KR20150036348A - Automatic transmission for vehicle - Google Patents

Abstract

A torque converter 2 disposed between the engine 1 and the drive wheel 7, a speed change mechanism 30 disposed in series with the torque converter 2, a mechanical oil pump (12) for stopping the engine (1) when a coast stop condition is satisfied, including a condition that the vehicle speed is equal to or less than the coast stop allowable vehicle speed VSP2; And an electric oil pump 10e driven by the hydraulic oil pump 10e while the engine 1 is stopped and the frictional engagement element of the auxiliary transmission mechanism 30 is engaged with the oil pressure from the electric oil pump 10e The controller 12 is configured to determine whether or not the engine 1 can be stopped based on the vehicle speed and the turbine rotational speed Nt of the torque converter 2. In this case,

Description

[0001] AUTOMATIC TRANSMISSION FOR VEHICLE [0002]

The present invention relates to an automatic transmission for a vehicle having a coast stop function.

There is known a vehicle having a function of automatically stopping an engine (driving source) (so-called idling stop function) for the purpose of improving fuel economy and the like.

In recent years, there has been proposed a vehicle having a function of stopping the engine at a low-speed coasting (so-called coast stop function) in which the vehicle is likely to stop even when the vehicle is running, For example, Patent Document 1 describes a technique for starting a coast stop when the vehicle speed is equal to or less than a permissible vehicle speed (coast stop permitted vehicle speed) of a coast stop.

In the automatic transmission of a vehicle equipped with a coast stop function, it is required to maintain the engagement state of the friction engagement element in the case where there is a request for re-acceleration during coast stop.

In the automatic transmission disclosed in Patent Document 1, the rotational driving force of the engine is transmitted to the drive wheel through the transmission mechanism (frictional engagement element). While the engine is stopped by the coast stop, the mechanical oil pump The oil pressure is supplied to the frictional engagement element by a battery-driven electric oil pump to maintain the engaged state of the frictional engagement element.

In the automatic transmission of Patent Document 1, while determining the deceleration state of the vehicle by signals such as the brakes and the accelerator opening degree, the coast stop function is operated only in the extremely low-speed region in which no shifting is performed based on the vehicle speed. Since the extremely low-speed region is not a speed-change permitting region, the turbine rotation speed Nt is uniquely determined in the coasting state in this extremely low-speed region, and the fastening capacity required for bringing the friction- As shown in FIG.

On the other hand, it is desired to set the coast-stop permitted vehicle speed to a higher-speed region side in accordance with the recent increase in the demand for fuel economy improvement. However, if the coast-stop permitted vehicle speed is expanded to the higher-speed region side, the coast-stop permitted region and the shiftable region overlap. Even if the vehicle speed and the turbine rotation speed do not correspond one-by-one in the shiftable range and the coast stop function is operated based on the vehicle speed after determining the deceleration state by the signal described above, , It is possible to take a plurality of turbine rotation speeds (Nt).

If the coast stop is operated in a state where the turbine rotation speed Nt is high, the required tightening capacity of the frictional engagement element is increased, so that there is a problem that the engaged state of the frictional engagement element can not be maintained in the electric oil pump.

As a result, if the acceleration request is made at this time, there is a problem that the ash attribution is lowered due to the time lag before the frictional engagement element transmits the power to the recalculation request during the coast stop. there was.

Here, as an example of the case of a continuously variable transmission in which a frictional engagement element and a CVT are arranged in series with respect to an operating state of "deciding a deceleration state in the signal and taking a plurality of turbine rotation speeds Nt by the speed ratio even if the vehicle speed is the same" Scenes 1 and 2 will be described.

Fig. 11 is a view for explaining the speed difference region side of the shift map defined by the vehicle speed VSP and the rotation speed Npri (= turbine rotation speed Nt) of the primary pulley of the belt-type continuously variable transmission.

<Scene 1>

For example, when the L range is selected by the shift lever so that the speed ratio is fixed to the lowermost line (lowest line), or when the transmission operates in the so-called manual mode and the speed change stage is fixed to the first speed, When the accelerating vehicle is changed to deceleration, the engagement state of the frictional engagement element may not be maintained.

When the accelerator pedal is stepped to accelerate and accelerate the vehicle and the vehicle speed becomes higher than the coasting start vehicle speed VSP2 and then the accelerator pedal is released to decelerate the vehicle, the operating point of the continuously variable transmission is shifted from zero Point D, and point D 'toward the higher-velocity region side (right side in the drawing). When the accelerator pedal is released at the point when the operating point reaches the point E, the operating point changes from the point E to the low-speed region side (left side in the figure) via the point F, To zero (0).

In the case of the automatic transmission of Patent Document 1, when the area for executing the coast stop is simply widened from the conventional permitted vehicle speed VSP1 to the vehicle speed VSP2 at the higher speed range side, the accelerator pedal is released and the vehicle speed starts to drop In the point F immediately after this, since the requirement of the vehicle speed &lt; the permitted vehicle speed VSP2 is satisfied, the coast stop is started at the time point F thereof.

Here, when the turbine rotation speed when the frictional engagement element can be maintained in the engaged state by the hydraulic pressure that can be supplied from the electric oil pump is the turbine rotation speed (turbine rotation speed Nt2 at the upper limit) indicated by Nt2 in the figure, Since the turbine rotation speed Nt3 at the time of starting is larger than the turbine rotation speed Nt2 at the upper limit, the frictional engagement element can not be maintained in the engaged state.

<Scene 2>

Another case in which the fastening state of the frictional engagement element can not be maintained will be described.

For example, in a state in which the D range is selected, the accelerator pedal is stepped to start and accelerate the vehicle, and when the vehicle speed reaches between the start vehicle speed VSP1 of the conventional coast stop and the vehicle speed VSP2 higher than the start vehicle speed VSP1 Next, when the vehicle is decelerated by releasing the accelerator pedal, the operating point of the continuously variable transmission is changed from zero (0) to point D and point D 'toward the high-speed region side do. When the accelerator pedal is released when the operating point reaches the point G, the upshift is started at that point and the operating point is changed toward the low rotational speed side (lower side in the figure) along the chain line in the figure. Then, then, the operating point reaches the point C on the cost line from the point G via the point H, then reaches the point D on the lowest line along the cost line, and finally, along the lowest line, (0).

In the case of the automatic transmission of Patent Document 1, when the area for executing the coast stop is simply widened from the conventional permitted vehicle speed VSP1 to the vehicle speed VSP2 at the higher speed range side, at the time point when the accelerator pedal is released, &Lt; &lt; / RTI &gt; Since the requirement of the permissible vehicle speed VSP2 is satisfied, the coast stop is started at the point G of time.

However, immediately after the accelerator pedal is released, the speed ratio of the continuously variable transmission does not change immediately but is at or near the point G. However, since the turbine rotation speed Nt4 at the point G or its vicinity is larger than the turbine rotation speed Nt2 at the upper limit, the frictional engagement element can not be maintained in the engaged state also in this case.

If the coast stop is executed with the turbine rotation speed Nt being high, even if the electric oil pump is driven instead of the mechanical oil pump which is stopped following the stop of the engine, the capacity of the electric oil pump is smaller than that of the mechanical oil pump A sufficient flow rate (hydraulic pressure) can not be secured and the fastening state of the friction engagement element can not be maintained. Therefore, when the fastening state of the frictional engagement element can not be maintained, there is a problem that if the fastening speed is required, the frictional engagement element must be in the fastened state, and the ash property is lowered by that amount.

An object of the present invention is to enlarge a cost stop area without reducing the ash attribution when there is a re-acceleration request during coast stop execution.

Japanese Patent Application Laid-Open No. 2010-164143

According to the present invention,

A fluid transmission mechanism disposed between the drive source and the drive wheel,

A friction engagement element arranged in series with the fluid transmission mechanism,

A hydraulic pressure source driven by the drive source,

Drive source control means for stopping the drive source when a predetermined stop condition is established at the time of deceleration of the vehicle,

And another hydraulic pressure source driven by another driving source different from the driving source while the driving source is stopped,

And the frictional engagement element is held in the engaged state by the hydraulic pressure from the other drive source while the drive source is stopped,

And the drive source control means determines the stop of the drive source based on the output rotation speed of the fluid transmission mechanism.

According to the present invention, the stop of the drive source is determined in consideration of the output shaft rotation speed of the fluid transmission mechanism contributing to the engagement of the friction engagement element.

When the vehicle speed at which the drive source is stopped is widened toward the higher speed region side, even if the vehicle speed is the same, different output shaft rotational speeds can be obtained depending on the speed ratio. Therefore, The frictional engagement element may not be held in the engaged state by the hydraulic pressure from the other drive source.

Considering the output shaft rotation speed of the fluid transmission mechanism contributing to the engagement of the frictional engagement element in determining the stop of the drive source as described above, even if the vehicle speed permitting the stop of the drive source is widened toward the high- The stop of the driving source can be permitted when the frictional engagement element can be held in the engaged state by the hydraulic pressure.

1 is a schematic configuration diagram of a vehicle equipped with a continuously variable transmission according to the embodiment.
Fig. 2 is a view for explaining the configuration of the controller of the continuously-variable transmission according to the embodiment. Fig.
3 is an explanatory view showing an example of a shift map of the continuously variable transmission according to the embodiment.
4 is an explanatory diagram of a hydraulic control circuit of a continuously variable transmission according to the embodiment.
5 is a flowchart of an execution determination of a coast stop according to the embodiment.
6 is a shift map of the transmission according to the embodiment.
7 is a timing chart for explaining the operation of the transmission.
8 is a diagram schematically showing a power transmission path from the engine to the wheels.
9 is a view for explaining the difference between the input torque on the upstream side and the input torque on the downstream side in the frictional engagement element.
10 is a timing chart for explaining the operation of the transmission.
11 is a view for explaining a shift map.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the "gear ratio" of any transmission mechanism is a value obtained by dividing the input rotational speed of the transmission mechanism by the output rotational speed of the transmission mechanism. The "lowest (lowest) speed ratio" is the maximum speed ratio of the transmission mechanism, and the "highest (highest) speed ratio" is the minimum speed ratio of the transmission.

1 is a schematic configuration diagram of a coast-stop vehicle according to an embodiment of the present invention. This vehicle is provided with an engine 1 as a drive source and the output rotation of the engine 1 is transmitted to the torque converter 2, the first gear train 3, the continuously variable transmission (hereinafter simply referred to as &quot; The second gear train 5 and the differential device 6 to the drive wheels 7 via the transmission 4, The second gear train (5) is provided with a parking mechanism (8) for locking the output shaft of the transmission (4) so that it can not mechanically rotate at the time of parking.

The transmission 4 is provided with a mechanical oil pump 10m that receives rotation of the engine 1 and is driven by using a part of the power of the engine 1 and a mechanical oil pump 10m that is driven by receiving power from the battery 13, (10e). The electric oil pump 10e is constituted by an oil pump main body, an electric motor and a motor driver for rotationally driving the oil pump main body, and the operation load can be controlled to an arbitrary load or in a multistage manner. The transmission 4 is also provided with a hydraulic pressure control valve (not shown) for controlling the hydraulic pressure from the mechanical oil pump 10m or the electric oil pump 10e A control circuit 11 is provided.

The transmission 4 is provided with a belt type continuously variable transmission mechanism (hereinafter referred to as a "variator 20") and a speed change mechanism 30 provided in series with the variator 20. Means that the variator 20 and the auxiliary transmission mechanism 30 are installed in series in the power transmission path from the engine 1 to the drive wheels 7. The auxiliary speed-change mechanism 30 may be directly connected to the output shaft of the variator 20 as in this example, or may be connected through another speed change or power transmission mechanism (for example, gear train). Alternatively, the auxiliary transmission mechanism 30 may be connected to the front end (input shaft side) of the variator 20.

The variator 20 includes a primary pulley 21, a secondary pulley 22, and a V-belt 23 wound therebetween. The primary pulley 21 and the secondary pulley 22 each have a fixed conical plate and a movable conical plate which is disposed in a state in which the sheave surface faces the fixed conical plate and forms a V- And hydraulic cylinders (23a, 23b) provided on the back surface of the movable conical plate for displacing the movable conical plate in the axial direction. The width of the V groove changes and the contact radius between the V belt 23 and each of the pulleys 21 and 22 changes so that the speed ratio of the variator 20 becomes It changes steplessly.

The auxiliary transmission mechanism 30 is a forward two-speed / reverse one-speed transmission mechanism. The auxiliary transmission mechanism 30 is connected to a Ravigneaux planetary gear mechanism 31 connecting two planetary gear carriers and a plurality of rotary elements constituting the Ravigneaux planetary gear mechanism 31, (The low brake 32, the high clutch 33, and the Rev brake 34) for changing the state of the frictional engagement element. When the supply oil pressure to each of the friction engagement elements 32 to 34 is adjusted and the state of engagement / disengagement of the friction engagement elements 32 to 34 is changed, the speed change stage of the auxiliary transmission mechanism 30 is changed.

For example, when the low-stage brake 32 is engaged and the high-speed clutch 33 and the Rev brake 34 are disengaged, the speed change stage of the auxiliary speed-change mechanism 30 becomes 1 gear. When the high-speed clutch 33 is engaged and the low-stage brake 32 and the Rev brake 34 are disengaged, the speed change stage of the auxiliary speed-change mechanism 30 becomes two speeds having a speed ratio lower than that of the first speed. When the Rev brake 34 is engaged and the low-stage brake 32 and the high-speed clutch 33 are disengaged, the speed change stage of the auxiliary speed-change mechanism 30 is reversed. In the following description, when the speed change stage of the auxiliary speed change mechanism 30 is the first speed, "the transmission 4 is in the low speed mode" and when it is the second speed, "the transmission 4 is in the high speed mode" .

Each frictional engagement element is provided on the power transmission path and at the front end or the rear end of the variator 20 so as to enable power transmission of the transmission 4 when any one of the frictional engagement elements is engaged, Lt; / RTI &gt;

2, the controller 12 is a controller that integrally controls the engine 1 and the transmission 4. The controller 12 includes a CPU 121, a storage device 122 composed of RAM and ROM, An interface 123, an output interface 124, and a bus 125 connecting them to each other.

The input interface 123 is provided with an output signal of the accelerator opening degree sensor 41 for detecting the accelerator opening APO which is the manipulated variable of the accelerator pedal, an input signal of the accelerator opening degree sensor 41, An output signal of the vehicle speed sensor 43 for detecting the vehicle speed VSP, and a line pressure sensor 44 for detecting the line pressure PL (hereinafter, referred to as &quot; primary rotational speed Npri &quot; An output signal of an inhibitor switch 45 for detecting the position of a select lever, an output signal of a brake hydraulic pressure sensor 46 for detecting a brake hydraulic pressure, a turbine (not shown) for detecting an output shaft rotational speed of the torque converter 2, The output signal of the rotation speed sensor 47, and the like.

The storage device 122 stores the control program of the engine 1, the shift control program of the transmission 4, and various maps and tables used in these programs. The CPU 121 reads and executes a program stored in the storage device 122 and performs various kinds of arithmetic processing on various signals inputted through the input interface 123 to output a fuel injection amount signal, A shift control signal and a drive signal of the electric oil pump 10e and outputs the generated signal to the engine 1 via the output interface 124, the hydraulic control circuit 11, the electric oil pump 10e. Various values used by the CPU 121 in the arithmetic processing and the arithmetic result thereof are appropriately stored in the storage device 122. [

The hydraulic control circuit 11 is composed of a plurality of hydraulic fluid control valves. The hydraulic pressure control circuit 11 controls the hydraulic pressure control valves based on the shift control signal from the controller 12 so as to switch the supply path of the hydraulic pressure and to switch the hydraulic pressure supply path between the mechanical oil pump 10m or the electric oil pump 10e And supplies the required hydraulic pressure to the respective portions of the transmission 4. The hydraulic pressure in the transmission 4 is supplied to the transmission 4, Thus, the speed ratio of the variator 20 and the speed change stage of the auxiliary speed change mechanism 30 are changed, and the shifting of the transmission 4 is performed.

Fig. 3 shows an example of a shift map stored in the storage device 122. Fig. The controller 12 controls the variator 20 and the auxiliary transmission mechanism 30 (the vehicle speed VSP, the primary rotation speed Npri, the accelerator opening APO in this embodiment) based on the shift map, ).

In this shift map, the operating point of the transmission 4 is defined by the vehicle speed VSP and the primary rotation speed Npri. The inclination of the line connecting the operating point of the transmission 4 and the zero point of the lower left corner of the shift map is the total speed ratio obtained by multiplying the speed ratio of the variator 20 of the transmission 4 by the speed ratio of the auxiliary speed- , Hereinafter referred to as &quot; through speed ratio &quot;). In this shift map, a shift line is set for each accelerator opening degree APO in the same manner as the shift map of the conventional belt-type continuously variable transmission, and the shifting of the transmission 4 is performed in accordance with the shift line selected corresponding to the accelerator opening APO All. 3, a total load line (a shift line when the accelerator opening APO = 8/8), a parasitic line (a shift line when the accelerator opening APO = 4/8), a coast line Only the shift line when the accelerator opening degree APO = 0/8) is shown.

When the transmission 4 is in the low speed mode, the transmission 4 selects the lowest speed mode lowest line obtained by setting the speed ratio of the variator 20 to the lowest speed ratio and the speed ratio of the variator 20 to the highest speed ratio Respectively. In this case, the operating point of the transmission 4 moves within the area A and the area B, respectively. When the transmission 4 is in the high speed mode, the transmission 4 is controlled by the high speed mode lowest line obtained by setting the speed ratio of the variator 20 to the lowest speed ratio and the speed ratio of the variator 20 to the high speed mode You can shift between tops. In this case, the operating point of the transmission 4 moves within the B region and the C region.

The speed ratio of each of the speed change stages of the auxiliary speed change mechanism 30 is set so that the speed ratio (low speed mode maximum speed ratio) corresponding to the high speed mode highest is smaller than the speed ratio (fast mode minimum speed ratio) corresponding to the high speed mode bottom. As a result, the range of the through-going transmission ratio (the "low-speed mode retry range" in the drawing) of the transmission 4 that can be taken in the low-speed mode and the range of the through- Speed mode retirement range &quot;) is partially overlapped and the operating point of the transmission 4 is in the region B which is sandwiched by the high-speed mode bottom line and the low-speed mode top line, the transmission 4 is in the low- Any mode can be selected.

On the shift map, a mode change-speed line for shifting the speed change mechanism 30 is set so as to overlap the high-speed mode top line. The through speed ratio (hereinafter, referred to as &quot; mode switching speed ratio mRatio &quot;) corresponding to the mode switching speed line is set to a value equivalent to the maximum speed ratio of the low speed mode. Setting the mode change-speed line in this way is advantageous in that the lower the speed ratio of the variator 20 is, the smaller the input torque to the speed change mechanism 30 is, and thus the shifting shock when shifting the speed change mechanism 30 is suppressed It is because.

When the operating point of the transmission 4 crosses the mode change speed line, that is, when the actual value of the through speed ratio (hereinafter referred to as &quot; actual through speed ratio Ratio &quot;) changes over the mode change speed ratio mRatio, 12 performs the coordinated shift described below, and switches between the high speed mode and the low speed mode.

The controller 12 changes the speed ratio of the variator 20 to a direction opposite to the direction in which the speed ratio of the auxiliary speed change mechanism 30 is changed. At this time, the inertia phase in which the speed ratio of the auxiliary speed change mechanism 30 is actually changed is synchronized with the period in which the speed ratio of the variator 20 is changed. Changing the speed ratio of the variator 20 in the direction opposite to the speed ratio change of the auxiliary speed change mechanism 30 is intended to prevent the driver from feeling uncomfortable due to a change in input rotation due to a step difference in the actual through speed ratio Ratio .

More specifically, when the actual through speed ratio Ratio of the transmission 4 is changed from the low side to the high side in the mode change speed ratio mRatio, the controller 12 determines whether or not the speed change stage of the speed change mechanism 30 (1-2 shift) from the first speed to the second speed and changes the speed ratio of the variator 20 to the lower speed side.

Conversely, when the actual through speed ratio Ratio of the transmission 4 is changed from the high-stage side to the low-stage side, the controller 12 changes the speed change stage of the negative speed change mechanism 30 from the second speed to the first speed (2-1 shift), and the speed ratio of the variator 20 is changed to the high speed side.

In the transmission 4 according to the present embodiment, when the speed change stage of the negative speed change mechanism 30 is maintained at the second speed, the actual through speed ratio Ratio of the transmission 4 changes from the high side to the mode change speed ratio mRatio So that the shift from the second speed to the first speed is not performed even when the speed change is made across the lower speed side.

Further, the controller 12 performs cost stop control to be described below in order to suppress the fuel consumption amount.

The coast stop control is a control for automatically stopping (stopping the engine 1) while the vehicle is running in the low-speed region to suppress the fuel consumption amount. The fuel cut control executed when the accelerator is off means that the fuel supply to the engine 1 is stopped. However, the lock-up clutch is released to cut off the power transmission path between the engine 1 and the transmission 4 , And the rotation of the engine 1 is completely stopped.

In this case, in the transmission 4 according to the embodiment, the friction engagement element (high-speed clutch 33) is held in the engaged state during the coast stop until the vehicle stops.

In executing the coast stop, the controller 12 first determines the following conditions a to d, for example.

a: The foot is released from the accelerator pedal (accelerator opening APO = 0)

b: Brake pedal is stepped (brake fluid pressure is higher than the specified value)

c: When the vehicle speed is lower than a predetermined lower speed (for example, 16 km / h)

d: the turbine rotation speed is lower than the predetermined rotation speed

Here, the conditions a to c are conditions for judging whether or not the driver intends to stop the vehicle.

The controller 12 determines that the cost stop condition is established when all the conditions a to c are satisfied and determines the start of the coast stop when the condition d is satisfied in addition to the conditions a to c.

In the coast stop, the fuel supply to the engine 1 is stopped, and the engine 1 is automatically stopped. When the engine 1 is stopped, the mechanical oil pump 10m driven by the power of the engine 1 is also stopped, the discharge pressure is reduced, and finally becomes zero.

When the drive of the electric oil pump 10e is started at the time when the cost stop condition is established and the oil pressure generated by the electric oil pump 10e is larger than the oil pressure generated by the mechanical oil pump 10m, The hydraulic pressure generated in the hydraulic cylinder 10e is supplied to the hydraulic cylinders 23a and 23b and the auxiliary transmission mechanism 30. [ The hydraulic pressure supplied to the hydraulic cylinders 23a and 23b changes the variator 20 to the speed ratio corresponding to the vehicle speed at that point of time until the vehicle decelerates and stops.

When the start of the coast stop is determined, the controller 12 maintains the engaged state of the high speed clutch 33 until the vehicle is stopped thereafter. When the vehicle is stopped, the controller 12 releases the high-speed clutch 33, and then engages the low-stage brake 32 in preparation for oscillation of the vehicle.

In addition, the conditions a to c above are continued to determine whether or not the conditions are satisfied even during coast stop. When any one of them is not formed, the cost stop condition is not fulfilled. The controller 12 resumes the supply of fuel to the engine 1 to restart the engine 1, and the mechanical oil pump 10m The electric oil pump 10e is stopped at the time point when the oil pressure is generated.

4 is an explanatory view showing the configuration of the hydraulic control circuit 11 of the present embodiment.

The hydraulic control circuit 11 is provided with a mechanical oil pump 10m driven by the driving force of the engine 1. [ The hydraulic pressure generated by the mechanical oil pump 10m is regulated to a predetermined line pressure by the pressure regulator valve 51 and is distributed to the respective portions of the variator 20 and the auxiliary transmission mechanism 30 through the oil passage 50 do.

The hydraulic pressure generated by the mechanical oil pump 10m is supplied to the torque converter 2 through the pressure regulator valve 51. [ This oil pressure is used for torque transmission of the torque converter 2 and engagement / disengagement of the lock-up clutch.

The line pressure of the oil line 50 is supplied to the oil chamber of the hydraulic cylinder 23b of the secondary pulley 22. The line pressure of the oil passage 50 is reduced by the pressure reducing valve 52 and supplied to the oil chamber of the hydraulic cylinder 23a of the primary pulley 21. [ By adjusting the hydraulic pressure supplied to the oil chamber of the hydraulic cylinder 23a by the pressure reducing valve 52, the width of each V groove is changed by the differential pressure with the line pressure supplied to the oil chamber of the hydraulic cylinder 23b, The contact radius between the pulley 23 and the pulley is changed, and the speed ratio of the variator 20 changes steplessly.

The line pressure of the oil passage 50 is supplied to the high speed clutch 33 through the pressure reducing valve 54 and the low stage brake 32 via the pressure reducing valve 53, do. The pressure reducing valve (53) adjusts the hydraulic pressure supplied to the lower stage brake (32) to control the engagement force of the lower stage brake (32). The pressure reducing valve (54) controls the tightening force of the high speed clutch (33) by adjusting the hydraulic pressure supplied to the high speed clutch (33).

An accumulator 60 is connected to a flow path 56 between the pressure reducing valve 53 and the lower stage brake 32. [ The accumulator (60) reserves the hydraulic oil inside, and alleviates the hydraulic pressure change of the hydraulic oil passage (56) by the hydraulic oil.

Specifically, when the hydraulic pressure is equal to or higher than the predetermined pressure, the hydraulic oil is stored in the accumulator 60. The hydraulic oil stored in the accumulator 60 is supplied to the oil passage 56 to delay the hydraulic pressure drop response of the oil passage 56 when the oil pressure is lower than the predetermined pressure. Further, when the oil pressure of the oil passage 56 rises from a low state, the operating oil is stored in the accumulator 60, thereby delaying the oil pressure rise response of the oil passage 56. [ This suppresses the hydraulic pressure responsiveness of the oil passage 56 and suppresses the sudden rise and fall of the oil pressure, thereby suppressing the shock at the time of engagement and release of the low-stage brake 32. [

The controller 12 controls the pressure regulator valve 51 to adjust the line pressure. Further, the pressure reducing valve 52 is controlled to adjust the hydraulic pressure to the hydraulic cylinder 23a of the primary pulley 21, thereby controlling the speed ratio of the variator 20. [ Further, the pressure reducing valve (53) is controlled to control the engagement state of the low-stage brake (32). Further, the pressure reducing valve 54 is controlled to control the engagement state of the high speed clutch 33.

The mechanical oil pump 10m is driven by the rotation of the engine 1. The mechanical oil pump 10m is always rotated while the engine 1 is rotating to generate the hydraulic pressure required for the operation of the transmission 4. [ Since the transmission 4 requires a hydraulic pressure in preparation for oscillation of the vehicle even when the vehicle is at rest, a state in which the engine 1 is rotating at the time of stopping the vehicle is generated by the drive of the mechanical oil pump 10m .

On the other hand, when the rotation of the engine 1 is stopped by a coast stop or the like, the drive of the mechanical oil pump 10m is stopped, and the oil pressure drops. In contrast to this, the oil passage 50 is provided with the electric oil pump 10e.

The electric oil pump 10e is controlled by the controller 12 to supply the oil pressure to the transmission 4 when the rotation of the engine 1 is stopped and the mechanical oil pump 10m is not operating, (13) to generate a hydraulic pressure.

Further, the electric oil pump 10e operates at a relatively low load such as an idle stop or a coast stop. Therefore, it is desirable that the capacity should be such that the required oil pressure can be satisfied in such operating conditions, and that the increase in the weight of the vehicle and the increase in cost are not caused.

5 is a flowchart of the execution determination of the coast stop by the controller 12 of the present embodiment. The processing of this flowchart is executed by the controller 12 at a predetermined interval (for example, 10 ms).

The processing of the execution decision of coast stop by the controller 12 will be described.

A signal is input from the various sensors shown in Fig. 2 to the controller 12. When a signal is input from various sensors (step 101), based on the current operating state specified from the input signal, Is established (step 102).

Here, the cost stop condition is a condition for determining whether the driver intends to stop the vehicle, and is a to c shown below.

a: The foot is released from the accelerator pedal (accelerator opening APO = 0)

b: Brake pedal is stepped (brake fluid pressure is higher than the specified value)

c: Vehicle speed is allowed to coast stop Vehicle speed VSP2 or less

d: the turbine rotation speed is not more than the predetermined rotation speed Nt2

Therefore, when it is determined in step 102 that the coast-stop condition is not satisfied, the process proceeds to step 104, where coast stop is prohibited (stopping of the engine 1 is prohibited) Coast stop is not executed.

On the other hand, when it is determined that the coast-stop condition is satisfied (step 102, Yes), the process proceeds to step 103 and the coast stop is permitted (the engine 1 is stopped) And the coast stop is executed.

The predetermined rotation speed Nt2 is set to an upper limit value of the turbine rotation speed Nt when the engagement state of the high speed clutch 33 can be maintained by the hydraulic pressure that can be generated by the electric oil pump 10e, Rotation speed Nt2 are different from each other depending on the oil pressure that can be generated in the electric oil pump 10e provided in the transmission 4. [

Hereinafter, the operation of the transmission 4 according to the embodiment will be described by applying to the traveling state of the vehicle.

Fig. 6 is a view for explaining the shift map of the transmission 4 according to the embodiment, and the lower-speed region side on which the coast-stop is executed.

Fig. 7 is a timing chart for explaining the operation of the transmission 4. Fig. 7 (a) shows the case where the coast-stop permissible vehicle speed VSP2 and the turbine speed Nt are taken into consideration in the determination of the start of the coast- b) show the case of the conventional example in which only the coast-stop permissible vehicle speed VSP1 is considered.

In the drawings, &quot; CS area &quot; means &quot; area where cost stop is executed &quot;. The coast-stop permissible vehicle speed VSP1 in the case of the conventional example is set in a low-speed region (a vehicle speed region where the vehicle speed and the turbine rotation speed correspond one-to-one) in which the turbine rotation speed Nt is uniquely determined with respect to the vehicle speed, The allowable vehicle speed VSP2 is a vehicle speed region in which the turbine rotational speed Nt is uniquely determined with respect to the vehicle speed (a vehicle speed range in which the turbine rotational speed Nt can be obtained for one vehicle speed region) : A vehicle speed range where a shift can be performed).

[Operational example 1]

When the vehicle is running with the vehicle speed higher than the coast-stop permissible vehicle speed VSP2 of the transmission 4 according to the embodiment, the vehicle speed is lowered due to the accelerator: off or brake: Will be described from the highest line to the lowermost line through the cost line.

In the transmission 4 according to the embodiment, it is assumed that the vehicle speed (coast-stop permissible vehicle speed VSP2) under the coast-stop condition is set to the higher-speed range side than the coast-stop permissible vehicle speed VSP1 in the conventional case.

6 and 7A, when the accelerator is turned OFF and the brake is turned ON, the operating point of the transmission 4 is shifted to the operating point (point A) at that point as the speed decreases, , Changes from point B to point C through point C along the cost line, and finally changes from point D toward zero (0) along the lowest line.

Here, in the shift map shown in Fig. 6, the predetermined rotation speed Nt2, which is one of the cost stop conditions, coincides with the intersection of the highest line, the coast line and the coast-stop permissible vehicle speed VSP2.

Therefore, when the vehicle speed continues to fall and becomes the coast-stop permissible vehicle speed VSP2 or less, the turbine rotation speed Nt at the time t2 becomes equal to or less than the predetermined rotation speed Nt2 for judging the execution of the coasting stop. (Fig. 7 (a): vehicle speed, turbine rotation speed Nt, coast stop reference, Fig. 5: step 102, Yes).

In the embodiment, the shift map in which the predetermined rotation speed Nt2 coincides with the intersection of the highest line and the coast line and the coast-stop permitted vehicle speed VSP2 is exemplified. However, the predetermined rotation speed Nt2 does not necessarily coincide with these intersection points.

Returning to the explanation of the operation example, when the cost stop condition is satisfied (Fig. 5: step 102, YES), the coast stop is started at the time point t2 (Fig. 7 (a) Step 103].

Then, with the start of the coast stop as a trigger, the fuel injection to the engine 1 is stopped, the engine 1 is stopped, and the electric oil pump 10e is started (Fig. 7 (a) Engine speed Ne, electric oil pump].

Therefore, when the hydraulic pressure generated by the electric oil pump 10e is greater than the hydraulic pressure generated by the mechanical oil pump 10m which is stopped by stopping the engine, the hydraulic oil is changed to the hydraulic oil from the mechanical oil pump 10m, The hydraulic pressure from the hydraulic cylinder 10e is supplied to the auxiliary transmission mechanism 30, the hydraulic cylinders 23a and 23b, and the like.

Here, in the transmission 4 of the embodiment, the engagement state of the high-speed clutch 33 of the auxiliary transmission is maintained until the vehicle stops, in preparation for a case where there is a re-acceleration request during the course stop have.

In order to maintain the engaged state of the high-speed clutch 33 (frictional engagement element) of the auxiliary transmission mechanism 30 at the coasting stop, the torque (upstream-side torque Tu) input from the upstream side of the auxiliary transmission mechanism 30, The hydraulic pressure corresponding to the difference of the torque (the downstream side torque Td)

Therefore, in the embodiment, the predetermined rotation speed Nt2, which is one of the above-described coasting stop conditions, is set to be the same as the predetermined rotation speed Nt2 due to the turbine rotation when the engagement state of the high speed clutch 33 can be maintained by the oil pressure that can be generated in the electric oil pump 10e Is set to the upper limit value of the speed Nt.

Here, the predetermined rotation speed Nt2 will be described.

Fig. 8 is a diagram schematically showing a power transmission path from the engine to the wheels, and Fig. 9 is a view for explaining the difference between the input torque on the upstream side and the input torque on the downstream side in the friction engagement element.

As shown in Fig. 8, the rotational driving force of the engine is transmitted to the wheels through the torque converter T / C of the automatic transmission and the auxiliary transmission mechanism (frictional engagement element).

In order to maintain the engagement state of the frictional engagement element at the time of the coasting stop, it is necessary to adjust the hydraulic pressure according to the difference between the torque (the upstream side torque Tu) input from the upstream side of the frictional engagement element and the torque (the downstream side torque Td) .

Here, the downstream-side torque Td is a torque according to the deceleration of the vehicle caused by the stepping of the brake, and becomes larger as the amount of stepping of the brake becomes larger.

The upstream-side torque Tu is a torque corresponding to the output rotational speed of the torque converter T / C (hereinafter referred to as the turbine rotational speed Nt) and is a difference between the rotational speeds of the impeller I and the turbine T of the torque converter T / ) Becomes larger.

Here, at the coasting stop, since the engine stops, the rotational speed of the impeller I to which the output rotation of the engine is input is zero. On the other hand, the rotational speed Nt of the turbine T in the torque converter T / C increases in proportion to the vehicle speed because the friction engagement element is engaged. Therefore, the larger the vehicle speed at the coasting stop, the larger the upstream-side torque Tu.

Assuming that there is no change in the stepping amount of the brake pedal during coast stop, that is, there is no change (constant value) in the downstream side torque Td, the difference between the upstream side torque Tu and the downstream side torque Td becomes larger in the following two cases to be.

(1) The vehicle is about to stop. In this case, the upstream-side torque Tu decreases with respect to the downstream-side torque Td (see reference symbol a in Fig. 9), and the difference? Ta increases.

(2) When the turbine rotation speed Nt is increased. In this case, the upstream side torque Tu becomes larger with respect to the downstream side torque Td (see the signs b and c in Fig. 9), and the differences? Tb and? Tc become larger.

Here, in the case of (1) above, since the coast stop is not generally executed during the rapid deceleration in which the downstream side torque Td becomes excessively high, immediately before the vehicle stops, (The vehicle speed is almost zero), the upstream-side torque Tu becomes substantially zero (the upstream-side torque Tu≈0) and the downstream-side torque Td≈the differential. In this case, since the difference is relatively small, the engagement state of the friction engagement element can be maintained by the hydraulic pressure that can be supplied from the electric oil pump.

In the case of (2) above, if the vehicle speed becomes large, the turbine rotation speed Nt also becomes large, and the difference also becomes large. In this case, depending on the vehicle speed, the engagement state of the frictional engagement element can not be maintained by the hydraulic pressure that can be supplied from the electric oil pump.

For example, as shown in Fig. 9, when the difference is larger than the torque width Eop that allows the frictional engagement element to be maintained in the engaged state by the hydraulic pressure supplied from the electric oil pump because the vehicle speed is large, It can not be maintained in the fastened state.

Therefore, in the prior art, there is a difference in the area where the engagement state of the frictional engagement element can be maintained by the hydraulic pressure that can be supplied from the electric oil pump, that is, a region having a low vehicle speed (vehicle speed VSP1 in the lower vehicle speed region ), The cost stop was allowed.

On the other hand, in the shift map according to the embodiment, the coast-stop permissible vehicle speed VSP2 is set to the higher-speed region side (the higher-speed region side near the vehicle speed VSP1) where there are a plurality of turbine rotation speeds that can be taken for one vehicle speed , And the coasting operation region is a region surrounded by a straight line from zero to point D, point B, point D, and point F.

The upper limit value of the turbine rotation speed Nt when the engagement state of the high speed clutch 33 can be maintained by the hydraulic pressure that can be generated in the electric oil pump 10e out of the area surrounded by the point B, the point D and the point F, (The region surrounded by the point D and the point D 'point B in the figure and the straight line from the zero point to the point D) than the turbine rotation speed Nt2 is equal to the rotation speed Nt2, As shown in Fig.

Thus, the predetermined rotation speed Nt2 is set to the upper limit value of the turbine rotation speed Nt when the engagement state of the high-speed clutch 33 can be maintained by the oil pressure that can be generated in the electric oil pump 10e, The engagement state of the high-speed clutch 33 is maintained immediately after the start time t2. Therefore, after time t2, the input shaft and the output shaft of the auxiliary transmission mechanism 30 are reduced at the same rotational speed (see Fig. 7 (a): the auxiliary speed change mechanism).

Therefore, when the input shaft and the output shaft of the auxiliary transmission mechanism 30 are decreasing to the same rotational speed after the time t2, there is a demand for a re-acceleration, the rotational driving force of the engine is quickly changed from the upstream side to the downstream side of the frictional engagement element And the like.

[Operation Comparative Example 1]

When the vehicle is traveling at a vehicle speed higher than the coast-stop permissible vehicle speed VSP2 of the transmission 4 according to the embodiment, for example, in the case of the transmission according to the conventional example in which only the vehicle speed VSP is considered, The case where the vehicle speed is lowered by the brake: ON and the case where the speed ratio of the transmission 4 changes from the highest line to the lowermost line via the cost line will be described for comparison with the operation example 1.

In the transmission according to the conventional example, the coast-stop permissible vehicle speed VSP1 is set to a lower-speed range side than the coast-stop permissible vehicle speed VSP2 of the transmission 4 according to the embodiment, and the vehicle speed and the turbine rotation speed are set to one- .

6 and 7 (b), when the accelerator is turned off and the brake is turned on (at time t1), the operating point of the transmission is shifted from the operating point (point A) And then changes along the cost line from point B to point C to point D and finally changes from point D to zero along the characteristic line Low.

In the case of the conventional transmission, the coast stop is not executed during the time when the turbine rotation speed is not used for judging the start of the coast stop and the vehicle speed becomes less than or equal to the coast stop permitted vehicle speed VSP1.

Therefore, if the vehicle speed is lowered due to the accelerator: off or brake: ON when the vehicle is running at a vehicle speed higher than the coast-stop permissible vehicle speed VSP2, coast stop is not started until time t3 at which the coast- (Fig. 7 (b): vehicle speed, coast stop).

Therefore, when the vehicle speed reduction rate is the same, the transmission 4 according to the embodiment starts the coast stop before the transmission according to the conventional example. Therefore, in the transmission according to the embodiment, since the coast stop can be performed earlier than the transmission according to the conventional example by the time difference from the time t2 to the time t3 in Fig. 7, the fuel economy can be improved by that amount.

10 is a timing chart for explaining another example of the operation of the transmission 4. Fig. 10 (a) is a timing chart for explaining the start-up determination of the coast-stop according to the embodiment in which the coast-stop permissible vehicle speed VSP2 and the turbine speed Nt are considered. (B) is a diagram showing a case of the conventional example in which only the vehicle speed VSP2 is considered.

In the drawings, &quot; CS area &quot; means &quot; area where cost stop is executed &quot;.

[Operational example 2]

When the vehicle speed is decreased from the vehicle speed higher than the coast-stop permissible vehicle speed VSP2 while the accelerator pedal is turned off and the brake is turned on while accelerating the vehicle and the deceleration rate of the vehicle speed is high but the decrease in the turbine rotation speed is slow .

Also in this case, it is assumed that, in the transmission 4 according to the embodiment, the coast-stop permissible vehicle speed VSP2 is set to the higher-speed range side than the vehicle speed VSP1 of the start condition of the conventional coast-stop.

For example, when the L range is selected by the shift lever and the transmission ratio is fixed at the lowermost line, when the accelerator pedal is stepped and the vehicle is oscillated and accelerated, the operating point of the transmission 4, (The right side in Fig. 6) via the point D and the point D 'from zero (0).

Then, after the vehicle speed becomes higher than the coast-stop permissible vehicle speed VSP2, when the brake is stopped by stopping the acceleration (turning off the accelerator) when the vehicle reaches the operating point E, the operating point of the transmission 4 is thereafter (0) along the lowermost line from the operating point (point E) in Fig.

When the vehicle speed continues to fall below the coast-stop permissible vehicle speed VSP2 or less, at the time point (time t2 in Fig. 10A, point F in Fig. 6) d, the conditions a to c are established.

At this point, however, the turbine rotation speed Nt is larger than the predetermined rotation speed Nt2 (Fig. 10A: vehicle speed, turbine rotation speed Nt, cost stop reference, Fig. 5: step 102, Stop is prohibited (Fig. 10: step 104).

When the vehicle speed is lowered even after the coast stop conditions a to c are established, the turbine rotation speed Nt becomes equal to or less than the predetermined rotation speed Nt2 in the near future. Thus, at time t3 when the speed ratio is lowered to the point D ' , So that all the cost stop conditions a to d are satisfied (Fig. 10 (a): vehicle speed, turbine rotation speed Nt, coast stop reference, Fig. 5: step 102, Yes).

Thus, the coast stop is started at time t3 (Fig. 10 (a): Coast stop reference, Fig. 5: step 103).

Then, with the start of the coast stop as a trigger, the fuel injection to the engine 1 is stopped, the engine 1 is stopped, and the electric oil pump 10e is started (Fig. 10 (a) Engine speed Ne, electric oil pump].

Therefore, when the hydraulic pressure generated by the electric oil pump 10e is greater than the hydraulic pressure generated by the mechanical oil pump 10m which is stopped by stopping the engine, the hydraulic oil is changed to the hydraulic oil from the mechanical oil pump 10m, The hydraulic pressure from the hydraulic cylinder 10e is supplied to the auxiliary transmission mechanism 30, the hydraulic cylinders 23a and 23b, and the like.

Here, in the transmission 4 of the embodiment, the engagement state of the high-speed clutch 33 of the auxiliary transmission is maintained until the vehicle stops, in preparation for the case where there is a re-acceleration request during coast stop have.

As described above, in order to maintain the engaged state of the high-speed clutch 33 (frictional engagement element) of the auxiliary transmission mechanism 30 at the coasting stop, the torque input from the upstream side of the auxiliary transmission mechanism 30 The torque Tu and the torque input from the downstream side (the downstream side torque Td).

Therefore, in the embodiment, the predetermined rotation speed Nt2 that defines the above-described start condition of the coasting stop is a predetermined rotation speed Nt2 when the engagement state of the high-speed clutch 33 can be maintained by the oil pressure that can be generated by the electric oil pump 10e And is set to the upper limit value of the turbine rotation speed Nt.

Therefore, the engagement state of the high speed clutch 33 is maintained even after the time t3 at which the coast stop is started, so that the input shaft and the output shaft of the auxiliary speed change mechanism 30 decrease at the same rotational speed even after the time t3.

Therefore, after the time t3, when the input shaft and the output shaft of the auxiliary transmission mechanism 30 are decreasing at the same rotational speed and there is a re-acceleration request, the rotational drive force of the engine is quickly transmitted from the upstream side to the downstream side of the frictional engagement element .

[Operation Comparative Example 2]

Hereinafter, the case where the coast-stop permissible vehicle speed is simply changed from the initial coast-stop permissible vehicle speed VSP1 to the coast-stop permissible vehicle speed VSP2 on the higher-order speed side in the transmission according to the conventional example in which only the vehicle speed is considered, The case where the vehicle speed is decreased from the vehicle speed higher than the coast-stop permissible vehicle speed VSP2 and the vehicle speed is lowered but the lowering of the turbine rotation speed is slow is described as the operation example 2 For the comparison with.

For example, when the L range is selected by the shift lever and the transmission ratio is fixed to the lowermost line, if the accelerator pedal is stepped and the vehicle is oscillated and accelerated, the operation of the transmission 4 The point changes from zero (0) to point D and point D 'to the high-speed side (right side in the figure) along the lowermost line.

Then, after the vehicle speed becomes higher than the coast-stop permissible vehicle speed VSP2, when the brake is stopped by stopping the acceleration (turning off the accelerator) when the vehicle reaches the operating point E, the operating point of the transmission 4 is shifted Is changed to zero (0) along the lowest line from the operating point (point E) at that point since it is fixed to the lowest line.

When the vehicle speed continues to fall and becomes equal to or less than the coast-stop permissible vehicle speed VSP2, the coast stop is started at the time point t2 (see Fig. 10B, vehicle speed and coast stop, see Fig. 6: .

Thus, fuel injection to the engine 1 is stopped with the start of the coast stop as a trigger, and the engine 1 is stopped and the electric oil pump 10e is started (Fig. 10 (b) , Engine speed Ne, electric oil pump].

Therefore, when the hydraulic pressure generated by the electric oil pump 10e is greater than the hydraulic pressure generated by the mechanical oil pump 10m which is stopped by stopping the engine, the hydraulic oil is changed to the hydraulic oil from the mechanical oil pump 10m, The hydraulic pressure from the hydraulic cylinder 10e is supplied to the auxiliary transmission mechanism 30, the hydraulic cylinders 23a and 23b, and the like.

However, as shown in Fig. 6, the turbine rotational speed Nt3 corresponding to the point F is the maximum rotational speed at which the high-speed clutch 33 of the auxiliary transmission can be maintained in the engaged state by the oil pressure from the electric oil pump 10e Is higher than the speed Nt2, the high-speed clutch 33 can not be engaged and becomes in the slip state.

As a result, since the high-speed clutch 33 is slipped immediately after the time t2 at which the coast stop is started and a difference occurs between the rotational speeds of the input shaft and the output shaft of the auxiliary transmission mechanism 30 after the time t2, There is a possibility that it may have a sense of incongruity in the behavior of This state means that the turbine rotation speed Nt is maintained for a while after the time point t3 when the turbine rotation speed Nt reaches the upper limit rotation speed Nt2 at which the high speed clutch 33 can be maintained in the engaged state by the oil pressure from the electric oil pump 10e (Fig. 10 (b): turbine rotation speed Nt, reference to the auxiliary transmission mechanism input / output shaft rotation speed).

As described above, in the transmission according to the conventional example in which only the vehicle speed is considered, the allowable vehicle speed at the coast stop is simply changed from the originally permitted vehicle speed VSP1 to the vehicle speed VSP2 at the higher speed side so that the vehicle speed region, The fastening state of the frictional engagement element (high-speed clutch 33) may not be maintained.

On the other hand, in the transmission 4 according to the embodiment, it is determined whether or not the start of the coast stop is possible based on the turbine rotation speed Nt as well as the vehicle speed.

Therefore, even if the coasting start vehicle speed is set to the higher speed side than the corresponding vehicle speed range where the rotational speed of the turbine is one-to-one with respect to the vehicle speed, the oil pressure that can be supplied from the electric oil pump 10e, A coast stop is executed only when the turbine rotation speed at which the state can be maintained can be prevented from becoming a behavior causing a driver to feel a sense of incongruity at coast stop.

Therefore, the coast stop can be started from the higher speed side than in the case of the conventional transmission, and the fuel consumption can be improved.

In the embodiment described above, the case where the transmission ratio is fixed to the lowermost line has been described as an example. Here, in a state in which the D range is selected, the accelerator pedal is stepped to cause the vehicle to oscillate and accelerate so that the vehicle speed reaches between the start stopping vehicle speed VSP1 of the conventional coast stop and the vehicle speed VSP2 higher than the start vehicle speed VSP1, Even when the accelerator pedal is released and the vehicle is decelerated, it may happen that the fastening element can not be held in the engaged state during the coast stop. Therefore, the operation of the transmission 4 according to the embodiment in this case will be described below with reference to Fig.

While the vehicle is oscillating and accelerating, the operating point of the transmission 4 changes along the lowest line from zero (0) to point D and point D 'toward the higher speed side (right side in the figure). When the accelerator pedal is released and the brake pedal is stepped at the point when the operating point reaches the point G, the upshift is started at that point, and the operating point is shifted to the low rotational speed side . Then, the operating point then reaches point I on the cost line from point G via point H, then reaches point D on the lowest line along the cost line, and finally along the lowest line, zero (0).

In the transmission 4 according to the embodiment, the vehicle speed VSPa at that time point is lower than the coast-stop start vehicle speed VSP2 (VSPa < VSP2) at the point of time when the accelerator pedal is released, but the turbine rotation speed Nt4 is lower than the above- Nt2 (Nt4 > Nt2), all of the cost stop conditions a through e are not established. Therefore, at the time point D when the accelerator pedal is released, coast stop is prohibited.

If the vehicle speed and the turbine rotation speed decrease as the coast stop is prohibited, the operating point of the transmission 4 continues to decrease toward the point I along the chain line in the figure. Then, when the operating point reaches the point H on the way to the point I, the turbine rotation speed Nt at that point becomes equal to or smaller than the above-mentioned predetermined rotation speed Nt2 (Nt? Nt2). Therefore, from that point on, the coast stop is started.

In the case of the transmission according to the conventional example in which only the vehicle speed is considered, the allowable vehicle speed at the coasting stop is simply changed from the initial permitted vehicle speed VSP1 to the vehicle speed VSP2 at the higher speed side so that the vehicle speed region, The coast stop is started at the point G when the accelerator pedal is released.

Then, the turbine rotational speed Nt4 at the point G when the accelerator pedal is released is set to be higher than the upper limit rotational speed Nt2 that can keep the high-speed clutch 33 of the auxiliary transmission at the engaged state by the oil pressure from the electric oil pump 10e The high-speed clutch 33 can not be engaged, and the clutch is in a slip state.

As described above, in the embodiment, the torque converter 2 (fluid transmission mechanism) disposed between the engine 1 (drive source) and the drive wheel 7,

A speed change mechanism 30 (friction engagement element) arranged in series with the torque converter 2,

A mechanical oil pump 10m (oil pressure source) driven by the engine 1,

A controller 12 (drive source control means) for stopping the engine 1 when a predetermined stop condition is established at the time of deceleration of the vehicle,

A motor-driven oil pump 10e driven by the battery 13 while the engine 1 is stopped,

A vehicular automatic transmission in which a frictional engagement element of a negative speed change mechanism (30) is held in a locked state by an oil pressure from an electric oil pump (10e) while the engine (1) is stopped,

The controller 12 is configured to determine whether or not the engine 1 can be stopped based on the turbine rotation speed Nt (output shaft rotation speed) of the torque converter 2 in addition to the above-described stop condition.

Here, the stop conditions are the following a to c.

a: The foot is released from the accelerator pedal (accelerator opening APO = 0)

b: Brake pedal is stepped (brake fluid pressure is higher than the specified value)

c: When the vehicle speed is equal to or less than a predetermined vehicle speed

This configuration makes it possible to determine not only the vehicle speed but also the stopping of the engine 1 in consideration of the output shaft rotation speed (turbine rotation speed Nt) of the torque converter 2 which contributes to the engagement of the friction engagement element of the auxiliary transmission mechanism 30 do.

If the vehicle speed at which the engine 1 is allowed to stop (the coast-stop permissible vehicle speed) is widened to the higher-speed side, even in the same vehicle speed, the turbine rotational speed Nt can be different depending on the speed ratio. Therefore, Even if the vehicle speed is met, even when the engine 1 is stopped, the turbine rotation speed Nt is too high and the torque input to the friction engagement element is large. Therefore, friction due to the hydraulic pressure from the electric oil pump 10e The fastening elements may not be held in the fastened state.

In the above-described configuration, in consideration of the turbine rotation speed Nt contributing to the engagement of the frictional engagement element, the frictional engagement element is engaged with the oil pressure from the electric oil pump 10e, for example, (Coast stop permissible vehicle speed) permitting the engine 1 to stop is set to the high-speed side by allowing the engine 1 to stop (start of coast-stop) when the rotational speed at which the engine 1 can be maintained It is possible to suitably prevent the frictional engagement element from becoming non-engaged when the engine 1 is stopped.

Thereby, it is possible to prevent the driver from feeling a discomfort in the behavior of the transmission 4 or the like. In addition, since the engine 1 can be stopped at the higher speed side, the opportunity to stop the engine 1 can be increased, thereby improving the fuel economy.

The controller 12 is configured to allow the engine 1 to stop when the turbine rotation speed Nt is equal to or lower than a predetermined rotation speed Nt2 determined by the hydraulic pressure at which the electric oil pump 10e can generate.

Whether or not the frictional engagement element can be maintained in the engaged state is determined in accordance with the oil pressure at which the electric oil pump 10e can be generated. The state in which the frictional engagement element can be maintained in the engaged state by the hydraulic pressure from the electric oil pump 10e can be obtained even if the vehicle speed at which the engine 1 is allowed to stop (the coast-stop permitted vehicle speed) , The engine 1 can be stopped (start of coast stop).

Thereby, the vehicle speed at which the engine 1 is allowed to stop can be widened toward the higher-speed range side, so that the opportunity for stopping the engine 1 can be increased. As a result, the time required to stop the engine 1 is increased, and the fuel economy is improved by that amount.

Further, since the frictional engagement element can be suitably prevented from being brought into the slip state, the rotational driving force of the engine 1 can be quickly transmitted from the upstream side to the downstream side of the frictional engagement element, It is possible to suitably prevent the ash attribution of the vehicle on which the transmission is mounted from being lowered.

The predetermined rotation speed Nt2 is set to an upper limit value of the turbine rotation speed Nt capable of maintaining the engagement state of the frictional engagement element at an oil pressure that can be generated by the electric oil pump 10e.

With this configuration, the engine 1 is stopped when the turbine rotation speed Nt is equal to or lower than the rotation speed Nt2 that defines the upper limit at which the frictional engagement element can be held in the engaged state by the hydraulic pressure from the electric oil pump 10e .

This makes it possible to appropriately prevent the frictional engagement element from being brought into the slip state, so that the rotational driving force of the engine 1 can be quickly transmitted from the upstream side to the downstream side of the frictional engagement element when there is a re- It is possible to suitably prevent the ash attribution of the vehicle equipped with the automatic transmission from being deteriorated.

In addition, since the vehicle speed at which the engine 1 is allowed to stop can be widened to the higher-speed region side, the chance that the engine 1 is stopped can be increased.

As a result, the time required to stop the engine 1 is increased, and the fuel economy is improved by that amount.

The predetermined stopping condition includes a condition that the vehicle speed is equal to or less than the allowable vehicle speed VSP2 permitting the stop of the driving source in the driving state just before stopping when the vehicle is decelerating. (A region surrounded by points B, D and D 'in Fig. 6) where the turbine rotation speed Nt in a region where a plurality of turbine rotation speeds that can be taken with respect to one vehicle speed in the engine is within a predetermined rotation speed Nt2 And is set to the high-speed side.

With this configuration, the permitted vehicle speed VSP2 is a vehicle speed determined according to the turbine rotation speed Nt2 when the frictional engagement element can be held in the engaged state by the oil pressure that can be generated by the electric oil pump 10e, Can be set. Therefore, the cost stop can be executed at the higher speed side as much as possible, so that the improvement of the fuel economy can be further expected.

In the above embodiment, the present invention has been described by taking the case where the present invention is applied to a belt-type continuously variable transmission provided with a negative speed change mechanism (30) on the downstream side of the variator (20) The present invention is also applicable to a belt type continuously variable transmission provided with the auxiliary transmission mechanism 30 or an automatic transmission that realizes a desired speed change stage by a combination of engagement and disengagement of a plurality of engagement elements.

In the above-described embodiment, the case where the &quot; driving source &quot; is an engine is exemplified. However, the present invention is not limited to this, and may be a motor or a configuration in which torque is inputted from both the engine and the motor.

In the above embodiment, the case where the cost stop condition is the following a to d is exemplified.

a: The foot is released from the accelerator pedal (accelerator opening APO = 0)

b: Brake pedal is stepped (brake fluid pressure is higher than the specified value)

c: Vehicle speed is allowed to coast stop Vehicle speed VSP2 or less

d: the turbine rotation speed is not more than the predetermined rotation speed Nt2

In addition to these a to d, &quot; the lockup clutch is released &quot; may be included in the cost stop condition.

Claims (4)

A fluid transmission mechanism disposed between the drive source and the drive wheel,
A friction engagement element arranged in series with the fluid transmission mechanism,
A hydraulic pressure source driven by the drive source,
Drive source control means for stopping the drive source when a predetermined stop condition is established at the time of deceleration of the vehicle,
And another hydraulic pressure source driven by another driving source different from the driving source while the driving source is stopped,
And the frictional engagement element is held in the engaged state by the hydraulic pressure from the other drive source while the drive source is stopped,
Wherein the drive source control means determines the stop of the drive source based on the output rotational speed of the fluid transmission mechanism. The method according to claim 1,
Wherein the drive source control means
And permits the drive source to stop when the output rotational speed of the fluid transmission mechanism is equal to or lower than a predetermined rotational speed determined according to the oil pressure capable of generating the other oil pressure source. 3. The method of claim 2,
Characterized in that the predetermined rotation speed is an output rotation speed of the fluid transmission mechanism and is set to an upper limit value at which the engagement state of the friction engagement element can be maintained at an oil pressure that can be generated by the other oil pressure source Transmission. 4. The method according to any one of claims 1 to 3,
Wherein the predetermined stopping condition includes a condition that the vehicle speed is equal to or less than a permissible vehicle speed allowing the stop of the drive source.

Images