Solenoid for a vehicle starter motor

Abstract

Solenoid (110) for a vehicle starter motor (100), wherein the solenoid (110) has: at least one coil (112, 114) with a passage (130) extending through the coil (112, 114); and a plunger (116) movably positioned within the passage (130), wherein the plunger (116) comprises a substantially cylindrical outer surface section (80) with a circumferential groove (82) formed in the outer surface section (80), characterized in that the plunger (116) is designed to move in an axial direction (166) between a first position (A) and a second position (D), wherein the at least one coil comprises a first coil (112) and a second coil (114), the first coil (112) being adjacent to the second coil (114), the first coil (112) and the second coil (114) being wound around a coil former (120) and the passage (130) extending through the coil former (120), further comprising a guide plate (72) positioned adjacent to an end of the coil former (120), the guide plate (72) being separated from the plunger (116) by a radial gap (70) and the radial gap (70) changing as the plunger (116) moves from the first position (A) to the second position (D) as a result of the movement of the groove (82) relative to the Guide plate (72) moves, with the groove (82) being located directly opposite the guide plate (72),when the plunger (116) is in the first position (A), and wherein the groove (82) is removed from the guide plate (72) in the axial direction (166) when the plunger (116) is in the second position (D), further comprising a tube (76) positioned in the coil former (120), wherein the plunger (116) is positioned inside the tube (76) and is designed to move in the axial direction (166) relative to the tube (76), the tube (76) extending past the guide plate (72) at one end of the coil former (120).

Description

AREA

[0001] This concerns the field of vehicle starter motors and in particular solenoids for starter motor assemblies. BACKGROUND

[0002] Starter motor units, which assist in starting engines, such as those in vehicles, are well known. A conventional starter motor unit is found in Fig. 23 shown. The starter motor assembly 200 of the Fig. Assembly 23 comprises a solenoid 210, an electric motor 202, and a drive mechanism 204. The solenoid 210 includes a coil 212, which is energized by a battery after the ignition switch is closed. When the solenoid coil 212 is energized, a plunger 216 moves in a linear direction, causing a shift lever 205 to rotate and engage a pinion 206 with a ring gear of a vehicle engine (not shown). When the plunger 216 reaches a plunger stop, electrical contacts are closed, connecting the electric motor 202 to the battery. The energized electric motor 202 then rotates, providing output torque to the drive mechanism 204. The drive mechanism 204 transmits the torque of the electric motor, via various drive components, to the pinion 206, which engages with the ring gear of the vehicle engine.Accordingly, the rotation of the electric motor 202 and pinion 206 leads to the cranking of the motor until the motor starts.

[0003] Many starter motor units, such as the starter motor unit 200 of the Fig. 23, are equipped with a "soft-start" starter motor engagement system. The purpose of a soft-start starter motor engagement system is to engage the starter motor's pinion with the motor's ring gear before full electrical power is applied to the starter motor. When the pinion and ring gear collide during this engagement, the motor provides a small torque to rotate the pinion, allowing it to properly engage with the ring gear before a high current is applied. The design of the solenoid, shift fork, electrical contacts, and motor drive is such that a high current is not applied to the motor until the gears are properly engaged. Accordingly, grinding of the pinion and ring gear in a starter motor with a soft-start engagement system is prevented.

[0004] Starter motors with a soft-start intervention system, such as that of the Fig. 23, typically comprise a solenoid with two different coils. The first coil is a pull-in coil 212 and the second coil is a holding coil 214. As in Fig. As shown in Figure 23, the draw-in coil 212 is first wound onto the coil former 220. The holding coil 214 is then wound onto this winding. Sometimes this order is reversed, so that the holding coil 214 is first wound onto the coil former 220, followed by the draw-in coil 212.

[0005] During operation of the starter motor, closing the ignition switch (typically after the operator turns a key) energizes both the starting coil 212 and the holding coil 214. Current flowing through the starting coil 212 at this time also reaches the electric motor 202, applying a limited current to the electric motor and causing the pinion to rotate with low torque. The energizing of the starting coil 212 and the holding coil 214 moves a solenoid shaft (referred to herein as the "plunger") in an axial direction. The axial movement of the solenoid plunger moves the shift lever 205 and directs the pinion 206 toward engagement with the motor's ring gear. Once the solenoid plunger reaches its plunger stop, a series of electrical contacts close, supplying full power to the motor.Closing the electrical contacts effectively short-circuits the pull-in coil 212, eliminating unwanted heat generated by the pull-in coil. With the pull-in coil short-circuited, however, the holding coil 214 provides sufficient electromagnetic force to hold the plunger in place and keep the electrical contacts closed, thus enabling the continued supply of full power to the electric motor 202. The fully energized electric motor 202 drives the pinion 206, which causes the motor's ring gear to rotate and thus cranks the vehicle's engine.

[0006] After the engine ignites (i.e., the vehicle starts), the vehicle operator opens the ignition switch. The electrical circuit of the starter motor assembly is designed such that opening the ignition switch causes a current to flow through the holding coil and the starting coil in opposite directions. The starting coil 212 and the holding coil 214 are designed such that, after the ignition switch is opened, the electromagnetic forces of the two coils 212 and 214 cancel each other out, and a return spring pushes the plunger 216 back into its original, unenergized position. As a result, the electrical contacts that had connected the electric motor 202 to the electrical power source are opened, and the electric motor is switched off.

[0007] To manufacture a high-performance vehicle starter motor with a soft-start engine engagement system, such as the one described earlier, designers face numerous design challenges. First, the pull-in coil must be precisely designed to avoid various problems that can arise during starter motor operation. As described above, when the pull-in coil of a soft-start starter system is energized (i.e., when the ignition switch contacts close as a result of the operator turning the ignition key), it provides an electromagnetic force to pull the plunger toward the plunger stop and into the closed position. However, the pull-in coil is electrically connected in series with the starter motor and should therefore have very low resistance.With low resistance through the starter coil, sufficient current flows through it and to the electric motor for the motor to deliver enough output torque to turn the pinion and avoid contact with the ring gear, as previously described. This required torque is typically 8–12 Nm. For a 12 V motor, the resistance can be on the order of 0.030 ohms, allowing several hundred amperes to flow through the motor and the series-connected starter coil during a soft start. However, this low resistance of the starter coil creates other design problems. First, if the soft start duration is prolonged or repeated starts are performed, a large amount of ohmic heat is generated in the starter coil due to the large current flowing through it.In a 12V system, this can be on the order of 3-4 kW, which can lead to thermal failure of the insulation system of the wiring forming the coil. Secondly, the high current through the pull-in coil generates a much stronger electromagnetic force on the plunger during closing than is necessary. This can become a problem if there is a collision between the pinion and the ring gear, and the impact force of the pinion on the ring gear can exceed 4500 N. As a result, the ring gear could break or chip. Over time and thousands of starts, the surface of the ring gear can deteriorate and require replacement for proper starting.

[0008] Design problems concerning the starting coil, such as those discussed in the preceding paragraph, lead to additional design problems with other components of the starter motor, such as the holding coil. As explained in the previous section, the starting coil, for example, has certain design constraints regarding the current flowing through it. Since the electromagnetic excitation is the product of coil turns times current, and since the current is fixed, the number of turns in the starting coil generally remains the primary design variable for the starting coil. Although the number of turns in the starting coil can be reduced to lessen the previously described problem of contact force, this presents a problem with the holding coil.In particular, the number of turns in the holding coil should match that of the pull-in coil so that, during the separation of the pinion and ring gear after the vehicle starts, the electromagnetic forces of the two coils cancel each other out, allowing the pinion to be cleanly pulled out of the ring gear. Before the vehicle starts, however, the holding coil remains energized for a much longer time than the pull-in coil. Therefore, the holding coil should not have a low resistance, or it will thermally fail. Thus, the resistance of the holding coil is generally an order of magnitude higher than that of the pull-in coil. The high resistance of the holding coil means that the current flowing through it before starting is relatively low, resulting in a relatively low ampere-turns product.If the number of turns of the holding coil is too low, then the holding coil provides insufficient magnetic force to keep the plunger closed, and the starter motor disengages before the vehicle starts.

[0009] As explained in the preceding paragraphs, designers of vehicle starter motors with a soft-start engine engagement system face conflicting design challenges for two coils that should generate equivalent electromagnetic forces. On the one hand, designers strive to limit the number of turns in the engagement coil to reduce the shock force during the engagement of the pinion and ring gear. On the other hand, designers strive to increase the number of turns in the holding coil so that it provides sufficient electromagnetic force to keep the plunger in a closed position while the engine is being cranked.

[0010] US 2006 / 0 001 513 A1 describes a solenoid with a coil and a passage extending through the coil. A plunger is movably positioned within the passage. The plunger has a cylindrical outer surface section with a circumferential groove formed in this outer surface section. The driving force of the plunger is to be kept constant within a predetermined range of motion.

[0011] US 4,686,501 A describes an electromagnetic actuator for a vehicle starter motor. The actuator has two coils and a passage extending through the coil. A plunger is movably positioned within the passage. Depending on the position of the plunger, the reluctance of a magnetic circuit changes.

[0012] DE 11 2005 002 756 T5 discloses an electromagnetic actuator with an excitation coil and a movable armature, which has a groove for influencing the reluctance as a result of movement of the armature.

[0013] CN 201 277 131 Y shows a construction of a linear solenoid in combination with a vehicle starter motor.

[0014] Accordingly, it would be desirable to provide a solenoid for a vehicle starter motor with a pull-in coil that limits the impact force during the engagement of the pinion and ring gear. It would also be desirable to provide a holding coil for the solenoid that delivers sufficient electromagnetic force to keep the plunger in a closed position while the motor is being cranked. Furthermore, it would be desirable for such a solenoid to be relatively simple in design and inexpensive to implement. SUMMARY

[0015] In accordance with an example, a solenoid for a vehicle starter motor is provided. The solenoid comprises at least one coil with a passage extending through the coil. A plunger is slidably positioned within the passage and is designed to move axially between a first position and a second position. The plunger comprises a substantially cylindrical outer surface section with a circumferential groove formed in the outer surface section.

[0016] In at least one example of the solenoid, the at least one coil comprises a first coil and a second coil, the first coil being axially adjacent to the second coil. The first coil is a pull-in coil, and the second coil is a hold-in coil. The hold-in coil and the pull-in coil are wound around a coil former, and the passage extends through the coil former. A plate element is positioned at one end of the coil former, the plate element being separated from the plunger by a radial distance. The radial distance changes as the plunger moves from the first position to the second position as a result of the movement of the groove relative to the plate element. A sleeve element can be coupled to the plunger such that the sleeve element covers the circumferential groove formed in the plunger.

[0017] In at least one example, a method for operating a solenoid for a vehicle starter motor includes the excitation of at least one coil of the solenoid. The method further includes the movement of a plunger in an axial direction as a consequence of the excitation of the at least one coil. Additionally, the method includes the change in the magnetic reluctance between the plunger and a solenoid wall as a consequence of the plunger's axial movement.

[0018] The features and advantages described above, as well as others, will become more apparent to the person skilled in the art by reference to the following description and the attached drawings. Although it would be desirable to provide a solenoid that incorporates one or more of these or other advantageous features, the teachings disclosed herein extend to those embodiments that fall within the scope of the attached claims, irrespective of whether they achieve one or more of the aforementioned advantages. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic diagram of a vehicle starter motor comprising a motor and a solenoid; Fig. Figure 2 shows a perspective view of a coil former, a pull-in coil, and a holding coil of the solenoid of the Fig. 1 dar; Fig. Figure 3 shows a diagram illustrating lines of magnetic flux through the solenoid when the pull-in coil and the holding coil of the Fig. 2 are excited and the plunger is away from a plunger strike; Fig. Figure 4 shows a diagram illustrating lines of magnetic flux through the solenoid when the pull-in coil and the holding coil of the Fig. 2 are excited and the plunger is in a transition towards the plunger impact; Fig. Figure 5 shows a diagram illustrating lines of magnetic flux through the solenoid when only the holding coil of the Fig. 2 is excited and the plunger is engaged with the plunger strike; Fig. Figure 6 shows a cross-sectional view of the coil former. Fig. 2, which was created along a center line of the coil body; Fig. Figure 6A shows a cross-sectional view of the coil former along line AA. Fig. Figure 6 illustrates one side of a central flange of the coil body; Fig. Figure 6B shows a cross-sectional view of the coil former along line BB. Fig. Figure 6 illustrates another side of the center flange of the coil former; Fig. 6C shows a side view of the coil former along line CC of the Fig. Figure 6 illustrates an end flange of the coil body; Fig. Figure 7 shows a perspective view of an alternative example of the coil body of the Fig. 2 dar; Fig. 8 represents the coil former of the Fig. 7, wherein the holding coil is wound in one direction into a second coil bay of the coil body; Fig. 9 represents the coil body of the Fig. 8, wherein the holding coil is wound in the opposite direction into the second coil bay of the coil body; Fig. 10 represents the coil body of the Fig. 9, wherein the holding coil is completely wound in the second coil bay of the coil body; Fig. 11 represents the coil body of the Fig. 10, wherein the draw-in coil is wound in a first coil bay of the coil body; Fig. 12 represents the coil body of the Fig. 11, wherein the draw-in coil is completely wound in the first coil bay of the coil body; Fig. Figure 13 shows a cross-sectional view of the coil body along line DD. Fig. 12, which includes the holding coil and the draw-in coil, which are positioned on the coil body; Fig. Figure 14 shows a cross-sectional view of an alternative embodiment of the coil former, the holding coil and the draw-in coil of the Fig. 13 dar; Fig. Figure 15 shows a cross-sectional view of the coil former, the pull-in coil and the holding coil of the Fig. 2 in an embodiment according to the invention of a solenoid plunger with a circumferential groove, which is positioned in the inner passage; Fig. Figure 16 presents a graph showing the difference in axial plunger force between a standard plunger and the variable reluctance plunger of the Fig. 15 illustrates the process while the axial plunger gap is being closed; Fig. Figure 17 shows a cross-sectional view of the position of the circumferential groove when the plunger is in position A of the Fig. 16 is located; Fig. Figure 18 shows a cross-sectional view of the position of the circumferential groove when the plunger is in position B of the Fig. 16 is located; Fig. Figure 19 shows a cross-sectional view of the position of the circumferential groove when the plunger is in position C of the Fig. 16 is located; Fig. Figure 20 shows a cross-sectional view of the position of the circumferential groove when the plunger is in position D of the Fig. 16 is located; Fig. Figure 21 shows an isolated side view of the plunger with the circumferential groove of the Fig. 15, wherein a sleeve element is positioned above the circumferential groove; Fig. Figure 21A shows a perspective view of an embodiment of the sleeve element of the Fig. 21 dar; Fig. Figure 21B shows a perspective view of another embodiment of the sleeve element of the Fig. 21 dar; Fig. Figure 22 shows a cross-sectional view of an alternative embodiment of the plunger, coil former, pull-in coil and holding coil of the Fig. 15, wherein the sleeve of the Fig. 21 is positioned on the plunger; and Fig. Figure 23 shows a cutaway view of a conventional starter motor with a soft-start starter motor engagement system. DESCRIPTION General starter motor arrangement

[0019] With reference to Fig. In at least one embodiment, instrument 1 comprises a starting motor 100 for a vehicle, an electric motor 102, and a solenoid 110. Although in Fig. Not shown in Figure 1, the starter motor 100 also includes a drive mechanism and a pinion similar to the conventional starter motor assembly 200, which is described above with reference to Fig. 23 was described. The electric motor 102 in the embodiment of Fig. 1 is positioned in a motor circuit 104, which is designed to connect the motor to the vehicle battery (not shown) via terminal B+. The solenoid 110 is positioned in the motor circuit 104 to enable the connection of the motor to the vehicle battery. The solenoid comprises a pull-in coil 112, a holding coil 114, a plunger 116, and an ignition switch 118.

[0020] The motor circuit 104 of the Fig. The circuit comprises a first current path 106 and a second current path 108, which are designed to supply electrical power to the electric motor 102. The first current path 106 starts at terminal B+, passes through the contacts 119 of the ignition switch 118, continues to node 115, passes through the pull-in coil, and terminates at the input terminal 103 of the electric motor 102. Accordingly, the first current path 106 is only a closed path when the contacts 119 of the ignition switch 118 are closed.

[0021] The second current path 108 begins at terminal B+, passes through the motor contacts 117 associated with the plunger 116, and terminates at the input terminal 103 of the electric motor 102. Accordingly, this second current path 108 is only closed when the plunger 116 has closed the motor contacts 117. When the second current path 108 is closed, the first current path 106 is also short-circuited by the second current path 108, and no current flows through the pull-in coil 112. After the ignition switch 118 closes, the solenoid 110 and the motor 102 work together to provide a soft-start engine engagement system for a vehicle. Axially adjacent coils

[0022] Fig. Figure 2 shows the pull-in coil 112 and the holding coil 114 of the solenoid 110 positioned on a coil former 120 of the solenoid 110. In the embodiment of the Fig. 2. The pull-in coil 112 and the holding coil 114 are adjacent to each other in an axial direction of the coil former 120. The axial direction is in Fig. 2 represented by axis 132.

[0023] The pull-in coil 112 consists of a first length of wire wound around a first section of the coil former 120 to form a first plurality of conductor windings (i.e., turns). The wire for the pull-in coil 112 has a relatively large cross-sectional area such that the resistance of the conductor windings is relatively low. Similarly, the hold-in coil 114 consists of a second length of wire wound around a second section of the coil former to form a second plurality of conductor windings (i.e., turns). The wire for the hold-in coil 114 has a relatively small cross-sectional area such that the resistance of the conductor windings is relatively high.

[0024] The draw-in coil 112 and the holding coil 114 are held side by side on the coil former 120. In the embodiment of the Fig. 2. The coil former 120 is a single component made of a glass-filled nylon material. However, it should be understood that the coil former can alternatively be made of different materials. The coil former 120 can be manufactured using any of the various known processes, such as straight drawing or other forming processes.

[0025] The coil former 120 comprises a first end flange 122, a middle flange 124, a second end flange 126, and a hub 128. The hub 128 of the coil former 120 is generally cylindrical and provides a coil-holding surface for the draw-in coil 112 and the holding coil 114. Although in the embodiment of the Fig. Where a straight circular cylinder is depicted in Figure 1, it is to be understood that the hub 128 may assume other shapes, including cylindrical and non-cylindrical forms. Furthermore, the term "coil body" as used herein refers to any suitable solenoid coil holder, irrespective of whether the hub is provided as a cylinder or whether flanges are included at the ends of the hub.

[0026] The hub 128 in the embodiment of the Fig. 2 extends from the first end flange 122 to the second end flange 126. The hub 128 defines a cylindrical inner passage 130 that extends through the coil former 120 from the first end flange 122 to the second end flange 126. The cylindrical hub 128 also defines a coil former axis 132 that extends through the inner passage 130. The coil former axis 132 defines a centerline for the coil former 120 and an axial direction along the coil former.

[0027] The first end flange 122 provides an end wall for the coil former 120, designed to hold coil windings on the coil former. The first end flange 122 is generally disc-shaped and includes a circular center hole at the inner passage 130 of the coil former. This end wall can be solid with a center hole for the plunger passage 130, as shown in Fig. 2 is shown, or can include several openings. Although the flange 122 is a relatively thin circular disk in the embodiment of the Fig. As shown in Figure 2, it should be understood that the end flange 122 can also be provided in various different shapes and designs.

[0028] The center flange 124 also provides a wall designed to hold coil windings on the coil former. The center flange 124 is positioned on the hub 128 between the first end flange 122 and the second end flange 126, but not necessarily centered between the first end flange 122 and the second end flange 126. In fact, in the embodiment of Fig. 2 is positioned closer to the second end flange 126 than to the first end flange 122. The space between the first end flange 122 and the middle flange 124 provides a first coil bay 142 on the coil body 120, into which the draw-up coil 112 is wound around the hub 128.

[0029] Similar to the first end flange 122, the middle flange 124 in the embodiment of Fig. 2 also disc-shaped. The central flange 124 is generally thicker than the first end flange and includes coil mounting devices 134, such as slots 136 along the outer circumference of the flange 124. These slots 136 provide a passage for cables at the draw-up coil 112. It should be understood that additional coil mounting devices 134 are also possible, and examples of such coil mounting devices are described in more detail below with reference to the Fig. 6-12 explained. Although the center flange in Fig. Figure 2, which is shown with a circular circumference, indicates that the central flange 124 can be provided in various different shapes and designs. For example, although the central flange 124 is shown as solid with a single central opening, the central flange can also have multiple openings.

[0030] The second end flange 126 provides another end wall for the coil former 120, designed to hold coil windings on the coil former. The space between the second end flange 126 and the center flange 124 provides a second coil bay 144 on the coil former, axially adjacent to the first coil bay 142. The holding coil 112 is wound around the hub 128 on the second coil bay 144. Similar to the first end flange 122, the second end flange 126 is also generally disc-shaped and includes a circular center hole at the inner passage 130 of the coil former. The second end flange 126 generally has the same thickness as the first end flange 122. Similar to the middle flange 124, it includes mounting devices 134, such as slots 138 along the outer circumference of the flange 126. These slots 138 provide passage for cables at the pull-in coil 112 and the holding coil 114.The second end flange 126 can be solid, as in . Fig. 2 is shown, or can include several openings. Although the second end flange 126 is shown as a relatively thin, circular disk in the embodiment of the Fig. As shown in Figure 2, it should be understood that the flange 126 can also be provided in various different shapes and designs.

[0031] As previously mentioned with reference to Fig. As described in Figure 2, the coil former 120 of the solenoid 110 is designed such that the pull-in coil 112 is positioned axially adjacent to the holding coil 114 of the solenoid. As a consequence of this adjacent arrangement, a significantly increased flux leakage around the pull-in coil can occur, as shown below with reference to the Fig. As described in Figures 3-5, the increased flux leakage reduces the magnetic force perceived by the plunger as a result of the pull-in coil 112. This allows for a low resistance of the pull-in coil 112 while minimizing the previously described problems of contact interference. Simultaneously, the adjacent coil arrangement ensures minimal flux leakage at the holding coil 114 when the plunger gap is zero and the contacts are closed. This allows for a low number of coil windings in the holding coil while maximizing its holding force.

[0032] The Fig. Figures 3-5 are diagrams illustrating the lines of magnetic flux through the solenoid when the pull-in coil 112 and the holding coil 114 are in various excited and unexcited states. In each of the Fig. Figures 3-5 show the pull-in coil 112, the holding coil 114, the plunger 116, the solenoid housing 150, and the plunger stop 152 as a cross-sectional view of the solenoid, created radially outward from the solenoid centerline 132. The solenoid coil body 120 of the Fig. 2 is in the Fig. Figures 3-5 are not shown for clarity, which allows for a clearer representation of the lines of magnetic flux 170 passing through the solenoid 110. However, it should be understood that the coil former 120 is not shown in the representations of the Fig. 3-5 with the pull-in coil 112 and the holding coil 114, which are wound around the coil body, and the plunger 116, which is inserted into the inner passage 130 of the coil body 120.

[0033] With particular reference to the Fig. 3 The solenoid 110 is received by the solenoid housing 150. The plunger stop 152 is a generally disc-shaped element that is attached to the solenoid housing 150 and extends radially inward from the solenoid housing. The plunger stop 152 includes a cylindrical projection 154 that extends into one end of the inner passage 132 of the coil former 120 (not shown in Fig. 3) fits.

[0034] This cylindrical projection 154 provides a stop surface 154 which is designed to engage with the plunger 116 when the plunger is moved in the axial direction by the pull coil 112.

[0035] The plunger 116 is a solid component with a cylindrical shape. The cylindrical shape of the plunger 116 comprises a first, larger diameter section 160 and a second, smaller diameter section 162. A shoulder 164 is formed between the larger diameter section 160 and the smaller diameter section 162. The plunger 116 is slidably positioned in the solenoid housing 150. In particular, the plunger 116 is designed to slide axially along the centerline 132 to close an air gap 168 (also referred to herein as a "plunger gap") between the plunger shoulder 164 and the stop surface 154 of the plunger stop 152. The plunger 116, the solenoid housing 150 and the plunger stop 152 are all made of a metallic material that has a relatively small magnetic reluctance, so that the magnetic flux lines pass easily through the solenoid housing and the plunger.

[0036] With continued reference to Fig. 3 The pull-in coil 112 of the solenoid 110 is positioned in the solenoid housing 150 and surrounds the larger diameter section 160 of the plunger 116. The pull-in coil 112 is axially separated from the plunger stop by a distance d. An axial end of the pull-in coil is aligned with the shoulder 164 of the plunger 116 when the plunger is in its leftmost position. Fig. 3. As previously explained, the draw-in coil 112 consists of a length of conductor comprising several turns, which are wound around the coil former 120 (in Fig. 3 not shown). When the pull-in coil 112 is initially excited, the plunger 116 is pushed axially to the right, as indicated by the arrow 166.

[0037] The holding coil 114 is positioned axially adjacent to the pull-in coil 112 within the solenoid housing 150. The holding coil 114 surrounds the projection 154 of the plunger stop 152 and the associated stop surface 156. Accordingly, the holding coil 114 also surrounds the smaller diameter section 162 of the plunger that extends through the plunger stop 152. Furthermore, the pull-in coil surrounds the air gap 168 when the plunger is in its leftmost position. Fig. 3. As previously explained, the holding coil 114 consists of a length of a conductor comprising several turns, which are wound around the coil body 120 (in Fig. 3 not shown). When the holding coil 114 is initially excited, the plunger 116 is forced axially to the right, as indicated by the arrow 166. The coil position within the solenoid leads to stray flux.

[0038] As through the river lines 170 in the Fig. 3 and Fig. As shown in Figure 4, when the pull-in coil 112 and the holding coil 114 are energized, a magnetic flux is generated in the solenoid. Leakage flux is any flux that does not contribute to the axial force acting on the plunger 116. The axial force that pulls the plunger 116 toward the plunger stop 152 and closes the plunger gap 168 depends on the total flux linkage between the pull-in coil 112 and the plunger 116, and between the holding coil 114 and the plunger 116. If flux leakage occurs, the flux linkage is reduced, and thus the resulting force on the plunger 116 is also reduced.

[0039] By arranging the draw coil 112 away from the plunger gap 168 and the plunger stop surface 156, as shown in the Fig. 3 and Fig. As shown in Figure 4, the flux dispersion of the pull-in coil 112 is intentionally increased considerably in order to reduce the resulting force on the plunger 116. As shown in the Fig. 3 and Fig. As shown in Figure 4, an increased amount of the flow, rather than flowing directly from the plunger 116 to the plunger stop 152, bypasses the plunger 116 and couples directly from one side of the housing 150 to the stop 152 or even back to the housing 150 outside the wall 151. Examples of this stray flow are shown in Fig. 4 indicated by lines 171. The leakage flux 171 effectively reduces the magnetic force on the plunger 116 for a given ampere-turn excitation of the pull-in coil 112. Since the magnetic force on the plunger 116 is reduced, and since the pinion is mechanically connected to the plunger via the rotating shift lever, the impact force and the steady-state contact force of the pinion against the ring gear are also reduced. Therefore, with the embodiment of the Fig. 1-5 The resistance of the starting coil 112 is made low to increase the soft-start current for the electric motor 102. Accordingly, the torque of the electric motor 102 is increased during the soft start without excessive contact force between the pinion and the ring gear, which conventionally results from the high ampere-turn excitation of the starting coil 112.

[0040] While the coil arrangement in the embodiment of the Fig. While the arrangement is designed to increase the leakage flux for the pull-in coil 112, it is designed to do the opposite for the holding coil 114. In particular, the holding coil 114 is designed in the Fig. The design of the plunger 116 (1-5) minimizes flux leakage with the plunger 116 in order to maximize the electromagnetic holding force on the plunger 116 for a given number of turns of the holding coil 114. This is achieved by centering the holding coil 114 on the contact surface of the plunger stop surface 156. In this way, the leakage flux 171 with the holding coil 114 is minimized and the electromagnetic force on the plunger is maximized. Accordingly, the geometric arrangement of the turns of the pull-in coil 112 and the holding coil 114 makes it possible to transform the force curves of the plunger 116 to values ​​that are more desirable for a starter motor with a soft-start system.

[0041] In addition to the advantages regarding flux dispersion, the arrangement of the pull-in coil 112 and the holding coil 114 side by side can also offer thermal advantages. This is particularly true for conventional windings arranged one above the other, as is the case, for example, in Fig. As shown in Figure 23, the holding coil 214 loses strength when the engagement time between the pinion 206 and the ring gear is prolonged. During prolonged engagement, the engagement coil 212 heats up rapidly and then increases the temperature of the holding coil 214. As the temperature of the holding coil 214 increases, its electrical resistance increases and the current decreases. This reduces the resulting holding force provided by the holding coil, thus increasing the risk of the plunger contacts opening and the plunger disengaging. However, in the side-by-side coil arrangement shown in the starter motor embodiment of the Fig. As shown in Figure 1-5, the thermal influence of the starting coil 112 on the holding coil 114 during starting is minimal, since the resistance of the heat conduction path is much higher when the two coils are separated from each other in the axial direction. Coil body with additional mounting devices

[0042] Now, with reference to the Fig. 6-7 describes an alternative embodiment of the coil former 120 of the Fig. 2 shown. Similar to the coil former of the Fig. 2 The alternative embodiment of the coil former generally also comprises a first end flange 122, a middle flange 124, a second end flange 126, and a hub 128. The hub 128 is generally cylindrical around an axial center line 132, and an inner passage 130 extends through the hub from one end of the coil former 120 to the other. As explained in more detail below, the middle flange 124 and the second end flange 126 in the embodiment of Fig. 6-7, however, a number of additional installation devices 134.

[0043] The Fig. 6A and Fig. Figure 7 shows views of the side of the center flange 124 opposite the first coil bay 142. The center flange 124 incorporates various mounting devices, including a first winding post 172 positioned between an inlet slot 174 and an outlet slot 176. The first winding post 172 extends radially outward from the centerline of the coil former 120 and is designed to engage with the wire of the retaining coil. Sufficient space is provided around the first winding post 172 to allow the retaining coil 114 to be wound around it. Furthermore, the first winding post 172 is sufficiently long to allow the wire of the retaining coil 114 to be wound multiple times around it.As explained in detail below, the first winding post 172 accordingly provides a mounting device 134 that enables secure anchoring of the retaining coil to the coil former 120, and also provides a device for reversing the direction of the windings of the retaining coil 114 on the coil former. A reversing winding post can be advantageous in solenoids for starter motors with a soft-start system, as described in US 8,416,039 B2, filed on April 26, 2010.

[0044] With continued reference to the Fig. 6A and Fig. 7 The inlet slot 174 provides an axial groove in the outer circumference of the central flange 124, which is designed and dimensioned to receive the wire used to form the draw-up coil 112. In addition, in the embodiment of the Fig. 6A and Fig. 7 The inlet slot 174 forms an inlet ramp 175 for the starting cable of the pull-in spool 112. This inlet ramp 175 is designed such that the depth of the slot 174 in the central flange 124 is slightly wedge-shaped and extends towards the hub 128. Accordingly, the inlet slot 174 with the inlet ramp 175 allows the starting cable of the pull-in spool 112 to be guided on the spool body 120 from the circumference of the central flange 124 towards the hub 128 without consuming space in the first spool bay 142 before the starting cable reaches the hub 128. As soon as the starting cable reaches the hub 128, the first layer of windings for the pull-in coil 112 begins. Although the inlet slot 174 is fully disclosed, it is understood that in at least one alternative embodiment the inlet slot extends directly to the hub without the inlet ramp 175 being positioned in the slot 174.

[0045] Similar to the inlet slot 174, the outlet slot 176 provides a further axial groove in the outer circumference of the central flange 124, which is designed and dimensioned to receive the wire used to form the draw-up coil 112. However, unlike the inlet slot 174 in the embodiment of the Fig. In 6A-7, the outlet slot 176 includes a ramp section extending radially towards the hub 128 of the coil former. Instead, the outlet slot 174 is simply provided on the circumference of the center flange 124 and extends radially approximately the thickness of the wire for the draw-up coil to allow the end cable of the draw-up coil to pass transversely over the center flange 124 once the draw-up coil is fully wound into the first coil bay 142.

[0046] With reference to Fig. 6B shows the opposite side of the center flange 124. The side of the center flange 124 that is in Fig. The side shown in Figure 6B is the side facing the second coil bay 144 of the coil former 120. The first winding post 172, the inlet slot 174, and the outlet slot 176 are all visible on this side of the center flange 124. Additionally, this side of the center flange 124 includes an inlet ramp 182 for the initial cable of the holding coil 114. This inlet ramp 182 is similar to the inlet ramp 175 for the draw-in coil and extends in a generally radial direction toward the hub 128, gradually tapering in a wedge shape as it extends toward the hub 128. Furthermore, the side of the center flange 124 shown in Figure 6B includes... Fig. Figure 6B shows a second winding post 178, which is accessible only on this side of the central flange 124. Accordingly, a recess 180 is formed in this side of the central flange 124, and the second winding post 178 is housed in this recess 180. As will be explained in more detail below, this second winding post 178 provides a mounting device for the holding coil 114, which can be used as an armature or as a reverse winding device.

[0047] Now with reference to Fig. 6C includes the second end flange 126 with additional mounting features comprising a double start cable slot 184, a first end cable slot 186, and a second end cable slot 188. The double start cable slot 184 is designed and dimensioned to allow the start cables for both the pull-in coil 112 and the hold-in coil 114 to pass through the circumference of the second end flange 126. When both start cables are positioned in the slot 184, the start cable for the hold-in coil 114 is positioned radially inward from the start cable for the pull-in coil 112. The first end cable slot 186 is designed to allow the end cable for the pull-in coil 112 to pass through the circumference of the second end flange 126. Similarly, the second end cable slot 188 is designed to allow the end cable for the retaining coil 114 to pass through the circumference of the second end flange 126.

[0048] It can be seen that the central flange 124 is thicker in the axial direction than the two end flanges 122 and 126. This increased thickness is a natural consequence of the desired axial separation of the draw-in coil 112 and the holding coil 114, ensuring that the coils are positioned precisely on the coil former 120. The increased thickness also provides more space for the various coil mounting devices 134 integrated into the central flange 124. Without this central flange design, the end flanges 122 and 126 would need to have the same thickness as the central flange to accommodate the same devices, which would reduce the available space for the coil recesses 142 and 144.

[0049] The winding of the draw-in coil 112 and the holding coil 114 onto the coil former 120 is now described with reference to the Fig. 8-12 described to provide a better understanding of the design of the preceding mounting device 134 of the coil former 120 and the arrangement of the coils 112 and 114 on the coil former.

[0050] The process of winding the coil body 120 begins with the holding coil 114. Fig. Figure 8 shows the holding coil 114 as it is wound into the second coil bay 144 of the coil former. To begin the winding process, a starting cable 190 of the holding coil 144 is wound around the first winding post 172 to anchor the wire for the holding coil to the coil former 120. The starting cable 190 is then guided down the entry ramp 182 on the center flange 124 towards the hub 128 (not shown in Figure 8). Fig. 8) After the initial cable 190 reaches the hub 128, the coil former 120 is rotated in the direction of arrow 191, causing a length of wire from a spool (not shown) to be wound around the hub, creating windings for the retaining coil 114. These windings are wound in a first direction of rotation into the second coil bay 144 of the coil former 120.

[0051] As in Fig. As shown in Figure 9, after a predetermined number of turns in the first direction have been produced in the coil bay 144, the length of wire for the holding coil is wound around the first winding post, and the coil former 120 is rotated in the opposite direction, as indicated by arrow 192. The rotation of the coil former in the direction of arrow 192 results in reverse winding turns being produced in a second direction in the second coil bay 144 on the coil former 120. Such reverse winding turns can be advantageous on a holding coil in a vehicle starter motor, as described in US 8,416,039 B2, filed on April 26, 2010.

[0052] Now with reference to Fig. 10. After the reverse winding turns have been produced, the wire for the holding coil is wound around the second winding post 178 on the center flange to securely anchor the holding coil in the second coil bay 144. The end cable 194 of the holding coil is then guided through the second end cable slot 188 on the second end flange 126. The starting cable 190 is also guided through the double starting cable slot 184 on the second end flange 126, thus completing the holding coil 114 on the coil former 120.

[0053] Fig. Figure 11 shows the pull-in coil 112 as it is wound into the first coil bay 142 of the coil former 120, after the holding coil 114 has been wound into the second coil bay 144. To begin winding the pull-in coil, a starter cable 196 of the pull-in coil 144 is guided through the double starter cable slot 184 on the second end flange 126 and through the entry slot 174 on the center flange 124. The starter cable 196 is then guided down the entry ramp 175 on the center flange 124 towards the hub 128. After the initial cable 196 reaches the hub 128, the coil body 120 is rotated in the direction of arrow 197, which causes a length of wire from a spool (not shown) to be wound around the hub and generates winding turns for the draw-in coil 112 in the first coil bay 142 of the coil body 120.

[0054] Now with reference to Fig. 12. After the windings of the draw-up coil 112 are completely wound into the first coil bay 142, the end cable 198 is guided through the exit slot 176 on the center flange 124. The end cable 198 is then guided over the windings of the holding coil 114 and through the first end cable slot 186 on the second end flange 126. This completes the winding of the draw-up coil 112 on the coil former 120. Coil formed from rectangular wire

[0055] Fig. Figure 13 shows a cross-sectional view of the coil body 120 along the line DD of the Fig. 12. In this embodiment of the solenoid 110, the pull-in coil 112 is formed from a rectangular wire 146 (i.e., a wire having a substantially rectangular cross-section), and the retaining coil 114 is formed from a conventional round wire 147. In particular, the rectangular wire 146 used for the pull-in coil 112 is a square wire in the embodiment of Fig. 12 and Fig. 13. The rectangular wire 146 is sheathed with an insulating layer on its outer edge. The wire 146 also includes slightly rounded corners 148, which are provided for manufacturing reasons and to avoid sharp edges on the wire that could cut into the insulating layer of adjacent wires. As explained below, the rectangular wire 146 is advantageous for use in the draw-up coil 112 because it provides an increased stacking factor for the coil while also offering thermal advantages for the coil.

[0056] The stacking factor for a coil is the ratio of the total volume consumed by the conductors alone (i.e., not including the air gaps between the conductors) to the total volume consumed by the complete coil (i.e., including all conductors and air gaps between the conductors). Conventional round wire has an effective stacking factor of about 78%. In contrast, the square wire disclosed herein has an effective stacking factor of 90% or more. In particular, the square wire 146, which in the embodiment of Fig. 12 and Fig. 13 uses a stacking factor of 92%. Consequently, when comparing square wire and round wire, square wire requires less space to provide the same electromagnetic force (i.e., less space to provide the same number of ampere turns). This space saving is particularly useful for vehicle starter motors, where the starter motor is often located in a cramped engine compartment.

[0057] Another advantage of the rectangular wire 146 of the Fig. 12 and Fig. 13 is that it offers a better heat conduction path than round wire for transporting the ohmic heat of the coil 112 to the edges of the coil, where the heat can be removed by conduction or convection. In a coil with round wire, there is only a single point of contact between adjacent windings, since the conductor layers are wound on top of each other (i.e., two adjacent circles touch only at a single point). In contrast, as in Fig. As shown in Figure 13, with a square wire 146, the contact area between the conductors on adjacent windings is much larger because there is contact between adjacent conductors along the entire flat section of the conductor sides. Therefore, the heat transferred from coil wire to coil wire is transported via the copper wire rather than through the air between the wires, and this copper-to-copper conduction provides a significant thermal advantage. For example, the improved conduction reduces the delta temperature difference between the outer edges of the coil and the typically hot spot in the center of the coil.

[0058] Now with reference to Fig. Figure 14 shows a further alternative embodiment of the solenoid coil body 120 and the coils 112, 114. In this embodiment, the pull-in coil 112 is formed from rectangular wire 146, and the hold-in coil 114 is also formed from rectangular wire 149. The rectangular wire 146 of the pull-in coil 112 is essentially the same as the rectangular wire 149 of the hold-in coil, except that the width of the pull-in coil wire 146 is greater than the width of the hold-in coil wire 149. Accordingly, the hold-in coil wire is a square wire with rounded corners. In addition, the rectangular wire 149 is sheathed with an insulating layer on its outer circumference. The rectangular wire 149 of the hold-in coil 114 also offers similar advantages to those described above for the pull-in coil 112. For example, the rectangular wire 149 provides an increased stacking factor for the holding coil 114, while also offering thermal advantages for the coil. Variable reluctance plunger

[0059] In the embodiments described above, the plunger 116 was shown to have a large diameter section 160 and a small diameter section 162, each section having a constant cross-sectional profile (i.e., a constant diameter). However, in at least one embodiment according to the invention, which is described in Fig. As shown in Figure 15, the diameter of the larger diameter section 160 of the plunger 116 is varied such that a radial gap 70 between a guide plate 72 and the plunger 116 changes as the plunger slides in the axial direction. Consequently, the reluctance of the magnetic circuit and the associated magnetic force on the plunger can be adjusted during the pull-in and hold-down phases of operation, as explained in more detail below.

[0060] As in Fig. As shown in Figure 15, the larger diameter section 160 of the plunger 116 comprises a substantially cylindrical surface section 80 with a circumferential groove 82 formed therein. The circumferential groove 82 comprises a central cylindrical section 84 with chamfered edges 86. The diameter of the central cylindrical section 84 of the groove 82 is smaller than the diameter of the remaining substantially cylindrical surface section 80.

[0061] As in Fig. As shown in Figure 15, the groove 82 of the plunger 116 is positioned opposite the guide plate 72. The guide plate 72 generally has a disc-shaped structure that extends radially outwards from the plunger 116. In the embodiment of the Fig. The guide plate 72 is provided as part of the solenoid housing 150 and is integral with the outer wall 151 of the housing 150. The guide plate 72 is positioned adjacent to the end of the coil former 120 that is furthest from the plunger stop 152. Accordingly, the coil former 120 is bounded within the solenoid housing 150 by the guide plate 72 and the plunger stop 152.

[0062] In the embodiment of the Fig. 15 A thin tube 76 is positioned along the inner diameter of the coil former 120 between the plunger 116 and the coil former 120. The tube 76 is fixed relative to the coil former 120 at this position, and the plunger 116 is designed to slide within the tube 76. The tube 76 extends axially over the entire length of the coil former and beyond the guide plate 72. A plunger return spring 78 is positioned on the opposite side of the guide plate 72 from the coil former 120 and engages with both the guide plate 72 and the tube 76. The tube 76 can be made of any of several different materials, such as brass or non-magnetic stainless steel.

[0063] The extension of the tube 76 beyond the guide plate 72 of the solenoid housing 150 serves at least two purposes. First, the extended tube 76 provides a continuous sliding surface for the plunger 116. The continuous surface provided by the tube 76 prevents the edges 86 of the groove 82 from catching on the guide plate 72 during plunger movement when the solenoid coils are activated and deactivated. Second, the extended tube 76 prevents the return spring 78 (which is arranged coaxially with the plunger 116 and rests against the outside of the guide plate 72) from jamming in the groove 82 within the plunger 116 during coil 112 activation. If this were to occur, the plunger 116 would jam against the guide plate 72 of the housing 150.

[0064] The in Fig. The plunger shown in Figure 15 offers a design in which the reluctance of the magnetic circuit and the associated magnetic force on the plunger 116 is variable during the pull-in and holding actuation of the solenoid 110. Fig. Figure 16 provides a graph showing the difference in plunger axial force between a standard plunger (i.e., a plunger without a circumferential groove) and the variable reluctance plunger 116. Fig. Figure 15 illustrates this while the axial plunger gap 168 is closed. In this graph, the upper solid line 60 represents the axial force of the standard plunger with a constant diameter, and the dashed line 62 represents the axial force of the variable reluctance plunger 116 with a circumferential groove 82, such as that of the embodiment of the Fig. 15. The lower solid line 64 in Fig. 16 represents the axial force of the return spring. Between positions A and C, the lower solid line 64 represents the axial force of the return spring, and between positions C and D, the lower solid line 64 represents the axial force of both the return spring and a through-stroke contact spring.

[0065] Four different plunger positions are specifically found in Fig. 16 noted. These four positions comprise the following: Position A at the beginning of the tightening process, in which the axial plunger gap 168 is at a maximum and the tightening coil 112 and the holding coil 114 are initially energized; Position B in the middle of the tightening process, when both the tightening coil 112 and the holding coil are energized; Position C at the end of the tightening process and the beginning of the holding process, in which the plunger 116 has moved to a position where the plunger contacts are closed and the tightening coil 112 is short-circuited; and Position D during the holding process, in which the axial plunger gap 168 is completely closed and only the holding coil 114 is energized.

[0066] With further reference to Fig. 16. The net work done on the plunger during the tightening process is the integral of the net force (magnetic force minus spring force) acting on the plunger over the activation length. This is represented by the area under each of curves 60 and 62 in Fig. Figure 16 shows that this energy is dissipated during the impact between the starter motor drive pinion and the ring gear during the collision.

[0067] The Fig. 17-20 represent a movement of the plunger 116 with circumferential groove 82 at each of the four positions A, B, C and D of the Fig. 16 dar. Fig. Figure 17 represents the plunger in position A, in which the axial plunger gap 168 is at its maximum distance and the pull-in coil 112 and the holding coil 114 are initially energized. In this position A, the groove 82 of the plunger 116 is positioned relative to the guide plate 72. In particular, the guide plate 72 is positioned directly opposite the front chamfered edge 86 of the groove 82 in position A. With the plunger 116 in this position, the radial gap 70 between the plunger 116 and the guide plate 72 is maximized. Because of this large radial gap 70, the resulting magnetic reluctance of the magnetic solenoid circuit is increased. Consequently, the axial force on the plunger 116 is significantly reduced, as can be seen by comparing curves 60 and 62 in Figure 17. Fig. 17 can be observed.

[0068] Fig. Figure 18 represents the plunger in position B, in which the axial plunger gap 168 is closed while the plunger 116 moves toward the plunger stop 152, with both the holding coil 112 and the pull-in coil remaining energized. In this position B, the groove 82 of the plunger 116 remains relative to the guide plate 72. In particular, the guide plate 72 is positioned directly opposite the rear chamfered edge of the groove 82 in position B. With the plunger 116 in this position, the radial gap 70 between the plunger 116 and the guide plate 72 remains maximized. Because of this large radial gap 70, the resulting magnetic reluctance of the magnetic solenoid circuit remains elevated, while the axial force on the plunger 116 is still considerably reduced compared to that of the standard plunger.

[0069] Fig. Figure 19 represents the plunger 116 in position C, in which the axial plunger gap 168 is almost closed and the plunger 116 engages the plunger contacts 117 (see Fig. 1) has moved into a closed position. With the plunger contacts 117 closed, the pull-in coil 112 is short-circuited, as previously described with reference to Fig. As described in section 1. Additionally, in position C, the plunger groove 82 is no longer directly opposite the guide plate 72, but has moved axially past the guide plate 72. With the plunger 116 in this position, the radial gap 70 between the plunger 116 and the guide plate 72 is minimized. Because of this small radial gap 70, the resulting magnetic reluctance of the magnetic solenoid circuit is reduced, which allows the retaining coil 114 to generate the maximum axial force on the plunger 116.

[0070] Fig. Figure 20 represents the plunger in position D, in which the holding coil 114 remains energized and the pull-in coil 112 remains short-circuited. In this position D, the axial plunger gap 168 is completely closed, since the holding coil 114 has moved the plunger 116 into engagement with the plunger stop 152, overcoming the force of both the plunger return spring and the through-stroke contact spring (not shown). Furthermore, in position D, the plunger groove 82 is even further away from the guide plate 72 in the axial direction, so that the radial gap 70 between the plunger 116 and the guide plate 72 remains minimized. Accordingly, in this position D, the holding circuit 114 with the plunger is enabled to generate the maximum axial force on the plunger.

[0071] As above with reference to the Fig. As described in Figures 15-20, the net work during the tightening phase can be reduced by using a variable reluctance plunger, while still fulfilling all the functional requirements of the solenoid. The variable-cross-section plunger ensures a magnetic circuit with variable reluctance, resulting in increased magnetic reluctance during the tightening process (i.e., compare curves 60 and 62 between points A and C in Figure 15-20). Fig. 16) Accordingly, the axial force on the plunger is reduced during the engagement process, thereby reducing the energy dissipated during an impact between the starter motor drive pinion and the ring gear during engagement. Simultaneously, the variable-cross-section plunger ensures a magnetic circuit with variable reluctance, which provides increased (i.e., normal) magnetic reluctance during the holding process (i.e., compare curves 60 and 62 between points C and D in [reference]). Fig. 16). This allows the axial force on the plunger to remain at an increased value during the holding process.

[0072] Although only one embodiment in the Fig. As shown in Figures 15-20, it is to be understood that there are numerous alternative embodiments for the plunger, encompassing many possible alternative geometric configurations that would exhibit the desired magnetic behavior and can be adapted to a given application and requirement. Although the variable reluctance plunger 116 is shown in the Fig. As described in Figures 15-20, in conjunction with a holding coil and a pull-in coil that are axially adjacent, the variable reluctance plunger can also be used in further embodiments in conjunction with a more conventional winding arrangement in which the holding coil is radially adjacent to the pull-in coil (i.e., the holding coil is wound around the pull-in coil), such as the coil arrangement described in Fig. 23 is shown, or vice versa (i.e., where the pull-in coil is wound around the holding coil). Variable reluctance plunger sleeve

[0073] At least one alternative embodiment for the variable reluctance plunger of the Fig. 15 is in the Fig. 21 and Fig. 22 shown. As in Fig. As shown in Figure 21, a cylindrical sleeve 92 is positioned over the circumferential groove 82 on the larger diameter section 160 of the plunger 116. The sleeve 92 is slightly larger in diameter than the plunger 116 and may include chamfered ends 94. Accordingly, the sleeve 92 can serve as a surface contact between the plunger 116 and the tube at this end of the solenoid. In other embodiments, however, the sleeve 92 may be essentially the same diameter as the remainder of the larger diameter section 160 or even slightly smaller in diameter.

[0074] In at least one embodiment, the sleeve 92 is designed as an overmolded plastic sleeve on the plunger 116. In this embodiment, the sleeve 92 is continuously and substantially smooth over its entire outer surface 96, as shown in Fig. Figure 21A is shown. In a further embodiment, the sleeve 92 is a separately molded plastic sleeve that is fitted onto the site via the plunger 116. In this embodiment, the sleeve 92 can include an axial slot 98 to allow the diameter of the sleeve 92 to increase when it is fitted onto the plunger 116 and then to snap back elastically when the sleeve 92 reaches the circumferential groove 82, thus enabling the sleeve 92 to be secured to the plunger 116.

[0075] The sleeve can be made from one of numerous different materials, including, for example, stainless steel or brass. In at least one embodiment, the sleeve is made of polytetrafluoroethylene (PTFE), which is commercially marketed under the name TEFLON®. PTFE provides a low coefficient of friction for the sleeve during plunger movement.

[0076] As in Fig. As shown in Figure 22, the tube 76 must be covered by a sleeve 92 (shown in dashed lines in Figure 22) by covering the circumferential groove 82 on the plunger 116. Fig. 22 (to show their position above the groove 82) do not extend past the guide plate 72 of the solenoid housing 150. This is contrary to the embodiment of the Fig. 15, in which the tube 76 extends completely past the guide plate 72. In Fig. In embodiment 15, the presence of the extended tube necessitates an increase in the radial gap between the plunger 116 and the guide plate 72 to accommodate the tube. This increases the reluctance of the magnetic circuit. This increase in magnetic reluctance does not impair the performance of the solenoid 110 during the tightening process, as, previously described, it can be advantageous to increase the magnetic reluctance during this process. However, this increase in magnetic reluctance can be disadvantageous during the holding process, as, also previously described, it is advantageous to decrease the magnetic reluctance during the holding process to maximize the flux and therefore the axial force of the plunger. This additional radial gap required to accommodate the extended tube 76 is, however, eliminated in the embodiment of Fig.22 eliminated. By reducing the radial gap distance, the reluctance of the magnetic circuit is also reduced. With the reduced magnetic reluctance, the resulting axial force on the plunger during the holding process is increased. During the tightening process, the circumferential groove 82 acts to provide the desired increased reluctance.

[0077] In addition to the aforementioned advantages, the sleeve 92 also eliminates the need for the full plunger diameter to extend beyond a section of the guide plate for vibration reasons, and eliminates the need for grooving in the tube. In particular, the plunger 116 is held by the contact surface between the sleeve 92 and the guide plate 72. Furthermore, this allows the circumferential groove in the plunger 116 to be extended and also reduces the excessive magnetic attraction force, especially in the "rest" position.

[0078] In addition to the problems addressed by the sleeve 92 itself, a PTFE sleeve is particularly helpful in other areas. For example, when the plunger 116 is at rest, a full-diameter section of the plunger should be within the area of ​​the guide plate 72 so that the vibrational force is transferred from the plunger 116 to the guide plate 72. Otherwise, the vibrational force of the plunger 116 against the unsupported, cantilevered tube will cause a groove to form in the thin tube. Over time, this groove and wear will require a high mechanical force to overcome during activation and deactivation and can become large enough to cause a functional defect of the solenoid. A PTFE / stainless steel contact surface is generally superior to a steel / stainless steel contact surface in terms of wear resistance.During vehicle or device use, the plunger is in its "rest" position. As a result of vibrations, the plunger / tube contact surface is constantly subjected to low-amplitude abrasion, where the two parts move relative to each other. This can lead to frictional wear damage. However, if one of the surfaces is made of PTFE, such as the PTFE sleeve 92 described above, the steel-on-steel abrasion is eliminated, minimizing this problem. Additionally, the lubricating properties of PTFE aid during the engagement and disengagement of the solenoid. In particular, PTFE provides a more trouble-free sliding surface that is not damaged by surface corrosion, a problem that can sometimes plague a conventional metal-on-metal assembly.

[0079] The foregoing detailed description of one or more embodiments of the starter motor solenoid with a variable reluctance plunger is presented here only as an example and is not intended to be limiting. Therefore, the meaning and scope of any appended claims should not be limited to the description of the embodiments contained herein.

Claims

[1] Solenoid (110) for a vehicle starter motor (100), wherein the solenoid (110) has: at least one coil (112, 114) with a passage (130) extending through the coil (112, 114); and a plunger (116) movably positioned within the passage (130), wherein the plunger (116) comprises a substantially cylindrical outer surface section (80) with a circumferential groove (82) formed in the outer surface section (80), characterized by , that the plunger (116) is designed to move in an axial direction (166) between a first position (A) and a second position (D), wherein the at least one coil comprises a first coil (112) and a second coil (114), the first coil (112) being adjacent to the second coil (114), the first coil (112) and the second coil (114) being wound around a coil former (120) and the passage (130) extending through the coil former (120), further comprising a guide plate (72) positioned adjacent to an end of the coil former (120), the guide plate (72) being separated from the plunger (116) by a radial gap (70) and the radial gap (70) changing as the plunger (116) moves from the first position (A) to the second position (D) as a result of the movement of the groove (82) relative to the Guide plate (72) moves, with the groove (82) being located directly opposite the guide plate (72),when the plunger (116) is in the first position (A), and wherein the groove (82) is removed from the guide plate (72) in the axial direction (166) when the plunger (116) is in the second position (D), further comprising a tube (76) positioned in the coil former (120), wherein the plunger (116) is positioned inside the tube (76) and is designed to move in the axial direction (166) relative to the tube (76), the tube (76) extending past the guide plate (72) at one end of the coil former (120). [2] Solenoid according to claim 1, wherein the first coil (112) is a pull-in coil and the second coil (114) is a holding coil. [3] Solenoid according to claim 1, wherein the first coil (112) and the second coil (114) are positioned axially adjacent to each other on the coil body (120). [4] Solenoid according to claim 1, wherein the first coil (112) and the second coil (114) are positioned radially adjacent to each other on the coil body (120). [5] Solenoid according to claim 1, further comprising a sleeve element (92) coupled to the plunger (116) and covering the circumferential groove (82) formed in the plunger (116). [6] Solenoid according to claim 5, wherein the sleeve element (92) is formed over the circumferential groove (82). [7] Solenoid according to claim 5, wherein the sleeve element (92) comprises an axial slot (98) designed to allow the sleeve element (92) to expand when the sleeve element (92) is coupled to the plunger (116). [8] Solenoid according to claim 5, wherein the sleeve element (92) comprises chamfered ends (94). [9] Solenoid according to claim 5, wherein the sleeve element (92) has a larger diameter than the cylindrical outer surface section (80) of the plunger (116). [10] Solenoid according to claim 5, wherein the sleeve element (92) is made of polytetrafluoroethylene (PTFE). [11] Solenoid (110) for a vehicle starter motor (100), wherein the solenoid (110) comprises: at least one coil (112, 114) with a passage (130) extending through the coil (112, 114); a plunger (116) which is positioned within the passage (130) and is designed to slide within the passage (130) in an axial direction (166) between a first position (A) and a second position (D); and a guide plate (72) which is separated from the plunger (116) by a radial gap (70), wherein the radial gap (70) changes when the plunger (116) moves from the first position (A) to the second position (D), characterized by a sleeve element (92) that is coupled to the plunger (116) and is positioned in the plunger (116) via a circumferential groove (82), wherein a movement of the circumferential groove (82) past the guide plate (72) changes the radial gap (70) between the guide plate (72) and the plunger (116). [12] Solenoid according to claim 11, wherein the guide plate (72) is positioned at one end of the at least one coil (112, 114), and wherein the at least one coil (112, 114) comprises a pull-in coil and a holding coil.

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