Flywheel device

Abstract

This flywheel device includes: a first wheel comprising a ring gear on an outer peripheral part; and a second wheel comprising a second friction surface facing a first friction surface of the first wheel. The flywheel device has a starter motor that comprises a helical pinion that meshes with the ring gear, and starts and rotates the first wheel. The first wheel is movable between a fastening position at which the first friction surface and the second friction surface are in contact with each other, and a release position at which the first friction surface and the second friction surface are separated from each other. When starting an engine for rotationally driving the helical pinion, the first wheel is moved to the fastening position.

Description

Flywheel Device

[0001] The present disclosure relates to a flywheel device.

[0002] A flywheel device consisting of two wheels is attached to the crankshaft of the engine. This flywheel device has a first wheel fixed to the crankshaft and a second wheel connected to the first wheel via a spring (see Patent Documents 1 and 2).

[0003] JP 2006-9939 A JP 2005-140312 A

[0004] When starting an engine using a starter motor, a first wheel fixed to the crankshaft is rotated to start the engine. However, because the second wheel is connected to the first wheel via a spring, there is a risk that the first and second wheels may resonate when the engine is started. This resonance phenomenon reduces quietness, so there is a need to suppress this resonance phenomenon when the engine is started.

[0005] According to the present disclosure, a flywheel device includes a first wheel axially movably connected to a crankshaft and including a ring gear on its outer periphery. The flywheel device includes a second wheel rotatably connected to the first wheel via a spring and including a second friction surface opposing a first friction surface of the first wheel. The flywheel device includes a helical pinion that meshes with the ring gear and a starter motor that starts and rotates the first wheel. The first wheel is movable between an engaged position where the first friction surface and the second friction surface are in contact with each other and a disengaged position where the first friction surface and the second friction surface are separated. When the engine is started to rotate the helical pinion, the first wheel is moved to the engaged position.

[0006] According to the present disclosure, it is possible to suppress the resonance phenomenon when starting the engine.

[0007] FIG. 1 is a diagram showing an example of a vehicle equipped with a power unit. FIG. 2 is a diagram showing the structure of a connection portion between an engine and a transmission. FIG. 3 is a cross-sectional view of a wheel assembly taken along line A-A in FIG. 2. FIG. 4A is a diagram showing the operating state of the wheel assembly during driving. FIG. 4B is a diagram showing the operating state of the wheel assembly during coasting. FIG. 5 is a diagram showing a flywheel device according to an embodiment of the present disclosure. FIG. 6 is a diagram showing the operating state of the flywheel device during engine start. FIG. 7A is a diagram showing an example of transition in wheel rotation speed during engine start as an example. FIG. 7B is a diagram showing an example of transition in wheel rotation speed during engine start as a comparative example.

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the following description, identical or substantially identical configurations and elements are designated by the same reference numerals and will not be described repeatedly.

[0009] <Power Unit> Fig. 1 is a diagram showing an example of a vehicle 11 equipped with a power unit 10. The illustrated power unit 10 is provided with a flywheel device 12 which is an embodiment of the present disclosure. As shown in Fig. 1, the vehicle 11 has the power unit 10 which is made up of an engine 13 and a transmission 14. An output shaft 15 of the power unit 10 is connected to rear tires 18 via a propeller shaft 16 and a differential mechanism 17. The illustrated power unit 10 is a rear-wheel drive power unit, but is not limited to this and may be a front-wheel drive or all-wheel drive power unit.

[0010] FIG. 2 is a diagram showing the structure of the connection portion between the engine 13 and the transmission 14. As shown in FIG. 2, the transmission 14 has a speed change mechanism 20 consisting of a speed change gear train, a synchronizer, and the like (not shown). A wheel assembly 21 and an input clutch 22 are provided between the engine 13 and the speed change mechanism 20. Engine torque output from a crankshaft 23 of the engine 13 is transmitted from the wheel assembly 21 via the input clutch 22 to the speed change mechanism 20. The wheel assembly 21 has a function of attenuating fluctuations in the engine torque transmitted to the speed change mechanism 20. The input clutch 22 is switchable between an engaged state, which connects the wheel assembly 21 and the speed change mechanism 20, and a disengaged state, which disconnects the wheel assembly 21 and the speed change mechanism 20.

[0011] 2, the wheel assembly 21 has a first wheel 30 connected to the crankshaft 23 of the engine 13, and a second wheel 40 connected to the input shaft 24 of the transmission mechanism 20 via the input clutch 22. The wheel assembly 21 thus equipped with the two wheels 30, 40 is called a dual mass flywheel.

[0012] The first wheel 30 includes a disc 31 movably attached to the crankshaft 23 in the axial direction and an annular cover 33 attached to the disc 31 to define a damper chamber 32 therein. A hub 34 with spline teeth 34a is fixed to the crankshaft 23, and the disc 31 meshes with the spline teeth 34a of the hub 34. In other words, the disc 31 constituting the first wheel 30 is movably attached to the crankshaft 23 via the hub 34 in the axial direction. The second wheel 40 includes a hollow shaft 42 rotatably supported on the hub 34 via a bearing 41, a disc 43 attached to the hollow shaft 42 and housed in the damper chamber 32, and a fastening plate 44 attached to the end of the hollow shaft 42. The disc 31 of the first wheel 30 includes a pair of protrusions 35a, 35b disposed within the damper chamber 32. Similarly, the disc 43 of the second wheel 40 includes a pair of protrusions 45a, 45b disposed within the damper chamber 32.

[0013] FIG. 3 is a cross-sectional view of the wheel assembly 21 taken along line A-A in FIG. 2. As shown in FIG. 3, a pair of spring units (springs) 50 and 60 are housed in the damper chamber 32 of the wheel assembly 21. Each spring unit 50 and 60 is composed of three damper springs 70, 71, and 72 and four spring seats 73, 74, 75, and 76. Furthermore, end 51 of spring unit 50 faces protrusion 35b and protruding piece 45b, while end 52 of spring unit 50 faces protrusion 35a and protruding piece 45a. Similarly, end 61 of spring unit 60 faces protrusion 35a and protruding piece 45a, while end 62 of spring unit 60 faces protrusion 35b and protruding piece 45b. The spring constant of damper spring 70 is greater than the spring constants of damper springs 71 and 72.

[0014] 4A is a diagram showing the operating state of the wheel assembly 21 during driving, and FIG. 4B is a diagram showing the operating state of the wheel assembly 21 during coasting. In order to clarify the relative positions of the first wheel 30 and the second wheel 40, in FIGS. 3, 4A, and 4B, a mark P1 is shown on the first wheel 30 and a mark P2 is shown on the second wheel 40.

[0015] When driving, in which torque is transmitted from the engine 13 to the transmission mechanism 20, torque is transmitted from the first wheel 30 to the second wheel 40 via the compressed spring units 50, 60. At this time, as shown by arrow α1 in Fig. 4A, the relative rotational position of the first wheel 30 is advanced by a predetermined angle with respect to the second wheel 40. On the other hand, when coasting, in which torque is transmitted from the transmission mechanism 20 to the engine 13, torque is transmitted from the second wheel 40 to the first wheel 30 via the compressed spring units 50, 60. At this time, as shown by arrow β1 in Fig. 5, the relative rotational position of the first wheel 30 is delayed by a predetermined angle with respect to the second wheel 40.

[0016] In this way, the wheels 30, 40 that make up the wheel assembly 21 are connected to each other via the spring units 50, 60 so as to be capable of relative rotation. This allows the wheel assembly 21 to apply a rotational phase difference to the wheels 30, 40 while compressing the spring units 50, 60, thereby attenuating fluctuations in engine torque transmitted to the transmission mechanism 20. The first wheel 30 and the second wheel 40 are allowed to rotate relative to each other within a predetermined angular range.

[0017] <Input Clutch> The input clutch 22 has a clutch cover 80 attached to the fastening plate 44 of the wheel assembly 21, and a clutch disc 81 attached to the input shaft 24 of the transmission mechanism 20. A diaphragm spring 82 and a pressure plate 83 are provided inside the clutch cover 80. A release bearing 85 is attached to the transmission case 84 so as to be movable in the axial direction, and the release bearing 85 is disposed opposite the center of the diaphragm spring 82. A release fork 86 is tiltably attached to the transmission case 84, and a release cylinder 87 that actuates the release fork 86 is also attached.

[0018] When the driver depresses the clutch pedal (not shown), the release cylinder 87 moves the release bearing 85 via the release fork 86, and the release bearing 85 is pressed into the center of the diaphragm spring 82. This releases the diaphragm spring 82 from pressing down on the pressure plate 83, releasing the pressure plate 83 and the fastening plate 44 from binding the clutch disc 81, and the input clutch 22 is switched to a released state. On the other hand, when the driver releases the clutch pedal, the diaphragm spring 82 pushes back the release bearing 85, and the diaphragm spring 82 presses down on the pressure plate 83. This causes the pressure plate 83 and the fastening plate 44 to bind the clutch disc 81, and the input clutch 22 is switched to an engaged state.

[0019] <Flywheel Device> Next, a description will be given of the structure of the flywheel device 12. Fig. 5 is a diagram showing the flywheel device 12 according to one embodiment of the present disclosure. The flywheel device 12 shown in the figure is made up of a wheel assembly 21 and a starter motor 92.

[0020] 5, a ring gear 90 is attached to the outer circumferential portion 30a of the first wheel 30. A starter motor 92 having a helical pinion 91 that meshes with the ring gear 90 is attached to the transmission case 84. The helical pinion 91 of the starter motor 92 is movable between a protruding position where it meshes with the ring gear 90 and a retracted position where it is separated from the ring gear 90. The ring gear 90 and the helical pinion 91 are helical gears that have helical tooth traces.

[0021] The annular cover 33 of the first wheel 30 is formed with a first friction surface 36 equipped with a facing (friction material) 93. The fastening plate 44 of the second wheel 40 is formed with a second friction surface 46 opposing the first friction surface 36. As described above, the first wheel 30 is attached to the crankshaft 23 so as to be movable in the axial direction. The first wheel 30 is movable between a fastened position where it approaches the fastening plate 44 and a released position where it moves away from the fastening plate 44. That is, the first wheel 30 is movable between a fastened position where the first friction surface 36 and the second friction surface 46 are in contact with each other and a released position where the first friction surface 36 and the second friction surface 46 are separated from each other. The facing 93 is made of a base material such as glass fiber or metal fiber, and a binder such as a thermosetting resin.

[0022] A return spring 94 made of a disc spring is disposed between the first friction surface 36 of the first wheel 30 and the second friction surface 46 of the second wheel 40. The return spring 94 biases the first wheel 30 toward the released position. Furthermore, the facing 93 is positioned outward of the return spring 94 in the radial direction D1 of the first wheel 30. By disposing the facing 93 radially outward of the return spring 94 in this way, the area of ​​the facing 93 can be increased while avoiding an increase in the size of the wheel assembly 21.

[0023] <Starting the Engine> The operating state of the flywheel device 12 when starting the engine will now be described. Figure 6 is a diagram showing the operating state of the flywheel device 12 when starting the engine.

[0024] As shown in Figure 6, when starting the engine 13 using the starter motor 92, the helical pinion 91 of the starter motor 92 is moved to the protruding position and driven to rotate. This allows the starter motor 92 to rotate the first wheel 30, which in turn starts and rotates the crankshaft 23 connected to the first wheel 30. However, because the wheel assembly 21 has the wheels 30, 40 that are rotatable relative to each other, there is a risk that noise will be generated as the wheels 30, 40 rotate relative to each other. In other words, there is a risk that abnormal noise will be generated due to component contact or the like caused by resonance between the wheels 30, 40, which will reduce quietness during engine start-up.

[0025] Therefore, the first wheel 30 is axially movably connected to the crankshaft 23, and the helical pinion 91 is used to rotate the first wheel 30 during engine start-up. As a result, a meshing reaction force with the helical pinion 91 can be applied to the ring gear 90 during engine start-up, causing the ring gear 90 and the first wheel 30 to move in the direction of arrow X1. That is, during engine start-up, the axial component of the meshing reaction force transmitted to the first wheel 30 can move the first wheel 30 to the fastened position, causing the first friction surface 36 to contact the second friction surface 46. This allows the first wheel 30 and the second wheel 40 to rotate integrally, suppressing resonance between the wheels 30 and 40 and improving quietness during engine start-up. It goes without saying that as the first wheel 30 moves toward the fastened position, the helical pinion 91 also moves in the direction of arrow X1 together with the ring gear 90.

[0026] Here, Fig. 7A is a diagram showing an example of the change in rotation speed of the wheels 30, 40 when the engine is started, as an example. Fig. 7B is a diagram showing an example of the change in rotation speed of the wheels 30, 40 when the engine is started, as a comparative example. Fig. 7A shows the change in rotation speed when both wheels 30, 40 are rotated together, as an example, and Fig. 7B shows the change in rotation speed when both wheels 30, 40 are rotated separately, as a comparative example. In Figs. 7A and 7B, the rotation speed of the first wheel 30 is indicated by "N1," and the rotation speed of the second wheel 40 is indicated by "N2."

[0027] As shown in FIG. 7A , when the helical pinion 91 begins to rotate at time t1, the meshing reaction force between the helical pinion 91 and the ring gear 90 causes the first wheel 30 to start moving toward the fastened position. At time t2, the first wheel 30 moves to the fastened position, bringing the first friction surface 36 and the second friction surface 46 into contact with each other, and the first wheel 30 and the second wheel 40 begin to rotate together. In other words, from time t2 onward, the rotation speeds N1 and N2 of the two wheels 30 and 40 can be matched, suppressing resonance between the wheels 30 and 40 and improving quietness during engine start-up. In contrast, if the first wheel 30 were designed to not move axially, the two wheels 30 and 40 would resonate, causing a large difference between the rotation speeds N1 and N2, as shown in FIG. 7B . As a result, the relative rotation angle of the wheels 30, 40, i.e., the torsional angle of the wheel assembly 21, reaches an upper limit, causing abnormal noise due to parts coming into contact, etc., and reducing quietness during engine start-up.

[0028] When engine start is complete, the driving force of the helical pinion 91 decreases, and the meshing reaction force between the helical pinion 91 and the ring gear 90 decreases, causing the first wheel 30 to move to the release position due to the spring force of the return spring 94. In this way, relative rotation between the first wheel 30 and the second wheel 40 is permitted after engine start, so fluctuations in engine torque transmitted to the transmission mechanism 20 via the wheel assembly 21 can be attenuated. Furthermore, when engine start is complete, the helical pinion 91 moves from the extended position to the retracted position.

[0029] <Modifications> The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. In the above description, the helical pinion 91 of the starter motor 92 is moved from the retracted position to the extended position when the engine is started, but this is not limiting. For example, a constantly meshing starter motor in which the helical pinion 91 is always meshed with the ring gear 90 may be used.

[0030] In the illustrated example, the return spring 94 is disposed between the first friction surface 36 and the second friction surface 46, but this is not limiting and the return spring 94 may be disposed at another location between the first wheel 30 and the second wheel 40. Also, in the above description, a disc spring is used as the return spring 94, but this is not limiting and a return spring formed of a coil spring or the like may be used.

[0031] In the illustrated example, the facing 93 is provided only on the first friction surface 36, but this is not limiting. For example, the facing 93 may be provided only on the second friction surface 46, or the facing 93 may be provided on both the first friction surface 36 and the second friction surface 46. Furthermore, if it is possible to ensure the frictional force of the friction surfaces 36, 46 and prevent the friction surfaces 36, 46 from seizing or the like, the facing 93 may be omitted from both friction surfaces 36, 46.

[0032] In the illustrated example, each spring unit 50, 60 is configured with three damper springs 70, 71, 72, but this is not limiting. For example, each spring unit 50, 60 may be configured with one damper spring, or each spring unit 50, 60 may be configured with two or more damper springs.

[0033] The illustrated input clutch 22 and transmission mechanism 20 are manual input clutch 22 and transmission mechanism 20 operated by a driver, but are not limited to this. For example, they may be automatic input clutch and transmission mechanism that are automatically controlled by an electronic control unit.

[0034] 12...flywheel device, 13...engine, 23...crankshaft, 30...first wheel, 30a...outer periphery, 36...first friction surface, 40...second wheel, 46...second friction surface, 50, 60...spring unit (spring), 90...ring gear, 91...helical pinion, 92...starter motor, 93...facing (friction material), 94...return spring

Claims

1. A flywheel device connected to an engine crankshaft, comprising: a first wheel connected to the crankshaft so as to be axially movably, and having a ring gear on its outer periphery; a second wheel connected to the first wheel via a spring so as to be rotatable relative to the first wheel, and having a second friction surface opposing a first friction surface of the first wheel; and a starter motor having a helical pinion that meshes with the ring gear, and which starts and rotates the first wheel, wherein the first wheel is movable between a fastened position where the first friction surface and the second friction surface are in contact, and a released position where the first friction surface and the second friction surface are separated, and wherein the first wheel is moved to the fastened position when the engine is started to rotate the helical pinion.

2. A flywheel device according to claim 1, wherein the first wheel is moved to the fastened position by a meshing reaction force between the helical pinion and the ring gear.

3. A flywheel device according to claim 1, wherein at least one of the first friction surface and the second friction surface is provided with a friction material.

4. A flywheel device according to claim 1, wherein a return spring is provided between said first wheel and said second wheel to urge said first wheel toward said release position.

5. A flywheel device according to claim 1, wherein at least one of the first friction surface and the second friction surface is provided with a friction material, a return spring is provided between the first friction surface and the second friction surface for urging the first wheel towards the released position, and the friction material is located radially outward of the first wheel relative to the return spring.

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