KR20030046752A - Holding valve apparatus for excavator and its oil pressure control method - Google Patents

Abstract

PURPOSE: The process of controlling hydraulic pressure of a holding valve is provided to prevent the open pressure of a holding valve from being influenced by the load pressure of a hydraulic cylinder by installing an additional switching valve, therefore to minimize oil leakage and properly control the hydraulic pressure of the holding valve. CONSTITUTION: The holding valve for controlling the hydraulic pressure contains: a main poppet(17) inserted into a control valve housing(32); a plug(20) provided with an orifice(21) at one side and inserted into an inner space of the main poppet; a poppet sheet(23) provided with a pressure discharging room(13) and inserted into inner holes of both housings; a poppet(14) inserted into the inner hole of the control valve housing(32) and installed at the other side of a spring(22); a piston(24) adjacent to the end of the poppet(14) and inserted into the side hole of the holding valve housing(16) and then fitted into a piston guide(33); a holding valve containing a piston guide(33) and a piston(26); a socket(35) installed inside the lower hole of the holding housing; a switching valve comprising a sub spool(27) sticking to a plug(34) and inserted into the inside of the socket(35); a pilot port(18) connected to a pilot room A and a pilot room B; a pressure room(36) located between a piston guide(33) and a piston(25); a tank port(37) passing through the lower hole of the housing.

Description

Holding valve apparatus for excavator and its oil pressure control method}

The present invention relates to a holding valve device for an excavator and a hydraulic control method of the holding valve, and by additionally installing a separate switching valve on the flow path from the back pressure chamber of the holding valve to the tank, it is always open at a constant pilot pressure with a low leakage It relates to a holding valve device and a hydraulic control method of the holding valve.

Figure 1 is a reference diagram showing the configuration of a general excavator, Figure 2 shows a hydraulic circuit diagram showing the operation principle of a general holding valve, a boom (3), arm (2) in the upper body of the excavator, which is a kind of construction equipment And a work device such as a bucket 1 are provided, and the worker can perform a desired excavation work by appropriately combining the movements of these work devices.

In addition, these high pressure hydraulic oils (hereinafter referred to as "pressure oil") discharged from the hydraulic pump (7) directly connected to the engine of the excavator, the working device such as boom (3), arm (2), bucket (1) It is to be operated by zooming the hydraulic cylinder 19 connected to the work device through (8).

On the other hand, the boom (3) and the arm (2) is the oil inside the hydraulic cylinder (19), the control valve (8) and the hydraulic hose (11) connecting the hydraulic cylinder (19) by the self load and the load of the excavator control valve Partial leakage through the gap between the spool and the housing causes a natural fall even during neutrality, which is not desirable in view of safety and work efficiency.

Therefore, the component developed to prevent the natural fall phenomenon in the neutrality of the boom (3) and the arm (2) is a "holding valve 10", the holding valve 10 and the hydraulic cylinder (19) It is installed between the control valve side end of the hydraulic hose 11 connecting the control valve 8 and the corresponding discharge port of the control valve so that oil leaks from the hydraulic cylinder 19 to the control valve 8 side when the equipment is neutral. It serves to block.

Referring to Figures 2, 3, 4 simply look at the operation of the holding valve 10 as follows.

When the equipment is neutral, oil from the hydraulic cylinder 19 flows into the back pressure chamber 13 through the orifice 12 on the side of the holding valve main poppet 17. The pressure oil flowing into the back pressure chamber 13 is prevented from flowing any more because the sub spool 15 or the poppet 14 of the holding valve blocks the passage flowing into the tank 9, which is formed around the main poppet 17. Due to the pressure balance, the main poppet 17 is kept closed to prevent leakage from the hydraulic cylinder 19.

In addition, when the equipment is operated and oil has to flow from the hydraulic cylinder 19 into the control valve 8, the pilot pressure for activating the corresponding spool of the control valve 8 is simultaneously controlled by the pilot port of the holding valve 10. 18. The pilot pressure opens the spool 15 or the poppet 14, and the pressure inside the holding valve back pressure chamber 13 flows into the tank, causing the pressure inside the back pressure chamber 13 to flow to the tank. Since the main poppet 17 is opened by this, the hydraulic oil from the hydraulic cylinder 19 flows to the tank 9 through the control valve 8 inside.

Holding valve 10 is operated in the same principle as above, basically the principle that the main poppet 17 is open is the same.

According to the difference of the method of flowing oil filled inside the holding valve back pressure chamber 13 into the tank 9, it can be largely divided into a poppet type holding valve and a spool type holding valve.

However, the two types of holding valves have some problems in operation as follows.

First, since the poppet type holding valve (see FIG. 3) prevents the flow of oil from the holding valve back pressure chamber 13 to the tank 9 by the poppet 14, the amount of leakage from the hydraulic cylinder 19 is small. However, when the pilot pressure pushes the poppet 14 inside to open the holding valve, the pilot pressure must be increased or decreased according to the high and low load pressure applied to the hydraulic cylinder 19. Since the holding valve is opened by pushing), the holding valve cannot be opened at a constant pilot pressure at all times, which may be problematic.

For example, in the case of lifting a heavy object using an excavator, high pressure is applied to the large chamber side of the boom cylinder 6 even when neutral due to the heavy weight and the weight of the boom 3.

In addition, when the boom is to be lowered, the pilot pressure for operating the boom lowering spool of the control valve must be operated at the same time as the boom holding valve to open the holding valve before the boom (3) moves. ), The holding valve 10 is opened later than usual, so that oil flowing from the large chamber 38 side of the boom cylinder 6 to the control valve 8 lowers the boom 3. It is not compressed at the beginning of the operation and is compressed, but as soon as the holding valve 8 is opened, it rapidly flows through the control valve 8 into the tank, causing the boom 3 to suddenly descend, causing the equipment to falter and overturn. The disadvantage is that you may be in a situation.

Secondly, the spool-type holding valve (see FIG. 4) prevents the flow of oil from the holding valve back pressure chamber 13 to the tank 9 by the spool 15, and the spool 15 inside the holding valve is hydraulically structural. Since the open type is not affected by the cylinder 19 side load pressure, the main poppet 17 can be opened at a constant pilot pressure at all times without being affected by the high and low load pressure applied to the hydraulic cylinder 19.

On the other hand, since the oil pressure from the hydraulic cylinder 19 can leak to the tank 9 through the gap between the holding valve housing 16 and the spool 15, there is always some leakage even if the main poppet 17 is not opened. Therefore, compared with the poppet-type holding valve, the natural drop amount of the hydraulic cylinder 19 has a disadvantage.

An object of the present invention for solving the above problems is to eliminate the disadvantage that the opening pressure of the holding valve is affected by the load pressure of the hydraulic cylinder pointed out as a disadvantage of the poppet type holding valve while applying the poppet type holding valve. It is an object of the present invention to provide a holding valve device and a hydraulic control method of the holding valve by additionally installing a separate switching valve on the flow path from the back pressure chamber of the holding valve to the tank.

1 is a reference diagram showing the configuration of a typical excavator,

2 is a hydraulic circuit diagram showing an operation principle of a general holding valve;

3 is an internal structure diagram of a conventional poppet-type holding valve,

4 is an internal structure diagram of a conventional spool type holding valve,

5 is an internal structural diagram of a holding valve according to the present invention.

<Description of the symbols for the main parts of the drawings>

(1): bucket (2): arm

(3): boom 4: bucket bucket

(5): arm cylinder (6): boom cylinder

(7): main pump (8): control valve

9: tank 10: holding valve

(11): hydraulic hose 12: orifice

(13): back pressure chamber (14): poppet

15: spool 16: holding valve housing

(17): main poppet (18): pilot port

(19): hydraulic cylinder 20: plug

(21): Orifice 22: Spring a

(23): Poppet seat (24): Piston a

(25): Spring b (26): Piston b

(27): sub spool (28): spring c

(29): niche (30): pilot room a

(31): Pilot chamber b (32): Control valve housing

33: piston guide 34: plug

(35): Socket 36: Pressure chamber a

(37): tank port (38): large chamber

The apparatus of the present invention, which achieves the above object and accomplishes a problem for eliminating the conventional drawbacks, has a working device such as a boom 3, an arm 2, a bucket 1, and is directly connected to the engine. The high pressure oil discharged from the hydraulic pump 7 is mounted to the boom 3 and the arm 2 of the excavator operated by moving the hydraulic cylinder 19 connected to the work device through the control valve 8. In poppet type holding valve,

The poppet-type holding valve is characterized in that it is connected to the switching valve opening at a constant pilot pressure on the flow path from the back pressure chamber to the tank.

The connection configuration of the poppet-type holding valve and the switching valve

A main poppet (17) fitted into a hole in the control valve housing (32),

A plug 20 inserted into an inner space of the main poppet 17 and screwed and having an orifice 21 bored at one side thereof;

The poppet seat 23 is inserted into both housing inner holes at the upper hole boundary of the holding valve housing 16 in contact with the control valve housing 32 to be spaced apart from the main poppet 17 by a predetermined distance to form the back pressure chamber 13. )Wow,

A poppet (14) inserted into an inner hole of the control valve housing (32) side of the poppet seat (23) and installed at the other end of a spring (22) provided at one end of the plug (20);

A piston a (24) inserted into the holding valve housing (16) side hole of the poppet seat (23) and in contact with the end of the poppet (14) and fitted into the piston guide (33);

A holding valve part including a piston b 26 installed at a predetermined interval by the piston guide 33 and the spring b 25;

A socket 35 installed inside a hole formed below the upper hole of the holding valve housing 16;

One side is inserted into the inside of the socket 35, the switching valve portion consisting of a sub-spool (27) which is in contact with the plug 34 in contact with one side of the spring c (28) is caught on the other side of the socket 35,

A pilot port 18 formed in communication with the pilot chamber a 30 and the pilot chamber b 31 along a flow path inside the holding valve housing 16;

The pressure chamber a 36 formed in the space between the piston guide 33 and the piston b 25, the clearance between the piston a 24 and the piston guide 33, and the holding valve housing so as to communicate with the internal flow path. It characterized in that it is connected to the tank port 37 formed through the lower hole of the (16).

The cross-sectional area of the gap 29 between the main poppet 17 and the plug 20 is smaller than the cross-sectional area of the orifice 21 of the plug 20 side.

Hydraulic control method of the present invention

It is equipped with work equipment such as boom (3), arm (2), bucket (1), and the high pressure oil discharged from the hydraulic pump (7) directly connected to the engine is connected to the work equipment through the control valve (8) In the hydraulic control method of the poppet-type holding valve mounted on the boom (3) and the arm (2) of the excavator operated by moving the hydraulic cylinder 19,

Sub-spools 27 in the switching valve which are opened only under a predetermined holding valve opening pilot pressure are provided on the flow path from the back pressure chamber of the holding valve to the tank, and the back pressure chamber 13 is switched. The hydraulic control method is characterized in that the holding valve is opened only when the oil from the final flow to the tank port 37.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 5 shows the internal structure of the holding valve according to the present invention, the configuration of the holding valve of the present invention, the main poppet (17) is fitted into the hole in the control valve housing 32, the main poppet (17) Prevents the flow of pressurized oil from the hydraulic cylinder 19 to the control valve.

The plug 20 is screwed into the inside of the main poppet 17, and a spring a 22 is positioned between the plug 20 and the poppet 14.

The spring a 22 serves to seat the main poppet 17 and the poppet 14 on the seat surface of the control valve seat surface and the poppet seat 23, respectively.

The end of the poppet (14) is in contact with the end of the piston a (24), the piston a (24) is fitted in the piston guide (33), and the spring b (25) between the piston guide (33) and the piston b (26). ) Is installed.

Referring to the bottom of the holding valve housing 16 of FIG. 5, a sub spool 27 is installed therein, and a spring c 28 is installed between the sub spool 27 and the socket 35 so that the sub spool 27 is provided. Is in close contact with the plug 34 located on the right end.

In addition, the pilot port 18 communicates with the pilot chamber a 30 and the pilot chamber b 31 along the flow path inside the holding valve housing 16, and the pressure chamber a 36 is connected to the piston a 24. It communicates with the tank port 37 via the clearance between the piston guides 33, and an internal flow path.

Referring to the operation of the present invention having the configuration as described above are as follows.

The holding valve on the boom 3 side will be described as an example.

When the boom 3 is not moving and neutral, the hydraulic oil coming from the large chamber 38 side of the boom cylinder 6 is located at the side of the holding valve main poppet 17, the main poppet 17 and the plug 20 Into the back pressure chamber 13 through the orifice 21 which is drilled in the gap between the gap 29 and the plug 20 side.

At this time, since the poppet 14 is firmly seated in the poppet seat 23 by the spring a 22, the pressure oil filled in the back pressure chamber 13 can no longer flow, so the main poppet 17 is driven by pressure balance. It is securely seated on the seat face of the control valve housing 32 so that the hydraulic oil on the boom cylinder 6 large chamber 38 side cannot leak into the control valve, so that the natural drop of the boom cylinder 6 hardly occurs.

When the boom 3 is lowered, the hydraulic oil coming from the large chamber 38 side of the boom cylinder 6 is located at the side of the holding valve main poppet 17, between the main poppet 17 and the plug 20. The orifice 21 drilled into the gap 29 and the plug 20 enters the back pressure chamber 13.

At the same time, the boom lowering pilot pressure, which operates the boom spool of the control valve to the lowering side, flows into the pilot chamber a 30 and the pilot chamber b 31 through the pilot port 18. (26) is pushed to the left, and the poppet (14) is opened by the piston a (24) pushed by the piston b (26), and some of the hydraulic oil filled inside the back pressure chamber (13) serves along the inner flow path. It flows to the side groove part of the spool 27 and waits for the other part to leak through the gap between the piston a 24 and the piston guide 33 and leak to the tank port 37 through the inner flow path. Since the clearance between the piston a (24) and the piston guide (33) is so small that the amount of leakage is not small enough to open the main poppet (17).

At this time, the sub spool 27 is also pushed to the left by the boom lowering pilot pressure introduced into the pilot chamber b 31, but the pressure starting to push is set higher than that of the piston b 26 so that the side of the sub spool 27 is lower. The pressure oil which is waiting in the groove portion flows to the tank 9 through the tank port 37 through the flow path inside the spool 27 through the groove of the left end of the sub spool 27 after the sub spool 27 is switched. do.

When the hydraulic oil flows to the tank 9, the pressure inside the back pressure chamber 13 drops, and the main poppet 17 opens while pushing to the right due to the pressure balance from the large chamber 38 side of the boom cylinder 6. Since the pressure oil flows into the control valve and flows into the tank 9, the boom 3 can be lowered.

The difference between the holding valve of the present invention and the conventional holding valve is mentioned below.

As shown in FIG. 5, the structure of the upper part of the holding valve of the present invention is almost similar to that of the poppet-type holding valve. When the opening point of the holding valve is set as a reference when the cylinder pressure is high, the cylinder pressure is low. Since the holding valve is opened even at a low pilot pressure, there may be a problem that the boom begins to descend much earlier than the actual boom lowering is intended.

On the contrary, if the holding valve opening time is set as a reference when the cylinder pressure is low, the boom cylinder (6) may be opened when the cylinder pressure is high, since the holding valve may be opened much later than when the actual boom lowering should be started. ) Oil may be compressed on the large chamber side and flow suddenly, which may cause problems such as severe shaking of the equipment.

However, since the holding valve of the present invention adds a separate switching valve as shown in the lower part of FIG. 5, the sub spool 27 inside the switching valve must open to pass the poppet 14 through the back pressure chamber 13. The oil inside the air can escape to the tank port 37 side, and the sub spool 27 is always unaffected by the high and low cylinder pressure, so it can always be opened at a constant pilot pressure.

That is, the conventional poppet-type holding valve is always influenced by the cylinder side pressure and the opening time is changed. However, the holding valve of the present invention can be opened at a predetermined holding valve opening pilot pressure without being affected by the cylinder side pressure. It is a big difference.

As another difference, there is a difference in the structure of the main poppet (17) part, in the case of the existing holding valve, as shown in Fig. 3 or 4 when the pressure oil of the cylinder side flows into the back pressure chamber only on the poppet (17) In the holding valve of the present invention, the oil pressure from the cylinder side passes through the hole on the side of the main poppet 17 to fill the gap 29 between the main poppet 17 and the plug 20. It passes through the orifice 21 of the side of the plug 20, the structure is introduced into the back pressure chamber (13).

In addition, the cross-sectional area of the gap 29 between the main poppet 17 and the plug 20 is much smaller than the cross-sectional area of the orifice 21 on the side of the plug 20, even if foreign matter is mixed in oil orifice 21 ) Before passing through the gap (29) is filtered so that the filter serves as a filter.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, the present invention provides a structure in which the holding valve can be opened at a constant pilot pressure at all times, and also reduces the internal leakage amount, thereby preventing it from being operated suddenly when the boom is lowered or arm squeezed. have.

In particular, it can reduce the risk of equipment overturning during heavy lifting by excavators, and it can provide comfort to excavator operators by reducing the fluctuation of equipment due to rapid operation.

In addition, by providing a separate filter inside the main poppet 17, it is also possible to obtain an effect that can prevent the malfunction caused by the blockage of the orifice 21 in advance, and thus the industrial effect is expected.

Claims (3)

It is equipped with work equipment such as boom (3), arm (2), bucket (1), and the high pressure oil discharged from the hydraulic pump (7) directly connected to the engine is connected to the work equipment through the control valve (8) In the poppet-type holding valve mounted to the boom (3) and arm (2) of the excavator operated by moving the hydraulic cylinder (19), a) the main poppet (17) fitted into the hole inside the control valve housing (32), A plug 20 inserted into an inner space of the main poppet 17 and screwed and having an orifice 21 bored at one side thereof; The poppet seat 23 is inserted into both housing inner holes at the upper hole boundary of the holding valve housing 16 in contact with the control valve housing 32 to be spaced apart from the main poppet 17 by a predetermined distance to form the back pressure chamber 13. )Wow, A poppet (14) inserted into an inner hole of the control valve housing (32) side of the poppet seat (23) and installed at the other end of a spring (22) provided at one end of the plug (20); A piston a (24) inserted into the holding valve housing (16) side hole of the poppet seat (23) and in contact with the end of the poppet (14) and fitted into the piston guide (33); A holding valve part including a piston b 26 installed at a predetermined interval by the piston guide 33 and the spring b 25; b) a socket 35 installed inside the hole formed below the upper hole of the holding valve housing 16; One side is inserted into the inside of the socket 35, the switching valve portion consisting of a sub-spool (27) which is in contact with the plug 34 in contact with one side of the spring c (28) is caught on the other side of the socket 35, c) a pilot port 18 formed in communication with the pilot chamber a 30 and the pilot chamber b 31 along the flow path inside the holding valve housing 16; d) holding the pressure chamber a 36 formed in the space between the piston guide 33 and the piston b 26, the clearance between the piston a 24 and the piston guide 33, and the internal flow path. By connecting to the tank port 37 formed through the lower hole of the valve housing 16, the switching valve is configured to open at a constant pilot pressure on the flow path from the back pressure chamber of the poppet-type holding valve to the tank Holding valve device. The method of claim 1, The holding valve device for an excavator, characterized in that the cross-sectional area of the gap 29 between the main poppet 17 and the plug 20 is smaller than the cross-sectional area of the orifice 21 on the side of the plug 20. It is equipped with work equipment such as boom (3), arm (2), bucket (1), and the high pressure oil discharged from the hydraulic pump (7) directly connected to the engine is connected to the work equipment through the control valve (8) In the hydraulic control method of the poppet-type holding valve mounted on the boom (3) and the arm (2) of the excavator operated by moving the hydraulic cylinder 19, Sub-spools 27 in the switching valve which are opened only under a predetermined holding valve opening pilot pressure are provided on the flow path from the back pressure chamber of the holding valve to the tank, and the back pressure chamber 13 is switched. Hydraulic control method of the holding valve for excavators, characterized in that the hydraulic control method to open the holding valve only when the oil from the final flow to the tank port (37).