Transmission input-torque control device

Abstract

In the present invention, when predetermined learning conditions have been met, an HEV-CU (70) regeneratively runs a motor generator (40), detects output torque of a torque converter (20) from the amount of regenerative power of the motor generator (40), and on the basis of the output torque and the engine speed during detection, learns a "capacity coefficient × torque ratio" value of the torque converter (20). After the learning, the HEV-CU (70), on the basis of the learned "capacity coefficient × torque ratio" value and the real-time engine speed, estimates torque input into an automatic transmission (50), and controls the engine (10) so that the estimated input torque will not exceed the upper limit of the input-permissible torque for the automatic transmission (50).

Description

Transmission input torque control device

[0001] The present invention relates to a transmission input torque control device for controlling torque input to a transmission.

[0002] Patent Document 1 discloses an engine torque control device that controls the engine torque to reduce when the input torque to the transmission becomes excessive in order to protect the transmission. In this engine torque control device, when the engine output torque input to the transmission exceeds the allowable upper limit torque of the transmission, an engine generated torque control value is set so that the transmission input torque becomes smaller than the allowable upper limit torque.

[0003] Generally, the allowable upper limit torque value that limits the input torque of such a transmission is set with a margin, i.e., taking into consideration the range of individual variations in engines, torque converters, etc., the accuracy of engine torque estimation, etc., and the like, so that even the upper limit (worst case) of the transmission does not exceed its limits.

[0004] Japanese Patent Application Laid-Open No. 2006-170116

[0005] Conventionally, the detection accuracy of the torque output from the engine or torque converter (i.e., the torque input to the transmission) has been low, necessitating a large margin. However, because the degree of individual variation differs for each engine or torque converter, a large margin can result in unnecessary (excessive) restriction of the output torque of the engine or the like (i.e., unnecessary reduction of the allowable upper limit torque of the transmission).

[0006] In particular, with mid-range or lower-end engines and torque converters, the output torque is limited even though there is a margin up to the limit of the transmission (hardware), meaning that even though there is a surplus, the performance cannot be fully utilized, resulting in a situation where power performance is kept low.

[0007] Therefore, there has been a demand for more accurate detection of the torque input to the transmission (i.e., the torque output from the engine and torque converter) and for increasing this torque as much as possible without exceeding the limits of the transmission's hardware (i.e., for the margin when setting the allowable upper limit torque to be as small as possible).

[0008] The present invention has been made to solve the above problems, and aims to provide a transmission input torque control device that can more accurately determine the torque output from the engine and torque converter, and that can increase the torque output from the engine and torque converter and input to the transmission as much as possible without exceeding the limits of the transmission (hardware) (i.e., lower the margin and increase the input allowable torque upper limit as much as possible).

[0009] A transmission input torque control device according to one aspect of the present invention comprises an engine that outputs engine torque, a torque converter connected to the output shaft of the engine, transmitting engine torque via oil and having a torque amplification function, a motor generator connected to the output shaft of the torque converter and operating as a motor that outputs motor torque during driving and as a generator during regeneration, an automatic transmission connected to the output shaft of the motor generator and converting and outputting the input torque, and a control unit that controls the engine, torque converter, motor generator, and automatic transmission, wherein the control unit, when a predetermined learning condition is met, causes the motor generator to perform regenerative operation, detects the output torque of the torque converter from the amount of regenerative power generated by the motor generator, learns the value of the "capacity coefficient x torque ratio" of the torque converter based on the output torque and the engine speed at the time of detection, and, after learning, estimates the input torque of the automatic transmission based on the learned value of the "capacity coefficient x torque ratio" and the real-time engine speed, and controls the engine so that the estimated input torque does not exceed the upper limit of the allowable input torque of the automatic transmission.

[0010] According to the present invention, the torque output from the engine and torque converter can be determined with greater accuracy, and the torque output from the engine and torque converter and input to the transmission can be increased as much as possible without exceeding the limits of the transmission (hardware) (i.e., the margin can be reduced and the input allowable torque upper limit can be increased as much as possible).

[0011] Fig. 1 is a block diagram showing the configuration of a transmission input torque control device according to an embodiment, and a main part of a hybrid vehicle to which the transmission input torque control device is applied. Fig. 2 is a diagram showing an example of a performance curve of a torque converter. Fig. 3 is a diagram for explaining how to obtain learning data of "capacity coefficient x torque ratio" with respect to a speed ratio. Fig. 4 is a diagram for explaining a method of estimating output torque using learning data. Fig. 5 is a flowchart showing the processing procedure for transmission input torque control by the transmission input torque control device according to an embodiment.

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be designated by the same reference numerals. In addition, the same elements will be designated by the same reference numerals in each drawing, and redundant explanations will be omitted.

[0013] First, a description will be given of the configuration of a transmission input torque control device 1 according to an embodiment and a main part of a hybrid vehicle to which the transmission input torque control device 1 is applied, using Fig. 1. Fig. 1 is a block diagram showing the configuration of a transmission input torque control device 1 and a main part of a hybrid vehicle to which the transmission input torque control device 1 is applied.

[0014] The engine 10 may be of any type, but may be, for example, a horizontally opposed, direct-injection, four-cylinder gasoline engine. In the engine 10, air drawn in through an air cleaner (not shown) is throttled by an electronically controlled throttle valve provided in the intake pipe, passes through an intake manifold, and is drawn into each cylinder of the engine 10. The amount of air drawn in through the air cleaner is detected by an air flow meter 83. The throttle valve is also provided with a throttle opening sensor that detects the opening of the throttle valve. Each cylinder is equipped with an injector that injects fuel. Each cylinder is also equipped with a spark plug that ignites the air-fuel mixture and an igniter-integrated coil that applies high voltage to the spark plug.

[0015] In each cylinder of the engine 10, a mixture of intake air and fuel injected by an injector is ignited by a spark plug and combusted. Exhaust gas after combustion is discharged through an exhaust pipe.

[0016] In addition to the air flow meter 83 and throttle opening sensor described above, a cam angle sensor for identifying the cylinder of the engine 10 is attached near the camshaft of the engine 10. Also, a crank angle sensor 84 for detecting the rotational position (rotational speed) of the crankshaft 15 of the engine 10 is attached near the crankshaft 15 of the engine 10. These sensors are connected to an engine control unit (hereinafter referred to as "ECU") 71, which will be described later. Various sensors, such as a water temperature sensor for detecting the temperature of the cooling water for the engine 10, are also connected to the ECU 71.

[0017] The driving force (engine torque) obtained by the combustion of the air-fuel mixture is output from a crankshaft 15. An automatic transmission 50 is connected to the crankshaft 15 of the engine 10 via a torque converter 20 having a clutch function and a torque amplification function, a motor generator 40, etc., which converts and outputs the engine torque from the engine 10 and / or the motor torque from the motor generator 40.

[0018] The torque converter 20 is mainly composed of a pump impeller 21, a turbine runner 22, and a stator 23. The pump impeller 21 connected to the crankshaft 15 generates a flow of oil, and the turbine runner 22, disposed opposite the pump impeller 21, receives power from the engine 10 via the oil to drive a turbine shaft 25. The stator 23, located between the two, rectifies the discharge flow (return) from the turbine runner 22 and returns it to the pump impeller 21, thereby generating torque amplification.

[0019] The torque converter 20 also has a lock-up clutch 24 that directly couples the input and output. When the lock-up clutch 24 is not engaged (in a non-lock-up state), the torque converter 20 amplifies the driving force of the engine 10 and outputs it, and when the lock-up clutch 24 is engaged (in a lock-up state), the torque converter 20 directly outputs the driving force of the engine 10. The rotation speed of the turbine runner 22 that constitutes the torque converter 20 (turbine rotation speed: output shaft rotation speed) is detected by a turbine rotation sensor 87. The detected turbine rotation speed is output to a transmission control unit (hereinafter referred to as "TCU") 74, which will be described later.

[0020] An example of a performance curve (torque characteristics) of the torque converter 20 is shown in Figure 2. The horizontal axis of Figure 2 represents the speed ratio, and the vertical axis represents the torque ratio, efficiency, and capacity coefficient (torque capacity coefficient). The speed ratio, torque ratio, efficiency, and capacity coefficient are each calculated using the following equations: Speed ​​ratio = output shaft rotation speed / input shaft rotation speed (1) Torque ratio = output shaft torque / input shaft torque (2) Efficiency = torque ratio × speed ratio (3) Capacity coefficient = input shaft torque / input shaft rotation speed ２ ...(4)

[0021] Furthermore, the above equation (4) can be transformed to the following equation (5): Input shaft torque = Capacity coefficient x Input shaft rotation speed ２... (5) Similarly, the above equation (2) can be transformed to obtain the following equation (6): Output shaft torque = torque ratio x input shaft torque ... (6) Then, the above equation (5) can be substituted into the above equation (6) to obtain the following equation (7): Output shaft torque = (capacity coefficient x torque ratio) x input shaft rotation speed ２ ...(7) Furthermore, by transforming the above equation (7), the following equation (8) is obtained: (Capacity coefficient x Torque ratio) = Output shaft torque / Input shaft rotation speed ２ ... (8) Here, since the input shaft rotation speed = engine rotation speed, by detecting the output shaft torque from the regenerative power generation amount (voltage x current) of the motor generator 40, it is possible to obtain the individual (for each individual) value of (capacity coefficient x torque ratio) (corresponding to the transmission characteristics described in the claims) (details will be described later).

[0022] A turbine shaft 25 of the torque converter 20 is connected to a motor generator 40 via a pair of gears (drive gear and driven gear) 27 and an output clutch 30 .

[0023] The output clutch 30 is interposed between the torque converter 20 and the motor generator 40, and interrupts torque transmission between the engine 10 and the torque converter 20 and the motor generator 40 (to the drive wheels). The output clutch 30 is released to separate the engine 10 and the torque converter 20 from the wheels, for example, during coasting control (coasting control), during EV driving by the motor generator 40, and during regenerative braking by the motor generator 40.

[0024] However, even during coasting control, the output clutch 30 is engaged during learning, which will be described later. That is, during learning, the output clutch 30 is engaged, and the motor generator 40 generates regenerative power using the torque output from the engine 10 and torque converter 20, and the torque is calculated from the amount of power generated (details will be described later). The operation (engagement and release) of the output clutch 30 is controlled by the TCU 74, which will be described later.

[0025] The motor generator 40 is configured as a synchronous generator motor (three-phase AC synchronous motor) that functions as both a motor that converts supplied electric power into mechanical power and a generator that converts input mechanical power into electric power. That is, the motor generator 40 operates as a motor that generates drive torque when driving the vehicle, and as a generator during regeneration. The motor generator 40 is controlled by a hybrid vehicle control unit (hereinafter referred to as "HEV-CU") 70, which will be described later.

[0026] The motor generator 40 is connected to a high-voltage battery 73 via an inverter 72a. When the motor generator 40 is caused to function as a motor, the inverter 72a converts DC power supplied from the high-voltage battery 73 into AC power to drive the motor generator 40. When the motor generator 40 is caused to function as a power generator (generator), the inverter 72a converts AC power generated by the motor generator 40 into DC power to charge the high-voltage battery 73. As described above, the engine 10, the torque converter 20, and the motor generator 40 are connected in series, and are configured so that the torque output from the torque converter 20 can be absorbed by the motor generator 40 through regeneration.

[0027] The output shaft of motor generator 40 is connected to the input shaft of automatic transmission 50 via a reduction gear 45 consisting of a pair of gears (reduction drive gear and reduction driven gear). Torque (driving force) output from engine 10 and / or motor generator 40 is transmitted (input) to automatic transmission 50 via reduction gear 45.

[0028] The automatic transmission 50 converts input torque and outputs the converted torque. In this embodiment, a stepped automatic transmission (step AT) is used as the automatic transmission 50.

[0029] The automatic transmission 50 is configured with a transmission mechanism including a transmission gear train. More specifically, the transmission mechanism is configured with a plurality of planetary gear sets each including a plurality of planetary gears, each including a sun gear, a ring gear, a pinion gear, and the like, and friction engagement elements, such as clutches and brakes, for switching (i.e., shifting) the power transmission paths of the plurality of planetary gear sets. Thus, the automatic transmission 50 shifts gears by engaging or disengaging friction engagement elements, such as clutches (hereinafter simply referred to as "clutches, etc." or "clutches"). Note that the automatic transmission 50 enters a neutral state when all clutches are disengaged. Therefore, for example, by automatically placing the automatic transmission 50 in a neutral state during learning, which will be described later, torque input from the wheels can be blocked (i.e., torque is prevented from being input to the motor-generator 40).

[0030] The automatic transmission 50 may be, instead of a planetary gear automatic transmission, a parallel two-shaft stepped automatic transmission, which selectively switches between a combination of gear trains on a pair of parallel shafts by engaging and disengaging multiple wet clutches to obtain a finite number of gear stages. Furthermore, instead of a stepped automatic transmission (step AT), a continuously variable transmission (CVT), such as a chain or belt type, or a dual clutch transmission (DCT), which has independent clutches in each of the odd-numbered and even-numbered gear sets and sequentially switches between them to change gears, may be used. The continuously variable transmission includes, for example, a double-pinion planetary gear train, a forward clutch, a reverse brake, and the like, and enters a neutral state by disengaging the forward clutch and reverse brake that constitute a forward / reverse switching mechanism that switches between forward and reverse rotation of the drive wheels (forward and reverse of the vehicle).

[0031] The output shaft of the automatic transmission 50 is connected to a front drive shaft 66 via a counter gear 55, which is made up of a pair of gears (a counter drive gear and a counter driven gear). The driving force (torque) output from the output shaft of the automatic transmission 50 is transmitted to a front differential (hereinafter also referred to as a "front differential") 67 via the counter gear 55 and the front drive shaft 66. The front differential 67 is, for example, a bevel gear-type differential device. The driving force from the front differential 67 is transmitted to the left front wheel via the left front wheel drive shaft and to the right front wheel via the right front wheel drive shaft.

[0032] Meanwhile, a transfer clutch 60 is provided downstream of the counter gear 55 (counter drive gear) on the output shaft, and adjusts the driving force (torque) transmitted to a rear differential (hereinafter also referred to as "rear differential") 69. The transfer clutch 60 controls the engagement force (i.e., torque distribution rate to the rear wheels) in accordance with the drive state of the four wheels (e.g., front wheel slippage), engine torque, etc. Therefore, the driving force output from the output shaft of the automatic transmission 50 is distributed in accordance with the engagement force of the transfer clutch 60 and transmitted to the rear wheels as well.

[0033] More specifically, the transfer clutch 60 is connected to a propeller shaft 68 extending rearward of the vehicle. Therefore, the driving force (torque) adjusted (distributed) by the transfer clutch 60 is transmitted to a rear differential 69 via the propeller shaft 68.

[0034] A left rear wheel drive shaft and a right rear wheel drive shaft are connected to the rear differential 69. Driving force from the rear differential 69 is transmitted to the left rear wheel via the left rear wheel drive shaft and to the right rear wheel via the right rear wheel drive shaft.

[0035] As configured as described above, this hybrid vehicle can drive the wheels (vehicle) using two power sources: the engine 10 and the motor generator 40. In addition, the motor generator 40 can be used for EV driving and regeneration (electric power generation).

[0036] More specifically, with the drive force transmission system configured as described above, the torque of the engine 10 and / or the torque of the motor generator 40 is input to the input shaft of the automatic transmission 50. The torque converted by the automatic transmission 50 is then output from the output shaft of the automatic transmission 50 and transmitted to the front drive shaft 66 via the counter gear 55. The torque is then distributed to the left and right by the front differential 67 and transmitted to the left and right front wheels.

[0037] Meanwhile, a portion of the torque output from automatic transmission 50 is transmitted to propeller shaft 68 via transfer clutch 60. When a predetermined clutch torque is applied to transfer clutch 60, torque distributed in accordance with the clutch torque is output to propeller shaft 68. The torque is then transmitted to the rear wheels via rear differential 69.

[0038] The engine 10, motor generator 40, and automatic transmission 50, which are the driving force sources of the vehicle, are comprehensively controlled by a control system comprising an HEV-CU 70 (corresponding to the control unit described in the claims), an ECU 71, a power control unit (hereinafter referred to as "PCU") 72, a TCU 74, a vehicle dynamics control unit (hereinafter referred to as "VDCU") 76, etc.

[0039] Each of the HEV-CU 70, ECU 71, PCU 72, TCU 74, and VDCU 76 is configured to include a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, and an input / output I / F, etc.

[0040] The HEV-CU 70, ECU 71, PCU 72, TCU 74, and VDCU 76 are connected to each other via a CAN (Controller Area Network) 100 so as to be able to communicate with each other.

[0041] Various sensors are connected to the HEV-CU 70, including, for example, an accelerator pedal sensor 81 that detects the amount of depression of the accelerator pedal, i.e., the opening degree of the accelerator pedal, and a resolver 82 that detects the rotational position (rotational speed) of the motor generator 40. In addition, the HEV-CU 70 receives various information such as engine speed, turbine speed (output shaft speed), amount of regenerated power, brake operation amount, steering wheel angle, yaw rate, etc. from the ECU 71, PCU 72, TCU 74, VDCU 76, etc. via the CAN 100.

[0042] Based on the various acquired information, the HEV-CU 70 comprehensively controls the driving of the engine 10, the motor generator 40, and the automatic transmission 50. The HEV-CU 70 calculates the required torque of the engine 10, the torque command value of the motor generator 40, and the target gear ratio of the automatic transmission 50 based on various information such as the accelerator pedal opening (torque required by the driver), engine speed, motor speed, the vehicle operating state (vehicle speed, steering angle, etc.), the amount of regenerative braking, and the state of charge (SOC) of the high-voltage battery 73. The HEV-CU 70 then outputs the calculated required torque, torque command value, target gear ratio, etc. via the CAN 100. The HEV-CU 70 also acquires the actual motor torque of the motor generator 40 and transmits it to the TCU 74 via the CAN 100.

[0043] The ECU 71 identifies the cylinder based on the output of the cam angle sensor described above, and calculates the engine speed (rotational speed) based on the change in the rotational position of the crankshaft 15 detected by the output of the crank angle sensor 84. The ECU 71 also acquires various information, such as the intake air volume, accelerator pedal position, air-fuel ratio of the air-fuel mixture, and water temperature, based on detection signals input from the various sensors described above. The ECU 71 then controls the engine 10 by controlling the fuel injection amount, ignition timing, and various devices, such as the electronically controlled throttle valve, based on the acquired information and the required torque (or required rotation speed) from the HEV-CU 70. The ECU 71 stops fuel injection to the engine 10 (performs a fuel cut) during coasting control (inertia running control). However, fuel injection is not stopped during learning, which will be described later.

[0044] The ECU 71 also calculates the actual engine torque (output torque) of the engine 10 based on, for example, the intake air amount and engine speed detected by the air flow meter 83. The ECU 71 then transmits information such as the engine speed (rotation speed) and actual engine torque to the TCU 74, HEV-CU 70, etc. via the CAN 100.

[0045] The PCU 72 drives the motor generator 40 via the inverter 72a based on the torque command value from the HEV-CU 70. Here, the inverter 72a converts the DC power of the high-voltage battery 73 into three-phase AC power and supplies it to the motor generator 40. Meanwhile, during regeneration, the inverter 72a converts the AC voltage generated by the motor generator 40 into DC voltage to charge the high-voltage battery 73. At this time, the PCU 72 detects the amount of power generated (current, voltage) during regeneration and sends the detected amount to the HEV-CU 70.

[0046] A brake switch 89 that detects whether the brake pedal is depressed and a brake fluid pressure sensor 90 that detects the master cylinder pressure (brake hydraulic pressure) of the brake actuator are connected to the VDCU 76. Also connected to the VDCU 76 are a wheel speed sensor 91 that detects the rotational speed of each wheel of the vehicle (vehicle speed).

[0047] The VDCU 76 drives the brake actuator to brake the vehicle in accordance with the amount of brake pedal operation (amount of depression), detects vehicle behavior using various sensors (e.g., wheel speed sensor 91, steering angle sensor, acceleration sensor, yaw rate sensor, etc.), and suppresses skidding and ensures vehicle stability during cornering by automatically applying pressure to the brakes and controlling the torque of the engine 10, etc. The VDCU 76 also has an anti-lock brake function (ABS function) that prevents wheel lock that occurs during sudden braking or braking on a slippery road surface, and maintains an appropriate slip ratio for each wheel to ensure directional stability and steering during braking, as well as an anti-lock brake function (ABS function) that obtains optimal braking force, and a traction control function (TCS function) that suppresses spin of the drive wheels that occurs on slippery road surfaces or due to excessive driving force, thereby ensuring vehicle stability and acceleration during starting and acceleration.

[0048] The VDCU 76 transmits detected braking information (brake operation information) such as brake switch 89 and brake fluid pressure, wheel speed (vehicle speed), and the like to the TCU 74, HEV-CU 70, ECU 71, and the like via the CAN 100.

[0049] The above-mentioned turbine rotation sensor 87 and the like are connected to the TCU 74. The TCU 74 transmits the detected turbine rotation speed (output shaft rotation speed) and the like to the HEV-CU 70 and the like via the CAN 100.

[0050] Further, the TCU 74 receives information such as actual engine torque from the ECU 71 via the CAN 100, information such as actual motor torque and accelerator opening from the HEV-CU 70, and information such as vehicle speed and brake operation from the VDCU 76.

[0051] The TCU 74 changes the gear ratio (gear stage) of the automatic transmission 50 based on the acquired various information (vehicle operating conditions) and the target gear ratio from the HEV-CU 70 .

[0052] At that time, the TCU 74 controls the operation of the solenoid valve (electromagnetic valve) that constitutes the control valve 75 to adjust the hydraulic pressure supplied to the automatic transmission 50 and change the gear ratio (gear stage) of the automatic transmission 50.

[0053] The TCU 74 also controls the operation of the solenoid valve that constitutes the control valve 75 to adjust the hydraulic pressure supplied to the transfer clutch 60 (i.e., adjust the engagement force), thereby adjusting the distribution ratio of the driving force transmitted to the rear wheels. Furthermore, the TCU 74 controls the operation of the solenoid valve that constitutes the control valve 75 to control the engagement and disengagement of the output clutch 30. During learning, which will be described later, the TCU 74 places the automatic transmission 50 in neutral, engages the output clutch 30, and disengages the lock-up clutch 24 in accordance with a request (command) from the HEV-CU 70.

[0054] Here, the HEV-CU 70 has a function to more accurately calculate the torque output from the engine 10 and the torque converter 20 and to increase the torque output from the engine 10 and the torque converter 20 and input to the automatic transmission 50 as much as possible without exceeding the limits of the automatic transmission 50 (hardware) (i.e., a function to lower the margin and increase the upper limit of the allowable input torque as much as possible). In the HEV-CU 70, this function is realized by a microprocessor executing a program stored in an EEPROM or the like.

[0055] First, when predetermined learning conditions are met (during learning), the HEV-CU 70 engages (requests the TCU 74 to engage) the output clutch 30 interposed between the torque converter 20 and the motor-generator 40. Also, when predetermined learning conditions are met (during learning), the HEV-CU 70 places (requests the TCU 74 to engage) the automatic transmission 50 in a neutral state. Furthermore, the HEV-CU 70 disengages (requests the TCU 74 to disengage) the lock-up clutch 24 of the torque converter 20. This blocks torque from the wheels, allowing all torque output from the engine 10 and the torque converter 20 to be absorbed (regenerated) by the motor-generator 40.

[0056] Here, the predetermined learning condition is, for example, whether the torque required by the driver, which is determined based on the operation amount (depression amount) of the accelerator pedal, is zero or approximately zero (accelerator off) and whether the automatic transmission 50 can be put into neutral. More specifically, examples of such conditions include when the vehicle is stopped (when the vehicle is stopped by braking in P range or D range) and when the vehicle is coasting (when the vehicle is running with the accelerator and brake off).

[0057] In addition, when regenerating (generating electricity) while the vehicle is stopped, increasing the engine speed may cause discomfort to the driver or increase noise inside and outside the vehicle (causing problems). On the other hand, when coasting, if the vehicle speed is relatively high, noise and other issues become relatively small, making it possible to perform measurement (learning) at a higher engine speed. Furthermore, for example, a configuration may be adopted in which measurement (learning) can be performed during maintenance (by providing a maintenance mode).

[0058] Next, when a predetermined learning condition is met, HEV-CU 70 causes motor generator 40 to perform regenerative operation, detects the output torque of torque converter 20 from the amount of regenerative power generated by motor generator 40, and calculates the value of "capacity coefficient x torque ratio" of torque converter 20 based on the output torque and the engine speed at the time of detection (using equation (8) above), and learns this value. Here, the amount of regenerative power generated by motor generator 40 can be measured with high precision because the voltage and current can be accurately measured.

[0059] Incidentally, since (capacity coefficient x torque ratio) depends on the speed ratio of the torque converter 20, the HEV-CU 70 controls (varies) the engine 10 speed to obtain multiple learned values ​​at any speed ratio, thereby obtaining multiple learned values ​​in a speed ratio range of, for example, approximately 0 to 0.6. That is, during learning, the HEV-CU 70 changes the engine speed to vary the speed ratio of the torque converter 20, thereby causing the motor-generator 40 to perform regenerative operation at multiple speed ratios, and detects the output torque of the torque converter 20 from the amount of regenerative power generated by the motor-generator 40. Then, based on the output torque and the engine speed at the time of detection (using the above equation (8)), the value of "capacity coefficient x torque ratio" for the speed ratio of the torque converter 20 is calculated and learned.

[0060] Next, the HEV-CU 70 acquires learning data (learning characteristic curve) of "capacity coefficient x torque ratio" versus speed ratio by curve fitting the multiple learning values ​​acquired at multiple speed ratios, taking into account the design values ​​of the torque converter 20. For example, as shown in FIG. 3 , learning data (learning characteristic curve) of "capacity coefficient x torque ratio" versus individual (individual) speed ratios is acquired by curve fitting from three learning values ​​(indicated by circles). Here, FIG. 3 is a diagram for explaining how to obtain learning data (learning characteristic curve) of "capacity coefficient x torque ratio" versus speed ratio. The horizontal axis of FIG. 3 represents the speed ratio, and the vertical axis represents the capacity coefficient, the torque ratio, and the design and learned values ​​of "capacity coefficient x torque ratio."

[0061] Here, by taking into consideration the design values ​​of the torque converter 20, it is possible to perform curve fitting with high accuracy using fewer learning values. Note that the curve fitting can be performed using a known method such as the least squares method. The acquired learning data is stored in a memory such as an EEPROM.

[0062] After that (after learning), the HEV-CU 70 estimates the input torque of the automatic transmission 50 from the above equation (7) based on the learned value of "capacity coefficient x torque ratio" corresponding to the real-time (control) speed ratio and the real-time (control) engine speed.

[0063] Here, during learning, it is difficult to measure (learn) up to the high load range (high engine speed). Therefore, as shown in Figure 4, the output torque at high load (high speed) is estimated from the measured value (learned value) at low load (low speed) using the above equation (7). Figure 4 is a diagram for explaining a method of estimating output torque using learning data. The horizontal axis of Figure 4 represents the input speed of the torque converter 20 (= engine speed), and the vertical axis represents the output torque of the torque converter 20.

[0064] At this time, the HEV-CU 70 estimates the torque input to the automatic transmission 50, taking into account the gear ratio of the reduction gear 45 between the motor generator 40 and the automatic transmission 50, and the torque (powering or regenerative) of the motor generator 40.

[0065] Then, the HEV-CU 70 controls (requests the ECU 71 to) the engine 10 (engine speed) so that the estimated input torque does not exceed the upper limit of the allowable input torque of the automatic transmission 50.

[0066] Next, the operation of the transmission input torque control device 1 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the processing steps for transmission input torque control (learning processing, input torque estimation processing, input torque limiting processing) by the transmission input torque control device 1. This processing is repeatedly executed at predetermined timings mainly by the HEV-CU 70.

[0067] First, in step S100, it is determined whether learning has already been completed. If learning has already been completed, the process proceeds to step S114, which will be described later. On the other hand, if learning has not yet been completed, the process proceeds to step S102.

[0068] In step S102, it is determined whether or not predetermined learning conditions are met. If the predetermined learning conditions are not met, the process temporarily ends. On the other hand, if the predetermined learning conditions are met, the process proceeds to step S104. Note that the predetermined learning conditions are as described above, and therefore a detailed description thereof will be omitted here.

[0069] In step S104, the lock-up clutch 24 of the torque converter 20 is released (requested by the TCU 74), the output clutch 30 is engaged (requested by the TCU 74), and the automatic transmission 50 is placed in neutral (requested by the TCU 74).

[0070] Next, in step S106, the motor generator 40 is operated for regeneration, the torque output from the torque converter 20 is detected from the amount of regenerative power generated by the motor generator 40, and the value of the "capacity coefficient x torque ratio" of the torque converter 20 is calculated and learned based on the output torque and the engine speed at the time of detection (using the above equation (8)).

[0071] Next, in step S108, the speed ratio is changed to determine whether a predetermined number of learned values ​​(e.g., three) have been acquired. If the predetermined number of learned values ​​has not yet been acquired, the engine speed (i.e., speed ratio) is changed in step S110, and the processes of steps S106 to S108 described above are repeated until the predetermined number of learned values ​​is acquired. That is, the torque output from torque converter 20 from the amount of regenerative power generated by motor-generator 40 is detected at a plurality of speed ratios, and the value of "capacity coefficient x torque ratio" for the speed ratio of torque converter 20 is calculated and learned based on the output torque and the engine speed at the time of detection (using equation (8) above).

[0072] On the other hand, when the predetermined number of learned values ​​have been acquired, the process proceeds to step S112. In step S112, the learned values ​​acquired at the plurality of speed ratios are curve-fitted in consideration of the design values ​​of the torque converter 20, and learned data (learned characteristic curve) of "capacity coefficient x torque ratio" with respect to the speed ratio is acquired and stored, for example, as a map.

[0073] Next, in step S114, the real-time (control time) turbine rotation speed (output shaft rotation speed) and engine rotation speed (input shaft rotation speed) are read, and the real-time speed ratio (output shaft rotation speed / input shaft rotation speed) is calculated from the turbine rotation speed and engine rotation speed. The output shaft rotation speed may also be calculated from the motor rotation speed.

[0074] In the next step S116, the learned data stored, for example as a map, in step S112 is searched for using the real-time speed ratio calculated in step S114, and a learned value of "capacity coefficient x torque ratio" corresponding to the speed ratio is obtained. Then, based on the learned value and the real-time engine speed, the torque input to the automatic transmission 50 is estimated using equation (7) above.

[0075] Then, in step S118, the engine 10 (engine speed) is controlled so that the estimated input torque calculated in step S116 does not exceed the upper limit of the allowable input torque of the automatic transmission 50. Then, the process temporarily exits from this process.

[0076] As described above in detail, according to this embodiment, when a predetermined learning condition is met, the motor-generator 40 is operated to perform regenerative operation. The output torque of the torque converter 20 is detected from the amount of regenerative power generated by the motor-generator 40. The value of "capacity coefficient x torque ratio" of the torque converter 20 is learned based on the output torque and the engine speed at the time of detection. After learning, the torque input to the automatic transmission 50 is estimated based on the learned value of "capacity coefficient x torque ratio" and the real-time engine speed. The engine 10 is controlled so that the estimated input torque does not exceed the upper limit of the allowable input torque of the automatic transmission 50. Here, because the amount of power generated by the motor-generator 40 (current value and voltage value) can be accurately detected, the torque output from the engine 10 and the torque converter 20 can be accurately detected. Furthermore, because the engine speed can be accurately detected, the "capacity coefficient x torque ratio" of each individual torque converter 20 can be accurately determined (learned). Therefore, the torque output from the engine 10 and the torque converter 20 can be more accurately determined from the learned value and the real-time engine speed.

[0077] As a result, according to this embodiment, when the vehicle is driven by the engine 10 (including the engine 10 and the motor generator 40), the torque output from the engine 10 and the torque converter 20 can be determined with greater accuracy, and the torque output from the engine 10 and the torque converter 20 and input to the automatic transmission 50 can be increased as much as possible without exceeding the limits of the automatic transmission 50 (hardware) (i.e., the margin can be reduced to increase the upper limit of the allowable input torque as much as possible). As a result, it is possible to improve power performance by fully utilizing the torque limit of the automatic transmission 50, for example, when starting on a slope or going over a bump.

[0078] In particular, according to this embodiment, during learning, the rotational speed of the engine 10 is varied to vary the speed ratio of the torque converter 20. At each of the multiple speed ratios, the output torque of the torque converter 20 is detected from the amount of regenerative power generated by the motor-generator 40. Multiple learned values ​​for each of the multiple speed ratios are acquired based on the output torque and the engine rotational speed at the time of detection. Furthermore, during this learning, the design values ​​of the torque converter 20 are taken into consideration, and the multiple learned learned values ​​at each of the multiple speed ratios are curve-fitted to acquire learned data of "capacity coefficient x torque ratio" for each speed ratio. After learning, the input torque of the automatic transmission 50 is estimated based on the learned value of "capacity coefficient x torque ratio" corresponding to the real-time speed ratio and the real-time engine rotational speed. The engine 10 is controlled so that the estimated input torque does not exceed the upper limit of the allowable input torque of the automatic transmission 50. In this way, learning (torque measurement) is performed while varying the speed ratio, enabling accurate estimation of torque in the high rotational speed range (high torque range). This improves the detection accuracy of the torque output from the torque converter 20, thereby reducing the margin required for setting the upper limit of the allowable input torque. Therefore, it is possible to fully utilize the torque limit of the automatic transmission 50.

[0079] According to this embodiment, the predetermined learning condition is whether the driver's requested torque, which is determined based on the accelerator pedal depression amount, is zero or approximately zero and the automatic transmission 50 can be placed in a neutral state. When the predetermined learning condition is met (i.e., during learning), the automatic transmission 50 is automatically placed in a neutral state. Therefore, the torque input from the wheel side to the motor generator 40 is blocked, and only the torque output from the engine 10 and the torque converter 20 can be detected. Furthermore, the output torque can be measured without causing any discomfort to the driver (without changing the drive torque of the wheels).

[0080] Furthermore, according to this embodiment, the output clutch 30 is provided between the torque converter 20 and the motor generator 40, and the output clutch 30 is engaged during learning. Therefore, during EV driving, normal regeneration (other than during learning), and normal coasting (other than during learning), the output clutch 30 is disengaged to disconnect the engine 10 and the torque converter 20 and reduce drag (friction), while during learning, the output clutch 30 is engaged to allow the motor generator 40 to regenerate using the torque output from the engine 10 and the torque converter 20, and the torque can be determined from the amount of power generated.

[0081] Furthermore, according to this embodiment, the input torque to the automatic transmission 50 is estimated by further taking into consideration the gear ratio of the reduction gear 45 interposed between the motor generator 40 and the automatic transmission 50, and the torque (power running or regeneration) of the motor generator 40. Therefore, the torque input to the automatic transmission 50 can be detected and controlled with higher accuracy.

[0082] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. For example, in the above embodiments, the present invention is described as being applied to an AWD (all-wheel drive) vehicle, but the present invention can also be applied to, for example, a 2WD vehicle. Furthermore, the type and mechanism of the automatic transmission 50 are not limited to those in the above embodiments. For example, instead of a stepped automatic transmission (step AT), the present invention can be applied to other types of transmissions, such as a continuously variable transmission (CVT) or a dual clutch transmission (DCT).

[0083] Furthermore, the system configuration of the controllers such as the HEV-CU 70, ECU 71, and TCU 74, and the functional division of each controller, are not limited to those in the above embodiment. For example, in the above embodiment, the HEV-CU 70, ECU 71, and TCU 74 are connected to each other via the CAN 100 so that they can communicate with each other, but the system configuration is not limited to this form and can be changed (integrated, etc.) as desired, taking into account functional requirements, costs, etc. Also, a configuration without the VDCU 76 may be used.

[0084] In the above embodiment, hydraulic clutches are used as the output clutch 30 and the transfer clutch 60, but electromagnetic clutches, for example, may also be used.

[0085] 1 Transmission input torque control device 10 Engine 15 Crankshaft 20 Torque converter 21 Pump impeller 22 Turbine runner 23 Stator 24 Lock-up clutch 25 Turbine shaft 27 Pair of gears (gear pair) 30 Output clutch 40 Motor generator 45 Reduction gear 50 Automatic transmission 55 Counter gear 60 Transfer clutch 66 Front drive shaft 67 Front differential 68 Propeller shaft 69 Rear differential 70 HEV-CU 71 ECU 72 PCU 72a Inverter 73 High-voltage battery 74 TCU 75 Control valve (valve body) 76 VDCU 81 Accelerator pedal sensor 82 Resolver 83 Air flow meter 84 Crank angle sensor 87 Turbine rotation sensor 89 Brake switch 90 Brake fluid pressure sensor 91 Wheel speed sensor 100 CAN

Claims

1. A transmission input torque control device comprising: an engine which outputs engine torque; a torque converter connected to an output shaft of the engine, transmitting engine torque via oil and having a torque amplifying function; a motor generator connected to an output shaft of the torque converter, operating as a motor which outputs motor torque during driving and acting as a generator during regeneration; an automatic transmission connected to an output shaft of the motor generator, converting and outputting input torque; and a control unit which controls the engine, the torque converter, the motor generator and the automatic transmission, wherein the control unit, when a predetermined learning condition is established, causes the motor generator to perform a regenerative operation, detects the output torque of the torque converter from the amount of regenerative power generated by the motor generator, and learns a value of the transfer characteristic of the torque converter based on the output torque and the engine speed at the time of detection, and after learning, estimates the torque input to the automatic transmission based on the learned value of the transfer characteristic of the torque converter and the real-time engine speed, and controls the engine so that the estimated input torque does not exceed an upper limit of the allowable input torque of the automatic transmission.

2. The transmission input torque control device according to claim 1, wherein the transmission characteristic of the torque converter is the "capacity coefficient x torque ratio" of the torque converter.

3. The transmission input torque control device described in claim 2, characterized in that the predetermined learning condition is whether or not the driver's requested torque, which is determined based on the amount of accelerator pedal operation, is zero or approximately zero and the automatic transmission can be placed in a neutral state, and the control unit automatically places the automatic transmission in a neutral state when the predetermined learning condition is met.

4. The transmission input torque control device according to claim 3, wherein the control unit: during learning, releases the lock-up clutch of the torque converter, varies the speed ratio, which is the ratio between the input rotation speed and the output rotation speed of the torque converter, operates the motor generator for regeneration at a plurality of speed ratios, detects the output torque of the torque converter from the amount of regenerative electricity generated by the motor generator, learns a value of "capacity coefficient x torque ratio" for the speed ratio of the torque converter based on the output torque and the engine rotation speed at the time of detection, and after learning, estimates an input torque of the automatic transmission based on the learned value of "capacity coefficient x torque ratio" corresponding to the real-time speed ratio and the real-time engine rotation speed, and controls the engine so that the estimated input torque does not exceed an upper limit of the allowable input torque of the automatic transmission.

5. A transmission input torque control device as described in claim 4, characterized in that the control unit acquires learning data of "capacity coefficient x torque ratio" against the speed ratio by curve fitting multiple learning values ​​acquired at multiple speed ratios, taking into account the design values ​​of the torque converter.

6. The transmission input torque control device according to claim 5, further comprising a clutch interposed between the torque converter and the motor generator, wherein the control unit engages the clutch during learning.

7. The transmission input torque control device according to claim 6, wherein the control unit estimates the input torque of the automatic transmission taking into account the gear ratio between the motor generator and the automatic transmission and the torque of the motor generator.

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