JPH023768A - Speed change control device for automatic transmission - Google Patents

Abstract

PURPOSE:To prevent a rapid change of output torque by feedback-controlling an engaging transient pressure of oil first in execution of speed change and suspending a feedback control, when a transmission reaches the final period of speed change, thereafter controlling the engaging transient pressure of oil by a predetermined map. CONSTITUTION:When an automatic transmission engages its friction engaging unit, an engaging transient oil pressure control means inputs a rotary speed of a member of the friction engaging unit, changing the rotary speed by speed change execution, with an engine speed detected by an actual speed detecting means, and an engaging transient oil pressure is feedback-controlled in a manner wherein the member rotary speed is generated along a locus of the target rotary speed set by a decision means. Next, when a speed change final period detecting means detects a speed change to be placed in the final period, a feedback control is suspended, while the engaging transient oil pressure of the speed change final period is anticipation-controlled being based on a predetermined map. Thus surely reducing the oil pressure further in the speed change final period while feedback-controlling the engaging oil pressure, a speed change shock can be always decreased.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a shift control device for an automatic transmission.

[Conventional technology]

Conventionally, a gear transmission mechanism is provided with a gear transmission mechanism and a plurality of friction engagement devices, and the engagement state of the friction engagement device is selectively switched by the operation of a hydraulic control device to achieve one of a plurality of gears. Automatic transmissions configured to do this are already widely known. In addition, in order to reduce the shock during gear shifting in such an automatic transmission, a system is provided between the shift valve for changing gears and the frictional engagement device so that the transient hydraulic pressure at the time of engagement of the frictional engagement device can be adjusted. A device equipped with an accumulator is known.1 This accumulator has a cylinder-piston structure, and maintains the transient hydraulic pressure applied to the frictional engagement device at an almost constant hydraulic pressure for a predetermined period of time. Reduce shock. This constant oil pressure f&appropriate value changes depending on the engine torque input to the automatic transmission. Further, the value of this constant oil pressure can be controlled by changing the oil pressure (back pressure) applied to the back pressure chamber of the accumulator. Therefore, it is known that the hydraulic pressure applied to the back pressure chamber of the accumulator is electronically controlled, and as a result, the transient hydraulic pressure applied to the frictional engagement device is precisely controlled (for example, Japanese Patent Laid-Open No. 6-14
9657).

[Problem to be solved by the invention]

By the way, the applicant has previously proposed a method of feedback controlling the transient hydraulic pressure when the frictional engagement device is engaged, with the aim of reducing shift shock as well (Japanese Patent Application No. 1982-4).
4700, unknown). This feedback control first detects the rotational speed of a member whose rotational speed changes when a gear shift is executed, such as the turbine shaft in an automatic transmission, the drum of each clutch or brake, or the engine. This method feedback-controls the engagement transient oil pressure of the frictional engagement device in the automatic transmission so that the rotational speed changes along the trajectory of the target rotational speed that the member should follow after the gear change output. If such feedback control is adopted, the engagement transient oil pressure of the frictional engagement device will always bring the rotational speed of the member to the target rotational speed, regardless of vehicle-specific variations that occur during manufacturing or over time. The transmission speed is controlled so that it changes along the trajectory of the speed change, so that the optimum speed change transient state can always be obtained. However, when attempting to actually execute such feedback control, due to the response delay of the hydraulic control system,
To prevent sudden changes in output shaft torque (occurrence of shift shock) that cannot cope with sudden changes in the friction coefficient of a friction engagement device at the end of a shift and that occur at the moment when the friction engagement device finally engages. A problem occurred where it was not possible to

[Purpose of the invention]

The present invention has been made in view of these problems, and provides a shift for an automatic transmission that can constantly suppress sudden changes in output torque that occur at the end of a shift while feedback-controlling the engagement transient oil pressure. The purpose is to provide a control device.

[Means to solve the problem]

As summarized in FIG. 1, the present invention provides means for detecting the rotational speed of a member whose rotational speed changes when a gearshift is executed, and a trajectory of a target rotational speed that the member should follow after the gearshift is output. means for determining the rotational speed of the member, such that the rotational speed of the member changes along the trajectory of the target rotational speed;
means for feedback controlling the engagement transient hydraulic pressure of a frictional engagement device in an automatic transmission; means for detecting whether or not the gear shift has entered the final stage; The above object has been achieved by including means for stopping the feedback control of the hydraulic pressure and controlling the engagement transient hydraulic pressure at the end of the shift based on a predetermined map.

[Effect]

In the present invention, since the transient hydraulic pressure at the time of engagement of the frictional engagement device is feedback-controlled, it is possible to always obtain an ideal shift transient state regardless of vehicle-specific variations or changes over time. You will be able to do this. In addition, in the present invention, when performing feedback control of this engagement transient oil pressure, it is detected whether or not the shift has entered the final stage, and when it is detected that the shift has entered the final stage, this engagement transient Feedback control of the hydraulic pressure is stopped, and thereafter the engagement transient hydraulic pressure is (estimated) controlled according to a predetermined map. As a result, in the present invention, the friction coefficient in the automatic transmission is adjusted such that the rotational speed of the member whose rotational speed changes as a result of the execution of the gearshift changes along the locus of the target rotational speed from the initial stage to the middle stage of the gearshift. The engagement hydraulic pressure of the coupling device is feedback-controlled, and after the end of the shift is detected, the feedback control of the engagement transient hydraulic pressure is stopped, and the engagement transient hydraulic pressure is prospectively controlled according to a predetermined map. Therefore, the engagement transient oil pressure can be reliably lowered at the end of the shift, and the most ideal shift transient state can be obtained from the beginning to the end of the shift. Although the present invention does not limit how the predictive control at the end of the shift is performed, the map used in this predictive control may be based on, for example, the type of gear change (type of frictional engagement device) and the engine load. Based on this, the engagement hydraulic pressure is determined to be actively lowered.

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. In this embodiment, the back pressure of the accumulator is controlled in order to control the transient oil pressure when the frictional engagement device is engaged. Further, the turbine shaft is selected as the member whose rotational speed changes as the speed is changed. Feedback control of engagement transient oil pressure is
The actual turbine rotation speed NT is the turbine target rotation speed N
This is done by electronically controlling the duty solenoid (So) to vary along the trajectory of T o. The turbine target rotational speed N To is determined for each type of speed change according to the engine torque (or throttle opening). FIG. 2 shows an overall outline of a vehicle automatic transmission and engine to which this embodiment is applied. This automatic transmission includes a torque converter section 20 and an overdrive mechanism section 40 as its transmission sections.
and an underdrive mechanism section 60 with three forward stages and one reverse stage. The torque converter section 20 is of a well-known type and includes a pump 21, a turbine 22, a stator 23, and a lock-up clutch 24. The overdrive mechanism section 40 includes a set of planetary gears including a sun gear 43, a ring gear 44, a planetary pinion 42, and a carrier 41, and the rotational state of the planetary gears is controlled by a clutch CO, a brake Be, and a one-way clutch Fo. controlled by. The underdrive mechanism section 60 includes a common sun gear 6
1. Ring gear 62.63, planetary pinion 64.
2 consisting of 65 and carrier 66.67! The system is equipped with a 2 Mi planetary gear device, and the rotational state of the 2 Mi planetary gear device and the connection state with the overdrive mechanism are controlled by clutches C1, C2, brakes 81 to B3, and one-way clutches Fl, F2. There is. Since this transmission part itself is well known,
Regarding the concrete connection state of each component, only a skeleton diagram is shown in FIG. 2, and detailed explanation will be omitted. This automatic transmission includes a transmission section as described above,
and a computer (ECU) 84. The computer 84 includes a throttle sensor 80 that detects the throttle opening θ to reflect the output (torque) of the engine 1.
, a vehicle speed sensor (rotational speed sensor of the output shaft 70) 82 that detects the vehicle speed no. is input. The computer 84 controls the solenoid valves Sl, 32(
(for the shift valve) and SL (for the lock-up clutch), and performs a combination of engagement of each clutch, brake, etc. as shown in FIG. 3 to execute a gear shift. FIG. 4 shows the main parts of the hydraulic control circuit 86. In the figure, the symbol So is a duty solenoid, 108
is an accumulator control valve, 110 is a modulator valve, 112 is an accumulator, 114 is a shift valve, and 115 is a damper. In this figure, the brake B2 is used as a frictional engagement device.
are shown representatively. As is clear from Figure 3,
The brake B2 is a skew engagement device that is engaged when shifting from the first gear to the second gear. Line pressure PL is created by a well-known method using oil pressure generated by an oil pump (not shown) as a base pressure. This line pressure PL is the boat 11 of the modulator valve 110.
Applied to 0A. Modulator valve 110 receives this line pressure PL and generates a predetermined modulator pressure Pa in boat 110B using a well-known method. The duty solenoid So is this modulator pressure Pm
In response to this, a solenoid pressure E'S+ corresponding to the difference between the turbine rotational speed NT and the turbine target rotational speed N To is generated using a well-known method. That is, the times*iM degrees NT of the turbine 22 are input to the computer 84 as described above. This turbine speed NT is compared with a turbine target rotation speed NTO that is preset according to the engine torque and the type of speed change.For example, in the case of 1-2 speed change,
By executing the 1->2 shift, the turbine rotational speed NT decreases. If the turbine rotation speed NT is the target rotation distance NT
When it decreases earlier than O (when NT-NTo<O)
In this case, the gear shifting progresses too quickly, so the brake B
In order to reduce the engagement transient oil pressure of 2, this NT NT
A duty ratio command corresponding to o is applied to the duty solenoid So, and the duty solenoid So generates a solenoid pressure PS+ according to this duty ratio command using a well-known method. Note that in this example, when the due-eye ratio increases (10
0%), the generated solenoid pressure Psi becomes smaller. Further, reference numeral 115 in FIG. 4 is a damper for suppressing pulsating flow. This solenoid pressure PS+ is input to boat 108A of accumulator control valve 108. Accumulator control valve 108 controls line pressure PL+
and solenoid pressure PS from duty solenoid So
+ is used as an input signal, and the line pressure PL2 of the boat 108B is regulated to the accumulator back pressure Pac. In other words, the accumulator back pressure P, ac is basically the line pressure PL2 regulated by the line pressure PI,+ and the urging force of the spring 108C, and corrected by the solenoid pressure PS1 of the duty solenoid So. It is. When the computer 84 makes a shift decision (in this case, a shift decision from the first gear to the second gear), the solenoid valve S
1, the shift valve 114 is switched in a known manner and line pressure PL (Pao) begins to be supplied to the brake B2. Upon receiving this supply, the accumulator 11
The second piston 112A starts to rise. While the piston 112A is rising, the oil pressure (Pao) supplied to the brake B2 is maintained at a substantially constant oil pressure balanced with the downward biasing force of the spring 112B and the downward force acting on the piston 112A. It turns out. The force pushing the piston 112A downward is generated by the accumulator back pressure pac applied to the back pressure chamber 112C of the accumulator 112. Therefore, the accumulator back pressure pac is adjusted to the modulator valve 1 as described above.
10. By controlling via the duty solenoid So and the accumulator control valve 108, it is possible to arbitrarily control the transient oil pressure 2/0 when the brake B2 is engaged. As described above, the duty solenoid So is controlled depending on the difference between the turbine rotation speed NT and the turbine target rotation speed NTo. Speed NTo
It can be controlled by feedback to change along the line. In general, automatic transmissions depend on the characteristics of the hydraulic control system, engine characteristics, and gear ratio of the gear train.
Shift characteristics vary depending on the throttle opening. Therefore, feedback control of the engagement transient oil pressure as described above based on changes in the turbine rotational speed NTo during gear shifting is extremely effective in reducing shift shock. It is valid. However, this hydraulic control system always includes a response delay, and especially a sudden change in the output torque due to a change in the friction coefficient of the friction engagement device at the end of the shift (shift shock).
Therefore, as a qualitative tendency, the feedback control is stopped at the end of the shift, taking into account that the output torque at the end of the shift increases due to the dynamic friction coefficient and drag coefficient of the friction engagement device. , consider reducing the engagement transient oil pressure in a so-called "prospect" manner. At this time, the degree of decrease in the engagement transient oil pressure depends on the type of shift (
Specifically, the type of frictional engagement device involved in the gear shift),
For example, in the case of shifting from the first gear to the second gear, the frictional engagement device to be engaged is the brake B2 as shown in FIG. 3. Since the brake B2 is fixed to the housing,
No centrifugal hydraulic pressure is generated during engagement,
Therefore, there is no need to consider the influence of the centrifugal oil pressure on the engagement transient oil pressure at the end of the shift. On the other hand, in the case of shifting from second gear to third gear,
The frictional engagement device to be engaged is clutch C2 as shown in FIG. Since this clutch C2 starts rotating upon engagement, centrifugal oil pressure is generated by this rotation. Therefore, the engagement pressure at the end of the shift becomes larger by this centrifugal oil pressure than in the case of shifting from the first gear to the second gear. Conversely, in order to reduce the engagement transient oil pressure at the end of the shift and alleviate the shift shock, it is necessary to
In the case of shifting from the first gear to the third gear, a larger oil pressure drop is required than in the case of shifting from the first gear to the second gear. Furthermore, even in the same type of gear shifting, the amount of energy that the frictional engagement device should absorb differs depending on the engine torque (engine load). , it is also necessary to consider the engine torque factor. In addition, in this embodiment, it is determined whether or not the gear shift has entered the final stage.
As described later, the determination is made based on whether the difference between the synchronous rotational speed and the actual rotational speed of the turbine reaches a predetermined value, but even if the type of gearshift is the same, the turbine rotation before and after the gearshift changes depending on the engine torque. Since the amount of change in speed is different, it is also necessary to change the rotational speed difference between the turbine synchronous rotational speed and the actual rotational speed for determining the end of the shift depending on the engine torque. FIG. 5 shows the control procedure in this embodiment. At step 202, a gear shift determination is made according to the vehicle speed and throttle opening. As a result, a predetermined shift output is output in step 204. In step 206, an inertia phase (substantial shift start, that is, a decrease in the rotational speed NTo of the turbine 22) is detected. When the inertia phase is detected, the duty output value D+ to the duty solenoid So is calculated in step 208, and feedback control of the engagement transient oil pressure is executed.The duty output value Di is calculated as described above. Target rotational speed NT and actual rotational distance NT of the turbine 22
This is done based on the difference with o. After the feedback control has been executed in this manner, the end of the shift is detected in step 210. This detection determines whether the turbine rotational speed NT has become close to the value obtained by multiplying the rotational speed no of the output shaft 70 of the automatic transmission by the gear ratio iH of the newly formed gear stage (turbine synchronous rotational speed). Performed by making a judgment, specifically, NT
On. The predetermined value for this difference ΔN, which is determined by determining whether the difference ΔN between It has been decided. An example of this is shown in the left column of FIGS. 6(A) and (B). In FIG. 6, (A) shows an example of a 1->2 speed change, and (B) shows an example of a 2->3 speed change. When the end of the shift is detected in step 210, the process proceeds to step 212, where prospective control of the duty ratio DE as shown in the right column of FIGS. 6(A) and 6(B) is performed. The reason why the duty ratio Dε in this predictive control is determined for each type of speed change and throttle opening is as described above. Thereby, the engagement transient oil pressure can be reliably reduced at the end of the shift, and shift shock can be reduced. This situation is shown in FIGS. 7 and 8. In the example of FIG. 7,
The transient oil pressure during engagement from the start of the inertia phase to the completion of the shift is all determined by feedback control. Therefore, it is not possible to follow the sudden change in the friction coefficient at the end of the shift, and a sudden torque fluctuation occurs at point A. On the other hand, FIG. 8 shows the speed change characteristics in the above example,
Since the oil pressure is lowered from point B to a predetermined level in anticipation of an increase in the friction coefficient at the end of the shift, it is possible to suppress a sudden increase in torque. Note that the duty ratio at this point B corresponds to the duty ratio DE in FIG. 6. In step 214, complete completion of the gear shift is detected based on whether the difference ΔN has become smaller than 50, and the predictive control is ended. Note that the present invention does not limit how the end of the shift is determined. Further, in the above embodiment, the accumulator back pressure is regulated by the duty solenoid, but this may naturally be a linear solenoid or the like.

【Effect of the invention】

As explained above, according to the present invention, while performing feedback control of the engagement oil pressure, it is possible to always further reduce the oil pressure at the end of the shift, and shift shock can always be reduced favorably. An excellent effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the gist of the present invention, and FIG. 2 is a block diagram showing the gist of the present invention.
A schematic block diagram of a vehicle automatic transmission to which an embodiment of the present invention is applied; FIG. 3 is a diagram showing the operating state of the frictional engagement device in the automatic transmission; FIG. 4 is a diagram showing the operating state of the frictional engagement device in the automatic transmission; Fig. 5 is a flowchart showing the control procedure; Fig. 6 shows ΔN for determining the end of shift and the duty ratio DE after determining the end of shift. 7 is a shift characteristic diagram when feedback control is executed until the shift is completed, and FIG. 8 is a shift characteristic diagram when feedback control is stopped from the end of shift and prospective control is executed. . 108...Accumulator control valve, 11
2...Accumulator, 114...Shift valve, S□...Duty solenoid, PS,...Solenoid pressure, NT...Turbine rotation speed, NTO...Turbine blind rotation speed, Di・・Duty ratio during feedback control, DE
...Duty ratio during open control.

Claims (1)

[Claims] (1) means for detecting the rotational speed of a member whose rotational speed changes due to execution of a gearshift; means for determining a trajectory of a target rotational speed that the member should follow after outputting the gearshift; and rotation of the member. means for feedback controlling the engagement transient oil pressure of the frictional engagement device in the automatic transmission so that the speed changes along the trajectory of the target rotational speed; and means for detecting whether or not the shifting has entered the final stage. , means for stopping the feedback control of the engagement transient oil pressure when it is detected that the shift has entered the final stage, and controlling the engagement transient oil pressure at the final stage of the shift based on a predetermined map; A shift control device for an automatic transmission, characterized by comprising: