JP2001090827A - Shift control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a stable vehicular behavoir by setting a speed change time longer than a normal mode time intentionally, at the shift up time following to the release of a shift down. SOLUTION: This shift control device which can recognize the running state of a self car frontside and carry out the shift change of an automatic transmission based on a preview information when a speed reduction is necessary has a micro-computer 1 which can indicate a shift down based on the preview information when it is judged that the running state of the self car frontside is the state to reduce the speed and indicate the release of the shift down when it is judged that it is not the state to reduce the speed and TCU 4 for controlling the engagement of an engaging element in the automatic transmission 8. Here, TCU 4 controls the engagement so that a torque shock becomes smaller than the usual shift up time at the shift up time by the indication of the release of the shift down from the micro-computer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shift control device for instructing a shift-down of an automatic transmission in accordance with a running condition in front of a host vehicle, and more particularly to a shift control device which automatically shifts down in a condition requiring deceleration. The present invention relates to engagement control for downshifting.

[0002]

2. Description of the Related Art There has been proposed a technique for grasping a running condition ahead of a vehicle based on navigation information and preview information obtained from a preview sensor, and decelerating by downshifting as necessary. For example, JP-A-8-20
Japanese Patent Application Laid-Open No. 2989 and Japanese Patent Application Laid-Open No. HEI 8-194886 disclose that if the road ahead of the vehicle is curved, the vehicle speed when entering the curved road is too high, that is, if it is determined that the vehicle is overspeeding, A technique for executing a downshift before entering a curve is disclosed. By decelerating in advance just before a curve in this way, it is possible to realize good curve running without giving the driver a feeling of strangeness.

[0003]

In the above prior art, when it is determined that the current vehicle speed is excessive with respect to the radius of curvature of the curve, deceleration is automatically performed by downshifting regardless of the driver's intention. Will be Then, in a driving situation in which the deceleration can be released, the downshift is released, so that the upshift may occur automatically. If this shift-up occurs when the vehicle is traveling on a curve or on a road surface having a small road friction coefficient μ (hereinafter referred to as “road surface μ”) (for example, a snow-covered road surface), the vehicle behavior becomes unstable due to the shift-up. There is a possibility that it will become.

Accordingly, an object of the present invention is to provide a shift-up which can maintain a stable vehicle behavior by intentionally setting a shift time in a shift-up associated with the release of the shift-down, as compared with that in the normal mode. It is to do.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention recognizes a running situation ahead of a vehicle based on preview information and, when deceleration is necessary, performs a shift change of an automatic transmission. The shift control device performs shift down when it is determined based on the preview information that the traveling situation ahead of the vehicle is in a situation to be decelerated, and shifts when it is determined that the situation to be decelerated is no longer present. There are instructing means for instructing release of the down, and control means for performing engagement control of an engaging element in the automatic transmission. Here, when upshifting is performed according to an instruction to cancel downshifting from the instructing unit, the control unit performs engagement control such that torque shock is smaller than during normal upshifting.

[0006] Preferably, the instructing means instructs a downshift when it is determined that the current vehicle speed is excessive with respect to a radius of curvature of a curve existing in front of the own vehicle. When it is determined that the vehicle should be decelerated based on the positional relationship with the preceding vehicle existing in front of the own vehicle, it is desirable to instruct a downshift.

When the control means shifts up in response to an instruction to cancel downshifting from the instructing means, it is desirable to perform engagement control such that the shift time is longer than a normal shift-up time.

The instruction means may calculate a road surface μ of a road on which the vehicle is traveling. in this case,
In the case where the control means shifts up according to an instruction to cancel downshifting from the instruction means, it is preferable to perform engagement control such that the smaller the road surface μ, the longer the shift time.

[0009]

FIG. 1 is a block diagram showing the overall configuration of a transmission system according to this embodiment. The microcomputer 1 transmits to the microcomputer 1 the preview sensor information obtained from the preview sensor 2, the navigation information obtained from the navigation unit 3, and the shift signal indicating the current set shift speed which is output information from the transmission control unit (TCU) 4. P has been entered. The microcomputer 1 recognizes a running situation including a situation in front of the own vehicle, a running state of the own vehicle, a road surface state (road surface μ), and the like based on the various input information including the above. Then, the microcomputer 1 sends an instruction signal DO to the TCU 4 to decelerate according to the recognition result.
WN and TRGT are output.

[0010] The preview sensor 2 is a sensor that outputs the running situation ahead of the vehicle as preview sensor information. In the present embodiment, a pair of C
A well-known stereo image processing device including a CD camera and an image processing system is used. Based on a pair of captured images obtained from each CCD camera, it is possible to obtain three-dimensional position information including the distance to an object (preceding vehicle or road shape) existing ahead. The preview sensor 2
Alternatively, a monocular camera, a sensor using a millimeter wave or a laser wave, or a sensor using them in combination may be used in addition to the stereo image processing apparatus. Navigation unit 3
Outputs the navigation information including the position of the vehicle, the traveling direction, the road shape, and the like by using the GPS technology together with the road map information stored in a storage medium such as a CD-ROM or a DVD. The microcomputer 1 matches the preview sensor information from the preview sensor 2 with the navigation information from the navigation unit 3 and uses the matched information as “preview information” (information to be recognized as a driving situation). Thus, the reliability of the recognition of the running situation ahead of the vehicle is ensured. The vehicle speed sensor 5 and the throttle opening sensor 6 are well-known sensors used for calculating the vehicle speed υ and the throttle opening θ, respectively.

FIG. 2 shows an example of an automatic transmission (hereinafter referred to as A).
It is a figure showing the schematic structure of 8). The driving force from the crankshaft 19 of the engine is transmitted to the turbine shaft 21 via the torque converter 20. A turbine shaft 21, which is an input shaft of the transmission, is connected to a sun gear of a rear planetary 22. on the other hand,
Reduction drive shaft 2 which is the output shaft of the transmission
2 is connected to a ring gear of the front planetary 11 and a planetary carrier of the rear planetary 12.
Each member (sun gear, planetary carrier, ring gear) of the two planetary gears 11 and 12 has three multi-plate clutches (reverse clutch 1) as shown in the figure.
3, high clutch 15, low clutch 16), two multi-plate brakes (2 & 4 brake 14, low & reverse brake 17), and low one-way clutch 18. These engagement elements (clutch, brake) are selectively engaged or disengaged according to the shift speed. As a result, the transmission can perform four forward speeds and one reverse speed.

FIG. 3 is a table showing the relationship between the shift position and the engagement state of the engagement element in the AT 8 having the above configuration. In this table, a circle indicates that the corresponding engaging element is engaged, and a blank indicates that it is released. Further, the mark ◎ indicates that the engagement is performed only during the corresponding driving. In this transmission, except for the shift between the first and second speeds, the clutch to clutch (Clutch to
Clutch) gear shifting is performed. On the other hand, in the shift between the first and second speeds in which the low one-way clutch 18 operates, the shift is achieved only by the engagement control of the 2 & 4 brake 14. TCU4
Outputs an engagement control signal for setting the gear position of the AT 8 to the hydraulic control circuit 7. The hydraulic control circuit 7 activates each solenoid constituting the hydraulic control mechanism 8a in the AT 8 according to an instruction by the engagement control signal. Thereby, each friction engagement element (clutch or brake) constituting the friction engagement mechanism 8b in the AT 8 is engaged / released, and the AT 8
8 is a gear position indicated by the TCU 4 (for example,
Gear, reverse gear).

FIG. 5 is a flowchart showing a shift control procedure performed in the TCU 4. First, in step 51, the TCU 4 reads the downshift instruction signal DOWN from the microcomputer 1, and determines whether or not this instruction signal DOWN is at the "1" level, that is, whether or not downshift execution is instructed. . The shift-down instruction signal DOWN is normally maintained at the "0" level, and is set to the "1" level only when the own vehicle needs to be decelerated due to the curvature radius of the curve and the positional relationship with the preceding vehicle. As long as the downshift instruction signal DOWN is “0”, the shift setting in the normal mode in step 52 is performed. In the normal mode, as shown in FIG. 6, the gear stage GR is set by referring to a shift map based on the vehicle speed υ and the throttle opening θ. In step 53 following step 52, it is determined from the shift map reference result whether it is necessary to perform a shift change by releasing the downshift mode. Unless immediately after the level of the downshift instruction signal DOWN changes from "1" to "0", that is, in a situation where the normal shift control is continuously performed, the process proceeds from step 53 to step 56. The TCU 4 outputs an engagement control signal to the hydraulic control circuit 7 to execute normal hydraulic control. FIG. 7 is a schematic transition diagram of the release hydraulic pressure and the engagement hydraulic pressure at the time of a shift change. At the time of a normal shift change, a control signal is output to the hydraulic control circuit 7 so as to have a hydraulic pattern as indicated by a solid line in FIG.

On the other hand, if an affirmative determination is made in step 53, that is, if the upshift is caused by the release of the downshift mode, the process proceeds to step 54, where the hydraulic control during the downshift release is executed (step 54). . In this case, the engagement side hydraulic pressure is performed according to a special hydraulic pattern different from that at the time of a normal shift change. That is, as shown by the dotted line in FIG. 7, the engagement side hydraulic pressure in the inertia phase control is set to a value lower than that in the normal hydraulic pressure control (others are the same as those in the normal state).

If the instruction signal DOWN from the microcomputer 1 is "1", that is, if downshift is instructed, the TCU 4 proceeds from step 51 to step 55. In this case, the shift setting in the normal mode is temporarily interrupted, and the shift setting in the downshift mode is performed. That is, the gear GR is set to the target gear TR indicated by the microcomputer 1.
GT is forcibly set (that is, regardless of the shift map shown in FIG. 6) (step 55). Then, the hydraulic control is performed according to the normal hydraulic pattern shown by the solid line in FIG. 7 (step 56).

FIG. 4 is a flowchart showing a main routine of a deceleration instruction according to the present embodiment. The microcomputer 1 repeatedly executes a series of procedures shown in the flowchart at predetermined intervals. First, in step 1, preview information and various sensor information υ,
θ and the like are read.

Next, a running situation ahead of the vehicle is recognized based on the preview information and the navigation information (step 2). Specifically, the three-dimensional road shape and the presence / absence of a preceding vehicle (if present, the distance to the preceding vehicle)
Etc. are recognized. An important matter to be recognized in relation to the present embodiment is detection of a curve using a road position (each node coordinate with respect to the own vehicle) in the navigation information.

In step 3 following step 2, a determination speed Vth corresponding to the shape of the curve ahead is calculated. The determination speed Vth indicates the upper limit value of the vehicle speed allowed at the current position of the vehicle in relation to the curve ahead, and the deceleration determination in step 5 (shift down or not).
Is used as a threshold value for performing Judgment speed Vth
Can be calculated basically based on the radius of curvature of the curve, the road surface μ, and the distance from the vehicle to the curve. First, the road surface μ is calculated using a method disclosed in Japanese Patent Application Laid-Open No. H8-2274. Next, the maximum value of deceleration that does not cause slip on a certain road surface μ,
That is, the allowable deceleration β is calculated. A small road surface μ means that slip is likely to occur. Therefore, the smaller the road surface μ, the smaller the allowable deceleration β. It should be noted that a specific calculation method of the allowable deceleration β is disclosed in Japanese Patent Application Laid-Open No. H11-83501, and therefore, should be referred to if necessary. Next, the allowable approach speed Vap of the curve ahead is calculated based on the node having the smallest radius of curvature in the curve ahead (the point of the curve requiring the most deceleration is referred to as “target node Ptrgt”). When the target node Ptrgt is specified, the maximum speed allowed to enter the curve (that is, “allowable approach speed Vap”) is calculated by the following equation based on the radius of curvature rtrgt of the node.

Vap = (gv × rtrgt) ^1/2

Gv in the equation is an allowable lateral acceleration.
The lateral acceleration allowed when passing through a curve decreases as the road surface μ decreases or as the radius of curvature of the curve decreases. Therefore, the allowable lateral acceleration gv is calculated using the road surface μ and the radius of curvature of the curve of the target node Ptrgt as basic parameters. It should be noted that a detailed calculation method of the allowable lateral acceleration gv is disclosed in Japanese Patent Application Laid-Open No. H11-83501. Then, a determination speed Vth indicating the upper limit vehicle speed at the current position of the own vehicle is calculated from the calculated allowable approach speed Vap. This determination speed Vth is calculated from the current position to the target node Ptrgt
To the target node Ptrgt when the vehicle speed is reduced by K% (for example, 50%) of the permissible deceleration β of the own vehicle when the vehicle speed reaches the target node Ptrgt.
The speed is such that As an example, the determination speed Vth can be obtained by the following equation.

Vth = (Vap ² ) + 2 × (K × β) L) ^1/2

In step 4 following step 3, it is determined whether or not the deceleration execution flag FDS is "1"("1" indicates that downshifting is being executed). Deceleration execution flag FD
S is initially set to "0". Therefore, the process proceeds from step 4 to step 5 when the flag FDS is "0".

In step 5, it is determined whether or not the vehicle is to be decelerated. Specifically, the determination speed Vth calculated in step 3 is compared with the current vehicle speed 算出 calculated by the vehicle speed sensor 5. Vehicle speed υ is determined speed V
If it is less than th, it is determined that it is possible to enter a curve ahead at the current vehicle speed と も without deceleration. Therefore, in this case, from the negative determination in step 5 to step 9
And the downshift instruction signal DOWN becomes "0" level. The shift-down instruction signal DOWN is normally provided except for instructing the shift control in the shift-down mode.
It is maintained at the “0” level (instructing normal mode shift control). Therefore, in this cycle, "0"
A level shift down instruction signal DOWN is output to TCU4. As a result, since the shift setting in the normal mode is continued, the hydraulic pressure is controlled according to the normal hydraulic pattern shown in FIG.

On the other hand, if the determination in step 5 is affirmative, that is, if the vehicle speed 大 き い is higher than the determination speed Vth, it is determined that the current vehicle speed υ is excessively large in order to safely enter the curve ahead. In this case, it is determined that it is a situation to decelerate, and the process proceeds to steps 6 and 11, where the downshift instruction signal DOWN is set to the “1” level, and the deceleration execution flag FDS is set to “1”. Down instruction signal DOWN attains "1" level. Therefore, the shift setting in the downshift mode is performed, and the hydraulic control is performed according to the normal hydraulic pattern.

On the other hand, the procedure for releasing the downshift instruction is as follows. When a downshift is instructed (that is, the downshift instruction signal DOWN becomes "1") according to the series of procedures described above, the deceleration execution flag FDS is set to "1" (step 6). Therefore, in the subsequent cycles, the process proceeds to step 7 according to the affirmative determination in step 4.

First, at step 7, it is determined whether or not the situation to decelerate is no longer present.
It is determined whether the vehicle has passed the curve including trgt. If a negative determination is made in this step, that is, if the vehicle has not yet passed through the node having the smallest curve curvature, the process proceeds to steps 10 and 11, where the "1" level shift-down instruction signal DOWN is output to the TCU4. Is done. Therefore, the shift speed of AT8 is kept at the target shift speed TRGT (that is, the downshift is maintained). As long as the signal does not pass through the curve, the "1" level downshift instruction signal DOW
Since N is maintained, the downshift mode is continued.

On the other hand, if the determination in step 7 is affirmative, that is, if the vehicle has passed the curve, the instruction to shift down is released. That is, the downshift instruction signal DOWN switches from the “1” level to the “0” level, and the deceleration execution flag FDS is reset to “0” (steps 8 and 11). As a result, the mode is switched from the downshift mode to the shift setting in the normal mode. At this time, if it is determined from the shift map reference result that the upshift is necessary, the affirmative determination in step 53 changes the hydraulic pattern (the pattern shown by the dotted line in FIG. 7) that is specially used when the downshift is released. Therefore, hydraulic control is executed (step 54).

The hydraulic pressure pattern at the time of shift-down release is different from the normal hydraulic pressure pattern in that the engagement side hydraulic pressure in the inertia phase is set lower than normal. Therefore, in the inertia phase, the change in the turbine speed becomes gentler than usual, and the time required to converge to the target speed is increased. In other words, the shift time in the upshift accompanying the release of the downshift is longer than that in the normal upshift. As a result, stable vehicle behavior can be maintained even if such an upshift occurs during the passage of a curve or traveling on a road with a low road surface μ. Thereby, there is an effect that the safety and reliability of the vehicle behavior control according to the monitoring outside the vehicle can be further improved.

In the above-described embodiment, an example has been described in which the maximum hydraulic pressure value on the engagement side in the inertia phase is set low at the time of upshifting accompanying the release of downshifting. However, the present invention is not limited to this, and it is obvious that the present invention can be applied to other hydraulic control in which torque shock during upshifting is reduced.

The road surface μ of the road on which the vehicle is traveling
May be calculated, and the shift time in the upshift that occurs with the release of the downshift may be varied according to the road surface μ. That is, since the slip is more likely to occur as the road surface μ is smaller, the shift time is set longer as the road surface μ is smaller, and the hydraulic control is performed in which the torque shock is less likely to occur. For example, the microcomputer 1 calculates the road surface μ. Although there are various methods for calculating the road surface μ, it can be estimated based on the yaw rate, the steering angle, the lateral acceleration, and the vehicle speed, for example, as disclosed in JP-A-8-2274. Then, the microcomputer 1 instructs the TCU 4 on the shift time T in the downshift mode according to the road surface μ. TCU4 is
The shift-up control is executed according to the designated shift time T.

In the above-described embodiment, the deceleration control in a situation where a curve is present in front of the own vehicle has been described. However, this deceleration control can be performed in combination with the alarm control (to alert the driver). preferable. For example, if the current vehicle speed に 対 し て is too high with respect to a curve ahead, an alarm is first sounded to prompt the driver to decelerate. Then, when the driver has not decelerated by the brake operation or when the deceleration is insufficient, a downshift may be instructed.

In the above-described embodiment, the deceleration control due to the curve ahead of the vehicle has been described. However, the present invention is not limited to this, and can be widely applied to various driving situations where deceleration control can be performed. For example, the present invention may be applied to deceleration control in which a downshift is performed in accordance with a distance between the vehicle and a preceding vehicle. In this case, the determination inter-vehicle distance Dth is calculated according to the following equation instead of calculating the determination speed Vth in step 3 of FIG.

Dth = (current vehicle speed ＝ [m / s] × idling time A [sec]
+ Margin B [m]) x (-(relative speed [m / s] x coefficient C + margin D) Here, the relative speed is obtained from the preview sensor information obtained from the preview sensor 2 as the distance between the preceding vehicle and the preceding vehicle. When the current inter-vehicle distance becomes smaller than the determined inter-vehicle distance Dth, it is determined that the vehicle should be decelerated, and the state is determined as described in the above-described embodiment. Slow down due to downshift.

[0031]

As described above, according to the present invention, after the vehicle is decelerated by downshifting from the running situation ahead of the vehicle,
When upshifting is performed in response to the release of the deceleration state, the shift time is intentionally set longer than usual. This allows
Even if the upshift is performed while passing a curve or traveling on a low μ road surface, stable vehicle behavior can be maintained. Therefore, the safety and reliability of the device that controls the behavior of the vehicle according to the monitoring outside the vehicle can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of a transmission system according to an embodiment.

FIG. 2 is a diagram showing a schematic structure of a main part of an automatic transmission (AT).

FIG. 3 is a table showing a relationship between a shift position and an engagement state of an engagement element.

FIG. 4 is a flowchart illustrating a main routine of a deceleration instruction according to the embodiment;

FIG. 5 is a flowchart showing a shift control procedure.

FIG. 6 shows an example of a shift map.

FIG. 7 is a schematic transition diagram of release hydraulic pressure and engagement hydraulic pressure during a shift change.

[Explanation of symbols]

1 shift control device (microcomputer), 2 preview sensor, 3 navigation unit, 4 transmission control unit (T
CU), 5 vehicle speed sensor, 6 throttle opening sensor, 7 hydraulic control circuit, 8
Automatic transmission (AT), 8a hydraulic control mechanism,
8b friction engagement mechanism, 11 front planetary,
12 rear planetary, 13 reverse clutch, 14 2 & 4 brake, 15 high clutch, 16 low clutch, 17 low & reverse brake, 18 low one-way clutch, 1
9 Crankshaft, 20 Torque converter, 21 Turbine shaft, 22 Reduction drive shaft

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G08G 1/16 G08G 1/16 D // B60R 21/00 628 B60R 21/00 628C 628F F16H 59:66 F16H 59:66 F-term (reference) 3D044 AA24 AA42 AA45 AB01 AC03 AC26 AC28 AC56 AC59 AD16 AD17 AE03 AE07 3J052 AA01 CA01 CA05 GD04 GD07 HA01 KA01 LA01 5H180 AA01 BB13 CC03 CC04 CC14 FF05 FF27 LL01 LL04 LL01 LL04 LL04

Claims (5)

[Claims] 1. A shift control device for recognizing a running condition ahead of a vehicle based on preview information and performing a shift change of an automatic transmission when deceleration is required. Instruction means for instructing a downshift when it is determined that the traveling condition of the vehicle has become a condition to be decelerated, and instructing release of the downshift when it is determined that the situation to be decelerated is no longer present; Control means for performing engagement control of the engagement element, wherein the control means performs a shift-up by the instruction means to release a downshift so that a torque shock is smaller than that in a normal shift-up. A shift control device for an automatic transmission, wherein the shift control device performs an appropriate engagement control. 2. The system according to claim 1, wherein said instruction means instructs a downshift when it is determined that the current vehicle speed is excessive with respect to a radius of curvature of a curve existing in front of the vehicle. 3. A shift control device for an automatic transmission according to claim 1. 3. The system according to claim 2, wherein said instruction means instructs a downshift when it is determined that the vehicle should be decelerated based on a positional relationship between the own vehicle and a preceding vehicle existing in front of the own vehicle. 2. The shift control device for an automatic transmission according to claim 1. 4. The shift control device according to claim 1, wherein the control means performs an engagement control such that the shift time is longer than a normal shift-up time when performing a shift-up in response to a shift-down release instruction from the instruction means. The shift control device for an automatic transmission according to claim 1. 5. The instructing means calculates a road surface μ of a road on which the own vehicle is traveling, and the control means, when performing upshifting in response to an instruction to cancel downshifting from the instructing device, executes the road surface μ. 2. The shift control device for an automatic transmission according to claim 1, wherein the engagement control is performed such that the shift time becomes longer as is smaller.