JPH0535294B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a shift hydraulic pressure control method in an automatic transmission for a vehicle, which supplies appropriate hydraulic pressure to frictional engagement elements during gear shifting to always perform gear shifting in a good condition. Automatic transmissions for vehicles supply hydraulic pressure to frictional engagement elements such as clutches and brakes, and
By selecting rotational elements such as gears, gear ratios (shifts) are automatically performed according to the driving conditions of the vehicle, and this frictional engagement is used to protect devices and equipment and maintain a comfortable ride. The delivery of pressure oil to the elements occurs gradually according to certain predetermined characteristics. An example of a conventional general automatic transmission for a vehicle will be described with reference to FIG. ing.
The torque converter 6 includes a pump 8 and a turbine 1.
0, a stator 12, and a one-way clutch 14, the stator 12 is coupled to the case 16 via the one-way clutch 14, and the one-way clutch allows the stator 12 to rotate in the same direction as the crankshaft 4, but not in the opposite direction. The structure does not allow rotation. The torque transmitted to the turbine 10 is transmitted to the input shaft 20
The signal is transmitted to a gear transmission 22 disposed at the rear thereof, which achieves four forward speeds and one reverse speed. The transmission 22 includes three sets of clutches 24, 2
6, 28, two sets of brakes 30, 32, one set of one-way clutch 34, and one set of Ravigneau type planetary gear mechanism 36. The planetary gear mechanism 36 includes a ring gear 38, a long pinion gear 40, a short pinion gear 42, a front sun gear 44, a rear sun gear 46, and both pinion gears 4.
0 and 42, and is also rotatable.
8 is connected to the output shaft 50, and the front sun gear 4
4 is connected to the input shaft 20 via the kickdown drum 52 and the front clutch 24, the rear sun gear 46 is connected to the input shaft 20 via the rear clutch 26, and the carrier 48 is connected to the input shaft 20 via the kickdown drum 52 and the front clutch 24. 4 connected to the case 16 via a reverse brake 32 and a one-way clutch 34 and disposed at the rear end of the transmission 22.
It is connected to the input shaft 20 via a speed clutch 28. The kickdown drum 52 can be fixedly connected to the case 16 by a kickdown brake 30. The torque passing through the planetary gear mechanism 36 is transmitted from the output gear 60 fixed to the output shaft 50 to the driven gear 64 via the idle gear 62, and then to the driven gear 64.
The signal is transmitted to a differential gear device 72 connected to a drive shaft 70 of the drive wheels via a transfer shaft 66 and a helical gear 68, which are fixed to the drive shaft 70 of the drive wheels. Each of the above-mentioned clutches and brakes, which are frictional engagement elements, is composed of a frictional engagement device equipped with an engagement piston device or a servo device, etc., and is driven by the engine 2 by being connected to the pump 8 of the torque converter 6. It is operated by hydraulic pressure generated by a wheel pump 74 shown in FIG. The hydraulic pressure is controlled by a hydraulic control device, which will be described later.
The power is selectively supplied to each clutch and brake according to the operating state detected by various operating state detection devices, and the combination of the operation of each clutch and brake provides four forward and reverse speeds as shown in Table 1. 1
gears are achieved. In the same table, the ○ mark indicates the engagement state of each clutch or brake, and the ⓓ mark indicates that the rotation of the carrier 48 is stopped by the action of the one-way clutch 34 immediately before the low reverse brake 32 is engaged during gear shifting. It shows. Next, an electro-hydraulic control device for achieving the gears shown in Table 1 in the gear transmission 22 shown in FIG. 1 will be described. The hydraulic control device shown in FIG. 2 supplies oil discharged from an oil pump 74 from an oil reservoir 76 through an oil filter 78 and an oil passage 80 to the torque converter 6, the clutches 24, 26, 28 of the transmission 22, and the brake 30. , 32 piston devices or servo devices, the hydraulic pressure supplied to each hydraulic chamber is controlled according to the operating state, and mainly the pressure regulating valve 8
2, torque converter control valve 84, pressure reducing valve 86,
Manual valve 88, shift control valve 90, rear clutch control valve 92, N-R control valve 94, hydraulic control valve 96 during gear shifting, N-D control valve 98, 1-2 speed shift valve 1
00, 2-3 speed and 4-3 speed shift valve 102, 4
The components include a speed clutch control valve 104 and three solenoid valves 106, 108, and 110,
Each element is connected by an oil passage. Among these components, shift control valves 90 and 1-2 serve as switching valves that switch oil passages to the frictional engagement elements 24, 26, 28, 30, and 32 to switch the gear ratio.
speed shift valve 100, 2-3 speed and 4-3 speed shift valves 102, and 4 speed clutch control valve 104 function;
A hydraulic control valve 96, an N-R control valve 94, and a solenoid valve 106 during gear shifting, which control the hydraulic pressure supplied to each frictional engagement element, are controlled by an electronic control device 112.

[Table] Each of the solenoid valves 106, 108, 110 has the same structure, and the electronic control device 1
Each orifice 114,
116, 118 is a closed type solenoid valve when not energized, which controls the opening and closing of solenoids 120, 12.
2, 124, a valve body 12 disposed within the solenoid to open and close each orifice 114, 116, 118;
6, 128, 130 and springs 132, 134, 136 that bias the valve body in the closing direction. The electronic control device 112 includes a driving state determining device that detects the driving state of the vehicle and determines the opening/closing combination of the solenoid valves 108 and 110, a shift detecting device that detects the start of a shift, and performs duty control. The hydraulic pressure is controlled by operating and stopping the solenoid valve 106 and changing the valve opening time by controlling the single pulse current width of the 50 Hz pulse current supplied to the solenoid valve 106.
110, and its input elements include an engine load detection device 138 that detects the throttle valve opening (not shown) or intake manifold negative pressure of the engine 2, and a rotation speed detection device 140 of the engine 2, as shown in FIG. Kickdown drum 52 shown in
a rotational speed detection device 142 for detecting the rotational speed of the output shaft 50 corresponding to the vehicle speed, a rotational speed detection device 144 for the driven gear 64 articulated to detect the rotational speed of the output shaft 50 corresponding to the vehicle speed, an oil temperature detection device 146 for detecting the lubricating oil temperature, and a select It consists of a lever selection position detection device 148, an auxiliary switch selection position detection device 150, and the like. Pressure oil discharged from the oil pump 74 is guided to a pressure regulating valve 82, a manual valve 88, and a pressure reducing valve 86 via an oil passage 160. The manual valve 88 has four positions: D, N, R, and P. When the manual valve 88 is in the D position, the oil passage 160 is connected to the oil passage 172,
174, and as shown in Table 2, the gear transmission 22 achieves the forward operating state of the first to fourth speeds according to the combination of ON and OFF of the solenoid valves 108 and 110, and the N When it comes to the position, oil passage 16
0 is communicated only with the oil passage 174, and the oil passage 172 is communicated with the oil drain port 176, so that the gear transmission 22 achieves a neutral state.When the R position is reached, the oil passage 160 is communicated with the oil passages 178 and 180, and the gear transmission 22 is brought into a neutral state. Transmission device 22
When the P position is reached, all the oil passages communicating with the manual valve 88 are communicated with the oil drain port 176 or the oil drain passage 182, so that the gear transmission 22 becomes substantially neutral. state.

[Table] The pressure regulating valve 82 has a spool 188 and a spring 190, which have pressure receiving surfaces 184 and 186, and the hydraulic pressure from the oil passage 160 is transferred to the pressure receiving surface 184 from the oil passage 174.
, the oil pressure in the oil passage 160 is regulated to a predetermined constant pressure (hereinafter referred to as line pressure), and the pressure receiving surface 1
When the oil pressure from the oil passage 160 acts on the oil passage 86 via the oil passage 178, the oil pressure in the oil passage 160 is regulated to a predetermined value. Torque converter control valve 84 is connected to spool 192
and a spring 194, the pressure oil guided from the pressure regulating valve 82 through the oil passage 196 is connected to the spool 1.
The spool 1 is connected to the spool 1 through an oil passage 198 formed in the
Hydraulic pressure and spring 1 acting on the right end pressure receiving surface of 92
The pressure is regulated to a predetermined value by balancing with the biasing force 94 and supplied to the torque converter 6 via the oil passage 200. Note that the oil discharged from the torque converter 6 is supplied to each lubricating section of the transmission via an oil cooler 202. The pressure reducing valve 86 is connected to the spool 204 and the spring 2
06, and the balance between the hydraulic pressure due to the area difference between the hydraulic surfaces 208 and 210 formed opposite to each other on the spool 204 and the biasing force of the spring 206,
The hydraulic pressure from the oil passage 160 is adjusted to be reduced to a predetermined value and then supplied to the oil passage 212. The pressure regulating oil (reducing oil) guided to the oil passage 212 is fed to the orifice 214.
to the N-R control valve 94, the hydraulic control valve 96, and the orifice 114 of the solenoid valve 106. The N-R control valve 94 has pressure receiving surfaces 216, 218,
220 is formed, and a spring 224, the oil is released by the balance between the hydraulic pressure acting on the pressure receiving surface 216, the hydraulic pressure due to the area difference between the pressure receiving surfaces 218 and 220, and the resultant force of the biasing force of the spring 224. The oil pressure in the passage 226 is regulated to a predetermined value. The hydraulic control valve 96 has pressure receiving surfaces 228, 230, 2
32 is formed, and a spring 236, the oil is released by the balance between the hydraulic pressure acting on the pressure receiving surface 228, the hydraulic pressure due to the area difference between the pressure receiving surfaces 230 and 232, and the resultant force of the biasing force of the spring 236. The oil pressure in the passage 238 is regulated to a predetermined value. The adjusted hydraulic pressure led to the oil passage 226 is used to control the low reverse brake 32 when obtaining the reverse gear, and the adjusted oil pressure led to the oil passage 238 is used to control the forward movement or stop of the vehicle. In the condition, front clutch 24, rear clutch 2
6. Controls the kickdown brake 30 and low reverse brake 32. The solenoid valve 106 is duty-controlled by the electronic control unit 112 with a constant frequency pulse current of 50 Hz whose pulse width is changed according to the operating state, and the ratio of opening/closing time of the orifice 114 is changed by changing the pulse width. It controls the hydraulic pressure in the oil passage 212 downstream from the orifice 214, that is, the hydraulic pressure acting on the pressure receiving surface 216 of the N-B control valve 94 and the pressure receiving surface 228 of the hydraulic control valve 96.
This oil pressure change adjusts the oil pressure supplied to each frictional engagement element. That is, the oil pressure is regulated based on the relationship between the diameter of the orifice 214 and the diameter of the orifice 114, and accordingly, the oil passages 226, 2
Adjustment hydraulic pressure generated in 38 (oil path 180 or oil path 1
72) increases or decreases proportionally in response to the increase or decrease in the above-mentioned oil pressure. The operation start timing and operation period of the solenoid valve 106 are determined by the engine load detection device 13.
8. Determined by the electronic control unit 112 in response to electrical signals from the rotational speed sensors 140, 142, 144, a shift detection device built into the electronic control unit 112 that detects the start of a shift, etc. The shift control valve 90 is a solenoid valve 108,1
It has three spools 240, 242, 244 and two stoppers 246, 248, and the spool 240 has lands 250, 252 and an annular groove 25.
4 and the oil chamber 2 on the left side of the same groove 254 and land 250
56, and the spool 242 has lands 260, 262 with different diameters,
An annular groove 264 and pressing parts 266 and 268 that come into contact with each spool 240 and 244 are provided, and the spool 244 has lands 270 and 272 and an annular groove 27.
4 and the oil chamber 2 on the right side of the same groove 274 and land 272
An oil passage 278 communicating with 76 is provided.
Also, the stopper 246 is connected to the spools 240, 242.
A stopper 248 is interposed between the spools 242 and 244 and is fixed to the casing. The oil passage 172 is always communicated with an oil passage 280 via the annular groove 264, and the oil passage 280 is connected to the orifice 116, the left oil chamber 256, and the right oil chamber 27 via the orifice 282.
6 and through an orifice 284 to the orifice 118 and the spools 240, 242.
It communicates with an oil chamber 286 in between. The rear clutch control valve 92 includes a spool 294 provided with a land 288, a land 290 with a smaller diameter than the land 288, and an annular groove 292, and three lands 296, 298 with the same diameter as the land 290.
300 and annular grooves 302, 304, and a spring 308, the pressing force of the hydraulic pressure guided to the oil chamber 310 on the left side of FIG. 2 and acting on the pressure receiving surface of the land 288 is If the force becomes greater than the resultant force of the hydraulic pressure guided to the oil chamber 312 on the right side of Figure 2 and acting on the pressure receiving surface of the land 300 and the urging force of the spring 308, both spools 294, 3
06 is switched to the right end position in the figure. Furthermore, when the right end position is reached, hydraulic pressure acts between the lands 290 and 296, so when the hydraulic pressure in the oil chamber 310 is discharged, only the spool 294 moves to the left end, and then the hydraulic pressure acts on the left pressure receiving surface of the land 296. The spool 306 moves to the left when the pressing force becomes smaller than the resultant force of the hydraulic pressure in the oil chamber 312 and the biasing force of the spring 308. The N-D control valve 98 has a spool 320 provided with lands 314, 316 and an annular groove 318, and a spring 322, and has hydraulic pressure acting on pressure receiving surfaces 324, 326, 328 formed on the spool 320. The spool 320 is selectively switched between the left end position shown in FIG. 2 and the right end position (not shown) depending on the direction of the resultant force with the biasing force of the spring 322. The 1-2 speed shift valve 100 has a spool 330 and a spring 332, and is shifted between the left end position shown in FIG. 2 and the right end position (not shown) by supplying and discharging line pressure to the left end pressure receiving surface 334 of the spool 330. It can be switched, and when line pressure is supplied to the pressure receiving surface 334, it is moved to the right end by the hydraulic pressure of the same line pressure, and when the line pressure is discharged, it is located to the left end by the biasing force of the spring 332. It is. Similarly, the 2nd-3rd speed and 4th-3rd speed shift valves 102 and the 4th speed clutch control valve 104 are each connected to a spool 33.
6, 338 and springs 340, 342, oil chambers 344, 346 to which line pressure is guided are formed on the left side of each spool 336, 338, and oil chambers 348, 350 are formed on the right side of each spool. It can be selectively switched to the left end position shown in FIG. 2 or to the right end position (not shown). Next, the operation of the automatic transmission with the above structure will be explained. Since the speed change control of the automatic transmission with the same structure as above is already known (see Japanese Patent Application No. 144237/1984), only 1st speed will be explained here. →Using 2nd gear as an example, explanations of other gears will be omitted. First, when the first gear has been reached, both the solenoid valves 108 and 110 are energized, and the line led from the oil passage 160 to the oil passage 172 via the hand valve 88. Pressure is hydraulic control valve 9
6, oil passage 238, N-D control valve 98, oil passage 35
2. The rear clutch control valve 92 is led to the hydraulic chamber of the rear clutch 26 via the oil passage 354;
Branching from the oil passage 238 to the 1st speed-2nd speed shift valve 10
0, low reverse brake 3 via oil passage 356
2 hydraulic chamber, and the rear clutch 2
6. Both the low reverse brakes 32 are in an engaged state. When the accelerator is depressed in this state, the electronic control unit 112 sends the solenoid valves 108, 110
A shift start signal is sent to the solenoid valve 108.
is de-energized, and the solenoid valve 110 is kept energized. As a result, the spool 240 of the shift control valve 90
moves integrally with the spool 242 to the right in FIG.
42 between the two lands 260, 262, and is led to the oil passage 362, and the line pressure acts on the pressure receiving surface 334 of the 1st-2nd speed shift valve 100, and the spool 3
30 to the right end position in FIG. As a result, the line pressure that had been led from the oil passage 238 to the 1st-2nd speed shift valve 100 is supplied to the engagement side hydraulic chamber 366 of the kick-down brake 30 via the oil passage 364 as the initial gear shift oil pressure. Hydraulic chamber 366
As the oil pressure gradually increases, the rod 368 moves to the left in FIG. 2 against the spring 370, kicking down the brake band 30a.
2, while the oil pressure in the oil passage 356 is applied to the oil passage 2.
26 and is discharged through the low reverse brake 3
2 is disengaged, and a shift to 2nd speed is achieved. As mentioned above, an automatic transmission for a vehicle has a frictional engagement element operated by hydraulic pressure and a rotating element selected by the operation of this frictional engagement element, and hydraulic pressure is supplied depending on the running state of the vehicle. This method automatically selects the frictional engagement element that is used to change the gear ratio between the input shaft, into which the rotational power of the engine is input, and the output shaft, which outputs the rotational power to the drive wheels. The following problems have occurred depending on the degree of increase in the oil pressure supplied to the frictional engagement elements during the shift period, that is, from the start of the shift to the end of the shift.
In other words, if the feed oil pressure is suddenly increased, the frictional engagement elements are suddenly connected and the shock during gear shifting becomes large, which not only places an excessive load on the automatic transmission and engine, but also causes damage to the vehicle's ride. It was also making me feel worse. On the other hand, if the feed oil pressure rises too slowly, the shift time becomes longer and the frictional engagement element slips excessively, shortening the life of the frictional engagement element or preventing the gearshift from being carried out. There was a fear that it would not happen. The present invention has been made in view of the above circumstances, and it guarantees the shift function of an automatic transmission regardless of the driving state of the vehicle, and also achieves proper hydraulic pressure delivery to the frictional engagement elements during gear shifting. The object of the present invention is to realize good gear shifting without causing excessive gear shifting impact or slipping of frictional engagement elements. The gear shift hydraulic control method according to the present invention achieves the above object, by selecting an input shaft into which the rotational power of the engine is input, an output shaft which outputs the rotational power to the drive wheels, and an arbitrary rotational element. In an automatic transmission for a vehicle, comprising a hydraulically operated frictional engagement element that switches a gear ratio between a shaft and the output shaft, and a detection device that detects the rotational speed of the rotating element whose rotational speed changes during gear shifting. , controlling the oil pressure to the frictional engagement element so that the rate of change in rotational speed detected by the detection device follows a preset target rate of change, and changing the oil pressure as the shift time elapses. The oil pressure is maintained at a preset minimum oil pressure or higher. An example in which the method of the present invention is applied to the automatic transmission for a vehicle shown in FIGS. 1 and 2 will be described below. The explanation will be given by taking the gear stage from the first gear to the second gear as an example, and the explanation of the other gear gears will be omitted. A flowchart representing this embodiment is shown in FIG. 3, and this flowchart is stored in the electronic control unit 112 to control the shift hydraulic pressure according to the present invention. This embodiment will be explained along the flowchart shown in FIG.
When a shift start signal is transmitted and the solenoid valves 108 and 110 are switched as described above, the initial state of the solenoid valve 106 is determined based on the throttle valve opening detected by the detection device 138 and the vehicle speed detected by the detection device 144. The duty rate d ₁ (for example, 42% in this embodiment) is determined. This results in
The solenoid valve 106 is duty-controlled to adjust the control oil level downstream of the orifice 214 in the oil passage 212, and the kick-down brake 30 is supplied from the oil passage 172 through the oil passage 238, the 1-2 speed shift valve 100, and the oil passage 364. The shift initial oil pressure P ₁ is supplied to the oil pressure chamber 366. When hydraulic pressure is supplied to the hydraulic chamber 366 as described above, it is determined whether or not the first gear is out of synchronization based on the rotational speed of the kickdown drum 52 and the vehicle speed. If this desynchronization has not been achieved, it is assumed that the duty rate _d1 of the initial oil pressure _P1 is too low, and the duty rate is recalculated and increased to achieve the desynchronization. When desynchronization is achieved as described above, the target rate of change in the rotational speed of the kick-down drum 52, which is predetermined according to each gear stage and running condition, that is, the oil pressure supplied to the hydraulic chamber 366 is optimal. The rate of change in rotational speed that the kick-down drum 52 exhibits when the rotation speed is rising at a certain degree (in a state where the kick-down brake 30 does not engage or excessively slip, etc.) is determined according to the running state of the main gear. do. Then, the rate of change is calculated from the actual rotational speed of the kickdown drum 52 to calculate the deviation from the target rate of change, and the duty rate correction amount corresponding to this deviation is calculated to control the duty of the solenoid valve 106. is corrected, and the degree of hydraulic pressure delivered to the hydraulic chamber 366 of the kick-down brake 30 is changed. That is, as shown in FIG. 5c, the actual rotational speed change rate (dotted line) of the kick-down drum 52, which initially deviates greatly from the target change rate (solid line), follows the target change rate at the final stage. The hydraulic pressure in the hydraulic chamber 366 is feedback-controlled so that the values are the same or approximate, and the kick-down brake 30 is controlled to be applied to the optimum degree. Then, the rotation speed of the kick-down drum 52 and the vehicle speed are detected, and the rotation speed of the kick-down drum 52 matches or approximates the target rate of change at a predetermined rotation speed N _D (in this embodiment, the rotation speed is It is determined whether the actual rotational speed of the kickdown drum 52 matches 70% of the total rotational speed change amount Ns of the drum 52, and if the rotational speed of the kickdown drum 52 is not _ND , Continuing the above feedback control, the kickdown drum 5
2 rotation speed is zero, that is, the shift to the 2nd speed is completed. Therefore, this shift is performed in a good condition by feedback control without causing excessive slippage of the shift shock or the frictional engagement element. In this case, if this oil pressure is lowered too much, the following situation may occur. In other words, since automatic transmissions for vehicles have a variety of operating states depending on the driving conditions of the vehicle, in some cases, the above-mentioned feedback control may result in prolonged shift times or failure to shift. There is. Specifically, for example, when a vehicle is in a driving state where the amount of accelerator pedal depression is small, when the foot is removed from the accelerator, the gear is shifted up to ensure smooth driving. In this case, if an attempt is made to make the rotational speed of the rotating element, which naturally decreases with the engine rotational speed, follow the target rate of change, the oil pressure will continue to decrease, and there is a possibility that the shift will not be completed forever. Furthermore, even if the accelerator is depressed deeply when the oil pressure has dropped significantly as described above, the rise in oil pressure will not respond to this, and the input data to the electronic control unit 112 will be confused, resulting in a shift state. It is also possible that you will not be able to grasp it. In order to eliminate such unexpected situations, a subroutine shown in FIG. 3 is provided in the feedback control flowchart. That is, when calculating the duty rate in response to the deviation between the target rate of change and the rotational speed change rate of the kickdown drum 52 in the feed bag control as described above, the kickdown brake is equipped with a Kickdown servo switch 3
Elapsed time t from the start of shifting to the end of shifting obtained from the elapsed time from ON to OFF of 0b (shifting time)
is detected, and the lowest oil pressure, that is, the highest duty rate d(t), which is a function of this elapsed time t, is calculated. In this calculation, the initial value (for example, 78% in this embodiment) is di, and the duty change rate (for example, 15% in this embodiment) is
%/sec) is set as d', and is performed using the calculation formula d(t)=di-d〓・t.
A maximum duty rate d(t) that changes with time t and a minimum oil pressure P(t) corresponding to this maximum duty d(t) are determined as shown by a dashed line in the figure. Then, the duty rate d of the hydraulic pressure actually supplied to the downbrake 30 at each point during gear shifting is compared with the maximum duty rate d(t), and dd(t)>
In the case of 0, the electronic control unit 112 is commanded to lower the duty rate (that is, increase the feed oil pressure), and the duty rate of the electronic control unit 112 is set to the maximum duty rate d(t) or less and the signal is sent to the kickdown brake 30. The supplied hydraulic pressure is prevented from falling below the minimum hydraulic pressure P(t). Therefore, an excessive drop in the oil pressure supplied to the kick-down brake 30 is prevented, and the occurrence of the above-mentioned unexpected situation can be eliminated. Here, the above initial value di and duty change rate
d´ is set appropriately depending on the characteristics of the engine, automatic transmission, vehicle, etc., and the key is to adjust the range of rise and fall of the oil pressure by feedback control in order to prevent an excessive drop in the oil pressure that would lead to the above-mentioned unexpected situation. Any device that can set the maximum duty rate that defines the lower limit may be used. In addition, as shown in Table 1, each gear is engaged,
Kickdown brake 3 that repeatedly disengages
Since the kick-down drum 52, which repeatedly stops and rotates depending on 0, is used as the rotating element to be detected,
Although one detection device (sensor) 142 can perform feedback control at all gears, it is also possible to use a rotating element that operates only at a certain gear. In addition, in this example, an automatic transmission set to be compatible with an engine having a certain standard such as displacement and output torque amount is also used for an engine having a different standard, thereby reducing the product cost of the automatic transmission. reduction of
In order to simplify production management, a control function is also provided to adapt the oil pressure sent to the downbrake 30 after the transmission of the gear shift signal, that is, the gear shift initial oil pressure _P1 , to engines of different standards. That is,
If this initial shift oil pressure P ₁ does not comply with the engine standard, for example, when an automatic transmission for a relatively large displacement engine is combined with a relatively small displacement engine, the Compared to automatic transmissions, the operating oil pressure (line pressure) of large-displacement transmissions is inherently higher, and the engagement force of the frictional engagement element becomes excessive compared to the output torque of this engine, causing a shift start signal to be sent. A problem arises in that the frictional engagement element becomes engaged due to the initial oil pressure, resulting in a significant shift shock.
Moreover, in the opposite case, the line pressure is too low, resulting in problems such as not being able to start shifting or that it takes a long time to shift. In order to solve this problem and realize the application of automatic transmissions to engines with different standards, in the above case, when the detected actual rotational speed of the kick-down drum 52 is N _D , Similarly, in order to set an appropriate initial shift oil pressure before completing the shift to 2nd gear, the oil pressure that is being supplied to the downbrake 30 at this point is
In addition to detecting the duty rate d ₂ corresponding to P ₂ ,
The throttle valve opening θt of the engine 2 at that point in time is detected, and a duty ratio _d1 corresponding to the shift initial oil pressure that should originally be sent to the kickdown brake 30 after the shift start signal is issued is calculated. This calculation calculates the total throttle valve opening at the shift stage from 1st to 2nd speed as A, as shown in Fig. 4.
It is divided into four regions B, C, and D, and a constant k is experimentally set for each region.
(constants k ₁ to _{k 4} correspond to regions D to A, respectively) and constant l (constants l ₁ to _{l 4} correspond to regions D to A, respectively)
The calculation is performed using the equation d ₁ =(kθt+l)d ₂ with the throttle valve opening θc as a variable within the region to which the detected throttle valve opening θt belongs. The oil pressure based on the duty rate d ₁ determined in this way is set as the initial oil pressure for the next gear shift, and thereby the next gear shift is adjusted to match the initial oil pressure that should be originally supplied to the engine, or This can be done from an approximate state. In addition to the calculation method described above, various methods based on experiments and experience can be used to correct the initial shift oil pressure, and the number of regions and the range of divisions may vary depending on the characteristics of the vehicle engine and automatic transmission. Set as appropriate. In addition, in the above embodiment, the 70% point of the total rotational speed change N _S of the kick-down drum 52 is taken as the late shift, and the corresponding duty rate d ₂ of the oil pressure P ₂ is changed from the duty rate d ₁ of the initial oil pressure P ₁ . However, if the total rotational speed change amount N _S is within the range of 50% to 100% and has converged to the target change rate due to feedback control, the duty rate d ₁ of the initial oil pressure P ₁ can be found in the same way. It is possible. As explained above, according to the present invention, feedback control is performed so that appropriate oil pressure is supplied to the frictional engagement elements during gear shifting, and the oil pressure due to this feedback is controlled to be equal to or higher than the minimum oil pressure that changes with the gear shifting time. This eliminates the occurrence of unforeseen situations such as prolonged shifting, failure, or inability to grasp the shifting status due to an excessive drop in oil pressure, and prevents excessive shifting shocks and frictional engagement elements due to feedback control. This makes it possible to achieve good gear shifting without causing any slippage or the like.

[Brief explanation of the drawing]

1 and 2 show an example of an automatic transmission that implements the method of the present invention, in which FIG. 1 is a schematic diagram of the power transmission section, FIG. 2 is a schematic diagram of the hydraulic control section, and FIG. 3 is a schematic diagram of the hydraulic control section.
The figure is a flowchart according to an embodiment of the present invention, Figure 4 is a shift characteristic graph showing the throttle valve opening range, and Figures 5a, b, c, and d are graphs showing the duty ratio versus shift time, and the shift characteristics for kickdown braking. 3 is a graph showing the feed oil pressure, the rotational speed of the kickdown drum, and the output shaft torque, respectively. In the drawing, 2 is the engine, 4 is the input shaft, 30 is the kickdown brake, 52 is the kickdown drum, 112 is the electronic control unit, P(t) is the minimum oil pressure, and d
(t) is the highest duty rate.

Claims (1)

[Claims] 1. An input shaft into which the rotational power of the engine is input; an output shaft which outputs the rotational power to the drive wheels; and an arbitrary rotational element selected between the input shaft and the output shaft. A vehicle automatic transmission comprising: a hydraulically actuated frictional engagement element that switches the gear ratio; and a detection device that detects the rotational speed of the rotating element whose rotational speed changes during gear shifting, wherein: The hydraulic pressure applied to the frictional engagement element is controlled so that the rate of change in rotational speed follows a preset target rate of change, and the hydraulic pressure is controlled to exceed a preset minimum hydraulic pressure that changes with the passage of shift time. A method for controlling shift hydraulic pressure in an automatic transmission for a vehicle, characterized in that: