JPH08178053A - Lockup control device for automatic transmission - Google Patents

Abstract

PURPOSE: To suppress the decrease of the fuel consumption improving effect due to lockup and prevent an engine stall at the time of a quick brake. CONSTITUTION: This lockup control device is provided with a lockup control requirement judging means 31, a low-μ road judging means 32, a target differential rotation setting means 33 setting the differential rotation quantity of a lockup clutch to the target value causing no engine stall due to the drag at the time of a quick brake based on the lockup control judgment and low-μ road judgment, and a differential rotation control means 34 controlling the input side and output side of a torque converter 12 to the set differential rotation quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lockup control device for an automatic transmission, and more particularly to a control device for slip control of a lockup clutch provided in a torque converter of an automatic transmission.

[0002]

2. Description of the Related Art Conventionally, a vehicle automatic transmission is provided with a lock-up clutch attached to a torque converter as its starting device. This lockup clutch is locked up when the vehicle is traveling at high speed in order to improve the fuel consumption by eliminating the power transmission loss due to the slip of the fluid in the torque converter section. In addition to the control to extend the lockup region to the lower vehicle speed side, a low throttle is used to improve fuel efficiency by suppressing a sharp decrease in engine rotation during coast and prolonging the fuel cut time. Slip control at low vehicle speed at the opening is also performed.

By the way, if the lockup clutch is operated during coasting as described above, the engine may stall during sudden deceleration when traveling on a low μ road where wheel lock is likely to occur. In order to deal with such a problem, conventionally, a technique has been proposed in which deceleration of a vehicle is detected and control is performed to forcibly release the lockup clutch when the deceleration is equal to or more than a predetermined value (Japanese Patent Laid-Open No. 336067/1992).
(See the official gazette).

[0004]

However, in the lock-up release control by detecting the deceleration of the vehicle as in the above proposal, in the case of extremely rapid braking such as panic braking on a frozen road or a snowy road. , The possibility of engine stall due to delay in release cannot be denied. Therefore, in order to expedite the release of the lockup clutch, it is not unthinkable to set the slip amount of the lockup clutch, that is, the differential rotation amount in advance, but in such a case, the engine rotation during coasting as described above is This will reduce the fuel consumption improvement effect of suppressing the sudden decrease and lengthening the fuel cut time.

The present invention has been devised in view of the above circumstances, and determines the low μ road itself, which is apt to cause engine stall due to wheel lock, and is limited to when traveling on the low μ road.
A main object of the present invention is to provide a lock-up control device for an automatic transmission that prevents engine stall during sudden braking while suppressing a decrease in fuel consumption improving effect due to lock-up by generating a predetermined differential rotation amount. Further, according to the present invention, by limiting the time when the predetermined rotational speed difference is generated, when traveling on a low μ road under lockup slip control,
A further aim is to prevent engine stalls in response to emergency braking while minimizing the reduction in fuel consumption improvement effect due to lockup.

[0006]

In order to solve the above-mentioned problems, the lock-up control device of the present invention is designed so that the input side is connected to the output shaft of the engine and the output side is connected to the input shaft of the transmission. And a transmission, and in an automatic transmission having a lockup clutch that directly connects the output shaft of the engine and the input shaft of the transmission, it is determined whether lockup control is performed depending on the running state of the vehicle. Lockup control request determining means, low μ road determining means for determining whether or not the road surface is a low μ road, lockup control determination by the lockup control request determining means, and low μ road by the low μ road determining means Based on the judgment, a target differential rotation setting means for setting a target value of the differential rotation amount on the input side and the output side of the lockup clutch, and controlling the lockup clutch to the set differential rotation amount. Characterized in that it comprises a rotation control means.

Next, the present invention relates to a torque converter having an input side connected to an output shaft of an engine and an output side connected to an input shaft of a transmission, the torque converter being arranged between the engine and the transmission. A lock-up clutch that directly connects the input side and the output side of the torque converter, an on-side oil chamber to which an on-pressure for engaging the lock-up clutch is supplied, and an off-pressure for releasing the lock-up clutch are supplied. An off-side oil chamber, and a lock-up control valve that slip-controls the lock-up clutch by controlling the differential pressure between the on-pressure supplied to the on-side oil chamber and the off-pressure supplied to the off-side oil chamber. In a lock-up control device for an automatic transmission, which has lock-up slip control request determining means for determining whether or not to perform lock-up slip control depending on a running state of a vehicle; Based on the low μ road judgment means for judging whether or not there is a possibility of a low μ road, the lockup slip control judgment by the lockup slip control request judgment means, and the low μ road judgment by the low μ road judgment means. ,
Target differential rotation setting means for setting a large target value of the differential rotation amount of the lockup clutch, and differential rotation for controlling the lockup control valve so that the input side and the output side of the torque converter have the set differential rotation amount. And a control means.

[0008]

According to the present invention having such a structure, when the vehicle reaches the low μ road under the lock-up control, the low μ road judging means judges this and the target difference rotation setting means. Sets the target value of the differential rotation amount between the input side and the output side of the lockup clutch to a value corresponding to low μ road traveling, and controls the lockup clutch to the differential rotation amount set by the differential rotation control means. The operation is performed. Therefore, according to the present invention, the differential rotation amount corresponding to sudden braking is reduced to a low μ.
Since it can be limited to only when traveling on the road, it is possible to more reliably prevent engine stall during rapid deceleration on any road surface while suppressing a decrease in the fuel efficiency improving effect obtained by the lockup control.

According to the second aspect of the present invention, when the vehicle reaches the low μ road running under the lock-up slip control, the low μ road judging means judges the possibility, and the target difference rotation setting means makes it possible. The target value of the differential rotation amount of the lock-up clutch is set to a large value corresponding to running on a low μ road than that during normal lock-up slip control, and the difference between the input side and output side of the torque converter set by the differential rotation control means. An operation is performed to control the lockup control valve so that the rotation amount is achieved. Therefore, according to this configuration, since the setting of the large differential rotation amount corresponding to the sudden braking can be limited only to the low μ road traveling under the lockup slip control, the fuel consumption improving effect obtained by the lockup slip control is reduced. It is possible to more reliably prevent engine stall during sudden deceleration on any road surface while suppressing

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an automatic transmission having a gear train of four forward speeds and one reverse speed for a front engine front drive vehicle will be described with reference to the drawings. As conceptually shown in FIG. 1, an automatic transmission 1 includes a torque converter 12 having a lockup clutch 11 to be controlled according to the present invention, and a lockup clutch 1.
The lockup control means (in this example, the lockup control circuit 13a in the hydraulic control circuit 13) for engaging and disengaging 1 is provided, and by controlling the engaging force of the lockup clutch 11, the torque converter that contacts the input side thereof. The input rotations of the 12 pump impellers 121 and the output rotations of the turbine runner 122, which corresponds to the output side, are slip-controlled to a predetermined differential rotation amount.

In the present specification, the lock-up control circuit 13a, the control unit 3 for signal-controlling the solenoid valve in the lock-up control circuit 13a, and the control program incorporated therein are collectively referred to as a lock-up control device. Further, in FIG. 1, reference character E is an engine, C is its crankshaft, SN1 is a throttle sensor for detecting the throttle opening θ of the engine E, and SN2 is the rotational speed N _{E of the} engine _E.
The engine speed sensor for detecting SN3 is the automatic transmission 1
Input rotation sensor for detecting the input rotation speed Nin of SN4
Is an output rotation sensor for detecting the output rotation speed Nout, and SN5 is an AT for detecting the automatic transmission hydraulic oil temperature T _A.
An oil temperature sensor, SN6 is an intake air temperature sensor that detects the engine intake air temperature T _I , SN7 is a water temperature sensor that detects the engine cooling water temperature T _W , and SN8 is an outside air temperature sensor that detects the outside air temperature T.

As shown in detail in FIG. 5, the lock-up control device refers to map data in the control unit 3 to determine whether or not the lock-up slip control is to be performed depending on the running state of the vehicle, with reference to the engine speed N _E. The lock-up slip control request determination means 31 for determining according to the throttle opening θ, and whether or not the road surface may be a low μ road,
In this example, the low μ road determination unit 32 that makes a determination based on the temperature information detected by the various sensors SN5 to SN8 or a combination thereof, the lockup slip control request determination unit 31 and the low μ road determination. Based on the low μ road judgment by the means 32, the target differential rotation setting means 33 for setting a large target value of the differential rotation amount of the lockup clutch 11 with reference to the map data, and the input side and the output side of the torque converter 12 are set. Lock-up control valve 13 to be described later so that the set differential rotation amount is achieved.
2 and a differential rotation control means 34 for controlling 2. The differential rotation detecting means shown in the figure is equivalent to the sensors SN2 and SN3.
And constitutes a confirmation means for achieving the target differential rotation speed.

Returning to FIG. 1, each part will be described in detail. The gear train of the automatic transmission 1 is a main transmission unit 1 in which two planetary gear units are combined.
4 and an underdrive planetary gear unit 15. The sun gears 141, 144 of the main transmission unit 14 are connected to each other and the brake B
It is fixable to the transmission case 100 via 1 and to the case 100 via a one-way clutch F1 and a brake B2 connected in series. The front stage ring gear 143 is connected to the sun gear 1 via the clutch C1.
41 are connected to the input shaft 101, which is connected to the turbine shaft, via the clutch C2. The front stage carrier 142 and the rear stage ring gear 146 are connected to the output shaft 102. The carrier 145 at the rear stage can be fixed to the transmission case 100 via the brake B3 and the one-way clutch F2 which are arranged in parallel.

On the other hand, the ring gear 153 of the underdrive planetary gear unit 15 includes a counter shaft 103 and counter gears 149, 1 in the main transmission unit 14.
An input element connected via 50 and a carrier 152
And the sun gear 151 are connected via a clutch C3,
The sun gear 151 can be fixed to the transmission case 100 via the one-way clutch F3 and the brake B4 that are arranged in parallel, and the carrier 152 is the differential gear 1
6 is connected to the output gear 154.

In the gear train having the above structure, the clutch C3 of the underdrive planetary gear unit 15 is used.
The input that enters the ring gear 143 due to the engagement of the clutch C1 of the main transmission unit 14 under the underdrive rotation by the release and the engagement of the brake B4 is supported by the reaction force of the carrier 145 due to the engagement of the one-way clutch F2.
6 rotations is output as the first speed, the sun gear 141 is fixed by the engagement of the brake B2 and is output as the rotation of the carrier 142 at the second speed, and the ring gear 143 and the sun gear 141 are rotated at the same speed by the additional engagement of the clutch C2. When the main transmission unit 14 is directly connected, the input rotation is output from the carrier 142 as it is, and the fourth speed is achieved when the underdrive planetary gear unit 15 is directly connected by the engagement of the clutch C3 and the clutch C2 is engaged. , Brake B3 is engaged to input sun gear 144, carrier 14
The reverse is achieved by the reverse rotation of the ring gear 146 fixed to 5.

FIG. 2 shows the operation of the above-mentioned clutches and brakes and one-way clutch (abbreviated as OWC in the figure) at each shift position, and the shift speeds achieved thereby, from the first speed (1st) to the fourth speed (4th). The relationship is summarized and shown in a diagram. In the figure, "P" is purging,
"R" is reverse, "N" is neutral, "D" is drive, "2" is second, and "L" is low.

The hydraulic control circuit 13 of the automatic transmission 1 as a whole is
In addition to a shift control circuit including various valves for controlling hydraulic pressure supply to a servo that engages each clutch and brake for the above shift, a lock-up control circuit 13a separately shown in FIGS. 3 and 4 is provided. There is. This circuit, as shown in FIG. 3, the oil pump (PUMP) the line pressure P _L by regulating a hydraulic pressure source, a primary regulator valve 134 that outputs a secondary pressure P _S, further to the low pressure secondary pressure P _S A secondary regulator valve 135 that regulates the pressure to be supplied to each lubrication unit (LUBE) and a solenoid modulator valve 136 that modifies the line pressure P _L and supplies the line pressure P _L to the linear solenoid valve 131 are provided.

The lock-up control valve 132 (current duty ratio) is output by the signal I _D (current duty ratio) output from the control unit 3 (see FIG. 1), using the hydraulic pressure supplied from each pressure regulating valve shown in FIG. 3 as a base pressure. (As shown in FIG. 4), the linear solenoid valve 131 for adjusting the signal pressure P _SLU to be applied to the linear solenoid valve 131 and the hydraulic pressure supplied to the brake B2 as shown in FIG. Of the solenoid relay valve 137 for applying to the lock-up control valve 132, and the signal pressure P _SLU from the valve 137, the differential pressure between the on-side oil chamber 123 and the off-side oil chamber 124 before and after the clutch plate of the lock-up clutch 11. Control valve 132 for controlling the lockup and lockup relay valve 1 for switching the lockup on / off
And 33.

The lockup control circuit 13 thus configured
In a, the secondary pressure P _S is in the path indicated by the mark ● in FIG. 4, and the lockup relay valve 133 is imported 1
It is always supplied to 33a. This lockup relay valve 1
33 applies the signal pressure P _SLU output from the linear solenoid valve 131 to the spool end in opposition to the spring load, whereby the lock-up on position shown in the left half of the figure to the lock-up on position shown in the right half. It switched, by supplying the lock-up on (L-upON) oil passage to the torque converter 12 from the secondary pressure P _S port 133b that is provided to import 133a along the path shown denoted by the ● figure lockup The engagement pressure, that is, the secondary pressure P _S is applied to the rear on-side oil chamber 123 of the clutch plate of the clutch 11.

On the other hand, lock-up off (L-up OF
F) The return oil from the oil passage is locked by the route marked with a circle in the figure.
Guided to the port 133c of the backup relay valve 133, the valve
Route marked with a circle from the outport 133d through the inside
Lockup control valve 132 port 132b
From the drain port 132e through the valve oil passage.
Is discharged. At this time, the control unit shown in FIG.
Signal I output from _DIf the current duty ratio is 100
Output from the linear solenoid valve 131
Signal pressure P_SLUBecomes high pressure, and this
Applied to the large diameter part of the plunger 132c of the trawl valve 132
Therefore, both ports 132a and 132b of the valve 132 are
Supply pressure Ps and return pressure P via_DThe communication of the valve 132
It is blocked by the spool 132d of the
The differential pressure across the clutch plate of the latch 11 is kept high.

The signal S output from the control unit 3
When the duty ratio of the D current is a predetermined value, the output signal pressure P _SLU from the linear solenoid valve 131 also has a predetermined value corresponding thereto, and the lockup control valve 132 is applied by applying the spring load and the lockup engagement pressure. The spool 132d adjusts the communication between the supply pressure Ps and the return pressure P _D between the ports 132a and 132b.
Since the return of the lock-up control valve 132 via the lock-up control valve 132 occurs, the differential pressure across the clutch plate of the lock-up clutch 11 is maintained at a predetermined value required for slip control.

When the duty ratio of the current output from the control unit 3 is set to 0, the linear solenoid valve 13
The output signal pressure P _SLU from 1 is 0, that is, since the output signal pressure is drained by the valve 131, the signal pressure application to the lockup control valve 132 and the lockup relay valve 133 is released, and the lockup control valve is released. 132 is in communication, and the lockup relay valve 133 is switched to the off position. By this operation, the oil pressure of the import 133a is supplied from the port 133c to the lock-up off oil passage of the torque converter 12, and conversely, the return oil returning from the lock-up on oil passage to the port 133b is returned from the valve. It is drained through the check valve or cooled via the cooler and returned to the oil pan. In this way, lock-up on / off and slip control are performed according to the duty ratio of the current output by the control unit 3.

As shown in FIG. 1, the control unit 3 for controlling the automatic transmission is a central processing unit (CP).
U), random access memory (RAM), read only memory (ROM) control computer (EC
U), based on the information from each sensor for detecting the vehicle speed and the vehicle load (in this example, the throttle opening θ), each on / off solenoid valve and linear solenoid of the hydraulic control circuit 13 according to the incorporated program. Issue a control signal to the valve. In this example, the control unit 3 is also provided with a mode selection means 35 for manually setting the low μ road traveling, and the snow mode can be set by the driver.

The target differential rotation setting process of the lockup control device thus configured will be described with reference to the flow chart shown in FIG. First, in step 1, if it is determined whether or not the snow mode is manually set, in the case of YES, the flag setting f = 1 indicating low μ road traveling is set in step 2, and in the case of NO, the flag setting f is cleared by step 3. = 0.
Then, in the next step S4, the flag setting judgment is made based on whether the outside air temperature T is higher or lower than the reference value T ₁ as one judgment factor for the low μ road. If yes, the flag setting f = 1 is set in the next step S5, and if no, step S5 is skipped. In the next step S6, it is determined whether or not it is in the lockup slip control region. If this determination is yes, the next step S
The flag previously set in 7 is confirmed, and if the result is YES, the differential rotation ΔN is set to the predetermined value N in the next step S8.
_The process of setting to ₁ is performed. On the other hand, if the determination in step S6 is no, the subsequent steps are skipped and the process returns. On the other hand, if the determination in step S7 is NO, processing for setting the differential rotation ΔN to a value N ₂ smaller than the predetermined value is performed in step S9.

The lockup ON / OFF and the slip control of the lockup controller are not particularly different from the conventional ones, and the number of revolutions detected by the engine revolution sensor SN2 is referred to while referring to the area on the map data. N _E
(Or output speed No. detected by output speed sensor SN4
It may be the vehicle speed calculated from ut, the input speed Nin detected by the input speed sensor SN3, the output speed calculated from the gear ratio, etc.) and the throttle opening θ detected by the throttle sensor SN1. . Then, the determination of the lockup slip control request relating to the target differential rotation setting process is made in the slip control region.

FIG. 7 shows the effect of the above embodiment,
In the medium / high μ road shown in (1), in the lock-up slip control state when the engine is driven, a predetermined small differential rotation amount with respect to the engine speed N _E shown by a solid line in the figure is shown by a chain line in the figure. While the turbine speed Nin is maintained and the wheel speed N _H indicated by the chain double-dashed line in the figure is also maintained, when the throttle-off operation is performed, the engine speed N _E rapidly decreases and the reverse When the predetermined rotational speed difference N ₂ for driving is reached, the wheel rotational speed N _H is gradually lowered while maintaining the differential rotational speed N ₂ . When the brake is turned on here, the lockup slip control is released, so the engine speed N _E decreases in accordance with its own inertial force. In this case, since wheel lock does not occur, the engine is already locked up when the wheels are stopped, so the engine speed N _E maintains stable rotation when it has dropped to the idling speed.

Next, on the low μ road shown in (2), when the brake is turned on in the same manner as above from the state where the differential rotation amount N ₂ similar to the above is maintained, the lockup slip control is released similarly. However, since the wheel rotation speed N _H becomes 0 in an extremely short time due to the wheel lock, the engine rotation speed N _E also becomes 0 at the same time due to the lock-up drag until the actual lock-up off operation occurs. To engine stall.

On the other hand, when the differential rotation amount is set according to the present invention, as shown in (3), since a high differential rotation amount N ₁ is produced from the beginning, the brake is turned on in the same state as above. If the lock-up slip control is performed, the lock-up slip control is similarly released, but the wheel rotation speed N _H becomes 0 in an extremely short time by the wheel lock, whereas the lock-up until the actual lock-up off operation occurs. The lock-up operation is completed before the wheels are locked, and the engine speed N _E is maintained when the engine reaches the idling speed without being dragged by the wheel lock.

In the above example, the case where the brake is turned on after the throttle is turned off is shown as the case where the engine stall is most likely to occur. However, when the brake is turned on from the throttle on state, the engine is turned on the contrary. Brake-on operation in driving state, engine speed N
_{Since E} is higher than the wheel rotation speed N _H by the differential rotation amount N ₁ , the engine rotation speed N is higher than that shown in (3) above.
_E is less likely to be dragged by the wheel lock.

In summary, in the above embodiment, when the vehicle reaches the low μ road running under the lock-up slip control, the low μ road judging means 32 judges the possibility, and the target differential rotation setting means 33 makes it possible. The target value of the differential rotation amount of the lockup clutch 11 is set to a large value N ₁ corresponding to traveling on a low μ road as compared with the normal lockup slip control, and the differential rotation control means 34 sets the input side and the output side of the torque converter 12. The operation of controlling the lockup control valve 132 is performed so that the value becomes the set differential rotation amount. Therefore, according to this configuration, since the setting of the large differential rotation amount N ₁ corresponding to the sudden braking can be limited only to the low μ road traveling under the lockup slip control, the fuel efficiency improving effect obtained by the lockup slip control can be obtained. It is possible to more reliably prevent engine stall during rapid deceleration on any road surface without damaging the engine as much as possible.

As described above, the present invention is applied to a specific automatic transmission and the control for changing the target differential rotation speed is performed in the lock-up slip region, but the present invention is not limited to this. The present invention is applicable to various automatic transmissions, and it is also possible to perform control for setting a target differential rotation speed of lockup slip in the lockup region. It goes without saying that various changes can be made with.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of an automatic transmission to which a lock-up control device of the present invention is applied, in which a mechanical unit is skeletonized and a control unit is block-shaped.

FIG. 2 is an operation chart of the automatic transmission according to the above embodiment.

FIG. 3 is a hydraulic circuit diagram showing one of the lockup control circuits of the above embodiment divided into two parts.

FIG. 4 is a hydraulic circuit diagram showing the other half of the lockup control circuit.

FIG. 5 is a block diagram showing in detail a control unit for setting a target rotation speed in the above embodiment.

FIG. 6 is a flowchart showing a process of setting a target rotation speed in a control unit of the control device of the embodiment.

FIG. 7 is a time chart showing the effect of the control device of the embodiment by the change of each rotation speed.

[Explanation of symbols]

 E Engine C Crankshaft (output shaft) 1 Automatic transmission 11 Lockup clutch 12 Torque converter 13 Hydraulic control circuit 13a Lockup control circuit 101 Input shaft 123 On-side oil chamber 124 Off-side oil chamber 132 Lockup control valve

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Masayasu Ito 10 Takane, Fujii-cho, Anjo City, Aichi Prefecture Aisin AW Co., Ltd. (72) Inventor Mitsutaka Ito 10 Takane, Fujii-cho, Anjo City, Aichi Prefecture Aisin・ AW Co., Ltd. (72) Inventor Toshiki Kaneda 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (2)

[Claims] 1. An output shaft of an engine and an input shaft of a transmission, the input side being connected to an output shaft of an engine, the output side being connected to an input shaft of a transmission, and being arranged between the engine and the transmission. In an automatic transmission having a lock-up clutch that is directly connected to the lock-up clutch, a lock-up control request judgment means for judging whether or not lock-up control is to be performed depending on the vehicle running condition, and Based on the road determination means, the lockup control determination by the lockup control request determination means, and the low μ road determination by the low μ road determination means, the target value of the differential rotation amount between the input side and the output side of the lockup clutch. And a differential rotation control means for controlling the lock-up clutch so that the set differential rotation amount is set, and a lock-up control device for an automatic transmission. . 2. A torque converter having an input side connected to an output shaft of an engine and an output side connected to an input shaft of a transmission, the torque converter being arranged between the engine and the transmission, and the input side of the torque converter. A lock-up clutch that directly connects the lock-up clutch and an output side; an on-side oil chamber to which an on-pressure for engaging the lock-up clutch is supplied; and an off-side oil chamber to which an off-pressure for releasing the lock-up clutch is supplied. An automatic transmission having a lock-up control valve that slip-controls the lock-up clutch by controlling a differential pressure between an on-pressure supplied to the on-side oil chamber and an off-pressure supplied to the off-side oil chamber. In the lock-up control device, a lock-up slip control request determination means for determining whether or not to perform lock-up slip control depending on the vehicle running state, and a road surface on a low μ road Of the lockup clutch based on the low μ road determination means for determining whether or not there is a possibility of the lockup slip control determination by the lockup slip control request determination means, and the low μ road determination by the low μ road determination means. Target differential rotation setting means for setting a large target value of the differential rotation amount, and differential rotation control means for controlling the lock-up control valve so that the input side and the output side of the torque converter have the set differential rotation amount. A lockup control device for an automatic transmission, comprising: