JP5468213B2 - Control device for automatic transmission - Google Patents

Description

  The present invention relates to a control device for an automatic transmission that executes shift control according to a shift pattern set based on a vehicle speed and an engine load.

  A torque converter is provided between the engine and the automatic transmission. Since this torque converter is a slip element that transmits engine power via hydraulic oil, it has been a factor that reduces power transmission efficiency during steady running. Therefore, in order to improve the power transmission efficiency of the torque converter, the torque converter is provided with a lock-up clutch that directly connects the input element and the output element.

  By the way, when performing shift control of an automatic transmission, a predetermined shift pattern is referred to based on the vehicle speed and the accelerator opening, and a shift stage is set according to the driving situation. It was difficult to control the gear appropriately. In other words, the speed ratio and torque ratio of the torque converter are greatly different between the lock-up state in which the lock-up clutch is engaged and the converter state in which the lock-up clutch is released. It was difficult to perform.

In view of this, a control device has been proposed that controls the upshift and downshift of an automatic transmission based on the operating state of a lockup clutch (see, for example, Patent Document 1). In this control device, the shift pattern used in the lock-up state and the shift pattern used in the converter state are separately set, so that the shift control is appropriately executed according to the operating state of the lock-up clutch. I am doing so.
JP-A-8-159268

  However, since the control device described in Patent Document 1 permits a downshift at an earlier timing in the lock-up state and permits a downshift at a later timing in the converter state, the fuel consumption performance of the vehicle is improved. There is a risk of significant reduction.

  That is, in the lock-up state in which the lock-up clutch is engaged, the torque converter efficiency is almost 100%. Therefore, in order to improve the fuel efficiency of the vehicle, the engine should be operated in an operating region where the fuel consumption rate is good. is important. In this lock-up state, allowing the downshift at an earlier timing increases the engine speed and deteriorates the fuel consumption rate of the engine, and thus decreases the fuel efficiency of the vehicle. .

  In the converter state where the lock-up clutch is released, slipping occurs and the torque converter efficiency is greatly reduced. Therefore, in order to improve the fuel efficiency of the vehicle, a downshift is performed to improve the torque converter efficiency. It is important to. In this converter state, allowing the downshift at a later timing is a factor for continuing low torque converter efficiency, which is a factor for reducing the fuel efficiency of the vehicle.

  An object of the present invention is to improve fuel efficiency of a vehicle equipped with an automatic transmission having a lock-up clutch.

Control system for an automatic transmission according to the present invention, follow the shift pattern is set based on the vehicle speed and the engine load, a control apparatus for an automatic transmission for performing a speed change control by switching the gear position, the engine and the transmission A torque converter that is provided between the mechanism and the engine for transmitting engine power to the speed change mechanism; a lock-up clutch that is provided between an input element and an output element of the torque converter and operates in an engaged state and a released state; When the lockup determination means for determining the operation state of the lockup clutch, and at least one of the vehicle speed and the engine load changes beyond the downshift line in the shift pattern, the transmission mechanism Downshift control means for performing a downshift, wherein the lockup clutch is engaged with the downshift control means If the lockup clutch is in a disengaged state, a lower engine load and higher than the first downshift line are executed. A downshift is performed based on a second downshift line set on the vehicle speed side.

  The control device for an automatic transmission according to the present invention is characterized in that the engine load is represented by at least one of an accelerator opening and a throttle opening.

  In the automatic transmission control apparatus according to the present invention, the engagement state of the lockup clutch includes a slip state in which the input element and the output element are connected while sliding the lockup clutch. .

  According to the present invention, since the second downshift line is set at a lower engine load and higher vehicle speed than the first downshift line, when the lockup clutch is released, it is based on the second downshift line. It is possible to execute a downshift at an early timing. As a result, even when the lockup clutch is released and the torque converter efficiency is reduced, the torque converter efficiency can be improved by the early downshift, and the fuel efficiency of the vehicle can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a skeleton diagram showing an automatic transmission 10 to which an automatic transmission control apparatus according to an embodiment of the present invention is applied. As shown in FIG. 1, the automatic transmission 10 includes a transmission input shaft 13 coupled to the engine 11 via a torque converter 12, and a transmission output shaft 15 coupled to the transmission input shaft 13 via a transmission mechanism 14. And have. A front wheel output shaft 17 is connected to the transmission output shaft 15 via a gear train 16, and a rear wheel output shaft 19 is connected via a transfer clutch 18. The driving force output from the speed change mechanism 14 is transmitted from the front wheel output shaft 17 to the front wheels via the front differential mechanism 20. Further, the driving force output from the speed change mechanism 14 is transmitted to the rear wheel output shaft 19 via the transfer clutch 18, and then is transmitted from the rear wheel output shaft 19 to the rear wheels via a propeller shaft and a rear differential mechanism (not shown). Communicated. Note that the torque distribution ratio of the front and rear wheels can be controlled by controlling the fastening force of the transfer clutch 18.

  The torque converter 12 includes a pump impeller 23 connected to the crankshaft 21 via a front cover (input element) 22, and a turbine runner 24 facing the pump impeller 23. A turbine shaft 26 is connected to the turbine runner 24 via a turbine hub (output element) 25, and the transmission input shaft 13 is connected to the turbine shaft 26. A stator 29 is provided between the pump impeller 23 and the turbine runner 24 and fixed to the transmission case 28 via a one-way clutch 27. Further, a hydraulic lockup clutch 30 is provided between the front cover 22 of the torque converter 12 and the turbine hub 25.

  An apply chamber 31 is defined on one side of the lockup clutch 30, and a release chamber 32 is defined on the other side of the lockup clutch 30. By supplying hydraulic oil to the apply chamber 31 and discharging the hydraulic oil from the release chamber 32, the lockup clutch 30 is switched to an engaged state in which the lockup clutch 30 is pressed against the front cover 22. By controlling the torque converter 12 in such a lock-up state, the front cover 22 and the turbine hub 25 can be directly connected, and the power transmission efficiency can be improved. On the other hand, by supplying hydraulic oil to the release chamber 32 and discharging the hydraulic oil from the apply chamber 31, the lockup clutch 30 is switched to a released state in which the lockup clutch 30 is separated from the front cover 22. By controlling the torque converter 12 in such a converter state, the driving force can be transmitted from the pump impeller 23 to the turbine runner 24 via the hydraulic oil, and the torque amplification function of the torque converter 12 can be used. Become. Furthermore, by adjusting the hydraulic pressure in the apply chamber 31 and the release chamber 32, it is possible to switch to a slip state (fastened state) in which the lockup clutch 30 is pressed against the front cover 22 while sliding. By controlling the torque converter 12 in such a slip lock-up state, for example, even when the lock-up clutch 30 is engaged from a low vehicle speed range, it is possible to smoothly switch from the converter state to the lock-up state. .

  The speed change mechanism 14 that changes the driving force input from the torque converter 12 includes a plurality of planetary gear trains 33 and 34, hydraulic clutches 35 to 37, hydraulic brakes 38 and 39, and the like. By controlling the hydraulic clutches 35 to 37 and the hydraulic brakes 38 and 39 incorporated in the speed change mechanism 14, the power transmission path from the speed change input shaft 13 to the speed change output shaft 15 can be switched. As a result, the driving force can be shifted and transmitted from the shift input shaft 13 to the shift output shaft 15. The illustrated transmission mechanism 14 has four forward speeds and one reverse speed.

  In order to control the supply of hydraulic fluid to the apply chamber 31, release chamber 32, hydraulic clutches 35 to 37, hydraulic brakes 38, 39, etc., a valve unit 40 incorporating a plurality of solenoid valves is provided in the mission case 28. ing. Further, an oil pump 41 driven by the engine 11 is provided in the mission case 28 in order to supply hydraulic oil to the valve unit 40. Furthermore, an AT control unit (lock-up determination means, downshift control means) 42 that outputs a control signal to the valve unit 40 is provided to control the operation state of the valve unit 40. The AT control unit 42 includes a CPU that calculates various control signals, a ROM that stores various control data and control programs, a RAM that temporarily stores data, and the like. Further, as sensors for inputting a signal to the AT control unit 42, an accelerator opening sensor 43 that detects an accelerator opening that is a depression amount of an accelerator pedal, a vehicle speed sensor 44 that detects a vehicle speed, and an ATF temperature that detects a temperature of hydraulic oil. A sensor 45, an inhibitor switch 46 for detecting the travel range selected by the select lever, an engine speed sensor 47 for detecting the engine speed, a turbine speed sensor 48 for detecting the speed of the turbine shaft 26, and the like are provided. . The accelerator opening detected by the accelerator opening sensor 43 is a signal indicating the magnitude of the engine load.

  Subsequently, the shift control executed by the AT control unit 42 will be described. 2 and 3 are diagrams showing an example of the shift pattern. FIG. 2 shows a first shift pattern used in a lockup state and a slip lockup state, and FIG. 3 shows a second shift pattern used in a converter state. Thus, the first shift pattern used in the lock-up state and the slip lock-up state and the second shift pattern used in the converter state are set separately. In the following description, the lock-up state and the slip lock-up state are collectively referred to as a lock-up state.

  As shown in FIG. 2, the first shift pattern referred to in the lockup state includes an upshift line U2 that permits an upshift from the first speed to the second speed, and an increase from the second speed to the third speed. An upshift line U3 for permitting a shift and an upshift line U4 for permitting an upshift from the third speed to the fourth speed are set. The first shift pattern includes a first downshift line Da3 that permits a downshift from the fourth speed to the third speed, and a first downshift line Da2 that permits a downshift from the third speed to the second speed. A first downshift line Da1 that permits a downshift from the second speed to the first speed is set.

  These upshift lines U2 to U4 and downshift lines Da1 to Da3 are set based on the vehicle speed and the accelerator opening. The upshift and downshift of the speed change mechanism 14 are executed by referring to the upshift lines U2 to U4 and the downshift lines Da1 to Da3 based on the vehicle speed and the accelerator opening that change according to the driving state. It will be. For example, as shown by the arrow α in FIG. 2, in the process of increasing the vehicle speed while the accelerator opening is constant, the upshift from the first speed to the second speed is executed when the upshift line U2 is exceeded. (Reference A), an upshift from the second speed to the third speed is executed when the upshift line U3 is exceeded (reference B), and from the third speed to the fourth speed when the upshift line U4 is exceeded. Upshift is performed (reference C). Further, as shown by an arrow β in FIG. 2, in the process of decreasing the vehicle speed while the accelerator opening is constant, the downshift from the fourth speed to the third speed is executed when the downshift line Da3 is exceeded. (Reference D), when the downshift line Da2 is exceeded, a downshift from the third speed to the second speed is executed (reference E), and when the downshift line Da1 is exceeded, from the second speed to the first speed. Downshift is performed (reference F). Note that the shift control when the vehicle speed changes has been described, but the shift control is executed according to the upshift lines U2 to U4 and the downshift lines Da1 to Da3 even when the accelerator opening is increased or decreased as well as the vehicle speed. Needless to say.

  As shown in FIG. 3, the above-described upshift lines U2 to U4 are set in the second shift pattern referred to in the converter state. The second shift pattern includes a second downshift line Db3 that permits a downshift from the fourth speed to the third speed, and a second downshift line Db2 that permits a downshift from the third speed to the second speed. A second downshift line Db1 that permits a downshift from the second speed to the first speed is set. The downshift line Db1 is set at a lower accelerator opening and higher vehicle speed than the downshift line Da1, and the downshift line Db2 is set at a lower accelerator opening and higher vehicle speed than the downshift line Da2, and the downshift line Db3 Is set at a lower accelerator opening and higher vehicle speed than the downshift line Da3. Thus, the second shift pattern used in the converter state is a shift pattern in which a downshift is more easily performed than the first shift pattern used in the lockup state.

  For example, as indicated by the same arrow β in FIG. 3 in FIG. 3, in the process of decreasing the vehicle speed while the accelerator opening is constant, the downshift from the fourth speed to the third speed when the downshift line Db3 is exceeded. When the shift is executed (reference G), the downshift from the third speed to the second speed is executed when the downshift line Db2 is exceeded (reference H), and from the second speed when the downshift line Db1 is exceeded. Downshifting to the first speed is executed (symbol I). As described above, the downshift timing (reference symbols G, H, I) in the converter state is earlier than the downshift timing (reference symbols D, E, F) in the lockup state.

  Next, effects obtained by setting the downshift lines Db1 to Db3 to be lower in accelerator opening and higher in the vehicle speed side than the downshift lines Da1 to Da3 will be described. Here, FIG. 4 is an explanatory view showing the operating state of the engine 11. In FIG. 4, characteristic lines Ac <b> 1 to Ac <b> 8 indicate the accelerator opening, and characteristic lines F <b> 1 to F <b> 4 indicate fuel consumption rate contours of the engine 11. FIG. 4 shows the operating state of the engine 11 in the running state X (vehicle speed V2, accelerator opening degree Ac3, fourth speed, lock-up state) shown in FIG.

  First, when the vehicle speed is V2 and the accelerator opening is Ac3, a lockup control map (not shown) is referred to based on the vehicle speed V2 and the accelerator opening Ac3, and the lockup clutch 30 is based on the lockup control map. Is controlled to a fastening state. In such a lock-up state, since the shift control is executed according to the first shift pattern, the fourth speed is selected in the traveling state X in which the vehicle speed is reduced from V1 to V2. Here, the characteristic line L4 in FIG. 4 is an output torque characteristic line when the torque converter 12 is in the lock-up state, the vehicle speed is V2, and the gear position is the fourth speed. That is, as shown in FIG. 4, the engine 11 is operated in the operating state A in the traveling state X. As described above, in the lock-up state in which the lock-up clutch 30 is engaged, the torque converter efficiency is extremely high. Therefore, the first state of FIG. Shift control is executed according to the shift pattern. The torque converter efficiency is obtained by multiplying the speed ratio (output rotational speed / input rotational speed) of the torque converter 12 and the torque ratio (output torque / input torque).

  Here, the engagement control of the lock-up clutch 30 is usually executed with reference to a predetermined lock-up control map based on the vehicle speed and the accelerator opening, but when a predetermined lock-up release condition is satisfied. The lockup clutch 30 is forcibly switched to the released state regardless of the vehicle speed or the accelerator opening. The lock-up release condition is that the coolant temperature of the engine 11 is a predetermined temperature or lower, the hydraulic oil temperature is a predetermined temperature or lower, the hydraulic oil temperature is a predetermined temperature or higher, and the slip lock-up state is a predetermined time. For example, a sudden acceleration state of the vehicle is detected, and a high load state of the engine 11 is detected.

  That is, when the vehicle is traveling in the traveling state X of FIG. 2, if a predetermined lockup release condition is satisfied, the lockup clutch 30 is switched from the engaged state to the released state. Here, in the control device of the present invention, the first shift pattern used in the lock-up state and the second shift pattern used in the converter state are set separately. For this reason, when the AT control unit 42 determines that the lockup clutch 30 is in the released state, the shift pattern to be referred to is switched from the first shift pattern to the second shift pattern. As shown in FIG. 3, the downshift line Db3 of the second shift pattern is set at a lower accelerator opening and higher vehicle speed than the downshift line Da3 of the first shift pattern. Along with the release, in the running state X, a downshift from the fourth speed to the third speed is executed. The AT control unit 42 determines the operating state of the lockup clutch 30 based on the operating state of the valve unit 40, but determines the operating state of the lockup clutch 30 based on the engine speed and the turbine speed. You may let them.

  Here, the characteristic line C4 in FIG. 4 is an output torque characteristic line when the torque converter 12 is in the converter state, the vehicle speed is V2, and the shift speed is the fourth speed. A characteristic line C3 in FIG. 4 is an output torque characteristic line when the torque converter 12 is in the converter state, the vehicle speed is V2, and the shift speed is the third speed. That is, when the downshift from the fourth speed to the third speed is executed in the running state X in association with the release of the lockup clutch 30, the operating state of the engine 11 is changed from the state A to the state as shown in FIG. It will move to B. On the other hand, when the downshift line is not changed according to the operation state of the lockup clutch 30 as in the prior art, the lockup clutch 30 is released in accordance with the establishment of the lockup release condition. Since the state X does not change, the shift speed is maintained at the fourth speed. As described above, when the lockup clutch 30 is released but the fourth speed is maintained, the operating state of the engine 11 is shifted from the state A to the state C as shown in FIG.

  Here, FIG. 5 is a diagram showing the torque converter efficiency. In FIG. 5, a characteristic line Te3 is a characteristic line indicating the torque converter efficiency when the shift speed is the third speed, and a characteristic line Te4 is a characteristic indicating the torque converter efficiency when the shift speed is the fourth speed. Is a line. Further, the characteristic lines L4, C3, C4 and the characteristic line Ac3 shown in FIG. 5 are the same as the characteristic lines shown in FIG.

  As described above, when the downshift is executed from the fourth speed to the third speed by switching the shift pattern along with the release of the lockup clutch 30, the operating state of the engine 11 becomes the state B. When the characteristic line Te3 is referred to based on the engine speed in the operating state B, it is confirmed from the characteristic line Te3 that the torque converter efficiency is E2. On the other hand, when the fourth speed is maintained without switching the shift pattern as the lock-up clutch 30 is released as in the prior art, the operating state of the engine 11 becomes the state C. When referring to the characteristic line Te4 based on the engine speed in the operating state C, it is confirmed from the characteristic line Te4 that the torque converter efficiency is E2 lower than E1. Thus, when the lock-up clutch 30 is released, it is possible to obtain higher torque converter efficiency by performing a downshift at an earlier timing than when maintaining a high gear position, and the vehicle fuel efficiency The performance can be improved.

  As described above, in the lock-up state and the slip lock-up state in which the lock-up clutch 30 is engaged, the speed ratio of the torque converter 12 approaches 1, so that the torque converter efficiency is extremely high. For this reason, the engine 11 is selected in a region where the fuel consumption rate of the engine 11 is good by selecting the highest possible gear position based on the downshift lines Da1 to Da3 set on the high accelerator opening and on the low vehicle speed side. Like to drive. Thereby, in the lock-up state and the slip lock-up state, the torque converter efficiency and the fuel consumption rate can be kept good, so that the fuel efficiency performance of the vehicle can be improved.

  In the converter state in which the lock-up clutch 30 is released, a large slip occurs and the speed ratio of the torque converter 12 decreases, so that the torque converter efficiency is low. For this reason, on the basis of the downshift lines Db1 to Db3 set to the low accelerator opening and the high vehicle speed side, the downshift is executed at an early timing, thereby avoiding the low speed ratio region of the torque converter 12 and The converter efficiency is improved. As a result, even in a converter state with low torque converter efficiency, the torque converter efficiency can be improved by an early downshift, so that the fuel efficiency of the vehicle can be improved.

  In the above description, the upshift line and the downshift line are set based on the vehicle speed and the accelerator opening, but the upshift line and the downshift line may be set based on the vehicle speed and the throttle opening. . In this case, the downshift lines Db1 to Db3 of the second shift pattern are set to a lower throttle opening (low engine load) and higher vehicle speed side than the downshift lines Da1 to Da3 of the first shift pattern. It will be. Here, the throttle opening is an opening of a throttle valve provided in the intake system of the engine 11 and is a signal indicating the magnitude of the engine load.

  It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. For example, in the illustrated case, the downshift lines Db1 to Db3 are partially set to the low accelerator opening and the high vehicle speed side with respect to the downshift lines Da1 to Da3. ˜Db3 may be set to a low accelerator opening degree and a high vehicle speed side with respect to the downshift lines Da1 to Da3. In the illustrated case, three downshift lines Da1 to Da3 and Db1 to Db3 are set for each shift pattern. However, the number of downshift lines may be changed in accordance with the shift speed. Needless to say. Furthermore, in the above description, the first downshift lines Da1 to Da3 and the second downshift lines Db1 to Db3 are set in advance, but the first downshift line and the second downshift line are appropriately set according to the situation. You may make it calculate.

  In the illustrated case, the same upshift lines U2 to U4 are set for the first shift pattern and the second shift pattern, but the present invention is not limited to this, and the upshift lines U2 to U4 are not limited to this. The shift line may be set separately.

  In the above description, the present invention is applied to the planetary gear type automatic transmission 10. However, the present invention is not limited to this, and the present invention may be applied to a parallel shaft type automatic transmission. The present invention may be applied to a continuously variable transmission that is an automatic transmission.

1 is a skeleton diagram showing an automatic transmission to which an automatic transmission control device according to an embodiment of the present invention is applied. FIG. It is a diagram which shows an example of a shift pattern. It is a diagram which shows an example of a shift pattern. It is explanatory drawing which shows the driving | running state of an engine. It is a diagram which shows torque converter efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Automatic transmission 11 Engine 12 Torque converter 14 Transmission mechanism 22 Front cover (input element)
25 Turbine hub (output element)
30 Lock-up clutch 42 AT control unit (lock-up determination means, down-shift control means)
Da1-Da3 downshift line (first downshift line)
Db1 to Db3 Downshift line (second downshift line)

Claims (3)

Follow the shift pattern is set based on the vehicle speed and the engine load, a control apparatus for an automatic transmission for performing a speed change control by switching the gear position,
A torque converter provided between the engine and the transmission mechanism and transmitting engine power to the transmission mechanism;
A lock-up clutch provided between an input element and an output element of the torque converter and operating in an engaged state and a released state;
Lock-up determination means for determining an operating state of the lock-up clutch;
Downshift control means for performing a downshift of the transmission mechanism when at least one of the vehicle speed and the engine load changes beyond a downshift line in the shift pattern;
The downshift control means performs a downshift based on a predetermined first downshift line when the lockup clutch is in an engaged state, while when the lockup clutch is in a released state, A control device for an automatic transmission, wherein a downshift is executed based on a second downshift line set at a lower engine load and higher vehicle speed than the first downshift line. The control device for an automatic transmission according to claim 1,
The control device for an automatic transmission, wherein the engine load is expressed by at least one of an accelerator opening and a throttle opening. The control apparatus for an automatic transmission according to claim 1 or 2,
The automatic transmission control device according to claim 1, wherein the engagement state of the lockup clutch includes a slip state in which the input element and the output element are coupled while sliding the lockup clutch.

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