JPS611738A - Convergent circuit for construction vehicle - Google Patents

Abstract

PURPOSE:To prevent the occurrence of shock during the converging period by connecting the regulator of a variable oil-pressure pump with the operating pilot pressures of each control valve and a pilot pump through a switch valve to be operated by the operating pilot pressure. CONSTITUTION:A boom control valve 4 is connected in parallel at the lowest downstream to the first variable pump P1, and an arm convergence control valve 5 is connected in tandem to the control valve 4. An arm control valve 9 is connected in parallel at the lowest downstream to the second variable pump P2, and a boom convergence control valve 11 is connected in tandem to the control valve 9. The pilot pump pressure is connected to the operating pilot pressures of each control valve through a shuttle valve and the regulators 40 and 41 of both the pumps through a switch valve to be operated by the operating pilot pressure. Shock to be encountered during the convergent period can thus be prevented by controlling the flow rate of bleed.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention connects a pair of variable displacement pumps to respective circuit systems, and adjusts the discharge oil of the pump connected to one of the circuit systems as necessary. , relates to a merging circuit for a construction vehicle to be merged into another circuit system. In particular, this merging circuit is most suitable for power scissors equipped with a boom cylinder and an arm cylinder.

(Prior Art) FIG. 7 is a circuit diagram of a conventionally known merging circuit, in which variable displacement pump P1. A switching valve that controls a predetermined actuator is connected to each of P2.

That is, one variable displacement pump P1 is connected to a switching valve 1 for controlling a travel motor, a switching valve 2 for controlling a packet cylinder, a switching valve 4 for controlling a boom cylinder 3, and a merging valve 5 for increasing arm speed. ing. And the switching valve 1.
2.4 are connected in parallel via the parallel feeder 6, but only the merging valve 5 for increasing the arm speed at the most downstream side is connected in parallel via the parallel feeder 6.
It is connected in tandem to the switching valve 4.

Furthermore, a switching valve 7 for controlling the travel motor, a switching valve 8 for controlling the swing motor, a merging valve 9 for boom speed increase, and a switching valve 11 for controlling the arm cylinder 10 are connected to the other variable displacement pump P2. However, these switching valves and merging valves are connected in parallel via a parallel feeder 12.

Separately from both circuit systems as described above, a Nonoirot pump 13 is provided, and this pilot pump 13
includes a pilot operating valve 14 for traveling, a pilot operating valve 15 for swinging, a pilot operating valve 1B for boom,
The pilot operating valve 17 for the arm, the pilot operating valve 18 for the packet, and the pilot operating valve 18 for traveling are connected in parallel.

Each of these pilot operated valves outputs a pilot pressure proportional to the amount of operation thereof, and guides the pilot pressure to either the left or right pilot chamber of the switching valve depending on the direction of operation.

Note that the switching valve 11 that controls the arm cylinder 10 and the merging valve 5 have their pilot chambers communicating with each other, so by operating the pilot operating valve 17 for the arm, the switching valve 11'EL and the merging valve Pilot pressure acts on the pilot chambers of No. 5 at the same time. However, since the set pressure of the merging valve 5 is higher than the set pressure of the switching valve 11,
Even if the pilot pressure exceeds the set pressure of the switching valve 11, if it is below the set pressure of the merging valve 5, only the switching valve 11 opens and the merging valve 5 remains closed.

Also, a switching valve 4 and a merging valve 9 that control the boom cylinder 3 are provided.
The pilot pressure from the pilot operating valve 16 acts simultaneously on the pilot chambers of the two pilot chambers. In this case as well, the set pressure of the merging valve 9 is set higher than the set pressure of the switching valve 4.

Shuttle valves 20 to 25 are connected to each of the pilot operated valves 14 to 18, and the first stage shuttle valve selects the pilot pressure output from the pilot operated valve. Furthermore, the above-mentioned shuttle valves 21 and 2
2. The higher pilot pressure of 23 and 24 is selected by the second stage shuttle valves 2B and 27, and the third stage shuttle valve 28 and 29 selects the highest pilot pressure output from the pilot operated valve. It allows you to select high pressure.

Further, the shuttle valve 23 for selecting the pilot pressure of the pilot operating valve 17 for the arm is provided with a passage 30 on an extension of the passage connected to the shuttle valve 27.
The shuttle valve 23 is connected to the sequence valve 31 via.

Furthermore, the shuttle valve 22 for selecting the pilot pressure of the pilot operating valve 1B for the boom includes a shuttle valve 28.
A passage 32 is provided as an extension of the passage connected to the passage 3.
2, the shuttle valve 22 is connected to a sequence valve 33.

The above sequence valve 31% 33 has those springs 3
4.35 normally maintains the closed position, which is the normal position shown in the figure, but when the pressure inside the passage 30.32 exceeds the set pressure determined by this sequence valve, the pilot chamber 36 of the sequence valve closes. A pressure action of .37 switches the sequence valve 31.33 into the open position. When the sequence valve is switched to the open position as described above, pilot pressure from passage 30, 32 passes through this sequence valve and the fourth
It flows into the shuttle valves 38 and 39 of the stage.

This fourth stage shuttle valve 38.38 also communicates with the third stage shuttle valves 2B and 28, so the pilot pressure in the passage 30.32 and the third stage shuttle valve 2B, 28 are connected to each other.
The higher pilot pressure of the pilot pressure flowing in from 8.29 is selected by this shuttle valve 38.38.

The pilot pressure selected by the shuttle valve 38 is
The pilot pressure guided to the regulator 40 of the variable displacement pump P1 and selected by the shuttle valve 38 is guided to the regulator 41 of the variable displacement pump P2.

With such a circuit, for example, when the pilot operating valve 17 for the arm is operated, a pilot pressure proportional to the operating amount is output, and depending on the operating direction,
The switching valve 11 and the arm speed increasing merging valve 5 are switched to either the left or right side.

At this time, the pilot pressure is the shuttle valve 27, 28.
38 to the regulator tl, the discharge amount of the variable displacement pump P2 increases in accordance with the pilot pressure. Therefore, the oil discharged from the variable displacement pump P2 flows into the arm cylinder 10 via the switching valve 11 and operates the arm cylinder 10.

When the pilot pressure becomes equal to or higher than the set pressure determined by the sequence valve 31, the sequence valve 31 is switched to the switching position, so that the pilot pressure output from the pilot operation valve 17 is transferred to the regulator 4 of the variable displacement pump P1.
0, and also increases the discharge amount of the pump P1.

Therefore, the oil discharged from this one pump P1 also flows into the arm cylinder 10 via the merging valve 5, so in this state, the discharge amounts of both pumps P□ and P2 merge.

Further, when the pilot operating valve 16 is operated to operate the boom cylinder 3, the switching valve 4 is switched, and the boom speed increasing merging valve 9 of the other circuit system is also switched.

If the pilot pressure at this time is below the set pressure determined by the sequence valve 33, the variable displacement pump P of one circuit system
The discharge amount of 1 increases. When the pressure exceeds the set pressure, the sequence valve 33 is switched, so that the discharge amount of the pump P2 in the other circuit system also increases. Even when the boom pilot operation valve 1B is operated in this manner, the discharge amounts of both pumps can be combined.

In the merging circuit configured as described above, the correlation between the pilot pressure and the total discharge amount of both circulation displacement pumps is as follows.

For example, by operating the pilot operating valve 16 for the boom,
When the pilot pressure is increased, the discharge amount of one variable displacement pump P1 increases in proportion to the increase in the pilot pressure, as shown in FIG. 8(A). Then, when the pilot pressure becomes equal to or higher than the set pressure of the sequence valve 33,
Since the pilot pressure that has risen to the set pressure acts on the regulator 41 of the other variable displacement pump P2, the other variable displacement pump P2 has a pilot pressure that is higher than the set pressure, as shown in FIG. Discharges a flow rate according to the amount.

Then, by combining the characteristics in Figure 8 (a) and (b),
As shown in Figure (C), when the above pilot pressure reaches the set pressure, the discharge amount of the other variable displacement pump P2 is added, and the total discharge amount increases instantaneously. do.

(Problems to be solved by the present invention) In the conventional merging circuit described above, when the sequence valve is switched, the flow rate supplied to the boom cylinder and arm cylinder increases instantaneously, and a shock occurs at that time. There was a problem.

Additionally, if the switching valve is operated near the set pressure of the sequence valve, the flow rate supplied to the boom cylinder or arm cylinder will suddenly increase or decrease, resulting in the problem that smooth operability cannot be obtained. there were.

The object of this invention is to eliminate the shock at merging and to improve the operability at merging.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a variable displacement pump connected to each of a pair of circuit systems, and a switching system for controlling an actuator provided in each of these circuit systems. When a valve and a specific switching valve connected to at least one circuit system are switched, the actuator connected to the specific switching valve is switched in conjunction with the switching, and the pressure oil supplied to the other circuit system is switched. a pilot operating valve that outputs pilot pressure for switching the switching valve in proportion to the amount of operation, a pilot pump connected to this pilot operating valve, and a pilot operating valve that outputs pilot pressure for switching the switching valve. When the pilot pressure output from a selection mechanism consisting of a shuttle valve, etc. that selects pilot pressure and guides it to the regulator of the variable displacement pump, and a pilot operating valve connected to a switching valve that controls the specific actuator, exceeds the set pressure. At this time, in a confluence circuit of a construction vehicle equipped with a pilot control valve that guides pilot pressure to a regulator of a variable displacement pump in the other circuit system, which is different from the one circuit system, the first port of the pilot control valve is connected. communicates with the pilot pump, connects the second port to the flow path to the regulator of the other variable displacement pump, and connects the third port to the regulator of the other variable displacement pump.
When the port is connected to the tank, a variable restriction is formed in the flow path from the first port to the third port, and the pilot pressure output from the pilot operated valve connected to the specific switching valve is below the set pressure. , while cutting off the communication between the first and second ports, and controlling the opening of the variable throttle according to the pilot pressure when the pilot pressure becomes equal to or higher than the set pressure, the communication between the first and second ports is controlled. The bleed flow rate is controlled according to the opening area of the variable throttle, and a throttle is provided upstream of the variable throttle.

(Operation of the present invention) With the above configuration, when a specific switching valve in one of the circuit systems is switched, the actuator connected to the switching valve is operated. When the pilot pressure at this time becomes equal to or higher than the set pressure of the pilot control valve, the pilot control valve is switched in accordance with the pilot pressure. When the pilot control valve is switched in this way, the pilot pressure for merging control is output from the second port of the pilot control valve, but the pilot pressure for merging control at this time is controlled by the variable throttle installed in the pilot control valve. It will be controlled according to the opening degree. In other words, this variable aperture opening force 1
The larger the flow rate, the larger the bleed flow rate and the lower the pilot pressure for the merging control.

By controlling the bleed flow rate in this manner, the pilot pressure for merging can be controlled, so that shock at the time of merging can be eliminated.

(Embodiment of the present invention) Fig. 1 is a circuit diagram showing a large flow example of the present invention, and its feature is that proportional valves a and b are provided as pilot control valves in place of the conventional sequence valve. The other configurations are almost the same as the above-mentioned conventional device.

The specific configuration of these proportional valves a and b is as follows.
As shown in the figure, and since the configurations of both proportional valves a and b are exactly the same, when describing both proportional valves a and b based on FIG. 2, the same reference numerals will be used for common elements.

The proportional valves a and b have a first port 4 connected to the main body H thereof directly to the pilot pump 13 via a passage 42.
3 and a first port 43 connected to shuttle valve 38.38.
and a third port 45 communicating with the tank T.

Furthermore, a valve hole 48 is formed in this main body H, and this valve hole 4
8 are plugged with plugs 47, 48, and a partition 48 is formed at one end of this valve hole 46, and the outside thereof is a pilot chamber 50, and the pilot chamber 50 is connected to the shuttle valve 22, 23. There is.

A spool S is housed in the valve hole 4B, and a pilot plunger 51 is slidably passed through the partition wall 4θ, with the outer end of the plunger 51 facing the pilot chamber 50. Further, a spring chamber 52 is provided between the other end of the spool S and the plug 48, and a spring 53 is housed in the spring chamber 52.

The spool S thus constructed has an annular protrusion 54 at its center.
annular grooves 55 and 56 are formed on both sides of this annular protrusion 54.
In addition, the annular protrusion 54 has an annular groove 5.
A notch 57 is formed which becomes deeper toward the 8th side. When the spool S is in the normal position shown, the second port 44 and the third port 45 communicate with each other via the notch 57 and the annular groove 5B. Furthermore, when the spool S moves against the spring 53 and the annular groove 55 begins to open toward the second port 44, the notch 57 is gradually closed.

In this way, the more the spool S moves against the spring 53, the less the opening amount of the notch 57 becomes.
Eventually, this notch 57 closes completely, cutting off communication between the second port 44 and the third port 45, and together with the opening edge of the second port 44, this notch 57 forms a variable throttle. .

Note that the spring chamber 52 is communicated with the third port 45 via a communication path 58.

Further, a fixed throttle 58 is provided in the passage 42, so that even if the proportional valves a and b are opened, the pilot pressure supplied from the pilot pump 13 to the pilot operating valves 14 to 19 is
It is controlled to be constant by a constant pressure relief valve θ0.

Now, for example, if you operate the pilot operating valve 18 that controls the boom cylinder and the pilot pressure output from it becomes equal to or higher than the set pressure of the merging valve 9, the switching valve 4 and the merging valve 9 will switch, and the variable The discharge amount of the displacement pump P1 increases and the flow rate is supplied to the boom cylinder 3, as in the conventional case.

Further, the pilot pressure output from the pilot operation valve 1B is guided to the pilot chamber 50 of the proportional valve a via the shuttle valve 22, and acts on the pilot plunger 51.

Therefore, if this pilot pressure is below the set pressure determined by the spring 53, the first port 43 is closed and the second port 44 and the third port 45 communicate with each other via the notch 57. In addition, the 2.3rd port 44.45 is connected to the notch 5.
The reason for communicating through the port 7 is to release the pressure between the second port 44 and the shuttle valve 33.

In the above state, when the pilot pressure becomes equal to or higher than the set pressure, the spool S moves against the spring 53, and the first
Since the port 43 and the second port 44 are communicated with each other, the oil discharged from the pilot pump 13 flows from the fixed throttle 59 to the first port □
- port 43 → annular groove 55 → second port 44 → shuttle valve 3
9 and flows into the regulator 41. If the amount of movement of the spool S is small, the state in which the second port 44 and the third port 45 are maintained in communication via the notch 57 is maintained.

Since both ports 44 and 45 are maintained in communication with each other in this way, a portion of the flow from the pilot pump 13 is bleed off to the tank T through the notch 57.

Therefore, when the pressure oil whose pressure has been reduced by the fixed throttle 58 bleeds off from the notch 57 to the tank T, a differential pressure is generated before and after the notch 57, depending on the degree of opening of the notch 57. Therefore, the pilot pressure acting on the regulator 41 at this time is
It will be determined according to the opening degree of 7. '□ Also, as the pilot pressure acting on the pilot plunger 51 increases and the spool S moves further, the opening degree of the notch 57 gradually becomes smaller and the bleed-off to the tank T decreases. The pilot pressure generated at the 2 port 44 gradually increases as shown in FIG. 3 (b).

Therefore, the discharge amount of one variable-volume pump P1 side is:
As in the conventional case, both pumps P1. The characteristics at the time of merging of P2 become as shown in FIG. 3 (c), and the characteristics at the start of the merging become clearer. Moreover, by changing the shape of the notch 57, the slope shown in FIG. further improves its operability.

Note that the merging control of the arm cylinder IO is similar to the above-described merging control of the boom cylinder.

The second embodiment shown in FIGS. 4 and 5 has a proportional valve a,
bcy) 2nd port 44, legi! L'-Yuao, 41
The third port 45 is in direct communication with the shuttle valves 28 and 29.

Under this configuration, when the pilot operating valve 16 that controls the boom cylinder 3 is operated and neither of the pilot operating mechanisms of the other circuit system is operated, the pyro-/) output from the pilot operating valve 1B is The pressure acts on the regulator 40 of one variable displacement pump P1, increasing the discharge amount of the pump P1. If this pilot pressure is equal to or lower than the set pressure of the proportional valve a, the spool S maintains the normal position shown in the figure, and communication between the first port 43 and the second port 44 is cut off.

When the pilot pressure exceeds the set pressure described above, the spool S moves against the spring 53, and the spool S moves against the spring 53,
3.44, and the second port 44 and the third port
It communicates with the port 45 via a notch 57.

At this time, as mentioned above, none of the pilot operated valves 17 to 18 in the other circuit system is being operated, so the third port 45 is connected to the pilot operated valve via the shuttle valves 28 and 25, etc. Connects to tank T. Therefore, similarly to the first embodiment, the pilot pressure output to the second port 44 is transmitted through the fixed throttle 59 and the notch 57.
The discharge amount of the other variable displacement pump P2 is controlled in accordance with the pilot pressure output from the second port 44.

Then, from the above state, the other pilot operated valve 17
29 to 18, the pilot pressure output from the pilot operation valve concerned is controlled by the shuttle valve 29.
is guided to the third port 45 via the. In this way the third
The pressure oil guided to the port 45 flows into the spring chamber 52 via the communication path 58 and acts on the end surface of the spool S. Since the pressure receiving area of this spool end face is larger than the pressure receiving area of the pilot plunger 51,
When the pilot pressure acts on the spool end face as described above, the spool S returns to the normal position. When the spool S returns to the normal position, the first port 43 and the second port
While communication with port l-44 is cut off, communication with third port 45
communicates with the second port 44 via the notch 57. When both ports 44 and 45 are communicated in this way, the pilot pressure output from the pilot operating valve of the other circuit system acts on the regulator 41 of the other variable displacement pump P2. Therefore, even when the boom cylinder 3 is speeding up, if the actuator of the other circuit system is operated, the discharge amount of the other variable displacement pump P2 supplies the flow rate required by the actuator.

In short, when operating the actuator connected to the other circuit system on the opposite side from one circuit system to which the boom cylinder 3 is connected, the variable displacement pump P2 of the other circuit system operates the actuator of the other circuit system. The flow rate required by the system will be given priority.

This also applies to the arm cylinder 10.

6th rI! In the third embodiment shown in J, a notch 61 is formed at one end of the annular protrusion 54 of the spool S, that is, the end opposite to the notch 57, and this notch 61 forms the fixed throttle 59. It comes out.

Note that the fixed aperture 58 in each of the above embodiments may be a variable aperture.

Furthermore, the plug 48 on the spring chamber 52 side is formed with a stopper 62 that regulates the amount of movement of the spool S, and by changing the position of this stopper, the maximum discharge amount during merging control can be arbitrarily regulated. .

(Effects of the present invention) The variable displacement pump in one circuit system, which is different from the circuit system to which the actuator that requires speed increase is connected, gradually increases the discharge amount when the actuator speeds up. The flow rate supplied to the actuator increases smoothly, and no shock occurs as in the prior art.

Further, even if the switching valve is operated near the set pressure of the proportional valve, the flow rate supplied to the specific actuator will not suddenly increase or decrease, and smoother operability can be obtained.

4. Brief explanation of aspects Drawings 1 to 3 show the first embodiment. Figure 1 is a circuit diagram, Figure 2 is a cross-sectional view of the proportional valve, and Figure 3 shows the flow rate characteristics during merging. The graphs shown, Figures 4 and 5, show the second embodiment. Figure 4 is a circuit diagram of the main part, Figure 5 is a sectional view of the proportional valve, and Figure 6 is the proportional valve of the third embodiment. FIG. 7 is a conventional circuit diagram, and FIG. 8 is a graph showing flow characteristics during merging in this conventional method.

P,, P2...variable displacement pump, 1.2.4.7.8
, 11... Switching valve, 5.9... Merging valve, 14-18
...Pilot operated valve, 20-29...Shuttle valve, 40.41...Regulator, a, b...Proportional valve, 43...First port, 44...Second port,
45... Third port, 57... Notch constituting variable aperture, 58... Aperture.

Claims (1)

[Claims] A variable displacement pump connected to each of a pair of circuit systems, a switching valve that controls the actuator provided in each circuit system, and a specific switching valve connected to at least one of the circuit systems, when switched, interlocks with the switching valve. A merging valve that switches the pressure oil supplied to the other circuit system to the actuator connected to the specific switching valve, and controls the pilot pressure for switching the switching valve in proportion to the amount of operation. a selection mechanism consisting of a pilot operated valve to output, a pilot pump connected to the pilot operated valve, a shuttle valve etc. that selects the pilot pressure output from the pilot operated valve and guides it to the regulator of the variable displacement pump; When the pilot pressure output from the pilot operated valve connected to the switching valve that controls a specific actuator exceeds the set pressure, the pilot is applied to the regulator of the variable displacement pump in the other circuit system, which is different from the above one circuit system. In the merging circuit of a construction vehicle, the first port of the pilot control valve is connected to the pilot pump, and the second port is connected to the flow path to the regulator of the other variable displacement pump. At the same time, the third port is connected to the tank, and a variable restriction is formed in the flow path from the first port to the third port, so that the pilot pressure output from the pilot operation valve connected to the specific switching valve is When the pressure is below the set pressure, communication between the first and second ports is cut off, and when the pilot pressure exceeds the set pressure, the opening of the variable throttle is controlled according to the pilot pressure, and the first port is closed. and a second port, the bleed flow rate is controlled according to the opening area of the variable throttle, and a throttle is provided on the upstream side of the variable throttle.