JPH05322018A - Shift control unit for automatic transmission - Google Patents

Abstract

PURPOSE:To lessen shift shock at downshifting without reducing running perfor mance at downshifting under power on. CONSTITUTION:After a second gear is synchronized (S9 is YES) with a gear downshifted 3 2, a brake of a high speed stage side is released and if shift speed DELTAtheta of a throttle valve opening theta is DELTAtheta or more, back pressure Pa of an accumulator for controlling engagement oil pressure of the brake is set to rather small value, Pa1 (S13) and if change rate DELTAtheta is DELTAthetaa or less, the back pressure Pa is set to Pa2 which is larger than Pa1 (S14).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for an automatic transmission, and more particularly to releasing a friction engagement device on a high speed stage side and engaging a friction engagement device on a low speed stage side to downshift. The present invention relates to shift control when performing.

[0002]

2. Description of the Related Art Automatic vehicles equipped with an automatic transmission in which a plurality of gears are established by selectively engaging a plurality of friction engagement devices are widely used.
For example, FIG. 2 shows three clutches C0 as a friction engagement device.
-C2 and an example of an automatic transmission with five brakes B0-B4, the clutches and brakes of which are shown in FIG.
As shown by the "○" mark in FIG.
A high speed gear stage is established. In such an automatic transmission, when downshifting from 3rd to 2nd, for example, the brake B2 on the 3rd side is released and the brake B3 on the 2nd side is engaged, but the engine is blown up or both brakes are excessive. To prevent tie-ups,
The engagement torque of the brake B2 is gradually decreased while gradually increasing the engagement torque of the brake B2, and the engagement torque of the brake B2 is rapidly reduced after the brake B3 is engaged to complete the shift. The reason why the engaging torque of the brake B2 is rapidly reduced is to accelerate the rising of the driving torque, and the driving force lowering time at the time of gear shifting accompanying the engagement switching of the brakes B2 and B3 is shortened. The device described in Japanese Patent Application No. 3-344123 filed earlier by the present applicant is an example of a shift control device that performs such downshift control.

[0003]

However, in such a conventional shift control device, the driver may feel a shift shock depending on the driving situation because the driving torque rapidly rises. That is, in the downshift at the time of power-on when the driver depresses the accelerator pedal, the above-mentioned quick rise of the drive torque matches the driver's intention, which is desirable in terms of driving performance and causes a shift shock. However, in a downshift that occurs when the vehicle speed decreases on an uphill road in a state where the driver does not want to increase the driving force so much and there is little change in the accelerator, a gear shift shock occurs because the gear is suddenly changed. It is difficult to say that it is easy to feel and that an excellent riding comfort is not always obtained.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to reduce shift shock during downshifting without impairing running performance during downshifting during power-on. ..

[0005]

In order to achieve such an object, it is sufficient to control the rising of the driving torque according to the degree of demand of the driver for increasing the driving force. As shown in the claim correspondence diagram, it has an automatic transmission that establishes a plurality of shift speeds by selectively engaging a plurality of friction engagement devices, and when a downshift from a high speed gear to a low speed gear A gear shift control device for completely releasing the engagement of a friction engagement device on a high speed stage after engaging a friction engagement device on a gear stage, (a) accelerator operation amount detection means for detecting an accelerator operation amount, (B) a driving force request judging means for judging the degree of demand for an increase in the driving force of the driver based on the accelerator operation amount detected by the accelerator operation amount detecting means; and (c) the driving force request judging means. When the determined demand for the increase in the driving force is high, the engagement torque of the friction engagement device on the high speed stage side is quickly reduced after the friction engagement device on the low speed stage side is completely engaged. If the demand for increasing the driving force is low, the engagement torque control for gently reducing the engagement torque of the friction engagement device on the high speed stage side after the friction engagement device on the low speed stage side is completely engaged. And means.

[0006]

In such a shift control device for an automatic transmission, the driving force request judging means judges the degree of demand for increasing the driving force of the driver based on the accelerator operation amount detected by the accelerator operation amount detecting means. When the degree of demand for increasing the driving force is high, the engagement torque of the high speed gear side friction engagement device is promptly reduced after the low speed gear side friction engagement device is completely engaged by the engagement torque control means. On the other hand, when the degree of demand for increasing the driving force is low, the engagement torque of the friction engagement device on the high speed stage side becomes gentle after the friction engagement device on the low speed stage side is completely engaged by the engagement torque control means. Be lowered. Due to this difference in the decreasing speed of the engaging torque, when the demand for increasing the driving force is high, that is, when the driver shifts down the power on to depress the accelerator, the driving torque rises quickly and excellent running performance is obtained. However, in a downshift in which the degree of demand for increasing the driving force is low, the rise of the driving torque is gentle and the shift shock is reduced. When the degree of demand for increasing the driving force is low, the driver does not desire such high running performance, so that even if the rise of the driving torque is delayed a little, there is no problem.

[0007]

As described above, according to the shift control device of the present invention, the driving torque rapidly rises in the downshift at the time of power-on when the driver desires to increase the driving force, and excellent running performance is obtained. In a downshift in which the degree of demand for increasing the driving force is low, the drive torque rises gently and shift shock is reduced, so that both running performance and riding comfort can be achieved depending on the driving state.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 2, the automatic transmission 10 includes a torque converter 12, a first transmission 14, and a second transmission 1.
6 is provided. The pump impeller of the torque converter 12 is connected to the crankshaft 20 of the engine 18, and the turbine impeller of the torque converter 12 is connected via the input shaft 22 to the first transmission 1
4 carriers 24. First transmission 14
Is the sun gear 26, the ring gear 28, and the carrier 2.
4 is rotatably arranged in the sun gear 26, the ring gear 2
8 and a planetary gear device including a planetary gear 30 that is meshed with the gear 8. The clutch C0 and the one-way clutch F0 are provided in parallel between the sun gear 26 and the carrier 24, and the sun gear 26 and the housing 3 are provided.
A brake B0 is provided between the two.

The second transmission 16 includes a sun gear 34, a ring gear 36, and a planetary gear 40 rotatably arranged on the carrier 38 and meshed with the sun gear 34 and the ring gear 36. The sun gear 42, A second planetary gear unit comprising a ring gear 44 and a planetary gear 48 rotatably arranged on the carrier 46 and meshed with the sun gear 42, the ring gear 44, and rotatably arranged on the sun gear 50, the ring gear 52, and the carrier 54. And a third planetary gear unit including a planetary gear 56 meshed with the sun gear 50 and the ring gear 52. The sun gears 34 and 42 and the ring gear 2 of the first transmission 14 are included.
8, a clutch C2 is provided between the sun gears 34 and 42 and the housing 32, and a brake B1 is provided.
One-way clutch F1 and brake B arranged in series
2 and 2 are provided in parallel, and the carrier 38 and the housing 32 are provided.
A brake B3 is provided between the ring gear 44 and the sun gear 50 and the ring gear 28 of the first transmission 14, and a clutch C1 is provided between the ring gear 52 and the housing 32. Directional clutch F2 is provided in parallel. Also, the ring gear 3
6, the carriers 46 and 54 are integrally connected to the output shaft 58, and the output shaft 58 is connected to the drive wheels via a differential gear device or the like.

The clutches C0 to C2 and the brake B
0 to B4 (hereinafter, unless otherwise specified, the clutch C,
The brake B) is a hydraulic friction engagement device that is frictionally engaged by a hydraulic actuator such as a multi-plate clutch or band brake, and hydraulic oil is supplied from the hydraulic control circuit 60 to the hydraulic actuator. Is becoming The hydraulic control circuit 60 is equipped with a large number of switching valves and the like, and three ON / OFF solenoid valves 64, 66, according to the excitation signal from the control unit 62.
And 68 are respectively switched, the hydraulic circuit is switched, and the clutch C and the brake B are switched.
Is selectively engaged and controlled, and as shown in FIG. 4, one of the five forward speeds is established. FIG. 4 shows the case where the shift lever is operated to the “D (drive)” range. In the figure, “◯” indicates engagement control, and “Δ” indicates engagement during engine braking. Means total control. Further, the gear ratio of each shift stage (the rotation speed Nin of the input shaft 22 / the rotation speed Nout of the output shaft 58) is 1st.
Is the largest, 2nd, 3rd, 4th, O / D becomes smaller, and the 4th gear ratio is 1.0.
Although illustration is omitted, when the shift lever is operated to the “R (reverse)” range, the manual shift valve of the hydraulic control circuit 60 is switched to establish the reverse gear.

FIG. 3 is a diagram showing a part of the hydraulic pressure control circuit 60. The engaging hydraulic pressures PB2 and PB3 of the brakes B2 and B3 are shown in FIG.
The line oil pressure PL adjusted according to the vehicle speed and the throttle valve opening is controlled by the B2 supply / exhaust oil passage 74 or the B3 supply via the 1-2 shift valve 70 and the 2-3 shift valve 72. Guided to the oil drainage path 76. 1-2 shift valve 70
Can be switched between a first position for guiding the line oil pressure PL to the oil passage 78 and a second position for connecting the oil passage 78 to the drain oil passage 80. The ON / OFF solenoid valves 64, 66, When the 2nd or 3rd speed is established by 68, the first position is set according to the signal hydraulic pressure, and when the 1st speed is established, the second position is set according to the signal hydraulic pressure. Also, 2-3
The shift valve 72 connects the oil passage 78 to the B3 supply / discharge oil passage 76, and connects the B2 supply / discharge oil passage 74 to the drain oil passage 80, and connects the oil passage 78 to the B2 supply / discharge oil passage 74. At the same time, the B3 supply / discharge oil passage 76 can be switched to the second position where it is connected to the drain oil passage 80.
When the st or 2nd speed is established, the first position is set in accordance with the signal hydraulic pressure, and when the 3rd speed is established, the first position is set in the second position. Therefore, at the second shift speed, as shown in the figure, the line oil pressure PL is guided to the B3 hydraulic actuator 82 that engages the brake B3 via the B3 supply / discharge oil passage 76, and the B2 supply / discharge oil passage 74 is connected. Drain oilway 8
On the other hand, the line hydraulic pressure P
L is guided to the B2 hydraulic actuator 84 that engages the brake B2 via the B2 supply / discharge oil passage 74, and
The third oil supply / drain passage 76 is connected to the drain oil passage 80.

An engaging oil pressure PB is provided in the B3 supply / discharge oil passage 76.
A PB3 control valve 86 that regulates pressure 3 is arranged in parallel with an orifice and a check valve that are provided in parallel with each other. This PB3 control valve 86 is B
The spool valve 94 is provided for switching the communication states of the communication ports 88, 90 and the drain communication port 92 connected to the third oil supply / drain passage 76, and the spool valve is supplied by the signal hydraulic pressure PSb supplied from the SLU linear solenoid valve 96. By continuously changing the position of the child 94, the communication state between the communication ports 88 and 90 is continuously changed, and the communication state between the communication port 90 and the drain communication port 92 is continuously changed. The SLU linear solenoid valve 96 is configured to continuously change the magnitude of the signal hydraulic pressure PSb by duty-controlling the excitation signal SB supplied from the control unit 62. The drain communication port 92 is connected to the B2 orifice control valve 100 via an oil passage 98. In addition, the PB3 control valve 86 has 3r
The third speed signal hydraulic pressure PS3 is supplied at the d-th gear, so that the communication ports 88 and 90 are completely communicated with each other and the communication between the communication port 90 and the drain communication port 92 is completely cut off. To be done.

The B2 orifice control valve 100
Are arranged in the B2 supply / drain passage 74 in parallel with the orifices and the check valves provided in parallel with each other, and the pair of communication ports 10 connected to the B2 supply / drain passage 74 are connected to each other.
Spool valve 106 for switching the communication state of 2, 104
Is equipped with. When the signal hydraulic pressure PSc is supplied from the ON / OFF solenoid valve 108 to the spool valve element 106,
It is moved to the moving end on the left side against the hydraulic pressure in the B2 oil supply / exhaust passage 74, and connects the communication ports 102 and 104.
The ON / OFF solenoid valve 108 turns ON / OFF the excitation signal SC supplied from the control unit 62.
The output state of the signal hydraulic pressure PSc is switched by F. Such B2 orifice control valve 1
00 is also a communication port 11 to which the oil passage 98 is connected.
0 and a drain port 112, and the spool valve element 106 is moved to the left side moving end so that the connecting port 110 and the drain port 112 thereof are provided.
The communication with the communication port 11 is stopped by blocking the communication with the spool valve 106 and moving it to the right moving end.
0 and the drain port 112 are communicated with each other.

A B2 accumulator 114 and a B3 accumulator 116 are connected to the B2 supply / discharge oil passage 74 and the B3 supply / discharge oil passage 76, respectively, near the hydraulic actuators 84, 82 via orifices. In these accumulators 114 and 116, the back pressure Pa is controlled by the accumulator back pressure control valve 118, so that the engaging hydraulic pressures PB2 and PB during the supply / discharge transient of the hydraulic oil.
3 is pressure controlled. The accumulator back pressure control valve 11
8 continuously changes the back pressure Pa according to the signal oil pressure PSa supplied from the SLN linear solenoid valve 120. The SLN linear solenoid valve 120 is duty-controlled for the excitation signal SA supplied from the control unit 62. By doing so, the magnitude of the signal hydraulic pressure PSa is continuously changed. Note that FIG.
122 is a 2-3 timing valve that regulates the engagement hydraulic pressure PB2 according to the signal hydraulic pressure PSb when shifting from 2nd to 3rd.

Returning to FIG. 2, the automatic transmission 10 is provided with a pair of rotation speed sensors 130 and 132. The rotation speed sensor 130 indicates the rotation speed Nin of the input shaft 22.
The rotation speed sensor 132 detects the
Rotation speed Nout of each of the rotation speed signals SNin and SN, respectively.
Output out to the control unit 62. The control unit 62 is also supplied with a throttle valve opening signal Sθ representing a throttle valve opening θ from a throttle position sensor 134 arranged in the throttle valve of the engine 18, and is also arranged in the distributor of the engine 18. An engine rotation speed signal SNE representing the engine rotation speed NE is supplied from the rotation angle sensor 136. The throttle valve is mechanically connected to an accelerator pedal to open and close,
The throttle valve opening θ substantially corresponds to the accelerator operation amount. In this embodiment, the throttle position sensor 134
Corresponds to the accelerator operation amount detection means.

The control unit 62 is a CP
U, RAM, ROM, an input / output interface circuit, etc. are used to perform signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM, and each solenoid valve of the hydraulic control circuit 60. By outputting an excitation signal to, the gear position of the automatic transmission 10 is switched according to a predetermined gear shift diagram, and
The engagement hydraulic pressure of the clutch C and the brake B at the time of gear shift is adjusted. The above-mentioned shift diagram is set for each type of shift with the vehicle speed represented by the throttle valve opening θ and the output shaft rotation speed Nout as parameters, and the smaller the throttle valve opening θ and the higher the vehicle speed, the upshift to the higher gear side. In addition, as the throttle valve opening θ increases and the vehicle speed decreases, the downshift is made to the lower speed side. In addition to the above signals, the control unit 62 includes a shift range position and ON / O of an overdrive switch.
A signal representing an FF or the like is supplied and used for the above-described shift control and the like. As for the lockup clutch of the torque converter 12, the solenoid valve (not shown) provided in the hydraulic control circuit 60 is duty-controlled to switch between the complete engagement, the slip state, and the release state.

Here, the automatic transmission 10 of the present embodiment will be described.
In (1), it is necessary to release the brake B2 and engage the brake B3 when downshifting from 3rd to 2nd in a normal traveling state in which the engine brake is not applied. Hereinafter, the 3 → 2 shift will be specifically described with reference to the flowchart of FIG. In addition,
In such a 3 → 2 shift, the clutch C0 is released, but due to the action of the one-way clutch F0, the clutch C0 is released after the shift is completed.
The release timing of the clutch C0 does not pose a problem, such as releasing the clutch C0. Therefore, the description of the release control of the clutch C0 will be omitted in the following description.

First, in step S1, the excitation states of the three ON / OFF solenoid valves 64, 66, 68 are switched so as to shift from the 3rd gear to the 2nd gear.
As a result, the 2-3 shift valve 72 is switched from the second position to the first position, and the line hydraulic pressure PL passes through the 1-2 shift valve 70, the 2-3 shift valve 72, the B3 supply / discharge oil passage 76, and the B3 hydraulic pressure. While being guided into the actuator 82, the B2 supply / discharge oil passage 74 is connected to the drain oil passage 80 and the hydraulic oil in the B2 hydraulic actuator 84 starts to be drained. In step S2, the engagement oil pressure PB2 is lowered by the drain of the hydraulic oil in the B2 hydraulic actuator 84, and the change rate ΔNin of the input shaft rotation speed Nin that changes when the brake B2 starts to slip is a predetermined target change. The engagement hydraulic pressure PB2 is adjusted so that the ratio ΔNa is obtained. The pressure regulation control of the engagement hydraulic pressure PB2 is performed by the B2 accumulator 1
The back pressure Pa of 14 is controlled by the accumulator back pressure control valve 118. Specifically, the duty ratio of the exciting current SA to be output to the SLN linear solenoid valve 120 is determined by the change rate ΔNin and the target change rate ΔNa. Feedback control is performed according to the deviation. The target change rate ΔN
“A” is calculated from a predetermined data map, a calculation formula, or the like using the vehicle speed and the like as parameters. This back pressure Pa
The feedback control is continued until the determination in step S9 becomes YES, and times t1 to t4 in the time chart of FIG. 6 are times during which the back pressure control is being performed.

In the next step S3, the flag F1 is "0".
It is determined whether or not it is "0" and immediately step S8.
The following is executed, but since the flag F1 is set to "1" in step S7, steps S4 and thereafter are executed until then. In step S4, the PB3 control valve 86
Thus, the engagement hydraulic pressure PB3 is controlled to a predetermined low pressure state such that the brake B3 slightly transmits the torque. That is, the PB3 control valve 86 controls the B3 supply / discharge oil passage 7
When the oil pressure in 6 is low, the spool valve element 94 is positioned at the leftward moving end in FIG. 3 in accordance with the urging force of the spring and the signal oil pressure PSb to connect the communication ports 88 and 90 and to connect the communication port 90 and the drain. In order to block the communication with the port 92, when the 2-3 shift valve 72 is switched to the first position, the hydraulic oil is rapidly supplied into the B3 hydraulic actuator 82 through the communication ports 88 and 90. However, when hydraulic fluid is filled in the B3 hydraulic actuator 82 until the friction materials of the brake B3 come into contact with each other, the hydraulic pressure in the B3 supply / discharge oil passage 76 rises, and the spool valve element 94 is moved to the right. The communication port 90 and the drain communication port 92 are communicated with each other so that the hydraulic oil is drained, and the hydraulic pressure in the B3 supply / discharge oil passage 76, that is, the engagement hydraulic pressure PB3 is adjusted to a hydraulic pressure that balances with the signal hydraulic pressure PSb. To be done. Therefore, the engagement hydraulic pressure PB3 is regulated according to the magnitude of the signal hydraulic pressure PSb, in other words, the duty ratio of the exciting current SB output to the SLU linear solenoid valve 96.

The duty ratio of the exciting current SB is a predetermined data map or an arithmetic expression using the input torque as a parameter so that the engagement hydraulic pressure PB3 is in a low pressure state that causes a slight torque transmission to the brake B3. Etc. The input torque is, for example, the engine speed N
The engine output torque is calculated from a predetermined output torque characteristic of the engine 18 based on E and the throttle valve opening degree θ, and based on the speed ratio between the engine rotation speed NE and the input shaft rotation speed Nin and the engine output torque. The torque of the input shaft 22 can be directly detected by using a torque sensor or the like, although the torque ratio characteristic of the torque converter 12 is determined in advance. By thus controlling the engagement hydraulic pressure PB3 to a low pressure, tie-up in which both the brakes B2 and B3 are engaged with an excessive engagement torque is avoided. The B2 orifice control valve 100 is held in a state in which the communication port 110 and the drain port 112 communicate with each other based on the hydraulic pressure in the B2 supply / discharge oil passage 74. The hydraulic oil is rapidly supplied into the B3 hydraulic actuator 82 until time t2 in FIG. 6, and the engagement hydraulic pressure PB is reached after time t2 (until t3).
3 is in a state of being held at a low pressure.

In the following step S5, the input shaft rotation speed N
The estimated synchronization time tm until in synchronizes with the output shaft rotation speed Nout according to the gear ratio α2 of the 2nd speed is expressed by the following equation (1).
Then, in step S6, it is determined whether or not the expected synchronization time tm is shorter than a predetermined constant time ta. Then, while tm ≧ ta, the above step S2 and subsequent steps are repeated, but when tm <ta, the step S7 and subsequent steps are executed.

[0022]

## EQU1 ## tm = (α2 · Nout−Nin) / ΔNin (1)

In step S7, the flag F1 is set to "1", so that in subsequent cycles, step S8 and subsequent steps are executed following step S3. In step S8, the PB3 control valve 86 is controlled so that the engagement hydraulic pressure PB3 increases at a predetermined increase rate. That is, by changing the duty ratio of the exciting current SB output to the SLU linear solenoid valve 96 at a predetermined change rate, the signal oil pressure PSb is gradually increased to increase the engagement oil pressure PB3, and the engagement of the brake B3 is increased. The combined torque is gradually increased. The rate of change of the duty ratio of the exciting current SB is calculated from a predetermined data map or an arithmetic expression using the input torque as a parameter, and the input torque is the output torque characteristic of the engine 18 or the torque of the torque converter 12 as described above. It is calculated based on the ratio characteristics. At time t3 in FIG. 6, such an engagement hydraulic pressure PB
This is the time when the boost control of No. 3 is started.

In the following step S9, the input shaft rotation speed N
Whether or not in is synchronized with the output shaft rotation speed Nout according to the gear ratio α2 of the 2nd speed, that is, whether or not the brake B3 is completely engaged, satisfies the following expression (2). Whether or not it is determined, and until the synchronization is performed, step S2
The following executions are repeated, but after synchronization, step S10
Do the following: The determination of the equation (2) is performed with a predetermined width in consideration of the detection error of the sensor and the like. Time t in FIG.
4 is the time synchronized with the 2nd shift stage.

[0025]

[Formula 2] Nin≈α2 · Nout (2)

In step S10, the flag F1 is set to "0", and in the following step S11, the exciting current SB is switched so that the signal oil pressure PSb output from the SLU linear solenoid valve 96 is maximized, and the PB3 control valve 86 is switched.
The communication ports 88 and 90 are completely connected to each other, and the excitation signal SC is supplied to the ON / OFF solenoid valve 108.
Is output to generate the signal hydraulic pressure PSc, and the communication ports 102 and 104 of the B2 orifice control valve 100 are connected. By making the communication ports 88 and 90 of the PB3 control valve 86 completely connected,
The engagement hydraulic pressure PB3 is quickly raised to the brake B3.
The engagement torque of the B2 orifice control valve 100 is rapidly increased, while the communication ports 102 and 104 of the B2 orifice control valve 100 are increased.
By making the and the communication states, the hydraulic oil in the B2 hydraulic actuator 84 is rapidly drained.

In the next step S12, it is determined whether or not the changing speed Δθ of the throttle valve opening θ is equal to or more than a predetermined constant changing speed Δθa. Throttle valve opening θ
If the change speed Δθ of is large, it means that the driver is requesting an increase in the driving force when the accelerator pedal is depressed, and the 3 → 2 shift currently being executed is a downshift due to power-on. Means there is. Further, when the change speed Δθ is small, it means that the driver does not need to increase the driving force so much when the accelerator pedal depression operation amount hardly changes.
→ 2nd shift means downshift due to a decrease in vehicle speed due to an uphill road.

When Δθ ≧ Δθa, in other words, when the demand for increasing the driving force is high, in step S13, the SLN linear is adjusted so that the accumulator back pressure Pa becomes a predetermined relatively small hydraulic pressure Pa1. The duty ratio of the excitation signal SA output to the solenoid valve 120 is set. As a result, the engagement hydraulic pressure PB2 of the brake B2, that is, the engagement torque of the brake B2 is rapidly reduced, and the drive torque is rapidly increased in response to the reduction of the engagement torque of the brake B2. When the input torque is Tin and the engagement torque of the brake B2 is T _B2 , the driving torque To is proportional to (A · Tin−B · T _B2 ), and the driving torque To is corresponding to the decrease of the engagement torque T _B2. It will grow. Note that A and B are constants. When Δθ <Δθa, in other words, when the degree of demand for increasing the driving force is low, in step S14,
The duty ratio of the excitation signal SA output to the SLN linear solenoid valve 120 is set so that the accumulator back pressure Pa becomes a predetermined hydraulic pressure Pa2 higher than the hydraulic pressure Pa1. As a result, the engagement hydraulic pressure P of the brake B2
B2, that is, the engagement torque of the brake B2 is gently reduced, and the drive torque is gradually increased in response to the reduction of the engagement torque of the brake B2. The drive torque and the engagement hydraulic pressure P indicated by the one-dot chain line in FIG.
The graph of B2 is the case where the accumulator back pressure Pa is Pa1, and the graph of the drive torque and the engagement hydraulic pressure PB2 shown by the solid line in the figure is the case where the accumulator back pressure Pa is Pa2. The excitation signal S
The duty ratio of A is set in advance corresponding to the oil pressures Pa1 and Pa2. The accumulator back pressure Pa is also supplied to the accumulator 116 of the brake B3,
Only the deviation of the retreat timing of the piston of the accumulator 116 is generated, and the engagement control of the brake B3 is not affected.

As described above, the downshift control from the 3rd gear to the 2nd gear is completed, but in the present embodiment, in the downshift at power-on when the driver desires to increase the driving force, the brake B2 is synchronized after the 2nd synchronization. Is quickly released and the drive torque is quickly increased.
While excellent running performance that matches the driver's intention is obtained, in a downshift in a state where the accelerator change is small, the brake B2 is released gently and the drive torque is gradually increased, so the shift shock is reduced. Excellent riding comfort can be obtained. When the degree of demand for increasing the driving force is low, the driver does not desire such high running performance, and therefore it does not matter if the driving torque rises slowly.

In this embodiment, the control unit 62
The part that executes step S12 in the series of signal processing according to step S11 corresponds to the driving force request determination means, and step S13,
The part that executes S14 is the B2 accumulator 114,
The accumulator back pressure control valve 118 and the SLN linear solenoid valve 120 constitute an engagement torque control means.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above embodiment, B is synchronized after 2nd synchronization.
Although the back pressure Pa of the 2 accumulator 114 is switched in two steps to change the engagement torque reduction speed of the brake B2, three or more steps are required depending on the magnitude of the change speed Δθ of the throttle valve opening θ. The back pressure Pa may be changed continuously.

In the above embodiment, the back pressure Pa is controlled by the accumulator back pressure control valve 118 according to the signal oil pressure PSa output from the SLN linear solenoid valve 120.
The back pressure Pa can be directly controlled by the OFF solenoid valve.

Further, in the above embodiment, the accumulator 11
Although the back pressure Pa common to 4 and 116 is supplied, the back pressure of these accumulators 114 and 116 can be independently controlled.

Also, instead of changing the back pressure Pa, B2
It is also possible to control the engagement torque lowering speed of the brake B2 by changing the distribution area of the hydraulic fluid drained from the hydraulic actuator 84 by using an ON / OFF solenoid valve, a linear solenoid valve, or the like. That is, if the distribution area during draining is increased, the rate of decrease of the engaging torque becomes faster, and if the distribution area during draining is decreased, the rate of decrease of the engaging torque becomes slower.

Also, considering the delay time after the duty ratio of the excitation signal SA is changed until the accumulator back pressure Pa actually changes, the input shaft rotation speed Nin is completely 2n.
Before synchronizing in accordance with the gear ratio α2 of the d gear, for example, the input shaft rotation speed Nin is a predetermined rotation speed ΔN from α2 · Nout
However, the duty ratio of the excitation signal SA may be changed by executing step S12 and the subsequent steps when a predetermined time has passed after the determination in step S6 is YES.

Further, in the above embodiment, the case where the automatic transmission 10 of the fifth forward speed performs the 3 → 2 shift has been described, but at least the friction engagement device on the high speed stage side is released and the friction engagement on the low speed stage side is performed. The present invention can be similarly applied to an automatic transmission having a shift stage that engages a device to perform a downshift, and the number of shift stages and the configuration of the automatic transmission can be appropriately changed.

In the above embodiment, the engagement oil pressure PB3 of the brake B3 is maintained at a low pressure and then gradually increased to completely engage the brake B3, but at least the brake B2 slips. In this state, the brake B3 may be completely engaged, and then the brake B2 may be completely disengaged.

In the above embodiment, the throttle valve opening θ
Although the degree of demand for increasing the driving force was determined from the change speed Δθ of, the degree of demand for increasing the driving force can be determined, for example, by determining whether the throttle valve opening θ is larger than a predetermined judgment value. The method for determining is determined appropriately.

Further, although the throttle position sensor 134 is used as the accelerator operation amount detecting means in the above embodiment, it goes without saying that the operation amount of the accelerator pedal may be directly detected.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a diagram illustrating a configuration of an automatic transmission including a shift control device that is an embodiment of the present invention.

FIG. 3 is a circuit diagram showing a portion related to 3 → 2 shift in a hydraulic control circuit provided in the automatic transmission of FIG.

FIG. 4 is a diagram showing a shift stage of the automatic transmission of FIG. 2 and engagement operations of a clutch and a brake for establishing the shift stage.

FIG. 5 is a flowchart illustrating an operation when performing 3 → 2 shift in the automatic transmission of FIG.

6 is a time chart showing changes in input shaft rotation speed, drive torque, and hydraulic pressure when 3 → 2 shift is performed in the automatic transmission of FIG.

[Explanation of symbols]

10: Automatic transmission 62: Control unit 114: B2 accumulator 118: Accumulator back pressure control valve 120: SLN linear solenoid valve 134: Throttle position sensor (accelerator operation amount detecting means) B2: Brake (high speed side friction engagement device) B3: Brake (low speed gear side friction engagement device) Step S12: Driving force request determination means Steps S13 and S14: Engagement torque control means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Ando 10 Akane Takane, Fujii-cho, Aichi Prefecture Aisin AW Co., Ltd.

Claims (1)

[Claims] 1. An automatic transmission having a plurality of shift speeds established by selectively engaging a plurality of friction engagement devices, the low speed gear side being used when downshifting from a high speed gear to a low gear speed. In a shift control device for completely releasing the engagement of the friction engagement device on the high speed stage after engaging the friction engagement device, the accelerator operation amount detecting means for detecting an accelerator operation amount, and the accelerator operation amount. Based on the accelerator operation amount detected by the detection means, a driving force request judging means for judging a requesting degree for the driving force increase of the driver, and a requesting degree for the driving force increase judged by the driving force request judging means are When it is high, the engagement torque of the friction engagement device on the high speed side is quickly reduced after the friction engagement device on the low speed side is completely engaged, while the demand for increasing the driving force is low. In this case, there is provided an engagement torque control means for gently reducing the engagement torque of the friction engagement device on the high speed stage side after the friction engagement device on the low speed stage side is completely engaged. Shift control device for automatic transmission.