DE102020125886A1 - Parking lock for locking a transmission, in particular a motor vehicle transmission, and transmission - Google Patents

Abstract

The present invention relates to a parking lock (1) for locking a transmission, in particular a transmission of a motor vehicle, having a piston (30) for mechanically locking the transmission, a piston housing (50) in which the piston (30) moves along a longitudinal axis (X ) is movably arranged, a pressure chamber (40) into which a pressure medium for moving the piston (30) can be introduced, an electromagnetic actuator (10) with a movable armature tappet which is used to lock or release the piston (30) with the piston ( 30), the piston housing (50) being made of a plastic or a fiber-reinforced plastic, the piston housing (50) having an introduction opening through which the pressure medium can be introduced into the pressure chamber, and a pressure-limiting valve (60) in the Piston housing is provided. The present invention also relates to a transmission with a parking lock (1).

Description

The present invention relates to a parking lock for locking a transmission, in particular for locking an automatic transmission of a motor vehicle, having the features of patent claim 1 and a transmission having the features of patent claim 15.

Parking locks are already known from the prior art in different configurations, for example from WO 2020 119 980 A1 or DE 10 2019 114 563 A1 , And usually serve to actuate a mechanically acting locking device, through which the transmission of a motor vehicle, in particular the automatic transmission of a motor vehicle can be blocked. For this purpose, the parking lock can be positioned in a first position that releases the transmission and a second position that blocks the transmission, in which, for example, a pawl or a bolt engages a ratchet wheel of the automatic transmission and thus mechanically blocks the automatic transmission in a parking position.

Electrohydraulic parking locks are proposed for actuating the previously known parking locks, which are characterized in that the parking lock is pretensioned, for example by means of a spring accumulator, and the parking lock can be unlocked by means of a hydraulically actuated piston via a pressure medium, usually hydraulic oil. In this case, a locking device that can be actuated by an electromagnetically operated actuator is regularly provided, by means of which an unintentional actuation of the parking lock is prevented.

The prior art has proven to be problematic in that the previously known parking locks have a considerable weight. A piston housing, which houses a pressure chamber for the pressure medium to actuate a piston, is typically made of a metallic material in order to be able to absorb pressure peaks of up to 150 bar. These piston housings contribute significantly to the total weight of the parking lock. Recent developments with a piston housing made of a plastic have to be reinforced in a complex manner, which is why additional installation space is required.

This is where the present invention comes in.

It is the object of the present invention to provide a parking lock that is improved in an expedient manner in order to eliminate the disadvantages known from the prior art. Compared to previously known parking locks, the parking lock should have a lighter and more compact design and reduce the manufacturing costs. Furthermore, it is sought that a switching time of the parking lock should be adjustable independently of the operating temperature or the viscosity of the pressure medium.

These tasks are solved by a parking lock with the features of patent claim 1 and by a transmission with the features of patent claim 15 .

Further advantageous refinements of the invention are specified in the dependent claims.

The parking lock according to the invention with the features of claim 1 for locking a transmission, in particular a transmission or automatic transmission of a motor vehicle, has a piston for mechanically locking the transmission, a piston housing in which the piston is arranged so that it can move along a longitudinal axis, and a pressure chamber in which a pressure medium for moving the piston can be maintained. In addition, the parking lock according to the invention has an electromagnetic actuator with a movable armature tappet, which can interact with the piston to lock or release the piston, the electromagnetic actuator preferably being able to positively fix the piston in a first position and in a second position via a locking device . Furthermore, the invention provides that the piston housing is made of a plastic or a fiber-reinforced plastic, the piston housing having an introduction opening through which the pressure medium can be introduced into the pressure chamber and a pressure-limiting valve being arranged in the piston housing, through which the pressure in the Pressure space can be limited.

The present invention is based on the idea of limiting the maximum pressure in the pressure chamber of the parking lock, as a result of which pressure peaks are reduced. Due to the prevention of pressure peaks in the pressure chamber, thickening of a wall of the piston housing or ribbing of the piston housing for reinforcement can be dispensed with. Instead of a metallic material, a plastic can thus be used and, moreover, this can be designed with particularly thin walls. In particular, it is preferred if the piston housing is produced in an injection molding process, in which case the thin-walled design further optimizes the production process and high internal stresses within the wall can be prevented. Due to the thin-walled design, the customer's installation space conditions can be better met. In connection with this invention, under a pressure relief valve, a return be understood. In the simplest case, the pressure-limiting valve can have a blocking element that releases the outlet when a predetermined pressure is exceeded and can at least partially or completely close the outlet again below the predetermined pressure.

A preferred development of the present invention provides that the pressure chamber is completely enclosed by the piston housing and the piston. The pressure forces acting in the pressure chamber thus act exclusively on the piston housing and the piston and the seals arranged between the piston housing and the piston, while the remaining components of the parking lock remain essentially unloaded by the forces acting in the pressure chamber.

According to a development of the present invention, the pressure-limiting valve is arranged in the piston housing between the introduction opening or the pressure chamber and an outlet. The outlet can lead the pressure medium back into a pressure medium circuit, the pressure-limiting valve being arranged in the connection between the introduction opening and the outlet. The pressure-limiting valve is configured, when a predetermined pressure in the pressure chamber and/or the introduction opening is exceeded, to open an annular channel or channel and to release pressure medium into the outlet to lower the pressure. The pressure valve is preferably designed in such a way that the pressure in the pressure chamber is limited immediately after the end position of the piston has been reached, ie when the parking lock is in the position that blocks a transmission. In this case, both the pressure-limiting valve and the outlet can be arranged in such a way that a connection between the pressure medium in the pressure chamber and the pressure-limiting valve can only be established shortly before the end position of the piston is reached.

According to a further preferred embodiment of the present invention, the pressure-limiting valve is arranged in a recess which is aligned parallel to the longitudinal axis. After the piston housing has been produced, the pressure-limiting valve can be inserted into the recess, it being possible for the recess to be reworked in order to fasten the pressure-limiting valve. This arrangement of the pressure-limiting valve has production-related advantages in particular, since no additional slides have to be provided during the casting process. This development also contributes to a compact and slim design of the parking lock.

In addition, it has also proven to be advantageous if a valve seat for the pressure-limiting valve is formed through the piston housing, in particular in the recess. The valve seat is configured to cooperate with a closing element, described in detail later, wherein the closing element can bear sealingly against the valve seat. For this purpose, the valve seat can be adapted to the shape of the valve element and can, for example, be conical or spherical.

Furthermore, it is advantageous if the pressure-limiting valve is positively and/or cohesively fixed in the piston housing and/or the pressure-limiting valve is screwed or pressed into the piston housing. It is preferred if the pressure-limiting valve is designed as a simple check valve, consisting of a closing element, a closing element cage, a spring, a spring guide and a securing element. The securing element can be a securing ring, for example, which can be inserted in particular into a groove in the plastic housing, and the spring arranged between the spring guide and the ball cage, as well as the ball, press against the valve seat, with the spring tension of the spring determining an opening pressure of the pressure relief valve and thus also approximately the maximum pressure of the pressure medium present in the pressure chamber. The securing element can also be pressed or screwed into the recess or fixed in some other way.

According to a preferred embodiment, the pressure-limiting valve can be arranged in a form-fitting manner in the piston housing and, for example, overmolded during injection molding, as a result of which the manufacturing process can be further simplified.

Furthermore, it has proven to be advantageous if the closing element of the pressure-limiting valve is spherical or conical. The conical configuration of the closing element results in an improved opening and closing behavior of the pressure-limiting valve.

A development of the present invention provides that a leakage channel is arranged between the introduction opening and the outlet. The leakage channel is intended to provide a constant leakage path between the introduction opening and the outlet, as a result of which pressure medium is routed past the pressure chamber in the manner of a bypass. The leakage channel is intended to compare the switching time of the parking lock. Since the viscosity of the pressure medium is typically strongly dependent on the temperature of the pressure medium, the leakage channel has less of an effect when the pressure medium is viscous (i.e. cold) than when it is thin (warm pressure with phone). Thus, the switching time of the parking lock is extended with low-viscosity oil, while the switching time is reduced with high-viscosity oil.

According to a preferred embodiment of the present invention, the leakage channel is arranged in the pressure-limiting valve, with the leakage channel particularly preferably being arranged between the closing element and the valve seat. For example, the leakage channel can be created by appropriately shaping the valve seat or the closing element, with the shape of the valve seat not corresponding to the shape of the closing element in the area of the leakage channel and the closing element consequently not lying against the valve seat in this area. In this exemplary embodiment, the leakage channel can preferably be formed by a recess in the valve seat, which can already be formed during manufacture of the piston housing and thus means no additional effort in the manufacturing process.

A development of the present invention provides that the pressure-limiting valve is formed from a leaf spring. In particular, it is preferred if the leaf spring is made from a memory alloy and the leaf spring forms both the spring element and the closing element of the pressure-limiting valve. The leaf spring can already be arranged in the piston housing in a simple manner during the injection molding of the piston housing, resulting in a particularly effective manufacturing process.

In accordance with a preferred development of the present invention, the piston is designed to be hollow at least in certain areas, resulting in weight advantages. The piston can be formed from a number of components, with the mechanically highly stressed components, in particular a round piston pressure piece which interacts with the electromagnetic actuator, being able to be made from a metallic material.

A further development of the present invention provides that the pressure chamber is sealed off from the piston and the housing by means of seals, with a piston seal preferably being provided at one end on the piston that is movable in the longitudinal axis, and a lip seal sealing the pressure chamber at the other end between the piston and the Piston housing sealed.

The piston housing preferably has a circumferential collar which projects inwards in the direction of the longitudinal axis and on which the seal is arranged. The circumferential collar reduces the seal diameter and minimizes the forces acting on the seal. The seal is firmly connected to the piston housing, which is why pressure forces in the pressure chamber only act on the piston housing and the piston, but not on the electromagnetic actuator or the locking device.

In order to achieve a good seal, the seal can be a rod seal, in particular a lip seal. According to a further development, the seal can be arranged between a circumferential collar projecting from the piston housing towards the longitudinal axis and an outer wall of the piston pressure piece. The seal between the piston and the inside of the wall of the housing of the parking lock can be implemented by a conventional piston seal, for example by an O-ring located between the outside wall of the piston and the inside of the wall of the piston housing of the parking lock. The circumferential collar reduces the effective diameter in which the seal is arranged, as a result of which lower compressive forces act on the seal.

The armature tappet can also use the locking device to fix the piston in a first position and a second position, with the locking device comprising the latching link with two latching recesses which are arranged on the piston at a distance from one another along the longitudinal axis and the first position of the piston and the second position of the specify pistons. A blocking element can engage in the latching recesses, which is preferably carried along by the piston in the manner of a cage and can engage in the latching slot to form a form fit. The form fit can be canceled by actuating the electromagnetic actuator. The armature plunger can hold the blocking element in the respective latching recess via a respective expansion cone in the manner of a trap, wherein when the electromagnetic actuator is actuated, the expansion cone is displaced relative to the latching recess so that the blocking element can emerge from the latching recess.

According to a further preferred embodiment of the present invention, a wall of the piston housing or the wall of the pressure chamber is thin-walled and has a wall thickness t, the wall thickness t preferably being less than 5 mm, more preferably approx. 4 mm or no greater than 4 mm . In particular, it is preferred if the piston housing is made of a plastic or a fiber-reinforced plastic, in particular by injection molding.

A further aspect of the present invention relates to a transmission with a parking lock as described above.

• 1 eine Seitenansicht einer erfindungsgemäßen Parksperre, und
• 2 eine Schnittdarstellung der Parksperre gemäß 1 durch die Schnittlinie A - A,
• 3 eine Schnittdarstellung der Parksperre gemäß 1 durch die Schnittlinie B - B, und
• 4 eine vergrößerte und vereinfachte Darstellung des Details gemäß 3.

An exemplary embodiment of a parking lock according to the invention for locking a transmission, in particular a transmission of a motor vehicle, is described in detail below with reference to the accompanying drawing. Show it

• 1 a side view of a parking lock according to the invention, and
• 2 according to a sectional view of the parking lock 1 through the intersection line A - A,
• 3 according to a sectional view of the parking lock 1 through the line of intersection B - B, and
• 4 an enlarged and simplified representation of the detail according to 3 .

Identical or functionally identical components are identified below in the one exemplary embodiment with the same reference symbols. For the sake of clarity, not all identical or functionally identical parts are provided with a reference number in the individual figures.

1 shows a side view of a parking lock 1 according to the invention for fixing a (not shown) transmission by means of a piston rod, in particular an automatic transmission (not shown) of a motor vehicle (not shown).

The parking lock 1 includes according to the 2 and 3 an electromagnetic actuator 10, a locking device 20 (not shown in detail), a piston 30 and a piston housing 50. The parking lock 1 has a longitudinal axis X, with the piston 30 in the piston housing 50 along the longitudinal axis X being movable.

The piston housing 50 includes a wall 52 and is made of a plastic or a fiber-reinforced plastic with a wall thickness t, preferably by injection molding. The piston housing 50 also has a through opening 56 which extends between a first end area and a second end area. In the first end area of the piston housing 50, the piston housing 50 is connected to the electromagnetic actuator 10, while the piston 30 protrudes from the second end area through an opening. In the second end region, the piston housing 50 can have a housing cover 55 which is preferably connected to the piston housing 50 in a positive and/or non-positive manner.

In the through-opening 56 the piston 30 is arranged such that it can lift, which can be designed in several parts with a piston center part, a piston rod 32 , a piston pressure piece and a piston seal 35 . The piston pressure piece, the piston middle part and the piston rod 32 can be fixedly connected, whereby the piston pressure piece and/or the piston rod 32 can be made of a metallic material, while the piston middle part can be made of a plastic or fiber-reinforced plastic.

The piston 30 can be designed at least in sections as a hollow cylinder or hollow and also has a piston seal 35 on a lateral surface facing the piston housing 50, which can be formed from an O-ring, for example.

The pressure chamber 40 is arranged in the piston housing 50 and is enclosed by the piston housing 50 or its thin-walled wall 52 and the piston 30 . A pressure medium (not shown), preferably hydraulic oil, for moving or displacing the piston 30 along the longitudinal axis X from a first position, shown in FIGS 2 and 3 , Are introduced into a second (not shown) position. The piston 30 can be moved back into the first position (initial position) in the opposite direction by the return spring 38 , the pressure medium being displaced from the pressure chamber 40 . The introduction opening 42 can be connected to a hydraulic circuit (not shown) of a motor vehicle, it being possible for the pressure medium to be introduced into the pressure chamber 40 under pressure through the introduction opening 42 .

The wall thickness t of the wall 52 in the region of the pressure chamber 40 is preferably t≦6 mm, more preferably t≦5 mm and even more preferably t≦4 mm.

The introduction opening 42 is formed by a line channel 43 which extends from a connection into the piston housing 50 in the manner of a blind hole. The line channel 43 is arranged secantly to the longitudinal axis X or at a distance from the pressure chamber 40 along a first straight line. Furthermore, from the 2 and 3 it can be seen that an outlet 44 is provided. The outlet 44 is formed by a recess 45 which is also designed in the manner of a blind hole and which can be arranged parallel and at a distance from the longitudinal axis X and furthermore along a second straight line. The line channel 43 and the recess 45 cross or intersect at an angle α, the following preferably applying to the angle α: 0<α<180, more preferably 45≦α≦135 and even more preferably 70≦α≦110.

However, the first straight line and the second straight line can intersect at an intersection point it can be advantageous, as in the illustrated embodiment, if the straight lines have no point of intersection. The recess 45 extends from an open end to the duct 43 and opens into it. Thus, the outlet 44 and the duct 43 are in communication.

In the recess 45 there is also an opening 47 through which the recess 45 is connected to the pressure chamber 40 . The pressure medium can thus reach the pressure chamber 40 through the connection via the line channel 43 and the recess 45 .

Between the open end of the blind hole-like recess 45 and the opening 47, the pressure relief valve 60 is arranged, through which the pressure medium can be discharged through the outlet 44 when a high pressure is present.

The pressure-limiting valve 60 can be designed as a non-return valve and, according to the enlarged view in 4 a securing element 62, a spring guide 64, a spring element 65, a closing element cage 66 and a closing element 68.

As in the exemplary embodiment shown, the securing element 62 can be designed as a securing ring and engages in a groove worked into the recess 45 . The spring element 65 is supported on the securing element 62 by means of the spring guide 64 and presses the closing element cage 66 and the closing element 68 against a valve seat 69 which is formed in the recess 45 through the piston housing 50 .

The pressure chamber 40 is enclosed radially with respect to the longitudinal axis X by the piston housing 50 and the piston 30 . The pressure chamber 40 is closed on the opposite sides along the longitudinal axis X by means of a piston seal on the piston 30 and by means of a seal. The seal can be arranged on a peripheral collar 58 protruding from the piston housing 50 in the through opening 56 and is preferably designed as a lip seal.

The electromagnetic actuator 10 is designed and set up in the manner of a single lifting magnet, the piston 30 by means of the locking device 20 in the first position - see 1 - and to lock in the second position. The locking device 20 allows blocking elements (not shown) to form a form fit between the piston and a locking link, by means of which the piston can be fixed in its position. In order to release this form fit, the electromagnetic actuator 10 can be energized, as a result of which the form fit is canceled and the piston can be displaced in the longitudinal axis X.

Reference List

1

parking lock

10

actuator

20

locking device

30

Pistons

32

piston rod

35

piston seal

38

return spring

40

pressure room

42

insertion opening

43

conduit

44

outlet

45

recess

47

breakthrough

50

piston housing

52

wall

55

housing cover

56

passage opening

58

Federation

60

pressure relief valve

62

fuse element

64

leadership

65

spring element

66

locking element cage

68

closing element

69

valve seat

t

Wall thickness

X

longitudinal axis

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2020119980 A1 [0002]
• DE 102019114563 A1 [0002]

Claims (15)

Having a parking lock (1) for locking a transmission, in particular a transmission of a motor vehicle - a piston (30) for mechanical locking of the gearbox, - a piston housing (50) in which the piston (30) is arranged to be movable along a longitudinal axis (X), - a pressure chamber (40) into which a pressure medium for moving the piston (30) can be introduced, - an electromagnetic actuator (10) with a movable armature tappet, which can interact with the piston (30) to lock or release the piston (30), - wherein the piston housing (50) is made of a plastic or a fiber-reinforced plastic, - Wherein the piston housing (50) has an introduction opening through which the pressure medium can be introduced into the pressure chamber, and - wherein a pressure relief valve (60) is provided in the piston housing. Parking lock (1) after claim 1 , characterized in that the pressure chamber (40) is enclosed by the piston housing (50) and the piston (30). Parking lock (1) after claim 1 or 2 , characterized in that the pressure-limiting valve (60) is arranged in the piston housing (50) between the introduction opening (42) or the pressure chamber (40) and an outlet (44). Parking lock (1) after one of Claims 1 until 3 , characterized in that the pressure relief valve (60) is arranged in a recess (45) which is arranged parallel to the longitudinal axis (X). Parking lock (1) according to one of the preceding claims, characterized in that a valve seat (69) for the pressure-limiting valve (60) is formed from the piston housing (50). Parking lock (1) according to one of the preceding claims, characterized in that the pressure-limiting valve (60) is fixed in the piston housing (50) in a positive and/or cohesive manner and/or that the pressure-limiting valve (60) is screwed into the piston housing (50) or is pressed in. Parking lock (1) according to one of the preceding claims, characterized in that a closing element (68) of the pressure-limiting valve (60) is spherical or conical. Parking lock (1) according to one of the preceding claims, characterized in that a leakage channel is formed between the insertion opening (42) and an outlet (44). Parking lock (1) after claim 8 , characterized in that the leakage channel is arranged in the pressure relief valve (60). Parking lock (1) according to one of the preceding claims, characterized in that the pressure-limiting valve (60) is formed from a leaf spring. Parking lock (1) according to one of the preceding claims, characterized in that the piston (30) is hollow at least in certain areas. Parking lock (1) according to one of the preceding claims, characterized in that the piston (30) is sealed off from the piston housing (50) by means of at least one seal, in particular a lip seal. Parking lock (1) according to one of the preceding claims, characterized in that the anchor tappet can fix the piston (30) in a first position and a second position in the longitudinal axis (X) via a locking device (20). Parking lock (1) according to one of the preceding claims, characterized in that a wall (52) of the piston housing (50) is thin-walled, in particular has a wall thickness t of less than 5mm, preferably approximately 4mm. Transmission with a parking lock (1) according to one of the preceding claims.

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