Field of the Invention
[0001] The present invention concerns a dual outlet pressure pump comprising a first pump
entity and a second pump entity and more particularly a dual outlet pressure pump
whereby a first pump rotor and a second pump rotor are operatively arranged on a common
drive shaft to convey a fluid. The present invention further concerns a hydraulic
control system for a continuously variable transmission of a vehicle, comprising a
dual outlet pressure pump.
Description of Related Art
[0002] It is well known to utilize one or more fixed displacement pumps in continuously
variable and other automated transmissions of vehicles. More recently, also variable
displacement vane pumps have been considered for use as oil pumps for vehicle transmissions
and engines. By providing a suitable control mechanism to alter the capacity of the
pump to provide only the amount of pressurized lubrication oil necessary for proper
operation of the engine, energy required to pressurize unneeded oil can be saved and
thus energy efficiency of the pump, and the entire vehicle, can be improved.
[0003] Single pump hydraulic systems are particularly inefficient in applications requiring
high-pressure fluid because the single pump continues to deliver high flow, high pressure
fluid even when only low flow is needed. This results in unnecessary consumption of
power from the vehicle engine or battery and may tend to reduce the overall life of
the pump.
[0004] Multiple pump systems are designed to minimize this undesirable behavior by providing
an additional pump that can be activated to deliver a required fluid flow rate or
pressure depending upon the operating conditions.
[0005] In
US 8 128 377 B2 a hydraulic fluid supply system is disclosed that utilizes a split-pressure configuration
in cooperation with first and second pumps to continuously deliver variable flow,
high-pressure fluid and fixed flow, low-pressure fluid, depending on the individual
needs of two independent hydraulic circuits. In one embodiment of the disclosed invention,
a split-pressure hydraulic fluid supply circuit for supplying pressurized fluid to
a multi-speed transmission is provided. The split-pressure hydraulic fluid supply
circuit includes a first pump, a second pump, a low-pressure circuit portion, and
a high-pressure circuit portion. The first pump has both inlet and outlet ports, and
is driven by the power source to provide a continuous flow of pressurized hydraulic
fluid at a fixed rate. The second pump has an inlet port, an outlet port, and a regulator
port, and is driven by the power source to provide a continuous flow of pressurized
hydraulic fluid at variable rates. The low-pressure circuit portion includes a work
circuit fluidly coupled to the first pump. The low-pressure circuit portion is adapted
to supply all of the low-pressure hydraulic fluid needed by the multi-speed transmission.
The high-pressure circuit portion includes a high-pressure work circuit fluidly coupled
to the second pump. The high-pressure circuit portion is adapted to supply all of
the high-pressure hydraulic fluid needed by the multi-speed transmission. No fluid
coupling is provided between the high-pressure work circuit and the low-pressure work
circuit.
[0006] EP 2 441 985 A2 provides a hydraulic system for an automatic transmission which supplies oil from
an oil reservoir to a high-pressure part and a low-pressure part, using a cascaded
pump arrangement, which includes a first oil pump pumping up oil from the oil reservoir
and supplying the oil to the low-pressure part, and a low-pressure regulating valve
connected to a low-pressure part channel connecting the first oil pump with the low-pressure
part, and controlling the pressure of the oil discharged from the first oil pump.
A second oil pump receives the oil and supplies it to the high-pressure part of the
hydraulic system.
[0007] The known systems using multiple pumps to provide hydraulic fluid at different pressure
levels and flow rates help to save energy but are often complicated in design and
expensive to manufacture. Simplified and more affordable designs suffer from increased
wear on components.
[0008] Object of the present invention is to provide pumps with the capability to provide
fluids simultaneously at multiple pressure levels and flow rates. The pumps should
combine improved wear resistance and longer service life with simplified construction
and low cost and thereby improve known hydraulic control systems of said type in this
respect.
Summary of the Invention
[0009] The object is achieved by a dual outlet pressure pump with the features of claim
1.
[0010] According to the invention, a dual outlet pressure pump comprising a first pump entity
and a second pump entity, whereby a dual pump housing comprises a first pump rotor
cavity and a second pump rotor cavity separated by a diaphragm with a bore and whereby
a first pump rotor and a second pump rotor are operatively arranged on a common drive
shaft to convey a fluid is provided. Angular placement of elements of the first pump
entity relative to elements of the second pump entity about a pump axis is such, that
the radial force exerted by the fluid pressure in a first pump discharge region of
the first pump rotor cavity upon the first pump rotor is opposed in direction to the
radial force exerted by the fluid pressure in a second pump discharge region of the
second pump rotor cavity upon the second pump rotor.
[0011] By not simply stacking pump entities of known design onto a common drive shaft, but
instead consciously placing and aligning pump elements such as pump suction ports
and pump discharge ports or eccentric pump rotor cavities, vibrations and wear of
dual outlet pressure pump components can be significantly reduced. Many different
types and of asymmetric pumps of widely differing capacities can be successfully combined
by following the principles outlined in the present invention.
[0012] The object is further achieved by a hydraulic control system for a continuously variable
transmission of a vehicle, comprising a dual outlet pressure pump.
[0013] The directional terms "axial" and "radial" in the context of the present invention
always relate to the axis of the rotating pump shaft.
[0014] Refinements of the invention are given in the subclaims, the description and the
enclosed drawings.
[0015] Preferably the dual outlet pressure pump comprises a first pump entity and a second
pump entity which are any combination of either a hydraulic rotary vane pump or a
hydraulic gear pump.
[0016] Rotary vane pumps and gear pumps are known in many designs and can be configured
in many combinations to adapt to specific requirements of hydraulic control system
applications. Combinations of two pump entities of the same type, such as rotary vane
pump with rotary vane pump or gear pump with gear pump are useful. Preferred are combinations
of a rotary vane pump and a gear pump as either the first or second pump entity. This
allows a pump designer to combine complementary strengths of both pump types.
[0017] Many of the abovementioned rotary vane pumps and gear pumps can be said to comprise
an "operational plane of symmetry". In an internal gear pump such as a gerotor pump
an imagined plane through the axis of rotation of a gerotor pump inner rotor and the
axis of rotation of a gerotor pump outer rotor is fixed with respect to the gerotor
pump housing. This imagined "operational plane of symmetry" divides the pump rotor
cavity into a lower pressure pump suction region comprising the pump suction port
and a higher pressure pump discharge region comprising the pump discharge port. It
is the fluid pressure in the higher pressure pump discharge region that exerts a significant
radial force on the gerotor pump inner rotor and thus on the pump shaft supporting
the gerotor pump inner rotor.
[0018] In the case of a rotary vane pump having a circular cylindrical pump rotor cavity
an analogous "operational plane of symmetry" is an imagined plane through the axis
of rotation of the pump rotor and the axis of said circular cylindrical pump rotor
cavity. In this example again the imagined "operational plane of symmetry" divides
the pump rotor cavity into a lower pressure pump suction region comprising the pump
suction port and a higher pressure pump discharge region comprising the pump discharge
port. But here it is the combined fluid pressure of the moving compartments formed
between vanes of the rotary vane pump in the higher pressure pump discharge region
that exerts a significant radial force on the rotary vane pump rotor and thus on the
pump shaft supporting the rotary vane pump rotor.
[0019] A preferred embodiment of the dual outlet pressure pump comprising either a hydraulic
rotary vane pump and/or a hydraulic gear pump as the first pump entity and the second
pump entity, said first and second pump entities are angularly aligned about the pump
axis such that a first pump "operational plane of symmetry" and the second pump "operational
plane of symmetry" intersect at a pointed angle and the first pump discharge region
of the first pump rotor cavity and the second pump discharge region of the second
pump rotor cavity are provided in opposite larger quadrants of the intersecting first
and second pump "operational planes of symmetry".
[0020] In a further preferred embodiment of the inventive dual outlet pressure pump the
first pump discharge region of the first pump rotor cavity and the second pump suction
region of the second pump rotor cavity are hydraulically connected through a connection
passage.
[0021] Said connection passage allows pump fluid to pass from the lower pressure pump directly
to the higher pressure pump. The internal pressure drops of the two pumps are adding
up and the maximum pressure level achievable with the same first and second pump entities
is higher than in the embodiment without said connection passage.
[0022] In a preferred embodiment of the dual outlet pressure pump said connection passage
comprises a connection passage inlet which is located in the area of highest pressure
of the first pump discharge region of the first pump rotor cavity. By locating the
connection passage inlet close to the point of highest pressure of said connection
passage inlet flow characteristics of the first pump entity can be significantly improved.
Zones of reverting flow of high pressure fluid are minimized whereby pump friction
is reduced. Guiding pump fluid through a streamlined connection passage inlet right
through the diaphragm of the dual pump housing solves many common problems in hydraulic
pump outlet design and allows for a very compact dual outlet pressure pump scheme.
[0023] According to a further embodiment of the invention either the first pump entity or
the second pump entity of the dual outlet pressure pump is a variable displacement
pump. This allows the relative pumping capacity of the first and second pump entities
to be altered although both are driven by the same drive shaft.
[0024] In a further embodiment of the invention either the first pump entity or the second
pump entity is a fixed displacement pump. Fixed displacement pumps feature simple
construction and reliable operation.
[0025] In another preferred embodiment of the dual outlet pressure pump the first pump entity
is a lower pressure higher capacity pump and the second pump entity is a higher pressure
lower capacity pump. This combination of pump entities is particularly useful as in
many hydraulic systems there is a relatively large and variable need for fluid at
low pressure and an often intermittent and limited need for fluid at high pressure.
[0026] Preferably the first pump entity is a rotary vane pump. Rotary vane pumps are available
as variable capacity and low pressure types. Also preferably is the second pump entity
is a gerotor pump. A small gerotor pump is a nearly perfect choice for a higher pressure
lower capacity pump.
[0027] The axial bore of diaphragm of the dual pump housing of the dual outlet pressure
pump according to the invention may comprise a bearing for additional performance
and increased operating life.
Brief Description of Drawings
[0028] The invention is described below as an example with reference to the drawings.
- Fig. 1
- shows multiple sectional views of a dual pump according to the present invention.
- Fig. 2
- is a schematic view of a hydraulic control system for a continuously variable transmission
in an "Idle" state.
- Fig. 3
- is a schematic view of a hydraulic control system for a continuously variable transmission
in a "Speed UP" state of operation.
- Fig. 4
- is a schematic view of a hydraulic control system for a continuously variable transmission
in a "Constant Speed" state of operation.
- Fig. 5
- is a schematic view of a hydraulic control system for a continuously variable transmission
in a "Speed DOWN" state of operation.
- Fig. 6
- shows several embodiments of a variable displacement vane pump with enhanced discharge
port as known in the prior art.
Detailed Description of the Invention
[0029] Figure 1 shows schematically multiple sectional views of an exemplary preferred embodiment
of the dual outlet pressure pump comprising a variable displacement vane pump (VDVP)
as a first pump entity 10 and a small gerotor pump (designated as boost pump BP in
Figures 2 to 5) as second pump entity 20. Three schematic sectional views are aligned
along a pump axis 40. The sectional view 30 in the center of Fig. 1 shows the dual
pump housing 17 comprising a first pump rotor cavity 36, a second pump rotor cavity
39 and diaphragm 37 having a bore 38. Pump shaft 15 is arranged to extend through
the bore 38. Also shown is a connection passage 33 fluidly connecting first pump rotor
cavity 36 and second pump rotor cavity 39. Connection passage 33 has a carefully designed
connection passage inlet 32 and connection passage outlet 34.
[0030] View A of Fig. 1 shows the variable displacement vane pump in a sectional view. The
pump has a first pump suction port 11 arranged in a low pressure (0 bar) first pump
suction region 42. First pump rotor 16 is equipped with several vanes to fit into
slide 13 which is tensioned by spring 14. Slide 13 is movably arranged inside dual
pump housing 17. By varying a fluid pressure in control port 18 the position of slide
13 can be changed and thus the volumetric pumping capacity of the VDP can be varied
according to hydraulic control system requirements.
[0031] Assumed is a rotary motion of pump shaft 15 whereby the upper part of shaft 15 moves
into the plane of Fig. 1 in view 30. This rotation of pump shaft 15 appears as clockwise
rotation of rotor 16 in view A. Fluid is transported from first pump suction region
to first pump discharge region 44 (15 bar) and may be discharged through first pump
discharge port 12. Alternatively or simultaneously the fluid is transported through
connection port 33 to a second pump suction port 21 and a second pump suction region
46 by the combined action of first pump entity 10 and second pump entity 20. Second
pump entity 20 is shown in sectional view B. A second pump inner rotor 26 is operatively
arranged on pump shaft 15 and thus forced to rotate with the pump shaft. This rotation
entrains rotation of a second pump outer rotor in the same direction, which appears
as counterclockwise rotation of both second pump rotors in view B. Said rotation transports
fluid from second pump suction region 46 (15 bar) to second pump discharge region
48 where it is discharged at high pressure (30 bar) through second pump discharge
port 22.
[0032] The high pressure fluid in second pump discharge region 48 exerts a force on second
pump inner rotor 26 whereby the force is determined by the pressure difference between
second pump discharge region 48 and second pump suction region 46 (30 bar - 15 bar
= 15 bar) and the diameter of second pump inner rotor 26. Said force is transmitted
to pump shaft 15 and is shown as second pump shaft force vector 29 normal to a second
pump operational plane of symmetry 45 in view B and points into the plane of Fig.
1 in view 30 (not shown).
[0033] The force exerted by intermediate pressure (15 bar) fluid in the discharge region
44 of the first pump is shown as first pump shaft force vector 19 normal to a first
pump operational plane of symmetry 41 in view A and points out of the plane of Fig.
1 in view 30 (also not shown).
[0034] Figs. 2 - 4 show a dual outlet pressure pump operatively arranged in a hydraulic
control system according to the invention. The hydraulic control system controls a
continuously variable transmission in various operating modes. Arrows indicate oil
flow in a hydraulic line. Crosses on oil line indicate that oil pressure in the line
is maintained at low to medium level by the VDP - typically no significant flow of
oil from the pumps.
[0035] Figure 2 shows a schematic view of a hydraulic control system for a continuously
variable transmission in an "Idle" state. A first pump entity 10 (in this example
a variable displacement pump VDP) and a second pump entity 20 (in this example designated
as boost pump BP) are operatively arranged on a common pump shaft 15 which is driven
by a drive unit 80 which is typically the crankshaft of a combustion engine of a vehicle.
In "Idle" mode drive unit 80 is supposed to run at 600 rpm. The 600 rpm rotation of
pump shaft 15 drives the VDP at approximately 50% of theoretical pump capacity V
th. The VDP transports oil from oil reservoir 90 through oil filter 91 and oil intake
line 92 into low pressure oil line 94. A small fraction of the oil passes through
connection passage 33 to boost pump BP and is transported by the boost pump into high
pressure oil line 96. In "Idle" state all of the oil of high pressure oil line 96
is recycled through oil bypass line 98 to oil intake line 92 because no high pressure
oil is needed by primary pulley (PP) 65 and thus ratio control valve 55 is completely
closed as shown in detail in insert 56.
[0036] In "Idle" state part of the low pressure oil flow passes through valve compartment
50 through torque converter 85 into lubrication section 87 and back to oil reservoir
90. Part of the low pressure oil passes through check valve 54 and oil return line
99 to the oil reservoir 90. A small amount of low pressure oil maintains belt cramping
pressure in secondary pulley 66. Another small part of the low pressure oil is recycled
to the VDP under control of bypass valve 52 from where it is directed to control port
18 of the VDP which in turn controls flow rate of the VDP.
[0037] Fig. 3 is a schematic view of a hydraulic control system for a continuously variable
transmission in a "Speed UP" state of operation. Drive unit 80 is assumed to run at
1500 rpm. During "Speed UP" the VDP runs at 100% of V
th. The ratio control valve 55 is now partially open and the VDP is filling the primary
pulley 65 to increase the gear ratio. The boost pump assists the VDP in reaching and
maintaining a desired (medium) pressure level in the primary pulley 65.
[0038] Fig. 4 shows schematically the hydraulic control system of Figs. 2 and 3 in a "Constant
Speed" state of operation. The VDP runs at a fraction of its V
th and at a relatively low pressure. The primary and secondary pulleys are maintained
at the appropriate level and lockup clutch 86 is engaged. Most of the oil is recycled
over the bypass lines 98.
[0039] Fig. 5 shows the hydraulic control system of Figs. 2, 3 and 4 in a "Speed DOWN" state
of operation. The VDP runs at a significant fraction of its theoretical pump capacity
and part of the oil (at medium pressure) is recycled through bypass lines 98. The
VDP fills the secondary pulley 66 through the cramping pressure control valve 58 to
gradually decrease the gear ratio. The ratio control valve 55 controls the oil flow
out of the primary pulley 65.
[0040] Figure 6 is a series of sectional views showing different embodiments of a variable
displacement vane pump with enhanced discharge port as disclosed in
US 8 118 575 B2. "Gen I" designates an original design and "Gen II" and "Gen III" show proposed alternative
designs of an enhanced discharge port of said variable displacement vane pump. The
most preferable solution shown in "Gen III" requires much extra space in the pump
discharge region. By using a variable displacement vane pump and providing a connection
passage and a connection passage inlet according to the present invention flow behavior
and friction is improved significantly without the extra space requirement of the
"Gen III" solution.
[0041] The invention thus allows a particularly compact construction and relatively low
production costs for a dual outlet pressure pump in a hydraulic control system for
a continuously variable transmission of a vehicle.
List of Reference Numerals
[0042]
- 10
- First Pump Entity
- 11
- First Pump Suction Port
- 12
- First Pump Discharge Port
- 13
- Slide
- 14
- Spring
- 15
- Pump Shaft
- 16
- First Pump Rotor
- 17
- Dual Pump Housing
- 18
- Control Port (of VDP)
- 19
- First Pump Shaft Force Vector
- 20
- Second Pump Entity / Boost Pump (BP)
- 21
- Second Pump Suction Port
- 22
- Second Pump Discharge Port (30 bar)
- 23
- Second Pump (GeRotor) Outer Rotor
- 26
- Second Pump (GeRotor Inner) Rotor
- 29
- Second Pump Shaft Force Vector
- 30
- Sectional View of Dual Pump
- 32
- Connection Passage Inlet
- 33
- Connection Passage
- 34
- Connection Passage Outlet
- 36
- First Pump Rotor Cavity
- 37
- Diaphragm
- 38
- Axial Bore
- 39
- Second Pump Rotor Cavity
- 40
- Pump Axis
- 41
- First Pump Operational Plane of Symmetry
- 42
- First Pump Suction Region
- 44
- First Pump Discharge Region
- 45
- Second Pump Operational Plane of Symmetry
- 46
- Second Pump Suction Region
- 48
- Second Pump Discharge Region
- 50
- Valve Compartment
- 52
- Bypass Valve
- 54
- Check Valve
- 55
- Ratio Control Valve
- 56
- Expanded Sectional View of Ratio Control Valve
- 58
- Cramping Pressure Control Valve
- 65
- Primary Pulley (PP)
- 66
- Secondary Pulley (SP)
- 80
- Drive Unit
- 85
- Torque Converter (T/C)
- 86
- Lockup Clutch
- 87
- Lubrication Section
- 90
- Oil Reservoir
- 91
- Oil Filter
- 92
- Oil Intake Line
- 94
- Low Pressure Oil Line (Plow)
- 96
- High Pressure Oil Line (Phigh)
- 98
- Oil Bypass Lines
- 99
- Oil Return/Dump Lines
- CVT
- Continuously Variable Transmission
- LHPA
- Local High Pressure Area
- NEDC
- New European Driving Cycle (Standard/Richtlinie ECE)
- TCU
- Transmission Control Unit
- VD(V)P
- Variable Displacement (Vane) Pump
- Vth
- Percentage of Theoretical Pump Capacity
1. A dual outlet pressure pump comprising a first pump entity (10) and a second pump
entity (20), whereby a dual pump housing (17) comprises a first pump rotor cavity
(36) and a second pump rotor cavity (39) separated by a diaphragm (37) with an axial
bore (38) and whereby a first pump rotor (16) and a second pump rotor (26) are operatively
arranged on a common drive shaft (15) to convey a fluid,
characterized in that
the angular placement of elements of the first pump entity (10) relative to elements
of the second pump entity (20) about a pump axis (40) is such, that the radial force
exerted by the fluid pressure in a first pump discharge region (44) of the first pump
rotor cavity (36) upon the first pump rotor (16) is opposed in direction to the radial
force exerted by the fluid pressure in a second pump discharge region (48) of the
second pump rotor cavity (39) upon the second pump rotor (26).
2. The dual outlet pressure pump as claimed in claim 1,
characterized in that
the first pump entity (10) and the second pump entity (20) are any combination of
either a hydraulic rotary vane pump or a hydraulic gear pump.
3. The dual outlet pressure pump as claimed in claim 2,
characterized in that
the first pump entity (10) and the second pump entity (20) are angularly aligned about
the pump axis (40) such that a first pump operational plane of symmetry (41) and a
second pump operational plane of symmetry (45) intersect at a pointed angle and the
first pump discharge region (44) of the first pump rotor cavity (36) and the second
pump discharge region (48) of the second pump rotor cavity (39) are provided in opposite
larger quadrants of the intersecting first and second pump operational planes of symmetry.
4. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the first pump discharge region (44) of the first pump rotor cavity (36) and a second
pump suction region (46) of the second pump rotor cavity (39) are hydraulically connected
through a connection passage (33).
5. The dual outlet pressure pump as claimed in claim 4,
characterized in that
said connection passage (33) comprises a connection passage inlet (32) which is located
in the area of highest pressure of the first pump discharge region (44) of the first
pump rotor cavity (36).
6. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the first pump entity (10) is a lower pressure pump and the second pump entity (20)
is a higher pressure pump.
7. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
either the first pump entity (10) or the second pump entity (20) is a variable displacement
pump.
8. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
either the first pump entity (10) or the second pump entity (20) is a fixed displacement
pump.
9. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the first pump entity (10) is a lower pressure higher capacity pump and the second
pump entity (20) is a higher pressure lower capacity pump.
10. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the first pump entity (10) is a rotary vane pump.
11. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the second pump entity (20) is a gerotor pump.
12. The dual outlet pressure pump as claimed in any of the preceding claims,
characterized in that
the axial bore (38) of diaphragm (37) of the dual pump housing (17) comprises a bearing.
13. A hydraulic control system for a continuously variable transmission of a vehicle,
comprising a dual outlet pressure pump as claimed in claim 1.