GB1592443A

GB1592443A - Double hydraulic pump

Info

Publication number: GB1592443A
Application number: GB373278A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1977-02-08
Filing date: 1978-01-30
Publication date: 1981-07-08
Also published as: DE7703577U1

Description

(54) A DOUBLE HYDRAULIC PUMP (71) We, ROBERT BOSCH GmbH., a German company of Postfach 50, 7000 Stuttgart 1, Germany., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a double hydraulic pump comprising two adjustablestroke pump units.

In such a pump, each pump unit is provided with a rotor accommodating fluid displacement members and each rotor is arranged in a separate pump chamber.

Usually a feed pump is also provided for supplying extra hydraulic fluid to the pump chambers surplus to working fluid requirements so as to prevent cavitation occurring during operation of the pump. This extra fluid supply also provides lubrication and some degree of cooling and may also be used for flushing purposes.

However, under certain critical operating conditions, for example when one pump unit is delivering and the other is idling, the volume of extra hydraulic fluid reaching the idling pump unit may not be sufficient for adequate cooling of that unit.

This can lead to breakdown of the pump.

In a double hydraulic pump in accordance with the invention, comprising two adjustable-stroke pump units, in which each unit is provided with a rotor accommodating fluid displacement members and each rotor is arranged in a separate pump chamber, each pump chamber is provided with an inlet for cooling fluid and one of the inlets is provided with a throttle.

With that arrangement, cooling fluid can be supplied by the feed pump directly to the idling pump unit unthrottled whilst the delivering pump receives cooling fluid through the throttle and may also receive additional fluid from the idling pump unit. In that manner the entire pump can be adequately cooled even under the most critical operating conditions.

In a preferred form of double pump in accordance with the invention, the inlets to the pump chambers are connected together by a duct provided with a common inlet for cooling fluid to both pump chambers. The feed pump is then connected to the common inlet.

Preferably, the throttle is a bore in a plate arranged across the inlet to one of the pump chambers and may be arranged across the mouth of the inlet within the pump chamber.

If desired, flushing fluid, also derived from the feed pump, may be supplied from the low pressure side of one pump unit to the pump chamber of the other pump unit, through a flushing valve.

In one specific flushing arrangement, the outlet from the flushing valve leads to a flushing duct forming a connection between the pump units, that end of the flushing duct terminating at the said one pump unit being blocked and the other end of the flushing duct terminating at the said other pump unit being open for the passage of flushing fluid to the pump chamber of the said other pump unit.

Preferably, the end of the flushing duct terminating at the said one pump is blocked by a plate. The outlet from the flushing valve may lead to one end of the flushing duct, preferably that end thereof which is blocked by the metal plate.

To enable the double pump to be operated in various ways, it is preferable for each pump unit to be provided with its own flushing valve, in which case, the outlet from each flushing valve leads to a respective end of the flushing duct.

To provide for the passage of cooling and/or flushing fluid between the pump chambers, at least one bore may be provided between the pump chambers. The pump chambers are preferably separated from one another by a housing wall, in which case, the duct provided with the common inlet, the flushing duct and the said bore pass through the housing wall.

As a further aid to operating the double pump in various ways, the throttle plate and the blocking plate may be made removable so that they can be transferred from their position in one pump unit to the corresponding position in the other pump unit.

In order that the invention may be clearly understood and readily carried into effect, one embodiment of a double hydraulic pump in accordance therewith will now be described with reference to the ac companying drawings in which, Figure 1 is a longitudinal section through a double hydraulic pump and Figure 2 is a section taken on the line Il-Il in Figure 1.

As can be seen from Figure 1, the double hydraulic pump comprises two adjustable pump units A and B arranged in a com- mon housing 10, the respective pump chambers 12 and 13 of which are separated by a housing wall 11. A longitudinal bore 14, in which is fixed a control journal 15, is formed in the wall 11. A rotor 16 is arranged on the left hand portion 15' of the control journal, the rotor 16 accommodating displacement members (not shown) the ends of which projecting out of the rotor slide on a radially movable ring 17 for the purpose of stroke generation and stroke variation. The rotor 16 is driven by a coupling disc 18 which is fixed to a driving shaft 19 which extends through the hollow interior of the control journal 15.

A rotor 20 is arranged on the right hand portion 15" of the control journal 15, the rotor 20 accommodating displacement memhers (likewise not illustrated) the ends of which extending out of the rotor slide on a radially displaceable ring 21 for the purposc of stroke generation and stroke variation. The rotor 20 is driven by a coupling disc 22 which is rigidly mounted on the driving shaft 19. The driving shaft 19 is mounted in a cover 23 which closes the pump chamber 13. The pump chamber 12 is closed by a cover 24. An outlet bore 25, from which a discharge line 26 leads to a reservoir 27, passes through the lower part of the cover 24.

As can be seen from Figure 2, two transversely extending bores 28 and 29 which issue into the bore 14, are formed in the housing wall 11. Where they enter the bore 14, the bores 28 and 29 are in communication, through control ports (not shown) arranged in the control journal 15.

with the pump units A and B. A bore 30 proceeds from the bore 28 and issues into a duct 31 to which a feed pump 33 is connected through a line 32. The feed pump 33 draws hydraulic fluid from the reservoir 27 and delivers it into the interior of the housing 10 for cooling, flushing and make-up purposes. A bore 34 proceeds from the bore 29 and issues into the duct 31.

A non-return valve 35 is arranged in the bore 30 and a non-return valve 36 is arranged in the bore 34. The non-return valves 35 and 36 are arranged to open in a direction away from the duct 31 towards the bores 28 and 29.

A bore 37, in which is arranged a feed pump pressure limiting valve 38 (Figure 2) passes through the duct 31 and leads to a duct cunecting the pump chambers 12 and 13 together. This duct comprises a bore 39 proceeding to the left and a bore 40 proceeding to the right from the bore 37 above the pressure limiting valve 38. The bore 39 forms an inlet to the pump chamber 12 and the bore 40 forms an inlet to the pump chamber 13. The bore 37 forms a com- mon inlet for cooling fluid to both pump chambers 12 and 13 through their respective inlet bores 39 and 40. The bore 39 issues into an annular space 41 between the wall 11 and the rotor 16, forming part of the pump chamber 12. The bore 40 likewise issues into an annular space 42 between the wall 11 and the rotor 20, forming part of the pump chamber 13.The two annular spaces 41 and 42 are connected to one another by two bores 43 and 44 formed in the wall 11 and which extend parallel to the bores 39 and 40 but above the latter. A plate 45, preferably of metal, is provided with a throttle bore 46 and is arranged within the pump chamber 12 across the mouth of the inlet bore 39, thus closing the latter except for the throtle 46.

Above the control journal 15, a flushing duct 47 passes through the housing wall 11 and connects axially widened portions 48 and 49 of the two annular spaces 41 and 42 of the pump units 12 and 13 together.

A bore 50, forming an outlet from a valve block 51 on the top of the housing 10, leads to the widened portion 48. A bore 52, forming an outlet from a valve block 53, likewise on the top of the housing 10, leads to the widened portion 49. The portion 48 is completely isolated from the annular space 41, the rotor 16 and the ring 17, by a plate 55, preferably of metal.

Flushing valves are provided in the valve blocks 51 and 53 in known manner.

The pump units A and B can be set to different delivery rates or to zero delivery rates, so that they idle, and even reversed independently of one another by radial displacement of the stroke rings 17 and 21.

The critical operating condition with regard to lubrication and cooling is provided when the pump unit B is idling and the pump unit A is delivering. Then, as a rule, there is an insufficient amount of hydraulic fluid available for lubrication and cooling of both pump units.

The feed pump 33 continually delivers hydraulic fluid into the duct 31 through the line 32. When both pump units are idling, that is at zero delivery, only the leakage oil from the pump is replaced through the non-return valves 35 and 36.

The remainder of the fluid from the feed pump 33 passes through the feed pump pres sure limiting valve 38, through the bores 39 and 40 into the housing 10 and from the latter discharges through the outlet bore 25 in the cover 24 and the line 26 to the reservoir 27. The throttle 46 in the plate 45 covering the mouth of the bore 39 is so dimensioned that only a partial flow of fluid from the feed pump 33 can pass directly to the pump unit A. The remainder of the fluid from the feed pump 33 arrives in the pump chamber 13 of the pump unit B, through the unthrottled inlet 40. The fluid then flows through the pump chamber 13, through the bores 43 and 44 to the pump chamber of the pump unit A. The fluid then flows to the reservoir 27 through the outlet bore 25 in the cover 24.

When the double pump is operating, one of the bores 28 or 29 (28 for example) is connected to the reservoir 27 and the other bore (29) is connected to a load. Thus, a pressure difference prevails in the bores 28 and 29 so that in the above-mentioned critical operating condition the flushing valve arranged in the valve block 51 is opened and connects the low pressure side (28) through a low pressure limiting valve (not shown) and the bore 50 to the pump unit A. However, direct communication with the pump chamber 12 is interrupted by the metal plate 55 so that the stream of flushing fluid discharging through the bore 50 (feed flow - leakage oil etc.) is diverted to the pump chamber 13 of the pump unit B through the bore 47. The fluid then flows through the pump chamher 13, the bores 43 and 44 to the pump unit A.Flushing with fluid from the low pressure side is likewise effective for other operating conditions of the pump, that is to say, with either pump unit idling and the other pump unit delivering or with both pump units delivering.

If necessary, the double pump can be converted from clockwise operation of the shaft 19 to anti-clockwise operation thereof.

For this purpose, the driving shaft 19 and the bearing covers 23 and 24 are interchanged and the metal plates 45 and 55 are arranged on the opposite side of the wall 11 to restrict the flow of fluid into the pump chamber 13 and give priority to fluid flow ing into the pump chamber 12.

WHAT WE CLAIM IS: 1. A double hydraulic pump comprising two adjustable-stroke pump units, each unit being provided with a rotor accommodating fluid displacement members, each rotor being arranged in a separate pump chamber, each pump chamber being provided with an inlet for cooling fluid and one of the inlets being provided with a throttle.

2. A double hydraulic pump according to claim 1, in which the inlets to the pump chambers are connected together by a duct provided with a common inlet for cooling fluid to both pump chambers.

3. A double hydraulic pump according to claim 2, in which the common inlet is provided with a pressure limiting valve.

4. A double hydraulic pump according to any preceding claim, in which the throttle is a bore in a plate arranged across the inlet.

5. A double hydraulic pump according to claim 4, in which the plate is arranged across the mouth of the inlet within the pump chamber.

6. A double hydraulic pump according to any preceding claim, in which a flushing valve is provided for supplying fluid from the low pressure side of one pump unit to the pump chamber of the other pump unit.

7. A double hydraulic pump according to claim 6, in which the outlet from the flushing valve leads to a flushing duct forming a connection between the pump units, that end of the flushing duct terminating at the said one pump unit being blocked and the other end of the flushing duct terminating at the said other pump unit being open for the passage of flushing fluid to the pump chamber of the said other pump unit.

8. A double hydraulic pump according to claim 7, in which the end of the flushing duct terminating at the said one pump is blocked by a plate.

9. A double hydraulic pump according to claim 7, or claim 8, in which the outlet from the flushing valve leads to one end of the flushing duct.

10. A double hydraulic pump according to claim 9, in which each pump unit is provided with a flushing valve the outlet from which leads to a respective end of the flushing duct.

11. A double hydraulic pump according to any preceding claim, provided with at least one bore for the passage of cooling fluid between the pump chambers.

12. A double hydraulic pump according to any one of claims 2 to 5 or 7 to 11, in which the pump chambers are separated from one another by a housing wall and the said duct, the said flushing duct and the said bore pass through the housing wall.

13. A double hydraulic pump according to claim 4, claim 5 or claim 8, in which the throttle plate and the blocking plate are removable for transfer to correspond ing positions in either of the pump units.

14. A double hydraulic pump according to any one of claims 4, 5, 8 or 13, in which

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

leakage oil from the pump is replaced through the non-return valves 35 and 36.

The remainder of the fluid from the feed pump 33 passes through the feed pump pres sure limiting valve 38, through the bores

39 and 40 into the housing 10 and from the latter discharges through the outlet bore 25 in the cover 24 and the line 26 to the reservoir 27. The throttle 46 in the plate 45 covering the mouth of the bore 39 is so dimensioned that only a partial flow of fluid from the feed pump 33 can pass directly to the pump unit A. The remainder of the fluid from the feed pump 33 arrives in the pump chamber 13 of the pump unit B, through the unthrottled inlet 40. The fluid then flows through the pump chamber 13, through the bores 43 and 44 to the pump chamber of the pump unit A. The fluid then flows to the reservoir 27 through the outlet bore 25 in the cover 24.

When the double pump is operating, one of the bores 28 or 29 (28 for example) is connected to the reservoir 27 and the other bore (29) is connected to a load. Thus, a pressure difference prevails in the bores 28 and 29 so that in the above-mentioned critical operating condition the flushing valve arranged in the valve block 51 is opened and connects the low pressure side (28) through a low pressure limiting valve (not shown) and the bore 50 to the pump unit A. However, direct communication with the pump chamber 12 is interrupted by the metal plate 55 so that the stream of flushing fluid discharging through the bore 50 (feed flow - leakage oil etc.) is diverted to the pump chamber 13 of the pump unit B through the bore 47. The fluid then flows through the pump chamher 13, the bores 43 and 44 to the pump unit A.Flushing with fluid from the low pressure side is likewise effective for other operating conditions of the pump, that is to say, with either pump unit idling and the other pump unit delivering or with both pump units delivering.

If necessary, the double pump can be converted from clockwise operation of the shaft 19 to anti-clockwise operation thereof.

For this purpose, the driving shaft 19 and the bearing covers 23 and 24 are interchanged and the metal plates 45 and 55 are arranged on the opposite side of the wall

11 to restrict the flow of fluid into the pump chamber 13 and give priority to fluid flow ing into the pump chamber 12.

WHAT WE CLAIM IS: 1. A double hydraulic pump comprising two adjustable-stroke pump units, each unit being provided with a rotor accommodating fluid displacement members, each rotor being arranged in a separate pump chamber, each pump chamber being provided with an inlet for cooling fluid and one of the inlets being provided with a throttle.
2. A double hydraulic pump according to claim 1, in which the inlets to the pump chambers are connected together by a duct provided with a common inlet for cooling fluid to both pump chambers.
3. A double hydraulic pump according to claim 2, in which the common inlet is provided with a pressure limiting valve.
4. A double hydraulic pump according to any preceding claim, in which the throttle is a bore in a plate arranged across the inlet.
5. A double hydraulic pump according to claim 4, in which the plate is arranged across the mouth of the inlet within the pump chamber.
6. A double hydraulic pump according to any preceding claim, in which a flushing valve is provided for supplying fluid from the low pressure side of one pump unit to the pump chamber of the other pump unit.
7. A double hydraulic pump according to claim 6, in which the outlet from the flushing valve leads to a flushing duct forming a connection between the pump units, that end of the flushing duct terminating at the said one pump unit being blocked and the other end of the flushing duct terminating at the said other pump unit being open for the passage of flushing fluid to the pump chamber of the said other pump unit.
8. A double hydraulic pump according to claim 7, in which the end of the flushing duct terminating at the said one pump is blocked by a plate.
9. A double hydraulic pump according to claim 7, or claim 8, in which the outlet from the flushing valve leads to one end of the flushing duct.
10. A double hydraulic pump according to claim 9, in which each pump unit is provided with a flushing valve the outlet from which leads to a respective end of the flushing duct.
11. A double hydraulic pump according to any preceding claim, provided with at least one bore for the passage of cooling fluid between the pump chambers.
12. A double hydraulic pump according to any one of claims 2 to 5 or 7 to 11, in which the pump chambers are separated from one another by a housing wall and the said duct, the said flushing duct and the said bore pass through the housing wall.
13. A double hydraulic pump according to claim 4, claim 5 or claim 8, in which the throttle plate and the blocking plate are removable for transfer to correspond ing positions in either of the pump units.
14. A double hydraulic pump according to any one of claims 4, 5, 8 or 13, in which

the said plate is a metal plate.
15. A double hydraulic pump according to any preceding claim in which the pump chamber with the inlet provided with the throttle is also provided with an outlet bore for connection to a reservoir.
16. A double hydraulic pump substantially as herein described with reference the accompanying drawings.

A n n E TY AS T O PA