Lockup clutch control device

Abstract

To improve hydraulic pressure control of a lockup clutch so as to suppress vibration caused by backlash of a drive transmission system when further depression (additional depression) of an accelerator pedal is performed in a state where, although the accelerator pedal is gently depressed, a traveling load (road load) is large and a vehicle is traveling in a decelerating manner.SOLUTION: In a lockup clutch control device, in a state where a vehicle is traveling in a decelerating manner although an accelerator pedal is gently depressed, hydraulic pressure of a lockup clutch is set lower than hydraulic pressure when normal lockup clutch control is performed. Thereby, it is possible to suppress vibration caused by backlash of a drive transmission system when further depression of the accelerator pedal is subsequently performed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a lock-up clutch control device that controls the hydraulic pressure of a lock-up clutch provided in a vehicle. [Background technology]

[0002] In the lock-up clutch control device described in Patent Document 1, the oil pressure of the lock-up clutch is controlled based on engine torque, etc., so that the operating state of the lock-up clutch is determined based on the lock-up region diagram, throttle valve opening, and vehicle speed.

[0003] Furthermore, when the vehicle is decelerating and the accelerator opening is zero, flex lockup control during deceleration is performed, and the lockup clutch oil pressure is controlled to a level that puts the lockup clutch into a slip state. Furthermore, if the accelerator opening degree increases from 0 to greater than 0 during deceleration flex lockup control, it is determined that a tuck-in operation has occurred, and backlash elimination control is performed. In backlash elimination control, the increase in engine output that accompanies an increase in the accelerator opening degree is suppressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-12440 A Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to suppress vibrations caused by rattles in the drivetrain when the accelerator pedal is depressed (depressed further) from a state in which the accelerator pedal is gently depressed but the road load is large and the vehicle is decelerating, by improving the hydraulic control of the lock-up clutch. [Means for solving the problem]

[0006] In this lock-up clutch control system, when the accelerator pedal is gently depressed and the vehicle is decelerating, the oil pressure of the lock-up clutch is lowered below the oil pressure when normal lock-up clutch control is performed. This makes it possible to suppress vibrations caused by rattles in the drivetrain when the accelerator pedal is subsequently depressed further. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of a vehicle to which a lock-up clutch control device according to an embodiment of the present invention is applied, and is a diagram showing the main parts of a control system in the vehicle. [Figure 2] 2 is a schematic diagram of a main part of a drive transmission device of the vehicle. FIG. [Figure 3] FIG. 2 is a cross-sectional view of a main part of the drive transmission device. [Figure 4] 2 is a diagram conceptually showing a control device for controlling the hydraulic pressure of a lock-up clutch of the drive transmission device. FIG. [Figure 5] FIG. 3 is a diagram conceptually showing a lock-up region diagram stored in the lock-up clutch control device. [Figure 6] 4 is a flowchart showing a lock-up clutch hydraulic control program stored in the lock-up clutch control device. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lock-up clutch control device according to an embodiment of the present invention will be described in detail below with reference to the drawings. [Example]

[0009] As shown in Figure 1, a vehicle equipped with this lock-up clutch control device includes an engine 12 as a drive source, drive wheels 14, and a vehicle power transmission 16 (hereinafter referred to as power transmission 16) provided in a power transmission path between the engine 12 and the drive wheels 14. The power transmission 16 includes a torque converter (fluid transmission) 20 and an automatic transmission 22, a differential gear 26, a pair of axles 28, and the like, all of which are disposed within a case 18 (see Figure 2) serving as a non-rotating member attached to the vehicle body. The differential gear 26 is connected to an output rotating member 24 of the automatic transmission 22 via gears, and the axles 28 are connected to the differential gear 26. In the power transmission 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 26, the axles 28, and the like in this order.

[0010] The engine 12 is a power source for the vehicle and is, for example, an internal combustion engine such as a gasoline engine or a diesel engine.

[0011] The torque converter 20, automatic transmission 22, etc. are configured approximately symmetrically with respect to the axis RC of the transmission input shaft 30 (see Figures 2 and 3), which is the input rotating member of the automatic transmission 22, and the lower half of the axis RC is omitted in Figures 2 and 3.

[0012] As shown in FIGS. 2 and 3, the torque converter 20 includes a front cover 34 and a rear cover 35 that are welded to each other, a pump impeller (input member) 20p, a turbine impeller (output member) 20t, a lock-up clutch 32, and the like. The pump wheel 20p has a plurality of pump vanes 20f fixed to the inside of the rear cover 35, is connected to the crankshaft 12a of the engine 12 so as to be able to transmit power, and is arranged to be rotatable about an axis RC. The turbine wheel 20t faces the rear cover 35 and is connected to the transmission input shaft 30 so as to be able to transmit power. The lock-up clutch 32 is a hydraulic multi-plate friction clutch (wet multi-plate clutch) that controls the engagement state between the pump wheel 20p and the turbine wheel 20t by supplying a lock-up engagement pressure PSLU into a control oil chamber 20d (described later).

[0013] As shown in Fig. 3, the lock-up clutch 32 includes a plurality of annular first friction plates 38, a plurality of annular second friction plates 44, a pressing member 48, etc. The first friction plates 38 are engaged with outer-peripheral spline teeth 36a formed on the outer periphery of a first annular member 36 fixed to a front cover 34 connected to the pump wheel 20p so as to be rotatable integrally therewith but movably in the direction of the axis RC. The second friction plates 44 are engaged with inner-peripheral spline teeth 42a formed on the inner periphery of a second annular member 42 connected to the transmission input shaft 30 and the turbine wheel 20t via a damper device 40 so as to be rotatable relative to the axis RC but movably in the direction of the axis RC. The second friction plates 44 are disposed between the plurality of first friction plates 38. The pressing member 48 is an annular member facing the front cover 34, and is supported movably in the direction of the axis RC by a hub member 46 that is fixed to the inner circumferential portion 34a of the front cover 34 and supports the end of the transmission input shaft 30 on the front cover 34 side so as to be rotatable about the axis RC. In addition, an annular fixed member 50 is disposed opposite the pressing member 48 on the side opposite the front cover 34 side, and the oil-tight space between the fixed member 50 and the pressing member 48 forms the control oil chamber 20d. A return spring 52 is provided that biases the pressing member 48 toward the fixed member 50 in the direction of the axis RC, i.e., in a direction that moves the pressing member 48 away from the first friction plate 38 and the second friction plate 44 in the direction of the axis RC. A lockup engagement pressure PSLU is supplied to the control oil chamber 20d, which is a pressure for urging the pressing member 48 toward the front cover 34, i.e., toward the side that engages the lockup clutch 32 (the side that presses the first friction plate 38 and the second friction plate 44).

[0014] A main oil chamber (torque converter oil chamber) 20c is formed within the front cover 34 and rear cover 35 of the torque converter 20. The main oil chamber 20c has a hydraulic oil supply port 20a to which hydraulic oil output from the oil pump 33 is supplied and a hydraulic oil outlet port 20b through which the hydraulic oil supplied from the hydraulic oil supply port 20a flows out. A front-side oil chamber 20e and a rear-side oil chamber 20g are provided within the main oil chamber 20c. The front-side oil chamber 20e is a space formed between the pressing member 48 and the front cover 34, and is supplied with a second line oil pressure Psec (see FIG. 4 ), which is a pressure for urging the pressing member 48 toward the side opposite the front cover 34, i.e., the side that disengages the lock-up clutch 32. The rear-side oil chamber 20g is a chamber that communicates with the front-side oil chamber 20e, and oil flows out of the rear-side oil chamber 20g from the hydraulic oil outlet port 20b.

[0015] In the torque converter 20, for example, when the lock-up on pressure PLupON (kPa) as the lock-up engagement pressure PSLU supplied to the control oil chamber 20d is relatively large (the oil pressure in the front oil chamber 20e, i.e., the torque converter on pressure PTCin (kPa) is relatively small), the pressing member 48 is moved toward the front cover 34 as shown by the dashed line. The pressing member 48 presses the first friction plate 38 and the second friction plate 44, and the pump wheel 20p connected to the first annular member 36 and the turbine wheel 20t connected to the second annular member 42 rotate integrally. In other words, the lock-up clutch 32 is engaged, and the pump wheel 20p and the turbine wheel 20t are directly connected to each other.

[0016] Furthermore, for example, when the lock-up on pressure PLupON (kPa) supplied to the control oil chamber 20d is relatively small (the torque converter in pressure PTCin (kPa) in the front oil chamber 20e is relatively large), the pressing member 48 is moved to a position spaced apart 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 wheel 20t connected to the second annular member 42 rotate relative to each other. When the lock-up clutch 32 is disengaged, the pump wheel 20p and the turbine wheel 20t are disengaged.

[0017] In the lockup clutch 32, the transmission torque in the torque converter 20 is controlled based on the differential pressure ΔP (= PLupON - (PTCin + PTCout) / 2) between the lockup on pressure PLupON (kPa) in the control oil chamber 20d and the average value ((PTCin + PTCout) / 2) of the torque converter in pressure PTCin (kPa) in the front oil chamber 20e and the torque converter out pressure PTCout (kPa) output from the hydraulic oil outflow port 20b.

[0018] The lock-up differential pressure (engagement pressure) ΔP=PLupON-(PTCin+PTCout) / 2 is an empirical formula determined in advance through experiments, etc. In the formula, the torque converter in pressure PTCin and the torque converter out pressure PTCout vary depending on the engine speed Ne (rpm), turbine speed Nt (rpm), the differential speed therebetween (engine speed-turbine speed) ΔN (rpm), the second line oil pressure Psec (kPa), the ATF oil temperature Toil (°C), the engine torque Te (Nm), etc. The torque converter out pressure PTCout varies as the centrifugal oil pressure in the rear oil chamber 20g of the torque converter 20 varies due to changes in the engine speed Ne, turbine speed Nt, the ATF oil temperature Toil, etc.

[0019] The power transmission device 16 is equipped with a mechanical oil pump 33 that is connected to the pump impeller 20p so as to be capable of transmitting power. The oil pump 33 generates (discharges) oil pressure when rotated by the engine 12. The oil pressure discharged by the oil pump 33 is used for controlling the shifting of the automatic transmission 22, engaging the lock-up clutch 32 of the torque converter 20, supplying lubricating oil to various parts of the power transmission path of the power transmission device 16, and so on.

[0020] The lockup clutch 32 is controlled by an electronic control device (control device) 56 shown in FIG. 1 controlling the lockup differential pressure ΔP via a hydraulic control circuit (hydraulic circuit) 54. For example, the operating state of the lockup clutch 32 can be switched to one of a lockup release state (lockup off), a lockup slip state (slip state), and a lockup state (lockup on). The lockup release state is a state in which the lockup differential pressure ΔP is negative and the lockup clutch 32 is released. The lockup slip state is a state in which the lockup differential pressure ΔP is equal to or greater than zero and the lockup clutch 32 is partially engaged with slippage. The lockup state is a state in which the lockup differential pressure ΔP is at its maximum value and the lockup clutch 32 is fully engaged.

[0021] Regardless of whether lock-up clutch 32 is in the locked-up state, the lock-up slip state, or the lock-up released state, front oil chamber 20e and rear oil chamber 20g are the same chamber, i.e., front oil chamber 20e and rear oil chamber 20g are always in communication with each other, so lock-up clutch 32 is always cooled by hydraulic oil flowing from hydraulic oil supply port 20a to rear oil chamber 20g.

[0022] The automatic transmission 22 constitutes part of the power transmission path from the engine 12 to the drive wheels 14, and is equipped with a plurality of hydraulic friction engagement devices (first clutch C1 to fourth clutch C4, first brake B1, second brake B2), a one-way clutch F1, etc. In the automatic transmission 22, these are selectively engaged or disengaged to form a plurality of gear stages (speed stages) with different gear ratios (speed ratios). The automatic transmission 22 is a planetary gear type multi-stage transmission that functions as a stepped automatic transmission. For example, it is a stepped transmission that performs so-called clutch-to-clutch shifting, which is commonly used in vehicles. The automatic transmission 22 has a double-pinion first planetary gear set 58, a single-pinion second planetary gear set 60 configured as a Ravigneaux type, and a double-pinion third planetary gear set 62 on the same axis (on the axis RC), and changes the rotation of the transmission input shaft 30 and outputs it from the transmission output gear 24.

[0023] By controlling the engagement and disengagement of these hydraulic friction engagement devices, eight forward gears and one reverse gear are formed according to the accelerator operation by the driver, the vehicle speed V, etc. The gear ratio γ of the automatic transmission 22 corresponding to each gear (= transmission input shaft rotation speed Nin / transmission output gear rotation speed Nout) is determined appropriately by the gear ratios (= number of teeth of sun gear / number of teeth of ring gear) of the first planetary gear set 58, the second planetary gear set 60, and the third planetary gear set 62.

[0024] As shown in Fig. 4, the hydraulic control circuit 54 includes a lockup control valve 64, a linear solenoid valve SLU, a modulator valve 66, linear solenoid valves SL1 to SL6 (see Fig. 1), etc. The linear solenoid valve SLU linearly adjusts the first line hydraulic pressure PL, which is adjusted by a relief-type first line pressure adjusting valve 67 using the hydraulic pressure generated by the oil pump 33 as its source pressure, to a lockup engagement pressure PSLU. The modulator valve 66 adjusts the modulator hydraulic pressure PMOD to a constant value using the first line hydraulic pressure PL as its source pressure. The linear solenoid valves SL1 to SL6 control the operation of each hydraulic actuator (not shown) of the hydraulic friction engagement device of the automatic transmission 22.

[0025] The lockup control valve 64 is a pilot-operated two-position switching valve that includes a spool valve element (not shown), a spring 64a that biases the spool valve element toward the OFF position, and an oil chamber (not shown) that receives lockup engagement pressure PSLU to bias the spool valve element toward the ON position. In the lockup control valve 64, when the lockup engagement pressure PSLU as a pilot pressure is smaller than a predetermined value that is set relatively small, the spool valve element is held in the OFF position by the biasing force of the spring 64a. However, when the lockup engagement pressure PSLU is larger than the predetermined value, the spool valve element is held in the ON position against the biasing force of the spring 64a. In Figure 4, the solid lines indicate the flow path when the spool valve element is in the ON position, and the dashed lines indicate the flow path when the spool valve element is in the OFF position.

[0026] When the lockup control valve 64 is 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 a passage through which torque converter outlet pressure PTCout output from the hydraulic oil outlet port 20b of the torque converter 20 is guided. The second oil passage L2 is a passage through which lockup engagement pressure PSLU regulated by the linear solenoid valve SLU is guided. The third oil passage L3 is a passage through which lockup on pressure PLupON supplied to the control oil chamber 20d of the torque converter 20 is guided. The fourth oil passage L4 is a passage through which second line oil pressure Psec regulated by the second line pressure regulator valve 69 using oil pressure relieved from the first line pressure regulator valve 67 as the source pressure is guided. The fifth oil passage L5 is an oil passage through which the modulator oil pressure PMOD adjusted to a constant value by the modulator valve 66 is guided. The sixth oil passage L6 is an oil passage through which the torque converter in pressure PTCin supplied to the front oil chamber 20e of the torque converter 20 is guided. When the lock-up control valve 64 is in the OFF position, the first oil passage L1 is connected to the third oil passage L3, the second oil passage L2 is closed, the first oil passage L1 is connected to the cooler 68, the fourth oil passage L4 is connected to the sixth oil passage L6, and the fifth oil passage L5 is closed.

[0027] The hydraulic control circuit 54 configured as described above switches the hydraulic pressure supplied from the lock-up control valve 64 to the control oil chamber 20d and the front oil chamber 20e of 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 predetermined value is supplied to the lock-up control valve 64, the lock-up control valve 64 is switched to the ON position. The lock-up engagement pressure PSLU is supplied to the control oil chamber 20d as lock-up on pressure PLupON, and the modulator hydraulic pressure PMOD is supplied to the front oil chamber 20e as torque converter in pressure PTCin. When the lockup control valve 64 is in the ON position, the lockup on pressure PLupON > torque converter in pressure PTCin > torque converter out pressure PTCout. In this state, the lockup on pressure (engagement pressure) PLupON of the control oil chamber 20d is controlled, thereby controlling the lockup differential pressure ΔP (= PLupON - (PTCin + PTCout) / 2), and the operating state of the lockup clutch 32 is switched within the range from the slip state to lockup on (fully engaged).

[0028] When the lockup engagement pressure PSLU is smaller than a predetermined value, the lockup control valve 64 is switched to the OFF position by the biasing force of the spring 64a. The torque converter outlet pressure PTCout output from the hydraulic oil outlet port 20b is supplied to the control oil chamber 20d, and the second line oil pressure Psec is supplied to the front oil chamber 20e. That is, the torque converter outlet pressure PTCout is supplied to the control oil chamber 20d as the lockup on pressure PLupON, and the second line oil pressure Psec is supplied to the front oil chamber 20e as the torque converter in pressure PTCin. As a result, when the lockup control valve 64 is in the OFF position, the torque converter in pressure PTCin > torque converter out pressure PTCout > lockup on pressure PLupON, and the lockup clutch 32 is switched to a lockup off state (sometimes referred to as a lockup released state).

[0029] As shown in Fig. 1, the vehicle includes an electronic control device 56 that includes a so-called microcomputer. The electronic control device 56 includes, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various controls for the vehicle by utilizing the temporary storage function of the RAM and performing signal processing in accordance with programs previously stored in the ROM. The electronic control device 56 executes, for example, output control of the engine 12, lock-up clutch control that controls the lock-up engagement pressure PSLU of the lock-up clutch 32, i.e., the lock-up differential pressure ΔP, and gear shift control that controls the engagement pressure of the hydraulic friction engagement devices when shifting gears in the automatic transmission 22, via the hydraulic control circuit 54.

[0030] Various input signals detected by a plurality of various sensors provided on the vehicle are supplied to the electronic control device 56. The input signals include, for example, a signal representing a throttle valve opening θth (%) detected by a throttle valve opening sensor 70, a signal representing a vehicle speed V (km / h) detected by a vehicle speed sensor 72, a signal representing an engine speed Ne (rpm) which is the rotation speed of the engine 12 detected by an engine rotation sensor 74, a signal representing a turbine speed Nt (rpm) which is the rotation speed of the turbine impeller 20t of the torque converter 20 detected by a turbine rotation sensor 76, and a signal representing an accelerator opening Acc (%) which is the operation amount of the accelerator pedal detected by an accelerator operation amount sensor 78. The electronic control device 56 acquires the acceleration (including deceleration) of the vehicle based on the signal representing the vehicle speed V.

[0031] In addition, the electronic control device 56 outputs an engine output control command signal Se for controlling the output of the engine 12, a shift command pressure Sat for hydraulic control related to shifting of the automatic transmission 22, and a lock-up command pressure Slu for controlling the switching of the operating state of the lock-up clutch 32, etc.

[0032] 1 includes an engine output control unit 80, a gear shift control unit 82, a lock-up clutch control unit 84, a tip-in determination unit 86, etc. The engine output control unit 80 includes a backlash elimination control unit 80c, etc., and the lock-up clutch control unit 84 includes a complete lock-up control unit 84a, a lock-up release control unit 84b, a flex control unit 84c, a clutch oil pressure reduction unit 84f, etc.

[0033] The engine output control unit 80 calculates the required driving force Fdem by applying the actual accelerator opening Acc and vehicle speed V to a relationship (e.g., a driving force map) that has been experimentally or design-based and stored (i.e., predetermined). The engine output control unit 80 outputs an engine output control command signal Se to a throttle actuator, a fuel injection device, an ignition device, etc. (not shown) to control the output of the engine 12 so that the required driving force Fdem is obtained, taking into account transmission loss, accessory load, gear ratio γ of the automatic transmission 22, etc. Hereinafter, the control by the engine output control unit 80 (control that calculates the required driving force based on the driving force map and the actual accelerator opening, vehicle speed, etc., and performs the control so that the required driving force is obtained) may be referred to as normal engine control.

[0034] The backlash elimination control unit 80c executes backlash elimination control, which is control for suppressing engine output, when the tip-in determination unit 86 determines that a tip-in operation has occurred. In the backlash elimination control, a pushing torque (i.e., a torque suppressing torque for eliminating backlash) is applied to push the gear meshing from the driven side (follower side) of the engine 12 to suppress vibrations (shocks caused by backlash) caused by backlash in the drive system when the power transmission device (drive system) 16 transitions from a driven state to a driving state due to the tip-in operation. In this backlash elimination control, the engine torque (driving force) Te is made lower than the engine torque Te determined based on the accelerator opening, etc. (the engine torque corresponding to the required driving force calculated in normal engine control).

[0035] The tip-in determination unit 86 determines that a tip-in operation has occurred when the accelerator opening detected by the accelerator operation amount sensor 78 changes from a state where it is equal to or less than 0 to a state where it is greater than 0, that is, when the accelerator pedal (not shown) has been depressed from a state where it was not depressed. The determination of a tip-in operation by the tip-in determination unit 86 can be made to be performed during deceleration flex lock-up control.

[0036] The shift control unit 82 makes a shift decision by applying the actual vehicle speed V and throttle valve opening θth to a predetermined relationship (shift map, shift diagram) using the vehicle speed V and throttle valve opening θth (also including accelerator opening Acc, required driving force Fdem, etc.) as variables, and outputs a shift command pressure Sat as an instruction signal to the hydraulic control circuit 54 to engage and / or disengage hydraulic friction engagement devices involved in shifting of the automatic transmission 22 so as to obtain the determined predetermined forward gear. In accordance with this shift command pressure Sat, linear solenoid valves SL1 to SL6 provided in the hydraulic control circuit 54 are driven (operated) so that the automatic transmission 22 shifts gears, and hydraulic actuators of the hydraulic friction engagement devices involved in the shifting operate.

[0037] The lockup clutch control unit 84 executes lockup clutch control, controlling the lockup differential pressure (PLupON-(PTCin+PTCout) / 2)ΔP of the lockup clutch 32, i.e., the lockup command pressure Slu of the lockup engagement pressure PSLU. Using vehicle speed V and throttle valve opening θth as variables, the lockup clutch control unit 84 determines whether the vehicle state represented by the actual vehicle speed V and throttle valve opening θth is in the lockup-off region, flex lockup region, or full lockup region, using a predetermined relationship (for example, the lockup region diagram shown in FIG. 5) having the lockup-off region, flex lockup region, and full lockup region. The lockup clutch control unit 84 then controls the lockup command pressure Slu, which is an command signal, so that the operating state of the lockup clutch 32 corresponds to the determined region. In accordance with this lockup command pressure Slu, the linear solenoid valve SLU provided in the hydraulic control circuit 54 is driven (operated) so that the operating state of the lockup clutch 32 corresponds to the determined region. For example, the lockup region diagram shown in Figure 5 has a lockup-off region, a flex lockup region, and a complete lockup region when the throttle valve opening θth is positive. Hereinafter, this control by lockup clutch control unit 84 (control performed so that the operating state of lockup clutch 32 is determined based on the lockup region diagram, the actual vehicle speed, and the throttle valve opening, and control performed based on the oil pressure of lockup clutch 32, engine torque, etc.) may be referred to as normal lockup clutch control. Note that the lockup region diagram shown in Figure 5 is set for each gear position.

[0038] When the complete lockup control unit 84a determines that the vehicle state is in the complete lockup region based on the lockup region diagram shown in FIG. 5 or the like, it executes complete lockup control to control the lockup command pressure Slu of the lockup engagement pressure PSLU of the lockup clutch 32 so that the lockup clutch 32 is fully engaged.

[0039] When the lockup release control unit 84b determines that the vehicle state is in the lockup off region based on the lockup region diagram or the like, it performs lockup release control to control the lockup command pressure Slu of the lockup engagement pressure PSLU of the lockup clutch 32 so as to release the lockup clutch 32.

[0040] When the flex control unit 84c determines that the vehicle state is in the flex lockup region based on the lockup region diagram or the like, it performs flex lockup control, which is feedback control that adjusts the lockup command pressure Slu of the lockup engagement pressure PSLU of the lockup clutch 32 so that the lockup clutch 32 slips. In the flex control unit 84c, for example, the lockup command pressure Slu is controlled so that the actual rotational speed difference ΔN (rpm), which is the difference in actual rotational speed between the pump wheel 20p and the turbine wheel 20t, approaches a preset target rotational speed difference ΔN* (rpm). The actual rotational speed difference ΔN is the rotational speed difference between the rotational speed of the pump wheel 20p, i.e., the engine rotational speed Ne (rpm), and the rotational speed of the turbine wheel 20t, i.e., the turbine rotational speed Nt (rpm).

[0041] When the deceleration flex control unit 84d included in the flex control unit 84c determines based on the lockup region diagram that the vehicle state is in the flex lockup region or the complete lockup region and that the vehicle is decelerating without the accelerator pedal depressed (accelerator opening is 0), the deceleration flex control unit 84d executes deceleration flex lockup control, which is feedback control that adjusts the lockup command pressure Slu of the lockup engagement pressure PSLU so that the lockup clutch 32 slips, i.e., so that the actual differential rotation ΔN (rpm) between the pump wheel 20p and the turbine wheel 20t approaches the target differential rotation ΔN* (rpm). Note that, for example, the target differential rotation ΔN* in the deceleration flex lockup control can be set to a value equal to or greater than the target differential rotation ΔN* in the normal lockup clutch control.

[0042] The clutch oil pressure reducing unit 84f executes clutch oil pressure reduction control, which is control for reducing the oil pressure of the lock-up clutch 32 below the oil pressure under normal lock-up clutch control. The clutch oil pressure reduction control is executed when the accelerator opening detected by the accelerator 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 (when the vehicle is decelerating), in other words, when the deceleration (positive value) is greater than 0.

[0043] In a vehicle equipped with a lock-up clutch control device configured as described above, when the road load is large (for example, when traveling uphill), the vehicle may decelerate even if the accelerator pedal is lightly depressed. In this case, the engine 12 is in a driven state. If the accelerator pedal is subsequently depressed further (if the accelerator pedal is depressed further), the engine 12 switches to a driven state, and vibrations may occur due to rattles in the drivetrain.

[0044] On the other hand, when the accelerator pedal is depressed from a non-depressed state, it is determined that a tip-in operation has occurred, and backlash elimination control or the like is performed to suppress vibrations caused by backlash that occurs when the engine 12 switches from a driven state to a driving state. However, in general, vehicles often travel under light load (for example, when traveling on a flat road), and the engine 12 is normally in a driving state when the accelerator pedal is lightly depressed. Therefore, when the accelerator pedal is further depressed from a lightly depressed state, the tip-in determination unit 86 does not determine that a tip-in operation has occurred, and backlash elimination control is unlikely to be performed.

[0045] Furthermore, when the vehicle is decelerating with the accelerator pedal not depressed, deceleration flex lock-up control is performed, and the engagement pressure of lock-up clutch 32 is reduced. However, even when the vehicle is decelerating, if the accelerator pedal is lightly depressed (accelerator opening is greater than 0), it is difficult to perform deceleration flex lock-up control.

[0046] Therefore, in the lock-up clutch control device of this embodiment, when the accelerator opening is greater than 0 but less than the set opening, and the vehicle is decelerating, the clutch oil pressure reduction unit 84f reduces the engagement pressure of the lock-up clutch 32 to a value lower than the oil pressure when lock-up clutch control is performed normally.

[0047] In the electronic control unit 56, a lock-up clutch hydraulic pressure control program shown in the flowchart of FIG. 6 is executed at predetermined intervals. In step 1 (hereinafter abbreviated as S1, the same applies to the other steps), it is determined whether the accelerator opening A is greater than 0, smaller than the set opening Ath, and substantially constant. In step S2, it is determined whether the vehicle is decelerating. In step S3, it is determined whether the vehicle state (determined by the throttle valve opening and vehicle speed) is in the flex lockup region or the complete lockup region. If the determinations in steps S1, S2, and S3 are YES, the clutch oil pressure reducing unit 84f reduces the oil pressure (engagement pressure) P of the lockup clutch 32 to a value lower than the oil pressure when normal lockup clutch control is performed, and it is determined in steps S4 and S5 whether this reduced oil pressure state has continued for a first set time or longer. For example, the clutch oil pressure reducing unit 84f can reduce the oil pressure of the lockup clutch 32 by a predetermined set pressure lower than the oil pressure when normal lockup clutch control is performed, or can reduce the oil pressure to a value obtained by multiplying the oil pressure when normal lockup clutch control is performed by a set ratio smaller than 1.

[0048] In this embodiment, the oil pressure of the lock-up clutch 32 is reduced by the clutch oil pressure reducing section 84f, but the lock-up clutch 32 is not released.

[0049] Before the reduced oil pressure state continues for the first set time, the determination in S4 becomes NO, and in S6 it is determined whether the accelerator pedal has been depressed (the accelerator pedal has been depressed further). For example, it may be determined whether the accelerator opening has increased by a predetermined set value or more.

[0050] If the determination in S6 is NO, the process returns to S4. S4 to S6 are repeatedly executed, and if the determination in S6 becomes YES before the first set time has elapsed, S7 is executed, but if S4 to S6 are repeatedly executed, and the determination in S4 becomes YES before the determination in S6 becomes YES, the process returns to normal lock-up clutch control in S8.

[0051] If the determination in S6 is YES, then in S7 it is determined whether a second set time has elapsed since the accelerator pedal was depressed further. If the determination in S7 is YES, then in S8 the clutch pressure reduction control according to this embodiment is terminated and the process returns to normal lock-up clutch control. If the determination in S7 is NO, then the process waits for the determination to become YES. If the determination becomes YES, then in S8 the clutch pressure reduction control is terminated and the process returns to normal lock-up clutch control.

[0052] In this embodiment, when the accelerator pedal is lightly depressed but the vehicle is decelerating, the oil pressure of lock-up clutch 32 is lowered than when normal lock-up clutch control is performed. As a result, when the accelerator pedal is subsequently depressed and engine 12 transitions from a driven state to a driving state, vibrations (rattle shocks) caused by backlash in the drive train can be suppressed.

[0053] If the reduced oil pressure state due to the clutch pressure reduction control in this embodiment continues for a long period of time, there is a possibility that the accelerator pedal will not be depressed further, but even in that case, it is undesirable to maintain the reduced oil pressure state. For this reason, if the accelerator pedal is not further depressed before the first set time has elapsed since the oil pressure of lock-up clutch 32 was reduced, the system is configured to return to normal lock-up clutch control.

[0054] Furthermore, the reduced oil pressure state is maintained until the second set time has elapsed after the accelerator pedal is depressed further, thereby making it possible to more effectively suppress vibrations caused by rattles even without performing rattle elimination control on the engine 12.

[0055] The present invention can be similarly implemented even when the vehicle is equipped with a drive source including an electric motor. Furthermore, the present invention can be embodied in various forms with various modifications and improvements made based on the knowledge of those skilled in the art. [Explanation of symbols]

[0056] 12: Engine 20: Torque converter 20d: Control pressure chamber 32: Lock-up clutch 54: Hydraulic control circuit 56: Electronic control device 72: Vehicle speed sensor 78: Accelerator operation amount sensor 84: Lock-up clutch control unit Patentable invention

[0057] (1) A lock-up clutch control device that controls a lock-up clutch provided between a drive source and a transmission of a vehicle, A lock-up clutch control device including a clutch oil pressure reducing unit that reduces oil pressure in the lock-up clutch when an accelerator opening is smaller than a predetermined set opening and the vehicle is decelerating.

[0058] The drive 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. In the above embodiment, the lockup clutch control unit 84 corresponds to the lockup clutch control device.

[0059] (2) The lock-up clutch control device includes a normal lock-up clutch hydraulic pressure control section that controls the hydraulic pressure of the lock-up clutch so that a differential rotation, which is a value obtained by subtracting a turbine rotation speed from the rotation speed of the drive source, approaches a predetermined target differential rotation, 10. The lock-up clutch control device according to claim 1, wherein the clutch oil pressure reduction unit reduces the oil pressure of the lock-up clutch below the oil pressure controlled by the normal lock-up clutch oil pressure control unit when the accelerator opening is smaller than the set opening and the vehicle is decelerating.

[0060] The predetermined target differential rotation can be determined based on the difference between the target output rotation speed of the drive source and the target input rotation speed of the transmission. The target differential rotation can be determined based on the target output rotation speed of the drive source and the target gear ratio of the transmission, and can be set to 0. The predetermined target differential rotation speed may also be a preset differential rotation speed.

[0061] (3) A lock-up clutch control device as described in paragraph (2), wherein the clutch oil pressure reduction unit controls the oil pressure of the lock-up clutch so that the actual differential rotation, which is the differential rotation, approaches a target differential rotation that is greater than the target differential rotation speed determined by the normal lock-up clutch oil pressure control unit.

[0062] (4) The lock-up clutch control device includes a normal lock-up clutch hydraulic pressure control section that controls the hydraulic pressure of the lock-up clutch based on the output torque of the drive source, A lock-up clutch control device according to any one of items (1) to (3), wherein the clutch oil pressure reduction unit, when the accelerator opening is smaller than the set opening and the vehicle is decelerating, reduces the oil pressure of the lock-up clutch below the oil pressure controlled by the normal lock-up clutch oil pressure control unit when the output torque of the drive source is the same.

[0063] The oil pressure of the lock-up clutch may be controlled based on the output rotation speed of the drive source, the turbine rotation speed, the vehicle speed, the accelerator opening, and the like. (5) The lock-up clutch control device includes a normal lock-up clutch hydraulic pressure control section that controls the hydraulic pressure of the lock-up clutch based on the output torque of the drive source, etc., so that the lock-up clutch is in an operating state determined by the lock-up region diagram, vehicle speed, and throttle valve opening, A lock-up clutch control device according to any one of items (1) to (4), wherein the clutch oil pressure reduction unit reduces the oil pressure of the lock-up clutch below the oil pressure controlled by the normal lock-up clutch oil pressure control unit when the throttle valve opening, vehicle speed, and output torque of the drive source are the same, when the accelerator opening is smaller than the set opening and the vehicle is decelerating.

[0064] (6) A lock-up clutch control device according to any one of paragraphs (1) to (5), wherein the clutch oil pressure reduction unit terminates the reduction of the oil pressure of the lock-up clutch when the accelerator opening does not increase by more than a set value even if the reduction of the oil pressure of the lock-up clutch continues for a first set time, which is a predetermined set time.

[0065] After the reduction in the hydraulic pressure of the lock-up clutch is completed, the hydraulic pressure of the lock-up clutch is normally controlled by the hydraulic pressure control section.

[0066] (7) A lock-up clutch control device according to any one of (1) to (6), wherein the clutch oil pressure reduction unit maintains the reduction in oil pressure of the lock-up clutch from the time when the accelerator opening degree increases by a set value or more until a second set time, which is a predetermined set time, has elapsed.

[0067] (8) The vehicle includes a drive source control unit that controls the output of the drive source, The lock-up clutch control device according to any one of items (1) to (7), wherein the clutch oil pressure reduction unit reduces the oil pressure of the lock-up clutch when the drive source control unit controls the output of the drive source to approach a required drive force determined based on an accelerator opening and a vehicle speed.

Claims

1. A lock-up clutch control device that controls a lock-up clutch provided between a drive source and a transmission of a vehicle, A lock-up clutch control device including a clutch oil pressure reducing unit that reduces oil pressure in the lock-up clutch when an accelerator opening is smaller than a predetermined set opening and the vehicle is decelerating.

2. the lock-up clutch control device includes a normal lock-up clutch hydraulic pressure control unit that controls the hydraulic pressure of the lock-up clutch so that a differential rotation, which is a value obtained by subtracting a turbine rotation speed from the rotation speed of the drive source, approaches a predetermined target differential rotation, 2. A lock-up clutch control device according to claim 1, wherein the clutch oil pressure reduction unit reduces the oil pressure of the lock-up clutch below the oil pressure controlled by the normal lock-up clutch oil pressure control unit when the accelerator opening is smaller than the set opening and the vehicle is decelerating.

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