JPH081244B2 - Automatic transmission - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic transmission such as a vehicle, and more particularly to an automatic transmission intended to reduce shift shock.

(Prior Art) Generally, in an automatic transmission having a plurality of gears, the gear shifting operation is performed while the power from the engine is being transmitted to the drive system, and the gear ratio is switched stepwise. Due to the torque fluctuation of the drive system accompanying the change, acceleration change is applied to the vehicle body, and a so-called shift shock is felt to some extent. Since such a shift shock deteriorates the driving feeling, it is not preferable, and it is desired to reduce the shock as much as possible.

FIGS. 5 and 6 are diagrams showing torque flows of the second speed and the third speed of a general automatic transmission, respectively.

The solid line in the figure indicates the system path involved in torque transmission,
Dotted lines indicate lines not involved. Further, black circles indicate friction elements in the engaged state, and white circles indicate friction elements in the released state.

In FIG. 5, the torque transmission of the second speed is transmitted through the system path from the input shaft 100, the rear planetary gear 101 and the output shaft 102. Further, the reaction torque Tx from the band brake 103 in the engaged state is transmitted to the front planetary gear 104 → forward clutch 105 → forward one-way clutch 106 → rear planetary gear 101 → output shaft 102. Therefore, the output torque of the engine 102 is calculated by adding the input torque Tin from the engine and the reaction torque Tx to the output shaft 102.
out (Tout = Tx + Tin) appears, and the torque is being increased according to the gear ratio of the second speed.

In FIG. 6, the torque transmission of the third speed is transmitted through the system path from the input shaft 100 to the output shaft 102 through the rear planetary gear 101, and the high clutch 107 in the engaged state from the input shaft 100 to the front planetary gear. Lee gear 104 → forward clutch 105 → forward one-way clutch 106
-> Rear planetary gear 101-> Output shaft 102 is also transmitted via two paths via a path. That is, since the input torque Tin from the engine is transmitted through the two system paths, the torque Tout transmitted to the output shaft 102 is
The torques Ta and Tb shared by the two paths are added together. For example, if the gear ratio of the third speed is 1,000, Tin = Ta
It becomes + Tb, and the input torques Tin and Tout match.

Switching power trains like this (2nd speed → 3
Speed), the band brake 103 in the engaged state at the 2nd speed.
The high clutch 107 is changed to the engaged state while releasing the torque, and the torque flow switching shown in FIGS. 5 and 6 is performed. Depending on the release and engagement timing of the band brake 103 and the high clutch 107, the torque flow may be changed. There is a possibility that a large shift shock may occur due to lack of smoothness in the switching.

An example of a conventional automatic transmission that reduces this kind of shift shock is disclosed in Japanese Patent Application Laid-Open No. 61-31746. In this device, the disengagement timing of one friction element (hereinafter, referred to as disengagement side element) that changes from the engaged state to the disengaged state at the time of shifting is set as follows. That is, the other friction element (hereinafter referred to as the fastening side element), which reversely changes from the released state to the fastening state in cooperation with the operation of the one friction element, is in the semi-connected state, and the fastening side element is used. The predetermined time tx until a slight load starts to be applied to the engine is set in advance, and the release timing is set when the time tx elapses.

(Problems to be Solved by the Invention) However, in such a conventional method, since the release timing of the release side element is set to a single value for a certain time tx, the operating state of the engine and the automatic transmission are changed. When the characteristics of the torque converter and friction elements of the machine change, there will be a gap between the actual required optimum release timing (hereinafter, actual timing). For example, if the actual timing is delayed, The release side element is released before the transmission torque of the engagement side element is sufficiently increased, and in this case, the engine is idle.

In addition, if the actual timing is advanced, the engagement state of the disengagement side element continues to continue even after the transmission torque of the engagement side element has sufficiently increased, and in this case, an interlock occurs and a large pull-in occurs. There is a problem in that torque is generated and an uncomfortable shift shock is felt.

(Object of the Invention) The present invention has been made in view of such problems, and detects the actual shaft torque of the input shaft and the output shaft, and sets the release timing from the change of the shaft torque. , Aiming to match the actual timing with the release timing,
The purpose is to reduce shift shock regardless of changes in the operating state of the engine and changes in the characteristics of the automatic transmission.

(Means for Solving Problems) In order to achieve the above object, an automatic transmission according to the present invention has an input shaft that is rotationally driven by an engine, an output shaft that is coupled to a drive system, and an input shaft and an output shaft that are connected to each other. A gear transmission mechanism interposed between them, which is capable of selecting one of a plurality of gear ratios, and a friction engagement mechanism which selectively engages and releases a plurality of friction elements to select the gear ratio, When a gear shift command for switching to a gear ratio different from the current one is input, among at least two friction elements of the friction engagement mechanism, one friction element moves from the released state to the engaged state, In the automatic transmission that switches the gear ratio between the input shaft and the output shaft to a gear ratio different from the present, the other friction element in the engaged state is released according to the timing signal, and detects the shaft torque of the input shaft. Enter A force shaft torque detecting means, an output shaft torque detecting means for detecting the shaft torque of the output shaft, and a gear ratio different from the present one are switched based on the detected input shaft torque and the gear ratio different from the present one. And a signal generating means for generating the timing signal when the detected output shaft torque reaches the target output shaft torque.

(Operation) In the present invention, when a gear shift command for instructing switching to a gear ratio different from the present is input, a target output shaft torque is calculated based on the input shaft torque and the gear ratio different from the present, and this target output is calculated. When the actual output shaft torque reaches the shaft torque, the release side element is released.

Here, the output shaft torque after completion of the shift is a torque conversion of the input shaft torque according to the gear ratio of the shift stage selected by the engagement side element, and at this time, the release side element is in a completely released state. . Therefore, when the actual output shaft torque and the target output shaft torque are substantially the same, the torque on the engagement side element is almost 100%, and the torque on the release side element is almost 0%.
%. That is, when this coincidence is the optimum actual timing for releasing the release side element, by setting the release timing based on the actual input shaft torque or output shaft torque as in the present invention, It is possible to match the timing and the release timing, regardless of the operating state of the engine and the characteristic change of the automatic transmission,
Shift shock can be reduced.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

1 to 4 are views showing an embodiment of an automatic transmission according to the present invention, which is an example applied to an electronically controlled automatic transmission having four forward gears and one reverse gear.

First, the configuration will be described. In FIG. 1, reference numeral 1 denotes an engine, and the engine 1 generates a driving force according to an operation amount of a throttle pedal (not shown), and the driving force rotationally drives a crankshaft (not shown). Further, the rotation speed of the crankshaft of the engine 1, that is, the engine rotation speed Ne is detected by the engine rotation sensor 2.

3 is an automatic transmission, and the automatic transmission 3 is composed of a torque converter 4 and a transmission 5,
The transmission 5 has a rotation speed of an input shaft 10 described later.
An input shaft rotation sensor 6 for detecting Nt and a torque sensor (output shaft torque detecting means) 8 for detecting a shaft torque (output shaft torque To) of the output shaft 7 are provided.

 The automatic transmission 3 is shown in detail as shown in FIG.

In FIG. 2, a torque converter 4 includes a pump impeller 9 coupled to a crankshaft of an engine and rotating integrally with the crankshaft, and an input shaft of a transmission 5.
10 has a turbine impeller 11 spline-fitted to 10 and a stator 13 integrally fixed to the converter housing case 12, and when the pump impeller 9 is rotationally driven by the driving force of the engine, The driving force of the engine is transmitted from the turbine impeller 11 to the input shaft 10 via the fluid.

The transmission 5 has the above-mentioned input shaft 10 and an output shaft 7 connected to a drive system including a drive shaft, a final gear, drive wheels and the like (not shown), and between the input shaft 10 and the output shaft 7. A gear transmission mechanism 15 is interposed between the gears. The gear transmission mechanism 15 has, for example, two sets of planetary gears, that is, a front planetary gear 16 and a rear planetary gear 17, and each planetary gear is provided at the center as already known. Sun gears 16a, 17a, and a plurality of pinion gears 16b, 17b meshing with the sun gears,
Planet carriers 16c and 17c that support the pinion gear,
Ring gears 16d and 17d, which are provided on the outer periphery by meshing with the planet carriers 16c and 17c, fix one of the sun gear, planet carrier and ring gear, and drive the other two. By connecting to the driven side, the rotational torque transmitted from the driving side to the driven side can be reduced or increased in multiple steps. Further, the degree of decrease or increase is determined by the gear ratio obtained from the number of teeth of the sun gear and the ring gear, the rotation speed of the sun gear, etc., and by selectively fixing any one of the three, one of the plurality of gear ratios is selected. . Incidentally, the gear ratio in this embodiment is 2.785 for the first speed (hereinafter referred to as R ₁ ), 1.545 for the second speed (hereinafter referred to as R ₂ ), 1.000 for the third speed (hereinafter referred to as R ₃ ), 4
The speed is set to 0.694 (hereinafter R ₄ ) and the reverse is set to 2.272 (hereinafter R _R ).

The selection of the gear ratio is performed by the friction engagement mechanism 18, and the friction engagement mechanism 18 has a plurality of friction elements. This friction element is, for example, a band brake 19 or a reverse clutch.
20, high clutch 21, forward clutch 22, overrun clutch 23, forward one-way clutch 24, low one-way clutch 25, low & reverse brake 26, etc. The fixed parts of the gear 16 and the rear planetary gear 17 are switched to achieve one of the above-mentioned plurality of gear ratios.

Here, the plurality of friction elements described above are configured such that, during a shift change transition, while one friction element shifts from release to engagement, the other friction element operates relatively from engagement to release. Includes a pair of friction elements in a relationship. For example, in the case of the present embodiment, the relationship between the high clutch (one friction element) 21 and the band brake (the other friction element) 19 at the time of shifting from the second speed to the third speed is that.
The band brake 19 is released at an appropriate timing while 21 shifts to the engagement. If the release timing is improper, the engine may be blown or the interlock may be generated to cause a shift shock as described above, which is not preferable.

In the present embodiment, as will be described later in detail, the release timing is always set to the optimum value to prevent the engine from being blown, the interlock, or the like.

The friction engagement mechanism 18 described above selectively engages and disengages a plurality of friction elements by the hydraulic pressure supplied from the hydraulic control mechanism 27, and the hydraulic control mechanism 27 uses a shift control device described later.
The hydraulic path to each friction element is switched according to the gear shift command signal from 35.

Note that S _A and S _{B in} FIG. 2 show a part of the shift command signal. When S _A changes from “H” to “L”, the band brake 19 changes from engagement to release. , S _B changes from “L” to “H”, the high clutch 21 changes from release to engagement.

The input shaft rotation sensor 6 is fixed to the transmission case 28, and the input shaft rotation sensor 6 is arranged with a predetermined gap from the outer peripheral surface of the input shaft 10. The outer peripheral surface of the input shaft 10 is formed with irregularities such as serrations, and the input shaft rotation sensor 6 captures the movement of the irregularities due to the rotation of the input shaft 10 as a change in magnetic flux, and the change in the magnetic flux is detected by an electric signal. To convert the rotation speed Nt of the input shaft 10 into a value.

Further, the torque sensor 8 is fixed to the rear extension 29, and a known magnetostrictive torque sensor is used for the torque sensor 8, for example. That is, the torque sensor 8 includes a pair of exciting coils 30 and 30 'provided with a gap along the circumferential direction of the outer peripheral surface of the output shaft 7.
And a pair of groove bands 31, 31 'formed of a large number of grooves formed on the outer peripheral surface of the output shaft 7, and the direction of the grooves forming the pair of groove bands 31, 31' is the direction of the output shaft 7. The groove direction is symmetrical between the pair of groove bands 31, 31 'while forming a predetermined angle with respect to the central axis. Such a torque sensor 8 is
When a slight torsional deformation occurs in the output shaft 7 due to a change in the shaft torque, the pair of groove bands 31, 31 ′ increases the angle between the direction of each groove and the central axis, increasing one and decreasing the other. As a result, the magnetic permeability of one groove band side that increases the angle with the central axis increases and the magnetic permeability of the other groove band side that decreases the angle with the central axis increases due to this change. Permeability decreases. Therefore, when a magnetic flux is supplied from each of the exciting coils 30 and 30 'to the pair of groove zones 31 and 31', a current difference occurs in the exciting current flowing through the exciting coils 30 and 30 'according to the change in the magnetic permeability. Since this current difference is proportional to the magnitude of torsional deformation of the output shaft 7, the output shaft torque To can be detected from the current difference.

Again in FIG. 1, reference numeral 33 is an input shaft torque calculation device, and the input shaft torque calculation device 33 is composed of, for example, a microcomputer and the like, and data corresponding to the torque capacity coefficient CF shown in the characteristic diagram of FIG. Data corresponding to the torque ratio TR before and after the torque converter is stored as a table map in the internal memory. Input shaft torque calculator
33 executes the following processing according to a predetermined program.
That is, the speed ratio e before and after the torque converter 4 is calculated according to the following equation, The values of CF and TR corresponding to the obtained speed ratio e are looked up from the above table map.

Next, the input torque Ti of the torque converter is calculated according to the following equation, Ti = CF × n _e ² ... where CF is the lookup value, and the axial torque of the input shaft 10, that is, the input shaft torque Tt, according to the following equation. Is calculated.

Therefore, the input shaft torque calculation device 33, the engine rotation sensor 2 and the input shaft rotation sensor 6 described above constitute an input shaft torque detecting means.

Reference numeral 34 denotes a release timing setting device as a calculation means and a signal generation means. The release timing setting device 34 is composed of a microcomputer or the like, and has a torque ratio calculation unit.
It has 34a and a timing setting unit 34b. The torque ratio calculator 34a calculates the inter-shaft torque ratio TR 'including the speed change ratio between the input shaft 10 and the output shaft 7 at that time according to the input shaft torque Tt and the output shaft torque To. That is, the input axis
The torque transmitted from 10 to the output shaft 7 is increased / decreased by a predetermined ratio according to the gear ratio at that time. For example, in the second speed, the input shaft torque Tt multiplied by R ₂ (R ₂ = 1.543) Output shaft torque becomes To, and when in 3rd speed, Tt is set to R ₃ (R ₃
= 1.000) multiplied by that becomes To. Therefore, after the gear ratio is changed to a value different from the present, TR 'becomes a size that matches the value of the gear ratio at that time, and further, during a gear change transition (for example, 2nd gear → In 3rd speed), TR 'changes from the value corresponding to R ₂ to the value corresponding to R ₃ , and when R ₃ and TR' match, the conversion point from the so-called torque phase to inertia phase is reached. Becomes That is, at this conversion point, the torque share of the disengagement side element (for example, the band brake 19) becomes "0", so the conversion timing may be determined by detecting this conversion point.

From such a point of view, in the timing setting unit 34b, T
While monitoring o, TR 'during the calculated shift transition
And the destination Ri (however, i = 1, 2, 3, or R)
Based on the above, a conversion point at which the target output shaft torque Tt × Ri = To and the actual output shaft torque To match is detected, and a release timing (timing signal) signal TMG is output at the time of detection.

Since the release element operates by hydraulic pressure, it is considered that there is a slight response delay. Therefore, as shown in the following equation, the response delay α may be taken into consideration and correction may be made to accelerate the output of TMG.

Tt × Ri = To + α …… Alternatively, when the torsional rigidity of the drive system is low or the response speed of the release element is fast, TMG can be calculated as shown in the following formula.
The output of may be corrected so as to be delayed.

Tt × Ri + α ′ = To ...... However, α ′: the correction coefficient 35 is a gear shift control device, and the gear shift control device 35 is composed of a microcomputer or the like, and is based on various information such as the throttle opening and the vehicle speed. The optimum shift point for the running state is finely determined, and a shift command signal is output to the hydraulic control mechanism 27 of the transmission 5 as needed. For example, when the running state of the vehicle reaches the upshift point from the 2nd speed to the 3rd speed, S _B which is a part of the shift command signal is set to “L”.
Changes to "H" level to start shifting, and
When TMG is input from the release timing setting device 34, S _A
Is changed from “H” to “L” level. The shift control device 35 outputs shift information including the gear ratio Ri of the shift destination to the release timing setting device 34.

Next, the operation will be described with reference to the timing chart showing the shift operation timing from the second speed to the third speed in FIG.

First, at time t ₀ , the running state changes and the second speed → 3
When the upshift point to high speed is reached, the shift control device 35
Changes S _B from “L” to “H” level to command the start of gear shifting operation. The high clutch 21 starts operating from the disengaged state in the engagement direction according to S _B , and gradually backlashes. While closing this backlash (t ₀ −
At t ₁ ), the gear ratio remains at the second speed before switching, that is, To during that time indicates the magnitude obtained by Tt × R ₂ . In the case of upshifting between t _{0 and} t ₁ ,
Normally, the throttle pedal is depressed and both Ne and Nt tend to rise, but for convenience of explanation, it is assumed that these are constant, and the rotation speed of the output shaft 7 does not change. That is, it is illustrated that only the amount of change in torque due to the change in gear ratio is shown. Therefore, it should be recognized that it does not correspond exactly to the actual driving state.

At time t ₁ , the backlash of the high clutch 21 becomes “0”, and when the engagement is started, the transmission torque TC _B of the high clutch 21 increases as the engagement pressure increases, while the transmission of the band brake 19 increases. The torque TC _A decreases and enters the so-called torque phase. During this torque phase,
To is gradually changed in the decreasing direction with decreasing TC _A.

At time t ₂ , To decreases and is shown by the arrow in the figure.
When the point of To = Tt × R ₃ is reached, that is, R ₃ = 1.000
Since it is, if they match in this case the To = Tt, TC _B is 3
Satisfy the torque sharing in speed, whereas, TC _A is the torque allotment "0". Therefore, TMG is output from the release timing setting device 34 at the point of To = Tt at which this torque phase ends, and the shift control device 35 receives TMG and changes S _A to “H” →
Change to "L". As a result, the band brake 19 is S _A
, The torque capacity MTC _A of the band brake 19 becomes “0” and the band brake 19 is disconnected.

Between times t ₂ -t _3, only the torque margin A torque capacity MTC _B of the high clutch 21, Nt is pulled to release the amount of work required for the pull-down as the inertia torque INT. That is, during the time t ₂ -t ₃ , it acts as a so-called inertia phase, during which INT is added to To and temporarily rises to To = Tt × Ri + INT.

At time t ₃ , when INT is completely released, TC _B becomes 3
The speed becomes a value corresponding to the assigned torque, and To becomes a value of Tt × R ₃ along with this, and the speed is stabilized, and the shift operation is completed.

Thus, in this embodiment, the engine speed Ne, the input shaft speed Nt, and the torque capacity coefficient of the torque converter 4 are calculated.
Based on CF and the torque ratio TR before and after the torque converter, calculate the input shaft torque Tt during the shift transition period, find the value (that is, the target output shaft torque) that is the product of this Tt and the shift destination Ri, and obtain this value. The time when the output shaft torque To reaches is set as the release timing of the release side element.
Therefore, since the release side element is released based on the actual change of the input shaft torque Tt, the control accuracy is improved,
When the torque sharing of the disengagement side element becomes "0", this can be appropriately disengaged. As a result, it is possible to avoid idling of the engine and interlock, and it is possible to reduce shift shock regardless of the operating state of the engine and changes in the characteristics of the automatic transmission.

(Effect) According to the present invention, the actual shaft torque of the input shaft and the output shaft is detected, and the release timing of the release element is set based on the change in the shaft torque. It is possible to adjust the release timing to the optimum timing that becomes "," and it is possible to reduce the shift shock regardless of changes in the operating state of the engine and changes in the characteristics of the automatic transmission.

[Brief description of drawings]

1 to 4 show an embodiment of an automatic transmission according to the present invention, FIG. 1 is a diagram showing the overall configuration thereof, and FIG. 2 is a diagram showing a specific configuration of the automatic transmission. FIG. 3 is a characteristic diagram showing various characteristics of the torque converter, FIG. 4 is a timing chart for explaining its operation, and FIGS. 5 and 6 are D2 speed and D3 speed for explaining conventional problems. It is a figure which shows the torque flow of. 7 ... Output shaft, 8 ... Torque sensor (output shaft torque detecting means), 10 ... Input shaft, 15 ... Gear shifting mechanism, 18 ... Friction engagement mechanism, 19 ... Band brake (other friction element) ), 21 …… High clutch (one friction element), 2 ……
Engine rotation sensor (input shaft torque detection means), 6 ...
Input shaft rotation sensor (input shaft torque detection means), 33 ... Input shaft torque calculation device (input shaft torque detection means), 34 ...
Release timing setting device (calculation means, signal generation means).

Claims (1)

[Claims] 1. An input shaft rotatably driven by an engine,
An output shaft coupled to the drive system, a gear transmission mechanism interposed between the input shaft and the output shaft and capable of selecting one of a plurality of gear ratios, and a plurality of friction elements selectively engaging and releasing. And a friction engagement mechanism for selecting the gear ratio, and when a gear shift command for instructing switching to a gear ratio different from the current one is input, at least two friction elements of the friction engagement mechanism are While one friction element shifts from the disengaged state to the engaged state, the other friction element in the engaged state is disengaged in accordance with the timing signal, and the gear ratio between the input shaft and the output shaft is changed from the current gear ratio. In an automatic transmission that switches to a ratio, an input shaft torque detecting means for detecting a shaft torque of the input shaft, an output shaft torque detecting means for detecting a shaft torque of the output shaft, a detected input shaft torque and the present Calculating means for calculating a target output shaft torque when the gear ratio is changed to a gear ratio different from the present based on a different gear ratio; and the timing signal when the detected output shaft torque reaches the target output shaft torque. And a signal generating means for generating the.