JPS6011265B2 - automatic transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic transmission, and more particularly to a hydraulically controlled variable speed shifter that controls gear shifting by appropriately supplying hydraulic pressure to friction elements that determine a power transmission path through hydraulic actuation of various valves. This relates to transmissions.

When driving downhill with a hydraulically controlled variable transmission with its manual valve in the automatic gearbox range, the furthest gear remains selected, and engine braking is hardly expected, especially when driving long distances on steep slopes. In order to avoid using the foot brake frequently when going downhill, the driver should set the manual valve from the D range to the 2 far fixed range or 1 far fixed range, and then manually operate the manual valve as described above each time so that the engine brake is effective. It is necessary to do it. Therefore, in order to eliminate this complication, conventionally, when an operation representative of the above-mentioned driving condition is performed, i.e., when the foot is removed from the accelerator pedal and the brake pedal is pressed down, the system is automatically activated even if the vehicle remains in D range. and a hydraulically controlled eye that is devised to operate at least one valve selected from the above-mentioned various valves, usually a downshift valve, so as to downshift from the highest gear to the immediately preceding lower gear. A flat gearbox was proposed.

The downshift valve is an existing one that is actuated by a downshift solenoid that is energized when the accelerator pedal is depressed to the maximum, and forcibly downshifts from a selected gear to a lower gear. However, in such a hydraulically controlled variable transmission, the downshift is performed every time the brake pedal is stepped on to brake the vehicle, even when the vehicle is running and does not actually require engine braking.
The reality is that passengers feel an unpleasant sense of deceleration every time they brake, which significantly impairs the driving feeling. From this point of view, the present invention is applicable only when the vehicle is running in a driving state where the acceleration exceeds a set value and when the driver takes his foot off the accelerator pedal and depresses the brake pedal, that is, when driving downhill where engine braking is really required. This hydraulically controlled variable transmission has been improved so that only when the downshift solenoid is energized, a forcible downshift can be automatically performed and engine braking can be applied appropriately.

The present invention will be described in detail below based on the illustrated embodiments.
Fig. 1 shows a normal power transmission system in an automatic transmission with three forward, one far and one reverse, and this power transmission system generally consists of a torque converter that receives power from the engine's crankshaft 4, an input shaft 7, a front clutch. 1
04, rear clutch 105, second brake 10
6, low reverse brake 107, one-way brake 108, intermediate shaft 109, first planetary gear group 110,
second planetary gear group 111, output shaft 112,
It is composed of a first governor valve 113, a second governor valve 114, and an oil pump 13.

The torque converter 1 consists of a pump impeller P, a turbine impeller T, and a stator impeller S. The pump impeller P is driven by a crankshaft 4 and rotates the torque converter hydraulic oil contained therein through an input shaft 7. Torque is applied to the turbine wheel T fixed to the The torque is further transmitted by the input shaft 7 to the transmission gear train. The stator wheel S is placed on a fixed sleeve 12 via a one-way clutch 10. The one-way clutch 10 has a structure that allows the stator wheel S to rotate in the same direction as the crankshaft 4, that is, in the direction of the arrow (hereinafter referred to as forward rotation), but does not allow rotation in the opposite direction (hereinafter referred to as reverse rotation). ing. The first planetary gear group 110 is the intermediate shaft 10
Internal gear 117 fixed to 9, hollow transmission shaft 11
A planetary gear 120 consisting of two or more small gears that can rotate and revolve simultaneously while meshing with each of the sun gear 119, internal gear 117, and sun gear 119 fixed to the sun gear 119.
, the planetary gear 12 is fixed to the output shaft 112.
The second planetary gear group 111 includes an internal gear 122 fixed to the output shaft 112, a sun gear 123 fixed to the hollow transmission shaft 118, an internal gear 122, and It is composed of a planetary gear 124 made up of two or more small gears that can rotate and revolve at the same time while meshing with each of the sun gears 123, and a planetary gear support 125 that supports the planetary gears 124. The front clutch 104 is connected to an input shaft 7 driven by a turbine wheel T and both sun gears 119.
, 123, the hollow conduction shaft 11 rotates integrally with the
8 through a drum 126, and the rear clutch 1
06 serves to connect the input shaft 7 and the internal gear 117 of the first planetary gear group 110 via the intermediate shaft 109. The second brake 106 fixes both sun gears 119 and 123 by winding and tightening a drum 126 fixed to a hollow transmission shaft 118, and the low reverse brake 107 fixes both sun gears 119 and 123.
It functions to fix the planetary gear support 125 of. On the other hand, the brake 108 has a structure that allows the planetary gear support 125 to rotate in the normal direction, but not in the reverse direction. First governor valve 1
13 and a second governor valve 114 are fixed to the output shaft 112 and generate a governor pressure depending on the vehicle distance. Next, the power transmission train when the speed selection lever is set to the D (forward automatic shifting) position will be explained. In this case, only the IJ clutch 105, which is the forward input clutch, is initially engaged.

Power from the engine via the torque converter 1 is transmitted from the input shaft 7 to the internal gear 117 of the first planetary gear group 110 via the rear clutch 105. The internal gear 117 rotates the planetary gear 120 in the normal direction. Therefore, the sun gear 119 rotates in the reverse direction, and the planet gears 124 of the second planetary gear group 111 rotate in the normal direction to reverse the sun gear 123 of the second planetary gear group 111, which rotates integrally with the sun gear 119. One-way brake 108 prevents sun gear 123 from reversing planetary gear support 125 and acts as a forward reaction brake. Therefore, the internal gear 122 of the second planetary gear group 111 rotates normally. Therefore, the output shaft 112, which rotates integrally with the internal gear 122, also rotates in the normal direction, and a forward first and farthest reduction ratio is obtained. In this state, when the vehicle is raised and the second brake 106 is engaged, the rear clutch 1 is transferred from the input shaft 7 as in the case of the first brake.
The power passing through 05 is transmitted to the internal gear 117. The second brake 106 fixes the drum 126, prevents rotation of the sun gear 119, and acts as a forward reaction brake.
Therefore, the planetary gear 1 moves around the stationary sun gear 119.
20 revolves around its axis, and therefore the planetary gear support 12
Although the output shaft 112 and the output shaft 112 integrated therewith are decelerated, they rotate forward at a faster speed than in the case of the first far, and the forward speed reduction ratio of the second far is obtained. When the vehicle speed increases further and the second brake 106 is released and the front clutch 104 is engaged, the power transmitted to the input shaft 7 is transferred to the rear clutch 105.
The signal is transmitted to the internal gear 117 via the front clutch 104, and to the sun gear 119 via the front clutch 104. Therefore, the internal gear 117 and the sun gear 119 are interlocked, and the planetary gear support 121 and the output shaft 1
Together with 12, they all rotate forward at the same rotational speed to obtain the forward third distance. In this case, the input clutches are the front clutch 104 and the rear clutch 105,
There is no reaction brake because torque is not increased by planetary gears. Next, the power transmission train when the select lever is set to the R (reverse travel) position will be described. In this case, "Front clutch 104 and low reverse brake 1
07 is concluded.

The power from the engine passes through the torque converter 1 and is transferred from the input shaft 7 to the front clutch lo4,
It passes through drum 126 and is guided to sun gears 119, 123. At this time, the rear planetary gear support 125 is
Because it is fixed by reverse brake 107,
When the sun gear 119'123 rotates normally, the internal gear 12
2 is decelerated and reversed, and the output shaft 112, which rotates integrally with this internal gear 122, is also reversed to obtain a backward reduction ratio. FIG. 2 shows a hydraulic control system in which switching of the power transmission train is carried out by hydraulic control, including an oil pump 13 and a line pressure regulating 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, throttle pressure reducing valve 133, cut-down valve 134, second cock valve 135, 2-3 timing valve 136, solenoid down shift valve 137, throttle back up valve 138, vacuum throttle valve 139, vacuum diaphragm 140, front clutch 104,
It consists of a rear clutch 105, a second brake 106, a servo 141, a low reverse brake 107, and a hydraulic circuit network. The oil pump 13 is driven by the engine via the crankshaft 4 and the pump impeller P of the torque converter 1, and while the engine is running, the oil pump 13 always sucks oil from a reservoir 142 through a strainer 143, from which harmful debris has been removed, to the line pressure circuit. Send to. The oil is regulated to a predetermined pressure by the line pressure regulating valve 128 and used as the working hydraulic pressure for the torque converter 1 and the speed selection valve 130.
sent to. The line pressure regulating valve 128 consists of a spool 172 and a spring 173, and the spool 172 is connected to a circuit 16 via a spool 174 of a pressure increase valve 129 in addition to the spring 173.
5 throttle pressure and the line pressure of the circuit 156 act, and the orifice 175 is moved from the circuit 144 to the upper part of the spool 172.
line pressure acting through and pressure acting from circuit 176. Hydraulic oil to torque converter 1 is supplied from circuit 144 to circuit 1 via line pressure regulating valve 128.
45, and after flowing through the torque converter 1, the pressure is maintained within a certain pressure by a pressure holding valve 1146. Above a certain pressure, the pressure holding valve 146 is opened and oil is sent further from the circuit 147 to the rear lubrication section of the drive train. 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 fluid direction switching valve that is switched by manual operation of a speed selection lever (not shown), and is composed of a spool 150 that is linked to the speed selection valve.
The speed is selected via a linkage to a speed selection lever (not shown), and each speed selection operation moves the spool 150 to control the line pressure circuit 1.
44 pressure feeding passages. The state shown in FIG. 2 is when the speed selector valve 130 is in the N (neutral) position and the line pressure circuit 144 is open to boats d and c. 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. When the speed selection valve 130 is in the D, B, and 1 layers, the oil pressure reaches the second governor valve 114' from the line pressure circuit 144 through the boat c of the speed selection valve 130, and the car starts running. Then, the governor pressure proportional to the vehicle speed regulated by the second governor valve 114 is sent to the circuit 157 and introduced into the first governor valve 113. When the vehicle reaches a certain distance, the first governor valve 11
The spool 177 of No. 3 moves and the circuit 157 becomes the circuit 158.
The governor pressure is output to this circuit 158, and the governor pressure is output from the circuit 158 to the 1-2 shift valves 131, 2-.
It is balanced by respective springs that act on each end face of the 3-shift valve 132 and the cut-down valve 134 and press each of these valves to the right in the figure. Also, the servo 141 tightens the second brake 106 from the boat c of the speed selection valve 130 via the circuit 153, the circuit 161, and the circuit 162.
1-2 in the middle of the hydraulic circuit reaching the engagement side hydraulic chamber 169.
A shift valve 131 and a second lock valve 135 are provided separately, and a circuit 152 that reaches the second lock valve 135 from the boat b of the speed selection valve 130 is also provided. Therefore, when the speed selection valve is set to the ○ position, the spool 150 of the speed selection valve 130
moves and the line pressure circuit 144 connects boats a, b, and c.
Leads to.

Hydraulic pressure is applied from boat a through circuit 161, and part of it acts on the lower part of second lock valve 135, and spool 178, which is pressed upward by spring 179, receives hydraulic pressure from boat b through circuit 152. The remaining part passes through the orifice 166 and reaches the 2-3 shift valve 132 from the circuit 167, and from the boat c passes through the circuit 153 and reaches the second governor valve. 114, the rear clutch 105 and the 1-2 shift valve 131 are reached, and the transmission enters the first far forward state. In this state, when the vehicle speed reaches a certain speed, the governor pressure of the circuit 158 causes the spring 159 to
1-2 shift valve 131 being pushed to the right by
The spool 160 moves to the left, and an automatic shift action from the first forward speed to the second forward speed is performed as described below. That is, at this time, the circuit 153 and the circuit 161 are brought into conduction, and the hydraulic pressure is transferred from the circuit 162 through the second lock valve 135 to the engagement-side hydraulic chamber 169 of the servo 141, thereby engaging the second brake 106.
When the rear clutch 105 is kept engaged, the transmission enters the second forward state described above. In this case, since the 1-2 shift valve 131 is miniaturized, the speed at the shift point does not increase and the spool 16 moves to the left at the required speed to perform an automatic shift action from the first forward to the second far. will be held. When the vehicle speed increases further and reaches a certain speed, the governor pressure of the circuit 158 overcomes the spring 163 and pushes the spool 164 of the 2-3 shift valve 132 to the left, and the circuits 167 and 168 become conductive, and the hydraulic pressure is transferred from the circuit 168. A portion reaches the release side hydraulic chamber 1701 of the servo 141 and reaches the second brake 106.
is released, the remaining part reaches the front clutch 104 and engages it, and in conjunction with the engagement and holding of the rear clutch 105, the transmission enters the aforementioned third forward speed state. When the speed selection valve 130 is set to the RO (second forward speed fixed) position, the speed selection valve 130
The spools 15 and line pressure circuits 144 lead to boats b, c and d. Hydraulic pressure reaches the same location from boats b and c as in the case of position D, and the rear clutch 105 is engaged, while no hydraulic pressure is coming to the lower part of the second lock valve 135 on this day. Since the areas of the lands above and below the area where the spool 178 opens the circuit 152 and hydraulic pressure is applied are larger at the bottom, the spool 178 of the second lock valve 135 is pushed down against the force of the spring 179 and the circuit 152 and the circuit 162 are electrically connected,
The hydraulic pressure reaches the engagement-side hydraulic chamber 169 of the servo 141, engages the second brake 106, and the transmission enters the second forward speed state. From boat d, oil pressure passes through circuit 154 to solenoid down shift valve 137 and throttle back up valve 18. There is a disconnection between the boat a of the speed selection valve 130 and the line pressure circuit 144, and the circuit 151
Since the hydraulic pressure has not reached the 2-3 shift valve 132, the second brake 106 is not released and the front clutch 104 is engaged, and the transmission is not in the forward third far position. 135 is the speed selection valve 13
0 and works to fix the transmission in the second forward speed state. When the speed selection mode is set to the 1 (forward, first far fixed) position, the line pressure circuit 144 is connected to boats c, d, and e. Hydraulic pressure reaches the same place as in case b from boats c and d and engages the rear clutch 105, and from boat e it goes from circuit 155 to the 1-2 shift valve 131, and from circuit 171, part of it goes to low reverse. - When the brake 107 is reached, the low reverse brake 107, which works as a forward reaction force brake, is engaged, and the transmission is in the first forward speed state, and a portion reaches the left side of the 1-2 shift valve 131 and the spring 15
9 to press the spool 160 to the right, and the first forward movement is fixed. Furthermore, if the driver depresses the accelerator pedal until it hits the stopper while driving in position D, desiring a large acceleration force, a kick-down switch (not shown) installed in the middle of the accelerator link will activate the accelerator pedal. Detected and turned ON, the down shift solenoid 2 installed opposite the solenoid down shift valve 137
5 is energized by electricity.

As a result, the spool 19 of the solenoid down shift valve 137 is pushed downward from the locked position upward in FIG. 2 by the spring 191. At this time, the kickdown circuit 180 that was connected to the circuit 154 is connected to the line pressure circuit 154.
4 and the line pressure passes through circuits 144 and 180 to 1-2.
The pressure is supplied to the shift valve 131 and the 2-3 shift valve 132 so as to oppose the governor pressure. At this time, if the vehicle is traveling in the third leg, the spool 164 of the 2-3 shift valve 132 is forcibly pushed from the leftward position by the line pressure to the rightward position against the governor pressure, and A forced downshift from the third far position to the second far position is performed within the vehicle far range limit, and sufficient acceleration force is obtained. By the way, when the above-mentioned kickdown is performed during running in the second distance, 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 1801 is transferred to the lm2 shift valve 131. Spool 131
The stone is also moved from the leftward position against the governor pressure. Therefore,
In this case, a forced downshift from second gear to first gear is performed, making it possible to obtain even stronger acceleration force corresponding to a large load. In the present invention, the following circuit for automatically applying an engine brake is added to the hydraulically controlled variable transmission described above with reference to FIGS. 1 and 2.

FIG. 3 shows an outline of this circuit, in which 20 is a converter cover, 21 is a transmission case, and 22 is a transmission case 21.
It is an extension installed at the rear of the A torque converter 1 is housed inside the converter cover 20, and a front clutch 104 and a rear clutch 105 are housed inside the transmission case 21 and rear extension 22.
, a second brake 106 and a low reverse brake 107, and other power transmission parts including friction elements are housed therein, and furthermore, in the lower part of the transmission case 21, a hydraulic control circuit shown in the second figure including the various valves mentioned above is housed. They are included in one set. The down shift solenoid 25 is provided at the lower part of the transmission case 21, and in the present invention,
In addition, there is a remote sensor 26 provided on the rear extension 22 and an access pedal 28 that is activated when the access pedal 28 is released.
Idle switch 29 as idle detection means
, and turns on when the brake pedal 30 is depressed.
A brake switch 31 as a brake operation detection means and a computer 32 to which signals from these elements 26, 29, and 31 are input are provided.

The computer 32 supplies the output signal to the down shift solenoid 25, and this solenoid can be turned on and off independently of the kickdown signal described above. FIG. 4 shows a specific example of the configuration of the computer 32,
This computer includes acceleration determining means consisting of an acceleration detection circuit 33, an acceleration setting circuit 34, and a comparator 35.

The acceleration detection circuit 33 receives the far-vehicle signal from the far-vehicle sensor 26, continuously detects increases and decreases in this signal at fixed time intervals, and calculates the acceleration of the vehicle by calculating the increase and decrease of the vehicle speed within a fixed time. Calculated value (acceleration signal) Gm is sent to comparator 3
It is supplied to the negative input terminal of 5. Further, the acceleration setting circuit 34 sends a signal Gs related to the set acceleration to a comparator 35.
This set acceleration signal Gs corresponds to the lower limit value of the acceleration range in which the vehicle requires engine braking. The comparator 35 receives the acceleration signal Gm
A NOR gate 36 functions as an engine brake command means to output an H level signal when the acceleration signal Gm is smaller than the set acceleration signal GS, and to output an L level signal (high acceleration detection signal) when the acceleration signal Gm is larger than the set acceleration signal Gs. 1
It is assumed that the power can be supplied to two input terminals.

One of the other two input terminals of the NOR gate 36 is connected to a power supply of 10 V through a timer 37 and a resistor 38 in order, and normally a signal at an H level from this power supply of 10 V is input to the timer 37.
The other end is connected to the power supply +V through a resistor 39, so that normally an H level signal is supplied from the power supply +V. The circuit between the timer 37 and the resistor 38 can be appropriately grounded via the idle switch 29 on the one hand, and the flip-flop circuit 40 on the other hand.
Connect to the set input terminal S of Further, the circuit between the NOR gate 36 and the resistor 39 can be appropriately grounded via the brake switch 31. Thus, when the idle switch 29 is OFF, it supplies the voltage of the power supply +V (a daily level signal) to the set input terminal S of the flip-flop circuit 40 via the resistor 38, and also supplies the voltage of +V to the set input terminal S of the flip-flop circuit 40 via the timer 37.
Supplied to the corresponding input terminal of the OR gate 36, when turned on,
In the presence of the resistor 38, an L level signal (idle detection signal) can be supplied to the set input terminal S of the flip-flop circuit 40 and the corresponding input terminal of the NOR gate 36. Furthermore, when the switch 31 is OFF, it supplies a voltage of 10 V from the power supply (a daily level signal) to the corresponding input terminal of the NOR gate 36 via the resistor 39, and when it is ON, the resistor 3
9, an L level signal (brake operation detection signal) can be supplied to the input terminal of the NOR gate 36. The timer 37 transmits this signal to the NOR gate 36 when the idle switch 29 is turned on and an L level signal is sent to the corresponding input terminal of the NOR gate 36 as described above.
It starts supplying to the corresponding input terminal after a predetermined time delay.
The idle switch 29 turns OFF and the NOR gate 3
When an H-level signal is directed to the input terminal of No. 6, this signal is passed through without the above-mentioned time delay.

The output terminal of the NOR gate 36 is connected to the flip-flop circuit 4.
0 reset input terminal R, and the output terminal Q of the flip-flop circuit 40 is connected to the input terminal of the NOT gate 41.

In the flip-flop circuit 4, when an H level signal is input to the set input terminal S, an H level signal is output from the terminal 9, and when an H level signal is input to the reset input terminal R, an L level signal is output from the terminal Q. In addition to outputting a level signal, these H level and L level signals are input to the set input terminal S.
It is assumed that the signal is held until an H-level signal is input to the terminal. The output terminal of the NOT gate 41 is connected to the down shift solenoid 25 via an amplifier 42, and
A power supply of 10 V is connected via a hand switch 43 and a resistor 44.

The manual switch 43 is mounted near the driver's seat, for example, on the steering column or the instrument panel, so that the driver can manually turn it on and off as needed to satisfy the requirements described below. The automatic transmission of the present invention, which is equipped with the electronic control circuit configured as described above, can automatically obtain engine braking even when the vehicle is traveling in the D position or in the third far distance, in the manner described below.

That is, when the vehicle is running downhill and the driver takes his foot off the accelerator pedal 28 (see FIG. 3) and depresses the brake pedal 30 (see FIG. 3), the vehicle applies engine braking. When the required large acceleration is received by the slope slope, the acceleration signal Gm becomes larger than the set acceleration signal Gs. Therefore, the comparator 35 supplies an L level signal (high acceleration detection signal) to the corresponding input terminal of the NOR gate 36. Also, in this driving state, the accelerator pedal is released and the brake pedal is depressed as described above, so both the idle switch 29 and the brake switch 31 are turned on, and the other two corresponding NOR gates 36 are turned on as described above. An L level signal (
idling detection signal and brake operation detection signal). However, the L level signal from the idle switch 29 is supplied to the corresponding input terminal of the NOR gate 36 only after the set time of the timer 37 has elapsed, and the L level signal from the idle switch 29 is supplied to the set input terminal of the flip-flop circuit 40. It is also supplied to terminal S. Thus, after the set time of the timer 37 has elapsed, L level signals are supplied to all input terminals of the NOR gate 36, and N
The OR gate 36 sends an H level signal (engine brake command) to the reset input terminal R of the flip-flop circuit 40.
supply. Therefore, the flip-flop circuit 40 outputs an L level signal from the output terminal Q, and the NOT gate 41
Enter. Therefore, the NOT gate 41 outputs an H level signal, which is amplified by the amplifier 42 and can energize the down shift solenoid 25. The down shift solenoid 25 operates the solenoid down shift valve 137 as described above by its activation, and performs a forced downshift to the second far position while driving in the third far position with the D range set. You can get the engine braking you need. Even if the driver takes his/her foot off the brake pedal 30 and the brake switch 31 is turned OFF, the engine brake is activated when the driver depresses the accelerator pedal 28 with the desire to accelerate, and the idle switch 29 is turned OFF.
It becomes an FF and continues as long as an H level signal is not supplied to the set input terminal S of the flip-flop circuit 40.

That is, the engine braking state continues as long as the driver does not depress the accelerator pedal 28 to accelerate the vehicle, that is, as long as engine braking is no longer required, and engine braking can be continuously obtained for the required period.
When the driver depresses the accelerator pedal 28 and the idle switch 29 turns OFF, the flip-flop circuit 40
The set input terminal S is connected to the H
The flip-flop circuit 40 outputs an H level signal from its output terminal 9, and this signal is inverted by the NOT gate 41 to become an L level signal. - The solenoid 25 is deenergized and the above-mentioned engine brake is released, allowing normal automatic transmission driving in the D range. Incidentally, if the driver determines that engine braking is necessary in addition to the automatic engine braking by the above-mentioned action, he/she turns the manual switch 43 ON'.

At this time, the voltage of the power supply +V (a daily level signal) is amplified by the amplifier 42 via the resistor 44 and the manual switch 43.
Supplied to down shift solenoid 25. Therefore, in addition to automatic engine braking by the above-mentioned action, engine braking can be obtained by energizing the down shift solenoid 25. Thus, since the automatic transmission of the present invention has a circuit for automatically applying the engine brake configured as described above, D
Even when driving in the 3rd range, the engine brake can be applied by automatically downshifting from the 3rd range to the 2nd range, and this engine braking can be applied only when it is really necessary, i.e., when the driver takes his foot off the gas pedal,
This applies only when the brake pedal is depressed and the acceleration received by the vehicle due to downhill driving exceeds the set value.
The driving feeling can be improved without causing the occupant to feel an uncomfortable feeling of deceleration due to unnecessary downshifting every time the brake is applied as in the conventional case.

Moreover, by installing a timer 37, it is possible to delay downshifting for engine braking by the set time. For example, when driving on a flat road, immediately after accelerating suddenly, you can take your foot off the accelerator pedal and press the brake pedal for a short time. Even if the vehicle acceleration during this brake operation exceeds the set acceleration due to the effect of previous sudden acceleration, as in the case where the brake pedal is pressed for a certain period of time, unnecessary downshifts will not be performed while driving on flat ground. It is possible to completely prevent the driving feeling from becoming worse. Furthermore, once the downshift is performed, engine braking can be obtained as long as necessary by holding the second shift until the driver depresses the accelerator pedal in order to accelerate the vehicle; When you step on the pedal and no longer need engine braking,
Immediately, the engine brake is automatically released and normal automatic transmission driving is resumed without interfering with this automatic transmission driving in any way. Moreover, these effects are achieved by using the existing down shift solenoid 25 in the hydraulically controlled variable transmission, so there is no need for additional valves, and they are achieved only by adding an electronic circuit. There is no need to change the design of the variable transmission at all, and the configuration of the present invention can be easily and inexpensively adopted. FIG. 6 shows a modification of the acceleration determining means of the electronic control circuit shown in FIG. Long range discrimination circuits 57 and 58 are provided. The far-vehicle area determination circuits 57 and 58 are connected to comparators 59, 60 and 61, 62 which receive signals from the far-vehicle sensor 26, and AN
D gates 63 and 64 are provided. In the low vehicle far range, the comparator 59 outputs an H level signal above the lower limit value, the comparator 60 outputs an H level signal above the upper limit value, and the AND gate 63 outputs an H level signal. Accordingly, the vehicle far range discrimination circuit 57 discriminates the low vehicle speed range and activates the acceleration setting circuit 34a. On the other hand, in a high vehicle speed range, the vehicle heading range determination circuit 58 determines the high vehicle speed range by the same action of the comparators 61, 62 and the AND gate 64, and the acceleration setting circuit 58 determines the high vehicle speed range.
Activate 4b. Therefore, acceleration setting circuits 34a, 3
4b is used for low vehicle distance and high vehicle distance, and the setting acceleration signals GS, . . . of these acceleration setting circuits 34a, 34b
GS2 is made to correspond to the lower limit value of the acceleration region that requires engine braking for each corresponding vehicle distant region. When the acceleration setting circuit 34a is activated at a low vehicle distance, the set acceleration signal G
When the acceleration setting circuit 34b is activated at high vehicle distance, the set acceleration signal Gs2 is supplied to the input terminal of the comparator 35b.

Incidentally, the acceleration signal Gm from the acceleration detection circuit 33 is input to one side input terminal of the comparators 35a and 35b, and the comparators 35a and 35b respectively receive Gm≧Gs, , GmZ
When GS2, an L level signal is applied to the corresponding input terminal of the OR gate 45, and when Gm<Gs, Gm<Gs2, an O signal is applied to the corresponding input terminal of the OR gate 45.
An H level signal can be supplied to the corresponding input terminal of the R gate 45. When an L level signal obtained by detecting GmZGs or GmZGs2 is input to at least one of its input terminals, the OR gate 45 performs "NOR".
By supplying an L level signal to the corresponding input terminal of the gate 36, the same operation as described above with reference to FIG. 4 can be performed thereafter. Therefore, according to the engine brake control circuit of this embodiment, in addition to the above-mentioned effects, it is also possible to exert the engine brake as desired in any vehicle distance range.

For example, even when driving downhill on a highway, even in conditions that require engine braking, it is possible to detect slight acceleration and downshift appropriately to apply engine braking. Furthermore, by changing the number and characteristics of the vehicle far range discrimination circuits 57, 58 and the acceleration setting circuits 34a, 34b, it is possible to freely change the downshift timing and freely obtain the engine braking characteristics most suitable for the vehicle. Furthermore, according to the present invention, the embodiment illustrated in FIG. 5 is configured as a digital circuit, and setting values are stored in a ROM (Read Only Memory) in place of the acceleration setting circuits 34a and 34b, so that each vehicle can correspond to a remote area. It is clear from the above-mentioned gist of the present invention that it is possible to extract and compare set values.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a general power transmission train of an automatic transmission, Fig. 2 is a hydraulic circuit diagram of a hydraulically controlled variable transmission, and Fig. 3 is an engine brake control section of the automatic transmission of the present invention. The block diagram shown in FIG. 4 is also an electronic circuit diagram thereof, and FIG. 5 is an electronic circuit diagram similar to FIG. 4 showing another example of the present invention. 1"""torque converter, 4...crankshaft,
13... Oil pump, 20... Converter cover, 2
1...Transmission case, 22...Rear extension, 25...Down shift solenoid, 2
6...Vehicle distance sensor, 28...Accelerator pedal, 29...Idle switch, 30...
...Brake pedal, 31...Flake switch, 32
... Computer, 33 ... Acceleration detection circuit, 34
, 34a, 34b... Acceleration setting circuit, 35, 35
a, 35b... Comparator, 36... NOR gate, 37... Timer, 38, 39... Resistor, 40
...Flip-flop circuit, 41...NO
T gate, 42...Amplifier, 43...Manual switch, 4
4...Resistance, 45...OR gate, 57, 58...
Vehicle long range discrimination circuit, 100, 111... Planetary gear set, 104... Front clutch, 105...
...Rear clutch, 106...Second flake, 1
07...Low reverse brake, 128...Line pressure adjustment valve, 130...Speed selection valve, 131...
1-2 shift valve, 132...2-3 shift valve, 137...
...Solenoid down shift valve. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. By hydraulically operating various valves, hydraulic pressure is appropriately supplied to the friction elements that determine the power transmission path to perform gear change control, and when the accelerator pedal is depressed to the maximum, the downshift solenoid is activated. In a hydraulically controlled automatic transmission that is configured to forcibly downshift from a selected gear to a lower gear depending on force, the system includes an idle detection means for detecting release of the accelerator pedal and a brake operation detection means for detecting depression of the brake pedal. an acceleration determining means for detecting that the acceleration of the vehicle has exceeded a set value; and an engine for issuing an engine brake command when all detection signals from the idle detecting means, the brake operation detecting means, and the acceleration determining means are received. An automatic transmission comprising: brake command means, and configured to automatically downshift from a selected gear to a low gear by energizing the downshift solenoid in response to the engine brake command. 2. The automatic transmission according to claim 1, wherein the acceleration determining means varies the set acceleration according to the vehicle speed and compares this with the vehicle acceleration. 3. A patent claim characterized in that a timer is provided to output a signal with a fixed time delay from the idle detection signal from the idle detection means, and this signal is supplied to the engine brake command means as an idle detection signal. Automatic transmission according to the range 1 above.