JPS6213539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the shift of an automatic transmission between the highest speed gear, particularly overdrive with a reduction ratio of 1 or less, and other gears.

In automatic transmissions, such gear changes are performed by operating a shift valve like other gear changes, but overdrive, which is set for the purpose of improving fuel efficiency, is more effective if the shift pattern is determined so that it is selected at relatively low vehicle speeds. big. However, in this case, the driving range in overdrive becomes wider, making it difficult to quickly shift from overdrive to the gear immediately below when overtaking or climbing a slope, and the lack of power caused by overdrive impairs drivability.

Therefore, the driver fully depresses the accelerator pedal and enters the downshift state, but in this case, the shift line that determines the shift timing shifts to the higher speed side, so the downshift is performed. , in the gear position selected by this,
Since the accelerator pedal is fully depressed to create a hard down state, it will cause overpower when accelerating slowly or climbing a slope, resulting in poor fuel efficiency.
There is also the danger of sudden acceleration.

Therefore, this type of automatic transmission is usually provided with a maximum speed gear release means that is activated by a manual switch operated by the driver, so that the highest speed gear can be released as appropriate. I'm being teased. However, in this case, the switch must be operated by the driver, and this operation can be very troublesome even when the vehicle is driving.

The present invention includes an engine load sensor and an engine load change rate detection circuit that processes a signal from the sensor to determine the rate of change in engine load, and detects when the rate of increase in engine load exceeds a set value according to the signal from the circuit. By activating the highest speed gear release means to release the highest speed gear, a predetermined downshift can be carried out without the need for a kickdown state during slow acceleration or gentle hill climbing when the engine load increase speed exceeds a set value. This not only prevents deterioration of fuel efficiency, but also eliminates the danger of sudden acceleration.Also, the driver can automatically obtain the downshift without having to operate a switch, which eliminates the inconvenience and eliminates the risk of sudden acceleration. From the perspective of solving the problem all at once, if the operation of the highest gear release means is stopped when the engine load falls below a predetermined value, the duration of the highest gear release will meet the requirements. In addition, after slow acceleration or climbing a hill, the highest gear can be reselected by simply releasing the accelerator pedal or stepping on the brake pedal.
A shift control device for an automatic transmission characterized by the above configuration is proposed here from the viewpoint that fuel efficiency can be improved without increasing operational complexity.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 schematically shows the power transmission part in an automatic transmission with four forward speeds (the fourth speed is overdrive) and one reverse speed, which is to be controlled by the device of the present invention. Torque converter 1, input shaft 7, direct clutch 185, OD band brake 186, OD planetary gear group 187, intermediate shaft 188, front clutch 104, rear clutch 105, second brake 106, low reverse brake 107 , one-way brake 108, intermediate shaft 109, first planetary gear group 1
10, a second planetary gear group 111, an output shaft 112, a first governor valve 113, a second governor valve 114, and an oil pump 13. The torque converter 1 consists of a pump impeller 3, a turbine impeller 8, and a stator impeller 9. The pump impeller 3 is driven by a crankshaft 4 and rotates the torque converter hydraulic oil contained therein to the input shaft 7. Turbine wheel 8 fixed to
gives torque to. The torque is further transmitted by the input shaft 7 to the transmission gear train. The stator wheel 9 is placed on the sleeve 12 via a one-way clutch 10. One way clutch 10
The structure allows the stator wheel 9 to rotate in the same direction as the crankshaft 4, that is, in the direction of the arrow (hereinafter referred to as normal rotation), but does not allow rotation in the opposite direction (hereinafter referred to as reverse rotation).

Input shaft 7 is OD planetary gear group 187
is connected to the planetary gear support 192 of. Planetary gear 1
89 rotates and revolves simultaneously with the internal gear 190 and the sun gear 191, respectively. The internal gear 190 is connected to the first planetary gear group 110 by an intermediate shaft 188. OD band brake 18
6 is for fixing or releasing the sun gear 191.

The first planetary gear group 110 includes an internal gear 117 fixed to an intermediate shaft 188, and a hollow conduction shaft 1.
Sun gear 119 fixed to 18, internal gear 11
7 and the sun gear 119, a planetary gear 120 consisting of two or more small gears that can rotate simultaneously and revolve at the same time, and an output shaft 1.
The second planetary gear group 1 is composed of a planetary gear support 121 that is fixed to the second planetary gear group 12 and supports the planetary gear 120.
Reference numeral 11 denotes an internal gear 122 fixed to the output shaft 112, a sun gear 123 fixed to the hollow conduction shaft 118, two or more gears that can rotate and revolve simultaneously while meshing with each of the internal gear 122 and the sun gear 123. It is composed of a planetary gear 124 made of a small gear, and a planetary gear support 125 that supports the planetary gear 124. A front clutch 104 connects an intermediate shaft 188 driven by an internal gear 190 and a hollow transmission shaft 118 that rotates in unison with both sun gears 119, 123, and a rear clutch 105 connects an intermediate shaft 188 and Internal gear 117 of 1 planetary gear group 110
It functions to combine. Second brake 1
06 serves to fix both sun gears 119 and 123 by fixing the hollow conduction shaft 118, and the low reverse brake 107 serves to fix the planetary gear support 125 of the second planetary gear group 111. The one-way brake 108 is the planetary gear support 1
25 has a structure that allows forward rotation but does not allow reverse rotation. A first governor valve 113 and a second governor valve 114 are fixed to the output shaft 112 and generate governor pressure according to vehicle speed.

Next, a description will be given of the power transmission train when the speed selection rod is set to the D (forward automatic shifting) position.

In this case, the direct clutch 185, which is a forward input clutch, and the rear clutch 105 are first engaged. Power from the engine via the torque converter 1 is transmitted from the input shaft 7 to the planetary gear support 192, and since the direct clutch 185 is engaged, the power is transmitted to the planetary gear group 187.
The whole is interlocked and transmits the same rotation as the input shaft 7 to the intermediate shaft 188, which then passes through the rear clutch 105 to the first
The signal is transmitted to the internal gear 117 of the planetary gear group 110. The internal gear 117 rotates the planetary gear 120 in the normal direction. Therefore, the sun gear 119 is reversed and the sun gear 1
The second planetary gear group 11 rotates together with 19.
In order to reverse the first sun gear 123, the planetary gears 124 of the second planetary gear group 111 rotate in the normal direction. One-way brake 108 prevents sun gear 123 from reversing planetary gear support 125 and acts as a forward reaction brake. Therefore, the second planetary gear group 111
The internal gear 122 rotates normally. Therefore, internal gear 1
Output shaft 112 that rotates integrally with 22
The motor also rotates in the normal direction, and the reduction ratio of the first forward speed is obtained. In this state, the vehicle speed increases and the second brake 1
When 06 is engaged, the power from the input shaft 7 is transmitted to the internal gear 117 via the interlocked OD planetary gear group 187 and the rear clutch 105. Second brake 106 prevents rotation of sun gear 119 and acts as a forward reaction brake. Therefore, the planetary gear 120 moves around the stationary sun gear 119.
revolves around its axis, and therefore the planetary gear support 1
Although the output shaft 112 and the output shaft 112 integrated therewith are decelerated, they rotate normally at a faster speed than in the first speed, and the reduction ratio of the second forward speed is obtained. The vehicle speed further increases, the second brake 106 is released, and the front clutch 104
When the input shaft 7 is engaged, the power transmitted to the input shaft 7 is transmitted to the internal gear 117 via the rear clutch 105 via the planetary gear group 187, and to the sun gear 119 via the front clutch 104 on the other hand. communicated. Therefore, the internal gear 11
7. Sun gear 119 is interlocked, planetary gear support 121 and output shaft 1
12, all rotate forward at the same rotation speed and move forward No. 3
You can get speed. In this case, the input clutches are the front clutch 104 and the rear clutch 105, and since torque is not increased by the planetary gear, there is no reaction brake.

Next, when the vehicle speed increases further, the direct clutch 185 is released and the OD band brake 186 is engaged. When the OD band brake 186 is engaged, the sun gear 191 is fixed. Therefore, the rotation of the input shaft 7 causes the internal gear 190 to rotate at an increased speed in the forward rotation direction by the planetary gear 189, and is transmitted from the intermediate shaft 188 to the rear clutch 105 and the front clutch 104, thereby obtaining a fourth speed overdrive. .

Next, the power transmission train when the speed selection rod is set to the R (reverse travel) position will be explained. In this case, the direct clutch 185, front clutch 104, and low reverse brake 107 are engaged.
The power that passes from the engine through the torque converter 1 is
Direct clutch 1 from input shaft 7
Planetary gear group 1 interlocked by tightening 85
87 to the front clutch 104, and the hollow transmission shaft 118 to the sun gears 119, 12.
I am guided by 3. At this time, the rear planet carrier 125 is the low reverse brake 107.
Since it is fixed by the sun gear 119,
The internal gear 122 is decelerated and reversed by the normal rotation of the internal gear 123, and a reverse reduction ratio is obtained from the output shaft 112 that rotates integrally with this internal gear.

Figure 2 shows the hydraulic system of the speed change control device related to the above-mentioned automatic transmission.
3, line pressure adjustment valve 128, pressure increase valve 129, torque converter 1, speed selection valve 130, first governor valve 113, second governor valve 114, 1-2 shift valve 131, 2-3 shift valve 132, 3- OD shift valve 133, OD release valve 197, throttle pressure reducing valve 133, cut-down valve 134, second
Lock valve 135, 2-3 timing valve 136, solenoid down shift valve 137, throttle back up valve 138, vacuum throttle valve 139, vacuum diaphragm 14
0, front clutch 104, rear clutch 1
05, second brake 106, servo 14
1. Low reverse brake 107, direct clutch 185, OD band brake 186,
Servo 186a, accumulator 200, OD
It consists of a release solenoid 198 and hydraulic circuitry.
The oil pump 13 is driven by the prime mover via the drive shaft 4 and the pump wheel 3 of the torque converter 1, and is always in the reservoir 142 during engine operation.
The oil from which harmful dust has been removed is sucked up through a strainer 143 and sent to a line pressure circuit 144.

The oil is regulated to a predetermined pressure by the line pressure regulating valve 128 and sent to the speed selection valve 130 as working oil pressure. The line pressure regulating valve 128 consists of a spool 172 and a spring 173.
73, the throttle pressure of the circuit 165 and the line pressure of the circuit 156 act through the spool 174 of the pressure increase valve 129, and the force generated by these acts on the line pressure acting from the circuit 144 through the orifice 175 above the spool 172. and circuit 17
It resists the pressure acting from 6. The working oil pressure of the torque converter 1 is determined by the hydraulic oil outflow passage 51 and the pressure holding valve after the oil introduced into the circuit 145 from the circuit 144 via the line pressure regulating valve 128 flows into the torque converter 1 through the hydraulic oil inflow passage 50. 146, the pressure is maintained within a certain pressure by a pressure holding valve 146. Above a certain pressure, the pressure holding valve 146 is opened and the oil flows further into the circuit 14.
7 to the rear lubrication section of the power transmission mechanism. When this lubricating oil pressure is too high, the relief valve 148 opens and the pressure is lowered. On the other hand, lubricating oil is supplied from the circuit 145 to the front lubricating section of the power transmission mechanism by opening the front lubricating valve 149. The speed selection valve 130 is a manually operated fluid direction switching valve, and is composed of a spool 150, which is connected to a speed selection rod (not shown) via a linkage, and the spool 150 is changed depending on each speed selection operation by the driver. It moves to switch the pressure feeding passage of the line pressure circuit 144. The condition shown in FIG. 2 is the N (neutral) position, where the line pressure circuit 144 is closed by the land of the spool 150 and ports a-f all communicate with the drain port. The first governor valve 113 and the second governor valve 114 actuate the 1-2 shift valve 131 and the 2-3 shift valve 132 using the governor pressure generated during forward travel to perform automatic gear shifting, and also control line pressure. The speed selection valve 130 is controlled by D,
When the vehicle is in the forward traveling position of or, the hydraulic pressure reaches the second governor valve 114 from the line pressure circuit 144 through port c of the speed selection valve 130, and when the vehicle is traveling, the pressure is regulated by the second governor valve 114. The governor pressure is sent to the circuit 157 and the first governor valve 1
13, and when the vehicle speed reaches a certain speed, the spool 177 of the first governor valve 113 moves and the circuit 157
is connected to the circuit 158 to generate governor pressure, and the governor pressure from the circuit 158 is transferred to the 1-2 shift valve 131,
2-3 shift valve 132, 3-OD shift valve 133
and acting on each end face of the cut-down valve 134,
Each of these valves is counterbalanced by a respective spring 159, 163, 133 _S , 134 _S pressing it to the right. Also, from port c of speed selection valve 130 to circuit 1
53, a servo 141 that tightens the second brake 106 via circuit 161 and circuit 162;
A 1-2 shift valve 131 and a second lock valve 13 are installed in the middle of the hydraulic circuit reaching the engagement side hydraulic chamber 169.
5 are provided in sequence, and further a circuit 152 is provided which reaches the second lock valve 135 from the boat b of the speed selection valve 130.

Therefore, when the speed selection rod is set to the D position, the spool 150 of the speed selection valve 130 moves and the line pressure circuit 1
44 leads to ports a, b, and c. The hydraulic pressure passes through the circuit 151 from port a, and part of it acts on the lower part of the second lock valve 135, and the spring 17
Spool 178 being pressed upward by 9
is not lowered by the hydraulic pressure acting from port b through circuit 152, and circuit 1
61 and 162 are not blocked. A portion of the hydraulic pressure from port a passes through the orifice 166 and reaches the 2-3 shift valve 132 from the circuit 167.
Hydraulic pressure from port c passes through circuit 153 to second governor valve 114, rear clutch 105 and 1-
2 shift valve 131 and the second governor valve 114
The rear clutch 105 is engaged to enable the 1-2 shift valve 131 to perform the operation described below.

On the other hand, the line pressure of the line pressure circuit 144 is 3-
The oil passage 193 reaches the OD release valve 197 via the OD shift valve 133, and the oil passage 194 reaches the direct clutch 185 and engages it. Together with the engagement of the rear clutch 105, the transmission shifts to the first forward speed. become a state. In this state, when the vehicle speed reaches a certain speed, the 1-2 shift valve 131 moves the spool 160, which is pressed to the right by the spring 159, to the left by the governor pressure of the circuit 158, and moves forward as shown below. An automatic shift action from the first speed to the second speed is performed. That is, at this time, the 1-2 shift valve 131 conducts the circuit 153 and the circuit 161, and the circuit 15
Hydraulic pressure from 3,161 is the second lock valve 13
5, the circuit 162 reaches the engagement side hydraulic chamber 169 of the servo 141, which engages the second brake 106. Together with the engagement of the direct clutch 185 and rear clutch 105, the transmission shifts to the second forward position.
Be in a state of speed. In this case, the 1-2 shift valve 13
1 is compact, the spool 160 moves to the left at the required speed without increasing the speed at the shift point, and an automatic shift action from forward first speed to second speed is performed. When the vehicle speed increases further and reaches a certain speed, the governor pressure of the circuit 158 overcomes the spring 163 and becomes 2-
3 Press the spool 164 of the shift valve 132 to the left to connect the circuit 167 and the circuit 168 so that the hydraulic pressure is partially transferred from the circuit 168 to the release side hydraulic chamber 1 of the servo 141.
70, the second brake 106 is released, a portion reaches the front clutch 104 and engages it, and together with the engagement of the direct clutch 185 and rear clutch 105, the transmission is in the third forward speed. become.

Next, when the vehicle speed increases further and reaches a certain speed, the governor pressure of the circuit 158 overcomes the spring _133S and
- In order to push the spool 133a of the OD shift valve 133 to the left, the oil pressure of the line pressure circuit 144 is stopped from being output to the oil path 193, and at the same time, the oil pressure of the line pressure circuit 144 is stopped from being output to the oil path 193.
93 communicates with the drain port 133d, so that the hydraulic pressure acting on the release side servo chamber _186R of the direct clutch 185 and OD band brake 186 passes from the oil passages 194 and 195 through the OD release valve 197 and through the oil passage 193. - Oil is drained from the drain port 133d of the OD shift valve 133.
This causes the direct clutch 185 to release,
The OD band brake 186 is engaged by the line pressure supplied from the line pressure circuit 144 to the engagement side hydraulic chamber of the servo 186a via the oil path 201, resulting in an overdrive state (fourth speed).

If the driver depresses the accelerator pedal until the throttle opening is close to full throttle while driving in position D, a solenoid switch (not shown) is turned on and the solenoid
A down shift solenoid 137c disposed opposite to the down shift valve 137 is energized by energization. As a result, the spool 137a of the solenoid downshift valve 137 is pushed downward by the spring 137b from the upwardly locked position in FIG. At this time, the kickdown circuit 180 that was connected to the circuit 154 is connected to the line pressure circuit 144, and the line pressure is passed through the circuits 144 and 180 to the 1-2 shift valve 131, the 2-3 shift valve 132, and the 3-OD shift valve 133. Supplied opposite the governor pressure. At this time, if you are running in overdrive, first spool 1 of 3-OD shift valve 133.
33a is forcibly pushed from the leftward position to the rightward position by the line pressure against the governor pressure, and a downshift from the overdrive state to third speed is forcibly performed within a certain vehicle speed limit.

Next, when the above-mentioned kick-down is performed while driving in third gear, the spool 164 of the 2-3 shift valve 132 is forced by the line pressure from the leftward position to the rightward position against the governor pressure. This will force a downshift from 3rd gear to 2nd gear within a certain vehicle speed limit and provide sufficient acceleration. Furthermore, if the above-mentioned kickdown is performed while running in second gear, the load is large and the speed is low at this time, so the governor pressure is also low, so the line pressure led to the circuit 180 is 1.
-2 The spool 160 of the shift valve 131 is also moved from the leftward position to the right against the governor pressure. Therefore, in this case, a forced downshift from second speed to first speed is performed, and a stronger acceleration force corresponding to a large load can be obtained.

When the speed selection rod is set to the (second forward speed fixed) position, the spool 150 of the speed selection valve 130 moves and the line pressure circuit 144 communicates with ports b, c, and d.
Oil pressure reaches the same location from ports b and c as in case D, engaging the rear clutch 105, while the lower part of the second lock valve 135 reaches the spool 178 because there is no oil pressure in this position.
The areas of the lands above and below the part that opens to the circuit 152 and where hydraulic pressure acts are larger at the bottom, so the second
The spool 178 of the lock valve 135 is pushed down against the force of the spring 179, and the circuits 152 and 162 are brought into conduction, and the hydraulic pressure reaches the engagement side hydraulic chamber 169 of the servo 141, engaging the second brake 106, and shifting. The aircraft is in second forward speed. From port d, oil pressure passes through circuit 154 to solenoid down shift valve 137 and throttle back up valve 138. There is a disconnection between port a of the speed selection valve 130 and the line pressure circuit 144, and the hydraulic pressure does not reach the 2-3 shift valve 132 from the circuit 151, so the second brake 106
Since the front clutch 104 is not released and the front clutch 104 is engaged, the transmission is not in the third forward speed. Therefore, the second lock valve 135 is the speed selection valve 1.
Together with 30, it functions to fix the transmission in the second forward speed state. When the speed selection rod is set to the (first forward speed fixed) position, the line pressure circuit 144 communicates with ports c, d, and e. Hydraulic pressure reaches the same location from ports c and d and engages rear clutch 105, and from port e it reaches the same location as in circuit 15.
5 to the circuit 171 via the 1-2 shift valve 131.
From there, a portion reaches the low reverse brake 107, which engages the low reverse brake 107, which acts as a forward reaction brake, and shifts the transmission to the forward first position.
A portion reaches the left side of the 1-2 shift valve 131 and acts together with the spring 159 to press the spool 160 to the right, thus fixing the first forward speed.

The OD release device consisting of an OD release valve 197 and an OD release solenoid 198 is for forcibly releasing the overdrive state while driving in the overdrive state, and this release is controlled by the circuit shown in Figure 3. do. This circuit includes a manual switch 68 connected to the power supply +V, which is manually closed when the driver wishes to release overdrive and does not wish to shift into overdrive. At this time, the switch 68 is connected to the power supply +V.
voltage, that is, an H level signal, is supplied to the driver 67, and thereby the driver 67 operates to energize the OD release solenoid 168. Because of this,
The plunger _198P of the OD release solenoid 198, which is normally in the retracted position shown in FIG.
44, line pressure is supplied to the left end of the OD release valve 197 in FIG. 2 via the oil passage 201 and the orifice 196a. This line pressure pushes the spool _197S against the spring 199, and in the overdrive state, the oil passage 197 S leading to the drain is pushed as described above.
3 is shut off, and the oil passage 194 is made to communicate with the oil passage 201. As a result, line pressure from the oil passage 201 is output to oil passages 194 and 195, which engages the direct clutch 185 and releases the OD band brake 186, forcing the automatic transmission to overdrive as desired by the driver. The transmission is automatically released and the gear is forcibly downshifted to the third gear selection state, or a shift up from the third gear to overdrive is prevented.

The circuit shown in FIG. 3 also includes a vehicle speed sensor 64 and a throttle sensor 66 as an engine load sensor.
The vehicle speed sensor 64 outputs a vehicle speed signal V corresponding to the vehicle speed, and the throttle sensor 66 outputs an engine load signal TH corresponding to the throttle opening.
It is input to the prohibition determination circuit 60. The vehicle speed signal V is a pulse signal that repeats H level and L level every fixed travel distance, has a pulse width corresponding to the vehicle speed, and is input to the binary counter 61. The counter 61 counts the number of pulses of the vehicle speed signal V in binary form within a fixed time period determined by the timer T, and holds the count value (corresponding to the vehicle speed) S _V for each fixed time period until the next count is completed.
Output to comparator 62. Engine load signal TH is
The input signal is input to the A/D converter 63, and this A/D converter stores the engine load signal (binary signal) S〓 corresponding to the current throttle opening for each of the eight throttle opening divisions, for example, into the set value memory 65. Output to. The memory 65 is, for example, a read-only memory (ROM), and is addressed by the signal S, and is determined by, for example, the 3-OD shift valve 133 (see FIG. 2) indicated by the dotted line A'-B'-B in FIG. The vehicle speed setting value corresponding to the current throttle opening classification is read from the 3→OD shift line defined as the solid line A-B in the figure, and the corresponding signal S _n
is output to the comparator 62.

The comparator 62 outputs a count value S corresponding to the current vehicle speed.
_V and the set value S _n are compared, and when S _V <S _n , the OD control signal S _OD which is the output signal is set to H level, and when S _V >
When S _n, the signal S _OD is set to L level, and this signal is ORed.
Supplied to gate 69. When the signal _SOD becomes H level, this signal is supplied to the driver 67 via the OR gate 69, and as a result of operating this, the automatic transmission is released from overdrive by the same effect as when the switch 68 is closed. When shifting only using the 3-OD shift valve 133, the third speed is selected in the shaded area in FIG. 4, which is the overdrive area, and drivability can be improved.

In the present invention, a differentiation circuit 70 as an engine load change rate detection circuit is added to the control circuit shown in FIG. 3, and the engine load signal TH from the throttle sensor 66 is inputted to this differentiation circuit 70. The differentiating circuit 70 is a signal
The rate of change in engine load is determined by differentiating TH with respect to time, and a signal _THV corresponding to this is supplied to the comparator 71. The comparator 71 compares the engine load change rate signal _THV from the differentiating circuit 70 with a set value, and when the signal _THV is larger than the set value, it supplies an H level judgment signal TH _J to the set terminal S of the flip-flop circuit 72. .

A comparator 73 is connected to the reset terminal of the flip-flop circuit 72, and this comparator detects the throttle opening from the throttle signal TH from the throttle sensor 66 while the throttle opening is equal to or greater than a value corresponding to, for example, 1/8 opening near the fully closed position. An H level signal is supplied to the reset terminal of the flip-flop circuit 72, and when the throttle opening becomes less than that and reaches a value corresponding to fully closed, the signal is switched to L level. The flip-flop circuit 72 outputs a signal TH _J to the set terminal S.
When Q rises, this sets the output terminal Q.
The higher level OD control signal TH _OD is sent to OR gate 6.
9, and when the signal to the reset terminal falls, it is set and the output signal from terminal Q
Assume that TH _OD shifts to L level.

A signal from the differentiator circuit 70 indicating the engine load increase rate by relatively rapid depression of the accelerator pedal.
When TH _V exceeds the set value, the comparator 71 changes the determination signal TH _J to H level. A flip-flop circuit 7 receives such a signal at a set terminal S.
2 is reset by the rise of the signal _THJ , and makes the output signal _THOD from the terminal Q go to H level. This H level signal TH _OD passes through the OR gate 69 and operates the driver 67, as described above.
By operating the OD release solenoid 198, overdrive can be released and the automatic transmission can be forcibly downshifted to third gear.

This forced downshift continues unless the accelerator pedal is released and the comparator 73 resets the flip-flop circuit by supplying a throttle opening fully closed signal (L level) to the reset terminal of the flip-flop circuit 72. The time flip-flop circuit 72 outputs its output signal
By changing TH _OD to L level, the above-described control can be performed according to the OD determination signal S _OD .

Thus, as described above, the speed change control device of the present invention includes the engine load sensor 66 and the engine load change rate detection circuit 70 that processes the signal TH to determine the rate of change of the engine load, and receives the signal TH _V from the circuit. Accordingly, when the engine load increase speed is equal to or higher than the set value, the highest speed gear release means 198 is activated to release the highest speed gear (overdrive in the illustrated example), so that the engine load increase speed is higher than the set value. When accelerating and climbing slopes as described above, a predetermined forced downshift can be obtained without having to enter the kick-down state and wait for the downshift by the operation of the solenoid downshift valve 137 described above, which is unnecessary during slow acceleration or gradual slope climbing. This eliminates the need to fully depress the accelerator pedal for the purpose of downshifting, which prevents deterioration of fuel efficiency and the risk of sudden acceleration due to overpower. In addition, since this forced downshift can be performed automatically, the driver does not have to manually switch 68 to obtain such control as in the past.
It has various features such as eliminating the need to close the door, eliminating the hassle of operation, and improving drivability.

In addition, since the operation of the highest speed gear release means is configured to stop when the engine load falls below a predetermined value, all that is required is to release the accelerator pedal after gentle acceleration or climbing a hill, or to press the brake pedal during deceleration. The highest speed gear can be selected,
Good fuel efficiency can be achieved without increasing operational complexity.

In addition, the control to stop the operation of the highest speed gear release means prevents the highest gear from being inadvertently reselected while the means is required to operate, thereby ensuring that the highest speed gear is released. Can be continued.

[Brief explanation of the drawing]

Fig. 1 is a skeleton diagram showing the power transmission part of an automatic transmission to which the transmission control device of the present invention is applied, Fig. 2 is a shift control hydraulic circuit diagram of the automatic transmission, and Fig. 3 is a shift control of the present invention. electronic circuit diagram of the device;
Figure 4 is a 3→OD shift diagram using the same device. 66...Engine load sensor, 67...Driver,
69...OR gate, 70...Engine load change rate detection circuit, 71...Comparator, 72...Flip-flop circuit, 73...Comparator, 133...3-OD shift valve, 185...Direct clutch, 186...OD
Band brake, 197...OD release valve, 198...
OD release solenoid.

Claims (1)

[Claims] 1. In an automatic transmission that is capable of shifting between the highest gear and other gears using a shift valve, and is equipped with a highest gear release means that prevents shifting to the highest gear as appropriate, the engine load sensor and an engine load change rate detection circuit that processes future signals to determine the rate of change in engine load, and when the engine load increase rate exceeds a set value based on the signal from the circuit, the highest speed shift stage is selected. A means is provided for activating a release means to release the highest speed gear, and stopping the operation of the highest speed gear release means when the engine load becomes less than a predetermined value based on a signal from the engine load sensor. Characteristics of the automatic transmission shift control device.