WO2014062106A1

WO2014062106A1 - Starter pulley, starter unit and motor unit

Info

Publication number: WO2014062106A1
Application number: PCT/SE2012/051119
Authority: WO
Inventors: Christoph Schiedt
Original assignee: Husqvarna Ab
Priority date: 2012-10-19
Filing date: 2012-10-19
Publication date: 2014-04-24

Abstract

The present application in particular relates to a starter pulley (1) adapted to be coupled to a crankshaft of an internal combustion engine in a starting operation. In more detail, a coupling interface (4) of the starter pulley (1) is adapted to be coupled to the crankshaft at least during the starting operation and is positioned in an off-center position (O) relative to the starter pulley (1).

Description

Title: Starter pulley, starter unit and motor unit

Background

The present application in particular is directed to a starter pulley to be coupled to a crankshaft of an internal combustion engine. Starting operations of internal combustion engines in general involve rotation of a respective crankshaft. A force-path experienced or occurring during rotation of the crankshaft is extremely indifferent and varies between high forces in compression and low forces in expansion strokes. The indifferent force-path occurring during a starting operation in many cases complicates starting of respective internal combustion engines, in particular with manual operated pullback starters.

It is therefore an object of the invention to provide a possibility to improve starting of internal combustion engines. In particular, starting operations, in particular manual starting operations, shall be made more effective, shall be simplified and made more convenient to the user.

Summary of the invention This object is solved by claims 1, 5 and 6, respectively proposing a starter pulley, starter unit and motor unit. Embodiments thereof result from respective dependent claims and the description blow and further below.

According to claim 1, a starter pulley is provided, which is specially adapted to be coupled to a crankshaft of an internal combustion engine in a starting operation, i. e. at least in or during a starting operation. A coupling, i.e. a coupling interaction, between the starter pulley and the crankshaft may be accomplished by a special latching or engagement mechanism adapted to automatically establish the coupling connection during or at the start of a starting operation. The latching or engagement mechanism may further be adapted to automatically release the coupling connection between the crankshaft and starter pulley once the internal combustion engine is running . Such latching or engagement mechanisms may for example comprise centrifugal force acting elements. The starter pulley as proposed comprises an interface, in particular a coupling interface, which is adapted and implemented to be coupled to the crankshaft of the internal combustion engine at least during the starting operation. In more detail, a coupling interface is provided, which in particular may comprise the latching or engagement mechanism as mentioned beforehand, and which may be adapted to selectively couple to the crankshaft in or during a starting operation.

According to the proposed starter pulley, the interface, in particular coupling interface, is positioned and arranged relative to the starter pulley, in particular relative to a circumference or surface area of the starter pulley, in an off- center position. Relative to the coupling interface, which may coincide with a rotational axis of the crankshaft, the off-center position in particular leads to an eccentric type starter pulley. An off-center position shall, in particular in accordance with an embodiment, mean a position spaced away, remote or distant from at least one of a center of area, center of rotation of the starter pulley and center of mass of the starter pulley. As a pulley in general has an oblate shape and preferably is disc-shaped, the center of area, center of rotation and/or center of gravity shall refer to the oblate cross section of the starter pulley.

Providing the interface, in particular the coupling interface, in an off-center position has the advantage, that a torsional moment exerted or effective at or to the crankshaft can be modulated or varied in particular in accordance with the force-path or force progression occurring in rotating the crankshaft of the internal combustion engine during a starting operation. Here, it shall be mentioned, that starting an internal combustion engine in general requires overcoming high and low compression stages of related high and low compression strokes of the internal combustion engine. Implementing the coupling interface in the off-center position on or at the starter pulley is effective to modulate a force or moment of force path in accordance with re- spective high and low compression stages. In this way, a comparatively con^¬ stant starting drive can be exerted to the crankshaft in order to start the in^¬ ternal combustion engine.

As a result of adapting the starting torque or starting force to be exerted to the crankshaft in accordance with or similar to the force path of the crankshaft during a starting phase, a comparatively smooth and continuous starting pow^¬ er can be obtained during a starting operation of the internal combustion engine. Hence the starting operation can be carried out with almost constant ro^¬ tational speed and reduced overall energy consumption and effort.

It shall be noted that the invention in particular can be applied essentially to arbitrary types of starting units, in particular to manual, springload, electric starter units and others. In particular, the starter pulley may be used in a manual recoil starter unit, where in general a starting rope is used to transfer a starting force to the starter pulley and to rotate the starter pulley in and during a starting operation.

In a particularly preferred embodiment of the starter pulley, it is provided that the starter pulley is in the form of a disc having a circular cross section. The respective cross section in particular shall refer to a plane perpendicular to the interface, in particular coupling interface of the starter pulley, i.e. perpendicu^¬ lar to a longitudinal axis of the crankshaft, at least a longitudinal axis of a crankshaft stub, to be coupled to the starting pulley coupling interface during a starting operation.

As already mentioned above, providing a starter pulley, in particular a starter pulley where an external force is or will be applied to a circumference of the starter pulley, and which starter pulley has a circular cross section with a coupling interface provided in an off-center position may lead, under the action of an almost constant external force, to a torque path corresponding to the one required for rotating the crankshaft. In particular, reduced pulling forces, in particular with manual pullback starters, and preferably almost continuous staring speeds can be obtained . This in turn will lead to effective and more efficient starting operations, in particular with manual operated starters, in particular with manual recoil starters. In one preferred embodiment, the starter pulley, at least a circumferential face side thereof, is implemented as a reel adapted to accommodate a starter rope of a manual recoil starter. In this configuration, the starter is intended for a manual starting operation of the internal combustion engine. Due to the eccentric location or position of the coupling interface of the starter pulley, it is possible that the force path in a starting action or operation can essentially be kept at a constant level . A constant force path, probably together with an almost constant rotational speed, may greatly simplify manual starting operations, and the overall progress of a starting operation or action may be rectified . In particular, the overall effort and energy consumption required for a starting operation or action can advantageously be reduced .

As can be seen, the proposed starter pulley is effective in providing enhanced and improved starting operation cycles, in particular with manual recoil starters.

According to claim 5, a starter unit comprising a starter pulley according to any embodiment and variant as described further above is proposed. As to ad- vantages and advantageous effects of the starter unit, reference is made to the description further above.

Note that the starter unit in particular may be implemented as a manual recoil starter unit. In general, the starter unit, but also starter pulley may be used for any type of internal combustion engine. In particular, the starter unit and starter pulley may be used for manual operated combustion engine driven devices or hand-held equipment. According to claim 6, a motor unit of internal combustion type is proposed. The motor unit comprises an internal combustion engine, in particular motor, having a crankshaft and a starter unit as described further above. The starter unit is adapted to be coupled to the crankshaft in a starting operation, in particular in a manual starting operation.

As to advantages and advantageous effects of the motor unit, in particular owing to the starter unit, reference is made to the description above and further above. In particular, it is possible to obtain smooth starting operations requiring less energy as compared to conventional starting operations. This in par- ticular is advantageous for manual recoil starting mechanisms.

In an embodiment of the motor unit, the coupling interface coupled or to be coupled with the crankshaft is off-centered relative to the starter pulley in such a way that a torque fluctuation during the starting operation, in particu- lar caused by compression and expansion strokes, essentially is balanced or compensated by a lever arm fluctuation of the starter pulley. This in particular is of advantage if an external starting force engages at a circumference of the starter pulley, which for example is the case with manual recoil starters. In other words, the interface, in particular coupling interface, is off-centered in such a way, that upon rotating the starter pulley during a starting operation, an effective lever arm provided with the starter pulley corresponds to the torque fluctuation during a respective starting operation, i.e. the torque required for rotating the crankshaft.

In an embodiment of the motor unit, it is provided that at least one point of interaction between the crankshaft and the starter pulley is defined such that an effective lever arm provided by the starter pulley varies in accordance with the torque fluctuation or variation for any regular starting rotation of the crankshaft. Here, in particular a latching mechanism may be provided which is adapted to latch the starter pulley and crankshaft at predefined angular rela- tions in or during a starting operation, and which is adapted to release a coupling engagement between crankshaft and starter pulley when the internal combustion motor is running .

The predefined angular relations or predefined latching angles are defined such that in any regular starting operation, the starter pulley and crankshaft are coupled in such an angular relationship that a torque path of the starter pulley corresponds or matches a force path of the internal combustion engine.

It is of great advantage, if the point of interaction is such that a maximal lever arm is effective in, at or near a top dead center of the internal combustion engine, and that a minimal lever arm is effective in, at or near a bottom dead center of the internal combustion engine.

Embodiments of the invention will now be described in connection with the annexed figures, in which :

Fig . 1 shows a starter pulley in a first configuration; and

Fig . 2 shows the starter pulley in a second configuration. Detailed description of preferred embodiments

Fig . 1 shows a starter pulley 1 in a first configuration. The starter pulley 1 as shown in the figures is implemented for a manual recoil type starter unit.

Therefore, the starter pulley 1, in more detail a circumferential face side thereof, is implemented as a reel adapted to accommodate a starter rope 2.

One end of the starter rope 2 is fixed to the starter pulley 1 while at the other end of the starter rope 2 is attached to a handle 3. In a starting operation carried out with the starter pulley 1, a user can pull the starter rope 2 off the starter pulley 1 by using the handle 3, which is indicated by an arrow in the Fig . 1.

In pulling the starter rope 2 from the starter pulley 1, the starter pulley 1 will be rotated, i .e. will carry out a rotating movement. The rotating movement of the starter pulley 1 can be used to start an internal combustion engine coupled to the starter pulley 1. In more detail and in general, in a starting action or starting operation carried out via the starter pulley 1, a rotational movement of the starter pulley 1 is transmitted or transferred to a crankshaft (not shown) of the internal combustion engine.

The crankshaft may be coupled to the starter pulley 1 via a latching mechanism adapted to latch the starter pulley 1 and crankshaft during a starting action and to allow free rotation of the crankshaft once the internal combustion motor has started running .

In any case, a type of coupling interface 4 is provided at the starter pulley 1 which is adapted to be coupled to the crankshaft of a respective internal combustion engine at least during a starting operation. The coupling interface 4 is aligned and essentially in line with a center or longitudinal axis of the crankshaft of a respective internal combustion engine. As can be seen from Fig . 1, the coupling interface 4 is positioned in an off- center position relative to the starter pulley 1. In the present case, the starter pulley 1 has a circular disc-shaped geometry and the coupling interface 4 is shifted from, i .e. distant from, the center 5 of the circular disc-shaped starter pulley 1. In more detail, the interface 4 is positioned and provided offset from the center of area, i .e. the center 5 of the circular cross-sectional area. A respective offset is designated with reference sign O.

If the starter pulley 1 is operated in a starting action, the starter rope 2 is pulled off the starter pulley 1 via handle 3 by manual action of a user. In unwinding or pulling the starter rope 2 off the starter pulley 1, pulling forces exerted by the user are effective at an outer circumference of the starter pulley 1, i.e. at a roll-off point 6 of the starter pulley 1. Due to the fact that the coupling interface 4 is in an off-center position relative to the starter pulley 1, an effective lever arm respectively defined between the coupling interface 4, in more detail a center of the coupling interface 4, and the roll-off point 6 at the starter pulley 1 varies between a maximal lever arm M and minimal lever arm m . Note that for clarity reasons re- spective lever arms are depicted only in Fig. 2 which shows the starter pulley 1 in a second configuration.

In Fig. 2, the minimal lever arm m is effective, whereas in the configuration shown in Fig. 1, the maximal lever arm M is effective. In pulling the starter rope 2, the starter pulley 1 exerts a rotating movement in which the coupling interface 4 adopts the function of or defines a pivot axis around which the starter pulley 1 is rotated.

During a starting action of an internal combustion engine, comparatively high, i.e. maximal, forces or moments of force are required at or close to the top dead center of the internal combustion engine stroke. Comparatively low, i .e. minimal, forces or moments of force are required at or close to the bottom dead center of the internal combustion engine stroke. With the starter pulley 1 as described beforehand it is possible, to couple the starter pulley 1 to the crankshaft of the internal combustion engine in such a way that the maximal lever arm M is effective at or near the top dead center and that the minimal lever arm m is effective at or near the bottom dead cen- ter. This is effective in balancing or compensating the torque or starting force fluctuation induced by respective stroke phases. In particular, maximal pulling forces required for starting the internal combustion engine can be lowered. Further, a comparatively continuous starting operation movement or speed can be achieved . In addition, the starting operation can be conducted with lower energy consumption as compared to conventional non-eccentric starter pulleys.

In all, it can be seen, that providing the coupling interface 4 in an off-center position relative to the starter pulley 1 is effective in easing and simplifying a starting operation for starting an internal combustion engine.

In the embodiment shown in the figures, the invention has been described in connection with a manual recoil starter. However, it shall be noted that the invention is not restricted to manual recoil starters, but may also applied to other types of starting mechanisms, in particular of spring-loaded, electrical type or others.

List of reference numerals

1 starter pulley

2 starter rope

3 handle

4 coupling interface

5 center of starter pulley

6 roll-off point

M maximal lever arm m m inimal lever arm O offset

Claims

1. Starter pulley (1) adapted to be coupled to a crankshaft of an internal combustion engine in a starting operation, wherein a coupling interface (4) of the starter pulley (1) is adapted to be coupled to the crankshaft at least during the starting operation and is positioned in an off-center position (O) relative to the starter pulley (1).

Starter pulley (1) according to claim 1, wherein the coupling interface (4) is provided offset from at least one of the center of mass, center of rotation (5) and center of area (5) of the starter pulley (1).

Starter pulley (1) according to at least one of claims 1 and 2, wherein the starter pulley (1) is in the form of a disc having a circular cross section.

Starter pulley (1) according to at least one of claims 1 to 3, wherein the starter pulley (1), at least at a circumferential face side of the starter pulley (1), is implemented as a reel adapted to accommodate starter rope (2).

5. Starter unit comprising a starter pulley (1) according to at least one of claims 1 to 4.

Motor unit of internal combustion type, comprising an internal combustion motor with a crankshaft and a starter unit according to claim 5, wherein the starter unit is adapted to be coupled to the crankshaft at least in a starting operation.

Motor unit according to claim 6, wherein the coupling interface (4) of the starter pulley (1) coupled with the crankshaft is off-centered (O) i such a way that a torque fluctuation during the starting operation essentially is balanced or compensated by a lever arm variation of the starter pulley (1). Motor unit according to at least one of claims 6 and 7, wherein at least one point of interaction between the crankshaft and the starter pulley (1) is defined such that an effective lever arm provided at the starter pulley (1) varies in accordance with a torque fluctuation for any regular starting rotation of the crankshaft.