Speed change control device for automatic transmission and control method thereof

Abstract

A speed change control device for an automatic transmission according to this invention determines whether or not a request to downshift a gear position of the transmission exists during traveling in a manual speed change mode (S1, S2), and calculates an input shaft rotation speed of the transmission following a downshift based on the downshift request (S4). When it is determined that the calculated rotation speed is higher than a rotation speed limit value (S5), the speed change control device performs a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the calculated rotation speed (S6, S8).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a speed change control device for an automatic transmission according to a first embodiment.

FIG. 2 is a flowchart showing control of the speed change control device for an automatic transmission according to the first embodiment.

FIG. 3 is a map showing the relationship between a vehicle speed, a primary rotation speed, and a speed ratio.

FIG. 4 is a map showing the relationship between a vehicle speed, a primary rotation speed, and a speed ratio.

FIG. 5 is a flowchart showing control of the speed change control device for an automatic transmission according to a second embodiment.

Claims

1. A speed change control device for an automatic transmission, including a manual speed change mode in which switching between a plurality of gear positions can be performed in accordance with a driver operation, the device comprising: a controller whichupshifts a gear position when a rotation speed of an input shaft of the transmission exceeds a predetermined high rotation speed;determines whether or not a request to downshift the gear position of the transmission exists during traveling in the manual speed change mode;calculates the input shaft rotation speed of the transmission following a downshift based on the downshift request;determines whether or not the calculated rotation speed is higher than a rotation speed limit value set on a lower rotation side than the predetermined high rotation speed; andperforms a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the calculated rotation speed when it is determined that the calculated rotation speed is higher than the rotation speed limit value.

2. The speed change control device as defined in claim 1, wherein the controller performs a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the rotation speed limit value when it is determined that the calculated rotation speed is higher than the rotation speed limit value.

3. The speed change control device as defined in claim 1, wherein the rotation speed limit value is set such that a time required for the input shaft rotation speed of the transmission to exceed the predetermined high rotation speed after exceeding the rotation speed limit value following a downshift based on the downshift request is equal to or greater than a first predetermined time.

4. The speed change control device as defined in claim 1, wherein the controller determines at least one of whether or not a request to perform a kick down exists during traveling in the manual speed change mode and whether or not a request to perform a downshift in accordance with a driver operation exists during traveling in the manual speed change mode.

5. The speed change control device for as defined in claim 1, wherein the controller which determines whether or not a request to perform a kick down exists during traveling in the manual speed change mode and whether or not a request to perform a downshift in accordance with a driver operation exists during traveling in the manual speed change mode, anddetermines whether or not the calculated rotation speed is higher than a first rotation speed limit value when a kick down is performed during traveling in the manual speed change mode and whether or not the calculated rotation speed is higher than a second rotation speed limit value when a downshift is performed on the basis of a downshift request in accordance with a driver operation during traveling in the manual speed change mode, the second rotation speed limit value being higher than the first rotation speed limit value.

6. The speed change control device as defined in claim 1, wherein, when it is determined that a request to downshift the gear position of the transmission exists during traveling in the manual speed change mode and the input shaft rotation speed of the transmission is higher than the rotation speed limit value, the controller prohibits downshifting regardless of whether or not the calculated rotation speed is higher than the rotation speed limit value.

7. The speed change control device as defined in claim 4, wherein, when it is determined that a request to perform a downshift in accordance with a driver operation exists and an elapsed time following a previous driver operation is shorter than a second predetermined time, the controller performs a downshift based on the downshift request regardless of whether or not the calculated rotation speed is higher than the rotation speed limit value.

8. The speed change control device as defined in claim 5, wherein, when it is determined that a request to perform a downshift in accordance with a driver operation exists and an elapsed time following a previous driver operation is shorter than a second predetermined time, the controller performs a downshift based on the downshift request regardless of whether or not the calculated rotation speed is higher than the rotation speed limit value.

9. The speed change control device as defined in claim 1, wherein the rotation speed limit value is set such that an acceleration produced by a driving force step occurring when a downshift is performed on the basis of the downshift request is smaller than a predetermined acceleration upper limit value.

10. A speed change control method for an automatic transmission, including a manual speed change mode in which switching between a plurality of gear positions can be performed in accordance with a driver operation, the method comprising: upshifting a gear position when a rotation speed of an input shaft of the transmission exceeds a predetermined high rotation speed;determining whether or not a request to downshift the gear position of the transmission exists during traveling in the manual speed change mode;calculating the input shaft rotation speed of the transmission following a downshift based on the downshift request;determining whether or not the calculated rotation speed is higher than a rotation speed limit value set on a lower rotation side than the predetermined high rotation speed; andperforming a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the calculated rotation speed when it is determined that the calculated rotation speed is higher than the rotation speed limit value.

11. The speed change control method as defined in claim 10, wherein the performing a downshift performs a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the rotation speed limit value when it is determined that the calculated rotation speed is higher than the rotation speed limit value.

12. The speed change control method as defined in claim 10, wherein the rotation speed limit value is set such that a time required for the input shaft rotation speed of the transmission to exceed the predetermined high rotation speed after exceeding the rotation speed limit value following a downshift based on the downshift request is equal to or greater than a first predetermined time.

13. The speed change control method as defined in claim 10, wherein the determining whether or not the request to downshift the gear position of the transmission exists determines at least one of whether or not a request to perform a kick down exists during traveling in the manual speed change mode and whether or not a request to perform a downshift in accordance with a driver operation exists during traveling in the manual speed change mode.

14. The speed change control method as defined in claim 10, wherein the determining whether or not the request to downshift the gear position of the transmission exists determines whether or not a request to perform a kick down exists during traveling in the manual speed change mode and whether or not a request to perform a downshift in accordance with a driver operation exists during traveling in the manual speed change mode, andthe determining whether or not the calculated rotation speed is higher than the rotation speed limit value determines whether or not the calculated rotation speed is higher than a first rotation speed limit value when a kick down is performed during traveling in the manual speed change mode, and determines whether or not the calculated rotation speed is higher than a second rotation speed limit value when a downshift is performed on the basis of a downshift request in accordance with a driver operation during traveling in the manual speed change mode, the second rotation speed limit value being higher than the first rotation speed limit value.

15. The speed change control method as defined in claim 10, wherein, when it is determined that a request to downshift the gear position of the transmission exists during traveling in the manual speed change mode and the input shaft rotation speed of the transmission is higher than the rotation speed limit value, the performing a downshift prohibits downshifting regardless of the determination result of the determining whether or not the calculated rotation speed is higher than the rotation speed limit value.

16. The speed change control method as defined in claim 13, wherein, when it is determined that a request to perform a downshift in accordance with a driver operation exists and an elapsed time following a previous driver operation is shorter than a second predetermined time, the performing a downshift performs a downshift based on the downshift request regardless of the determination result of the determining whether or not the calculated rotation speed is higher than the rotation speed limit value.

17. The speed change control method as defined in claim 14, wherein, when it is determined that a request to perform a downshift in accordance with a driver operation exists and an elapsed time following a previous driver operation is shorter than a second predetermined time, the performing a downshift performs a downshift based on the downshift request regardless of the determination result of the determining whether or not the calculated rotation speed is higher than the rotation speed limit value.

18. The speed change control method as defined in claim 10, wherein the rotation speed limit value is set such that an acceleration produced by a driving force step occurring when a downshift is performed on the basis of the downshift request is smaller than a predetermined acceleration upper limit value.

19. A speed change control device for an automatic transmission, including a manual speed change mode in which switching between a plurality of gear positions can be performed in accordance with a driver operation, the device comprising: auto upshift means for upshifting a gear position when a rotation speed of an input shaft of the transmission exceeds a predetermined high rotation speed;downshift request determining means for determining whether or not a request to downshift the gear position of the transmission exists during traveling in the manual speed change mode;rotation speed determining means for calculating the input shaft rotation speed of the transmission following a downshift based on the downshift request, and determining whether or not the calculated rotation speed is higher than a rotation speed limit value set on a lower rotation side than the predetermined high rotation speed; anddownshift control means for performing a downshift to a gear position at which the input shaft rotation speed of the transmission is lower than the calculated rotation speed when it is determined that the calculated rotation speed is higher than the rotation speed limit value.