Hydraulic unit

A hydraulic system with a hydraulic pump driven directly by an internal-combustion engine reduces the dimension, weight and number of component parts used in the state of the art systems while optimizing energy exploitation. A plurality of elements, one of which is a cam shaft adjusting device, are supplied with hydraulic pressure fluid by one and the same pump. A series of simplified hydraulic connections enables equivalent devices to be driven simultaneously by one or more pump circuits.

BACKGROUND OF THE INVENTION 
The invention generally relates to a hydraulic system with a hydraulic pump 
which is directly driven by an internal-combustion engine and more 
particularly to a hydraulic system with a hydraulic pump whose delivery 
rate is controlled at the inlet or at the outlet. 
SUMMARY OF THE INVENTION 
A hydraulic unit of this kind is described in German Patent Application No. 
4,033,105. The operating fluid (hydraulic pressure fluid) of the pump, 
respectively of the combination of pumps, may be constituted by the 
lubricating agent of the internal-combustion engine, but alternatively a 
separate hydraulic pressure fluid circuit may be envisaged as well. If 
however, in an automotive vehicle for which a hydraulic system of this 
kind is provided, a plurality of hydraulic consumers exist and each 
consumer is supplied with hydraulic pressure fluid independently of all 
others, considerable constructional efforts, enormous space requirements 
and elevated costs are required. 
It is, therefore, the object of the invention to further develop a 
hydraulic system of the kind under review in such a way that considerable 
reduction in cost, space requirements, weight and energy consumption are 
achieved. 
This object is attained by utilizing the pump, which has as up to now 
exclusively been utilized for the variable adjustment of the camshafts, 
for other consumers so that their pumps may be dropped and, as a 
consequence, costs and space saved. 
In this conjunction, both hydraulic devices may serve for the adjustment of 
camshafts, one camshaft adjusting device driven by each of the devices. In 
this context, in the case of engines with cylinders not being arranged in 
series (for example, V-shaped arrangement), the two camshafts can each 
actuate a series of inlet valves. It is another possibility that one of 
the two camshafts actuates exclusively inlet valves, whereas the other one 
actuates outlet valves. 
According to another advantageous development, the second device serves a 
consumer which has to be supplied with hydraulic pressure fluid with 
priority, because it is of importance for safety reasons. This consumer 
may be the hydraulic operating cylinder of a hydraulic power steering 
system, a chassis control device, a booster of an automatic clutch or a 
brake system. 
In particular, when an application requires that devices be equally or 
equivalently supplied with hydraulic pressure fluid, then solenoid valves 
provide a priority switching means such that, in a certain contingency, at 
least one of the two devices is actuated even in the event of a reduced 
pump capacity. 
A very simple design connection giving precedence to a consumer of 
importance for safety reasons is an unlockable non-return valve, subject 
to pressure in the second device, interposed between the first device and 
the pump. 
A very simple design connection for operating two hydraulically equivalent 
devices is a flow divider valve. In this instance both devices are 
supplied with hydraulic pressure fluid by a single pump circuit 
equivalently, without influencing each other. The hydraulic pressure fluid 
is delivered according to the demand of the devices by the flow divider 
valve. In particular, this type of connection is well-suited when both 
devices serve separate camshafts, each cam shaft exclusively controlling 
their respective outlet valves, or inlet valves. Another simple design 
connection preferable in the case of identical devices, in particular in 
devices actuating two camshafts, utilizes a proportional valve connected 
to the first device and a two position valve connected to the second 
device. Such an arrangement of connections is expedient if and when one 
device inlet camshaft and a second device outlet camshaft is to be 
adjusted, since for the optimization of the combustion within the engine 
the inlet camshaft has to be adjusted at finer steps than the outlet 
camshaft. In order to make sure that the other device (outlet valves) 
which is connected through the two-position valve is not influenced by the 
momentary function of the driving device (inlet valves) connected through 
the proportional valve, the overall system is designed such that in the 
former device a lower pressure exists than in the latter system. This is 
achieved in a simple manner by selecting a correspondingly larger 
cross-section of the hydraulic operating piston in the low-pressure device 
that is to say, in the device which actuates the outlet valves. 
In accordance with the further developments it is recommended that the 
two-position valve is a three-way two-position valve and that the piston 
for the adjustment of the camshaft controlling the outlet valves is 
prestressed in the retracting direction of the piston by means of a 
spring. 
In the hydraulic system in which the second device is a consumer which is 
of importance for safety reasons, the combinations of features shown in 
FIGS. 7 and 8 are recommended, along the lines of a further development of 
the inventive thought. In this design the effect of a priority switching 
means is also imitated in a simple way. 
Another method to avoid a priority switching means is provided by the 
combination of features shown in FIGS. 1-10. Such pumps work largely 
without loss, above all when they are controlled on the suction side. The 
pump may be configured optionally as a multiple-piston pump with only one 
single piston star, which allows a plurality of pistons to be grouped and 
connected together to form one pump circuit or to be furnished with a 
plurality of piston stars which are driven by a common driving shaft. An 
advantage offered by such a design is that, at but slight extra cost, the 
individual devices can be supplied with hydraulic pressure fluid largely 
without reciprocal reactions. To this end, a plurality of, for example, 
identical or equivalent devices are associated with each pump circuit. A 
further improvement as to excluding reciprocal reactions results from the 
application of the features as per the disclosed device. It is true that 
in this embodiment, in which with each consumer is associated with a pump 
circuit of its own, the disadvantage of a slightly excessive delivery rate 
at certain times in certain circuits might creep up, but any safety risk 
whatsoever caused by a reciprocal reaction of the individual devices is 
avoided. As an alternative, it can be imagined that one pump circuit is 
comprised of a plurality of consumers which may also be preferably 
connected in parallel. The devices should preferably be equivalent to each 
other. In this configuration, the application of a priority switching 
means is envisaged for the consumer which is of importance for safety 
reasons. 
A particularly silent operation of the hydraulic unit results when the pump 
is integrated into the cylinder head since the large mass of the engine 
damps the vibrations of the pump. 
When the pump is driven indirectly--for example by gear wheels and/or by a 
chain and/or by a toothed belt--or directly by the camshaft or, else, by 
the crankshaft, the energy losses will be further reduced. 
The device of FIGS. 11 and 12 offers the advantage that the hydraulic 
system is supplied with freshly delivered and, thus, also filtered 
lubricating agent as operating fluid, without the functionally determined 
pressure fluctuations in the lubricating circuit of the 
internal-combustion engine being transmitted to the suction behavior of 
the pump of the hydraulic system. The intermediate reservoir can be 
disposed in a favorable location inside or outside the internal-combustion 
engine and, therefore, many possibilities are presented to the design 
engineer for the positioning and the drive of the hydraulic pump. The 
constructional requirements for the storage and for the return of a 
separate operating fluid are dropped. The inventive hydraulic unit will be 
particularly advantageous if and when it serves for the actuation of 
controlling members inside the internal-combustion engine, for example for 
the control of the engine, because in that case the operating fluid can be 
conveyed back to the lubricating agent sump through the reflux ducts of 
the internal-combustion engine which are provided for the lubricating 
agent. 
As shown in FIG. 11 a restrictor orifice may be envisaged in the connecting 
line going from the lubricating circuit to the intermediate reservoir in 
order to limit to the necessary volume the quantity of operating fluid 
which is fed to the intermediate reservoir. 
Since the intermediate reservoir remains pressureless, the inventive 
hydraulic system offers, furthermore, the opportunity to control the 
delivery rate of the hydraulic pump by throttling the suction rate. Such 
control is highly advantageous where the system is driven by an 
internal-combustion engine in order to limit virtually without losses the 
delivery rate of the hydraulic pump at more elevated rates of revolutions 
of the engine. 
The embodiment affords a simple-design set-up of the hydraulic system and a 
simple-design configuration of the hydraulic pump, as any leakages 
occurring at the latter will can be conveyed directly into the interior 
space of the internal-combustion engine, as a result whereof any 
particular sealing of the hydraulic pump can be foregone. 
The embodiment in accordance with FIG. 12 is distinguished above all by 
minimized constructional efforts, since a tight seal on one side of the 
pump housing is dropped. Thanks to the arrangement of the orifice disc, an 
aspiration of air through the piston slot is, moreover, avoided, so that 
an air-free delivery of the operating fluid and, consequently, a reduction 
of the noise of the pump are ensured. The adulteration of the operating 
fluid, too, will be reduced to a considerable extent by an air-free 
delivery.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
In FIG. 1, a star of a radial piston pump 1 with six pistons 2, 3 is shown 
in a diagrammatic representation. The four pistons 2 are grouped together 
to form one pump circuit 4 which supplies hydraulic pressure fluid to 
hydraulic power steering system 5 and, through a priority switching means 
60, to camshaft adjusting device 6 which is connected in parallel. The two 
pistons 3 are grouped together to form the pump circuit 7 which supplies 
hydraulic pressure fluid to hydraulic booster 8 of hydraulic brake unit 9. 
In each pump circuit 4, 7 a pressure-limiting valve 10, 11 is inserted 
which, initiated by a preset pressure, opens up in the direction of the 
pressure-less reservoir 12. Out of said reservoir 12 the pump 1 aspirates 
the hydraulic pressure fluid. In the suction line 13, a filter 14 and a 
restrictor 15 are positioned, the latter limiting the maximum suction 
rate. 
The hydraulic brake system 9, with its booster 8, is not explained in more 
detail in this instance since such systems, in particular also those 
provided with anti-locking device, are general state of the art and a 
detailed functional description in conjunction with the present invention 
can, thus, be foregone. 
From the pump circuit 4, a line 16 leads directly from the pump 1 to a 
4/3-way valve 17 of the hydraulic power steering system 5. The latter is, 
thus, the priority consumer of this pump circuit 4. In the illustrated 
position of the valve 17, an open connection exists between the line 16 
and the line 62 which leads into the reservoir 12. In this way, the 
operating cylinder 21 can be supplied by the pump 1 with hydraulic 
pressure fluid. 
Furthermore, a connection leads from the pump circuit 4 over a line 61 and 
a priority switching means 60 to the 4/3-way proportional valve 22 to the 
camshaft adjusting device 6. By switching-over the valve 17, the right or 
the left side of the operating cylinder, that is to say, the line 19, 
respectively 20 is optionally subjected to the pump pressure over the line 
16. The other side of the operating cylinder 21 will then be connected to 
the reservoir 12. 
The 4/3-way proportional valve 22 controls the hydraulic pressure within 
the operating cylinder 23 of the camshaft adjusting device 6. In the 
illustrated central position of the valve, no direct connection exists 
between the lines 61 and 62, so that the operating cylinder 23 is cut off 
from the pump pressure. In this position, the operating cylinder 23 is 
hydraulically locked. In each one of the other two valve positions of the 
valve 22, the piston 24 is unilaterally pressurized and will slide 
accordingly. Simultaneously, a camshaft is rotated by a determined angle 
through toothing elements which are not shown in the drawing. This 
rotation is outlined by the arrow 25. 
The priority switching means 60 is provided in order always to be able to 
supply the operating cylinder 21 of the power steering system with 
priority to sufficient pressure from the pump 1. The element 60, which is 
not explained in more detail, ensures that on the actuation of the power 
steering system 5, no pressurized fluid can flow to the camshaft adjusting 
device 6. 
In all figures, constructional units are outlined by dash-dotted lines. In 
FIG. 2, in addition to the components described above, a second pump 
piston star 31 with pistons 32, 33 is shown, both pumps 1, 31 being driven 
by the same shaft. 
As in the pump 1, also in the case of the pump 31, the pistons 32, 
respectively 33 are grouped together to form one pump circuit 34, 
respectively 37. In said circuits 34 and 37, pressure-limiting valves 40 
and 41 are provided which are capable of discharging hydraulic pressure 
fluid in the direction of the reservoir 12. A device for level control 35 
is supplied with hydraulic pressure fluid by the pump circuit 34. Pump 
circuit 34 is controlled by a 4/3-way valve 47. Furthermore, two shock 
absorbers 49, two accumulators 50 and one brake power controller 51 are 
outlined. The circuit 37 supplies a further device 39 with hydraulic 
pressure fluid. This could, for example, be a clutch booster. 
In FIG. 3, again a double pump with two piston stars 1, 31 is shown, one 
pump 31 supplying the hydraulic power steering system 5 with hydraulic 
pressure fluid. The pump 1 supplies primarily the camshaft adjusting 
device 6 and secondarily, through the 2/2-way valve 52, a differential 
pawl 53 which is equipped with a slip control. By a priority switching 
means, being outlined in the shape of a switch 54, it is safeguarded that 
in case of need, said differential pawl 53 will be pressurized. 
In each of the FIGS. 4 to 6, one device 101 for the adjustment of an inlet 
camshaft and one device 102 for the adjustment of an outlet camshaft are 
shown. Each device 101, 102 consists of a double-acting hydraulic cylinder 
103, 104 and of an electronically actuatable proportional solenoid valve 
105, 106 with three potential positions. Said solenoid valves 105, 106 are 
controlled by a common electronic control unit 107. The latter may be a 
component part of the extended electronic engine management. 
For the supply of hydraulic pressure fluid, a hydraulic pump 108 is 
envisaged in all embodiments which aspirates hydraulic pressure fluid out 
of a pressureless reservoir 109. Said reservoir 109 serves simultaneously 
for collecting the hydraulic pressure fluid flowing back from the various 
consumers (103, 104, 125, 128). Parallel to said pump 108, a 
pressure-limiting valve 110 in each instance opens up in the direction of 
the reservoir 109. 
In the embodiment shown in FIG. 4, hydraulic lines 111, 112 lead directly 
from the pump 108 into the lefthand power chamber 113, 114 of the 
cylinders 103, 104 as viewed in the drawing. In the de-energized positions 
of the solenoid valves 105, 106 as shown in the drawing, the righthand 
power chambers 115, 116 are connected through the hydraulic lines 117, 118 
to the reservoir 109. When the valves 105, 106 are actuated over the 
electric lines 119, 120, the righthand power chambers 115, 116 can be shut 
off, from or connected to the pump 108. 
By stipulating the priority of the two consumers in the electronic control 
unit 107, delivery of pressure fluid to the lower priority device can be 
interrupted ensuring that sufficient pressure fluid can be delivered to 
the priority device when the pump delivery rate corresponds to the maximum 
consumption of one device 101, 102 only. In order to simultaneously or 
optionally adjust a determined position of both pistons 121, 122 within 
the cylinder 103, 104, either a permanent signal or a pulse 
width-modulated, respectively a pulse pause-modulated signal, is given to 
the solenoid valve 105, 106. For a priority-determined switching-off of, 
for example, the device 101, the valve must then not be supplied with 
electric current at all or care will have to be taken by means of an 
existing control circuit to ensure that the middle position of the valve 
is maintained. In lieu of the device 101, another consumer having 
importance under safety aspects may, of course, have its pressurized 
hydraulic fluid requirements ensured by an electronic control. 
Most of the components in FIG. 5 do not differ from those in FIG. 4. Only 
the differences will, therefore, be discussed. In the embodiment of FIG. 
5, no electronic priority control is provided. Downstream of the pump 108, 
a flow divider valve 123 is envisaged whereby both devices 101, 102 are 
being supplied equally with hydraulic pressure fluid. This solution is 
expedient above all for identical, equally important consumers. It has to 
be taken into account that the delivery rate of the pump 108 should 
correspond to the maximum consumption of both devices 101, 102 together. 
Nevertheless, this embodiment allows two equally important consumers to be 
supplied with hydraulic pressure fluid at especially low cost and in a 
particularly simple way. 
In the embodiment shown in FIG. 6, the device 101 is being supplied with 
hydraulic pressure fluid priority, as it is directly connected to the pump 
108. The second device 102 is connected to the pump 108 through a 
non-return valve 124 which is unlockable by the pressure in the line 111. 
In this design, the device 101 is supplied with priority with respect to 
hydraulic pressure fluid without electronic priority control so that in 
place of device 101 a consumer having importance for safety reasons could 
safely alternatively be envisaged. 
In FIG. 7 beyond a device 101' for the adjustment of a camshaft as a 
consumer, a hydraulic clutch booster 125 is illustrated which will, 
however, not be dealt with in more detail. The latter constitutes a 
consumer being of importance for safety reasons. A pressure switch 127, 
actuated by the pressure available for hydraulic clutch booster 125 in 
line 126, signals to either solenoid valve 105', in the event of a 
sufficiently high pressure in the system, to allow fluid to camshaft 
adjusting device 101' or, in the event of too low a pressure to the clutch 
booster 125, a signal for the locking portion of solenoid valve 105'. A 
pressure switch 127 is actuated by the pressure available for hydraulic 
clutch signals to either the solenoid valve 105' booster 125 in line 126, 
in the event of a sufficiently high pressure in the system, to allow fluid 
to the camshaft adjusting device 101' or, in the event of too low a 
pressure to the clutch booster 125, a signal for the locking position of 
solenoid valve 105'. By this provision, a priority supply of hydraulic 
pressure fluid to the consumer having importance for safety reasons is 
ensured by electrohydraulic means dependent on the pressure. 
In FIG. 8, an automatic clutch 128 is shown as the consumer having 
importance for safety reasons. The automatic clutch 128 is connected 
directly to the pump 108. System pressure acts on a pressure switch 129 
which is capable of connecting to a voltage source 131 a 2/2-way valve 
130, closed when de-energized, in the line 111 going to the device 101'. 
Also in this instance, hydraulic pressure fluid priority to the consumer 
having importance for safety reasons is ensured by the actuation of the 
automatic clutch depending on the system pressure. 
In the embodiments according to FIG. 4 and according to FIGS. 6 to 8, 
hydraulic units are proposed by the invention which afford a multiple 
utilization of a hydraulic pump 108 if and when for safety reasons one 
consumer must be supplied with priority with respect to hydraulic pressure 
fluid. The variant as per FIG. 5 permits a simultaneous supply of two 
equivalent consumers. The advantages mentioned above which result from the 
utilization of the pump provided for the camshaft adjusting device apply 
in all cases. 
FIG. 9 shows a device 201 for the adjustment of the inlet camshaft and a 
device 202 for the adjustment of the outlet camshaft. Each device 201, 202 
is comprised of a double-acting hydraulic cylinder 203, 204 connected to 
an electrically actuatable solenoid valve 205, 206. The solenoid valves 
205, 206 are controlled by a common electronic control unit 207. The 
latter may, for instance, be part of the extended electronic engine 
management. 
The device 201 for the adjustment of the inlet camshaft is equipped with a 
proportional valve 205 and with a hydraulic cylinder 203 having a small 
cross-sectional area, and the device 202 for the adjustment of the outlet 
camshaft is furnished with a two-position solenoid valve 206 and with a 
hydraulic cylinder 204 having a large cross-sectional area which allows 
adjustment thereof at a lower pressure level than the device 201. 
Both devices 201, 202 are supplied with hydraulic pressure fluid by a 
common hydraulic pump 208. Said pump 208 aspirates hydraulic pressure 
fluid from a pressureless reservoir 209 and conveys it through hydraulic 
lines 210, 211 and 212 to the proportional valve 205, to the hydraulic 
cylinder 203 and to the two-position valve 206 and from there to the 
hydraulic cylinder 204. Pressure-limiting valve 213 is connected to the 
line 212 and opens in the direction of the reservoir 209. 
In the illustrated valve positions of the valves 205 and 206, the pistons 
215 and 216 of the cylinders 203 and 204 move to the right in the drawing 
since each of the lefthand power chambers 217 and 218 are connected to the 
pump 208 and are pressurized and the righthand power chambers 219 and 220 
are both connected to the reservoir 209 and are thus pressureless. When 
the two-position valve 206 is reversed, then the righthand power chamber 
220 is pressurized and the lefthand power chamber 218 is connected to the 
reservoir 209, so that the piston 216 will slide to the left. Depending on 
the position of the two-position valve 206, the piston 216 will remain in 
its left or in its right final position. Depending on the position of the 
proportional valve 205, the piston 215 can be moved to any optional 
position. In the middle position of the valve 205, the piston 215 will 
remain immobile, since the righthand power chamber 219 is hydraulically 
locked. In the position of the valve 205 in which both power chambers 217 
and 219 come to be connected to the pump 208, the piston 215 will move to 
the left, as the righthand piston surface is larger than the lefthand one. 
Whereas in FIG. 9 the piston rod 223 is capable of adjusting the outlet 
camshaft in both directions in accordance with the direction of motion of 
the piston 216, in FIG. 10 another possibility for the adjustment of the 
outlet camshaft by the piston 216 is illustrated 
FIG. 10 shows an extract of FIG. 9 which shows substantially the actuation 
of the outlet camshaft through the piston rod 223 by means of the piston 
216. The assemblies shown in FIG. 10 will be explained only inasmuch as 
they have a method of operation which is different with respect to FIG. 9. 
In FIG. 10, the second piston 216 has a preload directing it to the right 
side by means of a spring 224. The second piston 216 will, therefore, 
travel to the right as soon as the force exerted by said spring overcomes 
the force exerted by the pressure in the power chamber 220. 
A simple-effect mode of operation results from such a configuration of the 
operating cylinder. In this design, for the retracting direction of 
motion, the force being exerted by the camshaft through the piston rod 223 
is aided by spring 224. 
A simplified configuration of the valve 206 will result from this measure 
insofar as by comparison with FIG. 9 two through openings for the passage 
of the control fluid can be eliminated. Beyond this, the comparison shows 
that by the arrangement in accordance with FIG. 10, a second connecting 
line between the cylinder 204 and the valve 206 can be foregone. 
FIG. 11 shows a part of the lubricating circuit of an internal-combustion 
engine with a lubricant sump 301, a lubricating pressure pump 302, a 
filter 303, and a lubricating pressure line 304. From the lubricating 
pressure line 304, a delivery line 305 with a restrictor orifice 306 
branches off terminating in an intermediate reservoir 307 with an overflow 
308. Said intermediate reservoir 307 is part of a hydraulic unit which is 
comprised of a suction-controlled hydraulic pump 309, a pressure-limiting 
valve 310, an electromagnetically actuatable control valve 311, and an 
operating cylinder 312. The delivery line for the suction side of the 
hydraulic pump 309 is connected to the intermediate reservoir 307 through 
a restrictor orifice 313 for suction control. The delivery side of the 
hydraulic pump 309 is in direct connection with the piston rod side of the 
operating cylinder 312. For carrying out positioning movements, the piston 
rod-free side of the operating cylinder 312 is connected by the control 
valve 311 either to the delivery side of the hydraulic pump 309 or through 
a reflux line 314 to the lubricant sump 301. In the position of rest, the 
control valve 311 is locked and the piston of the operating cylinder 312 
is maintained in the position it has reached at the particular moment. A 
reflux line 315 also leads to the lubricant sump 301 from the 
pressure-limiting valve 310. 
The described hydraulic system can advantageously utilize the lubricating 
circuit of an internal-combustion engine to supply operating fluid to a 
hydraulic pump 309 driven by the internal-combustion engine, 
notwithstanding the considerable fluctuations of the operating pressure 
due to the rate of revolutions of the engine and the operating 
temperature. The pressureless intermediate reservoir 307 provides suction 
pressure control of the hydraulic pump 309, so that the delivery rate of 
the hydraulic pump 309 can be limited to an adequate maximum value in a 
simple way and with minimum loss, regardless of strong fluctuations in the 
rate of revolutions of the pump drive. 
In FIG. 12 an embodiment of a hydraulic pump 309 is illustrated which is 
suited for the described hydraulic system. Hydraulic pump 309 is 
configured in the shape of a radial piston pump 309 and furnished with a 
substantially disc-shaped pump housing 316 flanged to the engine casing 
317 of an internal-combustion engine and enclosing an opening 318 in the 
engine casing 317. Said pump housing 316 is formed with a longitudinal 
through bore 319 and a successive cylindrical recess 320. Within said 
longitudinal bore 319, a control pivot 321 is fixed, for example by 
pressing, and projects into said recess 320. A rotor 322 is pivoted on the 
control pivot 321 within said recess 320. In rotor 322, a plurality of 
radially-directed cylinder bores 323 are configurated within which pistons 
324 slide. Said pistons 324 are supported at their radially extended ends 
at the inner surface of a stroke ring 325 which is pivoted eccentrically 
with respect to the control pivot 321 within the recess 320 by means of a 
roller bearing. In the control pivot 321, control slots 326, 327 are 
configured in the plane of said cylinder bores 323 which in the event of a 
rotation of the rotor 322 come into connection one after the other with 
the individual cylinder bores 323 through radial connecting bores. The 
control slot 326 is located in the suction range of the pistons 324 and is 
connected to a suction duct 328 which runs in the longitudinal direction 
within the control pivot 321. Through an aspiration bore 329, said suction 
duct 328 is connected to an intermediate reservoir 330 which is formed as 
a chamber in the housing 316. The control slot 327 is located in the 
pressure range of the pistons 324 and is connected, through a pressure 
duct 331 in the control pivot 321 running parallel to the suction duct 
328, to an annular groove 332 from which, outside the drawing plane, a 
bore leads to a pressure connection of the hydraulic pump. 
The rotor 322 is driven, through a coupling 333, by a shaft 334, for 
example by the camshaft of the internal-combustion engine. The coupling 
333 consists of a ring with axial wobblers. Radially outside the coupling 
333, the recess 320 is enclosed by an orifice disc 335 being shaped of a 
thin metal sheet which is pressed into the recess 320 and is in abutment 
at a step surface of the recess 320. The orifice disc 335 encompasses the 
radially extended range of the rotor 322 and serves for the latter, as 
well as for the stroke ring 325, as a stop disc to limit motion in the 
axial direction. Leaking operating fluid which escapes at the pistons 324 
and at the control pivot 321 is contained by orifice disc 335. As a 
result, the radially extended ends of the cylinder bores 323 are covered 
by operating fluid and air is prevented from aspirating through the piston 
slot when the suction pressure rises at the start of the suction pressure 
control. Excess operating fluid can flow off through the central bore for 
the coupling 333 into the engine casing 317. 
The intermediate reservoir 330 is represented in a cross-section in the 
drawing and extends substantially vertically with respect to the drawing 
plane. The suction bore 329 terminates in the intermediate reservoir 330 
near the bottom. Above the suction bore 329, operating fluid is fed to the 
intermediate reservoir 330 through the delivery line 305 which is branched 
off from the lubricating pressure line 304. Said delivery line 305 is in 
connection with the intermediate reservoir 330 through a restrictor 
orifice 336 which is provided in a cover lid 337 of said intermediate 
reservoir 330. By a transverse bore 338 the stream of operating fluid 
leaving the restrictor orifice 336 is deviated at an angle of 90 degrees 
toward the bottom of the intermediate reservoir 330. The volume of 
operating fluid supplied is limited in the intermediate reservoir 330 by 
the restrictor orifice 336. Above the restrictor orifice 336 and set off 
laterally with respect to the latter, an overflow bore 339 is provided in 
the cover lid 337 through which excess operating fluid can flow out of the 
intermediate reservoir 330 toward the interior space of the engine casing 
317. The overflow bore 339 is disposed sufficiently high above the suction 
bore 329 that in any operating condition which may occur when the 
internal-combustion engine is mounted in a vehicle, such as braking, 
acceleration, driving through curves, shaking, inclined positions, the 
suction bore 329 will always remain covered with operating fluid. The 
restrictor orifice 336 is also positioned at a sufficient height so that 
the intermediate reservoir 330 will remain filled and cannot be drained 
over the delivery line 305 when the engine is switched off and the supply 
of lubricating pressure is interrupted. 
The described hydraulic system and the hydraulic pump are suited above all 
for application in passenger cars and lorries as well as in automotive and 
in stationary machines. A preferred application is hydraulic adjusting 
devices for the control of the internal-combustion engine, for example for 
the adjustment of the camshaft.