JP2001088579A - Shift control device for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the safety and reliability of a device for controlling the behavior of a vehicle according to monitoring outside of the vehicle. SOLUTION: This shift control device for an automatic transmission has a microcomputer 1 instructing a down-shift in the case of judging that the condition of travel in front of one's own vehicle is a condition to reduce speed on the basis of preview information obtained from a preview sensor 2 and a navigation unit 3, and a TCU 4 performing the engaging control of an engaging element in the AT 8. The TCU 4 performs such engaging control that a shift shock is larger than the normal shift change in the case of the down-shift being instructed from the microcomputer 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 vehicle, and more particularly to a shift-down engagement performed in a situation where deceleration is required. Regarding control.

[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. In this way, by decelerating in advance just before entering a curve, it is possible to realize a good curve traveling property without giving a driver an uncomfortable feeling.

[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 Therefore, unless the driver is alerted by an alarm or the like, the driver may not notice that the downshift has been performed.

Accordingly, an object of the present invention is to urge a driver to be vigilant by intentionally causing a shift shock when performing such a downshift.

[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. A shift control device for performing shift down when it is determined, based on the preview information, that the traveling situation ahead of the vehicle has become a situation where deceleration is required, and an engagement element in the automatic transmission. Control means for performing engagement control. Here, when the downshift is instructed from the instructing means, the control means performs engagement control such that the shift shock becomes larger than in a normal shift change.

[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.

Further, it is preferable that when the downshift is instructed from the instructing means, the control means performs the engagement control by shifting the hydraulic pressure rising timing on the engagement side or the release side in a normal shift change.

The instruction means may calculate a road surface μ of a road on which the vehicle is traveling. in this case,
It is preferable that when the downshift is instructed from the instructing means, the control means performs engagement control such that the smaller the road surface μ, the smaller the shift shock.

[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. Based on various input information including the above, the microcomputer 1 travels including a situation ahead of the vehicle, a traveling state of the vehicle, and a road surface condition (a road surface friction coefficient μ (hereinafter, referred to as “road surface μ”)). Recognize the situation, and
The microcomputer 1 outputs instruction signals DOWN and TRGT to the TCU 4 to perform deceleration according to the recognition result.

[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 is a diagram showing a schematic structure of an automatic transmission 8 (hereinafter, referred to as "AT") as an example.
The driving force from the crankshaft 19 of the engine is transmitted to the turbine shaft 21 via the torque converter 20. Turbine shaft 21 as input shaft of transmission
Are connected to the sun gear of the rear planetary 22.
On the other hand, a reduction drive shaft 22 that is an output shaft of the transmission 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 is
As shown, three multi-plate clutches (reverse clutch 13, high clutch 15, low clutch 16), two multi-plate brakes (2 & 4 brake 14, low & reverse brake 17) and low one-way clutch 18 are connected. . These engagement elements (clutch, brake)
Are selectively engaged or released in accordance with the gear position. 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. Then, the TCU 4 outputs an engagement control signal in the normal mode to the hydraulic control circuit 7, and the engagement control in the normal mode is executed (step 53).
FIG. 7 is a schematic transition diagram of the release hydraulic pressure and the engagement hydraulic pressure at the time of a shift change. In the normal mode, an engagement control signal is output such that the release-side / engagement-side hydraulic pressure changes as indicated by the solid line in FIG.

When the instruction signal DOWN from the microcomputer 1 is "1", that is, when the downshift is instructed, the TCU 4 proceeds from step 51 to step 54 to perform the shift setting in the downshift mode. In this case, the shift setting / engagement control in the normal mode is temporarily interrupted, and the shift stage GR is forcibly set to the target shift stage TRGT instructed by the microcomputer 1 (that is, regardless of the shift map shown in FIG. 6). )
It is set (step 54). Then, an engagement control signal in the downshift mode is output to the hydraulic control circuit 7, and the engagement control in the downshift mode is executed (step 55). In shift down mode,
As shown by the dotted line in FIG. 7, the start-up is performed earlier than the engagement-side hydraulic pressure start-up timing in the normal mode (dotted line a). Alternatively, it may be started later than the engagement side hydraulic pressure start timing in the normal mode (dotted line b).

FIG. 4 is a flowchart showing a main routine of a deceleration instruction according to this 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, the running condition ahead of the vehicle is recognized based on the preview information and the navigation information (step 2). Specifically, a three-dimensional road shape, the presence or absence of a preceding vehicle, and the presence of a preceding vehicle, the inter-vehicle distance to the preceding vehicle, and the like 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.

For example, the road surface μ of the road is calculated by using the method disclosed in Japanese Patent Application Laid-Open No. 8-2274.
Next, the maximum value of the deceleration that does not cause a 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 is calculated based on a node having the smallest radius of curvature of 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 radius of curvature r of that node is
Based on trgt, the maximum speed allowed to enter the curve (ie, “allowable entry speed Vap”) is calculated by the following equation.

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". The shift-down instruction signal DOWN is normally “0” except when instructing shift control in the shift-down mode.
(Instruction of normal mode shift control). Therefore, step 11 in this cycle
Since the downshift instruction signal DOWN at the “0” level is output to the TCU 4, the TCU 4 performs the shift control in the normal mode.

On the other hand, if an affirmative determination is made in step 5, that is, if the vehicle speed 大 き い is greater than the determination speed Vth, it is determined that the current vehicle speed υ is excessively large in order to safely enter a forward curve. In this case, it is determined that the vehicle is to be decelerated, 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”. When the downshift instruction signal DOWN becomes “1” level, the TCU 4 performs the shift control in the downshift mode (steps 54 and 55).

On the other hand, the procedure for canceling the downshift instruction is as follows. Shift down is instructed according to the series of procedures described above (that is, shift down instructing signal DOWN).
Is set to "1"), 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, in 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 the curve, the process proceeds to steps 10 and 11,
The "1" level shift down instruction signal DOWN is
4 is output. Therefore, TCU4 is AT8
Is maintained at the target shift speed TRGT. As long as the vehicle does not pass through the curve, the "1" level shift down instruction signal D
Since OWN 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). This switches from shift down control to shift control in normal mode,
Normal shift control is restarted (steps 52 and 53).

As can be understood from the above description, when the vehicle is not sufficiently decelerated with respect to the curve ahead, the downshift instruction signal DOWN becomes "1" level (step 6). (Shift down) is executed. The shift change in the downshift mode is performed at a timing earlier than the engagement side hydraulic pressure rising timing in the normal mode (or a later timing as shown by the dotted line b in FIG. 7), as indicated by a dotted line a in FIG. Increase the hydraulic pressure on the fastening side. By advancing the start-up timing on the fastening side, the fastening on the fastening side proceeds before the release on the release side proceeds appropriately, and a temporary interlock state occurs. As a result, the shift shock becomes larger than at the time of a shift change in the normal mode. Further, by delaying the start-up timing of the fastening side, the progress of the fastening on the fastening side is delayed with respect to the progress of the release on the release side, and a state occurs in which the fastening is suddenly performed at a certain point. As a result, the shift shock becomes larger than at the time of a shift change in the normal mode.

As described above, even if the driver is not warned using an alarm or the like, the driver can be instructed that the current driving state before the curve should be alert by generating a shift shock that can be felt. Can be recognized. Therefore, 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 embodiment, an example has been described in which the hydraulic pressure start timing on the engagement side is shifted in the downshift mode. However, the present invention is not limited to this, and it goes without saying that the present invention can be applied to other hydraulic control in which the shift shock becomes large. For example, the hydraulic pressure falling timing on the release side may be shifted. Further, the shift time may be set shorter in the downshift mode than in the normal mode.

The microcomputer 1 calculates the road surface μ of the road on which the vehicle is traveling, and calculates the road surface μ.
, The magnitude of the shift shock in the downshift mode may be adjusted. That is, since the slip is more likely to occur as the road surface μ is smaller, it is necessary to perform engagement control such that the shift shock is smaller as the road surface μ is smaller. Various methods for calculating the road surface μ have been proposed. For example, as disclosed in Japanese Patent Application Laid-Open No. H8-2274, estimation can be performed based on yaw rate, steering angle, lateral acceleration, and vehicle speed. it can. Then, the microcomputer 1 instructs the TCU 4 on the shift time T in the downshift mode according to the road surface μ. TCU
4 determines the offset amount of the hydraulic pressure rise / fall timing on the engagement side / release side according to the instructed shift time T, and executes the downshift control in accordance with the offset amount.

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, a shift shock may be generated when the driver has not decelerated by the brake operation or when the deceleration is insufficient.

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 according to a positional relationship with a preceding vehicle. In this case, instead of calculating the determination speed Vth, the determination inter-vehicle distance Dth
Is calculated according to the following equation.

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 determined by the preview sensor 2
Can be calculated based on the change per unit time of the inter-vehicle distance from the preceding vehicle from the preview sensor information obtained from the above. When the current inter-vehicle distance becomes smaller than the determination inter-vehicle distance Dth, it is determined that the vehicle should be decelerated, and deceleration is performed by downshifting as described in the above-described embodiment.

[0034]

As described above, according to the present invention, when deceleration is necessary due to the running condition ahead of the vehicle, the driver is alerted by intentionally downshifting to cause a shift shock. Can be. 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.

[Description of Signs] 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) F16H 59:66 F16H 59:66 63:12 63:12 F term (Reference) 3D041 AA66 AA71 AA80 AB01 AC01 AC15 AC18 AD04 AD31 AD47 AD51 AE31 AE39 AE40 3G093 AA05 BA04 BA15 BA23 CB08 DA06 DB05 DB11 DB18 DB21 EB03 EC01 FA10 3J052 AA07 BB17 CA01 FB31 GD00 HA02 KA01 LA01 5H180 AA01 BB13 CC04 CC12 FF05 LL01 LL01 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. When it is determined that the traveling state of the vehicle has become a state to be decelerated, there is provided an instruction unit for instructing a downshift, and a control unit for performing engagement control of an engagement element in the automatic transmission. A shift control device for an automatic transmission, wherein when a downshift is instructed from the instructing means, engagement control is performed such that a shift shock is greater than in a normal shift change. 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 control means performs engagement control by shifting the hydraulic pressure start timing on the engagement side or the release side in a normal shift change when a downshift is instructed from the instructing 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. When the downshift is instructed by the instructing means, the control means shifts as the road surface μ becomes smaller. The shift control device for an automatic transmission according to claim 1, wherein engagement control is performed such that shock is reduced.