Actuator for operating frictional fastening elements

Abstract

To improve responsiveness and also to secure pressing force in fastening, while miniaturizing a motor in an operation actuator of a friction fastening element.SOLUTION: An operation actuator 2 of a friction fastening element 1 has: a motor 21; a screw mechanism 22 for converting torque of the motor 21 into a linear motion; and a hydraulic circuit 24 in an oil-tight state, including a piston 24c to which the linear motion of the screw mechanism 22 is transmitted to press a friction plate 13. The screw mechanism 22 includes: a first pitch region X1 on which a first pitch X11 positioned at an axial one side of a screw shaft 22a is formed; and a second pitch region X2 which is continuous to the first pitch region X1 and on which a second pitch X21 positioned at the axial other side is formed. The second pitch X21 is formed to be smaller than the first pitch X11, and the first pitch X11 and the second pitch X21 are determined so that the piston 24c is switched at a zero clearance position.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an actuator for operating a frictional fastening element mounted on a vehicle such as an automobile. [Background technology]

[0002] The frictional engagement elements installed in a vehicle are, for example, connected to a drive source such as an engine and installed in an automatic transmission equipped with multiple planetary gear sets. The automatic transmission is configured to selectively engage the multiple frictional engagement elements to switch the power transmission path passing through each planetary gear set to achieve multiple forward gears and usually one reverse gear.

[0003] As the frictional fastening element, there is known a frictional fastening element that includes a plurality of friction plates and a piston that presses the plurality of friction plates to fasten the frictional fastening elements when hydraulic pressure is supplied to a hydraulic chamber, and that uses the hydraulically actuated piston to fasten and release the frictional fastening elements.

[0004] However, the oil pressure supplied to the hydraulic chamber is generated by an oil pump driven by the engine, and the supply of working oil to the frictional engagement elements is controlled by a hydraulic control device equipped with multiple solenoid valves. As a result, oil leaks occur from the multiple solenoid valves, etc., and as a result, a drive loss occurs in order to maintain the oil pressure of the hydraulic control device by driving the oil pump even in the disengaged state, causing energy loss.

[0005] In response to this, instead of using a hydraulic control device such as an oil pump and multiple solenoid valves as a frictional fastening element, it is conceivable to reduce drive loss by maintaining hydraulic pressure in a non-engaged state by engaging and releasing the frictional fastening element using an electric motor, a conversion mechanism that converts the rotational motion of the electric motor into linear motion, and a hydraulic piston that constitutes an oil-tight hydraulic circuit.For example, Patent Document 1 discloses the use of an actuation actuator that includes an electric motor, a conversion mechanism, a master piston connected to the conversion mechanism, a hydraulic master cylinder in which the master piston is fitted, a hydraulic slave cylinder fluidly connected to the hydraulic master cylinder, and a slave piston that is fitted to the slave cylinder and presses a friction plate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-514198 A Summary of the Invention [Problem to be solved by the invention]

[0007] In order to improve responsiveness when the frictional fastening element is engaged, the clearance between multiple friction plates becomes zero and the position of the piston is set to a zero clearance position where the piston does not press against the friction plates and the tip of the piston is in contact or nearly in contact with the friction plates (hereinafter also referred to as the "zero clearance state").

[0008] From the piston release position to the zero clearance position, it is desirable to increase the piston stroke speed due to the requirement for responsiveness, and from the zero clearance position to the engaged position, it is desirable to generate the pushing force (pushing force) necessary to engage the frictional engagement element.

[0009] When attempting to achieve the above requirements with the actuation actuator of Patent Document 1, it is conceivable to use a high-output motor that is rated to output the maximum required rotational speed corresponding to the stroke speed required of the piston of the frictional fastening element and the maximum required torque corresponding to the pushing force required of the piston; however, it is desirable to improve mountability by making the actuation actuator more compact.

[0010] The present invention provides an actuator for operating a frictional fastening element, which is capable of achieving both improved responsiveness during fastening and a sufficient pressing force while miniaturizing the motor.

[0011] The present invention provides an actuator for operating a friction fastening element, which is provided between a drum and a hub and presses a plurality of friction plates alternately engaged with the drum and the hub to fasten them together, a motor, a screw mechanism that converts a rotational force of the motor into linear motion, a piston that presses the friction plate, and an oil-filled chamber in an oil-tight state that is filled with hydraulic oil that transmits the linear motion of the screw mechanism to the piston, The screw mechanism is composed of a ball screw mechanism having a screw shaft and a nut that moves axially on the screw shaft and transmits a pressing force to the piston via the oil filling chamber, and the screw shaft has a first pitch region in which a first pitch is formed on one side in the axial direction, and a second pitch region in which a second pitch is formed on the other side in the axial direction, continuous with the first pitch region, and is formed so that the second pitch is smaller than the first pitch, The first pitch The second pitch region is provided at a position corresponding to a zero clearance position where the piston moves from a release position of the piston to a zero clearance state where the piston closes the clearance of the friction plate, and the second pitch region is provided at a position corresponding to a fastening position from the zero clearance position. An actuator for operating a friction fastening element.

[0012] According to the present invention, by using a so-called variable pitch ball screw mechanism having a screw mechanism with first and second pitches that are different from each other, it is possible to increase the stroke speed from the released position of the piston to the zero clearance position without increasing the size of the motor, and to reduce the stroke speed while ensuring the pressing force required for engaging the frictional engagement element from the zero clearance position of the piston to the fully engaged position.

[0013] For example, by setting the first pitch to the maximum stroke speed during fastening and the second pitch to the maximum required torque during fastening, a smaller motor can be used compared to a large motor capable of outputting the maximum rated rotation speed and maximum required torque. This allows the use of a small motor that is easy to mount while improving the stroke speed of the piston from the release position to the zero clearance position and ensuring the fastening torque required after the zero clearance position.

[0014] The contact area can be reduced compared to when a sliding screw mechanism is used for the screw mechanism, and the screw efficiency is improved, which allows the motor torque to be reduced and the motor to be made smaller. The actuator is composed of a ball screw mechanism, an oil-tight oil-filled chamber, and a piston, so energy loss for maintaining pressure in the non-engaged state can be suppressed compared to when a hydraulic pump is driven to maintain hydraulic pressure in the non-engaged state.

[0015] a piston position detection means for detecting a zero clearance position of the piston at the time of manufacture; a deviation amount calculation means for calculating a deviation amount between the zero clearance position at the time of manufacture detected by the piston position detection means and a boundary position between the first pitch region and the second pitch region; and a stroke correction means for correcting an axial position of the nut when the piston is located at a release position based on the deviation calculated by the deviation calculation means, thereby correcting a stroke amount of the piston from the predetermined release position to the clearance position.

[0016] According to this configuration, by correcting the axial position of the nut based on the value of the piston position detection means which detects the zero clearance position at the time of manufacture, where the piston is in a state including manufacturing errors of multiple friction plates, it is possible to correct the deviation between the boundary position due to manufacturing errors of the multiple friction plates and the zero clearance position at the time of manufacture.Therefore, even if manufacturing errors occur in the multiple friction plates, it is possible to achieve both responsiveness during fastening, ensured pressing force, and precise controllability.

[0017] Specifically, for example, if the zero clearance position deviates from the boundary position toward the fastening side due to manufacturing errors in multiple friction plates, the deviation between the zero clearance position and the boundary position can be corrected by correcting the axial position of the nut in the released state to one axial side (release side) by the amount of stroke that is required to extend from the released position to the zero clearance position.

[0018] On the other hand, if the zero clearance position has shifted toward the release side from the boundary position due to manufacturing errors in multiple friction plates, the deviation between the zero clearance position and the boundary position can be corrected by correcting the axial position of the nut in the released state to the other axial side (fastened side) by the amount of stroke that needs to be shortened from the release position to the zero clearance position.

[0019] The piston position detection means may be configured to detect the as-manufactured zero clearance position of the piston at a rise in hydraulic pressure in the oil filling chamber.

[0020] According to this configuration, the oil pressure in the oil filling chamber rises at the as-manufactured zero clearance position where the piston moves from the released position to the engaged side to close the clearance of the friction plate. Therefore, even if a manufacturing error in the friction plate or the like causes a discrepancy between the amount of stroke from the predetermined released position of the piston to the as-manufactured zero clearance position and the amount of stroke from the predetermined released position of the piston to the zero clearance position at the time of design, the as-manufactured zero clearance position can be accurately detected.

[0021] The piston position detection means may be constituted by a hydraulic switch.

[0022] According to this configuration, the zero clearance position of the piston is detected by the rise in oil pressure due to the fastening of the friction plates using an oil pressure switch, so that the zero clearance position can be detected with a cheaper configuration than when an oil pressure sensor or the like is used.

[0023] The piston position detection means may be constituted by a hydraulic sensor.

[0024] According to this configuration, the zero clearance position of the piston is detected by the hydraulic pressure sensor based on the rise in hydraulic pressure caused by the engagement of the friction plates, so that more precise control can be obtained compared to the case where a hydraulic pressure switch is used. Effect of the Invention

[0025] According to the present invention, it is possible to provide an actuator for operating a frictional fastening element, which can achieve both improved responsiveness during fastening and a sufficient pressing force while miniaturizing the motor. [Brief description of the drawings]

[0026] [Figure 1] FIG. 4 is a schematic diagram of an actuator of the frictional fastening element according to the embodiment of the present invention in a released state. [Diagram 2] FIG. 2 is a schematic diagram of an actuator of a frictional fastening element in a zero clearance state. [Diagram 3] FIG. 4 is a schematic diagram of an actuator of a frictional fastening element in an engaged state. [Figure 4] 11 is an explanatory diagram for explaining correction of a stroke amount in a case where a zero clearance position at the time of manufacture of a piston is shifted to the fastening side by correcting the axial position of a nut. FIG. [Diagram 5] FIG. 4 is a schematic diagram showing the pitch of a screw shaft corresponding to the stroke of a piston. [Figure 6] 1 is a block diagram showing a configuration of a control device for an automatic transmission equipped with a frictional engagement element; [Figure 7]11 is an explanatory diagram for explaining correction of a stroke amount in a case where a zero clearance position at the time of manufacture of a piston is shifted to the release side by correcting the axial position of a nut. FIG. [Figure 8] 6 is a flowchart illustrating a method for correcting a stroke amount of a piston. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0028] 1 is a schematic diagram of an actuation actuator 2 of a frictional engagement element 1 according to an embodiment of the present invention, showing the disengaged state of the actuation actuator 2 of the frictional engagement element 1. The actuation actuator 2 has a function of adjusting the clutch clearance (the value obtained by subtracting the total thickness of all friction plates from the dimension between the engagement piston and the retaining plate) in order to improve the responsiveness of the frictional engagement element 1 when it is engaged. The frictional engagement element 1 may be, for example, a plurality of clutches and brakes provided in an automatic transmission (not shown), and the actuation actuator 2 is provided in each of the frictional engagement elements.

[0029] The clutch as the frictional fastening element 1 includes a cylindrical drum 11, a cylindrical hub 12 having a smaller diameter than the drum 11, a plurality of friction plates 13 arranged in the axial direction between the drum 11 and the hub 12 and alternately spline-engaged with the drum 11 and the hub 12, and an operating actuator 2 that presses the plurality of friction plates 13 to fasten them together. The plurality of friction plates 13 are pressed by a piston 23 provided in the operating actuator 2, whereby the clutch 1 is fastened.

[0030] Among the friction plates 13, the friction plates 13a arranged inside the drum 11 are spline-engaged with the drum 11 so as to be movable in the axial direction and to be rotatable integrally with the drum 11. The friction plates 13b arranged outside the hub 12 are spline-engaged with the hub 12 so as to be movable in the axial direction and to be rotatable integrally with the hub 12. The friction plates 13a of the drum 11 and the friction plates 13b of the hub 12 are alternately arranged and face each other via facings 13c provided on both sides of the friction plates 13b of the hub 12. A retaining plate 15 is spline-engaged with the drum 11 like the friction plates 13a of the drum 11 on the other axial side of the friction plates 13, and is prevented from coming off from one axial side by a snap ring 14.

[0031] The piston 23 is disposed on one axial side of the friction plates 13, and is fitted so as to be axially movable in a second cylinder 26b that constitutes a part of the oil filling chamber 26. On one axial side of the piston 23, a hydraulic chamber 27 is formed in an oil-tight manner by the second cylinder 26b and the piston 23.

[0032] An oil passage 27a provided in the second cylinder 26b is connected to the hydraulic chamber 27, and the oil passage 27a communicates with the other axial side of the first cylinder 26a via a hydraulic line 26c. The first piston 24 is fitted into one axial side of the first cylinder 26a. A return spring (not shown) is provided on the other axial side of the second piston 23 to bias the second piston 23 to one axial side.

[0033] The operating actuator 2 has an electric motor 21, a screw mechanism 22 that converts the rotational force of the electric motor 21 into linear motion, a piston 24c to which the linear motion of the screw mechanism 22 is transmitted to press the friction plate 13, and an oil-tight oil-filled chamber 26 filled with hydraulic oil that transmits the linear motion of the screw mechanism 22 to the piston 23.

[0034] The electric motor 21 is, for example, a brushless motor. A motor rotation speed sensor (for example, a magnetic sensor such as a Hall element) 35 is disposed on the side of the stator (not shown) facing the magnetic poles of the rotor (not shown). The motor rotation speed is calculated from a waveform having a constant period, which is synthesized based on a position detection signal from the Hall element. The position signal detected by the motor rotation speed sensor 35 is input to the control device 30 (see FIG. 7).

[0035] The screw mechanism 22 is, for example, a ball screw device equipped with a top-type ball circulation mechanism. The screw mechanism 22 includes a screw shaft 22a, a nut 22b that moves in the axial direction with the rotation of the screw shaft 22a, and a plurality of rolling elements (not shown) interposed between the screw shaft 22a and the nut 22b. The screw shaft 22a in this embodiment is configured by the rotating shaft of the electric motor 21, but may be configured so that power is transmitted to the screw shaft 22a via a gear or the like.

[0036] A ball rolling groove 22c having a substantially semicircular arc shape is formed in a spiral shape on the outer circumferential surface of the screw shaft 22a. The ball rolling groove 22c is formed so that the pitch changes at different positions in the axial direction of the screw shaft 22a. The screw mechanism 22 in this embodiment is configured with a pitch variable ball screw mechanism. Details of the pitch of the screw shaft 22a will be described later.

[0037] A nut rolling groove (not shown) having a substantially semicircular shape facing the ball rolling groove 22c of the screw shaft 22a is formed on the inner peripheral surface of the nut 22b. The balls are disposed between the ball rolling groove 22c and the nut rolling groove (not shown). As a result, the ball rolling groove 22c and the nut rolling groove are screwed together via the balls, and the balls roll and circulate in the circulation path by rotating the screw shaft 22a with the electric motor 21, thereby moving the nut 22b in the axial direction.

[0038] The nut 22b and the first piston 24 fitted in a first cylinder 24a (described later) constituting a part of the oil filling chamber 26 are connected by a connecting member 25. The first piston 24 is configured to move in the axial direction in conjunction with the movement of the nut 22b in the axial direction.

[0039] The oil filling chamber 26 has a first cylinder 26a that houses a first piston 24 connected to the nut 22b via a connecting member 25, a second cylinder 26b that houses a piston (second piston) 23 that presses the multiple friction plates 13, a hydraulic line 26c that connects the first and second cylinders 26a and 24d, and a reservoir tank 26e that can be connected to the first cylinder 26a via a connection part 26d provided on the first cylinder 26a. In this embodiment, the second piston 23 corresponds to the piston 23 that presses the friction plates 13.

[0040] The first cylinder 26a, the hydraulic line 26c, the second cylinder 26b, and the reservoir tank 26e are filled with hydraulic oil and are in an oil-tight state. The connection 26d is provided with a check valve 26f that is opened only when the hydraulic pressure in the first cylinder 26a falls below the hydraulic pressure in the reservoir tank 26e. The reservoir tank 26e is not sealed against the surrounding pressure, and the hydraulic oil present in the reservoir tank 26e has atmospheric pressure. The hydraulic oil in the first cylinder 26a, the hydraulic line 26c, and the second cylinder 26b is set to be in an oil-tight state in balance with the hydraulic oil in the reservoir tank 26e when the piston 23 is in the release position.

[0041] The axial movement of the nut 22b accompanying the rotation of the electric motor 21 of the screw mechanism 22 is transmitted to the first piston 24 via the connecting member 25. When the first piston 24 moves axially, the hydraulic oil in the first cylinder 26a flows into the second cylinder 26b via the hydraulic line 26c, and the second piston 23 strokes to the fastening (other axial) side.

[0042] In FIG. 1, the frictional fastening element 1 is shown in a released state in which hydraulic pressure has been discharged from the hydraulic chamber 27 and the second piston 23 has been moved to the side opposite the friction plate 13 by the biasing force of the return spring.

[0043] When the clutch 1 is engaged, in the released state shown in Fig. 1, the electric motor 21 of the operating actuator 2 is rotated to stroke the nut 22b toward the engagement side, and the first piston 24 moves axially in the first cylinder 26a to the other side as shown in Fig. 2. The axial movement of the first piston 24 causes the hydraulic oil in the first cylinder 26a to flow into the second cylinder 26b (hydraulic chamber 27) via the hydraulic line 26c, and the second piston 23 moves toward the friction plate 13 against the biasing force of the return spring.

[0044] The stroke of the nut 22b, more specifically, a first stroke L1 from a nut release position b1 on the screw shaft 22a corresponding to a predetermined release position a1 of the second piston 23 to a nut zero clearance position b2 on the screw shaft 22a corresponding to a zero clearance position a2 where the clearance between the friction plates 13 is closed by the second piston 23 and the second piston 23 is in a zero clearance state in which the second piston 23 is in contact with or almost in contact with the friction plates 13 without pressing the friction plates 13, supplies a holding hydraulic pressure P2 to the hydraulic chamber 27, which is lower than the fastening hydraulic pressure P1 corresponding to the pressing force required to fasten the friction fastening element 1, as shown in FIG. 4(a), to move the second piston 23 toward the friction plates 13 against the biasing force of the return spring, to end the stroke for fastening the second piston 23, and to hold the second piston 23 at the zero clearance position a2. In other words, the holding hydraulic pressure P2 is supplied to the hydraulic chamber 27 during the stroke of the second piston 24b from the release position a1 to the zero clearance position a2.

[0045] Furthermore, when the nut 22b is stroked toward the fastening side in the zero clearance state shown in Fig. 2, the first piston 24 moves further toward the other axial side in the first cylinder 26a as shown in Fig. 3. The axial movement of the first piston 24 causes the hydraulic oil in the first cylinder 26a to flow into the second cylinder 26b (hydraulic chamber 27) via the hydraulic line 26c, increasing the hydraulic pressure in the hydraulic chamber 27, causing the second piston 23 to press the friction plate 13, and the friction plate 13 is sandwiched between the retaining plate 15 fixed to the drum 11 and the second piston 23 and becomes unable to rotate relative to each other, thereby bringing about a fastening state in which the frictional fastening element 1 is fastened.

[0046] The stroke of the nut 22b, more specifically, the second stroke L2 from the nut zero clearance position b2 to the nut fastening position b3 on the screw shaft 22a corresponding to the fastening position a3 where the second piston 23 presses the friction plate 13 and the frictional fastening element 1 is in a fastened state, supplies hydraulic pressure to the hydraulic chamber 27 that is equal to or higher than the fastening hydraulic pressure P1 corresponding to the pressing force required to fasten the frictional fastening element 1, as shown in Figure 4(a).

[0047] On the other hand, when the frictional fastening element 1 is released, if the nut 22b is stroked toward the release side (from the nut fastening position b3 to the nut zero clearance position b2) in the fastened state shown in FIG. 3, the pressing force of the second piston 23 is released with the second piston 23 in contact or nearly in contact with the friction plate 13, as shown in FIG. 2, and the frictional fastening element 1 enters a zero clearance state.

[0048] Furthermore, when the nut 22b is stroked toward the release side (from the nut zero clearance position b2 to the nut release position b1) in the zero clearance state shown in FIG. 2, the second piston 23 moves toward the anti-friction plate 13 side due to the biasing force of the return spring, as shown in FIG. 1, and the frictional fastening element 1 enters the released state.

[0049] When the frictional fastening element 1 is engaged, it is desirable to increase the stroke speed of the piston 23 from the release position a1 to the zero clearance position a2 from the standpoint of responsiveness, and it is desirable to reduce the stroke speed from the zero clearance position a1 to the engaged position a3 while generating the pressing force necessary to fasten the friction plate 13 for precise controllability.

[0050] In order to achieve such requirements, it may be considered to use a high-output motor that is rated to output the maximum required rotational speed corresponding to the stroke speed required for the second piston 23 of the frictional fastening element 1 and the maximum required torque corresponding to the pressing force required for the piston 23; however, increasing the output of the motor will result in the motor becoming larger, which will make it difficult to mount the operating actuator 2.

[0051] In contrast, the actuator 2 of the friction plate 1 includes a screw mechanism 22 for achieving both improved responsiveness and securing of pressing force during fastening while miniaturizing the motor. As shown in FIG. 5, the screw mechanism 22 is configured by a pitch variable ball screw mechanism, and is disclosed, for example, in Japanese Patent No. 4366215. The screw mechanism 22 includes a first pitch region X1 in which a first pitch X11 is formed on one axial side of the screw shaft 22a, and a second pitch region X2 that is continuous with the first pitch region X1 and in which a second pitch X21 is formed on the other axial side. The second pitch X21 is formed to be smaller than the first pitch X11. In this embodiment, as disclosed in Japanese Patent No. 4366215, the nut 22b includes a ball holding member (not shown) having a rolling element transfer groove and a case (not shown) in which the ball holding member is rotatably accommodated, and is configured so that the ball holding member rotates relative to the case in response to a change in the pitch of the screw shaft.

[0052] The pitches X11 and X21 provided on the screw shaft 22a are the distance between adjacent screw grooves, and since the screw shaft 22a is configured with a single thread in this embodiment, one pitch corresponds to the distance that the nut 22b moves in the axial direction when the screw shaft 22a (electric motor 21) rotates once. The stroke amount of the nut when the electric motor 21 rotates once is larger in the first pitch region X1 than in the second pitch region X2. Therefore, the stroke speed of the nut 22b in the first pitch region X1 is set to be faster than the stroke speed of the nut 22b in the second pitch region X2.

[0053] As described above, the second piston 23 strokes according to the stroke of the nut 22b. The relationship between the first pitch region X1 and the second pitch region X2, in which the stroke speed of the nut 22b changes, and the stroke speed of the piston 23 will be described with reference to Fig. 2. For ease of explanation, it is assumed here that the stroke amount of the nut 22b and the stroke amount of the second piston 23 are the same.

[0054] The first pitch region X1 is set to be equal to a preset stroke amount L1 from the release position a1 to the zero clearance position a2 of the second piston 23. The second pitch region X2 extends to the other axial side continuously from the first pitch region X1, and is set to be equal to or greater than a preset stroke amount from the zero clearance position a2 to the fastened position a3.

[0055] The nut release position b1, which corresponds to the case where the second piston 23 is located at the predetermined release position a1, is set so that the tip position of the nut 22b is located at one axial end of the first pitch region X1. The nut zero clearance position b2, which corresponds to the case where the second piston 23 is located at the zero clearance position a2, is set so that the tip position of the nut 22b is located at the boundary position X between the first pitch region X1 and the second pitch region X2 (the other axial end of the first pitch region X1 and the one axial end of the second pitch region X2) as shown by the dashed line. In other words, the first pitch X11 and the second pitch X21 are switched at the zero clearance position a2 of the second piston 23.

[0056] A second pitch region X3 is provided on one axial side of the first pitch region X1 for correcting a zero clearance position during manufacturing of the friction plate, which will be described later. A third pitch X31 formed in the second pitch region X3 is set to have the same pitch width as the first pitch X11.

[0057] As is well known, the relationship of output of an electric motor = angular velocity x torque is satisfied. Therefore, if the output of an electric motor is kept constant, then when an attempt is made to increase the motor torque, the rotation speed decreases, and when an attempt is made to increase the rotation speed, the torque decreases.

[0058] Therefore, since the first pitch region X1 corresponds to the stroke region L1 from the release position a1 to the zero clearance position a2 of the second piston 23, the torque required for the electric motor 21 corresponding to the holding oil pressure P2 is lower than the fastening oil pressure P1, so that the nut 22b can be moved at a high rotational speed and a stroke speed faster than the second pitch region X2 without a decrease in the motor rotational speed.

[0059] On the other hand, since the second pitch region X2 corresponds to the stroke region L2 from the zero clearance position a2 to the fastening position a3 of the second piston 23, the torque required for the electric motor 21 requires a large torque corresponding to the fastening oil pressure P1, and as a result, the motor rotation speed decreases and the nut 22b can be moved at a stroke speed slower than that of the first pitch region X1.

[0060] Therefore, when fastening the frictional fastening element 1, if the nut 22b is stroked over the first pitch region X1, the second piston 23 will be in a zero clearance state, and if the nut 22b is further stroked over the second pitch region X2 in the zero clearance state, the friction plate 13 will be pressed at approximately the same time as the nut 22b strokes, and the frictional fastening element 1 will be fastened with good responsiveness.

[0061] An automatic transmission (not shown) having a plurality of frictional engagement elements 1 is provided with a control device 30 that controls each of the operating actuators 2 in each of the frictional engagement elements 1 to form a gear stage according to the driving state. As shown in Fig. 5, the control device 30 receives signals from a range sensor 31 that detects a range selected by the driver's operation, a vehicle speed sensor 32 that detects the vehicle speed of the vehicle, an accelerator opening sensor 33 that detects the amount of accelerator pedal operation (accelerator opening) by the driver, an engine speed sensor 34 that detects the engine speed, a motor speed sensor 35 that detects the speed of the electric motor 21 of the operating actuator 2, and a hydraulic sensor 36 provided above the oil filling chamber 26. The control device 30 is mainly constituted by a microcomputer.

[0062] Based on various input signals, the control device 30 controls the automatic transmission by outputting control signals to each operating actuator 2. In the gear shift control, a target gear position is determined based on, for example, the vehicle speed detected by a vehicle speed sensor 32, the accelerator opening detected by an accelerator opening sensor 33, and a predetermined gear shift map.

[0063] When a gear shift to a target gear stage is performed, the operating actuators 2 corresponding to the frictional engagement elements on the disengagement side and the engagement side, where a so-called changeover is performed, are controlled.

[0064] Due to manufacturing errors, etc., the actual zero clearance position of the multiple friction plates 13 may become an as-manufactured zero clearance position a21 that is shifted toward the engagement side from the zero clearance position (design zero clearance position) a2 of the second piston 23 that was preset at the time of design, or an as-manufactured zero clearance position a22 that is shifted toward the release side, as shown by the dashed line in Figure 5.

[0065] If the zero clearance position a1 is shifted toward the fastening side during manufacturing, the stroke of the second piston 23 from the release position a1 to the fastening may be insufficient, and complete fastening may not be achieved.

[0066] When the zero clearance position is shifted to the fastening side due to a manufacturing error, a shift also occurs between the boundary position X of the second piston 23, the first pitch region X1 and the second pitch region X2 of the screw shaft 22a, which are set to coincide with the design zero clearance position a2 of the second piston 23, and the manufacturing zero clearance position a21. In this case, even if the second piston 23 completes the stroke from the previously set release position a1 to the zero clearance position a2 (the nut 22b reaches the boundary position X between the first pitch region X1 and the second pitch region X2), the second piston 23 does not reach the manufacturing zero clearance position a21, and the stroke region of the nut 22b changes from the first pitch region X1 to the second pitch region X2 before the second piston 23 reaches the manufacturing zero clearance position a21. Therefore, the stroke speed of the second piston 23 decreases before reaching the manufacturing zero clearance position a21, and there is a risk of a delay in the response of the second piston 23.

[0067] If the zero clearance position a1 is shifted to the release side during manufacturing, the stroke of the second piston 23 from the release position a1 to the fastening may become excessive, which may cause a shock due to sudden fastening.

[0068] When the zero clearance position is shifted to the release side due to a manufacturing error, a deviation also occurs between the boundary position X of the second piston 23 and the zero clearance position a21 at the time of manufacture between the first pitch region X1 and the second pitch region X2 of the screw shaft 22a, which is set to coincide with the zero clearance position a2 at the time of design of the second piston 23. In this case, the second piston 23 reaches the zero clearance position a21 at the time of manufacture before the second piston 23 completes the stroke from the previously set release position a1 to the zero clearance position a2 (the nut 22b reaches the boundary position X between the first pitch region X1 and the second pitch region X2), and even if the second piston 23 reaches the zero clearance position a21 at the time of manufacture, the stroke region of the nut 22b remains in the first pitch region X1. Therefore, even when the zero clearance position a21 is reached at the time of manufacture, the stroke speed of the second piston 23 remains fast, so that the second piston 23 suddenly fastens the multiple friction plates 13, causing a shock and possibly making it impossible to perform precise fastening control such as slip control.

[0069] In response to this, the control device 30 is configured to control the electric motor 21 of the operating actuator 2 to correct the stroke amount of the piston 24c so that the second piston 23 is set to a zero clearance position (zero clearance position at the time of manufacture) a21 that corresponds to the manufacturing error of the friction plate 13.

[0070] The control device 30 includes a deviation amount calculation means for calculating deviation amounts G1, G2 of the multiple friction plates 13 based on the manufacturing zero clearance positions a21, a22 detected by a piston position detection means 36 that detects the manufacturing zero clearance positions a21, a22 of the second piston 23, and a stroke correction means for correcting the axial position of the nut release position b1 of the nut 22b when the second piston 23 is located at the predetermined release position a1, based on the deviation amounts G1, G2 calculated by the deviation amount calculation means, thereby correcting the stroke amount L1 from the predetermined release position a1 of the second piston 23 to the designed zero clearance position a2 at the time of design.

[0071] As shown in FIG. 1, the piston position detection means 36 is constituted by an oil pressure sensor 36 as a piston position detection means provided in the oil filling chamber 26, and the oil pressure sensor 36 detects the actual zero clearance positions (zero clearance positions at the time of manufacture) a21, a22 of the frictional fastening element 1 at the time of manufacture.

[0072] In this embodiment, the zero clearance positions a21, a22 at the time of manufacture are detected when the value of the oil pressure sensor 36 becomes equal to or greater than a predetermined threshold value P3, as shown in Fig. 4(a). The predetermined threshold value P3 is set, for example, to an oil pressure equal to or greater than a holding oil pressure P2 at which the second piston 23 holds the state in which the clearances between the multiple friction plates 13 are filled against the biasing force of the return spring.

[0073] The wear amount calculation means calculates deviation amounts G1, G2 from zero clearance positions a21, a22 at the time of manufacture and zero clearance position a2 at the time of design of the second piston 23. Since the stroke amount of the second piston 23 corresponds to the stroke amount of the nut 22b, in this embodiment, the deviation amounts G1, G2 of the second piston 23 are corrected by correcting the deviation amounts of the nut 22b from the boundary position X of the nut 22b corresponding to the zero clearance position a2 at the time of design of the second piston 23 to the point at which the value of the hydraulic sensor 36 becomes equal to or greater than a predetermined threshold value P3 as correction stroke amounts g1, g2.

[0074] The deviation amount calculation means calculates the motor rotation amount by integrating the motor rotation position detected by the motor rotation speed sensor 35, and calculates the correction stroke amounts g1, g2 by multiplying the calculated motor rotation amount by the second pitch X21.

[0075] The stroke correction means controls the electric motor 21 so as to position the nut release position b1 of the nut 22b on the release side by the corrected stroke amounts g1, g2 calculated by the wear amount calculation means. Since the third pitch area in which the first pitch X11 is formed is provided on the release side of the first pitch area X1, the stroke correction means positions the nut release position b1 at the corrected nut release position b21 by rotating the electric motor 21 by the motor rotation amount calculated from the motor rotation amount = corrected stroke amounts g1, g2 / first pitch X11. As a result, the stroke of the nut 22b from the boundary position X to the release position is extended, and therefore the stroke of the second piston 23 linked to the nut 22b from the release position a1 to the zero clearance position is also extended.

[0076] As shown by the virtual line in FIG. 4(b), if the zero clearance position is shifted toward the fastening side due to a manufacturing error, the nut 22b will stroke in the second pitch region X2 while the second piston 23 strokes from the design zero clearance position a2 to the manufacturing zero clearance position a21. However, in this embodiment, the stroke amount of the nut 22b is corrected so that the region in which the nut 22b strokes at the first pitch X11 is extended, so that the nut 22b can stroke at the stroke speed of the first pitch region X1 until the second piston 23 reaches the manufacturing zero clearance position a21.

[0077] The control device 30 controls the electric motor 21 so that the release position of the nut 22b when the second piston 23 is located at the release position a1 (the stroke amount of the piston and the stroke amount of the nut are made equal in this embodiment, so the release position of the nut 22b is set to a1) is located in the second pitch region X3 on one side of the end portion on one side in the axial direction of the first pitch region X1. The stroke correction amount of the nut 22b is calculated from the difference between the motor rotation speed from the release position a1 of the second piston 23 to the zero clearance position at the time of manufacture a21 and the rotation speed from the preset release position a1 to the zero clearance position at the time of design a2, and the second pitch X21. The rotation speed of the electric motor 21 is calculated from the calculated stroke correction amount of the nut 22b and the third pitch (=first pitch) P11, and the release position a1 of the nut 22b is corrected to the corrected release position a11.

[0078] As the release position of the nut 22b is corrected, the axial position of the first piston 24 connected to the nut 22b moves toward the release side, and the volume of the first cylinder 26a is expanded. The expansion of the volume of the first cylinder 26a generates negative pressure in the first cylinder 26a, and the check valve 26f is opened. Until the pressure of the first cylinder 26a coincides with the atmospheric pressure, hydraulic oil is supplied from the reservoir tank 26e to the first cylinder 26a via the connection part 26d, and the inside of the oil filling chamber 26 is maintained in an oil-tight state.

[0079] In this way, the control device 30 calculates the stroke correction amount of the release position of the nut 22b to correct the deviation of the zero clearance position, and by correcting the release position of the nut 22b, the zero clearance position of the second piston 23 is corrected.

[0080] As shown by the virtual line in FIG. 7, if the zero clearance position is shifted to the release side due to a manufacturing error, the second piston 23 will reach the as-manufactured zero clearance position a22 before completing the stroke from the release position a1 to the designed zero clearance position a2. As a result, the nut 22b will stroke through the first pitch region X1, and there is a risk that the second piston 23 will suddenly fasten the friction plate 13 at a stroke speed faster than that in the second pitch region X2. However, in this embodiment, the stroke amount of the nut 22b is corrected so that the region in which the nut 22b strokes at the first pitch X11 is shortened. Therefore, from the point in time when the second piston 23 reaches the as-manufactured zero clearance position a21, the nut 22b can be stroked at the stroke speed of the second pitch region X2.

[0081] The control device 30 controls the electric motor 21 so that the release position of the nut 22b when the second piston 23 is located at the release position a1 (in this embodiment, the stroke amount of the piston and the stroke amount of the nut are made to match, so the release position of the nut 22b is set to a1) is located on the other side of the end portion on one side of the axial direction of the first pitch region X1. The stroke correction amount of the nut 22b is calculated from the difference between the motor rotation speed from the release position a1 of the second piston 23 to the zero clearance position a21 at the time of manufacture and the rotation speed from the preset release position a1 to the zero clearance position a2 at the time of design, and the first pitch X11. The rotation speed of the electric motor 21 is calculated from the calculated stroke correction amount of the nut 22b and the first pitch X11, and the release position a1 of the nut 22b is corrected to the corrected release position a12.

[0082] As the release position of the nut 22b is corrected, the axial position of the first piston 24 connected to the nut 22b moves toward the fastening side, so the volume of the first cylinder 26a needs to be reduced. Since the reduction in the volume of the first cylinder 26a generates hydraulic pressure in the first cylinder 26a, the check valve 26f is opened to discharge hydraulic oil through the connection part 24d to the reservoir tank 26e side until the pressure of the first cylinder 26a coincides with the atmospheric pressure.

[0083] In this way, the control device 30 calculates the stroke correction amount of the release position of the nut 22b to correct the deviation of the zero clearance position, and by correcting the release position of the nut 22b, the zero clearance position of the second piston 23 is corrected.

[0084] In this manner, in the control device 30, the correction amount of the release position of the nut 22b for correcting the deviation of the zero clearance position is calculated, and the zero clearance position is corrected by correcting the release position of the nut 22b.

[0085] Fig. 8 is a flowchart for explaining the correction of the position of the second piston 23 when the frictional fastening element 1 is fastened. As shown in Fig. 8, the control device 30 calculates a stroke correction amount of the nut 22b corresponding to the deviation in the position of the second piston 23 due to the manufacturing error of the friction plate 13, and adjusts the release position of the nut 22b based on the calculated stroke correction amount of the nut 22b so that the position of the second piston 23 when fastening of the frictional fastening element 1 starts is a position where the zero clearance state is achieved.

[0086] First, the control device 30 reads the selected range and determines whether the read range is the P range or not (step S1).

[0087] If the determination in step S1 is NO, i.e., if the range is not the P range, the zero clearance correction control is terminated. If the determination in step S1 is YES, i.e., if the range is the P range, the stroke of the nut 22b is advanced (step S2) and it is determined whether the hydraulic sensor 36 is equal to or greater than a predetermined threshold value P3 (step S3).

[0088] If the determination result in step S3 is NO, that is, if the oil pressure is below the predetermined threshold value P3 and the second piston 23 has not reached the zero clearance position, steps S2 to S3 are repeated. However, if the determination result in step S3 is YES, that is, if the oil pressure is above the predetermined threshold value P3 and the second piston 23 has reached the as-manufactured zero clearance position a21, the difference (stroke correction amount) G1, G2 between the stroke amount from the release position a1 of the nut 22b to the as-manufactured zero clearance position a21 and the stroke amount from the release position a1 at the time of design to the as-designed zero clearance position a2 is calculated (step S4).

[0089] In the next step S5, the release position a1 of the nut 22b is corrected to the release side. At this time, the axial position of the nut 22b is corrected so that it is located on the release side or fastening side from the preset release position a1 by the stroke correction amount calculated in step S4.

[0090] In step S6, the check valve 24h provided between the first cylinder 26a and the reservoir tank 24g is opened to fill or discharge hydraulic oil into or from the first cylinder 26a, whose volume has expanded or contracted, and in the following step S7, step S6 is repeated until the first cylinder 26a is balanced with the atmospheric pressure (or the reservoir tank 26e), at which point the check valve 26f is closed and the zero clearance correction control is terminated.

[0091] In this way, the actuator 2 for the frictional engagement element 1 uses a variable pitch ball screw mechanism 22 having different pitches, the first pitch X11 and the second pitch X21, and thereby it is possible to increase the stroke speed from the release position a1 to the zero clearance position a2 and reduce the stroke speed from the zero clearance position a2 to the engagement position a3, without increasing the size of the motor, and to obtain the pushing force required for engagement of the frictional engagement element 1. As a result, it is possible to achieve both improved response speed when the frictional engagement element is engaged and precise engagement control.

[0092] For example, by setting the first pitch X11 to the maximum stroke speed at the time of fastening and the second pitch X21 to the maximum required torque at the time of fastening, a smaller motor can be used compared to the case where a large motor capable of outputting the maximum rated rotation speed and maximum required torque is installed.

[0093] Since a ball screw mechanism 22 and an oil-tight hydraulic circuit 24 are adopted as the operating actuator 2, there is no need to drive a hydraulic pump to maintain hydraulic pressure in the non-engaged state, as is the case when a hydraulic control device such as an oil pump and multiple solenoid valves is used as the operating actuator 2, and the drive loss due to maintaining pressure in the non-engaged state can be reduced.

[0094] The contact area can be reduced compared to when a sliding screw mechanism is used in the screw mechanism, and the screw efficiency is improved, which reduces the motor torque and allows the motor to be made smaller.

[0095] By correcting the axial position of the nut 22b at the released position, it is possible to correct the deviation between the boundary position of the first pitch region X1 and the second pitch region X2 and the zero clearance positions a21, a22 at the time of manufacture due to manufacturing errors of the multiple friction plates 13. Therefore, even if manufacturing errors occur in the multiple friction plates 13, it is possible to achieve both responsiveness during fastening and precise controllability.

[0096] Specifically, for example, if the manufacturing error of the multiple friction plates 13 causes the manufacturing zero clearance position a21 to shift toward the fastening side from the design zero clearance position (boundary position) a2, the deviation between the manufacturing zero clearance position a21 and the boundary position a2 can be corrected by correcting the axial position of the nut 22b in the released state to one axial side (release side) by the amount of stroke that needs to be extended between the release position a1 and the design zero clearance position a2.

[0097] On the other hand, if the zero clearance position a22 at the time of manufacture deviates from the boundary position a2 toward the release side due to manufacturing errors in the multiple friction plates 13, the deviation between the zero clearance position a22 at the time of manufacture and the boundary position a2 can be corrected by correcting the axial position of the nut 22b in the released state toward the other axial side (fastened side) by the amount of stroke that needs to be shortened between the release position a1 and the design zero clearance position a2.

[0098] Since the zero clearance positions a21, a22 of the second piston 23 at the time of manufacture are detected by the rise of hydraulic pressure, even if a manufacturing error in the friction plate 13 causes a deviation between the zero clearance positions a21, a22 at the time of manufacture and the zero clearance position a2 at the time of design, the zero clearance positions a21, a22 at the time of manufacture can be accurately detected.

[0099] Since the zero clearance position of the second piston 23 is detected by the hydraulic pressure sensor 36 based on the rise in hydraulic pressure caused by the engagement of the friction plates, more precise controllability can be obtained compared to the case where a hydraulic pressure switch is used.

[0100] In this embodiment, the screw shaft has the first pitch X11 and the second pitch X21, but the pitch provided on the screw shaft 22a may be composed of three or more kinds of pitches. For example, a transition region having a transition pitch formed at a pitch smaller than the first pitch X11 and larger than the second pitch X21 may be formed at a transition portion connecting the first pitch region X1 and the second pitch region X2. In the transition region, the pitch may be set to gradually decrease from the first pitch region X1 to the second pitch region X2.

[0101] In this embodiment, a configuration has been described in which the oil filling chamber 26 includes a first cylinder 26a, a second cylinder 26b, and a hydraulic line 26c that fluidly connects the first cylinder 26a and the second cylinder 26b, but the oil filling chamber 26 may also be configured to include either the first cylinder 26a or the second cylinder 26b.

[0102] In the present embodiment, the electric motor 21 of the operation actuator 2 is configured as a brushless motor, but this is not limited thereto, and other motors such as a stepping motor may be used.

[0103] In this embodiment, an example is shown in which the frictional fastening element 1 is a clutch, but basically, a similar operating actuator 2 may also be provided for a brake in which the drum 11 connects a non-rotating element constituted by a transmission case or the like and a hub 12 as a rotating member.

[0104] In this embodiment, an example in which the piston position detection means is configured as a hydraulic sensor has been described, but the present invention is not limited to this, and the piston position detection means may be configured as a hydraulic switch. This makes it possible to detect the zero clearance position with a cheaper configuration than when a hydraulic sensor or the like is used.

[0105] In this embodiment, an example has been described in which the piston position detection means is configured as a hydraulic sensor, but this is not limited to this, and the piston position detection means may be configured as a torque sensor that detects the rise of torque.

[0106] The present invention is not limited to the exemplified embodiments, and various improvements and design modifications are possible without departing from the gist of the present invention. [Industrial Applicability]

[0107] As described above, according to the present invention, in an actuator for operating a frictional fastening element, it is possible to achieve both improved responsiveness during fastening and a sufficient pressing force while reducing the size of the motor, and therefore the present invention may be suitably used in the industrial field of manufacturing frictional fastening elements. [Explanation of symbols]

[0108] 1. Frictional fastening elements 2. Actuator 11. Drums 12. Hub 13 Multiple friction plates 21 Motor 22 Screw mechanism (ball screw mechanism, variable pitch ball screw mechanism) 22a Screw shaft 22b Nut 23 First piston (piston) 26 Oil filling room 36 Piston position detection means (hydraulic sensor, hydraulic switch) 30 Control device (deviation amount calculation means, stroke correction means) a21 Zero clearance position G1, G2 deviation amount X border position X1 First pitch area X2 Second pitch area X11 1st pitch X21 2nd pitch

Claims

1. An actuator for operating a friction fastening element, which is provided between a drum and a hub and presses a plurality of friction plates alternately engaged with the drum and the hub to fasten them together, a motor, a screw mechanism that converts a rotational force of the motor into linear motion, a piston that presses the friction plate, and an oil-filled chamber in an oil-tight state that is filled with hydraulic oil that transmits the linear motion of the screw mechanism to the piston, The screw mechanism is composed of a ball screw mechanism having a screw shaft and a nut that moves axially on the screw shaft and transmits a pressing force to the piston via the oil filling chamber, and the screw shaft is provided with a first pitch region in which a first pitch is formed on one side in the axial direction, and a second pitch region in which a second pitch is formed on the other side in the axial direction, continuous with the first pitch region, and is formed so that the second pitch is smaller than the first pitch, an actuator for operating a frictional fastening element, the first pitch region being provided at a position corresponding to a zero clearance position where the piston moves from a released position of the piston to a zero clearance state where the piston closes the clearance of the friction plate, and the second pitch region being provided at a position corresponding to a change from the zero clearance position to a fastened position.

2. a piston position detection means for detecting a zero clearance position of the piston at the time of manufacture; a deviation amount calculation means for calculating a deviation amount between the zero clearance position at the time of manufacture detected by the piston position detection means and a boundary position between the first pitch region and the second pitch region; and a stroke correction means for correcting an axial position of the nut when the piston is located at a predetermined release position, based on the deviation calculated by the deviation calculation means, thereby correcting an amount of stroke of the piston from the predetermined release position to the clearance position.

3. 3. An actuator for operating a frictional fastening element according to claim 2, wherein the piston position detection means is configured to detect the position of the piston at a rise in hydraulic pressure in the oil filling chamber.

4. 4. The actuator for operating a frictional fastening element according to claim 3, wherein the piston position detection means is constituted by a hydraulic switch.

5. 4. The actuator for operating a frictional fastening element according to claim 3, wherein the piston position detection means is constituted by a hydraulic sensor.

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