This application claims the benefit of Swedish Application No. 1350384-2 filed Mar. 26, 2013 and PCT Application No. SE2014/050168 filed Feb. 11, 2014.
The present invention relates to a hydraulic pump assembly, comprising a rotatable piston drum with at least one centrifugal lever pivotally attached thereto for radial movements between radial flanges under the action of centrifugal force at rotation of the piston drum, the centrifugal lever being arranged to control the position of a valve member, preferably a ball, at the opening end of a bore in the piston drum.
Such a hydraulic pump assembly can be used in a system including a wet disc coupling for distributing torque between front and rear axles of an all wheel drive vehicle (AWD) and/or between left and right wheels of a two or four wheel drive vehicle. This hydraulic pump assembly for actuating a wet disc coupling is shown and described in WO 2010/019094 and in a more developed form in WO 2011/043722. For a better understanding of the background of the invention, reference is made to these two publications, especially the latter.
A desirable property of an all wheel drive system and its actuator is high dynamics. Based on vehicle dynamical and traction optimizing desired values, it shall be possible to reach the desired torque as quickly as possible. The accuracy with which this is obtained shall also be as high as possible without creating superimposed disturbances, i.e. overtones of any kind to the fundamental signal.
A pressure regulator and thus torque regulator of the type shown in the above publications has basically a highly dynamic function. There is an inherent risk that it may react in a non-desirable way on process disturbances that are caused by for example external acceleration, vibrations, temperature changes, and rotation speed variations. As a result superimposed torque variations in a non-desired frequency range may occur.
It may thus be desirable to introduce control over the dynamics of the regulator in a defined frequency range in order not to be forced to make a balance between high dynamics and robustness against process disturbances.
In a hydraulic pump assembly of the kind described above this may according to the invention be attained by the introduction of a defined friction surface between the lever and one of the radial flanges and by spring means for resiliently biasing the lever against said one of the flanges.
The friction surface is preferably in the form of a knob on an axial side of the lever.
In a first embodiment a compression spring placed in an axial bore in the lever may be arranged to push a ball against the other radial flange.
In the known regulator there is a ring spring arranged around the piston drum and laid over an axial pin on the lever for controlling the radial movement of the lever. In a second embodiment of the invention the axial pin has a surface sloping downwards from the lever towards the piston drum.
The invention will be described in further detail below under reference to the accompanying drawings, in which
The hydraulic system shown in
Hydraulic oil for the hydraulic actuator system is contained in a reservoir 6. It is sucked into the pump 2 through a hydraulic line 7 and is delivered therefrom towards a hydraulic cylinder 8 for actuating a disc package 9 of a limited slip coupling 10 by means of a piston 11 in the cylinder 8.
Depending on the position of the centrifugal regulator 4 and thus the pressure overflow valve 5, a portion and sometimes all of the hydraulic flow is diverted through a hydraulic line 12, through the overflow valve 5 and back to the reservoir 6. The result is that the hydraulic pressure delivered to the cylinder 8 is governed by the centrifugal regulator 4.
A relief valve 13 is connected to the cylinder 8 by means of a hydraulic line 14. The relief valve 13 has the purpose of diverting hydraulic oil from the cylinder 8 to the reservoir 6, when its pressure exceeds a certain level, for example 40 bar.
The electric motor 1, the pump 2, the drive shaft 3, the centrifugal regulator 4, and the overflow valve 5 are included in a hydraulic pump assembly.
Shown in
For controlling the application of each ball 22 against the open end of its bore 21 and thus the hydraulic flow past the ball 22, there is a centrifugal lever 23. The lever 23 is relatively close to a first one of its ends pivotally attached to the piston drum 20 by means of a lever pin 24. At rotation of the piston drum 20 the other or second end of the lever 40 will be biased radially out from the piston drum 20 by the centrifugal force. This tendency is counteracted by a spring means in the form of a ring spring 25, laid around spring pins 26 on the levers 23. The ball 22 is preferably connected to the lever end by means of a spring clip 27, which will allow the ball 22 to fit sealingly in the bore end or mouth of the bore 21.
In
For further information about the design and function of the hydraulic pump assembly, reference is made to said WO 2011/043722.
As has been explained more in detail above, the main object of the invention is to improve the control of the dynamics of the centrifugal regulator, comprising in essence the levers 23 controlling the balls 22.
A first embodiment of a device for such an improvement is shown in
Now, according to the improvement, a certain control of the levers 23 in cooperation with the drum flanges 20′ is introduced.
On one of its axial surfaces, namely its left hand surface in
Generally opposite the friction surface, the lever 23 is provided with a bore 29, housing a compression spring 30 and a ball 31 contacting the right hand flange 20′. The spring and ball arrangement will create an axial force biasing the friction surface 28 into engagement with the left hand flange 20′. There will also be a minor friction between the ball 31 and the right hand flange 20′. The required axial force may be provided by any alternative spring arrangement, as will be apparent to any person skilled in the art.
A second embodiment of a device for the improvement mentioned above is shown in
Referring to
The ring spring 25, which was present in the prior art device shown in
As is most clearly shown in
In the known version according to
The lever 23 is shown in
The invention is not limited to its use with a hydraulic pump assembly exactly as shown and described in the referenced publications.
Modifications are possible within the scope of the appended claims. The friction surfaces may for example be arranged on the flanges instead of on the levers.
Number | Date | Country | Kind |
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1350384 | Mar 2013 | SE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/SE2014/050168 | 2/11/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/158070 | 10/2/2014 | WO | A |
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102575666 | Jul 2012 | CN |
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Entry |
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Russian Office Action dated Nov. 16, 2017, Applicant: BorgWarner TorqTransfer Systems AB, Russian Application Serial No. 2015145028 filed Feb. 11, 2014; 7 pages. |
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Chinese Office Action dated Mar. 9, 2017 ; Application No. 201480018545.3; Applicant: BorgWarner TorqTransfer Systems AB; 6 pages. |
Number | Date | Country | |
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20160048133 A1 | Feb 2016 | US |