DE3943605C2 - Starter with pinion rotated by electromotor - Google Patents

Abstract

The starter has a pinion (5) driven by an electromotor. An electromagnetic switch (31) has a plunger (7) to move the pinion axially. A spring (21) presses the pinion against a cog belonging to the motor before the pinion can be rotated. The spring is a conical coil, compressed and located in the plunger. Alternatively, one end of a lever (10) may be connected directly to the plunger and its other end may be connected to the pinion (5). The coiled spring is at a rotation section (10a) that rotates until the pinion comes up against the motors cog and them moved back so that the spring is deflected.

Description

The invention relates to an electromagnetic attraction unit a starter motor.

An electromagnetic attraction unit for a starter motor, which belongs to the patent holder's internal prior art, is shown in FIG. 1.

The electromagnetic attraction unit is contained in an electromagnetic switch ( 6 ) which is provided next to a direct current motor ( 2 ) of a one-way clutch, which is slidably attached to the output shaft ( 3 ) of the motor, in order to form a starter. The arrangement also includes a one-way lever ( 10 ), one end of which engages with a hook ( 8 ), which is connected to the plunger ( 7 ) of the electromagnetic switch ( 6 ), and the other end of which engages with the cylindrical rear end section ( 9 ) of the one-way clutch outer ring ( 4 b) of the one-way clutch ( 4 ) stands to move the one-way clutch ( 4 ) on the output shaft ( 3 ).

The electromagnetic switch ( 6 ) for actuating the engagement lever ( 10 ) has a cylindrical outer frame ( 11 ) which has a wall ( 11 a) at one end. The plunger ( 7 ) listed above is inserted into the end wall ( 11 a). A stationary iron core ( 12 ) is attached to the other end of the outer frame ( 11 ) such that it faces the plunger. The iron core has an end wall ( 12 a) which is firmly inserted in the rear end portion of the outer frame and thus forms a frame together with the outer frame ( 11 ). A coil former ( 13 ) is accommodated in the frame thus formed. An excitation coil ( 14 ) is wound on the coil body ( 13 ). A return spring ( 15 ) is inserted between the iron core ( 12 ) and the plunger ( 7 ). The iron core ( 12 ) has a central passage opening in which a rod ( 16 ) is slidably inserted such that one end portion (or front end portion) extends from the iron core ( 12 ) towards the plunger. The other end portion (or rear end portion) of the rod ( 16 ) carries a movable contact ( 17 ).

The starter further comprises: a return spring ( 18 ) for returning the rod ( 16 ) to a predetermined position; a cap ( 19 ) made of resin; and a contact pin ( 20 ) which is received in the cap ( 19 ) so that its inner end serves as a stationary contact ( 20 a) with which the movable contact ( 17 ) is brought into contact.

The plunger ( 7 ) is inserted into the central opening formed in the end wall ( 11 a) of the outer frame ( 11 ) and is moved along the central axis of the coil former ( 13 ) against the iron core ( 12 ). The plunger ( 7 ) has a recess ( 7 a) which opens axially outwards. The hook ( 8 ) described above is in the form of a piston and has a flange ( 8 a) at its rear end. The hook ( 8 ) is slidably inserted into the recess ( 7 a) of the plunger ( 7 ), extends outwards and passes through the central opening, which is formed in a holder ( 21 ) that the open end of the recess ( 7 a) of the plunger ( 7 ). The outer end portion of the hook ( 8 ) is engaged with the upper end of the engagement lever ( 10 ). Inside the recess ( 7 a) of the plunger ( 7 ) is a cylindrically wound spring, namely a compression spring ( 22 ) between the holder ( 21 ) and the flange ( 8 a) of the hook ( 8 ).

It then operates in this way assembled electromagnetic attraction unit in connection with the starter briefly explained.

If the ignition switch of the vehicle is turned on, the excitation coil of the electromagnetic switch ( 6 ) is excited so that the plunger ( 7 ) is moved against the iron core ( 12 ). As a result, the engagement lever ( 10 ) is rotated so that the one-way clutch ( 4 ) and the pinion ( 5 ), which is made in one piece with the inner clutch ring ( 4 a), are moved on the output shaft ( 3 ). In this process, when the pinion ( 5 ) abuts against the side of the ring gear, the rotation of the engagement lever ( 10 ) is stopped while the plunger ( 77 ) is moved against the iron core, the compression spring ( 22 ) is compressed, so that the Pinion is pressed against the motor sprocket by means of the engagement lever ( 10 ).

While the plunger ( 7 ) abuts the rod ( 16 ), the movable contact ( 17 ) is brought into contact with the stationary contact ( 20 a), so that the DC motor ( 2 ) is switched on. As a result, as soon as the pinion ( 5 ) is rotated, it is brought into engagement with the motor ring gear by the spring force of the compression spring ( 22 ).

The relationship between the force of attraction of the plunger ( 7 ) and the spring force of the compression spring ( 22 ) in the electromagnetic switch is indicated in the characteristic curve according to FIG. 2, in which the vertical axis represents the force and the horizontal axis represents the distance (or the gap) (g ) between the plunger ( 7 ) and the iron core ( 12 ). That is, in Fig. 2, the curves (P, P ') indicate the tappet force characteristics and the straight line (S) the spring characteristic of the compression spring ( 22 ). Generally, the starter power supply is a 12 V storage battery, and in this case the tappet force characteristic is given by curve (P). In practice, however, the excitation coil ( 14 ) is excited with a voltage which is approximately two thirds (2/3) of the system voltage, due to various factors, such as a temperature rise; ie if a voltage of about 8 V is supplied to the excitation coil ( 14 ), the tappet force characteristic curve is given by the curve (P ').

If, on the other hand, the movement of the tappet ( 7 ) causes the pinion ( 5 ) to strike the motor sprocket, the compression spring ( 22 ) becomes effective and the spring characteristic changes linearly with the movement of the tappet ( 7 ).

As shown in Fig. 2, the tappet force characteristic (P ') comes into contact with the characteristic (S) of the compression spring ( 22 ) when the force of attraction is slightly reduced due to a drop in voltage. At the point of contact, the plunger attraction force is in balance with the spring force of the compression spring ( 22 ), and consequently the plunger ( 7 ) is no longer moved against the iron core ( 12 ) and, as a result, the DC motor ( 2 ) is not energized. This difficulty can be overcome by using a compression spring with less spring force. However, this method is not practical because its spring force may not be large enough to cause the pinion to engage the engine ring gear.

In the electromagnetic switch constructed in this way, the return spring ( 15 ) for returning the plunger ( 7 ) between the plunger ( 7 ) and the stationary iron core ( 12 ) is mounted in such a way that it shows the inner cylinder wall of the coil body ( 13 ) according to FIG. is closest, reducing the magnetic cross section of the magnetic path. Accordingly, the force of attraction is reduced, and in particular the initial force of attraction of the plunger is reduced.

In order to overcome this difficulty, the known magnetic switch ( 6 ) according to FIG. 3 has been improved. That is, in the improved magnetic switch, the return spring ( 15 ) is arranged between the plunger ( 7 ) and the stationary iron core ( 12 ) so that it is closest to the central axis of the coil body ( 13 ) in order to maintain the magnetic cross section of the magnetic path .

However, the electromagnetic switch is still disadvantageous in terms of the fol lowing: In the electromagnetic switch, the Rückfefe ( 15 ) is inserted into a recess which is formed along the passage opening of the iron core ( 12 ) into which the rod ( 16 ) is inserted, namely in such a way that the recess is deep enough to hold the base portion of the return spring ( 15 ). Therefore, the dimension (a) of the rod holding portion of the iron core is reduced, and the rod ( 16 ) has corresponding play.

From DE-GM 77 31 335 is an electromagnetic Stellvor direction known, in which a cylindrically wound spring in an excitation coil between a stationary iron core and a movable iron core is used. The moveable che iron core has a center on its end face arranged recess, which is initially conical and aligned which is followed by a cylindrical bore section. Of the stationary iron core has a cone on its face butt-shaped projection, which in turn on his forehead Surface has a cylindrical recess.

An electromagnetic valve is known from US Pat. No. 2,650,617 knows that has a conically wound spiral spring, the is arranged outside the excitation coil.

The invention has for its object an electromagnetic table tightening unit to create the magnetic cross cut maintained without causing play of the staff things that deliver great attraction.

This object is achieved by the electromagnetic cal tightening unit with the features of claim 1 solved.

In the electromagnetic attraction unit, during the movable iron core is attracted to the stationary core, the conically wound spring compressed. With this The process moves each of the coils of the spring to the next win dung with a larger diameter, and therefore the  compressed spring length relatively short. Therefore, the formed in the face of the stationary iron core Recess for receiving the compressed spring in axial dimension be short, which is the one listed above Difficulty eliminates the magnetic cross section is reduced.

Embodiments of the Invention are described below the adjacent Drawings explained in more detail; it shows

Fig. 1 a cross section of a related internal prior art of the patentee electromagnetic tightening unit in a known starter;

Fig. 2 is a characteristic curve which indicates the attraction force of the electromagnetic switch and the spring characteristic curve of a compression spring which can press against a pinion in the known starter;

Fig. 3 is a cross section of a known electromagnetic switch which is provided to improve the electromagnetic switch of the starter shown in Fig. 1;

Fig. 4 is a sectional view of an electromagnetic switch in a starter, in which an electromagnetic attraction unit according to the invention is used;

Fig. 5 is a sectional view of a plunger which is attracted against a stationary iron core in the electromagnetic switch of Fig. 4;

Fig. 6 is a sectional view of an electromagnetic switch in a starter in which the electromagnetic attractive unit of the invention is used;

Fig. 7 is a sectional view of a plunger which is attracted against a stationary iron core in the electromagnetic switch according to Fig. 6; and

Fig. 8 is a graph showing the attraction forces of the above two inventive electromagnetic switches according to the invention, and a known electromagnetic switch.

The preferred embodiments of the invention are described in Described with reference to the accompanying drawings.  

FIGS. 4 and 5 show an electromagnetic switch, in which a first embodiment of an electromagnetic tightening unit according to the invention is used, and FIGS. 6 and 7 illustrate a solenoid switch (140) constitute, in which a second embodiment of an electromagnetic tightening unit according to the invention is used. In these figures, components which correspond functionally to those described above in connection with FIG. 1 are therefore designated with the same reference numbers or symbols.

In the electromagnetic switch (130) has a cylindrical recess (131) of FIG. 4 disposed in the inner end face of a stationary core (12) such that its center axis coincides with that of the stationary iron core (12). An end portion ( 132 a) of a conically wound spring ( 132 ), which has a larger diameter than the other end portion ( 132 b), is attached along the circumference of the bottom of the cylindrical recess. The depth of the recess ( 131 ), ie the axial dimension of the recess, is substantially equal to the length of the compressed, conically wound spring (which is subsequently indicated as "compressed length" where necessary).

The conically wound spring ( 132 ) gradually decreases in diameter from one end to the other end, as can be seen from its design. When the spring ( 132 ) is compressed, each of its turns goes inside the next larger diameter turn, and therefore the compressed length of the spring ( 132 ) is relatively small. Accordingly, the axial depth of the recess ( 131 ) formed in the inner end face of the stationary iron core ( 12 ) can be small, and the noticeable length of the passage opening of the stationary iron core ( 12 ) is therefore long enough to hold the rod ( 16 ), and play of the rod ( 16 ) is prevented.

On the other hand, a circular projection ( 133 ) of small thickness is formed in the middle on the inner end face of the plunger ( 7 ) and faces the stationary iron core ( 12 ). The small diameter end portion ( 132 b) of the conically wound spring ( 132 ) is placed on the circular projection ( 133 ). Thus, the tapered spring ( 132 ) is positioned in place.

As is apparent from the above description, in the electromagnetic switch according to the invention, without the operation of the same being adversely affected, the plunger return spring is arranged closer to the central axis of the stationary iron core than in the known electromagnetic switch, with which the magnetic cross section is maintained, with the result that the Attraction is improved. Is Reference is also 8 to FIG. Indicative of the attraction force (characteristic curve (A)) of the electromagnetic switch (130) of FIG. 4 and the attraction force (characteristic curve (B)) of the known electromagnetic switch (6) of Fig. 1, so It can be seen that the electromagnetic switch ( 140 ) has a greater initial attraction than the electromagnetic switch ( 6 ).

In the electromagnetic switch (140) of FIG. 6 there is formed a recess in the form of a truncated cone in the inner end face of the stationary iron core (12) such that the central axis of the recess is substantially coincident with that of the stationary iron core (12). On the other hand, a frustoconical projection ( 142 ) is formed on the inner end face of the movable iron core, namely a plunger ( 7 ) arranged in the middle, which extends against the stationary iron core ( 12 ). A conically wound spring ( 143 ) is inserted between the plunger ( 7 ) and the stationary iron core ( 12 ) in such a way that the small-diameter end section ( 143 a) is fastened to the inner end section of the rod ( 16 ) and arranged on the bottom wall of the recess is, while the end portion ( 143 b) with a large diameter surrounds the projection ( 142 ) and bears against the end face of the plunger ( 7 ).

Both the recess ( 141 ) and the projection ( 142 ) are designed in the form of a truncated cone; however, the former ( 141 ) is larger than the latter ( 142 ). Therefore, when the face of the plunger ( 7 ) abuts against the face of the stationary iron core ( 12 ) when it is attracted, a space is formed between the recess ( 141 ) and the projection ( 142 ) to receive the conically wound spring ( 143 ) compressed .

Thus, in the electromagnetic switch ( 140 ) of FIG. 6, in a similar manner to the electromagnetic switch ( 130 ) according to FIG. 4, without adversely affecting the operation, the plunger return spring can be arranged closer to the central axis of the stationary core, whereby the magnetic cross section is maintained . Furthermore, the tapered surfaces of the recess ( 141 ) of the stationary iron core and the projection ( 142 ) of the plunger are substantially parallel to one another when viewed in cross section, so that the magnetic flux flow path is reduced there accordingly. Therefore, the electromagnetic switch has a larger initial attraction.

The attraction force of the electromagnetic switch shown in FIG. 6 is indicated by the characteristic (C) of FIG. 8. As shown in Fig. 8, of the above-described electromagnetic switches , the electromagnetic switch ( 140 ) shown in Fig. 6 has the greatest initial tightening force achieved when the distance or gap (g) between the stationary iron core ( 12 ) and the plunger ( 7 ) is largest.

As previously described, with the starter tightening unit according to the invention when the pinion by the Tappet attraction force against the motor ring gear the force exerted on the pinion after the Pinion strikes against the motor sprocket, in a Deflection force of the conically wound compression spring converted, and this deflection force pushes the pinion against the Motor gear ring. Therefore, the pressure force of the Ritzels against the motor ring gear in a square Course similar to the ram tightening characteristic. Consequently this starter doesn't show the problem  on that when the voltage to operate the Electromagnetic switch slightly decreased that Tappet tightening force in equilibrium with the spring force of the Compression spring arrives so that the engine does not start. Thus, the starter can be manufactured be without a large electromagnetic switch too use.

As previously described, in Electromagnetic switch the conically wound spring for Retrieval of the movable iron core between the stationary Iron core and the movable iron core, as well as in arranged essentially along the central axis, with what the magnetic cross section is maintained without the Operation of the electromagnetic switch disadvantageously influence. For this reason, the invention Electromagnetic switch has a greater attraction than that deliver known electromagnetic switches; in other words, for the same attraction, the invention Electromagnetic switches are sized smaller than that well-known magnetic switch.

Claims (4)

1. Electromagnetic attraction unit of a starter motor with:

• - an excitation coil ( 14 );
• - A stationary iron core ( 12 ) with an end face;
• - A movable iron core ( 7 ) with an end face which is opposite the end face of the stationary iron core ( 12 ), the movable iron core ( 7 ) being arranged coaxially to the stationary iron core ( 12 ) and being moved by electromagnetic force against the stationary iron core; and
• - A conically wound spring ( 132 ; 143 ) which is inserted within the excitation coil ( 14 ) between the stationary iron core ( 12 ) and the movable iron core ( 7 ), and which runs essentially coaxially with the stationary iron core and the movable iron core; in which
• - The end face of the stationary iron core ( 12 ) has a centrally arranged recess ( 131 ; 141 ) which has an axial depth which is equal to the axial length of the compressed, conically wound spring ( 132 ; 143 ), and one end of the conically wound Spring is arranged in the base of the recess ( 131 ; 141 ); and where
• - The end face of the movable iron core ( 7 ) has a projection ( 133 ; 142 ) which surrounds the other end of the conically wound spring ( 132 ; 143 ).

2. tightening unit according to claim 1, characterized in that the recess ( 131 ) is cylindrical and the projection ( 133 ) are circular. 3. tightening unit according to claim 1, characterized in that the recess and the projection have a truncated cone shape ( 141 ; 142 ). 4. tightening unit according to claim 1, characterized in that the conically wound spring ( 132 ; 143 ) gradually reduces in diameter from one end to its other end so that each winding of the spring ( 132 ; 143 ) when compressed in the Inside of the next winding with a larger diameter goes.