Sensor wheel for a motor

Abstract

Engine (1) comprising a crankshaft (10) positioned in a cylinder block (3) of the engine (1), wherein the crankshaft (10) at one end has a flywheel flange (12) for attaching a flywheel (8) and a number of counterweights for providing dynamic balancing of the crankshaft (10) in use, comprising an end counterweight (11) positioned very close to an end wall (3e) of the cylinder block (3), wherein the end counterweight (11) has a recess (11r) formed therein in which a sensor wheel (20) is mounted, wherein the sensor wheel (20) is stamped from a single piece of steel and a middle circular section (21) and comprising a folded-over cylindrical rim section (24), wherein the folded-over cylindrical rim section (24) is arranged around an outer circumference of the middle circular section (21), extends away from one end wall (3e) of the cylinder block (3), has an inner radius that is large enough to allow the cylindrical rim section (24) to fit over the end counterweight (11) when the encoder wheel (20) is mounted on the crankshaft (10), and having several circumferentially spaced encoder gear teeth (26), wherein there are a number of circumferentially spaced openings (25) in the folded cylindrical rim section (24) and each of the encoder gear teeth (26) is formed by a web between two adjacent openings (25) in the folded cylindrical rim section (24), which thus forms a cage-like structure, and wherein the central circular section (21) a central opening (22) with a diameter large enough to allow the encoder wheel (20) to be mounted past the flywheel flange (12), and a number of compensating openings (23) formed therein to move a center of mass of the encoder wheel (20) away from an axis of rotation of the encoder wheel (20), wherein the compensating openings (23) of the central circular section (21) of the encoder wheel (20) are arranged at an angle and the encoder wheel (20) has an unbalance mass which, in conjunction with the arrangement of the compensating openings (23), compensates for an unbalance effect of the material lost from the end counterweight (11) due to the recess (11r).

Description

[0001] The present invention relates to a reciprocating piston engine having a crankshaft, and more particularly to a trigger wheel for such an engine for providing an indication of the rotational position of the engine's crankshaft.

[0002] The attachment of a disc-shaped sensor wheel with a number of peripheral teeth to an engine crankshaft is well known. Such a sensor wheel must be sufficiently wide to generate a reliable signal.

[0003] Traditionally, a sensor is mounted very close to the timing gear to detect the passage of each tooth, which is used by an associated engine management system to provide an indication of the rotational position of the crankshaft.

[0004] Typically, such a sensor wheel is mounted on the crankshaft at a location outside the engine's cylinder block. Such an arrangement has the disadvantage of increasing the overall size of the engine, which is problematic in many current vehicles.

[0005] There is an increasing demand for the production of smaller engines, especially for urban vehicles and hybrid vehicles where the available installation space for the engine is limited.

[0006] Furthermore, a front-mounted engine presents a hard spot in the event of a head-on collision, and thus it is desirable to keep the engine as small as possible. Therefore, any arrangement that minimizes the size, and especially the length, of an engine is advantageous.

[0007] It is an object of the invention to provide an improved sensor wheel for an engine.

[0008] According to a first aspect of the invention, there is provided a pickup wheel for an engine, stamped from a single piece of steel and comprising a central circular portion and a cylindrical rim portion disposed around an outer periphery of the central circular portion, the cylindrical rim portion having a plurality of circumferentially spaced pickup wheel teeth, the central circular portion having at least one opening formed therein for moving a center of mass of the pickup wheel away from a rotational axis of the pickup wheel, there being a number of circumferentially spaced openings in the cylindrical rim portion, and each of the pickup wheel teeth being formed by a web between two adjacent openings.

[0009] Each encoder wheel tooth may extend substantially parallel to an axis about which the encoder wheel rotates in use.

[0010] The central circular portion may define a number of circumferentially spaced locating holes used to attach the sensor wheel to a crankshaft of an engine.

[0011] According to a second aspect of the invention, there is provided an engine having a crankshaft positioned in a cylinder block of the engine, the crankshaft having a number of counterweights for providing dynamic balancing of the crankshaft in use, comprising an end counterweight positioned very close to an end wall of the cylinder block, the end counterweight having a recess formed therein in which a pickup wheel for an engine constructed according to the first aspect of the invention is mounted, the pickup wheel being arranged at an angle and having an unbalance mass sufficient to counterbalance the unbalance effect of material lost from the end counterweight due to the recess, the cylindrical skirt portion of the pickup wheel extending away from the one end wall of the cylinder block.

[0012] The encoder wheel may have a number of circumferentially spaced compensating holes, and the sizing, spacing, and positioning of the compensating holes in the encoder wheel may be designed to compensate for the material lost due to the recess from the end counterweight.

[0013] The depth of the recess in the end counterweight may substantially correspond to the thickness of the central circular portion of the encoder wheel.

[0014] The invention will now be described by way of example with reference to the accompanying drawings in which: Fig. Figure 1 is a schematic side view of a three-cylinder engine constructed according to the invention; Fig. Figure 2a is a partial cross-sectional view of an end portion of an engine showing the arrangement of crankshaft counterweights relative to an end wall of a cylinder block of the engine; Fig. 2b a section of a view of the Fig. 2a, showing how the attachment of a conventional disc-shaped sender wheel to the counterweight creates a conflict condition with the end wall of the cylinder block; Fig. Figure 3a is an end view of a sensor wheel according to a first aspect of the invention; Fig. 3b a side view of the Fig. 3a shown encoder wheel; Fig. 4 a pictorial representation of the Fig. 3a and Fig. 3b shown encoder wheel; Fig. 5 an inverted pictorial view of the Fig. 4, showing the sensor wheel attached to one end of a crankshaft of the engine and the positioning of an associated sensor; Fig. Figure 6 is a fragmentary section through one end of the crankshaft and one end wall of the engine, showing the positioning of the sender wheel on the crankshaft; Fig. 7 a view in the direction of arrow ‘F’ in Fig. 6, which shows the sender wheel in position on the crankshaft; Fig. 8 is a partial cross-sectional view in the direction of arrow ‘R’ in Fig. 6, which shows the sender wheel on the crankshaft; and Fig. Figure 9 is a transparent pictorial view of one end of the cylinder block of the engine showing the positioning of the sender wheel and associated sensor.

[0015] With reference to Fig. 1 shows a three-cylinder engine 1 having a cylinder head 2, a cylinder block 3 and an oil pan 4. The cylinder block 3 rotatably supports a crankshaft 10 having at one end a flywheel flange 12 for attaching a flywheel (in Fig. 1 not shown) is used on the crankshaft 10. The overall length 'L' of the cylinder block 3 is kept as short as possible to improve the packaging of the engine 1 in a motor vehicle.

[0016] With reference to Fig. 2a shows, on a larger scale, an end portion of the cylinder block 3 in the area of ​​the flywheel flange 12, wherein a flywheel 8 attached to the flywheel flange 12 is shown in dashed outline.

[0017] The cylinder block 3 has a number of inner walls 3w and is defined at each end by an end wall 3e. The walls 3w, 3e of the cylinder block 3 are arranged to support a number of bearings 15, which are used, via main bearing journals 13, 13e, to support the crankshaft 10 of the engine 1 for rotation about a longitudinal axis of the crankshaft 10.

[0018] The crankshaft 10 further comprises three connecting rod bearing journals 14, of which only one is in Fig. 2a is shown.

[0019] As is well known in the art, the crankshaft 10 comprises a number of counterweights, of which only one final counterweight 11 is in Fig. 2a is shown.

[0020] It is understood that the end wall 3e is positioned as close as possible to the counterweight 11 in order to minimize the overall length 'L' of the cylinder block 3.

[0021] In such an arrangement, a sensor wheel is usually attached to a part of the crankshaft 10 that is not located in the cylinder block 3, which results in an increase in the length of the engine 1, since the sensor wheel and its associated sensor are then positioned outside the cylinder block 3.

[0022] Fig. 2b is a view that is consistent with that of Fig. 2a is identical, except that it shows the attachment of a conventional disc-shaped sensor wheel 'T' to an outer side of the counterweight 11. As clearly shown in Fig. 2b, this leads to a conflict condition with respect to the end wall 3e of the cylinder block 3, which can only be overcome if the end wall 3e is in the direction of the arrow 'H' in Fig. 2b is moved away. Moving the end wall 3e in this way results in an increase in the overall length of the cylinder block 3.

[0023] Now, with reference to Fig. 3-9 shows a sensor wheel 20 for a motor, which has a central disc section 21 and a cylindrical peripheral section 24.

[0024] In this example, the disc portion 21 has nine countersunk holes 23 punched therein to move a center of mass of the sensor wheel 20 away from a rotational axis of the sensor wheel 20. A number of fixing holes 29 are further provided in the disc portion 21 for use in securing the sensor wheel 20 to the crankshaft 10. Each of the fixing holes 29 has a chamfered lead-in.

[0025] The disc portion 21 has a central opening 22 having a diameter sufficiently large to allow the sensor wheel 20 to be mounted past the flywheel flange 12. The central portion 21 is thus circular, with an inner edge defined by the central opening 22 and an outer peripheral edge aligned with an outer surface of the cylindrical rim portion 24.

[0026] The cylindrical rim portion 24 has a series of spaced-apart punched openings 25. Pickup gear teeth 26 are formed by lands between adjacent openings 25. In this example, there are sixty pickup gear teeth 26 and two missing teeth formed using a reference opening 28 that is circumferentially much longer than one of the other openings 25.

[0027] The cylindrical rim portion 24 has an inner radius sufficiently large to allow the cylindrical rim portion 24 to fit over the counterweight 11 when the sensor wheel 20 is mounted on the crankshaft 10.

[0028] The encoder wheel 20 is formed from a single piece of steel, which is deformed to create the disc and surround sections 21 and 24. In this case, the encoder wheel 20 is formed by a stamping process and is thus a stamped steel encoder wheel.

[0029] An advantage of the encoder wheel 20 is that the length of each encoder wheel tooth 26 is not limited to the thickness of the material used to manufacture the encoder wheel 20. Each encoder wheel tooth 26 is much longer than the thickness of the disc portion 21 because it is formed in the folded cylindrical rim portion 24 of the encoder wheel 20. Thus, the encoder wheel 20 can be made of a relatively thin material, such as 0.0025 mm thick steel, which can be relatively easily formed into the desired shape, and the length of each encoder wheel tooth 26 can be 0.01 m.

[0030] Thus, it can be kept relatively thin since the thickness of the encoder wheel 20 does not affect its performance in terms of reliable signal generation.

[0031] A further advantage of using a cylindrical, folded-over rim section 24 is that it creates a cage-like structure, protecting the encoder teeth 26 from damage. Furthermore, the encoder teeth 26 are more resistant to bending than individual teeth of the same size would be because the encoder teeth 26 are formed as part of the cylindrical rim section 24.

[0032] Due to the displacement of the center of mass of the encoder wheel 20 relative to its axis of rotation, a rotation of the encoder wheel 20 generates an unbalance force in a radially outward direction on a vector 'V' (see Fig. 3a), which passes through both the center of mass and the rotation axis. In this example, the vector 'V' is positioned at an angle θ, which, measured from an upper one of the fixation holes 29, is 3.414 radians (195.6 degrees).

[0033] The strength and direction of this unbalance force depends on the thickness of the material used to manufacture the sensor wheel 20, the positioning, size and number of openings 23 and the rotational speed of the sensor wheel 20.

[0034] In order to allow the installation of the sensor wheel 20 within the limitations of the cylinder block 3, the counterweight 11 is provided with a recess 11r ( Fig. 6) into which the sensor wheel 20 fits. The central opening 22 of the annular disc portion 21 of the sensor wheel 20 is dimensioned to provide a slight sliding fit on a circumferentially extending inner wall 11w of the recess 11r, thereby providing radial positioning of the sensor wheel 20 on the crankshaft 10. The depth of the recess 11r substantially corresponds to the thickness of the material in the disc portion 21 of the sensor wheel 20. The loss of material of the counterweight 11 due to the recess 11r and its balancing effect is compensated for by the unbalancing effect of the sensor wheel 20, so that when the sensor wheel is attached to the crankshaft 10, the same balancing effect is provided as in the case where there is no recess and no sensor wheel 20.

[0035] The sensor wheel 20, in this example, is attached to the crankshaft 10 using three threaded fasteners 30. Each of these threaded fasteners 30 has a cylindrical shaft portion for cooperating with a positioning counterbore 37 in the crankshaft 10 and a threaded end portion. Each threaded fastener 30 extends through a respective one of the three locating holes 29 in the disc portion 21 of the sensor wheel 20 for engagement with a threaded bore 31 in the crankshaft 10. The sensor wheel 20 is attached to the crankshaft 10 such that the cylindrical skirt portion 24 extends away from the adjacent end wall 3e of the cylinder block 3 and overlies the counterweight 11.

[0036] Thus, the size and positioning of the balancing holes 23 in the disc portion 21 are designed to compensate for the loss of balance weight from the counterweight 11. It should be understood that the balancing holes 23 are arranged at an angle such that the offset center of mass of the sensor wheel 20 is positioned to compensate for the loss of material from the counterweight 11 due to the recess 11r. Thus, the balancing effect of the counterweight 11 and the sensor wheel 20 during rotation of the crankshaft 10 is substantially identical to that provided by the counterweight 11 without the recess 11r.

[0037] The use of such a sensor wheel 20 thus enables the installation of the sensor wheel 20 within the constraints of the cylinder block 3 without the need to increase the length L of the cylinder block 3.

[0038] As in Fig. 5 and Fig.9, a sensor 50 forming part of an engine control system is positioned very close to the cylindrical rim portion 24 of the sensor wheel 20 for detecting the passage of the sensor wheel teeth 26 in use.

[0039] Thus, in brief, an essential feature of the present invention is the combination of a bent / cage type encoder wheel design with punched balance holes, thereby eliminating the need for 100% balancing of the component.

[0040] Such a sensor wheel can be installed in the engine with minimal loss of available counterweight (the wheel is thin and holds the mass in the same angular position as the counterweight).

[0041] The use of a bent gear / cage design for the teeth allows the associated sensor to be positioned further forward in the cylinder block without requiring a thicker sensor wheel. The bent gear / cage design forms a closed band that protects the teeth from damage.

[0042] Because very little material needs to be removed from the counterweight, this allows the counterweight to be thick enough for balancing holes to be drilled on the production line, thus maintaining line cadence and cost-effective production processes.

[0043] A thin encoder wheel also allows the component to be punched.

[0044] A stamped encoder wheel is inexpensive to manufacture and allows accurate control of the part's imbalance without a 100% balance check.

[0045] It will be apparent to those skilled in the art that, although the invention has been described with reference to one or more exemplary embodiments, it is not limited to the disclosed embodiments and that alternative embodiments could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

[1] Engine (1) having a crankshaft (10) positioned in a cylinder block (3) of the engine (1), wherein the crankshaft (10) has at one end a flywheel flange (12) for attaching a flywheel (8) and a number of counterweights for providing dynamic balancing of the crankshaft (10) in use, comprising an end counterweight (11) positioned very close to an end wall (3e) of the cylinder block (3), the end counterweight (11) having a recess (11r) formed therein in which a sensor wheel (20) is mounted, the sensor wheel (20) is punched from a single piece of steel and a central circular section (21) and a folded cylindrical border portion (24), wherein the folded cylindrical border portion (24) is arranged around an outer circumference of the central circular portion (21), extends away from one end wall (3e) of the cylinder block (3), has an inner radius which is sufficiently large for the cylindrical rim portion (24) to fit over the end counterweight (11) when the encoder wheel (20) is mounted on the crankshaft (10), and a plurality of circumferentially spaced-apart encoder wheel teeth (26), wherein there are a number of circumferentially spaced-apart openings (25) in the folded cylindrical rim portion (24), and each of the encoder wheel teeth (26) is formed by a web between two adjacent openings (25) in the folded cylindrical rim portion (24), thus forming a cage-like structure, and wherein the central circular portion (21) a central opening (22) with a diameter sufficiently large to allow the sensor wheel (20) to be mounted past the flywheel flange (12), and a number of compensating openings (23) formed therein in order to move a center of mass of the sensor wheel (20) away from a rotational axis of the sensor wheel (20), wherein the compensating openings (23) of the central circular section (21) of the sensor wheel (20) are arranged at an angle and the sensor wheel (20) has an unbalanced mass which, in cooperation with the arrangement of the compensating openings (23), compensates for an unbalance effect of the material lost from the end counterweight (11) due to the recess (11r). [2] A motor according to claim 1, wherein each encoder wheel tooth (26) extends substantially parallel to the axis of rotation about which the encoder wheel (20) rotates in use. [3] An engine according to claim 1 or claim 2, wherein the central circular portion (21) defines a number of circumferentially spaced fixing holes (29) used to fix the sensor wheel (20) to the crankshaft (10) of the engine (1). [4] Motor according to claim 1, wherein the number of compensating openings (23) are circumferentially spaced and the dimensioning, spacing and positioning of the compensating openings (23) in the encoder wheel (20) is designed to compensate for the material lost from the end counterweight (11) due to the recess (11r). [5] Motor according to claim 1, wherein the depth of the recess (11r) in the end counterweight (11) substantially corresponds to the thickness of the central circular portion (21) of the encoder wheel (20).

Images