JPS6118044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure control valve suitable for mutually controlling the pressures of circuits formed by a plurality of fixed displacement pumps when a single prime mover drives the pumps.

In vehicles such as construction machines and cargo handling machines, a single prime mover may drive a plurality of constant displacement pumps and actuate actuators in respective circuit systems connected to each pump.

In this case, the sum of the load pressures of multiple pumps will act on the prime mover, so in order to prevent the prime mover from becoming overloaded, the total load of each pump must be equal to the maximum output of this prime mover. must not be exceeded.

In order to prevent this maximum output from being exceeded, when one circuit system becomes high pressure, it is necessary to control the pressure of the other circuit system to be lowered accordingly. What is shown in the figure is conventionally known.

The conventional control mechanism shown in FIG. 8 drives two pumps 31 and 32 with one prime mover 33,
Actuators 34 and 35 connected to these pumps 31 and 32 are driven.

When load pressure is generated in only one of the circuits, the pressure in that one circuit is controlled within the range of the set pressure of the high pressure relief valve 36.

Further, when load pressure is generated in the circuits on both the pumps 31 and 32 side, the circuit pressure acts on the on-off valves 39 and 40 via the pilot passages 37 and 38.

Therefore, for example, when the circuit pressure on one pump 31 side becomes equal to or higher than the cracking pressure of the on-off valve, the on-off valve 40 is switched from the illustrated closed position to the open position. When the on-off valve 40 is switched in this manner, the circuit on the other side of the pump 32 communicates with the low pressure relief valve 41, so the pressure of the other circuit is maintained within the set pressure of the low pressure relief valve 41.

The conventional control characteristics as described above are shown in FIG. For example, when one actuator 34 is currently being used near the maximum pressure P ₁ of the high pressure relief valve 36, the on-off valve 40 is open, so the pressure on the other actuator 35 side is the same as that of the low pressure relief valve 41. Controlled within the range of set pressure _P2 .
In this state, if the load pressure on the actuator 35 side exceeds the cracking pressure described above, the on-off valve 39 also opens, so the circuit pressure on the one actuator 34 side is also controlled within the range of the set pressure of the low pressure relief valve 41. It turns out.

Therefore, in this conventional control mechanism, the control is performed in stages as shown in FIG. 9, and the maximum output of the prime mover must be set at the P-C line. However, when the maximum output of the prime mover was set at the P-C line, there was a drawback that the shaded area was a complete loss of power.

Furthermore, in this conventional control mechanism, the on-off valve 3
Since a plurality of valves, 9 and 40, must be provided, there was also the drawback that the configuration was complicated accordingly.

An object of the present invention is to provide a pressure control valve that enables control with only one pressure control valve and reduces power loss.

FIG. 1 shows a first embodiment of the invention, FIG. 3 shows a second embodiment that is slightly different from the first embodiment, FIG. 4 shows a third embodiment, and FIG. A fourth embodiment is shown in FIG. 6, and a fifth embodiment is shown in FIG.

First, the first embodiment will be explained. Regarding the other embodiments, parts having the same structure as the first embodiment will be given the same reference numerals in the drawings, and only the different parts will be explained.

This pressure control valve is designed to control the circuit pressure of two fixed displacement pumps P ₁ and P ₂ driven by one prime mover E, and has two imports (pump side ports) 1x connected to the circuits respectively. , 1y is the valve body A
It is set up in

The valve body A has two valve chambers 3 whose outer openings are closed by screwing covers 2x and 2y.
x and 3y are provided on the left and right.

Inside each valve chamber 3x, 3y, a receiving chamber 4x, 4y which is continuous thereto is provided, and these two chambers are connected to the import chamber 1x, 4y by passages 5x, 5y, respectively.
1y, and are connected by a continuous path 6 provided between them.

In both valve chambers 3x, 3y, a pair of poppet valve bodies Bx, By, each having a rod _b2 integrally protruding from the tip of a truncated conical valve part _b1 , are installed inside the valve chambers 3x, 3y with the left and right sides facing in opposite directions. There is.

Each poppet valve body Bx, By has the above cover 2.
A set load is applied in advance by springs 7x and 7y, with x and 2y serving as spring receivers, and these valve parts are
b ₁ is in pressure contact with the valve seat 8x at the boundary between the valve chamber 3x and the receiving chamber 4x, or the valve seat 8y at the boundary between 3y and 4y, and the rod b ₂
pass through the receiving chambers 4x and 4y, respectively, and face into the continuous path 6, and have clearances 9x and 9y that function as chokes between them and the continuous path 6, and a clearance 9 between the tip surfaces of both rods.
A mixing chamber 10 is formed which allows fluid (hydraulic oil) to flow in from both receiving chambers 4x, 4y through x, 9y.

Therefore, in addition to the hydraulic pressure flowing into the receiving chambers 4x and 4y acting on each poppet valve body Bx and By, the hydraulic pressure flowing into the mixing chamber 10 also acts on the poppet valve bodies Bx and By. Part b ₁ valve seat 8
The receiving chamber 4x,
The truncated conical surface facing inside 4y is the main pressure-receiving surface _b3 , and the circular tip surface of the rod _b2 is the sub-pressure-receiving surface _b4 .

And the loads of springs 7x and 7y are pump P ₁ and P ₂
When one of them is under no load and the other is at the maximum limit pressure, that is, when the maximum pressure is applied only to the main pressure receiving surface _b3 , the poppet valve body Bx, to which the maximum pressure is applied, By spring 7x, 7
It is set to a value that operates against y.

It also communicates with the passages 5x and 5y, respectively,
Moreover, the mixing chamber 10
The check valve chambers 12x and 12y that communicate with the valve chambers 12x and 12y are provided with a ball check valve body 1 that allows flow from the communication passage 11 to the passage 5x or 5y, but prevents the opposite flow.
It has 3x and 13y inside. Each check valve body 1
Although springs 14x and 14y are applied to 3x and 13y, the spring loads are negligible.

The valve chambers 3x, 3y of the poppet valve bodies Bx, By are both communicated with one out port (tank side port) 15.

Therefore, when load pressure occurs on both circuit sides of both pumps P ₁ and P ₂ , the circuit pressure Px of one pump P ₁ side
flows into the import 1x, and the circuit pressure Py from the other pump _P2 side flows into the import 1y. The pressure oil that has flowed into the imports 1x, 1y flows into the receiving chambers 4x, 4y, and passes through the clearances 9x, 9y to the mixing chamber 10.
We will meet up at. The pressure oil thus merged in the mixing chamber 10 acts on the ball check valves 13x, 13y;
The pressure on the import 1x and 1y sides acts as back pressure.

Therefore, if the pressure Px of one circuit connected to the import 1x side is higher than the pressure Py of the other circuit connected to the import 1y side,
Only the other ball check valve body 13y is opened. When the ball check valve body 13y opens in this way, the pressure on the import 1y side flows into the mixing chamber 10, and the inside of this mixing chamber 10 becomes the circuit pressure Py on the import 1y side.

In this way, the pressure inside the mixing chamber 10 is reduced to
Py, the forces acting on the poppet valve bodies Bx and By are the pressure receiving area of their main pressure receiving surface b ₃ as Sr, the pressure receiving area of the sub pressure receiving surface b ₄ as St, and the spring force of springs 7x and 7y. If it is F, then it becomes as follows.

That is, for the poppet valve body 8x, Sr×Px＋St×Py＝F……(1) The formula is established, For poppet valve body 8y, Sr×Py＋St×Py＝F……(2) The formula holds true.

Therefore, the poppet valve bodies Bx and By are balanced within a range that satisfies the above equations (1) and (2), and the opening degree of both poppet valve bodies is determined at the balanced position.

If the circuit pressure Px on one pump P ₁ side and the circuit pressure Py on the other pump P ₂ side are exactly equal, then
Since the pressure in the mixing chamber 10 also becomes the same circuit pressure, the opening degrees of both poppet valve bodies Bx and By also become equal.

And in this state, for example, one pump P ₁
Even if the side pressure tries to rise, the pressure Px acting on the poppet valve body Bx will also rise, so
The opening degree of the poppet valve body Bx further increases, thereby preventing the pressure Px from increasing. In other words, the circuit pressure is controlled within a range in which the total load of both pumps P ₁ and P ₂ does not exceed the maximum output of the prime mover E.

In addition, the circuit pressure Px on one pump _P1 side is high,
When the circuit pressure Py on the other pump P ₂ side is low, if the circuit pressure Py on the other pump P ₂ side becomes even lower, the pressure inside the mixing chamber 10 will also become lower, so one poppet Valve body Bx
moves in the closing direction and reduces its opening degree.
In this way, the smaller the opening degree of one poppet valve body Bx, the more the circuit pressure on one pump _P1 side.
Px can be increased. Also in this case, control is possible so that the total load of both pumps P ₁ and P ₂ does not exceed the maximum output of the prime mover E.

Therefore, according to this embodiment, the load can be controlled within the range of the maximum output of the prime mover E, and
When one load pressure attempts to rise beyond the control range, the pressure increase is limited, and when one load pressure becomes low, the other load pressure is allowed to rise, and the second Stepless control is possible within the range of the straight line shown in the figure.

Next, the second embodiment shown in FIG. 3 eliminates the clearances 9x and 9y in the first embodiment, and
In addition, poppet type check valve bodies 16x, 16y are used in place of the ball check valve bodies 13x, 13y, and orifices or check yokes 17x, 17y are provided in the check valve bodies 16x, 16y in place of the clearances 9x, 9y, respectively. Its overall operation is the same as the first embodiment.

Next, the third embodiment shown in FIG. 4 is a poppet valve body.
Check valve chambers 12x and 12y are installed in Bx and By themselves, and the ball check valve bodies 13x and 13y in the first embodiment are installed in each of them,
This operation is also the same as in the first embodiment.

Next, the fourth embodiment shown in FIG. 5 has an import 1x and a receiving chamber 4 in addition to the configuration of the first embodiment.
A poppet valve body 18x, 18y for buffering is installed between x and between the import 1y and the receiving chamber 4y, so that even if the hydraulic pressure flowing into the imports 1x, 1y fluctuates rapidly, It is designed to be able to deal with it adequately.

That is, each poppet valve body 18x, 18y is provided with an orifice or a choke 19x, 19y, and normally the import 1x, 1 is provided through these.
The hydraulic oil from y flows into the receiving chambers 4x and 4y, but if the hydraulic pressure flowing into the import 1x suddenly increases, the poppet valve body 18x opens, and the hydraulic oil that enters the import 1x aisle 2
0, flows to the out port 15 through the valve chamber 3x of the poppet valve body Bx, and if the above occurs on the import 1y side, the poppet valve body 18y opens, and the flow flows through the communication passage 21 and the passage 2.
0, it flows to the out port 15 through the valve chamber 3x.

Next, in the fifth embodiment shown in FIG. 6, as shown in FIG. 7, one of the circuit pressures of the two pumps P ₁ and P ₂ is Pa
This is used when the other is in a relationship such that the maximum setting value Pmax is reached even though the prime mover E has surplus power when the following conditions occur. , 4y and the imports 1x, 1y, and the clearances 9x, 9y are removed, an additional pair of relief poppet valves 22x are installed between the receiving chambers 4x, 4y and the outport 15. ,22y
It's decorated.

These poppet valve bodies 22x, 22y have orifices or yokes 23x, 23y, and the hydraulic pressure spring 2 from the receiving chambers 4x, 4y flows into the rear chambers of both of them through passages 24x, 24y.
Poppet valve bodies 22x, 22 against 5x, 25y
When the valve y is closed, the hydraulic oil that has entered the rear chamber flows into the mixing chamber 10 through the communication passage 26, and the poppet valve bodies Bx and By operate in the same manner as in the first embodiment. It's summery.

Now, if the hydraulic pressure Py on the poppet valve body By side is at the maximum setting value Pmax, and the hydraulic pressure Px on the poppet valve body Bx side is below the Pa value, the hydraulic oil at Pmax will be due to the operation of the poppet valve By. The highest set pressure is maintained, and the relief poppet valve body 22y is closed through the passage 24y, and a part of it leaks from the orifice or the choke 23y and flows into the mixing chamber 10, and the poppet valve body 22x side is below Pa. So push this open.

By this opening, the mixing chamber 10 is connected to the outport 1.
5, and the hydraulic oil there flows from out port 15 to the tank without resistance.

Therefore, the working pressure of Py is Px working pressure is Pa
Below, the value of Pmax remains unchanged, and when Px exceeds the Pa value, the hydraulic oil in the mixing chamber 10 acts on the secondary pressure receiving surface b ₄ of the poppet valve element By, and the valve element By operates. , Py will decrease as Px increases. If the relationship between Px and Py is opposite to the above, Px will maintain a constant value.

As is clear from the above description, according to the pressure control valve recited in claim 1, the pressure in the pair of circuits can be controlled in an ideal state.

When controlling the pressure in a pair of circuits, for example, if the pressure in one circuit increases from a state where the pressures in both circuits are equal, the poppet valve of one of the circuits opens as the pressure increases. , suppress the increase in the circuit pressure of the one concerned.

In addition, if the pressure in one circuit is high and the pressure in the other circuit is low, and the pressure in the other circuit becomes even lower, the poppet valve body will act in the direction of closing, so the pressure in the one circuit will decrease. It is possible to rise further.

In either case, both pumps can be driven within the range of the maximum output of the prime mover, so the capability of the prime mover can be utilized to its maximum, and power loss of the prime mover can be reduced.

In addition, since control is possible with only one pressure control valve, the piping and the like are simpler than in the past, which has the advantage of simplifying maintenance and management.

According to the pressure control valve recited in claim 2, even if the pressure in one circuit rises to the maximum pressure, if the pressure in the other circuit does not rise above a predetermined pressure, the one circuit reaches the maximum pressure. Maintain high pressure. Therefore, even if one circuit pressure is used at the highest pressure, if there is still some leeway in the prime mover, the capacity of the prime mover can be utilized to its maximum.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is a sectional view of the first embodiment, and FIG. 2 is a sectional view of the first embodiment.
FIG. 3 is a sectional view showing only the parts of the second embodiment that are different from the first embodiment, and FIGS. 4 to 6 are sectional views of the third to fifth embodiments, respectively. FIG. 7 is a graph showing the correlation between two circuit pressures in the fifth embodiment, FIG. 8 is a circuit diagram of a conventional control mechanism, and FIG. 9 is a graph showing the correlation between two conventional circuit pressures. . A... Valve body, Bx, By... Poppet valve body,
b ₃ , b ₄ ... Main, sub-pressure receiving surface, 15 ... Outport, 3x, 3y ... Valve chamber, 7x, 7y ... Spring applying set load to poppet valve body Bx, By,
1x, 1y...Import, 4x, 4y...Accepting room, 10...Mixing room.

Claims (1)

[Claims] 1. A pair of poppet valve bodies having two pressure receiving surfaces, a main pressure receiving surface and a sub pressure receiving surface, are internally mounted by applying a set load to a valve chamber communicating with an out port formed in a valve body. , the main pressure-receiving surface of each poppet valve element faces the receiving chamber communicating with the import connected to each pump, and the auxiliary pressure-receiving surface faces the mixing chamber common to both poppet valve elements, and The mixing chamber is communicated with the receiving chamber via an orifice or a choke, and a check valve is provided in the passage that communicates the mixing chamber with the import to allow only flow from the mixing chamber to the import. A pressure control valve configured so that the pressure in the mixing chamber is the lower pressure of each import. 2 A pair of poppet valve bodies having two pressure receiving surfaces, a main pressure receiving surface and a sub pressure receiving surface, are installed inside the valve chamber communicating with the out port formed in the valve body, and a set load is applied to each poppet valve body. The main pressure-receiving surface faces a receiving chamber communicating with the import connected to each pump, and the sub-pressure-receiving surface faces a mixing chamber common to both poppet valve bodies, and the mixing chamber is A pressure control valve that communicates with the receiving chamber via an orifice or a choke, and communicates the mixing chamber with an out port via a relief poppet valve body in which the pressure on the import side acts as back pressure.