Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
  • F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
  • F04B1/26—Control
  • F04B1/30—Control of machines or pumps with rotary cylinder blocks
  • F04B1/32—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block
  • F04B1/324—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/002—Hydraulic systems to change the pump delivery
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/08—Regulating by delivery pressure

Definitions

• An adjusting device according to the preamble of claim 1 emerges from DE-AS 1 958 768.
• 7 of this document shows an adjusting device with an actuating piston, which at the same time forms the valve sleeve for the control valve.
• a valve piston is in turn axially movable in the axially movable valve sleeve, the valve sleeve being acted upon by a control pressure at one end.
• the valve piston is displaced axially, so that a first control edge increases the signal pressure in a control volume and thereby axially displaces the valve sleeve serving as the control piston in the same direction, so that the control edge is closed again.
• the actuator that adjusts the displacement volume of the piston mechanism is also adjusted by the same path by which the valve piston and the valve sleeve have been axially displaced.
• a return spring moves the actuating piston in the opposite direction and a second control edge connects the actuating volume to a tank connection. This relieves the actuating volume and the valve sleeve serving as the actuating piston is displaced axially in the same direction as the valve piston.
• the pressure chamber for the control pressure is separated from a gas volume by a flexible partition, so that the control pressure is buffered for a certain time.
• a disadvantage of the known adjusting device is that the valve sleeve and the valve piston of the control valve can only be produced with the required precision with a limited axial length. Since the axial displacement of the actuating piston and the valve sleeve directly predetermine the adjustment of the actuator of the piston machine, the actuating path for the actuator is relatively small. Either the swash plate of the axial piston machine can therefore only be adjusted within relatively small limits, or an appropriate gear ratio is required.
• the invention is therefore based on the object of specifying an adjusting device for adjusting the swash plate of an axial piston machine in a swash plate construction, in which the adjustment path of the control piston is independent of the adjustment path of the valve piston of the control valve.
• the invention is based on the knowledge that a structural separation of the control piston and the control valve enables a relatively large adjustment range of the control piston to be achieved with a relatively small adjustment range of the valve piston of the control piston.
• the necessary feedback between the control piston and the valve piston of the control valve does not take place in a form-fitting manner as in the prior art via the valve sleeve of the control valve, but in a force-locking manner via a return spring connecting the control piston to the valve piston of the control valve.
• the solution according to the invention enables an extremely compact structure that can be easily integrated into a receiving bore in the housing of the axial piston machine.
• actuating piston in a pot-shaped manner so that the actuating piston receives the return spring and a spring plate connected to the valve piston of the control valve.
• a connecting channel for connecting the actuating volume to the control edges of the valve piston is preferably provided in the stationary valve sleeve.
• the valve sleeve can also have a throttle in order to connect the connection channel to the tank connection in a throttled manner and to relieve the control volume.
• the valve piston preferably has a through hole in order to apply the signal pressure to the valve sleeve on both sides, so that the position of the valve sleeve is independent of the signal pressure.
• the valve sleeve of the control valve is preferably pressed by a pressure spring against an adjustable stop, so that the axial position of the valve sleeve is adjustable.
• the stop can be formed, for example, by an eccentric bolt.
• the control force acting on the control piston of the control valve is preferably generated by an electromagnet, in particular a proportional magnet, or an electric motor, in particular a stepper motor.
• the electromagnet or electric motor can engage the valve piston via a tappet at the end opposite the return spring.
• FIG. 1 shows a section through an axial piston machine, on which an embodiment of the adjusting device according to the invention is provided;
• Fig. 2 is an enlarged view of the embodiment of the adjusting device according to the invention.
• Fig. 3 is a hydraulic block diagram of the adjustment device according to the invention.
• Fig. 1 shows an axial section through an axial piston machine 1 in swash plate construction, in which an adjusting device 2 according to the invention is provided.
• the basic structure of an axial piston machine 1 in swash plate construction is known, so that the following description can be limited to the essential components.
• a shaft 3 is rotatably mounted on a first bearing 4 and on a second bearing 5 in a housing 6 of the axial piston machine 1.
• the housing 6 of the axial piston machine 1 is divided into a base body ⁇ a and a cover body 6b screwed to the base body 6a.
• a cylinder drum 7 is rotatably connected to the shaft 3.
• the cylinder drum 7 there are cylinder bores 8 arranged offset on a pitch circle, in which pistons 9 are axially displaceable.
• the pistons 9 are connected to slide shoes 11 via ball joint connections 10 and are supported via the slide shoes 11 on a swash plate 12 designed as a swivel cradle.
• the stroke of the pistons 9 in the cylinder bores 8 is predetermined by the swivel angle ⁇ of the swash plate 12.
• the swash plate designed as a swivel cradle is shown twice in FIG. 1 in its neutral position and in a position swiveled by the swivel angle ⁇ .
• the cylinder drum 7 is held in contact with the control body 13 by means of a spring 22.
• the spring 22 is supported on the cylinder drum 7 via a first ring 23 and on the shaft 3 via a second ring 24.
• the cylinder drum 7 is axially movable relative to the stationary shaft 3 via a key-and-groove connection.
• the adjusting device 2 according to the invention is used to pivot the swivel disk 12.
• the adjusting device 2 is integrated in a receiving bore 16 of the housing 6 and consists of an actuating piston 18 connected to the swashplate 12 via the ball joint connection 17, which is guided axially in the receiving bore 16, one in the control bore 19 inserted into the receiving bore 16 and an actuator 21 which specifies a control force for a valve piston 20 of the control valve 19.
• the control valve 19 and the control piston are arranged axially offset from one another in the receiving bore 16.
• FIG. 2 An embodiment of the adjusting device 2 according to the invention is shown enlarged in FIG. 2.
• the exemplary embodiment is essentially the same as the exemplary embodiment shown in FIG. 1, with the difference that an adjusting screw 30 is provided in the exemplary embodiment shown in FIG. 2, the function of which is still to be discussed. Otherwise, elements that correspond to FIG. 1 are provided with corresponding reference numerals in order to facilitate the assignment.
• a spherical sliding block 31 is in sliding contact with the actuating piston 18 axially guided in the receiving bore 16 of the housing 6 and, together with a spherical recess of the swash plate 12 shown in FIG. 1, forms the ball joint connection 17.
• the sliding block 31 could also slide against the swash plate 12 and the spherical recess could be formed in the actuating piston 18.
• the actuating piston 18 is cup-shaped, so that its wall 32 surrounds a cavity 33 which receives a return spring 34 for the valve piston 20 of the control valve 19, which will be described in more detail.
• the return spring 34 is clamped between the bottom 35 of the cup-shaped actuating piston 18 and a spring plate 39, which has a first end 40 of the Valve piston 20 of the control valve 19 is connected.
• the spring plate 39 has an axial longitudinal bore 41 which is placed on a pin-shaped projection 42 of the valve piston 20.
• the return spring 35 is supported on an outside step 43 of the spring plate 39.
• an outer annular groove 44 is provided, which is connected to the cavity 33 via a radial channel 68.
• the annular groove 44 also serves as a hydraulic stop.
• the diameter of the cavity 33 is larger than the diameter of the spring plate 39, so that the spring plate 39 is received by the cavity 33 of the actuating piston 18 in the maximum swivel pitch shown in FIG. 2.
• actuating volume 45 which also includes the cavity 33 of the actuating piston 18, an actuating pressure predetermined by the actuator 21 via the control valve 19 is established.
• the control valve 19 consists of a stationary, sleeve-shaped connection body 46, in which a tank connection 47 and a pressure connection 48 are formed.
• the connector body 46 is sealed off from the housing 6 by a seal 49, for example an O-ring.
• a valve sleeve 50 Inside the connection body 46 there are a valve sleeve 50, in which the valve piston 20 is axially movable.
• the valve piston 20, the valve sleeve 50, the connecting body 46 and the receiving bore 16 of the housing 6, in which the control valve 19 is inserted, are aligned coaxially to one another.
• a connecting channel 51 in the exemplary embodiment consisting of a longitudinal bore 52 designed as a blind bore and a transverse bore 53.
• the connecting channel 51 is connected to the tank connection 47 via a throttle 54.
• the valve sleeve 50 has a first ring channel 55, while the valve sleeve 50 has a second ring channel 56 in the area of the pressure connection 48.
• the valve piston 20 has a first annular space 57 which is connected to the pressure connection 48 via a first radial bore 56 and which is sealed via a sealing section 58 and a radial projection 59 of the valve piston 20. Furthermore, the valve piston 20 has an annular space 61 which is connected to the tank connection 47 via a second radial bore 60 and which is sealed via a sealing section 62 and a radial projection 63 of the valve piston 20.
• a first control edge 64 is formed at the transition from the first annular space 57 to the projection 59, while a second control edge 65 is formed at the transition from the second annular space 51 to the projection 63.
• the actuator 21 exerts a control force via a tappet 66 on the second end 67 of the actuating piston 20 opposite the return spring 34.
• the actuator 21 exerts a control force on the valve piston 20, which shifts the valve piston 20 to the right in FIG. 2, the first control edge 64 is closed and the second control edge 65 connects the tank connection 47 via the connecting channel 51 to the actuating volume 45 Control volume is therefore relieved via the tank connection 47 and the control pressure decreases. Consequently, the adjusting piston 18 is shifted to the left in FIG. 2 and the swash plate 12 swings out in the direction of a larger displacement volume of the axial piston machine. At the same time, the return spring 34 is pretensioned by the movement of the actuating piston 18 and a counterforce arises counter to the control force of the actuator 21, which increases with increasing displacement of the control piston 18 to the left in FIG. 2.
• valve piston 20 When an equilibrium position is reached such that the control force exerted by the actuator 21 corresponds to the counterforce exerted by the return spring 34, the valve piston 20 is in its equilibrium position, so that neither the control edge 64 nor the control edge 65 opens and opens in the actuating volume 45 sets a constant signal pressure.
• the hydraulic fluid slowly escapes from the actuating volume 45 via the throttle 54.
• the escaping hydraulic medium is continuously tracked by slightly displacing the actuating piston 20 via the control edge 64.
• each control force predetermined by the actuator 21 corresponds to a defined one Position of the adjusting piston 18 and thus a defined swivel angle ⁇ of the swivel plate 12.
• actuator 21 is an electromagnet, in particular a proportional magnet, the force or deflection of which is proportional to the exciting electrical current.
• an electric motor in particular a stepper motor, is also suitable as the actuator 21, which transmits a control force proportional to the rotational position of the electric motor to the tappet 66, for example via a spindle and a spring arranged between the tappet 66 and the spindle.
• the control force exerted on the end 47 of the actuating piston 20 can also be a hydraulic force which prevails in a pressure chamber formed at the end 67 of the valve piston 20 and acts on the left end face of the valve piston 20 in FIG. 2.
• an adjustable stop 70 is provided in the exemplary embodiment shown in FIG. 2, a pressure spring 71 holding the valve sleeve 50 in contact with the adjustable stop 70.
• the relative position of the control edges 64 and 65 in relation to the transverse bore 53 of the connecting channel 51 can be adjusted by the adjustable stop 70.
• the adjustable stop 70 consists of an adjusting screw 30 screwed into the housing 6 with a screw head 72 and lock nut 73.
• An eccentrically mounted washer 74 is located on the end of the adjusting screw 30 which projects into the receiving bore 16.
• valve piston 20 there is a through-channel 76 in the valve piston 20, which passage Control volume 45 connects to the spring chamber 77, which receives the pressure spring 71.
• the pressure on the left of the valve sleeve 50 is the same as that on the right of the valve sleeve 50, and the signal pressure in the actuating volume 45 has no influence on the axial position of the valve sleeve 50.
• FIG. 3 For a better understanding of the invention, a hydraulic basic circuit diagram of the adjusting device 2 according to the invention is shown in FIG. 3. Elements that have already been described are also provided with the same reference numerals here.
• the axial piston machine 1 which works as a hydraulic pump in the exemplary embodiment, is driven via the shaft 3, draws in hydraulic fluid from a tank 80 and promotes this
• Adjustment device 2 connected. In contrast, the tank connection 47 of the adjusting device 2 is over
• Pressure relief valve 82 connected either to the tank 80 or to the working line 81. In the basic position of the pressure relief valve 82 shown in FIG. 3, the pressure relief valve 82 connects the tank connection 47 to the tank 80.
• control piston 18, the control valve 19 with the valve piston 20, the return spring 35 arranged between the control piston 18 and the valve piston 20 and the actuator 21 designed as a proportional magnet in the exemplary embodiment can also be seen. It is also shown that the volumes to the left and right of the control piston 20 are connected to one another via the passage channel 76.
• the pressure relief valve 82 serves to limit the pressure prevailing in the working line 81 to a maximum pressure. If the pressure prevailing in the working line 81 exceeds that which can be set by means of the spring 83 Maximum pressure, the pressure-limiting valve 82 connects the tank connection 47, instead of the tank 80 to the working line 81, so that the actuating volume 45 is not relieved towards the tank 80, but rather the working pressure prevailing in the working line 81 is applied. The axial piston machine 1 is therefore pivoted back by the adjusting piston 18 in the direction of the minimum displacement volume V min or in the direction of the neutral position.
• V max in FIG. 3 denotes the maximum displacement volume that occurs when the actuating piston 18 in FIG. 2 strikes its left stop.
• the invention is not limited to the exemplary embodiments shown, but can also be used for an adjusting device 2 in a different design or
• Axial piston machines 1 are used in a different design. It should be emphasized that the adjustment path of the
• Actuating piston 18 is independent of the displacement of the valve piston 20 and is only a very small one
• Adjustment of the valve piston 20 is a very large one
• Adjustment path of the actuating piston 18 can be reached.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Reciprocating Pumps (AREA)
• Control Of Positive-Displacement Pumps (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=7925374

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (45)

Citations (9)

Family Cites Families (5)

• 1999
  • 1999-10-12 DE DE19949169A patent/DE19949169C2/de not_active Expired - Fee Related
• 2000
  • 2000-09-29 JP JP2001529585A patent/JP4691299B2/ja not_active Expired - Fee Related
  • 2000-09-29 DE DE50011655T patent/DE50011655D1/de not_active Expired - Lifetime
  • 2000-09-29 US US10/110,575 patent/US6725658B1/en not_active Expired - Lifetime
  • 2000-09-29 WO PCT/EP2000/009566 patent/WO2001027472A1/de not_active Ceased
  • 2000-09-29 EP EP00971304A patent/EP1220990B1/de not_active Expired - Lifetime

Patent Citations (9)

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