U.S. patent application number 14/655416 was filed with the patent office on 2015-12-03 for lubrication system for a rotary vacuum pump.
This patent application is currently assigned to VHIT S.P.A.. The applicant listed for this patent is VHIT S.P.A.. Invention is credited to Leonardo Cadeddu.
Application Number | 20150345496 14/655416 |
Document ID | / |
Family ID | 47790366 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150345496 |
Kind Code |
A1 |
Cadeddu; Leonardo |
December 3, 2015 |
LUBRICATION SYSTEM FOR A ROTARY VACUUM PUMP
Abstract
A lubrication system (200) for a rotary vacuum pump (300)
connectable to a thermal engine comprises a suction duct (50)
connecting the pump (300) to a power brake (16), and a connecting
duct (23) connecting the inside of the engine with the suction duct
(50) in order to generate, through the connecting duct (23), a flow
of an air-oil mixture sucked from the inside of the engine. A pump
having a casing (40) which defines a pumping chamber (44) and a
connecting duct (23) formed in the casing (40), and a lubrication
method for such a pump are also provided.
Inventors: |
Cadeddu; Leonardo;
(Offanengo (CR), IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VHIT S.P.A. |
Offanengo (CR) |
|
IT |
|
|
Assignee: |
VHIT S.P.A.
Offanengo (CR)
IT
|
Family ID: |
47790366 |
Appl. No.: |
14/655416 |
Filed: |
December 13, 2013 |
PCT Filed: |
December 13, 2013 |
PCT NO: |
PCT/IB2013/060911 |
371 Date: |
June 25, 2015 |
Current U.S.
Class: |
418/1 ; 418/225;
418/83 |
Current CPC
Class: |
F04C 25/02 20130101;
F04C 18/3441 20130101; F04C 15/0088 20130101; F04C 2/06 20130101;
F04C 29/02 20130101; F04C 18/06 20130101; F04C 29/028 20130101 |
International
Class: |
F04C 29/02 20060101
F04C029/02; F04C 25/02 20060101 F04C025/02; F04C 18/06 20060101
F04C018/06; F04C 15/00 20060101 F04C015/00; F04C 2/06 20060101
F04C002/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2012 |
IT |
TO2012A001157 |
Claims
1. Lubrication system (200) for a rotary vacuum pump (300)
connectable to a thermal engine, comprising a suction duct (50)
adapted to connect the pump (300) to a power brake (16),
characterized in that said lubrication system (200) further
comprises a connecting duct (23) adapted to connect the inside of
the engine with the suction duct (50) in order to generate through
the connecting duct (23) a flow of an air-oil mixture sucked from
the inside of the engine.
2. Lubrication system (200) according to claim 1 in which the
suction duct (50) is provided with two one-way valves (14, 15),
characterized in that the connecting duct (23) is connected to the
suction duct (50) in a portion of the duct (50) comprised between
the two one-way valves (14, 15).
3. Lubrication system (200) according to claim 2, characterized in
that the connecting duct (23) is connected to the suction duct (50)
in a region downstream of and close to the valve (14).
4. Lubrication system (200) according to claim 3, characterized in
that the connecting duct (23) has a narrowing (24) in its end
portion terminating in the suction duct (50).
5. Rotary vacuum pump (300) connectable to a suction duct (50) of a
power brake (16), said pump comprising a casing (40) which defines
a pumping chamber (44); a rotor (12) and a vane (22) mounted on the
rotor (12), said rotor and vane being suitable to divide the
chamber (44) into a suction chamber (13) and a compression chamber
(18); characterized in that the pump (300) further comprises a
connecting duct (23) formed in the casing (40) and adapted to
connect the inside of the engine to the suction duct (50).
6. Rotary vacuum pump (300) according to claim 5 and connected to
the suction duct (50) by means of a one-way valve (14),
characterized in that the connecting duct (23) is connected to the
suction duct (50) downstream of and close to the valve (14).
7. Rotary vacuum pump (300) according to claim 6, characterized in
that the connecting duct (23) has a narrowing (24) in its end
portion terminating in the suction duct (50).
8. Rotary vacuum pump (300) according to claim 6, characterized in
that the connecting duct (23) is made by drilling.
9. Rotary vacuum pump (300) according to claim 7, characterized in
that the connecting duct (23) has a funneled shape at its end
portion oriented towards the part of the casing (40) facing the
engine.
10. Lubrication method for a rotary vacuum pump (300) according to
claim 9, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
11. Lubrication method for a rotary vacuum pump (300) according to
claim 7, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
12. Rotary vacuum pump (300) according to claim 6, characterized in
that the connecting duct (23) has a funneled shape at its end
portion oriented towards the part of the casing (40) facing the
engine.
13. Lubrication method for a rotary vacuum pump (300) according to
claim 12, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
14. Lubrication method for a rotary vacuum pump (300) according to
claim 6, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
15. Rotary vacuum pump (300) according to claim 5, characterized in
that the connecting duct (23) is made by drilling.
16. Rotary vacuum pump (300) according to claim 5, characterized in
that the connecting duct (23) has a funneled shape at its end
portion oriented towards the part of the casing (40) facing the
engine.
17. Lubrication method for a rotary vacuum pump (300) according to
claim 16, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
18. Lubrication method for a rotary vacuum pump (300) according to
claim 5, wherein an oriented flow of an air-oil mixture starting
from the compression chamber (18) of the pump (300) is generated,
said flow passing through the connecting duct (23), reaching the
suction duct (50) and returning to the suction chamber (13) of the
pump (300).
19. Lubrication system (200) according to claim 2, characterized in
that the connecting duct (23) has a narrowing (24) in its end
portion terminating in the suction duct (50).
20. Lubrication system (200) according to claim 1, characterized in
that the connecting duct (23) has a narrowing (24) in its end
portion terminating in the suction duct (50).
Description
TECHNICAL FIELD
[0001] The present invention relates to rotary vacuum pumps, and
more specifically it concerns a lubrication system for a rotary
vacuum pump.
[0002] Preferably, but not exclusively, the invention is applied in
the so-called single-vane pumps, i.e. pumps where the rotor
includes a single vane with constant length, and the following
description will mainly refer to this preferred application.
PRIOR ART
[0003] Single-vane pumps are often used as vacuum pumps, for
instance in the automotive field. They comprise a body defining a
chamber, for instance with approximately elliptical cross section,
in which the rotor rotates, in tangential contact, about an
eccentric axis. The rotor has a diametrical slot where the vane is
mounted and the vane is radially movable in the slot so that, while
the rotor is rotating, the vane ends slide substantially in contact
with the internal wall of the chamber. The chamber is divided by
the rotor and the vane into a suction room and a pressure room,
between which a pumped fluid is displaced.
[0004] In pumps used in motor car engines, when the rotor and the
vane rotate air is sucked from the power brake through non-return
one-way valves and is mixed with oil sent to the pump by the engine
lubrication pump. The mixed air and oil are subsequently compressed
in the chamber and then discharged into the engine, where oil is
separated by means of an oil separator and collected in the oil
sump.
[0005] Lubrication systems for rotary vacuum pumps used in the
automotive field and mounted on the thermal engine are known, in
which the pump is lubricated by the engine lubrication oil under
pressure. An example is disclosed in ES 2340182.
[0006] In another known lubrication system, disclosed for instance
in DE 3841329, lubrication oil coming under pressure from the pump
drive shaft is sprayed into or sent to a coaxial bore in the rotor
and conveyed inside the pump by the latter.
[0007] A first problem encountered in such pumps and in their
lubrication systems is the oil return, under particular speed
conditions of the engine, towards the power brake through the
non-return valve, with consequent damages, in particular, of the
parts made of elastomeric material and incompatible with the engine
oil.
[0008] Oil return is caused by depression variations occurring
upstream and downstream the valves under particular speed
conditions of the engine. Those depressions are such that they
nullify the forces generated by the pressure difference and by the
resilient means, and have the effect of making the sealing element
operate in "weak" manner, thereby allowing oil migration towards
the power brake.
[0009] The same kind of problem may occur when the engine is off
and oil is present inside the pump, if the suction valve(s) do(es)
not have a perfect seal.
[0010] The solution of sucking atmospheric pressure between the
non-return valves in order to prevent oil return to the power brake
is known, for instance as disclosed in DE 102011005464.
[0011] A second problem may occur when the engine is turned off:
such a problem is the oil suction into the pump when the engine
stops and the oil return to the power brake when the engine is
off.
[0012] The phenomenon of oil suction, in this second case, is due
to the permanence of a depression inside the pump for relatively
short but significant periods, occurring when the engine is turned
off.
[0013] A third technical problem may occur in case the engine on
which the pump is mounted, after having been turned off, rotates in
reverse direction, driven by the vehicle drive system. If oil
suction occurred as disclosed with reference to the second problem,
such a third problem may cause a hydraulic block with consequent
pump breaking. A known solution for avoiding the occurrence of the
second problem and the third problem related thereto is disclosed
in document WO 2007003215, which teaches applying non-return valves
to the exhaust, which valves have the task of favouring a quick
restoration of the atmospheric pressure inside the pump, when the
engine is stopped.
[0014] Use of a safety valve in the suction chamber, arranged to
discharge oil under pressure toward the oil sump thereby solving
the third problem, is also known in the art.
DESCRIPTION OF THE INVENTION
[0015] It is an object of the present invention to provide a
lubrication system for a rotary vacuum pump which solves the
problems of the prior art.
[0016] According to the invention, this is achieved by means of a
lubrication system for a rotary vacuum pump for a thermal engine,
connected to a power brake through a suction duct, wherein the
system comprises a duct connecting the inside of the engine with
the suction duct in order to generate, through the connecting duct,
a flow of an air-oil mixture sucked from the inside of the
engine.
[0017] In a second embodiment, a valve for protection in case of
counter-rotation, discharging oil towards the engine oil sump, is
provided in the lubricating system.
[0018] The invention also concerns a rotary vacuum pump connected
to the power brake through a suction duct and comprising a casing
defining a pumping chamber and a connecting duct formed in the
casing and connecting the inside of the engine to the suction duct
in order to generate, through the duct formed in the casing, a flow
of an air-oil mixture sucked from the inside of the engine.
[0019] In a further aspect, the invention also provides a
lubrication method for a rotary vacuum pump, in which an oriented
flow of an air-oil mixture is generated, which flow starts from the
compression chamber of the pump, reaches the suction duct through
the connecting duct and returns to the suction chamber of the
pump.
BRIEF DESCRIPTION OF THE FIGURES
[0020] The above and other features and advantages of the present
invention will become apparent from the following description of
preferred embodiments given by way of non-limiting examples with
reference to the accompanying drawings, which show the invention
applied to a single-vane pump and in which:
[0021] FIG. 1 shows a diagram of a conventional lubrication system
for a single-vane rotary vacuum pump;
[0022] FIG. 2 shows a diagram of a lubrication system according to
the invention;
[0023] FIG. 3 is a cross-sectional view of a pump for the
lubrication system according to the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0024] The invention will be described in detail with reference to
its application in a single-vane pump, as defined above. In order
to make understanding of the invention easier, FIG. 1 shows a
diagram of a conventional lubrication system for a rotary vacuum
pump. In the example, a lubrication system for a single-vane pump
is illustrated. The present invention can however be employed in
any pump with vane rotor.
[0025] Referring to FIG. 1, pump 10 comprises a casing 40 defining
a pumping chamber 44, for instance with an approximately elliptical
cross-section, having an internal wall 42. Chamber 44 houses a
rotor 12 that, in known manner, rotates substantially tangent to
wall 42. The rotor has a radial slot 46 where a vane 22, radially
slidable within the same slot, is mounted. During the clockwise
rotation of rotor 12, the vane and the rotor divide chamber 44 into
a suction chamber 13 and a compression chamber 18. Moreover a
lubrication channel 11, connected to an engine lubrication pump 17,
is formed in casing 40.
[0026] Lubrication system 100 comprises, besides pump 10, a suction
duct 50, which connects pump 10 to a power brake 16 and through
which pump 10 sucks air from the power brake. Duct 50 is equipped
with one-way valves 14 and 15.
[0027] In the operation of a single-vane pump in a known
lubrication system, when rotor 12 and vane 22 rotate clockwise, air
is sucked from power brake 16 through valves 14 and 15 of suction
duct 50 and is mixed in pumping chamber 44 with oil sent through
channel 11 by an engine lubrication pump 17, sucking the engine oil
from oil sump 20. The mixed air and oil are subsequently compressed
in compression chamber 18 and then exhausted into the engine
through a stop valve 19, known in the art as "check valve". Inside
the engine, oil is separated from air by means of an oil separator
and is then collected in oil sump 20.
[0028] During such operation, the problem described above of the
oil return towards the power brake when the engine is on can occur,
since, under particular speed conditions of the engine, depression
variations are generated upstream and downstream valves 14, 15,
which variations are such as to nullify the forces generated by the
pressure difference and the resilient means. Thus the sealing
elements in the valves are made to operate in "weak" manner,
resulting in an oil migration towards the power brake and in
damages, in particular, of the parts thereof made of an elastomeric
material incompatible with the engine oil.
[0029] As said before, when the engine is turned off, other
problems can arise: oil suction into the pump when the engine stops
and oil return towards the power brake when the engine is off.
[0030] Oil suction is due to the permanence of a depression inside
pumping chamber 44 of pump 10 for relatively short but significant
periods when the engine is turned off. Such a depression causes oil
suction from lubrication channel 11.
[0031] A known solution to this problem consists in using a valve
21 for protection in case of counter-rotation, discharging oil
towards oil sump 20 when the engine on which pump 10 is mounted,
after having been turned off, rotates in reverse direction, driven
by the vehicle drive system.
[0032] Oil return towards the power brake when the engine is off
may take place when, after the engine has been turned off,
depression is maintained for relatively long periods in suction
chamber 13 and in the portion of suction duct 50 between one-way
valves 14 and 15. This phenomenon may give rise to two different
problems: oil suction from the pump towards power brake 16,
occurring if valves 14 and 15 perform a "weak" sealing, or sticking
of the sealing element in valve 14, favoured by the soiling by oil
residuals, when the valve sealing is good and hence the depression
is maintained for very long periods, when the engine is off, with a
consequent cooling that worsens the phenomenon.
[0033] Said sticking is due to the force generated by the flexible
member of the valve, in addition to the pressure difference acting
on the sealing member of the valve.
[0034] A lubrication system 200 according to the invention will now
be described with reference to FIGS. 2 and 3. In FIGS. 2 and 3,
elements corresponding to those illustrated in FIG. 1 are denoted
by the same reference numerals.
[0035] FIG. 2 shows a diagram of lubrication system 200 according
to the invention, and FIG. 3 shows an exemplary embodiment of a
pump 300 for lubrication system 200 according to the invention.
[0036] Lubrication system 200 according to the invention includes,
like prior art lubrication system 100, a pump 300, for instance a
single-vane pump.
[0037] The lubrication system according to the invention can be
applied also to a multi-vane pump.
[0038] The system according to the invention further comprises
suction duct 50, which connects pump 300 to power brake 16 and
through which pump 300 sucks air from power brake 16. More
particularly, air is sucked through valves 14 and 15. Preferably,
duct 50 is equipped with two one-way valves 14, 15. Preferably,
valve 14 is arranged to connect pump 300 with suction duct 50.
Preferably, system 200 includes, like prior art system 100,
lubrication channel 11 of pump 300, connected to engine lubrication
pump 17, and check valve 19 located at the exit from a discharge
duct 26, connecting the pumping chamber 44 with the inside of the
engine and introducing the air-oil mixture into the engine after
compression in compression chamber 18.
[0039] As shown in FIG. 2, valve 21 for protection in case of
counter-rotation has been eliminated in system 200 according to the
invention.
[0040] In a second embodiment of the invention, not shown in the
Figures, the lubrication system further includes valve 21 for
protection in case of counter-rotation, discharging oil towards oil
sump 20, similarly to the prior art system shown in FIG. 1.
[0041] Lubrication system 200 according to the invention includes a
connecting duct 23 connecting the inside of the engine with suction
duct 50, in turn connecting pump 300 to power brake 16.
[0042] Connecting duct 23 has a narrowing 24 in its end portion, in
correspondence of suction duct 50. Preferably, connecting duct 23
is connected to suction duct 50 in a portion comprised between
one-way valves 14, 15. Preferably, connecting duct 23 is connected
to suction duct 50 in a region downstream of and close to valve 14,
and is arranged to connect suction duct 50 with the inside of the
engine, preferably with an exhaust region 25 of the oil-air
mixture, adjacent to check valve 19 and to the outlet of a
discharge duct 26 connecting it.
[0043] During operation, an oriented flow of the air-oil mixture,
shown by the arrows in FIGS. 2, 3, is generated. That flow starts
from compression chamber 18 of pump 300 and, through connecting
duct 23 and narrowing 24, reaches suction duct 50, returning then
to pump 300, in particular to suction chamber 13, through valve
14.
[0044] Advantageously, the provision of the oriented flow of the
air-oil mixture flowing through connecting duct 23 eliminates the
problem of the oil return towards the power brake when the engine
is on, since pressure variations upstream and downstream valves 14,
15 and the resulting oil migration towards the power brake are
eliminated, and prevents the permanence of a depression inside the
pump when the engine is off, which depression could cause oil
suction into the pump. The flow of the air-oil mixture sucked from
the inside of the engine, passing through connecting duct 23 and
narrowing 24, has moreover the advantage of optimising lubrication
of the pumping assembly of pump 300 and of reducing the oil amount
taken from the lubrication circuit, thereby reducing the overall
energy utilised.
[0045] The phenomenon of oil suction into the pump when the engine
is off can no longer occur in lubrication system 200 according to
the invention, and hence valve 21 for protection in case of
counter-rotation is no longer necessary, since the depression can
no longer be established in pumping chamber 44 of pump 300 and in
suction duct 50, which are at atmospheric pressure or at a slight
temporary overpressure existing in the inside of the engine.
[0046] Advantageously, oil return towards the power brake or the
sticking of the sealing element in valve 14 when the engine is off
can no longer occur in system 200, since, when the motor is turned
off, atmospheric pressure is established in pumping chamber 44 of
pump 300 and between valves 14, 15, thanks to the provision of
connecting duct 23.
[0047] In the second embodiment of the invention, valve 21 for
protection in case of counter-rotation is provided to solve the
problem caused by oil inflow generated by other phenomena, such as
for instance accumulation of oil under pressure in the engine or
oil draining, occurring in rare kinds of engines. In such cases,
valve 21 for protection in case of counter-rotation is
maintained.
[0048] FIG. 3 shows an exemplary embodiment of a pump 300 for
lubrication system 200 according to the invention.
[0049] Pump 300 according to the invention includes, in known
manner, casing 40 and pumping chamber 44 with its internal wall 42.
Chamber 44 houses rotor 12, which, in known manner, rotates
substantially tangent to wall 42. The rotor has radial slot 46
where vane 22, radially slidable within the same slot, is mounted.
During the clockwise rotation of rotor 12, the vane and the rotor
divide chamber 44 into suction chamber 13 and compression chamber
18. Lubrication channel 11, connected to engine lubrication pump
17, is preferably formed in casing 40.
[0050] Pump 300 according to the invention further includes
connecting duct 23 connecting the inside of the engine with suction
duct 50, in turn connecting pump 300 to power brake 16.
[0051] Preferably, pump 300 is connected to suction duct 50 by
means of one-way valve 14.
[0052] Connecting duct 23 is formed, for instance drilled, in
casing 40 and it has a narrowing 24 in its end portion, in
correspondence of suction duct 50. Preferably, connecting duct 23
is connected to suction duct 50 between one-way valves 14, 15,
downstream of and close to valve 14, and is arranged to connect
suction duct 50 with the inside of the engine, preferably with the
exhaust region of the oil-air mixture.
[0053] Preferably, connecting duct 23 has a funnel-shaped end
portion 27, which is formed in correspondence of the portion of
casing 40 facing the engine, in region 25 adjacent to check valve
19 and to the outlet of discharge duct 26 where the air-oil mixture
is exhausted.
[0054] The funnel shape of end portion 27 of connecting duct 23
assists in collecting oil particles at the suction.
* * * * *