DE2162631A1 - ARRANGEMENT FOR STEERING POWER LIMITATION IN HYDRAULIC POWER STEERING DEVICES - Google Patents

Description

Patent a ri m el et- u η g

Subject: Arrangement for steering force limitation at hydraul! see power steering devices

Applicant: Company Langen & Co.

Ί Düsseldorf, Klosterstr. 4'J

The invention relates to an arrangement for limiting the steering force in hydraulic power steering devices with a steering valve for the so-called two-Kantön control of a pressure medium flow from a pressure source to a working space preferably larger effective area of a servo motor or from dera work space to a return, the work space preferably always having a smaller effective area is connected to the pressure source, and wherein reaction members with hydraulically acted upon reaction surfaces for feedback of a steering feeling to the handlebars are provided which reaction elements the different effective surfaces of the servo motor are assigned and in connection with corresponding lever arms or the like and / or corresponding reaction surfaces form a torque balance or the like.

It is known that the power steering systems commonly used hitherto have steering valves with four control edges possessed. These steering valves were used to supply the working spaces of a servo motor, which ini essentially had areas of the same size. FJin The work area was connected to the return flow, when the other was in communication with the pressure source. Reaction members mostly also possessed same areas and acted on the same lever arms,

as far as the ■ reaction curses are not anyway., r.iit the end faces of one or more control pistons were identical. With such an arrangement, the detuning of the rotary indicator or the like took place very easy due to the changing pressures in the reaction chambers. Correspondingly simple steering force limits could be implemented. It was enough to reduce the pressure in the reaction areas limit the desired amount. This limitation took place, for example, via pressure reducing valves (German patent Γ obo 672), which between ρ working space and reaction space were switched.

It has been shown that these arrangements are used for servicemen's institutions with two-edge control are not suitable. The reason is that that dem The work area with the smaller effective area, as well as the work area, assigned to the reaction congestion itself always from the essentially constant pressure of the Pressure source is applied. The detuning of the torque balance only takes place via the changing Pressure in the other reaction space.

It is therefore the object of the invention to find means "which the resentment in both the one limit in the other direction.

This object is achieved according to the invention through a combination of the following, individually partly known features:

a) That of the larger effective area of the servomotor The associated working space is connected to the associated reaction space via a throttle point tied together.

f- preferably ,, .-.

^309825/0187 BADORONAL

21S2631

b) That of the preferably smaller effective area of the servomotor assigned work space or the The pressure source is .with the reaction space assigned to the preferably larger effective area connected to a pressure reducing valve, which when falling below a certain lower pressure in the reaction chamber or when exceeding a certain pressure Pressure difference between working space

and reaction space opens. . .

c) The reaction space, which of the larger effective ones Area of the servomotor is assigned, is connected to the return via a pressure relief valve, which the exceeding of a certain the upper pressure in the reaction chamber

The pressure reducing valve is expediently on Pressure drop valve, which causes a constant pressure difference Ap. If the pressure relief valve is less pressurized Return provided the same pressure difference Zip is set and the ratio of the effective areas is 2: 1, can be used in both directions achieve the same maximum reaction forces. Of course you have to

2 · 4 P> P _n and on the other hand Δ P < P _n , where

Jp the pressure difference and ρ the pressure in that mean the working space assigned to the smaller area.

The invention is in its structure and mode of operation based on the exemplary embodiments shown in the figures explained in more detail.

preferably? _ _Ät _ _.

BATH ORIGINAL

309825/0187

FIG. 1 shows in a schematic representation, partly with symbols, an arrangement with one of the control pistons of the steering valve itself has reaction surfaces.

Figure λ shows a corresponding arrangement for a steering valve with a control piston provided with only one reaction surface and / or a separate, oppositely acting reaction piston. FIG. 3 shows in a diagram the relationship between the force on the servomotor and the reaction force. Figure 4 shows a very simple embodiment of a pressure drop valve.

A pump 1 conveys pressure medium into a pressure line 2, which leads to a connection P, a steering valve 3 so / ie to a connection P _{2 of} a servo motor 4. The steering valve has a housing 5, which has a bore 6 in its interior for driving a control piston 7. The control piston 7 has two shoulders 9 and Io separated by a waist £. 7m of the shoulder Io is an actuating rod 11, which leads tightly out of the steering valve 3 and which is connected to a part (not shown) of an at least two-part power transmission device between the steering wheel and the steered wheels. The housing 5 of the steering valve 3 is connected to the other part. The actuation takes place due to a slight relative movement between the two parts. The generation of this relationship has nothing to do with the invention and is therefore not shown in more detail. The connection P opens into an annular space 13 which surrounds the actuating rod 11 and which acts as a reaction surface F on one side

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309825/0187 ORIGINAL BATHROOM

216263Τ

. Ring surface of the shoulder Io is limited. In a central position of the control piston 7, the shoulder Io separates an annular groove 14 surrounding it from the annular space 13 and from an annular space 15 surrounding the waist 8. A connection T, _f which is connected to an outlet 16 ', opens into the annular space 15 . The free end face of the shoulder 9 acts as a reaction surface F and delimits a reaction space 17, the

2
is provided with a connection Λ. From the connection A ₀ , a line 18, in which a throttle point 19 is installed, leads to a connection A, which opens into the annular groove 14. A further line 20, which leads to the storage container and in which a pressure-limiting valve 21 is installed, goes out from connection A or line 18. Another line 22 emanates from the pressure line 2 and also runs via a pressure gradient valve 23 to connection A ₂ . The servomotor 4 consists of a cylinder 24 in which a piston 26 connected to a piston rod 25 slides. The servomotor acts as a support for the manual steering force on part of the power transmission device (not shown) or is connected in parallel with it. The connection P ^ opens into a working space 27 which surrounds the piston rod 25 and is delimited by the smaller effective area f .. of the piston 2ü. The larger effective area f ^ of the piston 26 delimits a working space 28 into which a connection A ^ opens, which is in communication with the line 18. A pressure-limiting valve 29 connected to the pressure line 2 serves to limit the pressure of the entire system. The ratio of the reaction areas and the ratio of the effective areas is F ^: F = f: f = 2: 1.

216263

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To explain the function, it is assumed that the pressure relief valve 29 is set to loo bar. The pressure difference i \ p _ia at the pressure drop valve 23 is just like the pressure difference / dP _a K ⁰ ^ ¹ pressure relief valve 21 70 bar. The respective pressure in the reaction chamber 17 and the system communicating with it _{is denoted by P / k} , while the pressure in the king chamber 13 and the system communicating with it is denoted by P. In the position shown, which corresponds to driving straight ahead, a pressure of 50 bar is established both in the working chamber 28 and in the reaction chamber 17. There applies

5 ©. f2 = loo. f. as well as

5 °. F _n = loo .F

* ■ 1

if the servomotor 4 is in equilibrium and there are no resulting forces acting on the control piston 7 either. If now the control piston 7 is operated during a steering operation to the left, pressurized fluid flows from terminal P to terminal A. and from there first through the terminal A ₃ in the working chamber 28, thereby there is a to be about v / i ndenden forces corresponding Pressure build-up takes place. This pressure build-up reaches connection A ₂ and the reaction chamber 17 via the line 18 and the throttle point R, the following equation results

- 60 • ^F 2 - 100 .. = 1 2o a ^P l - loo F ₌ 2o F,

3 0 9 8 2 5/0187 BAD ORIGINAL

iv.äiin ■ iiiit Γ, denotes a unit of area, the handicraft is now 2o holding power. If the Pressure iiii reaction space 17 has increased to 7o bar, you get

K ₁ . = 7o F, - loo F _n H max 2 1

= ίο F ₁

If the pressure tries to rise further, the pressure relief valve 21 opens and keeps the pressure constant at 70 bar. The pressure in the working space 28 can of course continue to rise and in an extreme case can reach 100 bar. Diesel "context exsichtlich of Figure 3. It is seen that the manual force first increases in proportion to the force K _fT aiii servo motor 4, and then horizontally further Vn runs. To prevent excessive outflow of pressure medium from the working chamber 2Ό via the pressure limiting valve 21 is The throttle point ID is built into the line 18. This throttle point 1-J allows a very rapid pressure equalization below the limit pressure of 70 bar, since only extremely small quantities resulting from expensive movements of the control piston 7 then flow through If the control piston 7 is moved to the right in the opposite way /, it establishes the connection A, - T, so that both in the working space 28 as aucii a pressure drop occurs in the reaction space 17. At a pressure drop of Io bar

3098 26/0187

BADORIGtNAL

So at P _A ~ 40 bar, results in hand force

Kj ₁ = loo. P - 4o. F "

= 2o F ₁ .

If the pressure drops further down to 30 bar, receives man

^K Hmax ^{= 1OoF} r ^3O * ^F 2 = 4o F ₁ -

Every further pressure drop results in the pressure drop valve opening, which is set to a pressure difference P _D - P, = loo - 3o = Z \ P "" = 7o bar.

The opening causes a current from the line 22 into the line 18 in such a way that at the throttle point 19 a dynamic pressure arises which does not fall below the value of 30 bar. This fact is of course true only as long as pump 1 or the pressure accumulator is delivering Has stored pressure medium.

It can be seen that the ' Steering force is limited to the same value. In general, this results in

^K H max

^K Hmax

Under the above mentioned condition

^ Pzu ⁼ 4 ^p from
the result is actually the same value in both directions.

309825/0187

In contrast to Figure 1, the steering valve 3ό in Figure 2 has a control piston 31 with only one reaction surface F 1. The advertising area. F ₂ is arranged on a separately arranged reaction piston 32 which, like the control piston 31, is actuated by a rotatable lever 34 via tappets 33 and 33 ', in such a way that the reaction piston 32 counteracts the control piston 31. The control piston 31 has three shoulders 35, 36, 37 which are separated by waists 38 and 39. _{The connection T 1} opens into the annular space 4o around the waist 38, while the connection P ₁ opens into an annular space 41 surrounding the waist 39. The middle shoulder 36 closes the connection A 1 in a central position of the control piston 31. The plunger 33 'acting on the shoulder 35, while the free end face of the shoulder 37 as a reaction surface F, acts and a reaction space 42'. Limits ,. In the Reaktionsrauiu 42, a terminal Γ opens' ^1, which is connected to the pressure conduit 2. The other parts of the arrangement are given the same reference symbols as in Figure 1, insofar as they fulfill the same function. Since the mode of operation is practically the same, reference can be made to the description of Figure 1.

In Figure 4, what is probably the simplest form is one Pressure drop valve (23) shown. Ls sicji UIu is a ball 44 loaded by a spring 43, which is seated on a valve seat 45. The ball 44 is in the opening direction from the pressure of the inflowing DruckmitteIs ^ supports the force of the spring 4 3. The pressure difference depends on the preload of the spring 43. If there is no If there is pressure, such a valve can also be used

- Io -

- ^ acted upon, while in Sc liließrdichtung the pressure of the outflowing pressure medium

3 0 9 8 2 5/0 1 8 1

BAD ORfGINAL

- Io -

Use as pressure relief valve 21. It is clear that valves of the same function can of course also be used can be used with control piston. The valves can of course be changed by changing them the spring preload be adjustable. Instead of a pressure drop valve, a pressure reducing valve can also be used or a pressure ratio valve can be used. The use of such valves is recommended but only if the pressure P can be regarded as constant. Compared to the exemplary embodiments, the invention can also be applied to power steering systems use whose steering valves have no reaction surfaces, but with an or two special reaction links are provided. Furthermore, the spatial arrangement of Steering valve and servo motor are irrelevant, provided the necessary line connections for installation of the valves are present. With this prerequisite, even integrated construction methods can be implemented realize. The actuation of the steering valve due to a relative movement of two to each other moving parts can be brought about in the most varied of ways. But it is in the frame of minor importance to the invention.

Finally, it should be clear that the line connections shown and, in part, also the Connections can be routed or connected differently, as long as the individual systems are in themselves stay communicative.

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BATH ORIGINAL 309825/0187

In contrast to the embodiment shown, it is also possible to use the same servo motors effective areas to be used. It is then necessary, however, between the pressure source and not from the To install a pressure transducer in the working chamber controlled by the steering valve, which reduces the pressure.

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309825/0187

Claims (5)

Claims; l.j Arrangement for steering force limitation with hydrauy Lischen power steering devices with a steering valve for the so-called two-edge control of a Pressure medium flow from a pressure source to a work space preferably larger effective area of a servomotor or from the working space to a return, the working space preferably being smaller effective area is always connected to the pressure source, and reaction elements with hydraulically acted upon reaction surfaces for the feedback of a Steering feel to the handlebars are provided, which reaction members the different effective surfaces of the servo motor are assigned and in connection with corresponding lever arms or the like and / or corresponding reaction surfaces form a torque balance or the like, marked through the combination of the following individually partly known features: a) The working chamber (28) assigned to the preferably larger effective area (f ₂ ) of the servomotor (4) is connected to the associated reaction chamber (17) via a throttle point (19). b) That of the preferably smaller effective area (f ^) of the servomotor (4) associated working space (27) or the pressure source (1) is associated with that of the preferably larger effective area (f ^) Reaction chamber (17) connected via a pressure-reducing valve (23), which at Falling below a certain lower pressure in the reaction chamber (17) or when it is exceeded a certain pressure difference between the working space (28) and reaction space (17) opens. - 13 - 309325/0187 ^s - 13 - ·. - '■ "■ ■ ■■ ■ ■ c) The reaction space, which of the 'larger effective Area of the servo motor is assigned to the return via a pressure relief valve (21) connected, which is the crossing of a certain upper pressure in the reaction space (17) prevented. 2. Arrangement according to claim 1 / characterized in that the pressure reducing valve is a pressure drop valve (23). ^; - 3. Arrangement according to claim 1, for "·" an inv essential constant pump pressure ρ ^ characterized by that the pressure reducing valve is a pressure reducing valve or is a pressure ratio valve. 4. Arrangement according to claim 2 and 3, characterized in that that the on the pressure reducing valve set pressure difference is just as great like the opening pressure of the pressure relief valve (21). 5. Arrangement according to one or more of the preceding claims, characterized in that the pressure reducing valve (23) and the pressure limiting valve (21) are adjustable together. G. arrangement also claim 5, characterized in that that the adjustment takes place via a rocker, the lever arms being inversely proportional to the C-V / ert the springs cautiously. preferably 309825/0187 BATH