DE1063032B - Hydraulic control system - Google Patents

Description

The rounding-up concerns one hydraulic rule · tnm rules <Jer Vcrdringang ciaex FJü $ 8Jg · a lijtlratiliiclicuHubvcfiLjilciiinirs · g and with a more agitated steaenrenti! for controlling the hydraulic Flusaigkeitliufuhr did HobvcrändcruiipTOnichtmig. The hydraulic control system is particularly suitable for Künlaalagcnottrieb.

According to the invention throw vöfgescMagCö that the » SttticnxtlÜl Via lines on both sides one in your When the pump is closed.

Compared with hydraulic devices && ea Regelaalagen, sn at d 'a drwcfccßißiJndliches Veutil is provided is € 3 advantageous <iu valve ait the "ötgegetigcteMten end" to the various pressures at din Missed "gaigesetiten pages aafprccheii to lasseo, since the pressures decent at Judges] IVN ^ en büniKn u :: il nevertheless the angle of the swash plate flicht beeißfluisen, K> leofc the training remains constant.

D ^ r kaiio, wcHB d «r Μ <Λοτ elSrfcef beJast«! What makes the increased pressure necessary in the conductors is worth the load factor without rerandering the angle dex swash plate. which is why the drive of constant drcteahi can be maintained.

The experience is further activated by a control valve, between the control valve and the hydraulic lift position, and sudden actuation of the pressure 2 to the hydraulic. Huh \ i; rindtiunpvon "ichtwn | r bd a rüilwii Bewiguug des Stfontnog ^ ieaeni-entils Texhjndert, wddi» BrschlcaiiiEwngi, vaitil from «nc? Hole ^ which a« Ix-iiuiig, from a Huberventil and the hydraulic valve and the hydraulic Mihliilcfjc dex hole gkitbarea V "tUgtied rait Flüisiglrcit.". ritirtriliisvn wid a spring lx $ 1dlt "which presses the valve member into a position in which the valve passage t \ m connection between icta control" til and the hjxlrsuJtschen HtibverindeTut In the event of a sudden flow from the control mechanism, move the valve in such a way that only the valve element around the valve element correctly enters the hydraulic system

At the hand of the drawings a
betSfite! the Eröiidusg bedwiebei. It does

1 shows a nematic representation of a variant of the invention,

2 shows a schematic representation of a part the FJg. 1 with Pampe, Xiotor, Steucn'cntil, BcKhlcuniguafisvcntil anddcktronag ^ tisctoii Vcaülbaeakrecht «sn Cut,

Fig. 3 of the vertical section of the control valve *, Hydraulic control system '

Anirelder:

Sundstrand Machine Tool Co.,
Rockford »HL (V. St. A.)

Representative Dr.-InQ. H. Rusdiie, Beilüi-Fiiedenau,

uc4 DipL-Iag. K. GrcntzenLeig,
Miirufacn 27, PjcazaaaucrstT. 2, patent attorneys

Melviix M. Hiirn, Rociioid, UL (V. St. A.),
itt has been named as Erfiodci

the the Stc ^ erveatUruigschicber and the pressure relief valve in one position shows

Fig. 4 is a view similar to FIG. 3, the> in ue t other position "IGT the SteuerventilnngSchiebei and DAJ pressure relief valve *,

FIG. 5 is a representation similar to that of FIG. 3, which shows a third position of its valve ring seal or the pressure relief valve.

6 shows a vertical section of the control valve, of the ßc * accelerigmg.sxcsiti1s and the eklctramagaetisehen Valve, which the veutik in the eiaea Stellang icigt,

Fig. 7 The representation is identical to that of Fig. 6, shows the accelerator valve and the electromagnetic valve in a different position, and the

Fig. 3 is a circuit diagram, d * i. shows the verÄhic4eßea switching devices with actuation of the ekktreaftpetischen valve and for controlling the pump

In Fig. I a Koeiprc4 * or2 is shown, * s housed in a «croibar trailer can be tmd the noraiaJerweiee vca the distant Trsktonnaschinc 4 ibex a hydraulic transmiwfon sogetrldxiJ is having a hydraulijche Pump 6 with Tc1a2d.tr] idieiti stroke and eiaeti hydnwitischen Motor 8 constant stroke * uniiaBt An electric motor 10 is over a suitable speed ^ » rtduiiergctrkbe 12 for the operation of the Koaapresior 2 angecMoesen if the attacher is ibgtkcf> pclt or if the Turkish screw 4 is not running.

According to FIG. 2, the control device for the pump 6, which is described in detail below, contains a Control valve 14, an accelerator valve 16, and an electromagnetic valve 18.

The pump

The hydraulic pump 6 has a housing 20 which forms a wobble disk chamber 21, a drive shaft 22 in the housing 20 resting in the bearings 24 and 26. One end 28 of the drive shaft 22 can be operatively coupled to the truck machine 4. A drum 30 is keyed to the shaft 22 for rotation therewith, which drum has a series of parallel cylinders 32 circumferentially arranged. A series of hollow pistons 34 are slidably movable within the cylinders 32 and are urged against the swashplate end of the cylinders 32 by internal springs 36. The outwardly extending ends of the pistons 34 are spherical or spherical, as shown at 38, and can form ball and socket connections with the slide plates 40 located on the front of the swash plate 42. The front 42 of the swash plate is made of hardened bearing metal and is seated in a recess 43 in a non-rotatable swash plate 44 so that it can reliably rotate therein with respect to the swash plate. The swash plate 44 is housed in the housing 20 so that it surrounds the shaft 22 and can be tilted, the stroke of the pistons 34 and thus the displacement of the pump being changed.

The pump 6 has an inlet funnel 46, the communicates with an inlet port 47, and an outlet funnel which communicates with an outlet port 49 is in communication, each of the cylinders 32 is provided with cylinder openings 50 extending from the Outlet end of each cylinder 32 extend out so that they alternate with the inlet funnel 46 and the outlet funnel 48 as the drum 30 rotates.

It will be appreciated that upon rotation of drum 30 by shaft 22, one of the cylinders 32 is moved so that its cylinder opening 50 receives a connection with the inlet funnel 46, the Piston moves outward so that it draws hydraulic fluid into the cylinder. If the Drum 30 continues to rotate, the cylinder opening 50 is moved to a position in which it communicates with outlet funnel 48 at which time the piston is through on its discharge stroke the swash plate 44 is moved and thereby the hydraulic Liquid into the discharge hopper 48 and outlet port 49 propels.

In the housing 20 a device is provided which changes the angle of inclination of the swash plate 44, whereby the displacement of the pump 6 is changed, which device is one in the housing 20 located control cylinder 52 contains, which has a movable hollow control piston 54 therein. One inner spring 56 pushes the control piston 54 outward so that the end of the control piston 54 against a shoulder part 57 of the swash plate 44 presses. The swash plate is eccentric for a moment with the tendency to generate this against a vertical or neutral stroke position under overcoming the force of the spring 56 to be preloaded. The relative force of springs 56 and 36 is at rest such that they leave the swash plate in a lifted position, i. H. at an angle of inclination of approximately 2 ° from the vertical.

Between the outlet opening 49 of the pump 6 and an inlet opening 60 of the hydraulic motor 8 a liquid line 58 lies, while a liquid line 62 lies between an outlet opening 64 of the hydraulic motor 8 and the pump inlet port 47 is located. A reservoir 66 for a hydraulic Liquid is connected to line 62 via lines 68 and 70, while a line 72 between the line 62 and the chamber 21 in the housing 20, inside which the swash plate 44 is located.

The control valve 14 responds to the discharge flow of the pump 6 and is equipped with a device provided for controlling the flutter angle by means of the control piston 54. To feel the flow out of pump 6 is an outflow block 76 with a passage 78 into line 58 adjacent the pump inlet 49 placed, and devices to be described later are provided for transmitting the Differences in pressure with respect to the control valve 14 occurring on opposite sides of the passage.

The control valve

According to FIG. 3, the control valve 14 is accommodated in an end cap 79 of the pump housing, which cap has a cylindrical bore 80 which is closed at one end by a plug 81. A ring slide 82 with a bore 82 α can slide in the bore 80 and is pressed therein by a spring 83 in a direction which spring lies between a shoulder 84 present on the ring slide 82 and a spring seat 83 which is adjustable in one end of the Hole 80 is attached. An upper part 82 b of the slide bore 82 α is stepped so that it has a larger diameter than the underlying part of the bore. Retaining rings 85 and 86 are disposed adjacent each end of the slide bore. A hollow pressure relief valve member 87 is slidably mounted in the cavity of the slide 82 and has a main part 87 a, which slide in the bore 82 a, and an upper flange part 87 b, which can slide in the bore 826. The pressure relief valve member 87 is closed at its upper end and is normally pressed upwards against the locking ring 85, so that one end of the slide 82 is effectively closed by means of a spring 88, one end of which is on a cylindrical disc 89 placed on the locking ring 86 rests, while the other end presses against the closed end of the pressure relief valve member 87.

The upper end of the bore 80 of the control valve 14 is in communication with the via a line 90 High pressure side of the passage 78, while the lower end of the bore 80 with the line 58 on the low-pressure side of the passage 78 is in communication via a line 91, so that the control slide 82 in the bore 80 due to the pressure difference that occurs on the opposite sides of the Passage 78 occurs and which results from the discharge flow of the pump 6 is set.

The control valve housing 79 has passages 96 and 98 which connect to various in the Slide 82 and existing in the pressure relief valve member 87 channels and openings at different Positions of the slide 82 and the pressure relief valve member 87 can be obtained. The passage 98 stands with

the control cylinder 52 via a line 110 in connection, while passage 96 communicates with the pump housing via lines 112 and 113 stands. The passage 96 also communicates with the control cylinder 52 via lines 112 and 111 Link.

For a more detailed description of the arrangement of the channels and openings in the control slide 82 and the pressure relief valve member 87, reference is now made to FIGS. 3, 4 and 5, from which it can be seen is that two annular channels 114 and 115 cut into the outer surface of the slide 82 at a distance are those at various positions of the slide 82 with those drilled into the valve housing Passages 96 and 98 can communicate. Extending radially through the slide 82 from the Channels 114 and 115 emanating from openings 116 and 117, respectively. An annular channel 118 is in the inner surface of the slide 82 and is in communication with the outer channel 114 via the opening 116. The pressure relief valve member 87 has an elongated reduced part 119 on the outer circumference, which is always in communication with the opening 116 and the channel 118 in the slide 82 and with the Opening 112 can establish a connection. In the outer periphery of the pressure relief valve member 87 is at a distance from the groove 119 an annular channel 120 is cut, which has a series of openings

121 has, which extend from there through the pressure relief valve member 87, the hollow interior thereof to the low pressure side of passage 78 via line 91, bore 80 and an orifice

122 in the disk 89 is in communication.

Since the variable displacement pump 6 has a substantially constant output power to the Motor 8 must feed with constant displacement, so that the compressor 2 is driven at a constant speed the control valve 14, which is responsive to the output flow of the pump 6, is provided, to change the position of the swash plate 44 by the control piston 54, whereby the stroke the pump 6 is increased when the speed of the pump drive of the truck engine 4 is is decreased, and the stroke of the pump 6 is decreased as the rotational speed of the vehicle engine 4 increases.

Before the truck engine 4 is started to operate the pump 6, the control slide 82 in the upper part of the bore 80 is displaced by the spring 83, and the valve member 87 is controlled by the spring 88 pressed against ring 85 in the upper part of sleeve 82 as shown in FIG. When the drum begins to rotate, liquid is pumped through the outlet funnel 48. When the initial pressure in the high pressure line 90 is not sufficient to overcome the force of the spring 83, the remains Valve slide 82 and the valve member 87 in its upper position (FIG. 4), so that the low-pressure line 91 via the openings 121, the channel 120, the openings 117, the channel 115 and the passage 98 is in communication with the line 110. Therefore, discharge liquid from line 58 flows through the Control valve 14 and through line 110 to control cylinder 52 and displaces control piston 54 against the swash plate 44, whereby its angle and thus the displacement of the pump 6 is increased. When the pump flow increases, increases Likewise, the pressure difference on opposite sides of the opening 78, and if the If the pressure in the high-pressure line 90 increases, the control slide 82 is pushed downward, the Ring 85 in the sleeve 82, the valve member 87 moves with the sleeve 82 until the pressure in the plant on the Low pressure side of port 78 plus the pressure of spring 83 equal to the pressure on the high pressure side the opening 78 is. At this point (see Fig. 2) the stroke of the pump 6 for the operation of the hydraulic Motor 8 suitable with constant displacement. With one stopped at this neutral point Movement of the spool 82, the channel 115 is no longer in communication with the passage 98, and the further flow of pressure fluid to the control cylinder 52 is shut off. These Condition continues until the speed of the carriage machine 4 either increases or decreases, thereby causing the pump 6 to operate faster or slower.

When the speed of the pump 6 increases, the output power of the pump begins to increase, which process increases the pressure difference at the opening 78 and causes the spool 82 to move downward to the position of FIG. 3 and the channel 114 with both passages 96 and 98 is ^/ Getting Connected in \. When this occurs, fluid is directed from the control cylinder 52 through line 110, passage 98, passage 114, passage 96, lines 112 and 113 to the pump housing. This emptying of the liquid from the control cylinder 52 allows the pressure moment to move the swash plate 44 towards a lower stroke position and thus reduce the stroke of the pump piston 34. If the stroke of the piston 34 has been reduced sufficiently to compensate for the increased drive speed, the control slide 82 is shifted upwards into the neutral position and blocks further removal of liquid from the control cylinder 52.

When the speed of the pump 6 decreases, the pump output flow also decreases and reduces the pressure differential across port 87, thereby allowing the spool 82 is moved from the neutral position by the spring 83 upwards until the channel 115 with the Passage 98 is in communication, as shown in Fig. 4

+5 set. This process releases hydraulic fluid of the lower pressure line 91 through the openings 122 and 121, the channel 120, the openings 117, the channel 115, the passage 98 and the line 110 in the control cylinder 52, whereby the control piston 54 after pressed outside and the angle of the swash plate 44 and the stroke of the piston 54 is increased, wherein a constant output flow from the pump 6 to the hydraulic motor 8 is obtained.

The pressure relief valve

The pressure relief valve 87 described earlier is provided in order to reduce the displacement of the pump 6 and thus the pressure in the system when the pressure in the system rises to a predetermined, relatively high value, as can occur when a driven element is blocked or when an obstacle occurs in a discharge line. If the hydraulic system works below a predetermined pressure value, which would represent the upper limit for safe and effective operation, the pressure relief valve 87 remains inactive and rests on the locking ring 85 under the action of the spring 88, as in FIGS. 2, 3 and 4 shown. However, if the pressure exceeds a predetermined value, the overpressure

valve member 87 is actuated, as shown in FIGS.

When the pressure in the system exceeds the predetermined value (see Fig. 4), it enters the upper part of the bore 80 via the high pressure line 90 (Fig. 4). The pressure relief valve member 87 is a stepped valve member, the upper end 87δ has a larger cross section than the lower end of the \ ^T entilgliedes. The fluid pressure at the upper part of the pressure relief valve member 87, when the pressure exceeds the predetermined maximum, is sufficient to overcome the force of the spring 88 and begins to move the pressure relief valve member 87 down into the spool 82, thereby establishing the connection between the channel 120 and the openings 117 blocked and control fluid from the line

110 and the control cylinder 52 is cut off. The pressure relief valve member 87 continues its downward movement in the control slide 82 until the position of FIG. 5 is reached, at which the elongated Channel 119 on the pressure relief valve member 87 is in communication with the openings 116 and 117, which with communicating with passages 96 and 98 via channels 114 and 115, respectively. This process allows that from the control cylinder 52 liquid through the line 110, the channel 115, the openings 117, the elongated channel 119, the openings 116, the channel 114, the lines 112 and 113 to the pump housing 21 flows, wherein the control piston 54 controls the pump 6 in a stroke position that of the load the spring 88 is determined, and the pressure of the system is reduced to below the predetermined value.

The accelerator valve

A rapid increase in the tilt angle of the swash plate 44 and thus a sudden increase to prevent load or pressure surges, which is usually the case with sudden shock waves from Control fluid would enter the control piston 54, the acceleration valve 16 is provided.

The accelerator valve 16 is disposed adjacent the inlet to the control cylinder 52 and includes a cylindrical bore 126 located in the end cap 79 (FIGS. 6 and 7). Two spaced apart Passages 127 and 128 extend into the control cylinder 52 starting from the bore 126 with a valve member 129 slidably resting in the bore 126 and downwardly by a spring 130 is pressed. A passage 131 communicates with the upper end of the bore 126, while a Passage 132 communicates with the lower end of bore 126, with an overflow opening 133 is arranged between the passages 131 and 132 and is in communication with the bore 126. Of the Passage 132 is via the liquid line 100 with the passage 98 in the control valve 14, the lines

111 and 112 and the passage 133 with the chamber 21 in the pump housing via the lines 111,

112 and 113 connected.

The accelerator valve 129 has a side passage 134 extending therethrough and which can connect to the passage 128 in normal operation at which the valve member 129 blocks the overflow opening 133 shown in FIG. 2. Another passage 135 extends extends in the longitudinal direction of the valve member 129 from the lateral passage 134 and opens to the bottom surface of the valve member 129.

It will be apparent that the accelerator valve just described has a number of useful functions exercises in the work of the regulator. When the car engine is started, the control valve 14 Demand a maximum displacement of the pump 6 and direct pressure fluid into the line 110 (see Fig. 4 and 6). Unless there is pressurized fluid in the passage and line 150 (See Fig. 6), the acceleration valve member 129 is moved up into the position of FIG. 6, and the The main part of the control fluid is passed through line 111. A leak around the valve member allows control fluid to flow into the cylinder 52 and the control piston 54 slowly afterwards moved to the right, increasing the pump stroke. If the movement of the control piston 54 stops, so A pressure is created in the control cylinder 52 and thus in the line 150. When this occurs, becomes that part of the accelerator valve 129 which is exposed to the pressures in the latter line, subjected to a force equal to that which the liquid in line 110 on the opposite Part of the valve member exerts, whereby the spring 130 after the acceleration valve member can move below, which process blocks the line and a direct connection between the Establishes fluid in line 110 and the interior of the control cylinder. On the other hand, if the machine If the truck is already idling and slowing down, it slows down too the pump, and the control valve demands a sudden increase in the pump stroke by the pump output to bring to the predetermined state. Such a sudden increase in the pump stroke at the lower point of the engine speed / min would tend to throttle the engine, but with a control surge the accelerator valve is used to move this up and thereby the main part of the to store the control pressure supplied to the control cylinder.

It is therefore understood that the accelerator valve for a gradual increase in the pump stroke instead of a sudden increase in size. When the compressor load when accelerating is very heavy, the task of the acceleration valve is to accelerate the motor (and thus of the compressor) over an extended period rather than suddenly causing no severe Load on the belt drive, the gearbox etc. for the pump is generated.

The electromagnetic valve

To control the pump 6 to the stroke zero and to automatically stop the hydraulic motor 8 under certain conditions the electromagnetic valve 18 is provided. That usually closed electromagnetic valve 18 can release the pressure in the control cylinder 52 when energized thus allowing the swash plate 44 to assume its zero stroke position.

The electromagnetic valve 18 consists of a housing 140 (Figs. 6 and 7) having an inlet 141 and has an outlet 142 which are communicated with each other through an opening 143 in communication. A diving iron 144 rests in an electromagnet core 145, which lies in a coil 146 with the connections 147, wherein the immersion iron 144 is forced by a spring 149 to close the opening 143 when the solenoid 146 is not energized during the normal cooling work of the system. Inlet 141 is in communication with the passage 131 of the accelerator valve 16

via a liquid line 150, while an outlet 142 is in communication with the chamber 21 of the pump housing 20 via the lines 112 and 113, so that when solenoid 146 is energized, port 143 is opened and allows liquid to flow is passed from the control cylinder 52 via the solenoid valve 18 to the pump housing chamber 21, whereby the pump 6 is controlled. '

If the coil 146 is excited, the immersion iron 144 from the opening 143 becomes that shown in FIG. 6 Position retracted, allowing control fluid from control cylinder 52 to pass the passage 127, the upper part of the bore 126, the passage 131, the conduit 150, the passage 141, the opening 143, the passage 142 and the lines 112 and 113 flows to the pump chamber 21, which The process allows the swash plate 44 to assume a substantially basic position. When the output flow from the pump 6 through the opening 78 is reduced in this way, the ring slide becomes 82 pushed up into the position of increased stroke, the channel 115 in connection is brought to the passage 98 so that discharge liquid from the low pressure line 91 to the accelerator valve 16 flows through line 110. By withdrawing control fluid from the S expensive cylinder 52 through the upper part of the bore 126, the discharge liquid flowing into the lower part of the bore 126 from the conduit 110 the work of the spring 130 is overcome so that the accelerator valve member 129 is located in the bore 126 moved upward, whereby the passage 128 to the control cylinder 52 is closed. In this way only the leakage of the discharge liquid downstream of the valve member 129 into the control cylinder 52 becomes withdrawn by the electromagnetic valve 18. Since it is possible, that the pump is in this position for is operated for an indefinite period of time, very little leakage fluid will enter the pump chamber 21 to dissipate the heat generated when the liquid pounds through the rotating parts will. In order to avoid overheating of the pump 6 and its possible failure, the upward movement opens of the acceleration valve member 129, which closes the passage 128, the overflow opening 133 and allows a substantial part of the discharge liquid from the line 110 through the lower part of the bore 126, the overflow opening 133 and the lines 111, 112 and 113 flows to the pump chamber 21, whereby the pump 6 is cooled.

It should also be noted that the electromagnetic valve does not control all liquid needs, which is passed into the line 110 from the control valve, but only the pressure in the cylinder 52 and the passage 150 needs to reduce in order to allow the .Swashplate to zero stroke shifts, and to cause the accelerator valve member to move upward. Therefore the electromagnetic valve may be smaller in size than would otherwise be required.

7 shows the position of the control elements at the moment when the electromagnetic valve 18 is de-energized and causes the immersion iron 144 to close the opening 143. The spool 82 is in its upper open-S division and allows the pressure of the system to the acceleration valve 16 from the low pressure line 91 through the openings 121, the channel 120, the openings 117 _; channel 115, passage 98 and line 110 is fed. However, the acceleration valve member 129 is still in its upper position and closes the passage 128 to the control cylinder 52, so that only the leakage fluid enters the control cylinder 52. When the electromagnetic valve 18 is closed, however, the pressure in the control cylinder 52 cannot be removed, which is why there is a gradual increase in the pressure in the control cylinder 52, which process causes the control piston 54 to gradually increase the angle of the swash plate 44 and thus the hydraulic motor 8 slowly accelerated. When the control piston reaches the end of its migration, the pressure in the control cylinder increases so that it is equal to the control input pressure and the accelerator valve member 129 is moved down into the open position, which provides a direct connection between the passages 132 and 128 via the Accelerator valve ports 135 and 134 manufactures.

^The hydraulic motor

As can be seen from Fig. 2, the hydraulic

■ Lical motor 8 with constant stroke a housing 165, which has a rotatable shaft 166 supported therein in suitable bearings, such as the typical bearing arrangement 167, rests. On the shaft is a drum-like housing 168 with a circumferentially and axially arranged therein annular row of cylinders 169, each of which has a piston 170 slidable therein owns. In the housing 165, a bearing 171 is mounted at a predetermined angle, which the Surrounding shaft 166 and which carries a swash plate 172, the pistons 170 against the swash plate 172 can press. Is fluid from the hydraulic pump 6 through line 58 into the inlet port 60 of the motor 8 is pumped, the liquid is pumped into the cylinders 169 of the drum housing 168, which are in communication with the inlet opening 60, and the pistons 170 against the angularly inclined Swash plate 172 is forced, causing rotation of the drum housing 168 and the Wellel66 is effected. An end portion 173 of the shaft 166 can be connected to the shaft of the compressor 2 of the refrigeration unit and, if desired, by suitable drive devices with blowers or ventilators (not shown), which are located in the refrigeration department. When the drum housing 168 rotates, The pistons 170 move inwardly into their cylinders 169 from the fixed swash plate 172 pressed, which process the liquid from the cylinders 169 and the outlet port 64, with which the Cylinder 169 come into connection, in the liquid line 62 presses.

An additional feature of the hydraulic motor 8 is that when there is no drive for the hydraulic pump 6 is present and the compressor 2 is driven by the electric motor 10, the hydraulic motor 8 does not work as a hydraulic pump, eliminating the need for a Clutch device between the hydraulic motor 8 and the compressor 2 is switched off. When the compressor 2 is driven by the electric motor 10, the shaft 166 and the drum housing become 168 of the hydraulic motor 8 is also driven. With this construction, however After one full revolution of the drum housing 168, all pistons 170 through the swash plate 172 forced inward into their cylinder 169, where they are driven by the centrifugal force of the rotation of the drum housing 168 are recorded. This centrifugal force is enough to push the fluid in the

909 580/233

To overcome reservoir 66 which would tend to hold the pistons against swash plate 172 so that motor 8 would act as a pump when driven by electric motor 10. In those cases where the reservoir is at a relatively high location, a control valve in the engine outlet line 62 can be provided.

Claims (8)

Patent claims: 1. Hydraulic control system for regulating the displacement of a liquid pump with a hydraulic stroke changing device and with a movable control valve for regulating the liquid supply to the hydraulic stroke changing device, characterized in that the control valve (14) via lines (90, 91) on both sides one in the outlet of the Pump (6) arranged throttle point (76) is connected. 2. Hydraulic control system according to claim 1, characterized by an acceleration valve (16) which is connected between the control valve (14) and the hydraulic stroke changing device ( 52,54) and sudden liquid pressure surges to the hydraulic stroke changing device (52, 54) when the Flow control valve (14) prevents which acceleration valve (16) from a bore (126) which cuts a line (110) between the control valve (14) and the hydraulic stroke change device ( 52,54) from a slidable in the bore (126) Valve member (129) with fluid passages (134,135) and a spring (130) which presses the valve member (129) into a position in which the valve passages (134,135) establish a connection between the control valve (14) and the hydraulic stroke change device (52, 54) produce, with sudden liquid pressure surges from the control valve (14) move the valve member (129) so that only Lec Kiquid enters the hydraulic stroke change device around the valve member (129). 3. Hydraulic control system according to claim 1 or 2, characterized in that between the Acceleration valve (16) and the control valve (14) a pressure relief valve (87) is provided, which in a manner known per se when the fluid pressure in the system rises to one predetermined value of fluid from the hydraulic stroke changing device (52, 54) to reduce the output of the pump (6) to zero. 4. Hydraulic control system according to claim 3, characterized in that the pressure relief valve (87) regulates the line (110) between the control valve (18) and the hydraulic stroke change device (52, 54) and opens when energized to drain fluid from the hydraulic stroke change device. 5. Hydraulic control system according to claim 2, 3 or 4, characterized by an overflow passage (111, 112, 113), through a leakage path around the acceleration valve member (129) , which acceleration valve member is when a substantial pressure difference occurs in the line (110) and moves in the hydraulic stroke change device (52, 54J ) and directs control fluid into the spill passage (111, 112, 113) , the leakage path allowing restricted flow of control fluid to the hydraulic stroke change device (52, 54) to create fluid pressure therein, and wherein the spring (130) and the leakage path together generate a pressure which acts on the accelerator valve member (129) in a direction in which the connection between the line (110) and the hydraulic stroke change device (52, 54) is restored when the therein occurring pressures are approximately the same. 6. Hydraulic control system according to claim 4 and 5, characterized in that the capacity of the electromagnetic valve (18) is not greater than the amount of liquid in the leakage path. 7. Hydraulic control system according to one of the preceding claims, characterized in that the control valve (14) consists of a housing (79) with openings and a sleeve (82) with a closed end which can slide in the housing and is supported by a spring (83 ) is printed in one direction, which sleeve (82) has outer annular grooves (114,115) which establish a connection between the openings (96, 98) in the housing (79), that openings (116,117) extend inwards through the sleeve ( 82) extend from the grooves (114, 115) so that the opposite ends of the valve housing (79) are connected to the throttle point (76) in the pump outlet, so that the position of the valve sleeve (82) in the housing (79) of the Pressure difference at the throttle point (76) is influenced, and that the valve housing openings (96,98) are in communication with the hydraulic stroke change device (52, 54) . 8. Flydraulic control system according to claim 7, characterized by a pressure relief valve (87), which is slidably disposed in the control sleeve (82). Considered publications:
German patent specification No. 842 307. For this purpose 2 sheets of drawings © 909 580/233 7.59