Patent Application
20230174211
This application claims priority to German patent application 10 2021 213 912.4, filed Dec. 7, 2021, which is hereby incorporated by reference in its entirety.
The present invention relates to a hydraulic trim device for a boat motor, a boat motor comprising such a trim device, and a boat comprising such a boat motor. Such boat motors regularly comprise a boat drive, for example an outboard motor or a stern drive. The boat drive is pivotably arranged on the hull of the boat by means of the trim device.
Such hydraulic trim devices for boat motors are known from the prior art, for example from U.S. Pat. No. 5,597,333 A or WO 01/98142 A. Usually, these hydraulic trim systems are used in combination with a hydraulic lift device. These combined devices are used on the one hand to pivot the boat drive, for example an outboard motor, via at least one lift cylinder of the lift device into a rest position in which the propeller of the drive is almost completely or fully lifted out of the water.
Further, at least one trimming cylinder of the trim device is used to perform a so-called power trim while the boat is travelling. Here, the boat drive is finely adjusted by rotation around the transverse axis of the boat in order to obtain an optimum alignment or position of the hull of the boat with respect to the water surface during travel. A suboptimal alignment between the hull and the water surface results in a loss of propulsion due to cavitation of the propeller as well as incorrect power input direction, unsteady handling and increased fuel consumption.
For this purpose, the hydraulic trim device has, in addition to the at least one trimming cylinder, a hydraulic unit and a trimming plate. The trimming cylinder comprises a piston rod axially movable in the trimming cylinder between a first end position and a second end position. In sense of the present invention, the first end position may correspond to a minimum trim position, which position may also correspond to the fully retracted position of the piston rod. The second end position may correspond to a maximum trim position, whereby this may correspond to a fully extended position of the piston rod. To extend the piston rod in the direction of the second end position, the trimming cylinder is pressurized in a known manner via the hydraulic unit.
The piston rod has a contact portion which is in contact with a contact surface of the trimming plate. The trimming plate is disposed on the boat drive so that the boat drive is pivoted relative to the hull by extending and retracting the piston rod. When the piston rod moves between the first end position and the second end position, the contact portion moves relative to the contact surface along the contact surface.
In known trim devices, the movement between the contact portion and the contact surface can result in transverse forces that increase wear, for example on guide bushings of the trimming cylinder. In particular, the friction between the contact portion and the contact surface also causes the piston rod to stop and move alternately, which is also noticeable in the form of vibrations. This phenomenon is also referred to as the slip-stick effect. As a result, there is also an undesirable noise formation, which manifests itself as a kind of rattling. As a general remedy, it is suggested that the contact surface or contact portion be lubricated regularly, which also has a positive effect on the wear between the contact surface and contact portion.
In addition, U.S. Pat. No. 5,597,333 A suggests that the trimming plate may be in the nature of a ball bearing, or that the contact surface may be symmetrically concavely curved, i.e., curved inward away from the contact portion.
The disadvantage of this is that the solution in the form of a ball bearing is very complex and therefore expensive to manufacture. The solution with concavely curved contact surfaces also only works satisfactorily with regular application of lubricant, whereby the transverse forces are even higher, depending on the position of the piston rod, than with a completely flat contact surface. Increased use of lubricant is also undesirable for ecological reasons, as a considerable proportion of the lubricant is discharged into the waterways due to its aquatic use in boat motors.
It is therefore the object of the present invention to provide a hydraulic trim device for a boat motor, with which the undesirable transverse forces as well as the undesirable noise development can be effectively prevented with reduced use of lubricant. The solution of the problem is achieved with a hydraulic trim device as disclosed herein. Preferable embodiments are also described.
The hydraulic trim device according to the invention is characterized over the trim devices known in the prior art in that the contact surface at least partially has a convex curvature in the direction of the piston rod. In other words, the contact surface at least partially curved outwardly in the direction of the piston rod or the contact portion. In this way, it can be ensured that the transverse force is significantly minimized, whereby the use of lubricant can also be noticeably reduced. Tests by the applicant have shown that, compared with conventional trim devices with flat contact surfaces, up to five times the number of movements can be achieved with the same use of lubricant.
Preferably, the contact portion is in a first contact position in the first end position of the piston rod and in a second contact position in the second end position of the piston rod. Preferably, the convex curvature of the contact surface between the first contact position and the second contact position is asymmetrical. In other words, the trimming plate is thus symmetrical along a first imaginary plane between the first end position and the second end position, but asymmetrical along a second plane perpendicular to the first plane. Thus, the trimming plate can be individually matched to the corresponding kinematics of the boat drive with respect to trim or power trim.
Preferably, the contact surface between the first contact position and the second contact position has a completely convex curvature in the direction of the piston rod. This means that the contact surface is not only convexly curved partially or in sections, but completely.
Preferably, the piston rod has a central mid-axis, the convex curvature of the contact surface being such that the central mid-axis of the piston rod in any position of the piston rod between the first end position and the second end position is orthogonal on the trimming plate or contact surface or is inclined by at most 6° on the trimming plate or contact surface. If the central mid-axis of the piston rod is inclined on the trimming plate or the contact surface, it is useful if the central mid-axis is inclined between 1.5° and 4.5°, preferably by 2° to 4° and particularly preferably by 3° on the trimming plate or the contact surface. A completely orthogonal arrangement results in the lowest transverse forces and consequently the lowest wear. With a certain inclination, the slip-stick effect can be largely suppressed, with tests by the applicant showing that the best compromise between reduced transverse forces and reduced slip-stick effect can be achieved at an inclination of 3°.
Preferably, the central mid-axis is inclined in the direction of the first contact position. By inclining the central mid-axis in the direction of the first contact position, the slip-stick effect is noticeably reduced, especially when the piston rod is extended.
Preferably, the contact portion is a spherical contact portion. This results in point contact between the contact portion and the contact surface. Alternatively, the contact portion can be a planar contact portion. This results in a line contact, which reduces the surface pressure. Furthermore, a flat contact portion is easy to manufacture. Of course, other shapes of the contact portion are also conceivable, for example semi-cylindrical, partially cylindrical or frustoconical.
Furthermore, the solution of the problem is achieved with a boat motor disclosed herein. According to the invention, the boat motor comprises a trim device described above as well as a boat drive. The trimming plate is attached to the boat drive. The boat drive may in particular be an outboard motor or a stern drive.
Furthermore, the solution of the task succeeds with a boat, in particular a sports boat. The boat according to the invention has a hull and a boat motor described above, the boat drive being pivotably arranged on the hull by means of the hydraulic trim device.
In the following, the invention is explained in more detail with reference to exemplary embodiments shown in the figures. The figures show schematically:
In
The hydraulic trim lift device 110 has a lift cylinder 106 and, in this embodiment, a trimming cylinder 2 as part of the hydraulic trim device 1. Of course, embodiments with two or more lift cylinders and with two or more trimming cylinders are also conceivable. Furthermore, a hydraulic unit (not shown in more detail) is provided, via which the lift cylinder 106 and the trimming cylinder 2 can be pressurized in a known manner.
The trimming cylinder 2 has a piston rod 3 which can be moved axially between a first end position EP1 and a second end position EP2 in the trimming cylinder 2, see also
During power trimming while the boat 101 is travelling, the trimming cylinder 2 extends and the contact portion 4, 4′ of the piston rod 3 of the trimming cylinder 2 moves along the contact surface 6 of the trimming plate 5 to pivot the outboard motor 105 relative to the hull 102 along the joint 103 about the transverse axis of the boat 101 to fine-tune between the lowered position (
In
In this embodiment, the contact portion 4 of the piston rod 3 is spherical, so that there is point contact between the contact portion 4 and the contact surface 6. As shown, the contact surface 6 of the trimming plate 5 has a convex curvature in the direction of the piston rod 3 or the contact portion 4, as will be described in more detail below.
To perform a power trim, the trimming cylinder 2 is pressurized by the hydraulic unit in the conventional manner and the piston rod 3 extends. Here, the contact portion 4 of the piston rod 3 moves along the contact surface 6 of the trimming plate 5 and a force is applied to the outboard motor 105 via the trimming plate 5 so that the outboard motor 105 is moved or pivoted relative to the hull 102 via the joint 103.
If the central mid-axis MA of the piston rod 3 were completely orthogonal relative to the trimming plate 5 or contact surface 6, α=0° and MA=KE would apply. In this case, the lateral forces would be minimal due to the orthogonal force application, but a noticeable slip-stick effect could occur. It has been shown that with α≤6° and especially in the range of 1.5°≤α≤4.5° an optimum compromise between introduced transverse forces and occurrence of the slip-stick effect can be achieved.
When configuring the curvature of the contact surface 6 of the trimming plate 5, this is initially selected so that it is individually matched to the corresponding kinematics of the boat motor 100 with regard to trim or power trim. Here, it is notionally assumed that an orthogonal alignment of the central mid-axis MA of the piston rod 3 to the trimming plate 5 or contact surface 6 is always to be achieved. Subsequently, if required, the contact surface 6 of the trimming plate 5 is rotated by an angle α, the angle α being at most 6°. This results in an asymmetrical and convex curvature of the contact surface 6 of the trimming plate 5 between the first contact position AP1 and the second contact position AP2.
In
As shown, the contact portion 4′ of the piston rod 3 in this second embodiment is designed as a flat surface. Thus, in contrast to the spherical design of the contact portion according to the first embodiment, there is a line contact between the contact portion 4′ of the piston rod 3 and the contact surface 6 of the trimming plate 5. In this embodiment, the angle α=0°. Overall, this results in lower surface pressure with minimized slip-stick effect.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102021213912.4 | Dec 2021 | DE | national |
