JP4939555B2 - Control device for lock-up clutch - Google Patents

Description

  The present invention relates to a torque converter disposed between an output shaft of an engine and an input shaft of an automatic transmission, and a lockup clutch provided in the torque converter and capable of mechanically coupling the output shaft and the input shaft. And a lock-up clutch control device including a lock-up clutch fastening control means for fastening the lock-up clutch at a predetermined hydraulic pressure in a predetermined operating range determined according to a throttle opening and a vehicle speed.

Using the vehicle speed and throttle opening as parameters, the shift map that defines the upshift line and downshift line for each shift stage of the automatic transmission has been shifted to the low throttle opening side with a predetermined downshift line and its downshift line. The slip start line defines the slip region of the lockup clutch, and the lockup clutch is slip controlled when the throttle opening enters the slip region before the start of downshifting, thereby reducing shift shock and fuel consumption. Patent Document 1 listed below is known to achieve both reduction in rate.
JP 2008-180299 A

  By the way, the above conventional ones are: The slip-up control of the lock-up clutch before the start of the downshift aims to reduce both the shift shock and the fuel consumption rate, but the slip state of the lock-up clutch after the start of the downshift also changes the shift shock and the fuel consumption rate. Is known to affect.

  That is, if the lockup clutch is maintained in the engaged state during the downshift, the fuel consumption rate is reduced because no slip occurs. On the other hand, if the lockup clutch is maintained in the slipped state during the downshift, the shift shock is alleviated. However, not only does the fuel consumption rate increase, but the engine speed after shifting is increased due to the slip of the lock-up clutch, so if the engine speed is prevented from entering the red zone, the limit vehicle speed for downshifting is reduced. There is a problem that decreases.

  The present invention has been made in view of the above-described circumstances, and aims to achieve both reduction of shift shock and reduction of fuel consumption rate by controlling a lock-up clutch during downshifting, and increase the limit vehicle speed for downshifting. Objective.

  To achieve the above object, according to the first aspect of the present invention, there is provided a torque converter disposed between an output shaft of an engine and an input shaft of an automatic transmission, and the output provided in the torque converter. A lockup clutch capable of mechanically coupling a shaft and the input shaft, and a lockup clutch fastening control means for fastening the lockup clutch at a predetermined hydraulic pressure in a predetermined operating range determined according to a throttle opening and a vehicle speed The lock-up clutch fastening control means includes a lock-up clutch engagement control means that operates the lock-up clutch at a standby hydraulic pressure lower than a tight hydraulic pressure at which the lock-up clutch is completely engaged simultaneously with the start of shifting at the time of downshifting. In addition to slip control, the gear ratio during shifting reaches a predetermined value and shifting Control of the lockup clutch, wherein the lockup clutch is engaged with the tight hydraulic pressure when the speed ratio of the torque converter falls below the target speed ratio from the time when the shift is determined until the shift is completed. A device is proposed.

  According to the invention described in claim 2, in addition to the configuration of claim 1, a shift map that defines a downshift line of the automatic transmission according to the throttle opening and the vehicle speed is provided. A lockup clutch control device is proposed in which the shift-down limit vehicle speed of the shift map is changed in accordance with the engagement state of the lockup clutch.

  The electronic control unit U of the embodiment corresponds to the lockup clutch engagement control means of the present invention.

  According to the configuration of claim 1, the lock-up clutch fastening control means slip-controls the lock-up clutch at a standby hydraulic pressure lower than the tight hydraulic pressure at which the lock-up clutch is completely fastened simultaneously with the start of shifting at the time of downshifting. The lockup clutch is engaged with tight hydraulic pressure when the speed ratio of the torque converter falls below the target speed ratio from when it is determined that the gear ratio has reached a predetermined value and the gear shift has progressed until the gear shift is completed. Therefore, while slipping the lock-up clutch during gear shifting to reduce gear shift shock, the lock-up clutch is quickly fastened to reduce fuel consumption and engine speed at the end of gear shifting. It is possible to protect the engine by suppressing an unnecessary rise.

  According to the second aspect of the present invention, the shift down limit vehicle speed of the shift map defining the downshift line of the automatic transmission is changed according to the engagement state of the lockup clutch immediately before the downshift. Even if a shift occurs in the lock-up clutch engagement timing during the shift-down due to the engagement state of the up-clutch, the engine speed is excessive due to the amount of increase in the engine speed after the shift-down caused by the shift in advance. It is possible to increase the vehicle speed at which the downshift is started within a range that does not become (shift down limit vehicle speed) as much as possible.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 4 show an embodiment of the present invention. FIG. 1 is an explanatory diagram of the structure of a torque converter having a lock-up clutch, FIG. 2 is a diagram showing a shift map of an automatic transmission, and FIG. 3 is a shift diagram. FIG. 4 is a time chart for explaining the control of the lockup clutch at the time of downshifting.

  As shown in FIG. 1, the torque converter T includes a pump impeller 12 connected to an output shaft 11 (crankshaft) of an engine E, a turbine runner 14 connected to an input shaft 13 (main shaft) of an automatic transmission M, A stator 17 supported by a casing 15 via a one-way clutch 16 and a lockup clutch 18 capable of coupling the pump impeller 12 and the turbine runner 14 are provided.

  When the pump impeller 12 connected to the output shaft 11 of the engine E rotates, the oil pushed out from the pump impeller 12 in the direction of the arrow flows into the turbine runner 14 and gives torque to the turbine runner 14 to input the input shaft of the automatic transmission M. After rotating 13, the rotation of the output shaft 11 of the engine E is transmitted to the input shaft 13 of the automatic transmission M by passing through the stator 17 and returning to the pump impeller 12.

  The lock-up clutch 18 includes a clutch piston 20 that can contact the inner surface of the torque converter cover 19, and a first oil chamber 21 and a second oil chamber 22 are formed on both sides of the clutch piston 20. The hydraulic control means 23 for supplying the control hydraulic pressure of the lockup clutch 18 to the first and second oil chambers 21 and 22 is composed of a hydraulic pump and a hydraulic control valve, and includes a vehicle speed V, an engine speed NE, and a torque converter T. Control is performed by an electronic control unit U (lock-up clutch engagement control means) to which a speed ratio, a gear ratio of the automatic transmission M, and the like are input.

  When hydraulic pressure is supplied to the first oil chamber 21 and the facing 20a of the clutch piston 20 contacts the inner surface of the torque converter cover 19, the lockup clutch 18 is engaged and the torque of the output shaft 11 of the engine E is directly applied to the automatic transmission M. To the input shaft 13. When hydraulic pressure is supplied to the second oil chamber 22 and the facing 20a of the clutch piston 20 is separated from the torque converter cover 19, the lockup clutch 18 is released and the output shaft 11 of the engine E and the input shaft of the automatic transmission M are disconnected. The mechanical connection is interrupted. Further, by controlling the differential pressure between the first and second oil chambers 21 and 22, the torque converter cover 19 and the facing 20 a of the clutch piston 20 are slipped so that the speed ratio of the torque converter T (the rotation of the output shaft 13). Number / number of rotations of the input shaft 11) can be arbitrarily controlled.

  FIG. 2 shows a shift map of a forward five-speed automatic transmission M, which defines the timing of upshifting and downshifting between the respective shift stages using the vehicle speed on the horizontal axis and the throttle opening on the vertical axis as parameters. 1st-2nd upshift line shown by solid line, 2nd-3rd upshift line, 3rd-4th upshift line, 4th-5th upshift line and corresponding shift when vehicle speed and throttle opening cross The 5th speed-4th speed downshift line, 4th speed-3rd speed downshift line, 3rd speed-2nd speed downshift line and 2nd speed-1st speed downshift line indicated by broken lines The corresponding downshift occurs when crossing.

  The shift map includes a fourth-speed and fifth-speed engagement line (refer to a one-dot chain line) of the lock-up clutch 18 of the torque converter T, and a fourth-speed and fifth-speed engagement release line (second line) of the lock-up clutch 18 of the torque converter T. Dotted line reference). At each gear stage, the lockup clutch 18 is engaged when the vehicle speed and the throttle opening cross the engagement line from left to right, and the lockup clutch 18 is engaged when the vehicle speed and the throttle opening cross the engagement release line from right to left. To release.

  Next, control of the lockup clutch 18 at the time of downshifting from the fifth speed to the fourth speed will be described based on the flowchart of FIG. 3 and the time chart of FIG.

  First, in step S1 of the flowchart of FIG. 3, the 5th-4th speed downshift line in the shift map of FIG. 2 is searched according to the state of the lockup clutch 18. As shown in FIG. 4, the lock-up clutch 18 immediately before the downshift includes an engaged state, a slip control state, and an engaged / released state, and the 5-speed to 4-speed downshift line changes according to these states. . That is, in FIG. 2, the upper part (the part where the throttle opening is large) of the 5th-4th downshift line changes in the left-right direction (increase / decrease direction of the vehicle speed). Specifically, if the lockup clutch 18 immediately before the downshift is in the engaged state, the upper part of the 5th to 4th downshift line is the vehicle speed = V3, and if in the slip control state, the vehicle speed = V2 and in the released state. If there is, vehicle speed = V1 (V1 <V2 <V3).

  In subsequent step S2, when the vehicle speed and throttle opening crosses the 5th-4th gear downshift line from the right to the left and the shift down is started, the hydraulic pressure of the lockup clutch 18 is slightly lower than the engagement release hydraulic pressure in step S3. A high standby oil pressure is set, and the lockup clutch 18 is brought into a slip state (see FIG. 4).

  In subsequent step S4, it is determined whether or not the speed change process is an inertia phase. As shown in FIG. 4, the torque phase in the first half of the shift process is such that, among the shift clutches in each shift stage of the automatic transmission M, the first five-speed clutch changes from the engaged state to the disengaged state, and This is a phase in which the speed clutch changes from the non-engaged state to the engaged state. In the inertia phase in the latter half of the gear shifting process, the front five-speed clutch is disengaged and the rear four-speed clutch is engaged. However, both clutches are still in the slip state. When the inertia phase in the latter half of the speed change process is entered, the speed ratio continuously changes from the speed ratio of the fifth speed gear stage to the speed ratio of the fourth speed gear stage.

  If the shift process is an inertia phase in step S4, it is determined in step S5 whether or not the shift has proceeded. Whether or not the gear shift has progressed is determined when the gear ratio in FIG. 4 reaches a predetermined value between the gear ratio of the fifth speed and the gear ratio of the fourth speed. If it is determined in step S5 that the shift has progressed, the speed ratio of the torque converter T is compared with the target speed ratio in step S6, and it is determined whether the speed ratio has fallen below the target speed ratio.

  As is clear from FIG. 4, the speed ratio of the torque converter T varies depending on the state of the lockup clutch 18 immediately before the downshift. If the lock-up clutch 18 is in the engaged state (speed ratio = 1.00) immediately before the downshift, the speed ratio gradually decreases simultaneously with the start of the downshift and falls below the target speed ratio in the second half of the inertia phase.

  If the lock-up clutch 18 is in an intermediate slip state between the engaged state and the non-engaged state immediately before the downshift (for example, the speed ratio = 0.97 to 0.98), the speed ratio is immediate even when the downshift starts. It does not change and falls rapidly in the middle of the inertia phase and falls below the target speed ratio.

  If the lockup clutch 18 is not engaged immediately before the downshift, the speed ratio is already below the target speed ratio at the start of the downshift, and the speed ratio gradually increases as the downshift progresses.

  Therefore, if the lockup clutch 18 is not engaged immediately before the downshift, the speed ratio of the torque converter T is already below the target speed ratio (see point A) when it is determined that the shift has proceeded, and the downshift is performed. If the lock-up clutch 18 is in the slip state immediately before, the speed ratio of the torque converter T falls below the target speed ratio after a predetermined time from the time when it is determined that the shift has advanced (see point B), and immediately before the downshift. If the lockup clutch 18 is in the engaged state, the speed ratio of the torque converter T falls below the target speed ratio after a predetermined time delay from the time when it is determined that the shift has progressed (see point C).

  When the speed ratio of the torque converter T falls below the target speed ratio, the standby hydraulic pressure that has been maintained at step S8 is increased to a tight hydraulic pressure at which the lockup clutch 18 can be completely engaged at step S7.

  As described above, even if the torque converter T is in the engaged state where the speed ratio = 1 or the slip state where the speed ratio is very close to 1 at the moment when the 5th-4th gear downshift is started, the lockup clutch 18 By reducing the hydraulic pressure to the standby hydraulic pressure so that it can easily slip, the shift shock can be effectively suppressed. When the shift shifts to the inertia phase and the speed ratio falls below the target speed ratio, the hydraulic pressure of the lockup clutch 18 is increased to the tight hydraulic pressure to shift to a completely engaged state, so that the period during which the lockup clutch 18 slips is increased. While suppressing the increase in the fuel consumption rate to the minimum, the lockup clutch 18 can be completely engaged at the end of the downshift to suppress the slip, and an unnecessary increase in the engine speed can be suppressed.

  In this way, since an unnecessary increase in the engine speed at the end of the downshift can be suppressed, the position of the 5th-4th speed downshift line on the high throttle opening side in view of that is shown in FIG. The vehicle can be moved to the right (high vehicle speed side) to increase the limit vehicle speed at which downshifting is possible. That is, in the conventional control of the lockup clutch 18, there is a possibility that the engine speed increases and enters the red zone at the end of the downshift. Therefore, the engine speed is set by setting a lower limit vehicle speed at which the downshift is possible. Although it was prevented from increasing and entering the red zone, according to the present embodiment, the hydraulic pressure of the lockup clutch 18 is increased to a tight hydraulic pressure at an appropriate timing to suppress an unnecessary increase in the engine speed. By doing so, it is possible to increase the limit vehicle speed at which downshifting is possible.

  By the way, in the present embodiment, the limit vehicle speed at which downshifting is possible is changed depending on the state of the lockup clutch 18 at that time. As shown in the upper right part of the 5th-4th speed downshift line in FIG. 2, if the lockup clutch 18 is in the engaged state at the start of the downshifting, the vehicle speed at which the 5th-4th speed downshift is started becomes V3. If the lockup clutch 18 is set in the slip control state, the vehicle speed is set to V2, and if the lockup clutch 18 is in the disengaged state, the vehicle speed is set to V1.

  The reason is as follows. Since the lock-up clutch 18 has relatively low responsiveness to hydraulic control, if the lock-up clutch 18 is in the engaged state at the start of downshifting and a high hydraulic pressure (that is, tight hydraulic pressure) is applied, the hydraulic pressure waits thereafter. Even if it tries to reduce it to the hydraulic pressure, it does not fall, and after that, the pressure increase time when the hydraulic pressure is increased to the tight hydraulic pressure is shortened, and the lockup clutch 18 is quickly engaged, and the increase in the engine speed is suppressed. Is done. Therefore, even if the vehicle speed at the start of the downshift is high (that is, even if the engine speed is high), the engine speed does not enter the red zone at the end of the downshift.

  Conversely, if the lock-up clutch 18 is in the disengaged state at the start of downshifting and a low oil pressure is applied, then the pressure increase time when the oil pressure increases to the tight oil pressure through the standby oil pressure becomes longer and locks. The up-clutch 18 enters the engaged state with a delay, making it difficult to suppress an increase in engine speed. Therefore, if the vehicle speed at the start of the downshift is not set low, the engine speed may enter the red zone at the end of the downshift.

  In this way, by changing the downshift line of the shift map according to the state of the lockup clutch 18 at the start of the downshift, the limit that allows the downshift within the range where the engine speed does not enter the red zone at the end of the downshift. The vehicle speed can be increased to the maximum.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, the fifth embodiment and the fourth gear shift down have been described in the embodiment, but the present invention can also be applied to the shift down of other gear stages.

Explanatory drawing of structure of torque converter with lock-up clutch Diagram showing shift map of automatic transmission Flowchart explaining control of lockup clutch at the time of downshift Time chart explaining lockup clutch control during downshifting

E Engine M Automatic transmission T Torque converter U Electronic control unit (lock-up clutch engagement control means)
11 Engine output shaft 13 Automatic transmission input shaft 18 Lock-up clutch

Claims (2)

A torque converter (T) disposed between the output shaft (11) of the engine (E) and the input shaft (13) of the automatic transmission (M);
A lockup clutch (18) provided in the torque converter (T) and capable of mechanically coupling the output shaft (11) and the input shaft (13);
Lock-up clutch engagement control means (U) for engaging the lock-up clutch (18) with a predetermined hydraulic pressure in a predetermined operating range determined according to the throttle opening and the vehicle speed;
In a control device for a lock-up clutch provided with
The lockup clutch engagement control means (U)
The lockup clutch (18) is slip controlled at a standby hydraulic pressure lower than the tight hydraulic pressure at which the lockup clutch (18) is completely engaged simultaneously with the start of the shift at the time of downshifting, and the gear ratio during the shift reaches a predetermined value. The lockup clutch is engaged with the tight hydraulic pressure when the speed ratio of the torque converter (T) falls below the target speed ratio from when it is determined that the shift has progressed until the shift is completed. A control device for a lockup clutch. A shift map that defines a downshift line of the automatic transmission (M) according to the throttle opening and the vehicle speed;
The control device for a lock-up clutch according to claim 1, wherein a shift-down limit vehicle speed of the shift map is changed according to an engaged state of the lock-up clutch (18) immediately before the downshift.

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