ACTUATOR FOR AN AUTOMATED OR AUTOMATIC TRANSMISSION, AND METHOD FOR CONTROLLING THE ACTUATOR

Abstract

The invention relates to an actuator (1) for an automated or automatic transmission, having a cylinder housing (3), a piston unit (2), and a piston rod (13), wherein the piston unit (2) is coupled to the piston rod (13) and is arranged movably in the cylinder housing (3) along an axial longitudinal axis (4), wherein the piston unit (2) separates from each other two pressure chambers (8, 9) of variable volume in the cylinder housing (3), by means of which pressure chambers the piston unit (2) can be loaded with compressed air on both sides, wherein the two pressure chambers (8, 9) are connected to a valve unit (14) which is able to switch the pressurization or purging of each of the two pressure chambers (8, 9), and wherein an end stop damping device for damping at least one end stop of the piston unit (2) is arranged in the actuator (1). In order to improve the end stop damping device, a pneumatically and a mechanically operating damping stage are provided.

Claims

1. An actuator (1) for an automated or automatic transmission, the actuator comprising: a cylinder housing (3), a piston unit (2), an end stop damping device, and a piston rod (13), wherein the piston unit (2) is coupled to the piston rod (13) and arranged in the cylinder housing (3) to be movable in two opposite directions along a longitudinal axis (4), wherein the piston unit (2) separates two pressure chambers (8, 9) of variable volume in the cylinder housing (3), the pressure chambers being configured to apply pressure to the piston unit (2) with compressed air from opposite sides, wherein the two pressure chambers (8, 9) are configured to be connected to a valve unit (14) configured to selectively switch between a pressurization or a purge of each of the two pressure chambers (8, 9), and wherein an end stop damping device is arranged in the actuator (1) for damping at least one end stop of the piston unit (2) and is composed of a first pneumatically active damping stage and a second mechanically active damping stage, wherein the first pneumatically active damping stage is configured to reduce the kinetic energy of the piston unit (2) in at least one movement direction thereof when the piston unit (2) approaches at least one of two opposite end stop faces (5, 6), wherein the first pneumatically active damping stage is formed on the cylinder housing (3) by a pneumatic damping element (19, 20), wherein the pneumatic damping element (19, 20) has an air outlet (34, 35) with a variable cross-sectional area for compressed air, which is configured to be pneumatically connected to a respective one of the two pressure chambers (8, 9) by switching the valve unit (14) into a purge position for the respective one of the two pressure chambers (8, 9), wherein the cross-sectional area (28, 29) of the air outlet (34, 35) is adjustable by a prevailing pressure in the respective pressure chamber (8, 9) connected thereto, and wherein the second mechanically active damping stage is configured to dissipate a kinetic energy of the piston unit (2) remaining after braking by the pneumatic damping element (19, 20), when the piston unit (2) reaches the at least one end stop face (5, 6).

2. The actuator as claimed in claim 1, wherein the end stop damping device is operative for both opposite directions of movement of the piston unit (2), wherein the first pneumatically active damping stage comprises a first pneumatic damping element (19) for a first movement direction of the two opposite directions, and a second pneumatic damping element (20) for a second movement direction of the two opposite directions, the first and second pneumatic damping elements being assigned to the valve unit (14), and wherein the second mechanically active damping stage comprises a first mechanical damping element (40) for stopping the piston unit (2) at a first end stop face (5) of the two end stop faces and a second mechanical damping element (41) for stopping the piston unit (2) at an opposite second end stop face (6) of the two end stop faces, the first and second mechanical damping elements being arranged on the piston unit (2).

3. The actuator as claimed in claim 2, wherein the first pneumatic damping element (19) is configured to be controlled by a first 3/2-way magnetic valve (15, 17) of the valve unit (14), that the second pneumatic damping element (20) is configured to be controlled by second 3/2-way magnetic valve (15, 17) of the valve unit (14) wherein the first and second pneumatic damping elements (19, 20) each have an air outlet flap (21, 22) formed as an elastic lip arranged on a first or second outlet opening (23, 24) of a first or second air outlet (34, 35) respectively connected to the first pressure space (8) or the second pressure space (9) via the first or the second 3/2-way magnetic valve, wherein the air outlet flap (21) is attached unilaterally to an associated one of the first and second air outlet openings (23, 24) such that the air outlet flap (21, 22) lies tightly under spring preload on the associated air outlet opening (23, 24) under atmospheric pressure and by overcoming the spring preload, lifts away from the respective air outlet opening (23, 24) on pressurization of the air outlet flap (21, 22) from the first or second pressure chamber (8, 9) when a pressure threshold value is exceeded, wherein each of the two air outlet flaps (21, 22) includes a respective permanently open passage opening (26, 27), the passage opening having a cross-sectional area substantially smaller than the respective air outlet opening (23, 24) associated with the air outlet flap (21, 22), wherein the air outlet openings (23, 24) which can be opened pressure-dependently are substantially smaller than a cross-sectional area (32) of the piston unit (2).

4. The actuator as claimed in claim 1, wherein the piston unit (2) has a radially inner main piston (10) fixedly connected to the piston rod (13), wherein the main piston (10) carries a first auxiliary piston (11) assigned to a first pressure chamber (8) of the two pressure chambers and a second auxiliary piston (12) assigned to a second pressure chamber (9) of the two pressure chambers, that the first and second auxiliary pistons (11, 12) are arranged radially above the main piston (2) with limited displaceability relative thereto and coaxial with the longitudinal axis (4), wherein the second mechanically active damping stage includes a first mechanical damping element (40), formed as a rubber buffer arranged on the first auxiliary piston (11) at a piston end proximate to the first end stop face (5) of the cylinder housing (3), and a second mechanical damping element (41), formed as a rubber buffer arranged on the second auxiliary piston (12) at a piston end proximate to the second end stop face (6) of the cylinder housing (3).

5. The actuator as claimed in claim 2, wherein the first and second pneumatic damping elements (19, 20) are combined in a valve block of the valve unit (14).

6. The actuator as claimed in claim 2, wherein the first and second pneumatic damping elements (19, 20) are directly integrated in a respective assigned 3/2-way magnetic valve (15, 17) of the valve unit (14).

7. The actuator as claimed claim 2, wherein the first and second an effective dead volume (39) which remains in an end position of the piston unit (2) and includes a free volume in the region between the piston unit (2) and the first or second end stop face (5, 6) in the respective pressure chamber (8, 9), and a volume of a pneumatic connection between the respective pressure chamber (8, 9) and the assigned air outlet opening (23, 24) of the respective pneumatic damping element (19, 20), is dimensioned to be minimal.

8. A method for controlling the actuator (1) as claimed in claim 1, the method comprising the following steps: pressurizing one of the two pressure chambers (8, 9), with a positive pressure (p(t)_1) and simultaneously purging the other of the two pressure chambers (9, 8) to drive a movement of the piston unit (2) coaxially to the longitudinal axis (4), performing a two-stage damping for damping the at least one end stop of the piston unit (2) at the at least one end stop face (5, 6) in the actuator (1), by first activating the first pneumatically active damping stage, via the pneumatic damping element (19, 20), when the piston unit (2) approaches the end stop face (5, 6), by producing a self-regulating counter-pressure (p(t)_2) countering the piston movement in the one of the two pressure chambers (8, 9) that is to be purged, wherein the cross-sectional area (28, 29) of the air outlet (34, 35) of the pneumatic damping element (19, 20) is automatically adjusted by the prevailing pressure, and subsequently, when the piston unit reaches the end stop face (5, 6), dissipating the remaining kinetic energy of the piston unit (2) by elastic deformation of a mechanical damping element (40, 41) of the second mechanically active damping stage.

9. The method as claimed in claim 8, wherein a temporal curve of an air mass flow (dm/dt_1, dm/dt_2, dm/dt_3) of a respective purging of the one pressure chamber (8, 9), and a temporal curve depending thereon of an adjustment travel (x(t)) of the piston unit (2), are at least approximately established by calculation using a simulation algorithm, of a first air outlet (34) or second air outlet (34, 35), wherein cross-sectional areas (28, 29, 30, 31) of a permanently open first or second passage opening (26, 27) and the pressure-dependently open first or second air outlet opening (23, 24), and a spring preload active in a closing direction of a first or second air outlet flap (21, 22), are matched to each other taking into account a predefined pressure level of a compressed air supply (36).

10. An automated or automatic transmission in a drive train of a motor vehicle, with at least one actuator (1) as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In the drawings,

[0039] FIG. 1 shows a schematic, longitudinal cross-section through a piston unit in a partial view in a neutral position in an actuator;

[0040] FIG. 2 shows the piston unit of FIG. 1 in an end position;

[0041] FIG. 3 shows a circuit diagram of a valve unit for controlling and damping the end position of the piston unit of FIG. 1 and FIG. 2;

[0042] FIG. 4 shows an enlarged detail of a pneumatic damping element of a valve unit from FIG. 3 with an air outlet flap in a first operating position;

[0043] FIG. 5 shows the detail of FIG. 4 with the air outlet flap in the second operating position;

[0044] FIG. 6 shows a combined travel-time diagram and speed-time diagram of a shift collar actuated by a piston unit in an automated transmission, with a two-stage end position damping of the piston unit according to the invention;

[0045] FIG. 7a shows a pressure-time diagram of the pressures in two pressure chambers of the piston unit on actuation of the shift collar of FIG. 6;

[0046] FIG. 7b shows the diagram according to FIG. 6 for comparison; and

[0047] FIG. 7c an air mass flow-time diagram of purging of a pressure chamber via the valve unit of FIG. 3 and according to FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE DRAWINGS

[0048] Accordingly, an actuator 1 shown in FIG. 1 and FIG. 2 of an automated transmission comprises a piston unit 2, configured as a shift piston, which is arranged to slide coaxially with a longitudinal axis 4 in a cylinder housing 3, formed as a shift cylinder. The piston unit 2 moves in a piston chamber 7 of the cylinder housing 3 between a first end stop face 5 and a second end stop face 6, wherein the piston unit 2 divides the piston chamber 7 into two pressure chambers 8, 9 which can be loaded with compressed air and are sealed against each other. The piston unit 2 consists of a main piston 10 and two auxiliary pistons 11, 12. A piston rod 13 is attached to the main piston 10 and is mounted so as to slide in the cylinder housing 3 and is guided along the longitudinal axis 4. The connection between the main piston 10 and the piston rod 13 is configured for example as a second screw connection 37.

[0049] The piston rod 13 is in engagement with or actively connected with a shift element of a shift clutch, for example a sliding collar (not shown), in the known fashion. The two auxiliary pistons 11, 12 are mounted sliding radially outside and coaxially to the main piston 10 and are axially displaceable relative thereto, wherein the first auxiliary piston 11 is arranged in the first pressure chamber 8 and the second auxiliary piston 12 is arranged in the second pressure chamber 9. The maximum adjustment travels of the two auxiliary pistons 11, 12 are approximately the same, and are limited by an annular travel-limiting component 38 arranged approximately centrally in the piston chamber 7. The first auxiliary piston 11 may thus move between the first end stop face 5 and one of the end faces of the travel-limiting component 38, and the second auxiliary piston 12 may move between the second end stop face 6 and the other end face of the travel-limiting component 38.

[0050] To damp the end stop of the piston unit 2 on the first end stop face 5 of the cylinder housing 3, a first mechanical damping element 40, formed as a rubber buffer, is mounted on the end face of the first auxiliary piston 11 facing the first end stop face 5. To damp the end stop of the piston unit 2 on the second end stop face 6 of the cylinder housing 3, a second mechanical damping element 41, formed as a rubber buffer, is attached to the end face of the second auxiliary piston 12 facing the end stop face 6. The two mechanical damping elements 40, 41 protrude beyond the end faces of the respective auxiliary pistons 11, 12. Each of the two mechanical damping elements 40, 41 is therefore active in one adjustment direction of the piston unit 2 as a mechanical damping stage of a two-stage end stop damping device of the piston unit 2.

[0051] The two pressure chambers 8, 9 of the piston chamber 7 are connected to a valve unit 14 (FIG. 3). The valve unit 14 has a first 3/2-way magnetic valve 15 which is connected to the first pressure chamber 8 via a first pneumatic connecting line 16, and a second 3/2-way magnetic valve 17 which is connected to the second pressure chamber 9 via a second pneumatic connecting line 18. The two pressure chambers 8, 9 can be connected to a compressed air supply 36 via the two magnetic valves 15, 17, as indicated merely by one pneumatic connecting line in FIG. 3. For purging to the environment, the two pressure chambers 8, 9 can be connected to a purge line 42 via the two magnetic valves 15, 17.

[0052] As FIG. 3 furthermore shows, the valve unit 14 has a first pneumatic damping element 19 which is pneumatically connected to the first 3/2-way magnetic valve 15. Also, a second pneumatic damping element 20 is present, which is pneumatically connected to the second 3/2-way magnetic valve 17. Each of the two pneumatic damping elements 19, 20 is active in one adjustment direction of the piston unit 2 as a pneumatic damping stage of the two-stage end stop damping device of the piston unit 2.

[0053] The two pneumatic damping elements 19, 20 may be integrated in a valve block (not shown further) which also receives the two 3/2-way magnetic valves 15, 16. Since they are configured identically, it is sufficient to describe in more detail one of the two pneumatic damping elements 19, 20. FIG. 4 and FIG. 5 each show a detail extract of one of the two pneumatic damping elements 19, 20. The double reference signs apply accordingly to the first pneumatic damping element 19 or the second pneumatic damping element 20. Accordingly, the first/second pneumatic damping element 19, 20 has a first/second air outlet flap 21, 22 formed as an elastic lip, which bears under preload in the closing direction on a first/second air outlet opening 23, 24 of a first/second air outlet 34, 35. For this, at one end, the air outlet flap 21, 22 is clamped between a first screw connection 25 and the body of the pneumatic damping element 19, 20. The first/second air outlet flap 21, 22 has a first/second passage opening 26, 27 configured as a bore, which in contrast to the first/second air outlet opening 23, 24 cannot be closed but is permanently open. The size ratios of the piston unit 2, air outlet flap 21, 22 and passage opening 26, 27, are designed such that a first/second active cross-sectional area 28, 29 of the first/second air outlet opening 23, 24 is substantially larger than a third/fourth active cross-sectional area 30, 31 of the first/second passage opening 26, 27, but substantially smaller than a fifth/sixth active cross-sectional area 32, 33 of the piston unit 2 (FIG. 1 and FIG. 2). The latter two cross-sectional areas 32, 33 are defined by the respective, pneumatically active end faces of the piston unit 2 on the pressure chamber side.

[0054] The function of the piston unit 2 with the end stop damping device described is as follows:

[0055] In the operating situation shown in FIG. 1, the piston unit 2 is in a neutral position and therefore positioned centrally in the piston chamber 7. The two auxiliary pistons 11, 12 are situated at the respectively assigned end face of the travel-limiting component 38. The main piston 10 lies between the auxiliary pistons 11, 12. The two 3/2-way magnetic valves 15, 17 of the valve unit 14 (FIG. 3) are switched to the same one of two possible switch positions, here a purge position. The two pressure chambers 8, 9 are purged via the associated pneumatic damping elements 19, 20, or more precisely via the passage openings 26, 27 of the air outlet flaps 21, 22 at the air outlets 34, 35 of the pneumatic damping elements 19, 20 (FIG. 4). In this operating situation, a pressure balance takes place between the pressure chambers 8, 9 and the surrounding atmosphere.

[0056] In order to move the piston rod 13 for example to the right from the position shown in FIG. 1, the first pressure chamber 8 is loaded with compressed air. For this purpose, the first 3/2-way magnetic valve 15 is switched into its other switch position, here a pressure position. In this pressure position of the first 3/2-way magnetic valve 15, the first pressure chamber 8 is pneumatically connected to a compressed air supply 36. The main piston 10 begins to move and carries the attached piston rod in the same movement direction coaxially to the longitudinal axis 4 (to the right in the viewing direction). In doing so, the main piston 10 pushes the second auxiliary piston 12, i.e. the auxiliary piston in the opposite second pressure chamber 9, before it in the direction towards the second end stop face 6. The first auxiliary piston 11 remains stationary at the travel-limiting component 38.

[0057] The second 3/2-way solenoid valve 17 remains in the purge position so that the second pressure chamber 9 is purged. On purging of the second pressure chamber 9, the pneumatic damping stage of the two-stage end stop damping device of the piston unit 2 becomes active. This is illustrated in the simulation diagrams in FIG. 6 and FIG. 7a-c. In the diagrams, the movement of the piston unit 2 is represented by the adjustment travel of a sliding collar. This is equivalent to a movement of the piston unit 2, so that for simplification, the description below refers to a piston movement.

[0058] FIG. 6 and FIG. 7b show the temporal travel curve x(t) of a piston movement and an associated speed curve v(t) of this piston movement. FIG. 7a shows an associated temporal pressure curve p_1(t) of the pressurization of the first pressure chamber 8, and a counter-pressure curve p_2(t) of the purging of the second pressure chamber 9. Also, the associated respective switch positions of the first 3/2-way magnetic valve 15 (pressurization of pressure chamber 8) and the second 3/2-way magnetic valve 17 (purging of pressure chamber 9) are shown. FIG. 7c shows, for purging of the second pressure chamber 9, an associated temporal curve dm/dt_1 of a first air mass flow through the passage opening 27 in the air outlet flap 21, 22, a temporal curve dm/dt_2 of a second air mass flow through the air outlet opening 24, and a resulting temporal curve of a total air mass flow dm/dt_3=dm/dt_1+dm/dt_2 of the purging.

[0059] Accordingly, the pressure p(t)_1 in the first pressure chamber 8 rises due to pressurization by means of the compressed air supply 36 (FIG. 7a). In the second pressure chamber 9 to be purged, initially only the small cross-sectional area 30 of the passage opening 26 of the air outlet 34 is active. The air outlet flap 21 lies preloaded in the closing direction against the air outlet opening 23 and closes this. Since the piston unit 2 moves into the second pressure chamber 9, the air therein is compressed and the pressure p(t)_2 increases, since the air mass flow dm/dt_1 for purging is limited by the cross-sectional area 30 of the passage opening 26 in the air outlet flap 21, which is small in comparison with the cross-sectional area 32 of the piston unit 2 (FIG. 7c).

[0060] The pressure p(t)_2 in the second pressure chamber 8 acts as a counter-pressure which reduces the piston speed v(t) and thereby damps the piston movement (FIG. 7b). The counter-pressure then exceeds the spring preload of the air outlet flap 21 and opens this, so that the larger cross-sectional area 29 of the air outlet opening 24 is activated and effective in a time window Δt. Correspondingly, purging is intensified by the larger air mass flow dm/dt_2. As a result, the piston unit 2 is accelerated and quickly reaches the second end stop face 6 (FIG. 2). Here, by impact of the second auxiliary piston 12 on the first end stop face 5, the mechanical damping stage becomes active. The mechanical damping element 41 formed as a rubber buffer is elastically deformed and thereby converts the residual kinetic energy of the piston unit 2 into heat, so that this remains in its end position. In this end position of the piston unit 2, the second pressure chamber 9 is almost completely purged. Only a small dead volume 39 (shown filled in black in FIG. 2) remains in the second pressure chamber 9.

[0061] While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.