Range selection apparatus for an automatic transmission

Abstract: A range switchover apparatus (1) is disclosed, including a range switchover valve operating device (3) capable of switching over a switchover valve (2), which switches over a shift range, among respective shift positions, a drive motor (12) for driving the range switchover valve operating device, a measuring device (28,32) for measuring a time, during which the drive motor causes the range switchover valve operating device to switch over between predetermined shift positions, a rotation control device (35) for controlling the rotational speed of the drive motor, a correcting device (34) for correcting the rotational speed by the rotation control device so that when a time measured by the measuring device differs from a target time in a predetermined range, the measured time becomes the target time, and a storage device (33) for storing the rotational speed corrected by the correcting device. The range switchover apparatus prevents a change in rotational speed due to secular change from being generated in a motor for driving a switchover valve in an automatic transmission.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to a range switchover apparatus for use in switchover of a running range of an automatic transmission, according to the preamble of claim 1 and as known from EP-A-0 444 676. 2. Description of the Related Art: Conventionally, a range switchover apparatus for switchover of a running range of an automatic transmission comprises a manual valve in the automatic transmission, and a shift lever connected to the manual valve by a shift cable and provided in a vehicle interior. This range switchover apparatus is constructed such that a driver operates the shift lever to thereby switch over the manual valve via the shift cable. However, it has been demanded to increase freedom for a place where a shift lever is installed, at the request of a recent increase in freedom for a vehicle interior design in automobiles and of an increase in types of a car derived from the same platform. A range switch over apparatus, which meets with such demand, is disclosed in Japanese Patent Laid-Open No. 190180/1995 and so on. With such range switchover apparatus, a motor is used to actuate a manual valve to perform switchover of running ranges. However, conventional range switchover apparatuses have never taken any measure to meet secular change due to a long term use of the motor. Therefore, there is the possibility that a change in rotational speed of the motor extends or shortens a time required for switchover of ranges to give an uncomfortable feeling to a driver. SUMMARY OF THE INVENTION The invention has its object to provide a range switchover apparatus capable of surely performing a switchover of a switchover means while preventing secular change from causing a change in rotational speed of a motor for driving a switchover means of an automatic transmission. The above-mentioned problem is solved by a range switchover apparatus for automatic transmission for automatic transmissions, comprising a range switchover means operating unit capable of switching over a switchover means, which switches over a shift range, among respective shift positions, a drive motor for driving the range switchover means operating unit, a measuring unit for measuring a time, during which the drive motor causes the range switchover means operating unit to switch over between predetermined shift positions, a rotation control unit for controlling the rotational speed of the drive motor, a correcting unit for correcting the rotational speed by the rotation control unit so that when a time measured by the measuring unit differs from a target time in a predetermined range, the measured time becomes the target time, and a storage unit for storing the rotational speed corrected by the correcting unit. The invention has a feature in the range switchover apparatus for automatic transmissions, such that the target time is one set in accordance with an environmental condition, the rotation control unit controls the rotational speed of the drive motor on the basis of a duty ratio of the drive motor, and the correcting unit compares the measured time and the target time with each other to correct the duty ratio so as to make the same large when the measured time exceeds the target time and to correct the duty ratio so as to make the same small when the measured time is shorter than the target time. BRIEF DESCRIPTION OF DRAWINGS The invention will be described in conjunction with the following drawings in which like features are designated with like reference characters, and wherein: Fig. 1 is a block diagram showing a range switchover apparatus according to the invention; Fig. 2 is a diagrammatic view showing an entire range switchover apparatus according to an embodiment of the invention; Fig. 3 is an enlarged view showing a detent lever; Fig. 4(a) and Fig. 4(b) are operation flowchart of the range switchover apparatus; Fig. 5 is a table indicating a duty ratio of a motor on the basis of a battery voltage and a temperature of a working oil in an automatic transmission; Fig. 6 is a table indicating a target time of switchover between a neutral range and a drive range in a battery voltage and a temperature of the working oil in the automatic transmission, respectively; Fig. 7 is a view illustrating the operation of a detent mechanism in the range switchover apparatus; and Fig. 8 is a view illustrating inlets conformed to a rotating direction of the detent lever. DESCRIPTION OF THE PREFERRED EMBODIMENTS When the drive motor (12) is started, the range switchover means operating unit (7) is actuated toward predetermined shift positions (P, R, N, D, L) to switch over the switchover means (2, 5). The measuring unit (28, 32) measures a time, during which the range switchover means operating unit (7) switches over between predetermined shift positions (P, R, N, D, L). The drive motor (12) is controlled in rotational speed by the rotation control unit (35) to rotate. Initially, the rotation control unit (35) rotates and controls the drive motor (12) on the basis of rotational speeds stored in the storage unit (33). When the drive motor (12) changes in rotational speed due to secular change of the drive motor (12), the range switchover means operating unit (7) also changes in operational speed and a time required for changeover between the predetermined shift positions (P, R, N, D, L). When a time measured by the measuring unit (28, 32) differs from a target time in a predetermined range, the correcting unit (34) corrects the rotational speed so that the time measured by the measuring unit (28, 32) approaches the target time. The storage unit (33) stores a new rotational speed, and in range switchover next time, the rotation control unit (35) controls rotation of the drive motor (12) at the new rotational speed stored. However, in the case where a time measured by the measuring unit (28, 32) does not make a target time in a predetermined range even when the rotation control unit (35) rotates the drive motor (12) at the new rotational speed, the correcting unit (34) corrects the rotational speed again, such rotational speed is stored in the storage unit (33) and the rotation control unit (35) rotates the drive motor (12) at such rotational speed. The range switchover apparatus (1) repeats such procedure to constantly perform control so that the range switchover time becomes a target time in a predetermined range. In addition, the target time is a time set in view of circumstances such as a battery voltage of the drive motor (12), temperature of the working oil of the automatic transmission and so on. Also, the rotational speed of the drive motor (12) is corrected by changing, for example, a duty ratio. Therefore, the storage unit (33) stores the duty ratio. More specifically, the correcting unit (34) compares a measured time and a target time with each other to correct the duty ratio to make the same large when the measured time exceeds the target time and to make the same small when the measured time is shorter than the target time, and the corrected duty ratio is stored in the storage unit (33). In addition, signs in parenthesis are marked for convenience and easy correspondence with the drawings, and are not intended for limitation of the constitution of the invention. A range switchover apparatus according to embodiments of the invention will be explained with reference to the drawings. (Explanation of Constitution) Fig. 2 is a diagrammatic view of a range switchover apparatus 1 of an automatic transmission. The range switchover apparatus 1 is adapted to actuate a manual valve 2, which serves as a switchover valve constituting a part of an automatic transmission such as multistage type automatic transmissions and continuously variable transmissions (CVT). Themanualvalve 2 is contained in a valve body 3, which constitutes a part of an outward appearance of an automatic transmission. The manual valve 2 is provided within the valve body 3 to be movable in directions indicated by an arrow A and an arrow B, corresponding to an axial direction of a spool 2a of the valve. The automatic transmission can be sequentially switched over to P, R, N, D and L ranges from a side of the arrow B to a side of the arrow A in the figure by moving the manual valve 2 in a direction of the arrow A and in a direction of the arrow B. An engagement groove 2c composed of two circular disks 2b, 2b is formed on a tip end of the manual valve 2 on the side of the arrow A. A detent lever (range switchover valve operating unit) 5 engages with the engagement groove 2c via a pin 5a provided on an arm portion 5B of the detent lever 5. The detent lever 5 has a sheet-shaped body 5c as shown in Fig. 3. Five range engagement grooves 5d, 5e, 5f, 5g and 5h are formed at predetermined spacings on an upper portion of the body 5c as viewed in the figure. The respective range engagement grooves 5d, 5e, 5f, 5g and 5h are arranged in this order from a right side in the figure to correspond to the ranges "P", "R", "N", "D" and "L" of the automatic transmission. Also, the arm portion 5b provided with the above-mentioned pin 5a projects rightward of the body 5c as viewed in the figure. A parking rod engaging hole 5i for driving of a parking mechanism in the P range (not shown) is formed on and extended through a leftward portion of the body 5c as viewed in the figure. Also, a rectangular-shaped engagement hole 5j, through which a range control shaft 7 described later is inserted, is formed on and extended through a substantially central portion of the body. Provided on an upper portion of the five range engagement grooves 5d, 5e, 5f, 5g and 5h of the body 5c is a detent spring 9 composed of a sheet spring and fixed at one end thereof to the valve body 3 or a casing of the automatic transmission or the like. A roller 9a rotatably supported on a tip end of the detent spring 9 is biased downward in Fig. 1 by the elasticity of the detent spring 9 to fit into and engage with one of five range engagement grooves 5d, 5e, 5f, 5g and 5h. Also, the rod-shaped range control shaft 7 engages with the engagement hole 5j of the body 5c to be made integral with the detent lever 5. The detent lever 5, the detent spring 9 and so on constitute a detent mechanism 8. The range control shaft 7 is formed at its left tip end with an engaging portion 7a having a rectangular-shaped cross section. A valve drive device 10 is connected to the engaging portion 7a. The valve drive device 10 is mounted on a cover of the automatic transmission or the like. The valve drive device 10 has a box-shaped casing 11. The casing 11 mounts thereon a DC drive motor 12. The drive motor 12 is provided with a clutch 19. A worm 12b is mounted on an output shaft of the drive motor 12. The worm 12b meshes with a worm wheel (not shown), which is rotatably supported on the casing 11. A gear 15 is provided on the worm wheel to rotate together with the worm wheel (not shown). A large gear 16a of a two-stage gear 16 rotatably supported on the casing 11 can mesh with the gear 15. The two-stage gear 16 comprises a small gear 16b having a half of a pitch circle radius of the large gear 16a and the large gear 16a formed therewith to be coaxial and integral therewith. The small gear 16b meshes with an output gear (not shown), which has a pitch circle radius four times that of the small gear 16b. The output gear is rotatably supported on the casing 11. Further, the output gear is formed centrally thereof with a rectangular-shaped engagement hole 17a. The above-mentioned engaging portion 7a of the range control shaft 7 fits into and engages with the engagement hole 17a. Connected to the drive motor 12 and the clutch 19 is a range control unit 20 for controlling the entire range switchover apparatus 1. The range control unit 20 is contained in the casing 11 to be connected to a shift lever position detecting unit 21. The shift lever position detecting unit 21 is adapted to detect a position of a shift lever 22. Connected to the range control unit 20 is a voltage meter 24 for measuring a voltage of a battery 23 connected to the motor 12. Further, connected to the range control unit 20 is an automatic transmission control unit 26 for controlling an automatic transmission 25. Connected to the automatic transmission control unit 26 is an oil temperature sensor 27, which is provided in the automatic transmission 25 to measure a temperature of a working oil in the automatic transmission 25. Also, connected to the range control unit 20 is a position sensor 28, which is provided on a stationary member (not shown) to detect positions of the range engagement grooves 5d, 5e, 5f, 5g and 5h of detent lever 5. The position sensor 28 detects a body 36 being detected, provided on inlets, described later, of the respective range engagement grooves 5d, 5e, 5f, 5g and 5h to detect the range engagement grooves 5d, 5e, 5f, 5g and 5h. The range control unit 20 comprises, as shown in Fig. 2, a RAM 1 (29) for storing a battery voltage measured by the voltage meter 24, a RAM 2 (30) for storing an oil temperature in the automatic transmission 25, measured by the oil temperature sensor 27, a counter 32 for counting a time required for switching over the range engagement grooves making use of the position sensor 28 detecting the range engagement grooves 5d, 5e, 5f, 5g and 5h, a RAM 3 (33) for storing a table of duty ratio (referred below to as "MAP1") conformed to the circumstance shown in Fig. 5, a table of target time (referred below to as "MAP2") conformed to the circumstance required for switchover between a neutral position (N) and a drive position (D), and a selected duty ratio of the motor 12, a correcting unit 34 for selecting a duty ratio over again so that a measurement time approaches a target time when a measurement time by the counter 32 differs from a target time in a predetermined range, a rotation control unit 35 for controlling the rotational speed of the motor 12 on the basis of a duty ratio in Fig. 6 and controlling actuation of the clutch 19, and so on. The counter 32, correcting unit 34 and rotation control unit 35 are provided in a CPU 31. (Explanation of Operation) An explanation will be given on the basis of a flowchart shown in Fig. 4. At the start of or during the running of a vehicle, when the shift lever 22 is switched over, the shift lever position detecting unit 21 detects a switchover position of the shift lever 22 to informthe rotation control unit 35 of the same (section S1). At this time, information about battery voltage measured by the voltagemeter 24 is stored in the RAM1 (29), and information about temperature of the working oil in the automatic transmission 25, measured by the oil temperature sensor 27 is stored in the RAM2 (30). The rotation control unit 35 causes the RAM2 (30) to select a duty ratio from the MAP1 on the basis of the information about battery voltage and the information about oil temperature and store the selected duty ratio (section S2). In addition, the duty ratio is a ratio of a movable time to a total time in a given time. The rotation control unit 35 starts the motor 12 so as to turn the detent lever 5 to a position where the range engagement grooves 5d, 5e, 5f, 5g and 5h corresponding to a range conformed to a switchover position of the shift lever can engage with the roller 9a (section S3). The motor 12 rotates forward or rearward at a rotational speed conformed to the duty ratio. Then the range control shaft 7 rotates a predetermined angle in a direction of an arrow C or an arrow D in Fig. 1 through the worm 12b, worm wheel (not shown), gear 15, two-stage gear 16, and output gear (not shown). The detent lever 5, pin 5a, and the arm portion 5b also rotate in the direction of the arrow C or the arrow D. When the pin 5a has rotated a predetermined angle, the spool 2a of the manual valve 2 engaging with the pin 5a via the engagement groove 2c is moved in a direction of the arrow A or the arrow B. The range of the manual valve 2 is sequentially switched over to the P, R, N, D and L ranges from the side of the arrow B. In the course of such switchover, the position sensor 28 sequentially detects the range engagement grooves 5d, 5e, 5f, 5g and 5h, which engage with the roller 9a (section S4). Simultaneously, the counter 32 counts a time required for adjacent range engagement grooves to be switched over (section S5 to section S7). The counter 32 is called in the range control unit 20 at a constant interval, so that the number of counting is replaced by time. In the embodiment, for example, in the case of switchover between the neutral position (N) and the drive position (D), the rotation control unit 35 causes the RAM3 (33) to read a target time of range switchover from the MAP2 on the basis of the information about battery voltage, measured by the voltage meter 24 and the information about oil temperature, measured by the oil temperature sensor 27. Further, the rotation control unit 35 judges whether a time (measurement time) required for switchover from the neutral position (N) to the drive position (D) is in the range of target time or not (section S8). When such time is in the range of target time, a duty ratio of the drive motor 12 remains as it is, and is not altered. When the measurement time is short of the range of target time (section S9), however, the detent lever 5 will rotate at a greater rotational speed than a normal rotational speed, which necessitates reduction in the rotational speed of the motor 12 at the time of next switchover. Hereupon, the correcting unit 34 corrects a duty ratio stored in the RAM 3 (33) to a lower value by 5 % (section S10), and corrects all the values of the MAP1 to lower values by 5 % (section S13). At the next time, the rotation control unit 35 controls the rotation of the drive motor 12 on the basis of the duty ratio, which is decreased 5 %. Conversely, when the measurement time is longer than the range of target time (section S11), the detent lever 5 will rotate at a smaller rotational speed than the normal rotational speed, which necessitates an increase in the rotational speed of the motor 12 at the time of next switchover. Hereupon, the correcting unit 34 corrects a duty ratio stored in the RAM 3 (33) to a higher value. When the duty ratio is 100 or more, it cannot be increased. Therefore, only when a duty ratio stored in the RAM 3 (33) is less than 100, the correcting unit 34 corrects the duty ratio higher by 5 % to make all the values of the MAP1 higher by 5 % (section S12, section S13). From the next time on, the rotation control unit 35 controls the rotation of the drive motor 12 on the basis of the duty ratio, which is increased 5 %. On the other hand, when a duty ratio stored in the RAM 3 (33) is 100 or more, and a difference between a maximum target time in the range of target time and a measurement time amounts to at most 20 % of the target time, the duty ratio is not increased but remains as it is (section S14). In the case of over 20 %, the drive motor 12 is put in abnormal state, and the range control unit 20 transmits an abnormality signal (section S15). In this manner, the range switchover apparatus according to the embodiment stores that duty ratio, by which a switchover time comes within a target time when a range switchover time differs from the target time because of secular change. In addition, the range switchover apparatus according to the embodiment corrects a duty ratio again when the latter does not come within the range of target time even at the time of next switchover, and repeats such operations. Also, the drive motor 12 tends to become higher in rotational speed at some period and then lower when its rotational speed changes due to secular change. In the case where the detent lever 5 rotates in the direction of arrow D in Fig. 7 in the above-mentioned operation, for example, when an inlet 5g' (see Fig. 7) of the range engagement groove 5g corresponding to a drive range position is facing the roller 9a, the position sensor 28 detects a body 36 being detected, provided on the inlet 5g' to detect the inlet 5g'. The rotation control unit 35 releases the clutch 19 to prevent torque of the drive motor 12 from being transmitted to the detent lever 5, thereby stopping rotation of the detent lever 5. In Fig. 7, when having passed a position where a drawing force generates for the roller 9a, the detent lever 5 makes the detent engagement grooves receive the roller 9a. When the inlet 5g' of the range engagement groove 5g faces the roller 9a, the reason why the clutch 19 is released to prevent torque of the drive motor 12 from being transmitted to the detent lever 5 is that after the clutch 19 is released, the detent lever 5 may rotate due to inertia of respective parts and stop its rotation before the roller 9a falls down into a valley of the range engagement groove or after the roller passes a valley 5g" of the range engagement groove 5g. In such case, range switchover of the manual valve 2 may become incorrect and so switchover operation of the automatic transmission 25 may not be effected smoothly. With the range switchover apparatus 1 according to the embodiment, the position sensor 28 detects the inlet 5g' of the range engagement groove 5g coming to the roller 9a, as shown in Fig. 7, before the roller 9a falls down into the valley of the range engagement groove, the clutch 19 is released taking account of inertia of respective parts so that the valley 5g" of the range engagement groove 5g bears the roller 9a. In addition, since it is difficult for the valley 5g" to surely bear the roller 9a, the range engagement groove 5g bears the roller 9a in some region (a detent lever rotation stopping region W) around the valley 5g". The region W is set in a range of error in range switchover of the manual valve 2, and is one, in which oil pressure is generated due to the range switchover of the manual valve 2. However, even when timing for stopping the motor 12 is set taking account of inertia of respective parts, a driver is in some cases given an uncomfortable feeling because the rotational speed of the motor 12 has changed in long term use to vary a time required for range switchover. Therefore, the range switchover apparatus 1 according to the invention is designed as described above to correct and store the duty ratio the motor 12 so that a range switchover time comes within a target time next time. In addition, while an explanation has been given to the operation in the case where the detent lever 5 in the range switchover apparatus 1 according to the embodiment rotates in the direction of the arrow D, it rotates in some cases in the direction of the arrow C. In Fig. 8, a position of the detent lever 5 relative to the roller 9a at the time of release of the clutch is in the vicinity of a point E (in the vicinity of inlets 5d' , 5e', 5f', 5g' and 5h' ) in the case where the detent lever 5 rotates in the direction of arrow D, and is in the vicinity of a point J (in the vicinity of inlets 5d', 5e', 5f', 5g' and 5h') in the case where the detent lever rotates in the direction of the arrow C. In addition, the range engagement groove indicated by the character 5d is formed to have a valley of greater depth than that of the other range engagement grooves. While the range switchover apparatus according to the embodiment has been explained taking the N-D shift as an example, it is applicable to the other shifts such as P-R shift and D-L shift. Also, control may be performed not only between adjacent ranges, but also in P-D shift with a target time set. Also, while the range switchover apparatus according to the embodiment has been explained taking the apparatus with the clutch 19 as an example, it is applicable to an apparatus, which is not provided with any clutch and in which a drive motor and a manual valve are connected to each other at all times. Further, because the detent lever 5 is biased by the roller 9a, which is provided on the detent spring 9 with elasticity, it seems that in the case where the roller 9a abuts against an inclined surface of the range engagement groove, the detent lever is exerted by the bias of the roller 9a to rotate to enable bearing the roller 9a on the valley of the range engagement groove. However, the detent lever hardly rotates biased by the roller 9a because there is provided the worm 12b for decelerating the rotation of the motor 12. According to the invention, even when the drive motor changes in rotational speed to lead to delaying of the range switchover time due to secular change, it is possible to automatically control the rotational speed to a predetermined rotational speed so that a switchover time comes within a target time. So, the switchover valve can be correctly switched over within the target time. Further, according to the invention, a target time is set in accordance with the environmental condition, and so it is possible to surely switch over the switchover valve within the target time in response not only to secular change but also to a change in environment.

Claims: A range switchover apparatus for automatic transmissions, comprising: a range switchover means operating unit (5, 7) capable of switching over a switchover means (2), which switches over a shift range, among respective shift positions; a drive motor (12) for driving the range switchover means operating unit; a rotation control unit (35) for controlling the rotational speed of the drive motor; characterised in that it further comprises a measuring unit (28, 32) for measuring a time, during which the drive motor causes the range switchover means operating unit to switch over between predetermined shift positions; a correcting unit (34) for correcting the rotational speed by the rotation control unit so that when a time measured by the measuring unit differs from a target time in a predetermined range, the measured time becomes the target time; and a storage unit (33) for storing the rotational speed corrected by the correcting unit. The range switchover apparatus for automatic transmissions according to claim 1, wherein the target time is one set in accordance with an environmental condition, the rotation control unit controls the rotational speed of the drive motor on the basis of a duty ratio of the drive motor, and the correcting unit compares the measured time and the target time with each other to correct the duty ratio so as to make the same large when the measured time exceeds the target time and to correct the duty ratio so as to make the same small when the measured time is shorter than the target time.

Inventors: EISHIMA HIROTOSHI, KUSAFUKA MUNEO, MURASE YOSHITAKA, OHKOSHI NAOKI, TAKEMOTO KAZUO, EISHIMA, HIROTOSHI, KUSAFUKA, MUNEO, MURASE, YOSHITAKA, OHKOSHI, NAOKI, TAKEMOTO, KAZUO, Eishima, Hirotoshi, c/o AISIN AW CO., LTD., Kusafuka, Muneo, c/o Aisin AW Co., Ltd., Murase, Yoshitaka, c/o AISIN AW CO., LTD., Ohkoshi, Naoki, c/o AISIN AW CO., LTD., Takemoto, Kazuo, c/o AISIN AW CO., LTD.
Applicants: AISIN AW CO, AISIN AW CO., LTD.
Application year: 2000
Main classification: F16H59
IPC codes: F16H61, F16H59