JP2000104823A - Control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the durability of a friction element when an acceleration pedal is depressed and a torque is increased, after the drop of a car speed in a state in which a gear shift is not carried out during the running of a manual mode, in an automatic transmission in which an automode switching a speed change step based on the speed change characteristic set in advance and a manual mode switched by the manual operation of a operator are provided in parallel. SOLUTION: A forced shift down car speed Vo is set on the higher car speed side than 4-3 shift down line D43 at the automode time and in a manual mode, 4-3 shift down speed change is carried out forcedly regardless of the existence/absence of a manual gear shift when a car speed V is lowered than this forced shift down car speed Vo. After the forced 4-3 shift down speed change is generated at the point of time Z further even if an engine load is increased at the low car speed time point Y like an arrow mark B, as the car speed is already switched to the low speed change step, the durability of a friction element is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving mode in which an automatic shifting is performed automatically based on a preset shifting characteristic, and a manual mode in which shifting is performed based on a manual operation by a driver. The present invention relates to a control device for an automatic transmission provided with an automatic transmission and belongs to a technical field of an automatic transmission for a vehicle.

[0002]

2. Description of the Related Art In recent years, as an automatic transmission for a vehicle, in addition to an automatic mode in which a gear is automatically switched based on a preset shift characteristic, a manual mode in which the gear is switched by a shift lever operation of a driver is provided. Those equipped with them have been put to practical use. In such an automatic transmission, for example, if the shift lever is shifted to the D (drive) range, the automatic mode is achieved, and the M (manual)
When the shift lever is shifted into the range, the manual mode is achieved. When the shift lever is swung forward in the M range, the shift speed is shifted up by one step, and when the shift lever is swung backward, the shift speed is shifted down by one step.

The shift characteristics in the auto mode are set based on the running state of the vehicle such as the vehicle speed and the throttle opening (engine load). The vehicle speed (shift vehicle speed) at the time of shifting is increased as the engine load increases. It is provided on the vehicle speed side. Therefore, a downshift accompanying a decrease in vehicle speed and a downshift accompanying depression of an accelerator pedal (increase in engine load) automatically occur.

On the other hand, in the manual mode, shifting of the gear position is basically left to the discretion of the driver, and the shift operation can be freely performed regardless of the running state of the vehicle considered in the automatic mode. Is possible. Therefore, downshifts due to a decrease in vehicle speed and downshifts due to depression of the accelerator pedal, such as in the auto mode, do not occur automatically, and only when the driver performs a downshift operation with the shift lever, the shift speed is changed. Is shifted down.

[0005]

In general, shifting in this type of automatic transmission is performed by selectively engaging a plurality of friction elements such as clutches and brakes to switch a power transmission path of a transmission gear mechanism. Done. Here, consider the case where the accelerator pedal is depressed and the torque increases while the vehicle speed is decreasing and the vehicle speed is decreasing to near the downshift vehicle speed set in the shift characteristics in the auto mode. The downshift is automatically performed when the pedal is depressed, so there is no problem of slippage or durability of the friction element. On the other hand, in the manual mode, the downshift does not occur unless manually operated by the driver. Therefore, the current gear position is maintained as it is, and the friction elements fastened at the current gear position may cause slip and durability problems. In order to completely increase the torque of the engagement friction element in the current gear, the torque capacity of the friction element must be increased, and the size of the friction element is so large that the transmission layout cannot be established. Becomes

Japanese Unexamined Patent Publication No. Hei 8-233087 discloses that when the running state of a vehicle changes without a shift operation being performed in a manual mode, as a result, the engine speed drops below a predetermined minimum speed. A technique for forcibly downshifting the shift speed is disclosed. However, there is no disclosure as to at what timing such a forced downshift in the manual mode is performed in relation to the shift characteristics in the auto mode, and the above problem cannot be addressed.

In particular, the number of friction elements to be engaged is reduced in order to suppress problems such as a complicated shift control or a shock, and a low load, When the accelerator pedal is depressed from a low vehicle speed range to increase the torque, the problem becomes more remarkable because the torque per friction element further increases.

The present invention has been made in view of the above circumstances, and in the manual mode in which the gear change is basically left to the driver's discretion, the durability of the friction element is increased due to an increase in the torque accompanying the depression of the accelerator pedal. It is an object of the present invention not to be damaged.

[0009]

In order to solve the above problems, the present invention uses the following means.

First, according to the invention described in claim 1 of the present application, a shift is automatically performed based on a preset shift characteristic, and a shift is performed based on a manual operation by a driver. And a manual mode in which the shift down vehicle speed in the shift characteristic is set to a higher vehicle speed side as the engine load increases, and the vehicle speed in the manual mode is equal to or less than a predetermined vehicle speed. When the downshift is performed from a gear position in which the number of friction elements engaged in torque transmission among the engaged friction elements is small, the forced downshift means forcibly downshifts when The predetermined vehicle speed when the forced downshift is performed is larger than the downshift vehicle speed in the above shift characteristics. Characterized in that the Kusuru control means are provided.

According to this, in the auto mode,
In the manual mode, when such a downshift is not automatically performed, the number of friction elements to be engaged is small, and thus the downshift is automatically performed with an increase in the engine load. When downshifting from a gear with a small number of friction elements participating in torque transmission, the forced downshift vehicle speed in manual mode is increased compared to the automatic downshift vehicle speed in auto mode. When the vehicle speed has decreased to a value close to the automatic downshift vehicle speed, it means that a downshift has already occurred in the gear position.

As a result, since a small number of friction elements that were engaged in the gear before the shift and participated in the torque transmission are released, even if the accelerator pedal is depressed in this state and the torque increases, the gear shift is not performed. There is no such a problem that the friction element, which has been engaged in the previous gear, slips and its durability is impaired. In addition, there is no need to increase the torque capacity of the friction element that is engaged in the shift stage before the shift, and the layout of the transmission can be maintained.

According to a second aspect of the present invention, in the first aspect of the present invention, the lowest value of the downshift vehicle speed in the shift characteristic is a friction element which participates in torque transmission at a shift speed before shifting. Is the lowest vehicle speed at which torque can be transmitted, and the control means sets a predetermined vehicle speed when the forced downshift is performed to be higher than the minimum vehicle speed.

The automatic shift-down vehicle speed in the auto mode is set to a higher vehicle speed side as the engine load increases, so that the automatic shift-down vehicle speed takes its minimum value when fully closed. According to the second aspect of the invention, in particular, the minimum value of the automatic downshift vehicle speed is limited to a limit at which the friction element engaged in torque transmission before the shift and participating in torque transmission can transmit torque. Because the vehicle speed is low, fuel efficiency is improved, and in auto mode, when the vehicle speed drops in a coasting state where the accelerator pedal is hardly depressed, the vehicle speed decreases before the torque transmission by the friction element becomes defective. If the accelerator pedal is depressed before the downshift occurs due to the decrease in vehicle speed, the downshift occurs immediately due to the increase in the engine load before the friction element slips. In any case, the durability of the friction element is ensured.

With such a configuration, the forced shift-down vehicle speed in the manual mode is made larger than the minimum value of the automatic shift-down vehicle speed in the above-mentioned auto mode. When the vehicle speed drops in the coasting state where the vehicle is hardly depressed, a forced downshift occurs before the torque transmission by the friction element becomes defective, so that the friction element does not slip even if the accelerator pedal is subsequently depressed. In any case, the durability of the friction element is ensured.

Next, according to a third aspect of the present invention, in the first aspect of the present invention, the control means increases the predetermined vehicle speed when the forced downshift is performed as the engine load increases. And

According to the third aspect of the invention, in particular, the forced downshift vehicle speed in the manual mode is corrected in accordance with the engine load, and is set to a larger value as the engine load is larger. Thus, in order to cover the magnitude of the torque, the forced downshift occurs early while the vehicle speed is decreasing, and the durability of the friction elements that are engaged in the gear before the shift and that participate in the torque transmission are effectively realized.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the control means increases the predetermined vehicle speed when the downshift is performed as the temperature of the hydraulic oil is lower. It is characterized by.

According to the fourth aspect of the invention, particularly, the forced downshift vehicle speed in the manual mode is corrected according to the oil temperature, and the larger the oil temperature, the larger the value. When the vehicle speed is low, the forced downshift occurs early during the reduction of the vehicle speed in order to cover the response delay, and the durability of the friction element that is engaged in the gear before the shift and that participates in the torque transmission is effectively realized.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by describing embodiments of the present invention.

FIG. 1 shows an operation section of a vehicle provided with an automatic transmission according to this embodiment. A shift plate 3 is provided on a guide plate 2 provided on a console section 1 on the side of a driver's seat. A shift gate 4 to be guided is provided. The shift gate 4 is located in the vehicle longitudinal direction (shift direction).
And a route in the vehicle width direction (selection direction), which is a stepped route, and is R (retreat), N (neutral), D (automatic) backward from the foremost P (parking) range selection position. Each range selection position is provided in order. Also,
M (manual) in the select direction from the D range selection position
A range selection position is arranged, and the front of the neutral position Mc is a shift-up position Mu, and the rear is a shift-down position Md.

As shown in FIG. 2, below the guide plate 2, when the shift lever 3 is operated to the M range selection position, the shift lever 3 is pressed by the base 3a of the lever 3 and turned on.
When the M range switch 5 and the shift lever 3 are pivotally operated to the shift-up position Mu or the shift-down position Md, the switch lever 6 is pressed and turned on by the switch operating member 6 linked to the lever 3 around the support shaft 6a. A shift-up switch 7 and a shift-down switch 8 are provided.

FIG. 3 shows an automatic transmission 10 according to this embodiment.
FIG. 2 is a skeleton view showing a mechanical configuration of the automatic transmission 1.
0 is a torque converter 20 as a main component.
And first and second planetary gear mechanisms 30 and 40 as transmission gear mechanisms driven by the output of the converter 20, and a plurality of clutches and brakes for switching power transmission paths of the planetary gear mechanisms 30 and 40. Friction elements 51-55
And a one-way clutch 56.
1 in D range as auto mode achievement range
Fourth speed, first to fourth speeds in the M range as a manual mode achievement range, and reverse speed in the R range are achieved.

The torque converter 20 includes a pump 22 fixed in a case 21 connected to the engine output shaft 9.
A turbine 23 disposed opposite to the pump 22 and driven by the pump 22 via hydraulic oil;
Transmission case 1 interposed between turbine 2 and turbine 23
1 is provided between the case 21 and the turbine 23 and is supported between the case 21 and the turbine 23 via the one-way clutch 24 to directly connect the engine output shaft 1 and the turbine 23 via the case 21. And a lock-up clutch 26, and the rotation of the turbine 23 is transmitted through a turbine shaft 27 to planetary gear mechanisms 30, 40.
Output to the side.

An oil pump 12 driven by the engine output shaft 9 via a case 21 of the torque converter 20 is disposed behind the torque converter 20.

The first and second planetary gear mechanisms 30 and 40 each include sun gears 31 and 41 and sun gears 31 and 4.
Plural pinions 32 ... 32, 42 ... 42 meshed with one
And pinion carriers 33 and 43 for supporting these pinions 32 ... 32, 42 ... 42, and pinions 32 ... 3
The ring gears 34, 44 meshed with 2, 42,.

Then, the turbine shaft 27 and the first
A forward clutch 51 is provided between the sun gear 31 of the planetary gear mechanism 30 and a reverse clutch 52 is provided between the turbine shaft 27 and the sun gear 41 of the second planetary gear mechanism 40.
A 3-4 clutch 53 is interposed between the pinion carrier 43 and the second planetary gear mechanism 40.
2-4 brake 54 for fixing the sun gear 41 is provided.

Further, the ring gear 34 of the first planetary gear mechanism 30 and the pinion carrier 43 of the second planetary gear mechanism 40
The low reverse brake 55 and the one-way clutch 56 are arranged in parallel between the transmission case 11 and these components, and the pinion carrier 33 of the first planetary gear mechanism 30 and the second planetary gear mechanism Forty ring gears 44 are connected, and the output gear 13 is connected to them.

The output gear 13 is meshed with a first intermediate gear 62 on an idle shaft 61 constituting an intermediate transmission mechanism 60, and is connected to a second intermediate gear 63 on the idle shaft 61 and a differential gear. The input gear 71 of the differential gear 70 meshes with the rotation of the output gear 13 and is input to the differential case 72 of the differential 70.
The left and right axles 73, 74 are driven via the zero.

Here, the relationship between the operating state of the friction elements 51 to 55 such as the clutches and brakes and the one-way clutch 56 and the shift speed is summarized in Table 1 below.

[0031]

[Table 1] The peripheral portions of the first and second planetary gear mechanisms 30 and 40 are specifically configured as shown in FIG. 4, and as shown, the transmission case 11 includes a turbine shaft for speed control. A turbine speed sensor 305 for detecting the speed of 27 (turbine speed) is attached.

As shown in FIG. 5 or FIG. 6, the hydraulic control circuit 100 in the automatic transmission 10 includes a regulator valve for generating a line pressure, a reducing valve for reducing the line pressure to a predetermined constant pressure, Alternatively, in addition to a manual valve (both not shown) for switching the range by manual operation, a low reverse valve 103, a bypass valve 104, and a bypass valve 104, which are operated at the time of gear shifting to switch oil paths leading to the friction elements 51 to 55. -4 shift valve 105 and lock-up control valve 106
And first and second ON-OFF solenoid valves (hereinafter referred to as “first SV” and “second SV”, respectively) 111 and 11 for operating these valves 103 to 106.
2, a solenoid relay valve (hereinafter, referred to as a “relay valve”) 107 for switching the supply destination of the operating pressure from the first SV 111, and generation, adjustment, and control of the operating pressure supplied to the hydraulic chambers of the friction elements 51 to 55. The first to third duty solenoid valves (hereinafter referred to as “first DS
V ”to“ third DSV ”) 121, 122, 123
Etc. are provided.

The first and second SVs 111 and 112 and the first to second SVs
The third DSVs 121 to 123 are all three-way valves,
A state in which the upstream oil path is connected to the downstream oil path and a state in which the downstream oil path is drained are realized. When the first and second SVs 111 and 112 are ON, they connect the upstream oil passage and the downstream oil passage. 1st to 3rd DSV 121 to
123 is OFF, that is, the duty ratio (1 ON
-When the ON time in the OFF cycle is 0%, the oil passage is fully opened to completely communicate the upstream oil passage and the downstream oil passage, and when ON, that is, the duty ratio is 100%.
In this case, the oil pressure on the upstream side is cut off, the oil pressure on the downstream side is drained, the hydraulic pressure on the upstream side is set as the original pressure at an intermediate duty ratio, and the oil pressure is adjusted downstream to a value corresponding to the duty ratio. Generate

Of the friction elements 51 to 55, the 2-4 brake 54 composed of a band brake has a fastening chamber 54a and a release chamber 54b as hydraulic chambers to which the operating pressure is supplied.
The fastening is performed when the operating pressure is supplied only to the fastening chamber 54a, the operating pressure is supplied only to the release chamber 54b, the operating pressure is supplied to both the chambers 54a and 54b, and the both chambers 54a , 54b are released when the operating pressure is not supplied, while the other friction elements 51 to 5 are released.
Reference numerals 3 and 55 each have a single hydraulic chamber, which is fastened when operating pressure is supplied to the hydraulic chamber and released when operating pressure is not supplied.

The pressure of the hydraulic oil discharged from the oil pump 12 is adjusted to a predetermined line pressure by a regulator valve, and further reduced to a predetermined constant pressure by a reducing valve. It is supplied to the first and second SVs 111 and 112.

The constant pressure is supplied to the relay valve 107 via the line 203 when the first SV 111 is ON, and when the spool of the valve 107 is located on the right side in the drawing, the bypass valve 104 is further connected via the line 204.
Is supplied as a pilot pressure to the control port 104a at one end to urge the spool of the bypass valve 104 to the left. On the other hand, when the spool of the relay valve 107 is located on the left side, the constant pressure is
The pilot pressure is supplied to a control port 105a at one end of the shift valve 105 as a pilot pressure.
5 is urged to the right.

The constant pressure is supplied to the bypass valve 104 via the line 206 when the second SV 112 is ON,
When the spool of the valve 104 is located on the right side, it is further supplied as pilot pressure to the control port 106a at one end of the lock-up control valve 106 via the line 207 to urge the spool of the control valve 106 to the left. . On the other hand, when the spool of the bypass valve 104 is located on the left side,
The pressure is supplied as pilot pressure to a control port 103a at one end of the low reverse valve 103 through 8 to urge the spool of the low reverse valve 103 to the left.

The line pressure is set to 3 via the main line 200.
-4 is supplied to the shift valve 105, and when the spool of the valve 105 is located on the right side, it is introduced into the accumulator 141 via the line 210.

The first DSV 121 is supplied with the line pressure as the control source pressure via the first output line 211 in each of the D, M, and R travel ranges by switching the oil passage by a manual valve.

Similarly, the second and third DSVs 122 and 123 are provided with oil passage switching by a manual valve.
In each of the forward ranges D and M, the line pressure is supplied as the control source pressure via the second output line 212, respectively.

Downstream of the first DSV 121 is a line 21
When the spool of the valve 103 is located on the right side through the servo apply line 215, the 2-4 brake 54
To the fastening chamber 54a. On the other hand, when the spool of the low reverse valve 103 is located on the left side, it is further guided to the hydraulic chamber of the low reverse brake 55 via the low reverse brake line 216. Note that an accumulator 142 is provided on the line 214.

The second output line 212 is also led to the 3-4 shift valve 105. When the spool of the valve 105 is located on the left side, the line pressure is led to the lock-up control valve 106 via the line 218, When the spool of the valve 106 is located on the left side, it is further guided to the hydraulic chamber of the forward clutch 51 via the forward clutch line 219. The line 220 branched from the forward clutch line 219 is led to the 3-4 shift valve 105. When the spool of the valve 105 is located on the left side, the line 220 communicates with the first accumulator 141 via the aforementioned line 210 and When the spool of the valve 105 is located on the right side, it communicates with the release chamber 54b of the 2-4 brake 54 via the servo release line 221.

Downstream of the second DSV 122 is a line 22
2 through the control port 10 at one end of the relay valve 107.
By supplying pilot pressure to the port guided by 7a, the spool of the relay valve 107 is urged to the left. In addition, the line 2 branched from the line 222
23 is led to the low reverse valve 103, and the valve 1
Line 2 when spool 03 is on the right
Leads to 24. From this line 224, the orifice 1
The line 225 is branched via the line 51, and the branched line 225 is connected to the 3-4 shift valve 105.
When the spool of the 3-4 shift valve 105 is located on the left side, the servo release line 22
It is guided to the release chamber 54b of the 2-4 brake 54 via 1.

From line 225, line 2
26 is branched, and this line 226 is led to the bypass valve 104, and when the spool of the valve 104 is located on the right side, the 3-4 clutch line 227
Through the hydraulic chamber of the 3-4 clutch 53.

The downstream side of the third DSV 123 is connected to the line 22
8 and is led to the lock-up control valve 106, and when the spool of the valve 106 is located on the right side, it communicates with the forward clutch line 219.

The line pressure is supplied to the low reverse valve 103 through the third output line 213 in each of the R and N ranges by switching the oil path by a manual valve, and the spool of the valve 103 is positioned on the left side. When this is done, the line pressure is guided to the hydraulic chamber of the reverse clutch 52 via the reverse clutch line 230. The line 231 branched from the third output line 213 is led to the bypass valve 104, and when the spool of the valve 104 is located on the right side, the pilot pressure is supplied to the control port 103a of the low reverse valve 103 via the line 208 described above. The line pressure is supplied as
Push the spool No. 3 to the left.

Here, the combinations (solenoid patterns) of the operating states of the first and second SVs 111 and 112 and the first to third DSVs 121 to 123 for each shift speed are set as shown in Table 2 below.

In Table 2, (○) indicates the first and second SV1.
ON for 11 and 112, 1st to 3rd DSV 121
Reference numerals 123 to 123 are OFF, and all indicate a state in which the upstream oil passage is communicated with the downstream oil passage and the original pressure is supplied to the downstream as it is. (×) indicates the first and second
OFF for SV111 and 112, 1st to 3rd DS
V121 to V123 are ON.
This shows a state in which the upstream oil passage is shut off and the downstream oil passage is drained.

[0049]

[Table 2] As shown in Tables 1 and 2 and FIG. 5, in the third speed, in particular, the first to third DSVs 121 to 123 operate, and as a result, while the forward clutch 51 and the 3-4 clutch 53 are engaged, The 2-4 brake 54 is released. As shown in FIG. 6, in the fourth speed, the third DSV 123 stops generating the operating pressure, and the first SV 111 operates. As a result, the 2-4 brake 54 and the 3-4 clutch 5
3 is engaged, while the forward clutch 51 is released. Here, since the 2-4 brake 54 fixes the sun gear 41 of the second planetary gear mechanism 40 as a transmission gear mechanism and stops its rotation, it does not directly participate in torque transmission. Therefore, in the third speed, both the forward clutch 51 and the 3-4 clutch 53 receive the torque, whereas in the fourth speed of the highest speed, only the 3-4 clutch 53 receives the torque.

As shown in FIG. 7, the automatic transmission 10 includes the first and second SVs 111 and 112 and the first to third DSVs 121 to 112 in the hydraulic control circuit 100.
Control unit 3 for speed change control for controlling 23 and the like
00 is provided.

The control unit 300 includes P
Range switch 301P, R range switch 301R,
N range switch 301N and D range switch 301
D, a signal from the inhibitor switch 301 for detecting the range selected by the shift lever 3;
Signals from the range switch 5, the shift-up switch 7 and the shift-down switch 8, a signal from a vehicle speed sensor 302 for detecting a vehicle speed, a signal from a throttle opening sensor 303 for detecting an engine throttle opening, and an engine speed are detected. From the engine speed sensor 304, a signal from the turbine speed sensor 305 for detecting the turbine speed, a signal from an oil temperature sensor 306 for detecting the temperature of the hydraulic oil, and the like.

Upon receiving these signals, the control unit 300 determines a target shift speed based on the operating state of the shift lever 3 by the driver, the operating condition of the vehicle or the engine, and the like, and the shift speed is realized. Thus, the control signal is output to each of the solenoid valves 111, 112, 121 to 123.

Next, the control operation of the control unit 300 will be specifically described with reference to the flowcharts shown in FIG.

That is, as shown in FIG. 8, the control unit 300 first determines in step S1 whether or not the D range switch 301D is ON. ,
When the R range or the N range is selected and any one of the P range switch 301P, the R range switch 301R, and the N range switch 301N is ON, a separate control corresponding to the selected range is provided in step S2. Run according to the program provided.

On the other hand, when the D range switch 301D is
If N, the M range switch 5 is turned on in step S3
Is determined. That is, since the selected positions of the shift levers 3 in the D range and the M range are set at the same position in the shift direction, depending on the inhibitor switch 301 that detects the position of the shift lever 3 in the shift direction, the D range is selected. Is selected and the M range is selected, the D range switch 301D is turned on and cannot be distinguished. Therefore, when the D range switch 301D is turned on, the M range switch 5 is turned on next.
It is determined whether it is N or not.

Then, the D range switch 301D is turned on.
However, when the M range switch 5 is OFF, that is, when it is determined that the D range has been selected, the shift control in the automatic mode is executed in step S4. On the other hand, when both the D range switch 301D and the M range switch 5 are ON, that is, when it is determined that the M range is selected, the shift control in the manual mode is executed in step S5.

Next, the operation of the shift control in the auto mode in step S4 will be described. As shown in FIG. 9, first, in step S11, the vehicle speed and the throttle opening are detected, and in step S12, A target shift stage G is set based on these detected values and a preset shift map (shift characteristic), and in step S13, each solenoid valve 111 of the hydraulic control circuit 100 is set so that the shift stage G is realized. , 112, 121-123.

Here, in the shift map, as shown in FIG. 10, the first to fourth speed stages are separated by shift-up shift lines U12, U23, U34 and shift-down shift lines D43, D32, D21. That
The speed change vehicle speed represented by each speed change line is provided so as to become higher as the throttle opening increases. Therefore, in this auto mode, a downshift associated with a decrease in vehicle speed as indicated by an arrow a and a downshift associated with depression of an accelerator pedal as indicated by an arrow b automatically occur.

In this case, in particular, the minimum value Va taken when the 4-3 downshift line D43 is fully closed is 4
A single friction element that is engaged at high speed and participates in torque transmission, that is, the minimum vehicle speed as a limit at which the 3-4 clutch 53 can transmit the torque, is set.

Next, the operation of the shift control in the manual mode in step S5 will be described. As shown in FIG. 11, first, in step S21, the shift-up switch 7
Is switched from OFF to ON, and YE is determined.
In the case of S, that is, when the shift lever 3 is operated to the shift-up position Mu in the M range, it is determined in a step S22 whether or not the current target shift speed (current shift speed) G is the fourth speed. Is the first to third speeds in which an upshift other than the fourth speed can be performed, the target shift speed G is set to the one-speed higher speed side in step S23, while step S22 is performed.
When it is determined that the speed G is the fourth speed in which the upshift is impossible, the speed G is not changed and the fourth speed is maintained.

On the other hand, if NO in step S21, the process proceeds to step S24, where the shift-down switch 8
Is switched from OFF to ON, and YE is determined.
In the case of S, that is, when the shift lever 3 is operated to the downshift position Md in the M range, it is determined in step S25 whether or not the current gear G is the first speed.
Is the second to fourth speeds in which downshifting other than the first speed is possible, the target shift speed G is set to the first lower speed side in step S26, and in step S24, the shift speed G is shifted down. When it is determined that the first speed is impossible, the gear G is not changed and the first speed is maintained.

Further, steps S21 and S2
In the determination of 4, even if neither the upshift switch 7 nor the downshift switch 8 is turned on, the gear G is not changed and the current gear is maintained.

Next, the control unit 300
In step S27, in this manual mode,
A base value (V) that is the basis of the vehicle speed (forcible 4-3 downshift vehicle speed) when forcibly executing three downshifts
Read b). Here, as shown in FIG. 12, the base value (Vb) is a value on the higher vehicle speed side than the lowest value Va of the 4-3 downshift line D43 in the automatic mode.

Next, the control unit 300
After detecting the throttle opening and the oil temperature in step S28, in step S29, the base value (Vb) is corrected based on the following equation based on the detected values, so that the final forced 4-3 shift is performed. The down vehicle speed (Vo) is obtained.

[0065]

(Equation 1) Here, K1 is a correction coefficient based on the throttle opening. As shown in FIG. 13, the throttle opening takes a minimum value of 1 when the throttle opening is 0, that is, when the throttle is fully closed, and the value increases as the throttle opening increases. growing. K2 is a correction coefficient based on the oil temperature. As shown in FIG. 14, the correction coefficient K2 takes the minimum value 1 on the high oil temperature side, and increases as the oil temperature decreases. Therefore, as shown in FIG. 12, the final value (Vo) of the forced 4-3 downshift vehicle speed is the base value (V
The value does not become smaller than b), and the value becomes higher on the vehicle speed side as the throttle opening increases and the oil temperature decreases. Further, at this time, the correction coefficients K1, K
Regarding the values of 2 in any combination, the final value (Vo) of the forced 4-3 downshift vehicle speed is not required to be lower than the 4-3 downshift line D43 in the auto mode. Value is set to

Next, the control unit 300
In step S30, the current vehicle speed (V) is detected. In step S31, it is determined whether the current vehicle speed (V) is lower than the forced 4-3 downshift vehicle speed (Vo). Then, as a result, if it is lower, it is once again determined in step S32 whether or not the current gear G is the fourth speed. If it is the fourth speed, the target gear G is changed in step S33. The speed is set to the first low speed side, that is, the third speed.

On the other hand, if the current vehicle speed (V) is not yet lower than the forced 4-3 downshift vehicle speed (Vo) in step S31, or if the current gear G is not the fourth speed in step S32, The shift speed G is not changed in step S33, and the above-described steps S21 to S21 are not performed.
The value set up to 26 is maintained as it is.

Then, the control unit 300
In step S34, a control signal is output to each of the solenoid valves 111, 112, 121 to 123 of the hydraulic control circuit 100 so that the gear stage G set in this way is realized.

Next, the operation of this embodiment will be described.

First, when the D range is selected by the shift lever 3, the shift control in the automatic mode is executed, and as shown in FIG. 10, a shift map in which the vehicle speed and the throttle opening are previously set as parameters is set. The automatic shifting of the gear stage is performed based on this.

In particular, as indicated by an arrow A in FIG. 12, in this auto mode, the vehicle speed decreases in a substantially fully closed state, and when the vehicle speed passes through the 4-3 downshift line D43, that is, when the vehicle speed decreases. The minimum value Va of the line D43
When the vehicle speed becomes lower than the above, an automatic downshift from the fourth speed to the third speed occurs at the time a due to the decrease in the vehicle speed. Thereby, it is fastened at the 4th speed and only participates in torque transmission.
The four clutches 53 transmit the torque well to its limit, and the fuel efficiency is improved and the durability of the 3-4 clutch 53 is ensured.

Further, as shown by an arrow B in FIG. 12, when the accelerator pedal is depressed and the throttle opening increases at a point in time before the shift down due to the decrease in the vehicle speed occurs, the throttle opening Automatic downshift from 4th gear to 3rd gear occurs immediately with the increase in speed. Thereby, the slippage of the 3-4 clutch 53 is avoided, and the durability thereof is ensured.

On the other hand, when the M range is selected by the shift lever 3, the shift control in the manual mode is executed, and the shift speed is switched based on the manual operation of the driver.

In particular, as shown by an arrow A in FIG. 12, in this manual mode, the vehicle speed decreases in a substantially fully closed state, and the vehicle speed becomes lower than the minimum value Va of the 4-3 downshift line D43 in the automatic mode. 4-3 downshifted vehicle speed Vo on the higher vehicle speed side (when both the throttle opening correction coefficient K1 and the oil temperature correction coefficient K2 are 1, Vo =
When the speed falls below Vb), a forced downshift from the fourth speed to the third speed occurs at the time c. Therefore, even if the accelerator pedal is depressed to increase the torque as indicated by the arrow B at a later point in time a, the 3-4 clutch 53 engaged at the fourth speed before the downshift and exclusively participating in the torque transmission is obtained. Has already been released,
A problem that the durability of the (-4) clutch 53 is lost due to slippage does not occur. Also, 3-4 clutch 5
It is no longer necessary to increase the torque capacity of 3-4.
The size of the clutch 53 can be suppressed, and the layout of the automatic transmission 10 and the compactness of the transmission case 11 are maintained.

In FIG. 12, a line L1 indicated by a chain line passing through the time point c or the forced 4-3 downshift vehicle speed Vo (= Vb) is associated with the depression of the accelerator pedal in the manual mode. This conceptually shows that no further downshifting occurs even if the accelerator pedal is depressed as indicated by arrow B after the downshift has not occurred and therefore the forced 4-3 downshift has occurred. .

On the other hand, for example, if the forced 4-3 downshift vehicle speed is set to be the same as the minimum value Va of the 4-3 downshift line D43 in the auto mode, the accelerator pedal is turned as indicated by the arrow B at the time point a. When is depressed, the fourth speed is maintained as it is before the forced 4-3 downshift at the time point a has occurred, and the problems of slipping and durability of the 3-4 clutch 53 cannot be solved. As a result, it is necessary to increase the torque capacity of the 3-4 clutch 53, and the dimensions of the 3-4 clutch 53 are determined by the layout of the automatic transmission 10 or the transmission case 11
Is too large to maintain the compactness of.

Here, FIG. 12 shows a line L 'indicated by a chain line passing through the minimum value Va of the 4-3 downshift line D43 in the time point a or the automatic mode.
Also conceptually indicates the same meaning as the line L1.

Further, the above-mentioned forced 4-3 downshift vehicle speed (Vo) is set to a higher vehicle speed value as the throttle opening becomes larger and the oil temperature becomes lower. As shown in the figure, when the vehicle speed is reduced in a state where the accelerator pedal is depressed and the torque is large, the vehicle speed is reduced to the forced 4-3 shift-down vehicle speed Vo (= Vb: oil temperature correction when fully closed). 4-3 shift down vehicle speed V on the higher vehicle speed side
At the time when the speed drops below o, a forced downshift from the fourth speed to the third speed occurs. Therefore, at the subsequent time point e, arrow D
Even if the accelerator pedal is further depressed to further increase the torque as shown by, no trouble occurs in the 3-4 clutch 53.

As described above, in the state where the torque is originally large, the forced 4-3 downshift is caused early to cover the magnitude of the torque, and the oil temperature is low and the 4-4 downshift occurs.
Even in a state where a response delay of the three-gear shifting operation may occur, the forced 4-3 downshift is also performed earlier to cover the response delay.
Thus, it is possible to effectively realize the durability and the like.

Note that, in FIG. 12, the line L2 indicated by the dashed line passing through the time point d or the forced 4-3 downshift vehicle speed Vo is also the line L1 or the line L '.
This is a conceptual illustration of the same meaning.

In the above embodiment, the correction coefficient K
When the values of K1 and K2 are both 1 or more, the final value (Vo) of the forced 4-3 downshift vehicle speed is its base value (Vb).
It is configured not to be smaller than the above. However, in any combination of the correction coefficients K1 and K2,
As long as the final value (Vo) of the -3 shift down vehicle speed is not required to be lower than the 4-3 shift down shift line D43 in the automatic mode, the values of the correction coefficients K1 and K2 are set to values less than 1. Alternatively, the final value (Vo) of the forced 4-3 downshift vehicle speed may be determined to be smaller than its base value (Vb).

[0082]

As described above, according to the present invention, in the manual mode in which the change of the gear position is basically left to the discretion of the driver, the friction element caused by the increase in the torque due to the depression of the accelerator pedal. Is avoided.

According to the present invention, an automatic mode in which a shift is automatically performed based on a preset shift characteristic and a manual mode in which a shift is performed based on a manual operation of a driver are provided as traveling modes. It can be preferably applied to an automatic transmission.

[Brief description of the drawings]

FIG. 1 is a plan view of a shift lever of a vehicle according to an embodiment of the present invention and a peripheral portion thereof.

FIG. 2 is a plan view showing an arrangement of an M range switch, a shift up switch, and a shift down switch operated by a shift lever.

FIG. 3 is a skeleton diagram showing a mechanical configuration of the automatic transmission.

FIG. 4 is a development view showing a configuration of a peripheral portion of a transmission gear mechanism of the automatic transmission.

FIG. 5 is an enlarged view showing a state of a third speed of a hydraulic control circuit of the automatic transmission.

FIG. 6 is an enlarged view showing a state of the fourth speed.

FIG. 7 is a block diagram showing a shift control system of the automatic transmission.

FIG. 8 is a flowchart showing a main program executed by a control unit of the system.

FIG. 9 is a flowchart showing an operation of a shift control in an auto mode in the main program.

FIG. 10 is a shift characteristic diagram used in a shift control operation in the auto mode.

FIG. 11 is a flowchart showing a shift control operation in a manual mode in the main program.

FIG. 12 is a conceptual diagram showing an operation of a forced downshift in the manual mode.

FIG. 13 is a characteristic diagram used in a shift control operation in the manual mode.

FIG. 14 is also a characteristic diagram.

[Explanation of symbols]

Reference Signs List 3 shift lever 5 M range switch 7 shift up switch 8 shift up switch 10 automatic transmission 51 forward clutch 53 3-4 clutch 54 2-4 brake 300 control unit (forcible shift down means, control means) 302 vehicle speed sensor 303 throttle opening Degree sensor 306 Oil temperature sensor

Claims (4)

[Claims] 1. A control device for an automatic transmission having an automatic mode in which a shift is automatically performed based on a preset shift characteristic and a manual mode in which a shift is performed based on a manual operation of a driver. The shift down vehicle speed in the shift characteristic is set to a higher vehicle speed side as the engine load becomes larger, and the shift down force means forcibly downshifts when the vehicle speed falls below a predetermined vehicle speed in the manual mode. When downshifting from a gear position in which the number of friction elements engaged in torque transmission among the engaged friction elements is small, the predetermined vehicle speed at the time of performing the forced downshift by the forcible shift down means is determined by the above-mentioned shift characteristic. Control means for increasing the vehicle speed relative to the downshift vehicle speed. Control device for dynamic transmission. 2. The minimum value of the downshift vehicle speed in the shift characteristics is set to the lowest vehicle speed at which a friction element that participates in torque transmission at a gear before shifting can transmit torque. 2. The control device for an automatic transmission according to claim 1, wherein a predetermined vehicle speed when the forced downshift is performed is set to be higher than the minimum vehicle speed. 3. 3. The control device for an automatic transmission according to claim 1, wherein the control means increases the predetermined vehicle speed when the forced downshift is performed as the engine load increases. 4. The control device for an automatic transmission according to claim 1, wherein the control means increases the predetermined vehicle speed when the forced downshift is performed as the temperature of the hydraulic oil is lower.