DE2335702A1 - HYDRAULIC SYSTEM - Google Patents

Description

Dr. I ■

Dipl Ing. H. Κ.ι-. id. .. -. . C-hmitz Dipl. Tnä. E. Gfa & i .; - Dipl. Ing. W. Wehnert

8 Munich 2, MoierJstraOe 23

Telephone 5380586

-ILR CORPORATI 'X.
200 Soutii Michigan Avenue

^ o, 111. 60604, U3A Manchjn, July 13, 197

Attorney File M-2744

Hydraulic system e

The invention relates to a hydraulic system and is based on a hydraulic system in which a pressure medium source, a fluid sump, a control valve with an between Pressure medium source and sump running neutral flow channel to produce a variable throttling effect and a pressure gradient between the pressure medium source and the sump, as well as a fluid-operated one Consumers are connected to one another by a common circuit.

Conventionally, one is open in the middle position Provide the control valve with a neutral flow channel, which connects the inlet opening of the control valve with the vent opening, so that the entire delivery rate of the pump is fed to the fluid sump via the valve. With multiple control valves, i.e. valves that have multiple control sections,

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Each control section is provided with a neutral flow channel, and all the neutral flow channels are in series with each other tied together. The neutral flow channel of a valve is always throttled or blocked when this neutral flow channel associated valve body is adjusted in such a way that the fluid supplied by the pump is a working opening is fed. In the case of valves with reversible pressure medium actuation of fluid motors, the valve body and the neutral flow channel is designed such that the neutral flow channel is throttled or blocked when the Valve body out of neutral in any direction is moved.

According to the invention, the operation of a hydraulic system with a control valve that is open in the middle position is carried out Improved use of a Kengenstrom-control device, which is connected in series with the neutral flow channel of the control valve and controls the mass flow through the neutral flow channel. The mass flow control device is actuated with With the help of a parallel connection to a neutral flow channel of the control valve.

The mass flow control device is connected in series with one or more neutral flow channels, these in turn are connected in series with the pump and the sump, so that the entire amount of fluid delivered by the pump contains all

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borrowed neutral flow channels and the mass flow control device flows through. Thus, both the mass flow control device and any of the neutral flow channels can To regulate the flow from the pump to the sump.

is
The mass flow control device / connected not only with the neutral flow channels to control the mass flow through the neutral flow channels in series, but also connected in parallel to one or more neutral flow channels connected in series, so that the setting of the mass flow control device depending on the pressure in one single neutral current channel or in any of the series-connected neutral current channels.

During operation, the narrowing of a neutral flow channel when a valve body is displaced a relatively small pressure gradient in this neutral flow channel generated, and this small pressure difference is used to adjust the flow control device, the in turn sets the pressure gradient that is required in each case, that flow from the pump to the sump to maintain, at which this low pressure gradient is kept constant at the neutral flow channel.

The use of such a mass flow control device results in three main advantages: on the one hand, the

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provide the valve body with the required actuation forces considerably reduced. This is due to the fact that the equilibrium forces acting on the valve body, a Are a function of QYAP, where Q is the flow rate and Δ. Ρ the Pressure difference is. These equilibrium forces are lower because only the control pressure difference through the neutral flow channel is set and the total pressure gradient between the pump and the sump primarily through the mass flow control device is caused.

A second advantage is that the flow of fluid to a fluid motor is proportional to the displacement of the valve body and is independent of the load, as long as there is only one valve body at a given point in time is operated. This is due to the fact that the mass flow control device in the bypass flow a part of the amount of fluid discharges to the sump, which is proportional to the flow capacity of the neutral flow channel. So that is the remaining part of the mass flow that reaches the fluid motor via a working opening is proportional to the displacement of the valve body.

A third advantage is that, as long as only one valve body is actuated at any point in time, the pump pressure is only as high as it is to adjust the pressure applied to the actuated fluid motor

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Load is required and the excess fluid to the sump at a pressure approximately equal to the load is returned.

Further details and features of the invention emerge from the claims and the following description in conjunction with the drawings. It shows;

1 shows a section of a control valve with three valve bodies and the mass flow control device in a single housing; further components of the system are shown schematically;

Pig. 2 a further embodiment in which the volume flow control device between the pump and the neutral flow channel is arranged; further components of the system are schematic shown.

According to Fig. 1, the hydraulic system contains a control valve 10, which is connected directly or in one piece to the mass flow control device 11, a pump 12, a pressure relief valve and a swamp Ha and 14b.

The control valve 10 includes a valve housing 15 and valve body 18a, 18b, 18c, which are in valve bores 19a, 19b and 19c

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of the valve housing 15 sit. The closure cap 20 contains conventional centering springs for the valve bodies 18a, 18b and 18c, by means of which the valve bodies are held in their neutral positions shown.

The mass flow control device 11 contains a control piston 22, a spring 2, 3 and a plug 24, all of which are arranged in the part of the valve housing 15 designated by 25.

When all the valve bodies are in their neutral position shown, the system operates as follows: that supplied by the pressure medium source in the form of the pump 12

the
Fluid passes via / line 28 and 29 to the inlet opening 30 of the valve 10, whereby the pressure inlet channels 31a, b, c, d, e and f, which end at the points 32a and 32b, are pressurized. The fluid supplied to the opening 30 also reaches the first opening 33a of a neutral flow channel 34a, which consists of the first opening 33a, the second opening 35a, the annular space surrounding the reduced section 36a of the valve body 18a and the adjoining sections of the valve bore 19a. The second opening 35a of the first neutral flow channel 34a is connected via a line 37a to the first opening 33b of the second neutral flow channel 34b, and in a corresponding manner all neutral flow channels 34a, 34t> and 34c are connected in series; Finally, the second opening 35c of the neutral flow channel 34c is the inlet opening

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40 of the mass flow control device 11 is connected.

That to the inlet opening 40 of the mass flow control device 11 Arriving .Strömmittel can via the throttle channel 47, which from the Ilaum between the reduced portion 42 of the piston 22 and an adjacent section of the cylinder bore 43, flow freely to the outlet opening 41. The exit opening 41 stands with the ventilation channels 44a, 44b, 44c, 44d, 44e, 44f and 44g in connection, which are connected to the outlet opening 45, which via a line 46 to the sump 14b connected is. The fluid conveyed by the pump 12 therefore passes through the neutral flow channels 34a, 34b and 34c of the Control valve 10, the throttle channel 47 and the outlet opening

41 of the mass flow control device 11 to the outlet opening 45 and to the sump 14b, which in practice with the pump 12 Sump 14a supplying fluid via a line 50 forms a structural unit; the entire volume flow delivered by the pump 12 is therefore returned at a low pressure.

The control valve 10 includes working ports 51a, 51b, 51c and 51d, to which one of the valve bodies 18a, 18b or 18c fluid connections can be established. The control valve 10 also includes inoperative work ports 52a and 52b, which are formed in the valve housing 15 according to the drawing, but due to the formation of the corresponding valve bodies

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are effective; next to each of the working openings 51a, 51b, 51c, 51d, 52a and 52b is a venting channel 44 and a pressure supply channel 31.

The working medium can be supplied from a pressure supply channel 31a, b, c, d, or e to a working opening 51a, b, c or d and from one of the working openings to one of the ventilation channels 44a, b, c, d, e or f move by moving the valve body 18a, b or c assigned to this working opening out of the valve body neutral position shown is shifted either to the right or to the left in an operating position.

The valve body 18a directs the pressure medium from the channel 31a to the working opening 51a when the valve body 18a to the left into a first operating position is moved. When the valve body moves to the right, because of the axial length of the web 53 of the valve body 18a no connection established between the working opening 51a and the venting channel 44a. Consequently the valve body 18a together with the bore 19a forms a two-way valve.

The valve body 18b connects the working opening 51b with the channel 31d when the valve body 18b to the left in a first Operating position is moved, and brings the working opening 51b with the vent channel 44a, b in connection when the valve

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body 18b is adjusted to the right in a second operating position, so that the valve body 18b together with the Bore 19b / 3-way valve forms.

The valve body 18c connects the working opening 51c with the Channel 31e and the working opening 51d with the ventilation channel 44e when the valve body 18c is moved to the left and reverses these fluid connections when the valve body 18c is adjusted to the right. The valve body 18c and the bore 19c thus together form a four-way valve.

Pig. 1 shows that the neutral flow channels 34a, 34b and 34c are narrowed by a valve body web 54a, 54b, 54c or 54d, when any of the valve bodies is adjusted so that it has fluid from a channel 31 of a work port feeds. On the other hand, there is no adjustment of a valve body during which no connection is established between a working opening and a pressure supply channel Throttling of the neutral flow channel 34, since the webs 55a and 55b are made shorter.

When any one of the valve bodies 18 is shifted to the left, one of the working openings 51 becomes the pressure supply channel 31 connected. With such a displacement of any of the valve bodies 18, the neutral flow channel 34 is also throttled or blocked off, since one of the webs 54 is

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with cooperating section of the corresponding valve bore 19 arrives. A throttling of the neutral flow channel 34 leads to a pressure gradient from the inlet opening 30 and the pressure supply channel 31 to the inlet opening 40 of the mass flow control device 11, i.e. that a differential pressure is generated between these two points.

This was caused by a throttling of the neutral flow channel 34 Differential pressure acts to actuate the differential pressure of the Pistons 22 on opposite piston ends. The higher pressure acts on the pressure application surfaces 58a and 58b, the first Form fluid-operated actuating device. The lower pressure that results from the throttling of the neutral flow duct 34 caused pressure gradient, acts on the end faces 59a and 59b, which a second fluid-actuated Form adjusting device. This lower pressure prevailing at the inlet opening 40 becomes the second adjusting device 59a, 59b are supplied via a bore 60.

The pressure applied to the second fluid-actuated adjusting device 59a, 59b is through a seal 62 on a Prevented escape to the left past the web 61 of the plug 24. The web 61 also serves as a stop for the preload spring 23, which pushes the piston 22 to the right into the fully open position.

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With an increase in the pressure gradient in the neutral flow channel 34 _f as it results from a displacement of a valve body 18, the force of the pretensioning spring 23 is overcome, whereby the piston 22 is moved to the left into a throttling position. The throttle position of the piston 22 depends on the pressure gradient that the fluid experiences when flowing through the neutral flow channel 34. The piston 22 throttles the mass flow in such a way that the pressure in the pressure supply channel 31 and supplied to the fluid-operated actuating device 58 generates a force which is equal to the force of the spring 23 plus that pressure force exerted by the fluid-actuated actuating device at the inlet opening 40 59 acting pressure is generated. At the mass flow control device 11 there is therefore a throttling effect which limits the mass flow through the neutral flow duct 34 according to the flow capacity of the neutral flow duct 34, which is dependent on the setting of the valve bodies 18, and the valve bodies 18 are capable of pressure differences between the pump and the sump in the order of magnitude of 150 to 200 kp / cm, but the pressure difference directly controlled by the valve bodies is low, for example 7 kp / cm, and this pressure difference controls the piston 22, which in turn regulates the high pressure drop.

Thus, the hydrodynamic acting on the valve body 18 Equilibrium forces are considerably reduced, since that

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The pressure gradient set on the valve bodies is only a fraction of the total pressure gradient, so that the of the neutral flow channel acting on the valve body to a fraction of the normal, in the middle position open valves occurring actuating forces can be reduced.

High pressure differences in neutral flow channels often lead to deformation of valve housings, with the result that the Fix the valve body. If there was a high pressure gradient between the first opening 32b and the second opening 35b for example, to bend the lip 63 downwards onto the web 54b seek, which leads to a pests setting of the valve body 18b in the bore 19b, so that a stronger centering spring in the cap 20 would be required. In the hydraulic system according to the invention, however, a strong centering spring can be dispensed with which is a further reason that in the hydraulic system according to the invention only low valve body actuation forces required are.

In addition to the lower valve body actuation forces, there is another advantage of the hydraulic system described in that the flow in the secondary flow from the pump 12 to the sump 14b is inversely proportional to the displacement a valve body 18 is. Therefore, the remaining mass flow that of the working opening 51 is one from the neutral position

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displaced valve body 18 is supplied, directly proportional the displacement of the valve body 18, independently of the one for actuating the one associated with the working opening 51 Fluid motor required pressure. Compared to conventional valves, this provides a more refined controllability achieved.

Finally, it is the fluid pressure delivered by pump 12 only as large as it is for adjusting the fluid motor connected to a working opening 51 load is required and the excess amount of fluid is controlled by the mass flow control device returned to the sump 14b.

FIG. 2 shows a modification of the exemplary embodiment according to FIG. 1, according to which the control valve 110 and the mass flow control device 11 can be arranged in separate housings. The mode of operation of the embodiment of FIG. 2 is the same as in the embodiment according to FIG. 1, except that the mass flow control device 11 is upstream of the neutral flow channel 134, which consists of the channel sections 134a and 134b, and not downstream of the Neutral current channel, as is the case with the exemplary embodiment according to FIG. 1.

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The neutral current arrives from the pump 112 via the lines 128 and 129, the inlet opening 140, the throttle channel 147, the outlet channel 141, the line 170, the first opening 133a, the neutral flow channel 134a, the second opening 135a, etc. to the Ventilation channel 144a, the outlet opening 145a, the line 146a and finally to the sump 114b.

In both exemplary embodiments, the individual neutral current channels are connected in series between the pump and the sump and are in series with the mass flow control device. Furthermore, in both exemplary embodiments, the one fluid-actuated adjusting device is at one end of the Neutral flow channel and the other fluid-operated actuator connected to the other end of the neutral flow channel. That is, with regard to the control of the mass flow through the neutral flow channel, the mass flow control device is connected in series with the neutral current channel, with respect to their adjustment effected by the neutral current channel however, they are connected in parallel to the neutral current channel.

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Claims (6)

Dr. I π P -1, JORC-. •. "AR., 'LR CORPORATIOIv
20J ooutn Michigan Avenue
Caica. ^ O, 111.ο3οΟ'4, U3A Müiicne: July 13, 19 7 3 Attorney File M-2744 Patent claims Λ ») Hydraulic system in which a pressure medium source, a fluid sump, a control valve with a neutral flow channel running between the pressure medium source and the sump to produce a variable throttling effect and a pressure gradient between the pressure medium source and the sump, and a fluid-operated consumer are connected to one another by a common circuit, characterized by a mass flow control device (11, 111) connected in series with the neutral flow channel (34-a, b, c) through which, together with the channel, a flow path from the pressure medium source (12,112) to the sump (Ha, Hb, 1Hb) can be produced and one fluid-operated adjusting device (22) and one pretensioning device (23) for adjusting the control device (11, 111) as a function of the pressure gradient and one the adjusting device -16-30988A / 0637 (22) with the channel (34a, t>, c) connecting fluid passage (60), the mass flow from the pressure medium source (12,112) to the sump (Ha, b, 114b) through the Control device (11,111) can be adjusted as a function of the pressure difference caused by the throttling effect. 2. Hydraulic system according to claim 1, characterized in that that the control valve (10) has valve bodies (I8a, b, c), the die- from a neutral position in which / fluid inflow to the fluid-operated consumer (working openings 51a, b, c, d) is blocked, in a throttled fluid inflow setting working position are displaceable. 3. Hydraulic system according to claim 1 or 2, characterized in that that in the housing of the control valve (10) a valve bore penetrating the working openings (51a, b, c, d) of the control valve (I9a, b, c) is formed, in which a valve body (I8a, b, c) is movably arranged when it is displaced from a neutral position to a working position a variably throttled fluid connection between an inlet opening (30) of the control valve (10) and the working opening can be produced that a neutral flow channel in the housing (34a, b, c) with a first opening (33a) connected to the inlet opening (30) and a second, -17-309884 / 0637 with the sump connected opening (35a) is provided, wherein by interacting sections of the Valve housing, the valve body and the neutral flow channel in the neutral position of the valve body an unthrottled Fluid flow from the inlet opening to the sump adjustable when the valve body is displaced (18), however, the flow of fluid is throttled or shut off in the direction of a working position and thereby a mass flow reduction and a pressure difference between the first and second openings (33a, 35a) of the neutral flow channel is adjustable, and that the flow rate control device (11,111) contains: a mass flow control piston (22) slidingly arranged in a bore, in its fully open position an unimpeded one Mass flow from an inlet to an outlet opening (40, 41) is made possible and when it is adjusted the fluid connection between these openings (40, 41) is throttled or blocked in a throttling position, a biasing device (23) by which the piston is pushed to its fully open position, first and second fluid-operated actuating devices (58a, 58b and 59a, 59b) to move the mass flow control piston (22) from its fully open position into the throttle position depending on the differential pressures applied to the actuating devices, and a fluid passage (Bore 60) through which the second fluid actuator 309884/0637 activated adjusting device (59) with the second opening (35a) of the bypass duct is connected and thus the displacement of the piston (22) from the fully open position into the throttle position by the fluid-operated Adjusting devices (58,59) can be controlled and thereby the mass flow from the pressure medium source (12,112) to the sump (.14a, Hb, 1 Hb) depending on the displacement of the valve body (18) and thus of that caused by the throttling of the neutral flow channel (34a, 34b, 34c) caused the pressure difference between the first and second opening (33a, 35a) of the neutral flow channel is adjustable. 4. Hydraulic system according to claim 3, characterized in that the control valve (10) has first and second working openings (51) and the valve body (18) from its neutral position into first and second operating positions is displaceable, in which a fluid connection from the pressure medium source to the first or second working opening is made, and that the neutral flow channel (34) oei a displacement of the valve body (18) throttled to any of its operating positions and a pressure differential between the first and second ports (33a, 35a) of the / .stromkanal can be produced and as a result, when the valve body (18) is displaced in the direction of any of its operational divisions of the quantity -19- 309884/0637 flow control piston (22) in the direction of its throttle position adjustable and thereby the mass flow from the pressure medium source to the sump through the mass flow control device (11,111) can be regulated. 5. Hydraulic system according to claim 3 or 4, characterized in that that the control valve (10) contains several Arbeitsabsehnitte, each with a working opening (51), a valve body (18) and a neutral flow channel (34), the neutral flow channels between the pressure medium source (12) and the sump (14b) one behind the other and in series with the mass flow control device (11,111) are switched, and that the first opening (33a) one of the series-connected neutral flow channels via a Fluid connection (31) to the first fluid operated Adjusting device (51) is connected -and in one the pressure medium source with one of the Working openings connecting actuation of any one of the valve bodies (18) of one of the neutral flow channels can be throttled and between the fluid connection (31) and the fluid passage (60) and between the first and a second adjusting device (58, 59) can be used to set a pressure difference by means of which the mass flow control piston (22) can be actuated in the direction of its throttle position. 309884/0637 6. Hydraulic system according to claim 4, characterized in that the control valve (10) contains several working sections, each of which has a valve body (18), a neutral flow channel (34) and at least one working opening (51), that one of the working sections has first and second working openings and a valve body (18) which can be displaced from a neutral position into first and second operating positions and, when it is displaced from the neutral position, a fluid connection can be established from the pressure medium source to the first or second working opening and the neutral flow duct (34) can be throttled so that the neutral flow ducts are connected between the pressure medium source and the sump one behind the other and in "series with the mass flow control device (11, 111), and that control channels (31, 60) are connected to the series-connected neutral flow channels, through which the on any or all of the neutral flow channels existing differential pressures the flow The flow control piston (22) can be adjusted in the direction of its throttling position due to the differential pressures caused by actuation of any valve body (18) connecting the pressure medium source to one of the working openings. 30988W0637