DE2352739A1 - TORQUE LIMITER FOR PUMPS WITH VARIABLE DISPLACEMENT - Google Patents

Description

PATENT LAWYERS
Dipl.-Phys. JÜRGEN WEISSE · Dipl.-Chem. Dr. RUDOLF WOLGAST

- D 5602 LANGENBERG BÖKENBUSCH41 2352739

P.O. Box 86 Telephone: (02127) 4019 Telex: 8516895

Patent application

Richard Joseph Ifield, 95 Gopeland Road,

Beecroft, Hew South Wales, Australia

Torque limiter for pumps with variable displacement

The present invention relates to hydraulic pumps and Motors that consist of a base body and a rotor which is surrounded by an external support and attached to it, wherein the base body is provided with an inlet and an outlet for the liquid to be pumped and the rotor has a plurality of pistons carries that at, equal angular intervals and parallel or at an angle are arranged to the axis of rotation of the rotor and move back and forth when the rotor is rotated and thereby liquid pump. A pump of this type is hereinafter referred to as a piston pump labeled with variable "displacement.

One embodiment of this piston pump on which the invention can be used, consists of a rotatable cylinder block device, in which the pistons are equally spaced around the cylinder block axis; parallel to this axis run cylinder bores. The cylinder block is with a drive device connected in such a way that the drive device and the cylinder block rotate at the same speeds.

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As the drive shaft rotates, the distance between each of the pistons and the mouth surface changes steadily. While the first half of the revolution each piston moves away from the orifice surface and during the other half of the revolution towards this; the inlet opening is aligned when the piston moves away, the outlet opening is aligned aligned as the piston moves closer.

The object of the present invention is to provide a piston pump to create with variable displacement with a torque limiter that is simple and functional and easy to manufacture is inexpensive, which can be easily adjusted or controlled in operation to suit any available from a prime mover Moment to be able to be adjusted.

According to the invention this object is achieved in that a hydr © - statically balanced slide bearing for the pump rotor and pressure-sensitive devices that respond to the hydrostatic bearing pressure are provided.

When using piston pumps with variable displacement for power transmission it is usually necessary to provide a hand control to set the maximum pump displacement, as well as, Provide override devices, one by which the pump displacement can be reduced when the transfer pressure exceeds a predetermined value in order to protect the force-transmitting parts against overload, and another to reduce the pump displacement when the drive torque exceeds a predetermined value by one to prevent overloading of the motor and the electric motor, which one drives the pump.

The theoretical drive torque of the pump is the product of the Pump displacement and the pressure difference, so that the torque limiter

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based on this fact »Until now, torque limiters contained a valve tappet, which is acted upon by the pump output pressure and actuates an adjusting valve that regulates the pump displacement via an adjusting motor, with the movements of the tappet taking place against a spring load, which is triggered by a on the movements of the adjusting motor responsive driver is changeable, so that the spring load of the pump displacement is inversely proportional. Moment limiters of this type are complex in construction and expensive to manufacture; they can only be set correctly on special test stands that are equipped with dynamometers for torque measurement. This torque limiter can not according to a proportional relationship to the respectively available, the changing moments w adapted ground, as supplied from gasoline engines, which are operated over a range of throttle openings ₀

The invention is based on the knowledge that the bearing load on the rotor support in pumps with variable displacement Product of the pump displacement and the operating pressure, so that the bearing load is proportional to the theoretical drive torque is. According to the invention is therefore responsive to the moment Bearing load converted into a pressure medium pressure, so that the pressure medium pressure corresponds to the theoretical drive torque of the 'Pump is proportional.

The subject of the invention includes the pressure sensitive device Switching valve with one under the bearing pressure against the pressure one Spring movable member, as well as an actuated by means of the switching valve control valve for controlling the adjustment device for the pump displacement. The torque can be controlled as a function of the speed of the prime mover driving the pump and one with a negative preload and one with the speed of the prime mover and the driving force variable load applied member; intended"

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In the torque limiter according to the invention, a stabilization device can also be used be provided in the form of a piston-cylinder device connected to the adjustment device; the switching valve is with a means of the stabilization device as a function of the rate of change of the pump displacement variable pressure medium applied to increase the stability.

In the torque limiter according to the invention is by means of the switching valve the effect of the other control means acting on the control valve can be overcome and the drive torque of the pump through the change in the pump displacement can be limited independently of the setting of the other control means.

According to the invention, the control valve is designed as a direction-controlling setting valve which has an axially movable valve body o In a first axial end position of the valve body, the setting device can be controlled by means of the setting valve according to the setting of the other control means mentioned, while in a second axial end position of the valve body, the pump output is controlled by means of the Adjustment valve and the adjustment device can be reduced. The valve body can be moved into the second end position by a pressure change as a result of the actuation of the switching valve. The control valve can also consist of a combined, manually operated and automatic adjusting and direction-controlling setting valve, which has a manually operated sleeve provided with through-openings and a rotatable valve body driven by a setting motor, which is axially displaceable as a result of the actuation of the switching valve _O

Advantageously, the torque limiter according to the invention the switching valve has a valve tappet which responds to the bearing pressure and which is supported on a spring-loaded valve part,

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where the spring load is used to set a maximum torque is mechanically adjustable.

In the following, the invention is described with reference to a special design of an axial piston pump which can be driven forward and backward beyond its center point; however, it can equally well be applied to other embodiments of variable displacement pumps ₀

The invention is further set out below in relation to a particular one Type of a hydrostatically balanced plain bearing described, but it can also be used with other designs with equal success Can be used by hydrostatically balanced bearings where the hydrostatic pressure supports the load responsive to the moment. To describe the mode of operation of the invention in connection with other controls, a suitable, complete control described, however, the invention is not limited to the type and details of this control or the adjustment devices associated therewith.

An embodiment of the invention is described in detail below with reference to the figures?

Fig. 1 is a longitudinal section through an axial piston pump, in which the invention can be used;

.Fig. Figure 2 shows an end view of the stationary orifice surface the pump shown in Fig. 1;

Figure 3 is a diagrammatic representation of a pump controller in one embodiment of the invention;

Fig. 4 shows a preferred embodiment of the control valve;

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Patent application P 23 52 739.1 Richard Joseph Ifield ? 352739

SUBMITTEDJ

Supplement to page 6 of the description immediately following the description of the figures of Fig. 6:

Fig. 7) S and 9 represent sections along the lines and 8 and 9 in Fig. 4 respectively.

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Mg ₀ 5 graphically represents the working range of a torque limiter according to the invention which responds to the machine speed;

FIG. 6 shows one possibility for realizing the control characteristics shown in FIG

According to FIG. 1, the cylinder drum 1 of the pump contains nine axial cylinders with pistons 2, which are formed via a ball joint 5 and flat Plain bearing surfaces "rest against an angle-adjustable swash plate 4 and with a plain bearing mounting plate 5 in Contact with the "surface to be held".

The cylinder rotor is a mouth surface 6 below the. Pressure one Number of springs 7, which on the drive shaft 8 on the Act thrust bearing 9.

The swash plate 4 is located on a partially cylindrical body 10 which is in an end part 11 of the housing is stored, the angle of the swash plate being adjusted of the piston 12 is adjustable with an adjusting motor by means of a rack 13 which is in engagement with the teeth is located on the partially cylindrical body 10. By adjusting the piston with the adjusting motor, the cylindrical Body 10 can be rotated in each direction up to an angle of about 20 °, whereby the stroke of the piston and the direction of flow changed through the passage openings

In the event that the body 10 is in the position shown and the pump clockwise looking from the end of the

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Drive shaft 8 is driven, the exit takes place from the opening A in Fig. 2, which is correspondingly called the front high " pressure opening ". When the body 10 in the opposite Direction is inclined, the exit occurs through the opening B, which is correspondingly referred to as the rear high pressure opening will,,

The drive shaft 8 is designed to be highly adaptable, so that the cylinder drum 1 is free in its alignment with the flat mouth surface 6 and is held on four partially spherical guide bodies Swash plate 4 is inclined in the direction shown _o If the swash plate is inclined in the opposite direction, the bearing load would rest on the sliding body 15. No theoretical, sideways-directed loads occur on the cylinder drum, so that a sliding body shown in the cut-open part of FIG. 2, which is arranged on each side, is only used for holding purposes.

The sliding bodies H and 15 are hydrostatic against the bearing loads matched. You can e.g. use the connection points marked with C and D via nozzle openings with the high pressure side be connected. The closed area of the spherical surfaces of the sliding bodies is sufficiently large for the requirements at the maximum pump displacement. The required hydrostatic equalization pressure becomes increasingly lower than the muzzle pressure, when the pump displacement is decreased; under these conditions, the sliding body works with a small margin on its Spherical surface, whereby the resulting leak creates a suitable pressure drop at the narrowed opening.

The inside of the pump housing is kept at the same pressure which also prevails at the mouth on the Hdeder pressure side, so that the

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Bearing load is the product of the muzzle pressure difference and the tangent is proportional to the angle of the swash plate. The driving torque the pump is theoretically proportional to the product of these two terands, so that the hydrostatic Pressure on the G-guide body proportional to the theoretical drive torque This hydrostatic pressure is the result of the invention used on the loaded plain bearing as a signal for the torque limiter.

The two ends of the adjusting cylinder are shown with the connection points marked E and F and the various with the letters A, B, 0, D, E and F in Fig. T and 2 designated Connection points are designated in the same way in the diagram of the control system according to FIG. 3.

According to FIG. 3, a low-pressure pump 17 is connected on the inlet side to a storage vessel 18; its outlet pressure is determined by the setting a low-pressure-side relief valve 19 limited., The pump delivers directly into the interior of the housing of the piston pump with variable displacement, from where the liquid passes through one of the check valves 20 or 21 of the respective low-pressure port is fed o When turned clockwise and forward delivery, there is high pressure at port A. and the opening B is acted upon by the low-pressure pump through the check valve 20 «,:

From the pump openings A and B outgoing lines have check valves 22 and 23, which are connected to one another downstream and the selected maximum pressure via throttles 24 and 25 to the. hydrostatically balanced sliding H or supply 15 through the connection points C and D, as described above in connection with FIG. 1 ₀

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The respective maximum pressure is determined by the check valves 22 and 23 the central bore of a manually "operated changeover valve 26 supplied, which furthermore contains a narrow bore, and at one end a central through-bore which communicates with the storage vessel 18 stands.

Two bores 28 and 29 in the G housing 27 of the manually operated changeover valve are connected to the cylinders of the adjustment device 12 of the transfer pump via a control valve 30 and the connection points Ξ and ¥. The manually operated reversing valve 26 is shown in a position in which maximum pressure is supplied to the connection point E to the setting device, while the connection point i ^{1 is} connected to the storage vessel via the bore 29. This causes the adjusting piston to move into the Pig. 1 position shown maximum pump displacement moved. An outward movement of the switching valve 26 causes a reversal of the pressures at the connection points E and F, so that the adjusting piston 12 moved into the other extreme pitch

The control valve 30 contains a control body 31 with an enlarged piston 32 at one end, which is slidable within a cylinder 33 and is under the pressure of a leather 34, which is opposite to the position shown »The spring chamber and the end of the control body 31 remote therefrom are with the storage vessel 18 in connection _o The output of the low pressure pump 1? is connected to the cylinder 33 via a throttle 35 so that the control element 31 is moved against the pressure of the spring 34 into the position shown, in which it does not influence the actuation of the setting motor corresponding to the adjustment of the manually operated reversing valve 27.

The bores 36 and 37 of the control valve 30 are with the openings A or B of the transfer pump -connected. With discharge

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of the cylinder 33, the control body 31 moves opposite to the direction shown and separates the bores connected to the manually operated changeover valve 27 therefrom and establishes a connection between the pump openings A and B to the connection points Ί? or _o E of the adjusting motor cylinder ₀

The opening A is the high pressure opening for the forward drive, so that an adjustment of the control body 31 causes the piston 12 of the adjustment motor to reduce the pump displacement in the case of forward drive, but this cannot cause a movement beyond the pump displacement 0 to take place because then the hole B would become the high pressure port ₀ Correspondingly, the operation when the hand-operated valve is adjusted inversely going on.

When overridden, the pump works as a motor and when the switch valve is set forwards, port B becomes a high-pressure port. An adjustment of the control body 31 then causes the adjusting piston to increase the pump displacement, as is desired in overdrive conditions _e

When the pump is turned counterclockwise, it is only necessary to swap the connections of openings A and B with bores 36 and 37 «.

In most transfer pump applications with variable Displacement it is necessary to switch off the pump at a predetermined maximum pressure in the area outside the end points to provide the piston movement in order to avoid overloading the pump, as well as a shutdown at a predetermined maximum drive torque of the pump in order to prevent overloading of the drive machine of the pump.

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A switching valve device 38 includes two small plungers 39 and 40, which are supported on valve bodies 41 and 42, which by adjustable springs 43 and 44 are held under pressure in their seat and close bores that connect to the cylinder 33- des Steaerventils are connected? the outlet chambers of the switching valve are connected to the storage vessel.

A feed line transmits the respectively higher pressure from the port A or B to the end of the plunger 39, so that when the pressure is too high the valve 41 opens, and opens the outlet of the cylinder 33, whereby the pump outside an end position comes to a standstill ₀

The pressures on the G-guide bodies 14 and 15 are controlled by the check valves 45 and 46 fed to the band of the plunger 40, so that this is responsive to the hydrostatic pressure on the sliding body. the the loaded bearing supported in each case. The force on the plunger 40 therefore responds to the drive torque of the pump, if this Pressure becomes too high, the valve opens and releases the outlet of the cylinder 33 of the control valve and limits it in this way the drive torque of the pump by changing the pump displacement

Sound the high pressure on the ·. Pompenauslaßöffnungen operated controls are prone to instability, particularly at high gains., D _e h. _e low pump displacement, the invention also includes a stabilizing device that operates in response to the rate of change in pump displacement. A typical Ausfülirungsbeispiel this part of the invention is shown in the Magramm ge s divides "

Piston 47 is in the manner shown with a driver roller 48 provided, which is a crouch 49 on the piston of the adjustment motor is applied ,, Preferably, the Uocken is shaped so that the Movements of the piston 47 relative to the adjustment motor 12 after a

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inverse function of the pump displacement takes place. The outer end of the cylinder for the piston 47 is connected to the inside of the pump housing by a central bore and is therefore subject to the pressure generated by the low-pressure pump, which keeps the driver roller in contact with the lock Switching valve 38 and * is connected to the storage vessel via a throttle 51 "The pressure difference at the throttle 51", which is created by the movements of the piston 47, acts on the enclosed pistons and 53 in such a way that the load on the valves 41 and 42 is changed _e

If one of the valves 41 or 42 opens and limits the pump pressure or the drive torque of the pump, the pressure difference at the throttle 51 a force to close the valve made available. A reduction in pressure on the Plungers 39 and 49, which close the associated valve allowed, causes the creation of a pressure difference at the throttle 51, which thus provides a force to open the valve represents. In this way, this device provides a guide member to stabilize the automatic control depending on the speed of the change in the pump displacement dar β *

In many variable displacement pump applications, it is desirable to use a hand control to vary the maximum pump displacement and to provide devices that override the maximum pressure and torque. Pig. 4 shows a valve which can replace the valves 27 and 30 in I ¹ Ig ₅ , 3 and which allows manual control of the displacement

A manually operated control lever 54 rotates a sleeve 55 provided with openings in a housing 56 _o A rotatable valve part 57 within the sleeve provided with openings has a

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toothed drive arch 58 which is driven by a gear 59 attached to the body 10 in Fig. 1 or by the rack on the piston 12 of the adjustment motor. In any case, the gear chamber is in communication with the interior of the pump housing and is acted upon by the pressure of the low-pressure pump 17. This pressure acts on an annular area of the valve body driven by the teeth, which via a throttle 61 with a cylinder 60 on the opposite Normally the piston in the cylinder 60 is under the pressure acting on the different surfaces in the position shown, but the toothed rotatable valve body moves to the left in the drawing when the cylinder 60 is released. This corresponds to the cylinder 33 in FIG. 3, the release event ile can be similar to those of the switching valve 38 in FIG. 3 and the connection K corresponds to the same connection in the diagram of FIG. 3.

Directional rotary selector valves of this type are well known. As shown in the drawing, they usually have Bores for each of the different pressures with through holes through the sleeve in diametrically opposite one another Are arranged in pairs in order to avoid laterally directed loads on the valves,

The openings marked with A and B are with the similarly designated openings of the transfer points in connection. The openings marked E and F are in correspondingly connected to the ends of the cylinder of the adjusting motor »The opening marked G- is connected to the respective Maximum pressure connected, which is similarly marked in Fig. 3 is. The opening marked H is connected to the storage vessel, which is constantly connected to the end of the cylinder that holds the Valve 57 contains, communicates, and through a central bore with an annular chamber that has a diameter that

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the outer diameter in the sleeve 55 is the same.

In the normal operating position shown, a rotation of the valve sleeve a connection between the passage openings E and F of the adjusting cylinder and the respective maximum pressure opening G or the storage vessel opening H. The adjustment of the piston of the adjusting motor brought about by this closes the ports G and H so that the valve normally operates as a position responsive controller. Under under these conditions the passage openings A and B are closed,

If one of the override valves 4-1 or 42 in Pig. 3 is open, they release the cylinder 60 and cause the control valve body 57 to slide in an asial direction to the left. As a result, the openings H and 6- are separated from their connection with the valve recesses and the openings A and B are released. The opening A is then connected to an adjusting cylinder of the adjusting motor via the opening F and the opening B is connected to the other adjusting cylinder via the opening E. This valve therefore works in a similar way to that in connection with I ¹ Ig. 3 foesctaielaieaae control valve 3O ₀

The each which loads the valve 42 to limit the torque ₉ is provided with an adjusting screw in the illustration. Of course, this screw can be replaced by a plunger operated by means of a camshaft * connected to _{the control of the prime mover 9} so that the driving torque of the pump becomes a function of the setting of the control of the prime mover

A preferred method of controlling the drive torque of the pump as a function of setting the power control of the prime mover is to ensure that the controlling moment is a controllable function of the prime mover speed increases until the torque setpoint line meets the line of

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cuts available torque from the prime mover. This is "shown by way of example by the curves in FIG. 5. The curves a to a _r represent the torque at the output of the prime mover at a specific throttle valve opening or a specific delivery rate of the fuel pumps in diesel engines . The curve Ta represents the line of a controlled torque represents ₅ that increases with the square of the engine _{speed 9} xf with an additional negative constant ₉ so that for engine speeds below 15 $ of the maximum speed the torque load is the value 0 $ and increases to 100 $ at 40 $ of the maximum engine speed »The actual ar- . The operating conditions of the controlled machine exist at the intersection of the a and b curves «,

The curve Id ₁ represents a minimum setting for the torque control and the curve b _{2 represents} a maximum setting for different power requirements on the drive machine, whereby "any other curve can run between these limits"

line The possibility to achieve this control characteristic is shown in -Figo 6, which showed a torque limiter, the low-pressure pump 17s, the storage vessel 18 and the low-pressure side relief valve 19

The Yerbindungspunkte marked with letters to the torque limiter are J _P abuts the leitlagern G of responsive to the torque hydrostatic pressure in the one IC ₂ at the prevailing control pressure of the control valve 30 in Fig _o 3 or Torrichtung shown in lig _o 4 ₉ and L ₉ on which the Stabilisierungsclriiek from the cylinder 50 in Figo 3 is _Θ

An adjustable passage opening 62 is built into the outlet channel of the low-pressure pump 17. The pressure drop at this opening is at the piston 63 against the force of a spring 64 at ₉

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which closes the valve. The spring 64 generates the desired negative constant. The pump 17 is driven by the prime mover driven so that the "pressure at point J, which is the driving torque

2
is proportional to the pump, is given by K ₁ Ή -K ₂ , where U is the machine speed, Kp the negative constant and K- changes with the setting of the power control on the prime mover, so. that thereby the lines of the controlled moment correspond to lines b., and b _? are generated in Fig _O 5. ,.

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Claims (1)

Claims M ₀ ) torque limiter for limiting the drive torque "in a piston pump with variable displacement, characterized in that a hydrostatically balanced sliding bearing (H, 15) for the pump rotor (1) and pressure-sensitive devices (30; 38; 54- responsive to the hydrostatic bearing pressure) 61; 62-64) are provided _o Torque limiter according to Claim 1, characterized in that the pressure-sensitive device has a switching valve (38) one under the bearing pressure against the pressure of a spring (43, 44) ″ movable member (41, 42), and a means of the switching valve actuated control valve (30} 54-61) for controlling the adjustment device (12) for the pump displacement. 3 · torque limiter according to claim 2, characterized in that the torque is a puncture of the speed of the one driving the pump Drive machine is controllable and that one with a negative preload (64) and one with the speed the driving machine and the driving force variable load-applied member (63) is provided. 4ο torque limiter according to claim 2, characterized in that a stabilization device in the form of a piston-cylinder device (47, 50) connected to the adjustment device (12) 409818/0373. is provided and that the switching valve (38) with a variable by means of the Stabiiisierungsvorrichtung as a function of the rate of change of pump displacement! fluid pressure is applied to increase the stability ₀ Torque limiter according to claim 2 _9, characterized in that the action of the other control means acting on the control valve (30-54-61) can be overcome by means of the switching valve (38) and the drive torque of the pump can be overcome by changing the S ¹ UmPenverdrängung independently of the setting of the other tax means is limited " 6ο torque limiter according to claim 5 »characterized in that the control valve is designed as a direction-controlling adjusting valve (30? 54 = 61), that the adjusting valve has an axially movable valve body (31 I 57), that in a first axial end position of the valve body the adjusting device ( 12) can be controlled by means of the adjusting valve according to the setting of the other control means mentioned ₉ that in a second axial end position of the valve body the pump output is reduced by means of the adjusting valve and the adjusting device and that the valve body is caused by a pressure change as a result of the actuation of the switching valve (38) can be moved into the second end position «, - ο torque limiter according to claim 6 _S, characterized ₉ that the control valve consists of a combined, manually operated and automatic adjustment and direction-controlling adjustment valve, a manually operated sleeve (55) provided with openings and a rotatable one - 19. « 4098 18/0379 ta by an adjusting motor driven valve body (57) ", which as a result of the actuation of the switching valve (38) axially displaceable is.to 8. torque limiter according to claim 5 _9, characterized in that the switching valve (38) has a valve tappet (39 * 40) responsive to the bearing pressure ₉ which is supported on a spring-loaded valve part (41 ₉ 42) ,? and that the spring load (439 44) for setting a maximum torque is mechanically adjustable ₀ 409 818/0379 ■ Blank page