KR20190098992A - Hydraulic servo mechanism - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servomechanism for hydraulic drive of a direction control valve used in the manufacture of a mobile vehicle, and in particular, an object of the present invention is an area difference servomechanism without a vibration phenomenon. An area difference compensation system is provided, and a reduction pressure chamber and a supply pressure chamber are also appropriately arranged which partition the cavity of the spool present along the servo mechanism. The area difference is obtained through an area change formed along the spool inside the chamber connected to the reduced drive line.

Description

Hydraulic servo mechanism

The present invention relates to a servomechanism for the hydraulic drive of a directional control valve used in the manufacture of a mobile vehicle, and in particular, the object of the present invention is to reduce the thrust work by the operator to avoid the vibration of the servomechanism It is a servo mechanism.

Operation of the servomechanism is performed by an operator driving a mobile vehicle with a mechanical movement mechanism controlled by a lever or a pedal.

A first prior art example is described in patent EP1777419, where a reduced pressure is applied to the entire diameter of the spring and the spool itself so that the force generated acts on the spool to resist the operation performed by the operator. . The force generated by the reducing pressure acts against the inner spring to regulate the spool itself.

If the servomechanism is to be used in a large machine for proper transmission of control signals, it is necessary to use a spool with a larger diameter, which can distribute higher flow rates. While maintaining the control pressure constant, as the area where such pressure acts increases, the work that the operator has to deliver to the servomechanism becomes greater to achieve the same delivery.

Many manufacturers use area difference servo mechanisms to eliminate such problems, an example of which is document EP1031780.

In a mechanism of this kind, the reducing pressure no longer acts on the overall diameter of the spool, and due to the difference in the diameter of the spool itself, such pressure is applied to the circular crown. Increasing the spool diameter also reduces the influence of thrust due to the reduced pressure acting against the operator.

A disadvantage of the prior art is related to the swing phenomenon of the control movement mechanism of the servo mechanism. This vibration phenomenon causes such a swing of the movement mechanism to operate the servo mechanism in an uncontrolled manner, which is not only a serious operating defect, but also a problem for the safety of the operator, because the vibration phenomenon is mounted on the servo mechanism. This can cause unintended operation of uncontrolled vehicles.

In order for the servo mechanism to function properly as an area difference solution, the chamber opposite the pusher must be at the same discharge pressure. In fact, if this does not happen and the same pressure is kept held, the above-mentioned vibration can be started. To achieve this connection, the prior art assumes three solutions:

The first solution is to insert, along the servomechanical cavity, a chamber for partitioning the spool below the supply pressure chamber P and the reducing pressure, and to partition the discharge line, which is related to the use of a hole or inside the main body of the servomechanism itself. In this case, additional cavities are inserted in the same servomechanical body, thereby increasing the number of conduits and / or passages and the height of the body itself resulting from processing to be formed or superimposed within the core box;

The second solution is to insert a direct discharge connection between the chamber opposite the pusher and the outside of the body of the servomechanism into the lower part of the servomechanical, so that an additional outward hole or lid for delivering the chamber only toward the outlet of the required body. And the disadvantages of the solution described above appear;

The third solution is to introduce a through hole across the entire spool, which can connect the pusher side discharge chamber to this chamber on the opposite side, which is described for example in US Pat. No. 4,566,492, the limit being Relieve all pressure exerted on such chambers while maintaining a sufficient thickness of the spool core to ensure maximum tension (limited under operating conditions) to avoid fatigue failure of the core diameter below the number of life cycles provided for this application. To get a hole with a diameter of sufficient size to pass through the spool for discharge to the side. In addition, a solution similar to the solution of the above-mentioned patent has an additional disadvantage, which appears because the reduced pressure chamber which partitions the spool in the cavity is between the level of the discharge pressure and the level of the supply pressure P.

In essence, in the differential servomechanism according to the prior art, the recess connecting the outlet and the reducing pressure region is arranged in a collar larger than the collar of the recess connecting the supply pressure to the reducing pressure itself. For this reason, it is necessary to use a deeper recess in the connection between the supply pressure and the reducing pressure to maintain the same pressure difference used in the servo mechanism without area difference, but if there is a through hole having a core diameter, There is a construction limitation that, due to structural limitations, it is not always possible to make the recess the desired depth.

It is an object of the present invention to minimize the working days of the hydraulic servomechanism with the area difference compensation system and the proper arrangement of the supply pressure chamber and the reducing pressure chamber which defines the cavity of the spool present along the servomechanism.

In particular, the embodiment of the present invention can obtain the area difference through the change of the area formed along the spool inside the chamber connected to the drive reduction line.

Another object of the present invention is to eliminate the swing phenomenon, which occurs with a channel that traverses the entire spool and pushes the chamber opposite the pusher to the discharge chamber on its side.

Another object of the present invention is to reduce the diameter of the second collar of the spool to obtain an area difference downstream of the intersection between the supply pressure chamber and the reducing pressure chamber.

 Thanks to this solution, the core length connecting the first and second collars of the spool no longer has the limitation of having to have a deeper connection recess between the supply pressure and the reducing pressure in order to maintain a proper pressure differential. Thus, it is possible to obtain a hole of sufficient size to pass through the entire spool and push out the chamber on the opposite side without affecting the tension limit of the spool itself at the level of the core diameter.

Another undesirable effect of the servomechanism is that the dynamic response is excessively fast, in order to ensure a more gradual return of the spool of the servomechanism (which can be countered if the return is too fast), the reducing pressure chamber and outlet of the servomechanism It is important to be able to narrow the connection between them, which is caused by one or more transverse holes that are formed in the spool collar and are suitable for partitioning the inner conduit.

All of the above objects and advantages are achieved and obtained with a hydraulic servomechanism having a vibration damping system which is the subject of the invention characterized by what is provided in the claims set out below.

These and other features will be further detailed in the following description of some embodiments, which are shown by way of example only and not by way of limitation in the figures of the accompanying drawings.

1 is a cross-sectional view of a hydraulic servo mechanism having no area difference according to the prior art.
Fig. 2 shows a cross section of the area difference servomechanism according to the prior art, wherein the chamber opposite the pusher is directly connected to the transverse discharge conduit which defines the chamber itself, the conduit being connected to the supply line chamber and the reducing pressure which defines the spool. It is arranged along the cavity located below the chamber.
Fig. 3 shows another cross section of the area difference servo mechanism according to the prior art, in which a through hole through the spool is pushed to connect the opposite chamber to the outlet.
4 and 4A show a cross section of an area difference servo mechanism and details thereof which are the subject of the present invention.

Referring to Figure 1, the operating mode of the hydraulic servo mechanism according to the prior art which is most widely used.

This hydraulic servo mechanism consists of the main body 1a, and a pressure reduction valve operates inside this main body.

The pressure reducing valve consists of a spool 8, springs 2a and 2b, and a plate 7, which is actuated by a pusher 4, which is integral with the drive movement mechanism 20. It is operated by the cam 5.

Three overlapping chambers which define the cavity 3 of the spool 8 are located in the body 1a, ie one chamber is in the central position 9 which is connected to the pressure line P and the other chamber is In the upper position 6, which is connected to the discharge line T, the last chamber is in the lower position, in which there is a reduced pressure generated between the two chambers 12.

Both chambers are connected to ports P and T for connecting to the pump and the outlet, respectively, located in the lower part of the servomechanism.

Specifically, the chamber 6 is connected to the discharge port T via a hole 10 located in the lower part of the chamber itself.

When the cam 5 pushes the pusher 4 downward, the pusher acts on the plate 7 so that the spring 2b is compressed, which acts on the spool 8 to bring the spool to the working position. Pushed downwards.

The first drawback is that during the above-mentioned operation, the controlled reduced pressure present in the chamber 12 resists the pusher at the spool face 13, the larger its diameter, the more the operation required by the user is. Becomes high.

The prior art provides a hydraulic servomechanism that can reduce working days even when the spool 8 needs a diameter 13 having a large diameter so that higher oil flow rates can be used along the discharge line. For reference, the features as the area difference servo mechanism according to the prior art are shown. In the main body 1b, three overlapping chambers are arranged in the following order: the centrally located chamber is connected to the reducing pressure 12, the upper chamber is connected to the outlet 6, and the lower chamber is Is connected to the supply pressure P (9). Unlike the previous solution, there is also a fourth chamber 21, which is formed at the end opposite the push along the cavity 3 of the spool 108.

The spool 108 is divided into two collars 14 and 18 separated by the core 17. The outlet 6 is connected to the reducing pressure chamber 12 via at least one recess 15, and the supply pressure chamber 9 is connected to the reducing pressure chamber via at least one recess 19.

The upper collar 14 has a larger diameter than the lower collar 18, so that the reducing pressure acting on the upper collar region 16 and the lower collar region 25 is not balanced, and the pusher 4 is actuated. This will generate upward thrust against this pusher. Since the recesses 19 are formed in the collar 18 with a smaller diameter in order to properly adjust the pressure difference between the supply chamber and the reducing pressure chamber, the recesses must be deeper, and the machining must be deeper (the core of the spool itself). There is a configuration limit that is determined by the dimension of the diameter of 17).

A further disadvantage of the arrangement of the servomechanism according to the prior art described above is that in the chamber 21, an undesirable force generated by the intervention of pressure on the lower side 103 of the spool acts on the spool 108 so that the servomechanism is reduced. This is due to the fact that control is lost. The chamber 21 needs to be connected to the discharge line 10 via the transverse conduit 23 or through the outward discharge hole 22 (one of the two measures described above is sufficient). In this solution, the complexity of the implementation becomes higher inside the body 1b of the servomechanism with respect to the number of conduits, corresponding intersections inside the body, outer connections and / or cavity integrally formed.

3, an area difference servo mechanism is shown in which the chamber 21 is through a through hole 24 formed in the spool 208 and a continuous transverse hole 26 traversing the chamber 6. Is connected to the discharge line 10. The configuration limit of the variation as shown in FIG. 3 is machine-structured, in fact, the hole 24 must be large enough to discharge all the pressure of the chamber 21 to the outlet 6 and the spool 208. Diameter of the core 17 of the core 17 ensures maximum tension (limited under operating conditions) to accommodate the appropriately sized holes 24 and also to avoid fatigue failure below the number of life cycles provided for the above-mentioned applications. It must be large enough to do so. As mentioned above, the upper limit of the core diameter is given by the depth of the recesses 19 formed in the lower collar 18 of the spool 208.

2 and 3, the connection between the chamber 6 and the chamber 12 is made through one or more recesses 15 in the upper collar 14 of the spools 108, 208. By changing such narrow passages, it is possible to control the reduced pressure release to ensure a more gradual and not too fast return of the regulating spools 108, 208 to reduce the unpleasant effects of too fast dynamics on the operator.

In view of the problems of the prior art as described above, it is an object of the present invention to provide a novel servomechanism capable of solving the above problems and minimizing machining costs. Means for solving the above-mentioned problems will be better explained with the help of Fig. 4, which shows a hydraulic area difference servo mechanism which is the subject of the present invention.

In the main body 1d, three overlapping chambers are arranged in the following order: the centrally located chamber is connected to the supply pressure 9, the upper chamber is connected to the discharge section 6, and the lower chamber is Is connected to the reducing pressure 12.

A fourth chamber 21 is formed along the cavity 3 exactly at the end opposite the pusher 4, which chamber 21 is adapted to receive the end of the spool 308 in the operating state. Here too, the cavity 21 is connected to the discharge chamber 6. In this example, such a connection is made through the through hole 24 and the transverse hole 26.

The spool 308 includes two collars, the upper collar is shown as "314" and the lower collar is shown as "318", and these collars are separated by the core 317 of the spool itself. The lower collar 318 consists of two portions 318a and 318b, the dual first portion 318a adjacent the core 317 and having the same diameter as the upper collar 314. On the other hand, the core 317 has a diameter smaller than the diameter of the upper collar 314 and the diameter of the first portion 318a of the lower collar.

The area difference used to perform the adjustment of the hydraulic servomechanism itself is no longer obtained through the difference between the two regions 316 and 325 disposed at the two ends adjacent to the core, since these two regions are the same. to be. It is no longer necessary to make deeper recesses 319 to carry out the adjustment of the reducing pressure between the supply chamber 9 and the chamber 12, because the recesses are formed in the larger diameter portion of the spool. Core 317 has a less stringent configuration limit in terms of maximum size compared to the prior case of the prior art.

The hole inside the core 317 itself can be made large enough to discharge the pressure generated inside the chamber 21 with minimal load loss.

The lower portion 318b of the collar 318 has a diameter smaller than the diameter of the adjacent upper portion 318a of the collar, and an area change 28 is formed in the collar 318 inside the chamber 12. This area change forms a narrow portion for both the first portion 318a and the second portion 318b of the collar, and now the reducing pressure of the servomechanism acts on the narrow portion. This area change portion forms a stepped portion having the same effect as the area difference formed in the servo mechanism obtained according to the prior art according to FIGS. 2 and 3.

Since the hole 24 can be made smaller in size than in the prior art, it is possible to connect and regulate the reduced pressure present in the chamber 12 to the outlet present in the chamber 6 through this hole.

The above-mentioned adjustment is made by one or more transverse holes 27 formed in the lower collar 318 of the spool 308, which defines the conduit 24. By varying the dimensions of the aperture 27, it is possible to control the release of the reduced pressure to ensure a more gradual and not timely return of the adjustment spool 308.

The chambers 6, 9, 12 are suitable for partitioning the cavity 3 along the body 1d laterally, in more detail, the chamber 9 (under working hydraulic pressure) is an intermediate chamber and reduced The pressure chamber 12 is a lower chamber.

This arrangement of the chambers 6, 9, 12 results in a hydraulic area difference servomechanism that is blunt in response to vibrations caused by residual pressure in the chamber when the chamber 21 is not properly connected to the outlet.

In addition, without strict depth limitations on the recesses 319, the diameter of the core 317 enables the construction of the inner conduit 24 without being subjected to excessive stress in terms of material tension under operating conditions and also. Wide enough to allow adjustment between the reducing pressure and the outlet.

1a, 1b, 1c, 1d body
2 springs (2a, 2b)
3 spool cavity
4 pusher
5 cam
6 discharge chamber
7 plates
8 spools
108 spool
208 spool
308 spool
9 Supply chamber (P)
10 exhaust conduit (T)
12 reducing pressure chamber
13 Lower area of the spool (8)
14 upper collar
15 Upper collar recess
16 upper collar area
17 core spool
18 lower collar
19 Lower collar recess
20 exercise equipment
21 Chamber opposite pusher
22 Outward outflow hole
23 Connection conduit of outlet 10
24 through hole
25 lower collar areas
Lower area of 113 spool 108
Lower area of 213 spool (208)
Lower area of 313 spool 308
314 upper collar
316 upper collar area
Core of 317 Spool (308)
318 lower collar
318a upper part of upper collar
318b Lower part of upper collar
319 recess of lower collar
325 lower collar area
26 Cross-holes to compartment outlet
27 reducing pressure adjustment holes
28 area change departments

Claims (8)

As the hydraulic servo mechanism 100,
a. At least one body 1d having at least one cavity 3 and at least three chambers 6, 9, 12,
Iii. The first chamber 6 of the main body is connected to the discharge line T of the main body 1d.
Can,
Ii. The second chamber 9 of the body may be connected to the supply pressure (P),
Iii. The third chamber 12 of the main body is controlled by the servo mechanism
The reducing pressure is configured to act on it;
b. At least one pusher (4) and a plate (7) coaxial with each other and freely translatable along the cavity (3);
c. Springs 2a and 2b which are coaxial and concentric with each other, respectively
Iii. Keep the plate 7 pressed against the pusher 4,
Ii. Springs 2a and 2b suitable for generating actuating thrust on spool 308
The spool 308 is slidable inside the cavity 3,
Also includes collars 314 and 318 separated by core 317; And
d. A fourth chamber 21 opposite the pusher 4 at the bottom of the spool 308,
One or more holes 24, 26 connect the fourth chamber 21 to the first chamber 6,
When the pusher 4 is actuated, the second chamber 9 and the third chamber 12 communicate through one or more recesses 319 along the first portion of the lower collar 318a,
The lower collar 318 consists of at least two parts 318a and 318b, the double first part 318a being adjacent to the core 317 and having the same diameter as the upper collar 314 , The second portion 318b of the lower collar 318 has a diameter smaller than the diameter of the adjacent portion 318a, and the core 317 is smaller than the diameter of the upper collar 314 and the first portion 318a. Has a small diameter,
Said portions 318a, 318b are separated by an area change portion 28 which forms a narrow portion for both the first portion 318a and the second portion 318b;
The servomechanism comprises at least one hole 27 in the collar 318, which defines one or more holes 24 and also allows the chamber 12 to communicate with the first chamber 6. Consisting of hydraulic servo mechanism. The method of claim 1,
The three chambers 6, 9, 12, which define the cavity 3, are laterally arranged along the body 1d, and the second chamber 9 is in an intermediate position and is of reduced pressure. The third chamber (12) is the lowest of the three chambers, the servo mechanism (100). The method of claim 1,
The one or more recesses 319 connecting the second chamber 9 and the third chamber 12 are formed in a portion 318a having the same diameter as the upper collar in the lower collar 318. 100. The method according to any one of claims 1 to 3,
A servo mechanism (100) comprising a hole (26) formed in the upper collar (314). The method of claim 4, wherein
One or more holes 27 in the collar 318 and holes 26 in the collar 314, configured to define one or more holes 24 extending axially along the spool 308. ) Has a variable diameter, the servo mechanism (100). The method according to claim 4 or 5,
The second chamber (9) is arranged in an intermediate position between the hole (26) of the upper collar (314) and the hole (27) of the lower collar (318). The method according to any one of claims 1 to 6,
The spool has a constant diameter in length between the second portion (318b) of the lower collar (318) and the end opposite the pusher (4). The method according to any one of claims 1 to 7,
The upper collar 314 and the lower collar 318 define corresponding regions 316, 325 disposed at two ends adjacent to the core 317, which regions 316, 325 have the same surface area. , Servo mechanism 100.

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