Lock-up clutch control device

Abstract

Provided is a lock-up clutch control device that suppresses vibration caused by a clearance collision in a drive transmission system by improving hydraulic pressure control of a lock-up clutch when a driving load (road load) is large although an accelerator pedal is in a slow-down state, and the driving load (road load) is not large even if the accelerator pedal is in a slow-down state. The accelerator pedal is further depressed from a state in which the vehicle is decelerated (further depressed). In this lock-up clutch control device, when an accelerator pedal is depressed slowly and a vehicle is traveling at a reduced speed, the hydraulic pressure of a lock-up clutch is lower than the hydraulic pressure when normal lock-up clutch control is performed. As a result, it is possible to suppress vibrations caused by a clearance collision in the drive transmission system when the accelerator pedal is further depressed thereafter.

Description

TECHNICAL FIELD

[0001] The present application relates to a lock-up clutch control device that controls hydraulic pressure of a lock-up clutch provided in a vehicle. BACKGROUND

[0002] In the lock-up clutch control device described in Patent Document 1, the hydraulic pressure of the lock-up clutch is controlled on the basis of engine torque and the like so that the operating state of the lock-up clutch becomes a state determined on the basis of a lock-up region map, a throttle opening degree, and a vehicle speed.

[0003] Further, in a case where the vehicle is in a deceleration state and the accelerator opening degree is zero, a deceleration-time flex lock-up control is performed to control the lock-up clutch hydraulic pressure to a magnitude that makes the operating state of the lock-up clutch a slip state.

[0004] Further, in the deceleration-time flex lock-up control, in a case where the state changes from the accelerator opening degree being zero to being greater than zero, it is determined that a tuck-in operation is performed, and a backlash control is performed. In the backlash control, an increase in engine output that occurs with an increase in the accelerator opening degree is suppressed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-12440 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] An object of the present application is to suppress vibration caused by backlash collision in a drive transmission system in a case where, although in a state where the accelerator pedal is being gently depressed, the running load (road load) is large, the accelerator pedal is depressed (further depressed) from a state where the vehicle is running in deceleration, by improving control of the hydraulic pressure of the lock-up clutch.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] In the present lock-up clutch control device, in a case where the accelerator pedal is being gently depressed and the vehicle is running in deceleration, the hydraulic pressure of the lock-up clutch is lower than in a case where the lock-up clutch control at the time of normal driving is performed. Thus, it is possible to suppress vibration caused by backlash collision in the drive transmission system in a case where the accelerator pedal is further depressed thereafter. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a schematic view of a vehicle to which a lock-up clutch control device according to an embodiment of the present application is applied, and is a view that shows main portions of a control system in the vehicle.

[0013] Figure 2 is a schematic view of a main part of a drive transmission device of the above vehicle.

[0014] Figure 3 is a sectional view of the main part of the above drive transmission device.

[0015] Figure 4 is a view conceptually showing a control device of hydraulic pressure and the like that controls a lock-up clutch of the above drive transmission device.

[0016] Figure 5 is a view conceptually showing a lock-up region line map stored in the above lock-up clutch control device.

[0017] Figure 6 is a flowchart showing a lock-up clutch hydraulic pressure control program stored in the above lock-up clutch control device. DETAILED DESCRIPTION

[0018] Hereinafter, a lock-up clutch control device of one embodiment of the present application will be described in detail with reference to the drawings.

[0019] Example 1

[0020] As shown in Figure 1 , a vehicle equipped with the present lock-up clutch control device includes an engine 12 as a drive source, drive wheels 14, and a vehicle power transmission device 16 (hereinafter, referred to as a power transmission device 16) and the like provided on a power transmission path between the engine 12 and the drive wheels 14. The power transmission device 16 includes a torque converter (fluid transmission device) 20 and an automatic transmission 22 disposed in a housing 18 (refer to Figure 2 ) as a non-rotating member mounted to a vehicle body, a differential gear device (differential gear) 26, a pair of axles 28, and the like. The differential gear device 26 is linked to an output rotating member 24 of the automatic transmission 22 via a gear, and the axles 28 are linked to the differential gear device 26. In the power transmission device 16, power output from the engine 12 is transmitted to the drive wheels 14 via the torque converter 20, the automatic transmission 22, the differential gear device 26, the axles 28, and the like in this order.

[0021] The engine 12 is a power source of the vehicle, and is, for example, an internal combustion engine such as a gasoline engine or a diesel engine.

[0022] The torque converter 20, the automatic transmission 22, and the like are roughly symmetrical with respect to an axis center RC of a transmission input shaft 30 (refer to Figure 2 , Figure 3 ) as an input rotating member of the automatic transmission 22, and a lower half of the axis center RC is omitted in Figure 2 , Figure 3 .

[0023] As shown in Figure 2 and Figure 3 , the hydraulic torque converter 20 includes a front cover 34 and a rear cover 35 which are welded to each other, a pump impeller (input member) 20p, a turbine (output member) 20t, and a lock-up clutch 32, and the like.

[0024] The pump impeller 20p has a plurality of pump vanes 20f fixed to the inner side of the rear cover 35, is power-transmissively coupled to the crankshaft 12a of the engine 12, and is rotatably disposed about the shaft center RC. The turbine 20t is opposite the rear cover 35 and is power-transmissively coupled to the transmission input shaft 30. The lock-up clutch 32 is a hydraulic multi-plate friction clutch (wet multi-plate clutch) which controls the engagement state between the pump impeller 20p and the turbine 20t by supplying a lock-up engagement pressure PSLU to a control oil chamber 20d described later.

[0025] As shown in Figure 3 , the lock-up clutch 32 includes a plurality of annular first friction plates 38, a plurality of annular second friction plates 44, and a pressing member 48, and the like. The first friction plates 38 are engaged with outer peripheral spline teeth 36a formed on the outer periphery of a first annular member 36 which is fixed to the front cover 34 rotatably coupled to the pump impeller 20p in a manner that cannot relatively rotate about the shaft center RC and can move in the shaft center RC direction. The second friction plates 44 are engaged with inner peripheral spline teeth 42a formed on the inner periphery of a second annular member 42 which is power-transmissively coupled to the transmission input shaft 30 and the turbine 20t via a damper device 40 in a manner that cannot relatively rotate about the shaft center RC and can move in the shaft center RC direction, and are respectively disposed between a plurality of the first friction plates 38. The pressing member 48 is an annular member opposite the front cover 34, is supported by a hub member 46 fixed to an inner peripheral portion 34a of the front cover 34 and supporting the end portion of the transmission input shaft 30 on the front cover 34 side so as to be rotatable about the shaft center RC, and is movable in the shaft center RC direction. In addition, an annular fixing member 50 is disposed opposite the pressing member 48 on the side opposite the front cover 34 side of the pressing member 48, and an oil-tight space between the pressing member 48 and the fixing member 50 is provided as the control oil chamber 20d. A return spring 52 is provided which urges the pressing member 48 toward the fixing member 50 in the shaft center RC direction, i.e., in a direction away from the first friction plates 38 and the second friction plates 44. The control oil chamber 20d is supplied with the lock-up engagement pressure PSLU which is a pressure for urging the pressing member 48 toward the front cover 34 side, i.e., toward the side (the side of pressing the first friction plates 38 and the second friction plates 44) on which the lock-up clutch 32 is engaged.

[0026] A main oil chamber (torque converter oil chamber) 20c is formed within the front cover 34 and rear cover 35 of the hydraulic torque converter 20. The main oil chamber 20c has: a working oil supply port 20a for supplying working oil output from the oil pump 33; and a working oil outlet port 20b for the working oil supplied from the working oil supply port 20a to flow out. A front oil chamber 20e and a rear oil chamber 20g are provided within the main oil chamber 20c. The front oil chamber 20e is the space formed between the pressing member 48 and the front cover 34, and is supplied with hydraulic pressure Psec (see reference 20g) via a second pipeline. Figure 4 The second pipeline hydraulic Psec is used to apply pressure to the pressing member 48 toward the side opposite to the front cover 34, i.e., toward the side that releases the lock-up clutch 32. The rear oil chamber 20g is a chamber that communicates with the front oil chamber 20e, and oil flows out from the working oil outlet port 20b.

[0027] In the torque converter 20, for example, when the lock-up opening pressure PLupON (kPa), which is the lock-up engagement pressure PSLU supplied to the control oil chamber 20d, is relatively large (while the hydraulic pressure in the front oil chamber 20e, i.e., the torque converter input pressure PTCin (kPa), is relatively small), the pressing member 48 is moved toward the front cover 34 as shown by the dashed line. The first friction plate 38 and the second friction plate 44 are pressed by the pressing member 48, and the pump wheel 20p connected to the first annular member 36 and the turbine 20t connected to the second annular member 42 rotate together. That is, the lock-up clutch 32 engages, and the pump wheel 20p and the turbine 20t are directly connected.

[0028] Additionally, for example, when the lock-up opening pressure PLupON (kPa) supplied to the control oil chamber 20d is relatively small (while the hydraulic torque converter input pressure PTCin (kPa) of the front oil chamber 20e is relatively large), the pressing member 48 is moved to a position separated from the first friction plate 38, as shown by the solid line. The pump wheel 20p, connected to the first annular member 36, and the turbine 20t, connected to the second annular member 42, rotate relative to each other. When the lock-up clutch 32 is released, the pump wheel 20p and the turbine 20t are released.

[0029] The torque transmitted in the hydraulic torque converter 20 is controlled based on the lock-up pressure difference ΔP (=PLupON-(PTCin+PTCout) / 2) in the lock-up clutch 32. The lock-up pressure difference ΔP is the average value ((PTCin+PTCout) / 2) between the lock-up opening pressure PLupON (kPa) in the control oil chamber 20d, the hydraulic torque converter input pressure PTCin (kPa) in the front oil chamber 20e, and the hydraulic torque converter output pressure PTCout (kPa) output from the working oil outlet port 20b.

[0030] Furthermore, the formula for the lock-up pressure difference (engagement pressure) ΔP = PLupON - (PTCin + PTCout) / 2 is an experimental formula determined in advance through experiments. In this formula, the torque converter input pressure PTCin and output pressure PTCout vary depending on the engine speed Ne (rpm), turbine speed Nt (rpm), the speed difference between them (engine speed - turbine speed) ΔN (rpm), the second line hydraulic pressure Psec (kPa), the ATF oil temperature Toil (°C), and the engine torque Te (Nm). Additionally, because the engine speed Ne, turbine speed Nt, ATF oil temperature Toil, etc., change, and the centrifugal hydraulic pressure within the rear oil chamber 20g of the torque converter 20 changes, the torque converter output pressure PTCout also changes.

[0031] Additionally, the power transmission device 16 includes a mechanical oil pump 33 that is connected to the pump wheel 20p to transmit power. The oil pump 33 is driven by the engine 12 to generate (discharge) hydraulic pressure. The hydraulic pressure discharged by the oil pump 33 can be used for gear shifting control of the automatic transmission 22, engaging the lock-up clutch 32 of the torque converter 20, or supplying lubricating oil to various parts of the power transmission path of the power transmission device 16, etc.

[0032] Depend on Figure 1 The electronic control device (control unit) 56 shown controls the lock-up pressure difference ΔP via a hydraulic control circuit (hydraulic circuit) 54, thereby controlling the lock-up clutch 32. For example, the operating state of the lock-up clutch 32 can be switched between a lock-up release state (lock-up closed), a lock-up slip state (slip state), and a lock-up state (lock-up open). The lock-up release state is when the lock-up pressure difference ΔP is negative and the lock-up clutch 32 is released. The lock-up slip state is when the lock-up pressure difference ΔP is above zero and the lock-up clutch 32 becomes partially engaged as it slips. The lock-up state is when the lock-up pressure difference ΔP is set to its maximum value and the lock-up clutch 32 is fully engaged.

[0033] Furthermore, regardless of whether the lock-up clutch 32 is in the locked state, the lock-up slip state, or the lock-up release state, the front oil chamber 20e and the rear oil chamber 20g are the same chamber, that is, the front oil chamber 20e and the rear oil chamber 20g are always connected to each other. Therefore, the lock-up clutch 32 is always cooled by the working oil flowing from the working oil supply port 20a to the rear oil chamber 20g.

[0034] The automatic transmission 22 forms part of the power transmission path from the engine 12 to the drive wheels 14, and includes multiple hydraulic friction engagement devices (first clutches C1 to fourth clutches C4, first brake B1, second brake B2) and a one-way clutch F1. In the automatic transmission 22, by selectively engaging or disengaging these devices, multiple gears (gear stages) with different transmission ratios (gear shift ratios) are formed. The automatic transmission 22 functions as a stepped automatic transmission, a planetary gear type multi-stage transmission. For example, it is a stepped transmission commonly used in vehicles that performs so-called clutch-to-clutch shifting. The automatic transmission 22 has a first planetary gear unit 58 of the double pinion type, a second planetary gear unit 60 of the Ravigneaux type of single pinion type, and a third planetary gear unit 62 of the double pinion type on the same axis (on the shaft RC), which changes the rotation of the transmission input shaft 30 and outputs it from the transmission output gear 24.

[0035] By controlling the engagement and disengagement of these hydraulic friction engagement devices, eight forward gears and one reverse gear are generated based on the driver's throttle operation, vehicle speed V, etc. The transmission ratio γ (= transmission input shaft rotation speed Nin / transmission output gear rotation speed Nout) of the automatic transmission 22 corresponding to each gear is appropriately determined by the gear ratios (= number of teeth on the sun gear / number of teeth on the ring gear) of the first planetary gear unit 58, the second planetary gear unit 60, and the third planetary gear unit 62.

[0036] like Figure 4 As shown, the hydraulic control circuit 54 includes a lock-up control valve 64, a linear solenoid valve SLU, a modulation valve 66, and linear solenoid valves SL1 to SL6 (see reference). Figure 1 The linear solenoid valve SLU linearly regulates the first line hydraulic pressure PL to the lock-up engagement pressure PSLU, wherein the first line hydraulic pressure PL is obtained by regulating the hydraulic pressure generated from the oil pump 33 as the source pressure by the pressure relief type first line pressure regulating valve 67. The modulation valve 66 uses the first line hydraulic pressure PL as the source pressure to regulate the modulation hydraulic pressure PMOD to a constant value. The linear solenoid valves SL1 to SL6 control the operation of the hydraulic actuators (not shown) of the hydraulic friction engagement device of the automatic transmission 22.

[0037] The lock-up control valve 64 is a pilot-operated dual-position switching valve, including a spool (not shown), a spring 64a that applies force to the spool towards the OFF position, and an oil chamber (not shown) that receives the lock-up engagement pressure PSLU to apply force to the spool towards the ON position. In the lock-up control valve 64, when the lock-up engagement pressure PSLU, which serves as the pilot pressure, is less than a relatively small predetermined value, the spool is held in the OFF position by the force of the spring 64a; however, when the lock-up engagement pressure PSLU is greater than the predetermined value, the spool is held in the ON position against the force of the spring 64a. Furthermore, Figure 4 In the diagram, the solid line represents the flow path when the spool of the valve is in the ON position, and the dashed line represents the flow path when the spool of the valve is in the OFF position.

[0038] With the lock-up control valve 64 in the ON position, the first oil passage L1 is closed, the second oil passage L2 is connected to the third oil passage L3, the first oil passage L1 is connected to the discharge oil passage EX, the fourth oil passage L4 is connected to the cooler 68, and the fifth oil passage L5 is connected to the sixth oil passage L6. The first oil passage L1 is the passage that introduces the torque converter output pressure PTCout from the working oil outlet port 20b of the torque converter 20. The second oil passage L2 is the passage that introduces the lock-up engagement pressure PSLU regulated by the linear solenoid valve SLU. The third oil passage L3 is the passage that introduces the lock-up opening pressure PLupON supplied to the control oil chamber 20d of the torque converter 20. The fourth oil passage L4 is the passage that introduces the second pipeline hydraulic pressure Psec, which is obtained by regulating the second pipeline pressure regulating valve 69 using the hydraulic pressure released from the first pipeline pressure regulating valve 67 as the source pressure. The fifth oil circuit L5 is the oil circuit that introduces the modulated hydraulic PMOD, which is adjusted to a constant value by the modulating valve 66. The sixth oil circuit L6 is the oil circuit that introduces the hydraulic torque converter input pressure PTCin, which is supplied to the front oil chamber 20e of the hydraulic torque converter 20. In addition, when the lock-up control valve 64 is in the OFF position, the first oil circuit L1 is connected to the third oil circuit L3, the second oil circuit L2 is closed, the first oil circuit L1 is connected to the cooler 68, the fourth oil circuit L4 is connected to the sixth oil circuit L6, and the fifth oil circuit L5 is closed.

[0039] The hydraulic control circuit 54, as described above, switches the hydraulic pressure supplied from the lock-up control valve 64 to the control chamber 20d and the front chamber 20e in the torque converter 20, thereby switching the operating state of the lock-up clutch 32. When a lock-up engagement pressure PSLU greater than a specified value is supplied to the lock-up control valve 64, the lock-up control valve 64 switches to the ON position. The lock-up engagement pressure PSLU is supplied to the control chamber 20d as the lock-up release pressure PLupON, and the modulated hydraulic pressure PMOD is supplied to the front chamber 20e as the torque converter input pressure PTCin.

[0040] Additionally, in the ON position of the lock-up control valve 64, the lock-up opening pressure PLupON > the torque converter input pressure PTCin > the torque converter output pressure PTCout. In this state, the lock-up opening pressure (engagement pressure) PLupON of the control oil chamber 20d is controlled, thereby controlling the lock-up pressure difference ΔP (=PLupON-(PTCin+PTCout) / 2), and the operating state of the lock-up clutch 32 switches from the slip state to the lock-up open (fully engaged) range.

[0041] In the lock-up control valve 64, when the lock-up engagement pressure PSLU is less than a specified value, the lock-up control valve 64 switches to the OFF position by the force of the spring 64a. The torque converter output pressure PTCout from the working oil outlet port 20b is supplied to the control oil chamber 20d, and the second pipeline hydraulic pressure Psec is supplied to the front oil chamber 20e. That is, the torque converter output pressure PTCout is supplied to the control oil chamber 20d as the lock-up release pressure PLupON, and the second pipeline hydraulic pressure Psec is supplied to the front oil chamber 20e as the torque converter input pressure PTCin. Thus, in the OFF position of the lock-up control valve 64, the torque converter input pressure PTCin > the torque converter output pressure PTCout > the lock-up release pressure PLupON, and the lock-up clutch 32 switches to the lock-up closed (sometimes called lock-up released) state.

[0042] like Figure 1 As shown, the vehicle is equipped with an electronic control unit 56, which includes a so-called microcomputer. The electronic control unit 56 includes, for example, a CPU, RAM, ROM, and input / output interfaces. The CPU performs signal processing according to a program pre-stored in the ROM while utilizing the temporary storage function of RAM, and executes various vehicle controls. For example, the electronic control unit 56 performs output control of the engine 12, or, via the hydraulic control circuit 54, performs lock-up clutch control (controlling the lock-up engagement pressure PSLU, i.e., the lock-up pressure difference ΔP), and shift control (controlling the engagement pressure of the hydraulic friction engagement device during automatic transmission 22 shifts).

[0043] The electronic control unit 56 is supplied with various input signals detected by multiple sensors installed in the vehicle. These input signals include, for example, signals representing the throttle opening θth (%) detected by the throttle opening sensor 70, the vehicle speed V (km / h) detected by the vehicle speed sensor 72, the engine speed Ne (rpm) of the engine 12 detected by the engine rotation sensor 74, the turbine speed Nt (rpm) of the torque converter 20 turbine 20 detected by the turbine rotation sensor 76, and the throttle pedal operation amount Acc (%) detected by the throttle operation amount sensor 78. In the electronic control unit 56, the vehicle's acceleration (including deceleration) is obtained based on the signal representing the vehicle speed V.

[0044] In addition, the electronic control unit 56 outputs an engine output control command signal Se for output control of the engine 12, a shift indication pressure Sat for hydraulic control related to the shift of the automatic transmission 22, and a lock-up indication pressure Slu for switching control of the working state of the lock-up clutch 32.

[0045] Figure 1 The electronic control unit 56 shown includes an engine output control unit 80, a transmission control unit 82, a lock-up clutch control unit 84, and an engagement determination unit 86. The engine output control unit 80 includes a backlash elimination control unit 80c, and the lock-up clutch control unit 84 includes a full lock-up control unit 84a, a lock-up release control unit 84b, a flexible control unit 84c, and a clutch hydraulic pressure reduction unit 84f.

[0046] The engine output control unit 80 calculates the required driving force Fdem by applying the actual throttle opening Acc and vehicle speed V to a pre-determined and stored relationship (e.g., a driving force mapping) obtained through experimentation or design. Taking into account transmission losses, accessory loads, and the gear ratio γ of the automatic transmission 22, the engine output control unit 80 outputs an engine output control command signal Se to the throttle actuator (not shown), fuel injection device, ignition device, etc., to control the output of the engine 12, thereby obtaining the required driving force Fdem. Hereinafter, the control performed by the engine output control unit 80 (calculating the required driving force based on the driving force mapping, actual throttle opening, and vehicle speed, etc., and performing control to obtain the required driving force) is sometimes referred to as normal engine control.

[0047] When the intervention determination unit 86 determines that an intervention action has been performed, the backlash elimination control unit 80c performs control to suppress engine output, i.e., backlash elimination control. In backlash elimination control, in order to suppress the vibration of the drive system caused by backlash (impact of backlash collision) when the power transmission device (drive system) 16 changes from a driven state to a driven state through the intervention action, a pushing torque (i.e., torque suppression torque for eliminating backlash) is applied to push the engagement of the gear from the driven side (driven side) of the engine 12. In this backlash elimination control, the engine torque (driving force) Te is made lower than the engine torque Te (the engine torque corresponding to the required driving force calculated in normal engine control) determined based on the throttle opening, etc.

[0048] When the throttle opening detected by the throttle operation amount sensor 78 changes from a state below 0 to a state above 0, that is, when the throttle pedal (not shown) changes from a state where it was never pressed to a state where it is pressed, the intervention determination unit 86 determines that an intervention action has been performed. The determination of the intervention action by the intervention determination unit 86 can be performed during the flexible lock-up control during deceleration.

[0049] The transmission control unit 82 applies the actual vehicle speed V and throttle opening θth to a predetermined relationship (transmission mapping, transmission line diagram) with vehicle speed V and throttle opening θth (the same applies to throttle opening Acc, required driving force Fdem, etc.) as variables to determine the transmission gear. To obtain the determined forward gear, the transmission indication pressure Sat is output as an indication signal to the hydraulic control circuit 54. The transmission indication pressure Sat engages and / or disengages the hydraulic friction engagement device involved in the transmission gear shift of the automatic transmission 22. According to the transmission indication pressure Sat, the linear solenoid valves SL1 to SL6 provided in the hydraulic control circuit 54 are driven (operated) to perform the transmission gear shift of the automatic transmission 22, and the hydraulic actuators of the hydraulic friction engagement device involved in the transmission gear shift operate.

[0050] The lock-up clutch control unit 84 performs lock-up clutch control, which controls the lock-up pressure difference (PLupON-(PTCin+PTCout) / 2)ΔP of the lock-up clutch 32, i.e., the lock-up indication pressure Slu of the lock-up engagement pressure PSLU. The lock-up clutch control unit 84 uses vehicle speed V and throttle opening θth as variables, and employs a predetermined relationship (e.g., a lock-up closed region, a flexible lock-up region, and a fully lock-up region) to define these relationships. Figure 5The system (as shown in the lock-up area diagram) determines which region of the vehicle state, represented by the actual vehicle speed V and throttle opening θth, falls within: the lock-up closed region, the flexible lock-up region, or the fully lock-up region. It then controls the lock-up indication pressure Slu, which serves as an indicator signal, to make the operating state of the lock-up clutch 32 correspond to the determined region. According to this lock-up indication pressure Slu, the linear solenoid valve SLU in the hydraulic control circuit 54 is actuated (operates), causing the operating state of the lock-up clutch 32 to change to the state corresponding to the determined region. For example, in... Figure 5 The lock-up region diagram is shown. When the throttle opening θth is positive, there are a lock-up closed region, a flexible lock-up region, and a fully lock-up region. Hereinafter, the control of this lock-up clutch control unit 84 (controlling the operating state of the lock-up clutch 32 to be determined based on the lock-up region diagram, the actual vehicle speed, and the throttle opening, i.e., hydraulic control of the lock-up clutch 32 based on engine torque, etc.) is sometimes referred to as normal lock-up clutch control. Furthermore, Figure 5 The lock-up area diagram shown is set for each gear position.

[0051] When based on Figure 5 When the vehicle is determined to be in the fully locked region by the lock-up area line diagram shown, the fully locked-up control unit 84a performs fully locked-up control. The fully locked-up control controls the lock-up engagement pressure PSLU and the lock-up indication pressure Slu of the lock-up clutch 32, so that the lock-up clutch 32 is fully engaged.

[0052] When the vehicle is determined to be in the locked-off region based on the locking region line diagram, the locking release control unit 84b performs locking release control. The locking release control controls the locking engagement pressure PSLU and the locking indication pressure Slu of the locking clutch 32 to release the locking clutch 32.

[0053] When the vehicle is determined to be in the flexible locking region based on the locking region line diagram, the flexible control unit 84c implements flexible locking control. This flexible locking control is a feedback control that adjusts the locking indication pressure Slu of the locking engagement pressure PSLU of the locking clutch 32 to cause the locking clutch 32 to slip. In the flexible control unit 84c, for example, the locking indication pressure Slu is controlled so that the actual speed difference ΔN (rpm) between the pump impeller 20p and the turbine 20t is close to a pre-set target speed difference ΔN* (rpm). Furthermore, the actual speed difference ΔN is the speed difference between the pump impeller 20p (engine speed Ne (rpm)) and the turbine 20t (turbine speed Nt (rpm)).

[0054] When the vehicle is determined to be in a flexible lock-up zone or a fully locked zone based on the lock-up zone line diagram and is in a deceleration period where the accelerator pedal is not depressed (throttle opening is 0), the deceleration flexible control unit 84d included in the flexible control unit 84c executes deceleration flexible lock-up control. This deceleration flexible lock-up control is a feedback control that adjusts the lock-up indicator pressure Slu of the lock-up engagement pressure PSLU, causing the lock-up clutch 32 to slip, i.e., making the actual speed difference ΔN (rpm) between the pump wheel 20p and the turbine 20t close to the target speed difference ΔN* (rpm). Furthermore, for example, the target speed difference ΔN* in the deceleration flexible lock-up control can be set to a value greater than or equal to the target speed difference ΔN* in the normal lock-up clutch control.

[0055] The clutch hydraulic pressure reduction unit 84f performs clutch hydraulic pressure reduction control, which reduces the hydraulic pressure of the lock-up clutch 32 to a level lower than the hydraulic pressure based on the normal lock-up clutch control. Clutch hydraulic pressure reduction control is performed when the throttle opening detected by the throttle operation amount sensor 78 is greater than 0 and less than the set opening, and the acceleration obtained by differentiating the vehicle speed detected by the vehicle speed sensor 72 is less than 0 (during deceleration). In other words, when the deceleration (positive value) is greater than 0.

[0056] In vehicles equipped with the lock-up clutch control device configured as described above, under heavy driving loads (road loads) (e.g., when driving uphill), the vehicle may slow down even when the accelerator pedal is gently pressed. In this situation, the engine 12 is in a driven state. Furthermore, when the accelerator pedal is pressed further (in the case of further pressing), the engine 12 switches to a driven state, and vibrations may occur due to clearances in the drive transmission system.

[0057] On the other hand, when the accelerator pedal changes from being unpressed to being pressed, it is determined that an intervention action has been performed, and gap reduction control is implemented to suppress vibrations caused by gap collisions that occur when the engine 12 switches from a driven state to a driven state. However, in general, vehicles are mostly driven under light loads (e.g., on flat roads), and it is common for the engine 12 to be in a driven state when the accelerator pedal is gently pressed. Therefore, if the accelerator pedal is further pressed from a gently pressed state, the intervention determination unit 86 does not determine an intervention action, making it difficult to perform gap reduction control.

[0058] Furthermore, when the accelerator pedal is not depressed and the vehicle is decelerating, the engagement pressure of the lock-up clutch 32 is reduced during deceleration soft lock-up control. However, even when the vehicle is decelerating, it is difficult to perform soft lock-up control during deceleration when the accelerator pedal is gently depressed (accelerator pedal opening is greater than 0).

[0059] Therefore, in the lock-up clutch control device of this embodiment, when the throttle opening is greater than 0 and less than the set opening and the vehicle is decelerating, the clutch hydraulic pressure reduction unit 84f reduces the engagement pressure of the lock-up clutch 32 to a level lower than the hydraulic pressure when performing lock-up clutch control under normal conditions.

[0060] In the electronic control device 56, execution is performed according to each predetermined set time. Figure 6 The flowchart shows the hydraulic control program for the lock-up clutch.

[0061] In step 1 (hereinafter referred to as S1; the other steps are the same), it is determined whether the throttle opening A is greater than 0, less than the set opening Ath, and approximately constant. In S2, it is determined whether the vehicle is in a deceleration phase. In S3, it is determined whether the vehicle's state (determined by the throttle opening and vehicle speed) is in a flexible lock-up region or a fully lock-up region. If the determinations in S1, S2, and S3 are "yes", then in S4 and S5, the clutch hydraulic pressure reduction unit 84f reduces the hydraulic pressure (engagement pressure) P of the lock-up clutch 32 to a level lower than the hydraulic pressure under normal lock-up clutch control, and determines whether the reduced hydraulic pressure state has lasted for more than a first set time. For example, the clutch hydraulic pressure reduction unit 84f can set the hydraulic pressure of the lock-up clutch 32 to be lower than the hydraulic pressure under normal lock-up clutch control by a predetermined set pressure, or set it to the hydraulic pressure obtained by multiplying the hydraulic pressure under normal lock-up clutch control by a set ratio less than 1, etc.

[0062] In addition, in this embodiment, the hydraulic pressure of the lock-up clutch 32 is reduced by the clutch hydraulic pressure reduction section 84f, but the lock-up clutch 32 is not in the released state.

[0063] Before the hydraulic pressure reduction state continues for a first set time, S4 determines "No". In S6, it is determined whether the accelerator pedal has been pressed (whether the accelerator pedal has been further pressed). For example, it can be determined whether the accelerator opening has increased by more than a predetermined set value.

[0064] If the determination in S6 is "No", return to S4. Repeat S4 to S6. If the determination in S6 becomes "Yes" before the first set time has elapsed, then execute S7. However, if the determination in S4 becomes "Yes" before the determination in S6 becomes "Yes", then in S8, return to the normal lock-up clutch control.

[0065] If the determination in S6 is "yes", in S7, it is determined whether a second preset time has elapsed since the point at which the accelerator pedal was further depressed. If the determination in S7 is "yes", in S8, the clutch pressure reduction control of this embodiment ends, and the system returns to the normal lock-up clutch control. If the determination in S7 is "no", the system waits for the determination to become "yes". When the determination becomes "yes", in S8, the clutch pressure reduction control ends, and the system returns to the normal lock-up clutch control.

[0066] Thus, in this embodiment, even when the accelerator pedal is being gently depressed, the hydraulic pressure of the lock-up clutch 32 is lower than when the vehicle is decelerating, which is the case during normal lock-up clutch control. Therefore, it is possible to suppress vibrations (impacts from gap collisions) caused by the drive system gaps when the engine 12 transitions from a driven state to a driven state when the accelerator pedal is depressed subsequently.

[0067] In this embodiment, if the hydraulic pressure reduction state caused by the clutch pressure reduction control persists for an extended period, it may be impossible to further depress the accelerator pedal. However, even in this case, it is undesirable to maintain the hydraulic pressure reduction state. Therefore, before a first set time has elapsed since the hydraulic pressure of the lock-up clutch 32 was reduced, and if the accelerator pedal is not further depressed, the lock-up clutch control is returned to normal operation.

[0068] Furthermore, the hydraulic pressure is maintained in a reduced state from the moment the accelerator pedal is further depressed until a second set time has elapsed. Therefore, even without gap-eliminating control of the engine 12, vibrations caused by gap collisions can be suppressed more effectively.

[0069] Furthermore, the present invention can be performed in the same way even when the vehicle has a drive source including an electric motor.

[0070] Furthermore, the present invention can be implemented in various ways with various modifications and improvements based on the knowledge of those skilled in the art.

[0071] Explanation of reference numerals in the attached figures

[0072] 12: Engine; 20: Hydraulic torque converter; 20d: Control pressure chamber

[0073] 32: Lock-up clutch; 54: Hydraulic control circuit; 56: Electronic control unit; 72: Vehicle speed sensor; 78: Throttle operation sensor; 84: Lock-up clutch control unit.

[0074] Inventions that are eligible for patents

[0075] (1) A lock-up clutch control device for controlling a lock-up clutch disposed between a drive source and a transmission of a vehicle, wherein,

[0076] The system includes a clutch hydraulic reduction unit that reduces the hydraulic pressure of the lock-up clutch when the throttle opening is less than a predetermined set opening and the vehicle is decelerating.

[0077] The driving source may include an electric motor but not an engine, may include an engine but not an electric motor, or may include both an engine and an electric motor.

[0078] In the above embodiments, the lock-up clutch control unit 84 corresponds to the lock-up clutch control device.

[0079] (2) The lock-up clutch control device according to (1), wherein,

[0080] The lock-up clutch control device includes a normal-time lock-up clutch hydraulic control unit that controls the hydraulic pressure of the lock-up clutch so that the value obtained by subtracting the turbine speed from the rotational speed of the drive source, i.e., the speed difference, is close to a predetermined target speed difference.

[0081] When the throttle opening is less than the set opening and the vehicle is decelerating, the clutch hydraulic pressure reduction unit reduces the hydraulic pressure of the lock-up clutch to a level lower than the hydraulic pressure controlled by the normal lock-up clutch hydraulic pressure control unit.

[0082] The specified target speed difference can be determined based on the difference between the target output speed of the drive source and the target input speed of the transmission. The target speed difference can be determined based on the target output speed of the drive source, the target gear ratio of the transmission, vehicle speed, and throttle opening, or it can be set to 0.

[0083] In addition, the specified target speed difference can be a predetermined set speed difference.

[0084] (3) According to the lock-up clutch control device described in (2), wherein the clutch hydraulic pressure reduction unit controls the hydraulic pressure of the lock-up clutch so that the speed difference, i.e. the actual speed difference, is close to a target speed difference that is larger than the target speed difference determined in the lock-up clutch hydraulic pressure control unit under normal conditions.

[0085] (4) The lock-up clutch control device according to any one of (1) to (3), wherein,

[0086] The lock-up clutch control device includes a normal-time lock-up clutch hydraulic control unit, which controls the hydraulic pressure of the lock-up clutch based on the output torque of the drive source.

[0087] When the throttle opening is less than the set opening and the vehicle decelerates, the clutch hydraulic pressure reduction unit reduces the hydraulic pressure of the lock-up clutch to a level lower than the hydraulic pressure controlled by the normal lock-up clutch hydraulic pressure control unit when the output torque of the drive source is the same.

[0088] The hydraulic pressure of the lock-up clutch is sometimes controlled based on the output speed of the drive source, the turbine speed, the vehicle speed, and the throttle opening.

[0089] (5) The lock-up clutch control device according to any one of (1) to (4), wherein,

[0090] The lock-up clutch control device includes a normal-time lock-up clutch hydraulic control unit, which controls the hydraulic pressure of the lock-up clutch based on the output torque of the drive source, so that the lock-up clutch is in an operating state determined by the lock-up zone diagram, vehicle speed, and throttle opening.

[0091] When the throttle opening is less than the set opening and the vehicle decelerates, the clutch hydraulic pressure reduction unit reduces the hydraulic pressure of the lock-up clutch to a level lower than that controlled by the normal lock-up clutch hydraulic pressure control unit when the throttle opening, vehicle speed, and output torque of the drive source are the same.

[0092] (6) The lock-up clutch control device according to any one of (1) to (5), wherein, even if the reduction of the hydraulic pressure of the lock-up clutch continues for a first set time of a predetermined set time, the clutch hydraulic pressure reduction section terminates the reduction of the hydraulic pressure of the lock-up clutch if the throttle opening does not increase by more than a set value.

[0093] After the hydraulic pressure of the lock-up clutch has decreased, the hydraulic pressure of the lock-up clutch is controlled by the normal hydraulic control unit.

[0094] (7) The lock-up clutch control device according to any one of (1) to (6), wherein, from the time the throttle opening increases to a set value or above until a second set time, which is a predetermined set time, the clutch hydraulic pressure reduction section maintains the reduction of the hydraulic pressure of the lock-up clutch.

[0095] (8) The lock-up clutch control device according to any one of (1) to (7), wherein,

[0096] The vehicle includes a drive source control unit that controls the output of the drive source.

[0097] When the output of the drive source is controlled by the drive source control unit to approach the required drive force determined based on the throttle opening and vehicle speed, the clutch hydraulic pressure reduction unit reduces the hydraulic pressure of the lock-up clutch.

Claims

1. A lock-up clutch control device for controlling a lock-up clutch disposed between a drive source and a transmission of a vehicle, wherein, The system includes a clutch hydraulic reduction unit, which reduces the hydraulic pressure of the lock-up clutch when the throttle opening is less than a predetermined set opening and the vehicle is decelerating.

2. The lock-up clutch control device according to claim 1, wherein, The lock-up clutch control device includes a normal-time lock-up clutch hydraulic control unit, which controls the hydraulic pressure of the lock-up clutch so that the value obtained by subtracting the turbine speed from the rotational speed of the drive source, i.e., the speed difference, is close to a predetermined target speed difference. When the throttle opening is less than the set opening and the vehicle decelerates, the clutch hydraulic pressure reduction unit reduces the hydraulic pressure of the lock-up clutch to a level lower than the hydraulic pressure controlled by the normal lock-up clutch hydraulic pressure control unit.

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