in the belt clamping pressure is reduced. Therefore, it is possible to suppress a decrease in the durability of the engagement device CB and the continuously variable transmission 28 while suppressing a deterioration in energy efficiency.

[0054] Also, according to this embodiment, when the execution time of the sweep control exceeds a predetermined time TMf and the calorific value Qcb is less than a predetermined calorific value Qcbf, the sweep control is continued. Thereby, when there is a margin in the calorific value Qcb, the engagement device CB is engaged slowly, so that engagement shock and belt slip are suppressed or prevented. Also, the frequency of increase in the belt clamping pressure is reduced. On the other hand, when the execution time of the sweep control exceeds a predetermined time TMf and the calorific value Qcb is equal to or greater than the predetermined calorific value Qcbf, backup control is performed. Thereby, the backup control is performed only when there is no margin in the calorific value Qcb.

[0055] Also, according to this embodiment, when the execution time of the sweep control exceeds a predetermined time TMf and the differential rotational speed ΔNcb is less than a predetermined differential rotational speed ΔNcbf, the sweep control is continued. Thereby, when the calorific value Qcb is difficult to increase, the engagement device CB is engaged slowly, so that engagement shock and belt slip are suppressed or prevented. Also, the frequency of increase in the belt clamping pressure is reduced. On the other hand, when the execution time of the sweep control exceeds a predetermined time TMf and the differential rotational speed ΔNcb is equal to or greater than the predetermined differential rotational speed ΔNcbf, backup control is performed. Thereby, the backup control is performed only when the calorific value Qcb is likely to increase.

[0056] Also, according to this embodiment, when the clamping pressure increase control is performed, the rotational speed of the oil pump is temporarily increased higher than the current rotational speed. Thereby, the increase in the actual belt clamping pressure is promoted. Also, it becomes easier to secure the flow rate of the oil FLD corresponding to the increase in the belt clamping pressure. Also, since the frequency of increase in the belt clamping pressure is reduced, the frequency at which the rotational speed of the oil pump is temporarily increased is also reduced.

[0057] Further, according to the present embodiment, when the actual belt clamping pressure cannot be increased to a predetermined clamping pressure or more from the time when the rotational speed of the oil pump 38 is temporarily increased until a predetermined waiting time elapses, the rotational speed of the oil pump 38 is further increased. Thereby, the increase in the actual belt clamping pressure is further promoted. Also, it becomes easier to ensure the flow rate of the oil FLD for coping with the increase in the belt clamping pressure.

[0058] As described above, the embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is also applicable in other aspects.

[0059] For example, in the above-described embodiment, the engagement device CB (clutch C1, brake B1) is exemplified as the engagement device provided in the power transmission path between the power source and the continuously variable transmission, but the present invention is not limited to this aspect. For example, the engagement device provided in the power transmission path between the power source and the continuously variable transmission may be a so-called starting clutch that is switched from the released state to the engaged state while increasing the torque capacity while being in a slip state at the start of the vehicle. Further, instead of or in addition to the oil pump 38, an electric oil pump may be provided.

[0060] Note that the above description is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Description of Reference Numerals

[0061] 10: Vehicle 12: Engine (power source) 14: Drive wheel 28: Continuously variable transmission 38: Oil pump 50: Primary pulley 50a: Fixed sheave 50b: Movable sheave 50c: Hydraulic actuator 52: Secondary pulley 52a: Fixed sheave 52b: Movable sheave 52c: Hydraulic actuator 54: Transmission belt (transmission element) 90: Electronic control unit (control unit) 94: Transmission control unit 96: Engagement device control unit B1: Brake (engagement device) C1: Clutch (engagement device) CB: Engagement device

Claims

1. A control device for a vehicle, comprising: a power source; a continuously variable transmission in which a transmission element is wound between a primary pulley and a secondary pulley for transmitting the power of the power source to drive wheels; and an engagement device provided in a power transmission path between the power source and the continuously variable transmission, a transmission control unit configured to control a clamping pressure applied to the transmission element in the continuously variable transmission; an engagement device control unit configured to perform a sweep control for gradually increasing an engagement pressure of the engagement device when switching the engagement device from a released state to an engaged state, and when an execution time of the sweep control exceeds a predetermined time, perform a backup control for increasing the engagement pressure faster than the sweep control to quickly bring the engagement device into the engaged state; wherein the control device includes: the transmission control unit is configured to perform a clamping pressure increase control for increasing the clamping pressure before starting the backup control, to be higher than when the sweep control is executed; the engagement device control unit is configured to start the backup control after completion of the clamping pressure increase control when performing the backup control. A control device for a vehicle, characterized in that.

2. The engagement device control unit is configured to continue the sweep control when a heat generation amount in the engagement device is less than a predetermined heat generation amount when the execution time of the sweep control exceeds the predetermined time, and to perform the backup control when the heat generation amount is greater than or equal to the predetermined heat generation amount. The control device for a vehicle according to claim 1, characterized in that.

3. The engagement device control unit is configured to continue the sweep control when a differential rotational speed in the engagement device is less than a predetermined differential rotational speed when the execution time of the sweep control exceeds the predetermined time, and to perform the backup control when the differential rotational speed is greater than or equal to the predetermined differential rotational speed. The control device for a vehicle according to claim 1, characterized in that.

4. The primary pulley and the secondary pulley each include a hydraulic actuator configured to change a groove width between a fixed sheave and a movable sheave by supplying hydraulic pressure, wherein the transmission control unit is configured to temporarily increase a rotational speed of an oil pump that supplies an original pressure of the hydraulic pressure to be higher than a current rotational speed when performing the clamping pressure increase control. The control device for a vehicle according to any one of claims 1 to 3, characterized in that.

5. The control device for a vehicle according to claim 4, wherein when the actual value of the clamping pressure cannot be increased to a predetermined clamping pressure or more until a predetermined waiting time elapses after the rotation speed of the oil pump is temporarily increased, the transmission control unit further increases the rotation speed of the oil pump.

Images