Park lock solenoid

A solenoid for a park lock mechanism wherein an annular frame has a reduced diameter at one end and receives a bobbin with a coil wound thereon with the bobbin projecting outward of the coil at one end and defining an integral bearing positioned in the one end of the annular frame. A magnetic permeable sintered metal bushing is interposed between the integrated bearing of the bobbin and the one end of the annular frame. A plunger is received in the bobbin for sliding movement relative thereto. The plunger has a first reduced section at one end that includes an element for connecting to a shifter and a second reduce section at its other end that projects out of said bobbin. The solenoid has two operating conditions, a first condition in which no magnetic force is applied to the plunger and a connected shifter is locked, and a second condition in which magnetic force is applied to the plunger and a connected shifter is unlocked for shifting. A manual release is provided for coacting with the plunger for putting the solenoid into the second condition in the absence of power.

FIELD OF THE INVENTION

This invention relates to a solenoid, and in particular, to a solenoid for use in a park lock mechanism for an automatic transmission in a vehicle.

BACKGROUND OF THE INVENTION

Solenoids are commonly used to power park lock mechanisms for automatic transmissions for vehicles, especially in an automatic transmission floor shifter to lock the shifter when it is in park. The park lock mechanism prevents the gear selector stick from being moved out of the park position except under certain predetermined conditions. This helps prevent the transmission from being engaged accidentally. Prior art solenoids have complex constructions, which have difficult and costly assembly causing potential quality, reliability and cost issues.

The requirements in the automotive industry for this solenoid are strict as it is considered a safety item. Hence reliability is a major concern. Assembly difficulties are a source of reliability issues. Complex structures increase the cost. Noise is another major customer concern.

Hence there is a desire for a solenoid for use in a park lock mechanism which is easy to assemble, thereby reducing the chance of failure and reducing costs.

SUMMARY OF THE INVENTION

It is a principal object of the present invention to provide a novel park lock solenoid, the construction of which facilitates ease of assembly and compliance to shifter system performance requirements, especially regarding noise.

Accordingly, in one aspect thereof, the present invention provides a solenoid for a park lock mechanism comprising: an annular frame having a reduced diameter at one end; a bobbin with a coil wound thereon with the bobbin projecting outward of the coil at one end and defining an integral bearing; the bobbin received in the annular frame with its integral bearing positioned in said one end of the annular frame; a plunger received in said bobbin for sliding movement relative thereto; said plunger having a first reduced section at one end and a second reduced section at its other end that projects out of said bobbin; said first reduced section including an element for connecting to a shifter; said solenoid having two operating conditions, a first condition in which no magnetic force is applied to the plunger and a connected shifter is locked, and a second condition in which magnetic force is applied to the plunger and a connected shifter is unlocked for shifting, and a spring biases the plunger to place the solenoid in the first condition.

Preferably, a magnetic permeable sintered metal bushing is interposed between the integrated bearing of the bobbin and the one end of the annular frame.

Preferably, a connector housing is provided for the annular frame and solenoid, said connector housing providing a bearing for holding the second reduced section of the plunger.

Preferably, the bobbin supports terminals for connecting the coil to supply leads, the terminals being received in the connector housing.

Preferably, a manual release coacting with the plunger is provided for putting the solenoid into the second condition in the absence of power.

Preferably, the second reduced section of the plunger is provided with a groove and a retaining clip is received in the groove and coacts with the manual release.

Preferably, the manual release is comprised of an L-shaped lever that is pivotally mounted on the solenoid with one leg being the actuating leg and the other leg coacting with the plunger for unlocking the solenoid.

Preferably, a spring integrally formed with the lever, biases the lever to a locked position.

Preferably, a U-shaped magnetically permeable washer is located about one end region of the bobbin adjacent the second end of the annular frame.

Preferably, a bumper coacts with the spring and the plunger to reduce noise and absorb impact.

Preferably, a bumper is mounted on the second reduced section of the plunger to reduce noise and absorb impact as the solenoid returns to the first condition.

Other and further advantages of the present invention will become apparent from the following detailed description of a preferred embodiment of the invention when taken in conjunction with the appended drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1illustrates a preferred solenoid S, a high side-load (3200N) solenoid, according to the present invention for use in a park lock mechanism. The solenoid S provides a movable pin or bolt56which prevents the gear lever, shift or stick, associated with the park lock solenoid, from being moved out of the park position, unless certain conditions are met. The purpose of such a design is to prevent accidental engagement of the transmission.

The solenoid S is shown exploded inFIG. 2to identify the major parts. The solenoid assembly consists of a frame assembly10composed of a frame20and a bushing22; and a coil assembly30composed of a bobbin32, a coil34wound on the bobbin, an integral housing36and terminals38for connecting the coil34to a source of power; a flux ring40; a plunger50; a pair of bumpers62and64; a spring70; a connector housing80; a manual release lever90; and a retaining clip110. The solenoid may include an electrical noise suppression device35fitted to the coil assembly and electrically connected to the terminals.

The frame20, as shown inFIGS. 2,3and4, is a drawn metal can that carries magnetic flux and is a component of the magnetic circuit of the product, as well as, the mechanical structure. One end21of the frame20has a reduced section into which is received a sintered metal bushing22; the frame20locates the bushing22on the center line of the solenoid and with the mounting features of the connector housing80. The other end of the solenoid has retention tabs23to secure the housing to the connector housing80. The frame also serves to locate the wound bobbin/connector assembly30(coil assembly complete).

The bushing22, shown inFIGS. 2,3and4is fitted to the frame20and consists of a powder metal sintered part made of soft magnetic material that facilitates the flow of magnetic flux in the magnetic circuit between the plunger and the frame to achieve the solenoid performance. The i.d. bore of the bushing22locates the bobbin32on the center line of the solenoid. The o.d. of the bushing is a press fit within the one end of the frame21.

The coil assembly is shown in more detail inFIGS. 2,3and5-7. The bobbin32is a one-piece molded plastic part which provides an area for the wound coil34and has channels to route the start and finish wires to the terminals38. The bobbin32also has locating pockets for the terminals, a ledge33for seating a transient voltage device35(an electrical noise suppression device), a slot37for locating the flux ring40, and a reduced section at one end to serve as a molded in one piece bearing39that fits into the bushing22in the one end21of the frame20. To ensure proper interface connection with the customer connector, the bobbin has a connector latch feature41molded in reference to the terminal locating pockets.

The terminals38have a feature to engage the transient voltage suppression device mechanically and electrically. This eliminates the need for soldering this connection. Preferably the feature is a slot42sized to grip the lead wires112of the device as the terminals are pressed into the pockets in the bobbin. The terminals also have a feature, such as post43, for wrapping the start and finish wires44from the coil in a position for welding. The primary blades on the terminals engage the customer's mating connector.

The transient voltage device35(electrical noise suppression device), as shown inFIG. 8, is a discrete component having two lead wires112which are attached to the terminals38as described above. The device35may be a resistor or a varistor type device or other suitable device for suppressing transient voltages due to the coil, which occur when switching on/off the solenoid.

The flux ring40shown inFIGS. 2 and 3has a geometry that is “U” shaped to fit the bobbin so that the start and finish wires can be routed to the terminals through the opening of the flux ring40. The flux ring location, positioned in a slot or recess37molded on the bobbin32has the function of presenting magnetic flux to the plunger50to obtain the correct force. The flux ring is part of the magnetic flux path between the plunger and the frame at the second end of the coil or frame.

The plunger50has a section52of maximum diameter that lies within the coil bobbin32in a slidable manner. The section52is integral with a reduced section53that engages the bobbin bearing39and a reduced shaft section54that engages housing bearing82of the connector housing80, as shown in the sectional view ofFIG. 3. The plunger50has a further step down diameter section56that is the output piece that engages with the customer's shift mechanism. Since the bearing diameter of the plunger section52is larger than the output diameter of section56, deflection of the output does not result in binding of the plunger operation.

The bumpers62and64are resilient annular structures and provide noise dampening for the power on/power off stroke of the plunger50. One bumper62is located between one end of the plunger section52and the bearing39of the bobbin32. The other bumper64is located between the other end of the plunger section52and spring70. The bumper64that engages the spring70is contoured65to align the spring70on the centerline to keep it from making surface sliding noise during cycling.

The spring70has one end bearing against the bumper64pressed against the shoulder defined between sections52and54of plunger50, and its other end bearing against the housing bearing82. Spring70returns the plunger50to its start position when power is removed, and also, slows the actuation force at the end of travel at “power on”, reducing “power on” impact noise.

The connector housing80is crimped to the frame20via the retention tabs23, thus securing all of the internal components in proper alignment and position. Molded integrally in the housing80is the bearing82for holding the shaft section54of plunger50, the connector cover that features easy access for the mating connector, a protective pocket for the transient voltage suppression device35and the mounting feature for the manual release lever90.

The manual release lever90provides the function of moving the plunger manually to release the park lock mechanism when there is no battery power available. The lever90consists of a pivotally mounted, L-shaped finger activated lever92, pivotally mounted to the connector housing80via pins93, as shown inFIGS. 1 and 2. Lever92is movable against spring94attached to the top of lever92and bearing against a plate84on the bottom of the connector housing80, as shown inFIG. 3. The bifurcated top of up leg95of the lever is received around the projecting end of shaft section54. A retaining clip110engages a groove55in the projecting end of shaft section54and holds up leg95around the shaft. When the manual release lever92is pressed towards the connector housing, it pivots about pins93and up leg95of the manual release lever pushes the clip/shaft/plunger outwardly of the connector housing, to the right, as shown inFIG. 3, to release the park lock mechanism. The clip110is a low cost commodity component that enables avoiding tooling a plastic part. Spring94returns the lever to the power off position after manually releasing the lock. Spring94may be a separate component but is preferably formed intergrally with the lever as a monolithic construction.

Lubricant is applied to the plunger to dampen noise during the power on/power off cycle as well as to keep sliding friction low.

The operation of the solenoid is as follows. When power is applied to the connector terminals38the solenoid coil34is energized producing a magnetic field that interacts with the plunger50. The plunger50moves to the equilibrium position of the magnetic field. When power is removed, the magnetic field collapses and the spring70pushes the plunger50back to its original position. In the application, the solenoid in the power off position blocks the motion of the shift lever. When the solenoid is powered on, the park lock mechanism is released so that the shift lever can be moved to one of the transmission gear positions.

The invention as described above, gives certain advantages and improvements in performance. These include better sound quality performance, better retention of manual override feature, one-piece drawn-can construction, enhanced assembly due to lead-in's on drawn can housing, better physical protection for the EMC device and more reliable interference fit connection (eliminating any use of solder), optimized magnetic circuit for low cost (eliminating any permanent magnet), and integrated bearing design in the bobbin eliminating any separate sleeve bearings.