DE3230221A1 - HYDRAULIC PRESSURE CONVERTER - Google Patents

Description

PATENT LAWYERS

IiUROPEAN PATENT ATTORNEYS

. franz uesthoff

DIPL.-ING. GERHARD PULS (1952-I971)

151 PL.-CH EM. DR. F. FRFlHERR VON PECHMAh

UK.-ING. bll'.TER BEHRENS U1P1 ..- ING .; DIPL.-WIRTSCH.-ING. RUPERT GO

1A-56 334

D-8000 MUNICH 90 SCHWEIGERSTRASSE 2

phone: (089) 6620 ji
telegram: protectpatent telex: 524070

August 13, 1982

Patent application

Applicant

LUCAS INDUSTRIES public limited company Great King Street

Birmingham 19, West Midlands
- England -

Title:

Hydraulic pressure transducer

". .I) R ~ -1nC:.!» AN?

WUESTHOFF-v. PECHMANN -BEHRENS-GÖET /:

PATENTANWÄLTE '.. "...;; .--.. - -dr.-inC ;. ι came / win shh.pp

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EUROPEAN PATENT TORNEYS

IIIl'L.-CHIM I) R. I '. IKFIlI! KR VON I ¹ I-CIIMANN DR.-ING. UIUTER HEIIRiNS DlfL-lNG.j DIPL.-WIRTSCH.-INC. RUI'tHT CiOETZ

D-8000 MÜNCHEN 90 SCHWEICERSTKASSEZ

IA-56 33 ^ ·

phone: (0R9) 66 20 ji TELEGRAM! I'ROTEOTI'ATENT TELEX: J 24 070

Description hydraulic pressure converter

The invention relates to hydraulic pressure transducers for generating a boosted or increased hydraulic pressure in one Pressure chamber depending on a lower hydraulic pressure supply.

In vehicles, it is usually considered too expensive to have a high-pressure pump only for use in the braking system to be provided. Consequently, it is desirable to be able to use a pump already present in the vehicle, e.g. a pump that for the power steering is available, or a lubrication pump or one for other additional equipment, e.g. a suspension Pump provided with automatic level compensation. That in itself already causes difficulties, since one already in one The vehicle's existing pump may not be entirely suitable to provide servo power for a braking system.

It is known to provide hydraulic pressure transducers in such arrangements which include a piston which is suitable in Depending on the lower pressure supply of the already existing steering pump or the like. a reinforced or elevated generate hydraulic pressure for use in the braking system.

The hydraulic pressure converter according to GB-PS 2 OI6 587 has the piston has a differential piston, which is in a

tion works, the outline of which is stepped accordingly, to a pressure generating chamber at the end of the piston with the smaller area and two actuation chambers on opposite sides of the part of the piston with the larger area to limit, the actuation chambers with a pump or a steering control valve and are connected to each other through a bypass passage. The back and forth movement of the Piston in the bore is caused by the action of a control valve, which at the opposite extreme Points of the piston movement is operated so that it alternately opens and closes the secondary passage, so that at closed valve the piston by the pressure of the fluid from the pump, which acts in one of the actuation chambers, against the action of the biasing force is driven in one direction, thereby fluid simultaneously from the other To drive out the actuating chamber to the steering control valve, while with the control valve open it causes the pre-tensioning force, that the piston is driven in the other direction, while fluid from the pump through the bypass passage directly to the Steering control valve flows.

In the hydraulic pressure converter according to GB-PS 2 016 587 the Biasing force is supplied by a return spring and the piston withdraws fluid from a container while a separate one Container is provided as a supply of fluid for the pump. . '·

According to the invention is in a hydraulic pressure transducer of the type mentioned with a differential booster piston, the works in a stepped bore in a housing, and a pressure chamber that is in the end of the housing with a smaller area is limited, the piston is adapted to be reciprocated in the bore 'to deliver hydraulic fluid from a Suction inlet through a first one-way valve into the pressure. space to draw and hydraulic fluid from the pressure chamber

-ν

to pump through a second outlet valve to an outlet and means for reciprocating the piston in the bore, to which a supply of hydraulic actuating fluid under pressure belongs to generate a force, which urges the piston in a first direction away from a given position, valve means acting on the Displacement of the piston in the first direction responds and the magnitude of the force decreases when the displacement reaches a predetermined value, and a facility. which the piston in a second direction opposite to first urges when the force from the valve device is reduced to the smaller value, suitable for the suction inlet, To draw fluid from a location upstream of a flow control for a steering pump.

This eliminates the need to provide a separate reservoir for the pump, while at the same time reducing flow fluctuations which may affect the features of the power steering control valve.

The withdrawal of fluid from the steering circuit represents make sure there is enough pressure to reset the intensifier piston so that it is no longer necessary is to provide a return spring.

- ir -

An embodiment of the invention is described below explained in more detail using schematic drawings. It shows*

1 shows a section through a hydraulic pressure converter; Fig. 2 is a graph of the valve loading;

which is plotted against the Yentilopening movement; 3 shows the curve according to FIG. 2 in an enlarged Jöassstab and

exaggerated for the sake of clarity; Fig ·> an arrangement scheme of a modified arrangement;

The pressure transducer shown in FIG. 1 knows a housing 1 old a hole 2 on "in which" works in booster piston 3 " the old of a pump rod 4 and a counter bxw. Follower rod 5 is provided * which each have the same surface area »but are axially in the opposite direction extend.

The pump rod k works in a bore part 6 and sees fluid from a container 7 through a first one-way valve 8 into a pump chamber 9 during the inward movement of the pump rod k and releases the fluid from the pump chamber 9 through a second when the pump rod 4 moves in the opposite direction One-way valve 10 on a brake circuit.

The counter rod 5 works in a similar Bohrstell 12 at the opposite end of the housing 1, the outer End via a normally closed, eolenoid operated Valve 13 connected to a container 1st

1st on the side of the piston adjacent to the counter rod 5 an inlet opening is provided, which is connected to a steering » pump of a vehicle is connected, and provided on the opposite side of the booster piston 3 Aus * Orifice 15 is connected to the steering valve.

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The connection between the chambers 36, 37 formed at the opposite ends of the booster piston 3 is controlled by a control valve X6 which has a valve closing body 17 which works in an inclined bore 18 extending through the booster piston 3 and at its inner end a seat 19 can be brought into engagement so that it controls the connection between complementary passages 20 and 21. The valve closing body 17 is normally urged away from the seat 19 by a spring 23 in the form of a return pressure spring.

A shaft 2k extends from the valve closing body 17 in the direction of a cam surface 25 surrounding the inner end of the bore part 6 and carries a head 26 which works in a bore 27 of the valve closing body 17. A spring 28, namely a compression spring, normally pushes the head against a stop 29 in the adjacent end of the bore 27, which also forms a stop for the spring 23 *

In the bore of the valve closing body 17 also slides a floating piston 30, which is connected between the spring 28 and a plate spring or washer-like spring 31 is.

From the end of the valve closing body 17 remote from the shaft 24, a second shaft 32 extends in the direction of a second cam surface 33 »which surrounds the inner end of the bore part 12.

In the rest position, the booster piston 3 has a strong Spring 35 in the form of a return pressure spring in a retracted position Position held, and in this position, the control valve 16 by the engagement between the shaft 32 and the Cam surface 33 held in the closed position.

In operation, fluid from the power steering pump to the inlet

The opening Ik leads and causes the booster piston 3 to be moved away from the cam surface 33 in the chamber 36. The movement of the booster piston 3 is counteracted by the spring 35, the friction of piston seals, the pressure drop at the one-way valve 10 for the supply and possible pumping forces in the chamber 9 ₍ and these counteracting forces generate a pressure in the chamber 36, which causes the booster piston 3 to move and also on the end of the central closing body 17 remote from the shaft Zk acts to keep the control valve 16 closed against the force of the spring 23.

When the booster piston 3 moves to the left, the shaft Zk bit of the cam surface 25 engages and the pressure in the chamber 36 acting on the cylinder body 17 generates a compressive force by which the springs 28 and 31 are pressed together. First, the spring 28 is compressed until the head 26 engages the piston 30, and then the spring 31 is compressed. The force in springs 28 and 31 is also an opposing force by which the pressure in chamber 36 is increased. The increased pressure in the chamber 36 in turn increases the compressive force which acts on the valve closing body 17 in order to press the springs 28 and 31 even further. Because of the relative areas of the valve closing body and the booster piston 3, however, the increase in the pressure force acting from the chamber 36 on the valve closing body 17 is less than the increase in the spring force "which acts on the valve closing body 17". At a certain point the force is in the springs 28 and 31 greater than the pressure force "which acts on the valve closing body 17 from the chamber 36" and the control valve 16 opens and allows fluid to flow from the chamber 36 into the chamber 37Details about opening the valve can be found in the curve according to FIG 3 outstanding

Fig * 2 shows «in curve A of the" Ventlistelf ", namely the Valve loading, i.e. the hydraulic force that strives is »the valve 16 under the force directed to the left · close fluid flow below - and this is entered via the movement of the Yentil clasp body 1? when opening the Control valve 16. For the sake of clarity, the curve of FIG. 2 is exaggerated in FIG. As can be seen from Fig. 3, represents the inclination of a tangent * which is placed on this curve at any point, the "valve stiffness" on the 8em Point. Inclined lines on the curve can also represent spring stiffness "and" if the spring stiffness was higher, the steeper the slope. The lower dashed horizontal line between the W and the horizontal axis gives the Load on the spring 23 again

If there is no external resistance for the pump rod 4, the pressure acting in the chamber 36 during a power stroke is low. When the control valve 16 begins to open, the pressure in the chamber 36 corresponds to a valve load W ^ in the curve. The horizontal line W ₁ B shows the opening of the valve under constant load, so that the spring 28 is not released when the control valve 16 is opened, but the booster piston 3 slows down to the extent that the valve takes in more inlet flow B (on the curve of the stiffness) the control valve 16 absorbs the entire input flow, and the booster piston stops when the control valve 16 comes to a standstill. When the booster piston 3 is stationary, the pressure in the chamber 36 depends only on the opening of the valve, so that further actuation is determined by the valve stiffness according to curve A. Line BC in the curve represents the stiffness or constant of spring 28, which is less than the valve position at B. Any slight change in flow or load from the pump chamber makes control valve 16 unstable and opens to C, where energy from the spring 28

sees "there at any point" wipe B and C die Spring load is greater than the valve load.

A similar consequence shall now be considered at high pressure "if there is an initial resistance for the Punch rod 4. When the control valve begins to open 16, the valve loading now begins at Wj ₁ , and point B 'corresponding to B is higher. The line B * Ö * indicates "that a very strong stroke (greater than the only available joint) would be necessary" to compress the spring 28 to a load corresponding to W "* This cannot be circumvented by preloading the spring" Such a preload a spring characteristic would arise "which would follow the line B'C down to the preload and then drop vertically * ura to provide an infinite spring stiffness below this load, since the spring constant must be less than the Yentll stiffness" to open the valve, see below can »the valve would not open at loads below the preload · The additional disc springs 31 of high stiffness can offer a solution. Its stiffness is shown by the line B * D in the curve, and it causes the valve to open successfully under all loads bie down to W _x , where the valve position is just slightly higher than the stiffness of the spring 31t. The spring begins at lower loads 28 to expand with the lower stiffness and causes "that the geearate spring constant follows the curve B ¹ DE" so that the valve salt is successfully opened with a stroke that is short compared to that "which resulted from the use of a single spring with relatively low spring stiffness were.

When the booster operates at very low pressures, the spring 35 provided as a return pressure spring delivers the Main resistance to leftward movement of the piston. The pressure difference generated by the movement against this resistance at the intensifier piston 3 must be large enough to

334

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keep the control valve 16 closed against the force of the spring 23 · Movement of the booster piston 3 to the right during the return stroke also tends to generate a pressure difference in the same direction as that obtained during the left stroke · Since the control valve 16 while the return stroke is open »it would be expected» that this pressure difference is very small. As a result, there is a risk that the piston total will reach the point at which the resulting pressure drop across the open control valve 16 exceeds the load on the spring 23, with the result that the control valve 16 snaps shut and shortens the return stroke. Measures must be taken to dampen this return movement · Damping means can be provided in any suitable form, ζ · Ε · in the form of increased sealing friction. However, it is preferred to provide a one-way valve 40 and a throttle kl connected in parallel, which is switched into the line between the counter rod 5 and the Y-valve 13, as FIG. 1 shows.

With the construction described above, the energy stored in springs 28 and 31 acts during each temporary reduction of the fluid flow rate or any other counteracting load that supports the fluid, since the control valve 16 is above its fixed point is opened out

When the solenoid operated valve 13 is de-energized, it acts as a one-way valve and traps fluid in the outer end of the Bore parts 12 a. This creates a hydraulic lock that keeps the booster in the off position holds.

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. Is shown k Bti a modified embodiment shown in Anordnungsscheoa of FIG, the Punpeneaugelnlaß a Ströeungssteuerung kO at the steering pump VKI looks from a location upstream from · This has "that except-calibrating pressure * eteht advantage for disposal to the Veretärkerkolben 3 in its to bring back the withdrawn position. The spring 35 can consequently be absent

The advantage of creating an increased restoring force is only achieved "because steering control valves la in general and even in the" straight ahead "position create an intended amount of throttling» around responsiveness Improve the valve KU If this were not the case, there would normally be negligible pressure in the Circuit and the modification geiaäa Flg. 4 wouldn't bring any Advantage.

According to an alternative, the counter rod 5 can this pressure be exposed. The steering pump needed less power «To drive and the flow in the counter rod was the Do not skim the steering valve flow as the counter rod 5 between the steering pump P4l and the strand control 40 switched 1st «

Claims (1)

Claim A hydraulic pressure transducer for generating an increased or increased fluid pressure depending on a lower one hydraulic pressure supply with a differential booster, which is in a stepped bore in a housing works, and a pressure space which is limited in the end of the housing that has the smaller area, the piston is adapted to be reciprocated in the bore to carry hydraulic fluid from a suction inlet through a first One-way valve to pull into the pressure chamber and hydraulic fluid from the pressure chamber via a second one-way valve to one To pump outlet, and with means for reciprocating the piston in the bore to which a supply of hydraulic actuating fluid under pressure that generates a force that moves the piston in a first direction away from a given position, valve means responsive to displacement of the piston in the first direction and reduces the magnitude of the force when the displacement reaches a predetermined value, as well as a Device that opposes the piston in a second direction pushes towards the first direction when the force is reduced to the lower value by means of the valve device, characterized in that the suction inlet (9) is adapted to receive fluid from a location upstream of a flow control (Jj-O) for a steering pump (41) to be deducted.