JPS63111351A - Method of controlling shift of vehicle automatic transmission - Google Patents

Abstract

PURPOSE:To reduce unsatisfactory shocks due to deceleration when a clutch is re-engaged, by selecting a gear for starting a vehicle among a plurality of gear stages in accordance with the acceleration of the vehicle when the vehicle descends in a coasting condition. CONSTITUTION:An accelerator sensor 42 provided to an accelerator pedal 40 is adapted to detect an accelerator manipulating degree which is lower than a manipulating degree in the idle speed range of an engine 10, so as to know that a vehicle descends in a coasting condition. If the vehicle descends in a coasting condition, a gear stage for starting the vehicle is selected on a relatively high speed side among a plurality of gear stages in accordance with the accelerating condition of the vehicle. With this arrangement, the difference in rotational speed between the input and output shafts of a clutch during re-engagement of the clutch may be reduced and the reduction ratio of the transmission may be also reduced, thereby it is possible to reduce unsatisfactory shocks due to deceleration of the vehicle when the clutch is re-engaged.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a shift control method for an automatic transmission for a vehicle.

PRIOR ART A vehicular automatic transmission that automatically shifts a stepped transmission having a plurality of gear stages by operating a shift actuator according to a pre-stored shift diagram of a shift member of the stepped transmission. It has been known. An example of this is a fully automatic manual transmission in which the shift fork of a synchronized mesh transmission, which was conventionally operated manually, is operated by a hydraulic cylinder. In such automatic transmissions, as described in Japanese Patent Laid-Open No. 59-81230, etc., the shift timing is determined based on the actual accelerator operation amount and vehicle speed from a pre-stored shift diagram. shift is executed.

Problems to be Solved by the Invention However, in the conventional shift control method for automatic transmissions, shifts are performed uniformly according to the transmission diagram regardless of the vehicle's driving condition, which impairs the drivability of the vehicle. There was a case. For example, when starting a vehicle on a downhill road, when the braking action of the brake device is released, the vehicle starts coasting without operating the accelerator pedal. In this state, when the accelerator pedal is operated to accelerate the vehicle, the clutch is engaged and power transmission begins while the stepped transmission is switched to first or second gear. Since the clutch is engaged when the vehicle is already running and the rotational speed of the input shaft to which power from the engine is transmitted is lower than the rotational speed of the output shaft of the clutch, the deceleration shock caused by engagement of the clutch is reduced. There was an inconvenience that this occurred on the vehicle.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist is that the geared transmission is automatically shifted by operating the shift actuator of the shift member of the geared transmission having a plurality of gears according to a pre-stored shift diagram. A shift control method for an automatic transmission for a vehicle, comprising: (a) a downhill coasting detection step of detecting a downhill coasting state of the vehicle; (b) a step of detecting acceleration of the vehicle; and (C) the step of detecting the downhill coasting state of the vehicle. When the vehicle is in a downhill coasting state, the present invention includes a gear stage selection step of selecting a gear stage at which the vehicle starts from among the plurality of gear stages based on the acceleration of the vehicle.

In this way, in the gear selection step, when the vehicle is coasting downhill, the gear when the vehicle starts is compared from the plurality of gears based on the acceleration of the vehicle. Since the relatively high speed side is selected, a power transmission path is formed in a relatively high speed gear stage when the clutch is engaged. Therefore, the difference in rotational speed between the input shaft and the output shaft of the clutch when the clutch is re-engaged is reduced, and the reduction ratio of the transmission, that is, the torque transmission ratio, is also reduced, causing discomfort when the clutch is re-engaged. Therefore, the deceleration block is suitably alleviated.

Here, the downhill coasting detection step is detected based on the fact that the accelerator operation amount of the vehicle is less than or equal to the operation amount when the engine is idling.

Further, the stepped transmission has at least a first gear to a fourth gear, and in the gear selection step, the higher the vehicle acceleration, the higher the vehicle acceleration, the higher the vehicle acceleration. gear, and then sequentially selects the second gear.

Furthermore, the gear stage selection process includes a clutch release process, a gear stage switching process, and a clutch re-engaging process in sequence, and the clutch re-engaging process is performed by adjusting the engine rotation rate that should be obtained after the selected gear stage is established. This is executed when there is a discrepancy between the engine speed and the actual engine speed.

Further, in the clutch re-engaging step, the transmitted torque is gradually increased according to a predetermined control formula.

EXAMPLE Hereinafter, an application example of the present invention will be explained in detail based on the drawings.

In the second time, the power of the vehicle engine 10 is transmitted to the driving wheels via the magnetic particle type electromagnetic clutch 12, the stepped transmission 14, and a differential gear device (not shown).

The magnetic particle electromagnetic clutch 12 functions as an automatic clutch in this application example, and is inserted between the crankshaft 15 and the input shaft 46 of the stepped transmission 14, as shown in FIG. Then, the torque is controlled by the excitation current supplied from the control device 16, and a torque corresponding to the excitation current is transmitted.

The crankshaft 15 and the input shaft 46 of the stepped transmission 14
correspond to the input shaft and output shaft of the magnetic particle type electromagnetic clutch 12. The stepped transmission 14 is a synchronized mesh transmission with five forward speeds and one reverse speed, which is well known as a manual transmission. and a shift rod 18 to which a shift fork (not shown) is attached for shifting to the second gear.
, a shift rod 20 to which a shift fork 19 for shifting to the third and fourth gears is attached, and a shift fork (not shown) for shifting to the fifth and reverse gears is attached. Shift rods 22 and the shift rods 18, 20, 22
A shift device is provided for selectively driving the shift position from the neutral position to the shift position. The shift device includes a 3-position hydraulic cylinder 26 for shifting that drives the shift select lever 24 in the rotational direction and drives any of the shift rods 18, 20, 22 in the axial direction, and a 3-position hydraulic cylinder 26 that rotates the shift select lever 24. and a 3-position switching hydraulic cylinder 28 that engages the lower end of the shift select lever 24 with any of the shift rods 18, 20, and 22 by positioning it at three positions in the direction of the rotation axis. We are prepared. The 3-position hydraulic cylinder 26 for shifting is controlled to 3 positions by a combination of the operation of a pair of solenoid valves 30 and 32, and the 3-position hydraulic cylinder 28 for switching is also controlled by a combination of the operation of a pair of solenoid valves 34 and 36. It is designed to be controlled in three positions depending on the combination of. That is, the solenoid valves 30, 32, 34 and 36
Due to the combination of operations, the hydraulic pressure supplied from the hydraulic pump 37 to the hydraulic circuit 38 is selectively supplied to the 3-position hydraulic cylinder 26 for shifting and the 3-position hydraulic cylinder 28 for switching. When both are on, the switching three-position hydraulic cylinder 28 engages the shift select lever 24 with the shift rod 20 for switching between the third gear stage and the fourth gear stage.
When the solenoid valve 34 is on and the solenoid valve 36 is off, the three-position switching hydraulic cylinder 28 engages the shift rod 18 for switching the shift select lever 24 between the first gear and the second gear. On the other hand, when the solenoid valve 34 is off and the solenoid valve 36 is on, the 3-position switching hydraulic cylinder 28 moves the shift select lever 24 to the shift rod 22 for switching between the 5th gear and the reverse gear. engage with.

Further, when both the solenoid valves 30 and 32 are on, the 3-position shift hydraulic cylinder 26 is positioned in a neutral state, but when the solenoid valve 30 is on and the solenoid valve 32 is off, the 3-position shift hydraulic cylinder 26 is positioned in a neutral state. If the cylinder 26 moves any of the shift rods to the first, third, or fifth speed side, and conversely, the solenoid valve 30 is off and the solenoid valve 32 is on, the three-position hydraulic cylinder 26 for shifting moves one of the shift rods to 2nd gear, 4th gear, or the reverse side. Figure 6 shows
It shows the relationship between the movement locus of the upper end of the shift select lever 24 and the gear stage established thereby.

The vehicle is equipped with various sensors for detecting driving parameters, and signals from these sensors are supplied to the control device 16. That is, from the accelerator sensor 42 provided on the accelerator pedal 40, a voltage signal vacc representing the amount of accelerator operation is sent to the control device 1.
6.

A signal t representing the engine rotation period is output from the engine rotation speed sensor 4'4 provided in the engine 10.

is output to the control device 16. An input shaft rotation sensor 50 and an output shaft rotation sensor 52 provided near the input shaft 46 and output shaft 48 of the stepped transmission 14 output a signal t1 representing the rotation period of the input shaft 46 and a rotation period of the output shaft 48. A signal toout representing the output signal is output to the control device 16. Further, from the shift position detection switches 54, 56, 58, 60 provided in the stepped transmission 14, signals N, .
1 to N, , 4 are output to the control device 16. The operating position of the 3-position hydraulic cylinder 26 for shifting is detected by a combination of signals from a pair of shift position detection switches 54 and 56, and the 3-position hydraulic pressure for switching is detected by a combination of signals from a pair of shift 1 position detection switches 58 and 60. The operating position of the cylinder 28 is detected. These shift position detection switches 54, 56, 58, and 60 are similar to those described in Japanese Patent Application No. 1983-41977 previously filed by the present applicant.

The control device 16 includes a CPU 66, a ROM 68, and a RAM 70.
, a so-called microcomputer equipped with an input interface 72, a clutch drive circuit 74, a throttle drive circuit 76, a solenoid valve drive circuit 78, etc., and which uses the memory function of the RAM 70 and receives input signals according to a program stored in advance in the ROM 68. Processing and solenoid valve 30.32.3
4.36 The drive signal for driving the solenoid valve drive circuit 7
At the same time, an excitation current for controlling the electromagnetic clutch 12 is output from the clutch drive circuit 74.

Further, the throttle drive circuit 76 outputs a drive signal to a throttle actuator 82 that drives a throttle/nottle valve 80 provided in the intake pipe of the engine 10. Furthermore, a throttle sensor 84 for detecting the opening degree of the throttle valve 80 is provided, and an output signal V of the throttle sensor 84 is supplied to the input interface 72 .

FIG. 7 shows an example of the output terminal configuration of a solenoid valve drive circuit 78 consisting of four bits, bits 0 to 3. 0
The No. 1 bit, No. 1 bit, No. 2 bit, and No. 3 bit correspond to solenoid valves 30, 32, 34, and 36, respectively. Similarly, FIG. 8 shows an example of a partial configuration of the input terminal of the human interface 72, which consists of four bits, bits 0 to 3. 0th bit, 1st bit,
The 2nd and 3rd bits are shift position detection switches 54
．． 56, 58, and 60, respectively.

Next, the operation of the shift control device for an automatic transmission configured as described above will be explained with reference to the flowcharts in FIGS.

First, in step Sl, the input signal L from each sensor is
e, j! n, jout s Vmcc s VLhs
N5w1 to N, , 4 are read. Next, in step S2, the following equations (11, (2), (3
), (4), (5), (6), and (7), the actual engine rotation speed N0 and input shaft rotation speed N! 6. Output shaft rotational speed N out, vehicle speed SPD, vehicle acceleration d
sPD, accelerator operation amount Acc, and throttle valve opening degree θ are calculated.

Nsrpm=(1/l,)x60sec ・・−+
t) NA,,=(1/li,1)×60sec...(
2) Nout = (1/to++t)
X 60sec...(3) SPD km/h
= N out・γdie・2πr, 6011
1+7·l/1000 (4) where r is the radius of the wheel and the gear ratio of the 14:1 differential gear device.

dsPD m/s”= (SPD t+%) SPD
(TI-Lll)) / ta... (5) However, SPD〉 and 5PI)〉-Lm) are values determined every fixed period tmsec by executing the interrupt routine at fixed intervals shown in Fig. 9. and its previous value.

Acc” (Vacc-νcto*a)/(V*
sx Vctos*)・100...(6) However, VCLo*a and V□8 are accelerator pedal 40
This is an output signal from the accelerator sensor 42 when the accelerator is not operated and when the accelerator is fully operated.

θ%= (vth, CLO@m)/(vll
aX, CL (11@), IQQ... (7
) However, vcoos and vM port are output signals from the throttle sensor 84 when the throttle valve 80 is fully closed and fully open.

In the subsequent step S3, the gear position determination routine shown in FIG. 10 is executed, so that the signals N□4 to N
The current gear stage is detected based on □l. Above signal N
Since □4 to N□1 are supplied to the input terminals arranged as shown in FIG. 8, they are determined by the binary number B represented by the bit arrangement of the terminals. That is, if none of the signals N□4 to N□1 are supplied, 2
Since the binary number B becomes 0, it is determined that the stepped transmission 14 is in the neutral state, and when the signals N, 2 and N5w4 are supplied, the binary number B becomes 5, so it is determined that the gear stage is in the first gear, and the signal 2 if N□2 and N5w3 are supplied
Since the base number B is 6, it is determined to be the second gear, and the signal N is
, , 4 is supplied, the binary number B becomes 1, so it is determined that the third gear is selected, and when only the signal N, , 3 is supplied, the binary number B becomes 2, so the third gear is determined. When it is determined that the gear position is 4th gear and signals N, 1 and N, 4 are supplied, the binary number B becomes 9, so it is determined that the gear position is 5th gear.
When the signals N,,l and N,,3 are supplied, the binary number B becomes 10, so it is determined that the gear is in reverse gear, and the value indicating the current gear is stored in the register γ. .

In the subsequent step S4, it is determined whether the content of the shift sequence flag Fchg indicating that a shift operation is being executed is "0". If it is not "0", the steps from step 318 described below are executed in order to preferentially execute the shift control, but if it is "0", the shift operation has been completed, so in step 5 the steps shown in FIG. 11 are executed. By executing the target gear position determination routine, the target gear position for the next shift is determined. That is, step 3MI to 5M12
In step , a shift diagram corresponding to the actual gear stage is selected from a plurality of types of shift diagrams stored in advance in the ROM 68 based on the numerical value in the register γ indicating the actual gear stage. In 5M13, the upshift shift point vehicle speed SPD and the downshift shift point vehicle speed SPD are calculated by interpolation based on the actual throttle valve opening from the shift diagram. □ is calculated. Then, in step 5M14, when the actual vehicle speed SPD becomes equal to or higher than the upshift shift point vehicle speed spo,p, step 5
In M15, the contents of the register T11 that stores the numerical value indicating the target gear stage are set to r+1, but in step 5M1
6, the actual vehicle speed SPD is the downshift shift point vehicle speed SPD. ,,7 or less, the contents of the register T1 are set to r-1 in step 5M17. That is,
The contents of the register T1 are set to be one gear higher than the current gear or one gear lower than the current gear. FIGS. 12(a), (b), and (C1) respectively show examples of the shift diagrams selected in step SM2.3M4.5M10 above, where the solid line is an upshift diagram, and the broken line is a downshift diagram. Furthermore, if the shift diagram in step 5M13 is as shown in FIG. Compare sequentially with the X-axis data on the map, and
<When it becomes X-axis data, set it to X2 and set Acc<
Assuming that the previous X-axis data to become X-axis data is X+, this is performed according to the following equation (8).

Returning to FIG. 1(a), when the target gear stage is determined as described above, in step S6, the accelerator operation amount is It is determined whether Ace is larger than the idle state, that is, the fully closed opening degree Ace""("0). If it is larger, the contents of the flag FCL for requesting clutch engagement are determined. Steps 318 and subsequent steps are executed after the actual acceleration dSPD, but if it is small, the gear position during coasting is determined in steps S7 to S12 based on the magnitude of the actual acceleration dSPD.In other words, in step S7 If the actual acceleration d SPD is greater than or equal to the predetermined judgment reference acceleration α, the gear stage T during coasting is determined in step S8.

is considered to be the fourth gear stage, but if the actual acceleration d SPD is smaller than the judgment reference acceleration α, the steering knob S9
In this step, it is determined whether the actual acceleration dSPD is greater than or equal to a predetermined judgment reference acceleration β.

If the acceleration d SPD is greater than or equal to the judgment reference acceleration value β, the gear stage γ during coasting is determined in step SIO.
, is assumed to be the third gear stage, but the actual acceleration d SPD
If the actual acceleration d SPD is smaller than the predetermined reference acceleration β, it is determined in step S11 whether the actual acceleration d SPD is greater than or equal to the predetermined reference acceleration ε. If the acceleration dSPD is greater than or equal to the determination reference acceleration ε, the gear γ during coasting is set to the second gear in step S12. Here, the magnitude relationship of each of the above judgment standard accelerations is α〈β
〈There is a relationship of ε. This is to increase safety by appropriately increasing the engine braking effect as the vehicle coasts on a steep downhill slope as the acceleration d SPD of the vehicle increases.

In step S13, steps S9 to S12
The expected engine rotation speed N when the gear T during coasting determined by the execution of is established is the following from the reduction ratio T1'' of the gear γ and the actual output shaft rotation speed N0 It is calculated according to equation (9), and it is determined in step S14 whether or not the predicted engine rotation speed N is equal to or higher than a reference rotation speed N o t that is set to be slightly higher than the rotation speed that causes the engine to stop. be judged.

N, = γ, rxNoIlt (9) The judgment in step S14 is for predicting engine stop, and in step 314 N, <Noff
If it is determined that this is the case, step 317 is executed to avoid engine stoppage.

However, if it is determined in step S14 that N1≧N, the engine will not stop even if the clutch 12 is engaged, so step 315 is executed and the It is determined whether the target gear position γm is larger than the coasting gear position T1 determined in steps S9 to 312. This step S
15 is for determining whether or not the engine rotation becomes unstable due to low rotation when the electromagnetic clutch 12 is engaged. If it is determined in step S15 that T8<γ1, the vehicle speed is not sufficiently high for gear γ3 during coasting, so step 317 and below are executed. However, in step S15, T1
If it is determined that ≧T, the gear stage γ1 during coasting
Since the vehicle speed is sufficiently high for the target gear position, step 816 is executed to update the target gear stage T1 and set the contents of the flag F'ct to "1".

In step 318 of FIG. 1(b), the content of the shift sequence flag Fchq is determined, and if the content of the shift sequence flag Fchw is "0", control is performed to start and stop the vehicle. Step 31
9 and below are executed, but the shift sequence flag F ch
If the content of g is "4", it is assumed that only the gear stage is being changed, and steps 323 and subsequent steps are executed, and the gear stage changing operation is continued. Soshi′ζ,
If the content of the shift sequence flag Fchg is neither "0" nor "4", the shift operation routine of step S22 is directly executed as a shift during driving, including throttle operation and clutch operation.

In step 318 above, the shift sequence flag F
If it is determined that the content of chg is "0", it is determined in step 319 whether or not the electromagnetic clutch 12 has been fully engaged, that is, whether the vehicle is running normally or whether the vehicle is starting or stopping. It is determined whether the difference IN, -Ni,l between the engine rotational speed N and the input shaft rotational speed N,7 is larger than a predetermined constant value ΔN.

The above value ΔN is a value for determining the fully engaged state of the electromagnetic clutch 12, and a value of about 50 rpm is adopted in consideration of measurement errors. IN in step S19.

If it is determined that Ntnl>ΔN, the electromagnetic clutch 12 has not yet completed engagement and the vehicle is starting or stopping, so steps 824 and subsequent steps described below are executed. If it is determined that ll≦ΔN, it means that the engagement of the electromagnetic clutch 12 has been completed, so step S20 is executed. This step S2
At 0, it is determined whether the target gear stage indicated by the contents of register γ8 and the actual gear stage indicated by the contents of register T match. If they do not match, step S21 is executed, and the contents of the shift sequence flag Fckg are first set to "1" prior to the shift operation, and then, in step S22, the shift operation routine shown in FIG. 14 is executed. As a result, a series of speed change operations are performed to switch the gear position of the stepped transmission 14 to the target gear position indicated by the contents of the register T7.

First, in step SHI, the shift sequence flag F
The contents of the are determined. Shift sequence flag F
If the content of chq is "1", a series of steps SH2 to SH5 are executed to start a power cutoff operation. In step SH2, it is determined whether the actual throttle valve opening θ is larger than its minimum opening θcto□. If not, steps SH6 and subsequent steps to be described later are executed to switch the meshing of the gear stages, but if it is, the control amount Vth to the throttle actuator 82 is reduced by a constant value ΔVth in step SH3. In the following step SH4, the control amount VCL for the electromagnetic clutch 12 is maintained at the previous control amount VeL-1), and each electromagnetic valve 30.32.3 for shifting
The content of the control amount Vshift for 4.36 is zero, that is, a state in which no drive signal is output to any solenoid valve. Then, in step SH5, the contents of the shift sequence flag F'chg are set to rlJ. While the above series of steps are repeated, when the control amount Vth for the throttle actuator 82 is decreased, the throttle valve opening degree θ is determined to be zero in step SH2, and from then on, steps SH6 and subsequent steps are performed. executed.

In step SH6, it is determined whether the actual gear stage stored in the register T and the target gear stage stored in the register T1 match or not. Therefore, Step 5 HIO and subsequent steps described below are executed, but if - is not met, Step SH is executed.
At step 7, the electromagnetic clutch 12 is released to avoid gear shift failure due to engine inertia, etc.
1 is set to zero, and the throttle valve 1111ffiV, which has already been set to zero, is maintained at that value in order to fully close the throttle valve opening θ and prevent the engine 10 from revving up. After the gear change routine of step SH8 is executed, the content of the shift sequence flag Fchq is set to "2" in step SH9.

The gear stage switching routine of step SH8 is executed, for example, as shown in FIG. 15. First step SGI
By processing the data indicating the target gear stage stored in the register T1 using the signal processing routine shown in FIG. Convert to a number that can be output as a bit array. That is, in order to convert the data indicating the target gear stage into data having the same arrangement as the input terminals of the input interface 72 shown in FIG. is converted into shift side data γI'□ and select side data γst for operating the switching hydraulic cylinder 26. For example, if the target gear is the first gear, the shift side data γ1□ is rlJ and the select side data γIL is "4", and if the target gear is the second gear, the shift side data T ″□ is ``2
” and the select side data γ1□ is set to “4”, and if the target gear stage is the third gear stage, the shift side data r”sh is set to “1” and the select side data γ sl is set to “O”,
If the target gear is the 4th gear, shift side data γ
If sk is "2" and select side data γ*1 is "0", and the target gear is 5th gear, shift side data γ sb is "1" and select side data Tl1tL is "
If the target gear is the sixth (reverse) gear, the shift side data TII is set to "2" and the select side data γ11 is set to "8".

Returning to FIG. 15, in the following step SG2, the contents of the register T are converted into shift side data γ and select side data T and L by a processing routine not shown, just as described above. These shift side data T0 and select side data TIL are detected by shift position W detection switches 54, 56 .
The signal N, w4 to N□l supplied from 58.60 to the input interface 72 is composed of the lower 2 bits and the upper 2 bits (including the lower 2 bits of "0" as a numerical value). You can also do this.

In step SG3, select side data r"IL based on the target gear position and select side data γ based on the actual gear position are
, L, and in step SG4, the shift side data γ'', based on the target gear stage are determined.
It is determined whether or not the shift side data γ based on the actual gear stage and the shift side data γ are lost. If both the determinations in steps SG3 and SG4 are affirmative, there is no need to change the gear stage, so step SG5 is executed and the control amount V is changed. The contents of ift are set to zero. However, step SG
Even if the determination in step 3 is affirmative, if the determination in step SG4 is negative, step SG6 is executed and the contents of the control amount Vski□ are set as shift-side data γsh based on the target gear stage.

As a result, the three-position hydraulic cylinder 26 for shifting is driven in step S9, which will be described later, and the target gear stage is established. Further, if the judgment in step SG3 is negative, it is necessary to use a shift rond different from that currently engaged by the shift select lever 24, so in step SG7 shift side data γ based on the actual gear position is used. It is determined whether □ is zero, that is, whether the three-position shift hydraulic cylinder 26 is in the neutral position. If the judgment in step SG7 is affirmative, the content of the control amount Vshift is changed to the target gear stage in step SG8 in order to operate the 3-position switching hydraulic cylinder 28 to a position for selecting a shift rond for operating the target gear. The select side data γ st is based on . However, if the determination in step SG7 is negative, in order to operate the three-position hydraulic cylinder 26 for shifting to the neutral position, a control amount V
The content of lkift is set to "3". This control 1vsh
Since the content "3" of ift becomes "11" in binary, drive signals are outputted from the 0th bit and the 1st bit of the electromagnetic valve drive circuit 78 to the electromagnetic valves 30 and 32, respectively, in step S9. When the three-position hydraulic cylinder 26 for shifting is operated to the neutral position in this way, shift rond is selected in steps SG8 and S9 of the next cycle, and step SG of the next cycle is activated.
6 and step S9, the target gear stage is established.

When the execution of the gear changeover routine in step SH8 is completed in this way, the register γ6 storing the numerical value indicating the target gear position and the register γ storing the numerical value indicating the actual gear position are identical in content. The 14th
The judgment at step SH6 in the figure is affirmed, and a series of steps 5HIO to 5) (15) for power retransmission are executed. That is, in step 5HIO, the actual throttle valve opening θ is equal to the accelerator operation I A c c It is determined whether it is smaller than .Initially, it is small, so step 5
Control lv for the electromagnetic clutch 12 in HII. ,
is increased by a predetermined constant increase value ΔVCI. In the following step 5H12, the control amount Vc
Transmission torque value T of electromagnetic clutch l2 where L is predetermined
It is determined whether the size corresponds to "ct".

The above value TcL is predetermined in order to open the throttle valve after the electromagnetic clutch 12 starts engaging, and corresponds to a relatively small transmission torque after the electromagnetic clutch 12 starts engaging. If the judgment in step 5H12 is negative, there is a risk that the electromagnetic clutch 12 is not sufficiently engaged and the engine 10 will idle if the throttle valve is opened, so step 5H13 is skipped and step 5H14 is performed. The content of the shift sequence flag Fckg is set to "3". While the above steps are repeatedly executed, if the control amount VcL for the electromagnetic clutch 12 is increased in step 5HII, the determination in step 5H12 is affirmed, so step 5F (13) is executed and the control amount for the throttle actuator 82 is increased. V is increased by a predetermined constant value Δ■, and the content of the shift sequence flag FCh9 is set to "3" in step 5H14.Then, in the process of repeatedly executing steps 5HI0 to 5H14, the control The amount is gradually increased,
Each time the throttle valve opening θ is the target throttle valve opening θ
. 2 will be followed. As a result, step 5H
Since the decision in LO is affirmed, step 5HI5
is executed and the contents of the gear shift sequence flag Fchi become “
0".

When the speed change operation routine of step S22 in FIG. 1(b) is completed as described above, in step S25
. Each control value such as V, V, h, and □ is output, and the electromagnetic clutch 12, throttle actuator 82, electromagnetic valves 30, 32, 34, 36, etc. are driven. As a result,
The gear position of the stepped transmission 14 is switched to the target gear position.

If it is determined in step S20 that the current gear and the target gear match, then the input shaft rotational speed Nin is changed to the N in step 326 since the shift operation has been completed. It is determined whether or not the value is larger than ff. In this step S26, Ntg>Norr
If it is determined that the engine 10 stops rotating or becomes unstable, step 327 is performed.
is executed and the operation amount Vcl for the electromagnetic clutch 12 is set to the maximum value yc,,maX, but on the contrary, step S
N8 in 26. , ≦N07. If it is determined that the engine 10 stops rotating or becomes unstable, step 32B is executed and the operation amount (■) for the electromagnetic clutch 12 is changed. , is assumed to have a minimum value of zero.

In step S24, which is executed when it is determined in step S19 that engagement of the electromagnetic clutch 12 is not completed, the target gear stage indicated by the contents of register γ8 and the contents of register γ It is determined whether or not the actual gear stage indicated by matches the actual gear stage. If they match, it means that the engagement of the electromagnetic clutch 12 is incomplete and the gear stage switching has been completed.
In step S29, it is determined whether the vehicle starts or stops based on the accelerator operation amount Acc.

That is, the accelerator operation I A c c is the minimum value A
It is determined whether the value of the flag FcL is greater than ``ce'' or not. If the determination in step S29 is negative, it is not a start, so it is determined in step S30 whether or not the content of the flag FcL is "O". If the determination in step S29 is affirmative, the vehicle is in a starting state, so step 331 is executed and the control M v et is determined according to the control equation for starting the vehicle shown in the following equation α.

veL=(N11-NidL)×K...0 (ll However, K is a constant. If it is determined in step S30 that the contents of the flag FcL have not yet been reset to "0",
Since engagement of the electromagnetic clutch 12 is still required, step S32 is executed and the control amount ■□ is increased according to the following formula 〇〇. However, step S
If it is determined in step 30 that the contents of the flag FcL have already been reset to "0", step 328 is executed and the contents of the control 'fV th for the throttle actuator 82 are set to zero, and In step 335, the control amount vsh5 is set for switching gears according to the routines shown in FIGS. 15 and 16. is determined.

As described above, according to this application example, when it is determined in step S6 that the vehicle is in a downhill coasting state, the gear stage of the vehicle changes from the plurality of gear stages to the acceleration d SPD of the vehicle.
Therefore, when the electromagnetic clutch 12 is engaged when the vehicle starts after starting coasting downhill, a power transmission path is formed at a relatively high speed gear. Therefore, the rotational speed difference between the input shaft (crankshaft 15) and the output shaft (input shaft 46) of the electromagnetic clutch 12 when the electromagnetic clutch 12 is re-engaged is reduced, and the reduction ratio of the stepped transmission 14 is reduced. That is, since the torque transmission ratio is also reduced, the unpleasant deceleration shock that occurs when the electromagnetic clutch 12 is reconnected can be suitably alleviated.

Further, in this application example, the content of the control amount VCt is set to zero from step S7 onward.

V cL = V cl (n-1) +Δ■,
...00 However, Δ■□ is the increase amount per calculation cycle, and as described above, steps S27, S28, S31,
In S32, the control amount when the vehicle starts, stops, etc.■
. , is determined, the control amount A for the throttle actuator 82 is determined to correspond to the actual accelerator operation amount A(() in step S33.

In step 31B, the shift sequence flag Fc
If it is determined that the content of k* is "4", or if the determination in step S24 is negative, step 323 is executed, so that the content of the shift sequence flag Fchg becomes "4". After being done,
In step S34, the control amount ■ is applied to the electromagnetic clutch 12 in order to maintain the released state of the electromagnetic clutch 12 and the fully closed state of the throttle valve 80 so that the gear stage can be easily established.
In S12, as the acceleration dSPD of the vehicle increases, the shift is made from the fourth gear to the third gear and then to the second gear, so that the vehicle coasts down a steep downhill slope with the electromagnetic clutch 12 engaged. When driving, it has the advantage of providing an appropriate engine braking effect.

Furthermore, in the application example described above, when it is determined in step S12 that the expected rotational speed N, has become smaller than N of f
This prevents the engine 10 from stopping or becoming unstable when the electromagnetic clutch 12 is engaged to start the vehicle during downhill coasting. In such a case, as the vehicle speed increases due to downhill coasting, the predicted rotational speed N1 becomes N01. There is an advantage that the electromagnetic clutch 12 starts to engage immediately when it reaches .

The above description has been made based on the drawings showing one application example of the present invention, but the present invention is also applicable to other embodiments.

For example, in the application example described above, the magnitude of the vehicle acceleration d SPD during downhill coasting has three types of judgment reference values α,
Although the judgment is made based on β and ε, there is no problem even if two or four types of judgment reference values are used.

Furthermore, although the magnetic particle type electromagnetic clutch 12 is used in the application example described above, other types of automatic clutches that can control engagement, such as a hydraulic clutch, may also be used.

Furthermore, although the magnetic particle type electromagnetic clutch 12 in the application example described above is provided between the engine 10 and the stepped transmission 14, it may be inserted elsewhere in the power transmission path of the engine 10. No problem.

Furthermore, although the aforementioned stepped transmission 14 was a synchronous mesh type transmission, it is a planetary gear type stepped transmission in which gears are switched by selectively operating a plurality of frictional engagement devices. There is no problem even if there is.

It should be noted that the above description is merely an example of application of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are flowcharts illustrating the operation of the shift control device of FIG. 2. FIG. FIG. 2 is a block diagram showing a shift control device for a stepped automatic transmission to which the present invention is applicable. FIG. 3 is a diagram showing the characteristics of the electromagnetic clutch shown in FIG. 2. 4 and 5 are diagrams showing a hydraulic drive device for switching gear stages of the stepped transmission shown in FIG. 2, and are sectional views of essential parts as seen from cross sections at right angles to each other. FIG. 6 is a diagram showing the relationship between the locus of the end of the shift select lever in FIGS. 4 and 5 and the shift position. 7th
8 and 8 are diagrams respectively illustrating the terminal configuration of the electromagnetic valve drive circuit of FIG. 2 and the terminal configuration of a part of the input interface. Figure 9, Figure 10, Figure 11, Figure 14
15 and 16 are diagrams showing the routines executed in the flowcharts of FIGS. 1(a) and 1(a), respectively. FIG. 12(a), TC) is a diagram showing a shift diagram pre-stored in the ROM in FIG. b) is the diagram selected in the second gear stage, (C1 is the diagram selected in the fifth gear stage. 10: Engine 12: l Powder type electromagnetic clutch (automatic clutch) 14: Stepped transmission Fig. 1 (aJ 3r!A Fig. 6 Fig. 7 Fig. 8ffi Figure 9 Figure 12 Figure 13 km/h

Claims (5)

[Claims] (1) An automatic transmission for a vehicle in which a stepped transmission having a plurality of gears is automatically shifted by operating a shift actuator according to a pre-stored shift diagram of a shift member of the stepped transmission. A downhill coasting detection step of detecting a downhill coasting state of the vehicle; a step of detecting acceleration of the vehicle; and when the vehicle is in the downhill coasting state, A shift control method for an automatic transmission for a vehicle, comprising the step of selecting a gear at the time of starting from among the plurality of gears based on the acceleration of the vehicle. (2) The vehicle according to claim 1, wherein the downhill coasting detection step is detected based on the fact that the accelerator operation amount of the vehicle is equal to or less than the operation amount when the engine is idling. Shift control method for automatic transmission. (3) The stepped transmission has at least a first gear to a fourth gear, and in the gear selection step, the higher the vehicle acceleration is, the higher the gear is selected from the fourth gear to the third gear.
3. The shift control method for an automatic transmission for a vehicle according to claim 1, wherein the shift control method is for sequentially selecting a first gear and then a second gear. (4) The gear stage selection process sequentially includes a clutch release process, a gear stage switching process, and a clutch re-engaging process. A shift control method for an automatic transmission for a vehicle according to any one of claims 1 to 3, which is executed when the rotational speed and the actual engine rotational speed match. (5) The automatic transmission for a vehicle according to any one of claims 1 to 4, wherein in the clutch re-engaging step, the transmitted torque is gradually increased according to a predetermined control formula. Machine shift control method.