JP2001235015A - Control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an automatic transmission capable of keeping a driver from feeling discomfort by limiting the reverse motion of the vehicle on an uphill road, for reducing difference between the normal D-range time and neutral control time. SOLUTION: The control device includes a torque converter for transmitting an engine driving force to a transmission mechanism; a C2 clutch which is brought into engagement when a forward drive range is selected; a one-way clutch F locked by engagement of the C2 clutch to achieve the first forward speed; and a B1 brake for locking the one-way clutch F by engagement to prevent reverse rotation of the output shaft of the transmission mechanism. When a predetermined requirement is met with the vehicle at standstill, the C2 clutch is almost released to perform neutral control. Means are provided for controlling the engagement hydraulic pressure of the B1 brake so that when the vehicle backs during the neutral control, a speed equal to or less than a limit reverse speed is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an automatic transmission, and more particularly to a control device for an automatic transmission having a function of performing neutral control.

[0002]

2. Description of the Related Art Generally, an automatic transmission is provided with a transmission mechanism and a fluid transmission device such as a torque converter. When a driving range such as a D range is selected, the fluid transmission device is brought into a rotation transmitting state and a transmission mechanism is provided. Is a state in which the input shaft and the output shaft are mechanically connected. Therefore, when the vehicle is in a stopped state, the engine driving force is consumed due to slippage of the fluid in the fluid transmission, and power loss occurs.

In order to solve such a problem, an automatic transmission that performs neutral control has been proposed. Neutral control means that, even in the travel range, when the vehicle is stopped, the clutch in the transmission mechanism is in a state immediately before engagement, and the input shaft and the output shaft of the transmission mechanism are in the power-off state, and the fluid in the fluid transmission device Control that reduces the engine load that causes slippage, reduces power loss, and improves fuel efficiency.

[0004] However, if the neutral control is performed, it becomes impossible to obtain a creep force due to slippage of the fluid in the fluid transmission device. Therefore, when the vehicle starts on a sloping road such as an uphill road, a phenomenon occurs in which the vehicle moves backward. . To cope with this problem, an automatic transmission that performs neutral control also uses hill hold control. Hill hold control means that a specific brake included in the speed change mechanism is engaged to lock the one-way clutch that achieves the first forward speed, and to establish the second speed state, thereby achieving the output shaft of the speed change mechanism. To prevent reverse rotation of. Such an automatic transmission using both the neutral control and the hill hold control is disclosed in, for example, Japanese Patent Application Laid-Open Nos.
It is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-51165.

[0005]

However, in the case of an automatic transmission using both the neutral control and the hill hold control, when the hill hold control is performed on an uphill road, the vehicle does not reverse at all, but the hill hold control is performed. When the control is released to return to the normal D range state, the vehicle suddenly moves backward. In other words, there is a large difference in the reverse feeling depending on the presence or absence of the hill hold control, and the driver may feel uncomfortable.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic transmission capable of eliminating a driver's discomfort by restricting the vehicle from retreating on an uphill road and reducing the difference between the normal D range and the neutral control. It is to provide a control device.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a fluid transmission device for transmitting an engine driving force to a speed change mechanism is engaged when a forward travel range is selected. A one-way clutch that is locked by engagement of the clutch to achieve the first forward speed, and a brake that locks the one-way clutch by engagement and prevents reverse rotation of the output shaft of the transmission mechanism,
In an automatic transmission in which the clutch is substantially disengaged and the neutral control is performed when a predetermined condition is satisfied while the vehicle is stopped, when the vehicle retreats during the neutral control, the brake is controlled so as to be equal to or lower than a limit reverse speed. A control device for an automatic transmission, characterized by comprising means for controlling the engagement hydraulic pressure of the automatic transmission.

If the neutral control is started while the vehicle is stopped on an uphill road, no creep force is generated.
When the brake pedal is released, the vehicle starts moving backward. In the present invention, instead of the conventional hill hold control, the slip speed of the brake is controlled to limit the retreat speed on the uphill road to the limit retreat speed or less. Therefore, even when the neutral control is performed, the same reverse feeling as in the normal D range (during the non-neutral control) can be obtained, and the driver does not feel uncomfortable. Further, in the conventional hill hold control, since the vehicle cannot retreat at all, when the driver wants to slowly retreat on an uphill road, another operation such as switching to the R range is required. However, in the present invention, only the brake pedal is loosened. The vehicle can be slowly moved backward, so that no special operation is required. According to the present invention, since the brake is not completely engaged and can be slid even when the brake is fully engaged, no engagement shock is generated due to the engagement of the brake. Further, even when the brake control is performed, since the automatic transmission is in the neutral state internally, the fuel efficiency is improved and the unpleasant vibration of the vehicle body can be suppressed.

There are various methods for setting the limit reverse speed as shown below. (1) The limit reverse speed is set to a constant value (for example, about 5 km / h) irrespective of the gradient of the road surface. If the reverse speed is lower than that, the brake control is not performed (the brake is released), and the constant value is set. If it is attempted to exceed the limit, a method of limiting the brake engagement hydraulic pressure to a fixed value or less by feedback control. (2) A method in which the limit reverse speed is set in advance according to the road surface gradient, the road surface gradient is detected, and feedback control is performed so that the reverse speed is equal to or less than the limit reverse speed. The limit retreat speed in this case may be set stepwise according to the gradient, or may be set continuously.

If the start condition of the neutral control is only the vehicle speed and the operation of the foot-operated brake or the parking brake, the driver can easily recognize whether or not the neutral control is being performed. However, when other factors (for example, throttle opening, oil temperature, etc.) are included in the start condition, there may be a case where the vehicle retreats and a case where the vehicle retreats despite performing the same operation on the uphill road. , The driver may feel uncomfortable. In particular, when the start condition includes a condition that is difficult for the driver to recognize, such as the oil temperature, a sense of discomfort is likely to occur. Even in such a case, according to the present invention, since the vehicle always moves backward, there is an effect that the driver does not feel uncomfortable.

It is desirable that the limit retreat speed substantially coincides with the retreat speed on the uphill road in a state where the creep force is applied at the first forward speed. The limit retreat speed may be set to a constant value, but the retreat speed on an uphill road in a state where the creep force is applied in the first forward speed is different depending on a gradient of a road surface or the like. Therefore, by making the limit reverse speed substantially equal to the reverse speed at the first forward speed, the normal D
Driving with the same feeling as range driving becomes possible. As a method of making the limit reverse speed substantially equal to the reverse speed in the first forward speed, a map of the limit reverse speed in the D range according to the gradient is set in advance, and the neutral control is performed so as to follow this map. There is a method of controlling the reverse speed at the time, or a method of estimating the limit reverse speed from the creep force in the actual D range, the gradient of the road surface, and the like.

[0012]

FIG. 1 shows an example of an automatic transmission for a vehicle according to the present invention. This automatic transmission includes a torque converter 1, an input shaft 2, to which engine power is transmitted via the torque converter 1, three clutches C1 to C3, two brakes B1, B2, a one-way clutch F, a Ravigneaux type planetary gear. A mechanism 4, an output gear 5, an output shaft 7, a differential device 8, and the like are provided. In this embodiment, the clutch which is almost released during the neutral control according to the present invention refers to the C2 clutch, and the brake whose engagement hydraulic pressure is controlled to be equal to or lower than the limit reverse speed when the vehicle retreats refers to the B1 brake. .

The forward sun gear 4a of the planetary gear mechanism 4
Is connected to the input shaft 2 via a C1 clutch, and the forward sun gear 4a is also connected to the transmission case 6 via a B1 brake. The rear sun gear 4b is connected to the input shaft 2 via a C2 clutch. The carrier 4c is connected to the input shaft 2 via the intermediate shaft 3 and a C3 clutch. Further, the carrier 4c is connected to the transmission case 6 via a B2 brake, and is also connected to the transmission case 6 via a one-way clutch F that allows only the forward rotation (engine rotation direction) of the carrier 4c. The carrier 4c has two types of pinion gears 4d and 4
e, the forward sun gear 4a meshes with a long pinion 4d having a long shaft length, and the rear sun gear 4b meshes with the long pinion 4d via a short pinion 4e having a short shaft length. The ring gear 4f that meshes with only the long pinion 4d is connected to the output gear 5.
The output gear 5 is connected to a differential 8 via an output shaft 7.

The above automatic transmission comprises clutches C1, C2,
C3, brakes B1, B2 and one-way clutch F
As shown in FIG. 2, four forward speeds and one reverse speed are realized by the operation of. In FIG. 2, ● indicates the operation state of the hydraulic pressure. The B2 brake is engaged at the time of reverse and the first speed, but is engaged at the first speed only in the L range. FIG. 2 also shows operating states of first to fourth solenoid valves (SOL1 to SOL4) 22 to 25 described later. ○ indicates an energized state, X indicates a non-energized state, and △ indicates a temporary energized state. This operation table shows the operation in the steady state.

FIG. 3 shows an example of a hydraulic control device used in the automatic transmission. The hydraulic control device includes an oil pump 10, a regulator valve 11, a manual valve 1
2. Solenoid modulator valve 13, sequence valve 15, fail-safe valve 16, B1 pressure control valve 17, C2 pressure control valve 18, C2 lock valve 1.
9, C3 pressure control valve 20, B2 pressure control valve 21, first to fourth solenoid valves 22 to 25, electronic control unit 3
0 or the like. The electronic control unit 30 includes a vehicle speed, a throttle opening (accelerator opening), an operation signal of a foot-operated brake (brake signal), a shift position signal for detecting a position of a shift lever, a lubricating oil temperature inside the transmission (oil temperature). ) Is input to control the first to fourth solenoid valves 22 to 25 according to the driving state of the vehicle. If necessary, signals such as the turbine speed, the engine speed, and the gradient of the road surface may be input to the electronic control unit 30.

The first solenoid valve 22 is for B1 brake control, the second solenoid valve 23 is for C2 clutch control, and the third solenoid valve 24 is for C3 clutch control and B2 brake control. Third
The reason that the solenoid valve 24 serves both for controlling the C3 clutch and for controlling the B2 brake is that the B2 brake does not operate in the D and 2 ranges but is used only for the engine brake control in the L range and the transient control in the R range. This is because they do not interfere with the C3 clutch operated in the D range. The fourth solenoid valve 25 is a valve for switching the sequence valve 15 at the time of switching transition between the L range (first speed) and the R range. As described above, since the first to third solenoid valves 22 to 24 need to perform delicate hydraulic control, a duty solenoid valve or a linear solenoid valve is used, and the fourth solenoid valve 25 is an ON / OFF switching valve. Good.

The regulator valve 11 is an oil pump 1
The discharge pressure of 0 a valve pressure regulated to a predetermined line pressure P _L, the manual valve 12, and supplies the line pressure P _L to the solenoid modulator valve 13, B2 pressure control valve 21. As shown in FIG. 4, the regulator valve 11 includes a spool 11b urged rightward by a spring 11a, and a plug 11c separate from the spool 11b is provided at the left end. The discharge pressure of the oil pump 10 is input to the port 11d, and the port 11e is connected to the suction side of the oil pump 10. The line pressure P _L is fed back to the right end of the port 11f. The C1 clutch pressure _PC1 is input to the left end port 11h only during reverse (R), and the line pressure during reverse is adjusted to be higher than during forward travel.

The manual valve 12 changes the spool 12a to L, 2, D, N,
The range can be switched between R and P. Then, selectively outputs the line pressure P _L input from the input port 12b from the output port 12c, or the output 12d for backward for forward.

The solenoid modulator valve 13 is a valve for supplying a constant source pressure to each of the solenoid valves 22 to 25, and has a spool 13b urged leftward by a spring 13a as shown in FIG. The input port 13c is input line pressure P _L from regulator valve 11, the solenoid modulator pressure Psm each solenoid valve 22-2 from the output port 13d
5 and output to the right end signal port 19c of the C2 lock valve 19. The port 13e is a drain port. The output pressure Psm is fed back to the left end port 13f, whereby the solenoid modulator pressure Ps
m is adjusted to a hydraulic pressure corresponding to the load of the spring 13a.

The B1 pressure control valve 17 is a pressure regulating valve for controlling the B1 brake pressure P _B1 , as shown in FIG.
Spool 1 urged left by spring 17a
7b, and the signal pressure P _s1 is input from the first solenoid valve 22 to the left end port 17c. Port 17d is a drain port. Output port 17e is B
The input port 17f is connected to a port 16i of a fail-safe valve 16 described later. Further, the output pressure P _B1 is fed back to the right end port 17h. Therefore, the output pressure P _B1 becomes the signal pressure P
_The pressure is adjusted to the oil pressure proportional to _s1 . The B1 brake is not only engaged at the second speed and the fourth speed, but is also slip-controlled when the vehicle tries to reverse on an uphill road during neutral control described later. That is, the first solenoid valve 22 is controlled in accordance with the reverse speed, and the signal pressure P _s1 is input to the left end port 17c of the B1 pressure control valve 17. Therefore, the hydraulic pressure P _{B1 of the} B1 brake is feedback-controlled so that the vehicle does not exceed the limit reverse speed.

The fail-safe valve 16 is a valve for preventing multiple engagement (interlock) in which the C2 and C3 clutches and the B1 brake are simultaneously engaged during traveling in the D range. Specifically, the solenoid valve 22
3 engaging elements C2, C3, B due to malfunctions of ~ 25, failure of electronic control circuit, sticks of various valves, etc.
When the hydraulic pressure is simultaneously supplied to the first gear, the third gear state is forcibly set by releasing the hydraulic pressure P _{B1 of the} B1 brake. The fail-safe valve 16 includes a spool 16b urged rightward by a spring 16a as shown in FIG. 5, and the spool 16b is normally in the right position as shown in the upper part of the drawing, Only at the time of switching transition and at the time of interlock, it switches to the left side as shown in the lower part of the drawing. The right end port 16c has a C3 clutch pressure _Pc3 or R
Range pressure P _R is selectively input, the port 16d C
The two-clutch pressure P _C2 is input, the B1 brake pressure P _B1 is input to the port 16e, and the spool 16b is pushed leftward by these oil pressures. The left end of the port 16j accommodating the spring 16a the line pressure P _D at the time of forward movement is constantly input, the line pressure P _D at the time of even advanced port 16h is input through the sequencing valve 15. for that reason,
These oil pressures push the spool 16b rightward.
The port 16i is an input port 17 of the B1 pressure control valve 17.
f. Port 161 is a drain port. The fail-safe valve 16 has a reverse hydraulic pressure, ie, C, as shown in FIG.
A port 16f to which one clutch pressure _PC1 is input, a port 16g connected to the drain port 21d of the B2 pressure control valve 21, a drain port 16k, and the like are provided.

The sequence valve 15 has a function of ensuring the first speed when the operation of the second solenoid valve 23 or the C2 pressure control valve 18 is defective. Further, since the third solenoid valve 24 is also used for controlling the C3 clutch and the B2 brake, the B2 pressure control valve 21 and the C3 pressure control valve 2 are used.
Function of switching the source pressure of 0, function of guiding the R range pressure P _R to the right port 16c of the fail-safe valve 16 at the time of transition for change to the reverse range, B2 source pressure of the B1 brake pressure and the C3 clutch pressure when the action of the brake pressure And the like. As shown in FIG. 6, the valve 15 includes a spool 15b urged leftward by a spring 15a, and is controlled by a signal pressure P _S4 of a fourth solenoid valve 25 input to a signal port 15c at the left end. It switches to the direction. That is, the spool 15b is switched to the right only at the first speed of the L range and at the time of transition to the R range as shown in the lower part of the drawing. The port 15d receives the C2 clutch pressure P from the C2 pressure control valve 18.
_C2 is input, and port 15e is connected to the C2 clutch. Line pressure P _D at the time of forward movement from the manual valve 12 is input to the port 15f. Port 15g is connected to port 16h of fail-safe valve 16,
And it outputs the line pressure P _D at the time of forward. Port 15h is a drain port. The B2 brake pressure P _B2 is input from the B2 pressure control valve 21 to the port 15i,
5j is connected to the B2 brake. The port 15k line pressure P _R at the time of retraction are input is also connected to it C1 clutch. The port 151 is connected to the right end port 16c of the fail-safe valve 16, and the port 1
5m is connected to the C3 clutch.

The B2 pressure control valve 21 is a pressure regulating valve for controlling the B2 brake pressure P _B2 and has a spool 21b urged leftward by a spring 21a.
From the third solenoid valve 24 to the left end port 21c,
When the signal pressure P _S3 is input at the time of the range, the port 21 d
Is connected to the port 16g of the fail-safe valve 16. The port 21e is connected to the B2 brake via the sequence valve 15, and has a role of supplying the oil pressure P _B2 to the B2 brake at the time of the first shift of the L range and at the time of transition to the R range. The line pressure P _L is input to the port 21f, and the output pressure P _B2 is fed back to the right end port 21g containing the spring 21a.

During forward running, the port 21d is drained because it is connected to the C1 clutch via the fail-safe valve 16. Also, the left end port 21c
Since the signal pressure P _S3 of the third solenoid valve 24 which is input is also drained, the spool 21b is in the left end position as shown in the lower part of FIG. Therefore, the hydraulic pressure P _B2 to the B2 brake is also drained.

On the other hand, at the time of transition from the P and N ranges to the R range, the fourth solenoid valve 25 is temporarily turned on.
Therefore, the sequence valve 15 is temporarily switched to the right side, and the right end port 16
By high receding pressure P _R to c is input, the fail-safe valve 16 also temporarily switched to the left side, the port 21d of the B2 pressure control valve 21 is drained. Also,
Since the signal pressure P _S3 is input from the third solenoid valve 24 to the left end port 21c, the spool 21b is held at the position shown in the upper part of FIG. 6, and the output pressure P _B2 is proportional to the signal pressure P _S3 and the line pressure. The pressure is adjusted to a hydraulic pressure lower than P _L.
As described above, the B2 pressure control valve 21 has a function of gradually increasing the hydraulic pressure P _B2 to the B2 brake during the transition to the R range, that is, reducing the switching shock by delaying the engagement from the C1 clutch. are doing.

The C2 pressure control valve 18 has a C2 clutch pressure P
_This is a valve for controlling _C2 . The spool 18 is biased leftward by a spring 18a as shown in FIG.
b. The line pressure P _D during forward movement is input to the input port 18c, and the C2 clutch pressure P _C2 is output from the output port 18d. Line pressure P _D at the time of the signal pressure P _s2 or advancement of the second solenoid valve 23 via the C2 lock valve 19 at the left port 18e is input. In addition,
18f is a drain port. Output pressure P _C2 is fed back to the right end port 18g spring 18a is accommodated, the output pressure P _C2 is pressure is adjusted to a hydraulic proportional to the signal pressure P _s2.

The C2 lock valve 19 supplies the signal pressure _Ps2 of the second solenoid valve 23 to the left end port 18e of the C2 pressure control valve 18 at the time of starting transition, and the maximum pressure during traveling (first to third speeds). a valve for switching to supply the hydraulic pressure P _D. The lock valve 19 has a spool 19b urged rightward by a spring 19a as shown in FIG. 7, and is pushed leftward by a solenoid modulator pressure Psm input to a signal port 19c at the right end. The input port 19d has a line pressure P _D during forward movement.
Is input, and the output port 19e is connected to the C2 pressure control valve 18.
Is connected to the left end port 18e. Then, the left two ports 19f, the 19g is input the signal pressure P _s2 of the second solenoid valve 23. Starting at the beginning, since the signal pressure P _s2 of the second solenoid valve 23 is lower than the solenoid modulator pressure Psm, the spool 19b is in the left position, the port 19 g, signal at the left end port 18e of the C2 pressure control valve 18 via 19e By supplying the pressure P _s2 , the C2 clutch is controlled to slip, and the vehicle starts gently. on the other hand,
After the transition to complete to the running state of the start, since the P _s2 = Psm, spool 19b is switched to the right position by a spring 19a, the line pressure P _D during forward is supplied to the left port 18e of the C2 pressure control valve 18 To securely engage the C2 clutch. Further, in the fourth speed state, the signal pressure _Ps2 of the second solenoid valve 23 is drained, so that the spool 19b is in the left position and the port 19
The left end port 18e of the C2 pressure control valve 18 is drained via g and 19e, and the C2 clutch is released. The C2 clutch is not only engaged in the first to third speeds, but also in the neutral control described later, the signal pressure P _s2 of the second solenoid valve 23 is applied to the left end port 18 e of the C2 control valve 18 via the C2 lock valve 19. Supplied to
The C2 clutch is maintained in a substantially released state, in other words, a state immediately before engagement.

The C3 pressure control valve 20 is a valve for controlling the C3 clutch pressure _PC3 , and as shown in FIG. 7, a spool 20b urged leftward by a spring 20a.
It has. The left end port 20c is connected to the third solenoid valve 24, and receives a signal pressure _Ps3 thereof. Therefore, at the first and second speeds, the spool 20b is at the lower position in FIG. 7, and at the third and fourth speeds, the spool 20b is at the upper position in FIG. Port 20d is a drain port, port 2
0e is the output port connected to the C3 clutch, and the port 20f line pressure P _D at the time of forward movement is input. The output pressure _PC3 is fed back to the right end port 20g in which the spring 20a is disposed.

Next, an example of the neutral control according to the present invention will be described with reference to FIG. When started, it is first determined whether or not a start condition for starting the neutral control is satisfied (step S1). The start conditions include, for example, that the shift position is in the D range, the vehicle speed is almost 0, the throttle opening is almost fully closed, the brake signal is ON (the foot-operated brake is operating), The oil temperature may be equal to or higher than a predetermined temperature, and it is necessary to satisfy all these conditions.
If the start condition is satisfied, neutral control is started (step S2). In the neutral control, as described above, the signal pressure P _s2 of the second solenoid valve 23 becomes C2
It is supplied to the left end port 18e of the C2 control valve 18 via the lock valve 19, and the C2 clutch is almost released.
In other words, the state just before the engagement is maintained. Therefore, the input shaft 2 and the output shaft 7 of the transmission mechanism are in a power cutoff state,
It is possible to eliminate the creep force caused by the slippage of the fluid in the torque converter 1, reduce the engine load, reduce the power loss, and improve the fuel efficiency. Next, it is determined whether the vehicle has retreated during the neutral control (step S3). At this time, did you retreat on the uphill road,
Alternatively, in order to determine whether the vehicle has retreated for another reason, a gradient sensor or the like may be provided to detect the gradient of the road surface, but it is not always necessary to detect the gradient. If the vehicle is moving backward, it is determined whether or not the vehicle speed has become equal to or higher than the limit reverse speed (step S4). Here, the limit reverse speed is set to a constant value (for example, about 5 km / h) regardless of the gradient of the road surface. If the vehicle speed is lower than the limit reverse speed, the B1 brake pressure is maintained at 0, that is, the B1 brake is maintained in the released state (step S5). That is, since the reverse speed is low, it is determined that there is not much difference from the reverse on the uphill road in the state where the creep force is applied in the normal D range (first forward speed), and the brake control is not performed. On the other hand, when the vehicle speed is equal to or higher than the limit reverse speed, the vehicle speed is far from the reverse speed on the uphill road in a state where the creep force is applied in the normal D range (first forward speed). The B1 brake pressure is feedback-controlled so as to be the reverse speed (step S6). That is, by performing the slip control of the B1 brake, the reverse speed is controlled so as not to exceed the limit reverse speed. By performing the brake control as described above, even when the neutral control is performed, the same reverse feeling as in the normal D range (during the non-neutral control) can be obtained, and the driver does not feel uncomfortable. I'm done.

As described above, in the neutral control according to the present invention, it is determined whether or not to start the control based on the oil temperature in addition to the vehicle speed, the brake signal, and the throttle opening.
The reason for the need for the oil temperature condition is that the neutral control requires the clutch to be controlled to a state just before engagement, but at low temperatures the viscosity of the oil increases, making it difficult to perform delicate clutch control. It is. Therefore, when the temperature is low, the neutral control is not performed.

In the above description, the limit retreat speed is set to a constant value, but the present invention is not limited to this. FIG. 9 shows another example of setting the limit retreat speed. In this case, the retreat speed on the uphill road in the neutral control is made to substantially match the retreat speed on the uphill road in the state where the creep force is applied in the normal D range (first forward speed). Is set high according to the gradient of the road surface. Therefore, when the vehicle retreats during the neutral control, the retreat speed is limited according to the gradient of the road surface, so that driving can be performed with the same feeling as in a normal D range. That is, the driver can drive without being aware of the neutral control. However, in this case, since it is necessary to know the gradient of the road surface, it is necessary to use a gradient sensor. In FIG. 9, the limit retreat speed is set in proportion to the gradient, but may be set stepwise as shown by a broken line.

FIG. 9 shows a case where the limit retreat speed-gradient characteristic is constant. However, the limit retreat speed-gradient characteristic may be changed in consideration of various conditions, or the limit retreat speed may be obtained by calculation. . That is, the reverse speed on the uphill road in the D range changes not only due to the slope of the road surface but also due to an increase in creep force accompanying an increase in the idle speed due to the operation of the air conditioner and the like, and also changes depending on the number of occupants and the like. . If the limit reverse speed-gradient characteristic is constant as shown in FIG. 9, there may be a difference in the reverse speed between the normal D range and the neutral control. Therefore, the limit retreat speed may be calculated from the results of the road surface gradient, the idling speed, the acceleration characteristics in the D range, and the like. As a result, the reverse speed on the uphill road during the neutral control can be made to exactly match the reverse speed in the D range state.

In the above embodiment, the three clutches C1 to C
3 and 2 brakes B1, B2 and one-way clutch F
However, the present invention is not limited thereto, and an automatic transmission including at least a clutch engaged at the first forward speed, a one-way clutch, and a brake engaged at the second speed. If applicable, it is applicable.
Although the hydraulic control valves of the B1 brake and the C2 clutch are constituted by the combination of the spool valves 17 and 18 and the solenoid valves 22 and 23, they may be constituted by a single solenoid valve. As the solenoid valve, a known solenoid valve such as a duty solenoid valve or a linear solenoid valve can be used.

[0034]

As is apparent from the above description, according to the present invention, when the vehicle starts to reverse on an uphill road during the neutral control, the brake control is performed so as to limit the reverse speed to the limit reverse speed or less. Thus, the same reverse feeling as in the normal D range can be obtained, and the driver does not feel uncomfortable. Also, when you want to slowly retreat on an uphill road,
Since the vehicle can be slowly moved backward only by depressing the brake pedal, no special operation is required. Furthermore, according to the present invention, the brake is not completely engaged, and it is possible to slide even when the brake is fully engaged, so that there is an effect that no engagement shock due to the engagement of the brake is generated.

[Brief description of the drawings]

FIG. 1 is a schematic mechanism diagram of an example of an automatic transmission for a vehicle according to the present invention.

FIG. 2 is an operation table of each engagement element and a solenoid valve of the automatic transmission of FIG. 1;

FIG. 3 is an overall circuit diagram of a hydraulic control device of the automatic transmission shown in FIG.

FIG. 4 is a circuit diagram of a regulator valve, a manual valve, and a solenoid modulator valve in the hydraulic control device of FIG. 3;

FIG. 5 is a circuit diagram of a B1 pressure control valve and a fail-safe valve in the hydraulic control device of FIG.

6 is a circuit diagram of a fail-safe valve, a sequence valve, and a B2 pressure control valve in the hydraulic control device of FIG.

FIG. 7 is a circuit diagram of a C2 pressure control valve, a C2 lock valve, and a C3 pressure control valve in the hydraulic control device of FIG. 3;

FIG. 8 is a flowchart illustrating a method of neutral control and brake control according to the present invention.

FIG. 9 is a diagram illustrating a characteristic example of a limit retreat speed and a gradient.

[Explanation of symbols]

 C2 clutch B1 brake 17 B1 pressure control valve 18 C2 pressure control valve 22, 23 solenoid valve 30 Electronic control unit

Claims (2)

[Claims] A fluid transmission device for transmitting an engine driving force to a transmission mechanism, a clutch engaged when a forward travel range is selected, and locking by engagement of the clutch to achieve a first forward speed. A one-way clutch and a brake that locks the one-way clutch by engagement and prevents reverse rotation of the output shaft of the transmission mechanism. When the vehicle is stopped and a predetermined condition is satisfied, the clutch is almost released and neutral control is performed. Automatic transmission that performs
A control device for an automatic transmission, further comprising means for controlling the hydraulic pressure applied to the brake so that when the vehicle reverses during the neutral control, the braking hydraulic pressure is lower than the limit reverse speed. 2. The control device for an automatic transmission according to claim 1, wherein the limit reverse speed is made substantially equal to the reverse speed on an uphill road in a state where a creep force is applied in a first forward speed. .