JPH0459499B2 - - 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. Delivery of pressure oil to the elements must be done gradually according to certain predetermined characteristics. 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. 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 is intended to achieve proper hydraulic pressure delivery to the frictional engagement elements during gear shifting, and to provide a good system that does not cause excessive gearshift impact or slippage of the frictional engagement elements. The purpose is to realize gear shifting. A shift hydraulic control method for an automatic transmission for a vehicle according to the present invention which achieves the above object has an input shaft into which rotational power of an engine is input, an output shaft which outputs rotational power to a drive shaft, and an arbitrary hydraulically actuated a frictional engagement element that switches the gear ratio between the input shaft and the output shaft by selectively engaging with the rotating element, the target rotation that the rotating element should follow when the gear shift is started; The speed change rate is set to a relatively large first value, and when the rotational speed of the rotating element reaches a value immediately before the end of the shift, the target rotational speed change rate switches to a second value smaller than the first value. A vehicular automatic system configured as shown in FIG. In the transmission, the supply pressure to the frictional engagement element is temporarily reduced by a predetermined value before the rotational speed of the rotating element reaches the predetermined rotational speed and the target rotational change rate switches to the second value. It is characterized by causing Hereinafter, an embodiment in which the method of the present invention is applied to a shift initial oil pressure setting method already proposed in Japanese Patent Application No. 59-69926 will be described using a shift stage from 1st speed to 2nd speed as an example. First, a Ravigneaux-type automatic transmission with four forward speeds and one reverse speed in which the method of the present invention has been implemented will be explained with reference to FIG. 1, which schematically shows its structure. It is directly connected to the pump 8 of the converter 6. The torque converter 6 includes a pump 8, a turbine 10, and a stator 1.
2. It has a one-way clutch 14, and the stator 1
2 is connected to the case 16 via the one-way clutch 14.
The one-way clutch rotates the stator 12 in the same direction as the crankshaft 4, but
The structure does not allow rotation in the opposite direction. 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.
The carrier 48 rotatably supports the carriers 0 and 42 and is also rotatable, and the ring gear 38
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 6 via the idle gear 62.
4, and a transfer shaft 66 and a helical gear 68 fixed 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. 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 an oil pump (not shown). The hydraulic pressure is selectively supplied to each clutch and brake according to the operating state detected by various operating state detection devices by an electronic hydraulic control device controlled by a computer, which will be described later. As shown in Table 1, the combination of the following operations achieves four forward speeds and one reverse speed. In the same table, the ○ mark indicates the engagement state of each clutch or brake, and the ● mark indicates the engagement of the carrier 48 by the action of the one-way clutch 34 immediately before the low reverse brake 32 is engaged during gear shifting.
indicates that the rotation is stopped.

[Table] In this embodiment, as can be seen from Table 1, the kick down brake 30 is set to 1st gear - 2nd gear.
The speed of the kick-down drum 52 is changed from speed (2nd) to third speed (3rd) to fourth speed (4th). This kick-down drum 52 is set as a rotating element that serves as a reference for hydraulic control.
The rotational speed of the engine is detected by a sensor 142 and input into a computer 80 shown in FIG. FIG. 2 is a schematic configuration diagram showing a part of the electro-hydraulic control device for the gear transmission 22 which is duty-controlled by the computer 80. (Japanese Patent Application Laid-Open No. 58-46258), etc., so only the portions related to the kick-down brake 30, which is the object of control in this embodiment, will be explained here. The electronic hydraulic control device shown in Fig. 2 operates the downbrake 3 according to the operating condition by adjusting the line pressure of pressure oil discharged from an oil pump (not shown) to a constant pressure.
0 kick-down sobo piston 30a, and the duty is mainly controlled by the N-R control valve 94, the oil pressure control valve 96 during gear shifting, the N-D control valve 98, the 1st-2nd speed shift valve 100, and the computer 80. The component includes a controlled solenoid valve 106, and each component is connected by an oil path. According to such a configuration, when the first gear is achieved, the line pressure led to the oil passage 172 is transferred to the oil pressure control valve 96, the oil passage 238, the oil passage 1-
It is led to the hydraulic chamber of the low reverse brake 32 via the 2-speed shift valve 100 and an oil passage 356,
In this state, when the accelerator is depressed and a shift start signal is sent from the computer 80, a shift solenoid valve (not shown) is activated and the line pressure
- Move the 2nd speed shift valve 100 to the right end position in FIG. As a result, the line pressure led from the oil passage 238 to the 1st-2nd speed shift valve 100 is reduced to the oil passage 238.
Kickdown servo piston 30a via 64
The kickdown drum 5 is supplied to the engagement side hydraulic chamber of
The brake band 30b of the kick-down brake 30, which is wrapped in the second gear, is engaged with the kick-down drum 52, while the hydraulic pressure supplied to the low reverse brake 32 is discharged to achieve a shift to the second gear. As shown in FIG. 3, the computer 80 stores preset rotational speed change characteristics of the kick-down drum 52 during the shift from the first speed to the second speed. This characteristic is exhibited by the kick-down drum 52 when an ideal speed change is performed by supplying hydraulic pressure to the frictional engagement element at an appropriate level to prevent excessive gearshift impact or excessive slippage of the frictional engagement element. This is a change in rotational speed, and time A is just before the end of the gear shift.
The slope between the X zone and the Y zone,
In other words, the rotational speed change rate is different, and the
As already proposed in No. 60888, in the Y zone after time A, hydraulic pressure is sent to the frictional engagement element in order to suppress the output shaft torque fluctuation of the automatic transmission due to the engagement of the frictional engagement element near the end of the shift. The feed rate is made gentler and the rotational speed change rate of the kickdown drum 52 is made smaller than in the X zone. That is, the rotational speed change rate in the X zone is the first value, and the rotational speed change rate in the Y zone is the second value. Further, the computer 80 stores a flowchart as shown in FIG. 4, and according to this flowchart, the frictional engagement is adjusted so that the rotational speed change of the kick-down drum 52 during gear shifting conforms to the characteristics shown in FIG. The hydraulic pressure delivered to the element is controlled. still,
As mentioned above, this embodiment is applied to a method for setting the initial gear shift oil pressure, so the part related to this method is also included in the above flowchart, but this part will be explained later and first the gear shift oil pressure control of the present invention will be explained. The part related to the method (from the first gear out of synchronization to the end of the shift in FIG. 4) will be explained. When the computer 80 issues a shift start signal (shift start command in FIG. 3), the shift solenoid valve operates and the supplied hydraulic pressure begins to rise.
After the feed oil pressure starts to rise, the computer 80
Solenoid valve 106 whose duty is controlled by
Operating at a certain duty rate, the rotational speed of the kickdown drum 52 begins to decrease (shift start in FIG. 3), and the first gear becomes out of synchronization. Here, the solenoid valve 106 is a non-energized closed type whose opening/closing time ratio changes by changing the pulse width of the constant frequency pulse current, and the solenoid valve 106 is of a closed type when the current is not energized and is closed in the oil passage 212 downstream of the orifice 214 according to the duty rate. The kick-down servo piston 3 is controlled by controlling the oil pressure acting on the N-R control valve 94.
It controls the hydraulic pressure supplied to the frictional engagement elements such as 0a, and the duty rate and the hydraulic pressure supplied to the frictional engagement elements tend to contradict each other. Supply oil pressure tends to be low. When the synchronization is achieved as described above, a target rotational speed change rate that satisfies the characteristics of the X zone is determined, and a rotational speed change rate and a target rotational speed change rate calculated from the actual rotational speed of the kick-down drum 52 are determined. Calculate the difference between Next, a duty rate correction amount for this deviation is calculated and instructed, and the duty control of the solenoid valve 106 is corrected so that the actual rotational speed change of the kick-down drum (dotted line in Fig. 3) becomes the target rotational speed change (the The hydraulic pressure supplied to the kickdown servo piston 30a is adjusted so as to follow the solid line in Fig. 3). Next, the actual rotation speed N _D of the kick-down drum 52 and the vehicle speed are detected, and the rotation speed N _D is compared with the boundary rotation speed B between the X and Y zones. When the pressure is within the range, the hydraulic pressure adjustment using the duty control described above is repeated. The rotational speed N _D of the kick-down drum 52 is X,
When the rotation speed becomes equal to or less than the boundary rotation speed B of the Y zone, a command is given to increase the duty rate by 3%, and then a target rotation speed change rate that satisfies the characteristics of the Y zone is determined. Therefore, as shown in FIG. 3, the target rotational speed change rate (first value) of the X zone
to Y zone target rotational speed change rate (second value)
Before switching to , the duty rate is increased by 3% and the hydraulic pressure supplied to the kickdown brake 30 is temporarily lowered. Actual rotational speed of kickdown drum 52 N _D
Repeat the same hydraulic adjustment using duty control in the Y zone as in the X zone until N _D drops to 140 rpm, and by holding the duty rate d ₂ at 140 rpm for 0.1 seconds, you can shift to 2nd gear. The process ends (speed change ends in Fig. 3). As shown in FIG. 3, by increasing the duty rate and temporarily lowering the hydraulic pressure supplied to the kick-down brake 30, overshoot of the hydraulic pressure can be prevented at point A where the X zone and Y zone switch. , the oil pressure curve becomes smooth at point A without any temporary rise. Here, since the speed change is performed within a short time, the rotational change of the kick-down drum 52 that has followed the target rotational speed change rate in the X zone has a small slope due to the delay in the operation of components such as sensors and valves. There is a concern that the rotational speed of the kick-down drum 52 may not be able to follow the target rotational speed change rate of the Y zone, and the rotational speed of the kick-down drum 52 may fall without exhibiting predetermined characteristics, as shown by the dotted line in FIG. . However, as mentioned above, before the control starts in the Y zone, the duty rate is increased by 3% and the feed rate of the hydraulic pressure to the kick-down servo piston 30a is reduced, so the kick-down also occurs in the Y zone. drum 52
The rotation change follows the target rotation speed change. still,
The degree of increase in the duty rate is not limited to 3%, but is appropriately set depending on the characteristics of the vehicle, engine, automatic transmission, driving conditions, etc. As described above, by controlling the oil pressure to the kick-down servo piston 30a so that the actual rotation speed change rate of the kick-down drum 52 follows the target rotation speed change rate during gear shifting, the kick-down servo piston 30a is always Appropriate oil pressure is supplied, and good gear shifting is achieved without causing excessive gear shifting impact or excessive slipping of the frictional engagement elements. In this embodiment, the shift initial oil pressure is set and controlled using the above-mentioned shift oil pressure control. For example, when a certain automatic transmission is combined with engines of different displacements, output torques, etc., if the line pressure is too high and the engagement force of the frictional engagement element becomes excessive compared to the output torque of the engine. There is a problem in that the frictional engagement element immediately becomes engaged due to the initial hydraulic pressure supplied at the start of a shift, causing a large shift impact.
When the line pressure is too low, there is a problem that the shift takes a long time or the shift does not start. Shift initial oil pressure setting control is used to solve the above problem and adapt the automatic transmission to the engine, and is performed according to the flowchart shown in FIG. That is, after the shift from 1st gear to 2nd gear has started and a shift solenoid valve (not shown) is switched from 1st gear to 2nd gear, the engine throttle opening θ _t and the vehicle speed are detected. , for the time being, determine the duty rate d ₁ at the initial stage of gear shifting, and use this duty rate as
The initial shift oil pressure corresponding to _d1 is sent to the kickdown servo piston 30a. Then, the rotational speed of the kick-down drum 52 and the vehicle speed are detected, and the duty rate _d1 is corrected to repeatedly control the feed oil pressure until the first gear is out of synchronization. When the synchronization of the first gear is achieved in this way, the shift is proceeded in a good condition by the shift hydraulic control described above, and the duty ratio d ₂ at the time when the rotational speed of the kickdown drum 52 is 140 rpm is changed, for example. Arithmetic formula d ₁ ′=(k・
By θ _t +l)d ₂ , the duty rate d ₁ ' to be fed to the kickdown servo piston at the start of a shift is set as the conversion initial duty rate for the next shift so as to show the characteristics shown in FIG. In the equation, k and l are constants that are well determined by the throttle opening _θt and vehicle speed, respectively. Therefore, after the next shift, the shift initial oil pressure approximates or matches the predetermined value, and the engine and automatic transmission are matched, thereby realizing the versatility of the automatic transmission. Furthermore, as mentioned above
The duty rate _d2 at the time of N _D = 140 rpm is used as a reference because at N _D = 140 rpm, which is just before the end of the shift, the hydraulic pressure supplied to the kick-down servo piston 30a becomes approximately the appropriate value due to the shift hydraulic control. This is because the duty rate d ₁ ' can be calculated with high accuracy based on , but N _D is not limited to this and may be any other value just before the end of the shift. Although the above embodiment describes the gear stage from 1st to 2nd gear, the same can be applied to the gear stage from 2nd gear to 3rd gear and from 3rd gear to 4th gear. The same applies when applied to a Lavigneaux-type automatic transmission with three forward speeds and one reverse speed. In addition, in the above embodiment, the rotational element to be detected is a kick-down drum that changes between the rotating state and the stopped state at all gears, so the rotation speed detection device is simple, but the rotational state is changed only at a certain gear. A rotating element that switches between a stopped state and a stopped state, such as rear sun gear 4
6. It is also possible to use a carrier 48 or the like as appropriate. As explained above, according to the present invention, the supply of hydraulic pressure to the frictional engagement element is controlled so that the rotational speed change rate of the rotating element during gear shifting follows a preset target rotational speed change rate, and Since the hydraulic pressure feed rate is temporarily lowered before the value of the target rotational speed change rate changes just before the end of the shift, it is possible to prevent excessive shift impact or excessive slipping of the frictional engagement elements. It is possible to realize a speed change.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a vehicle automatic transmission to which an embodiment of the present invention is applied, and FIG. 2 is a schematic configuration diagram showing an example of a hydraulic control device for a kick-down brake.
FIG. 3 is a graph showing the concept of rotational speed change characteristics and supply oil pressure of the kick-down drum, and FIG. 4 is a flowchart of one embodiment of the present invention. In the drawing, 2 is an engine, 20 is an input value, 30 is a kickdown brake, 50 is an output shaft, and 52 is a kickdown drum.

Claims (1)

[Claims] 1. An input shaft into which the rotational power of the engine is input;
an output shaft that outputs rotational power to a drive shaft; and a friction engagement element that is operated by hydraulic pressure and selectively engages with an arbitrary rotating element to switch a gear ratio between the input shaft and the output shaft. In preparation, when the shift starts, the target rotation speed change rate that the rotating element should follow is set to a relatively large first value, and when the rotation speed of the rotating element reaches the value immediately before the end of the shift, the target rotation speed changes. the rotational speed is configured to switch to a second value smaller than the first value, and the actual rotational speed change rate of the rotating element follows the first value or the second value during gear shifting. In the vehicle automatic transmission that feedback-controls the hydraulic pressure supplied to the frictional engagement element, the rotational speed of the rotary element reaches the predetermined rotational speed and the target rotational speed change rate switches to the second value. 1. A method of controlling shift hydraulic pressure in an automatic transmission for a vehicle, characterized by temporarily reducing supply pressure to a frictional engagement element by a predetermined value.