JP2941923B2 - Directional switching valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a directional switching valve provided in a hydraulic machine such as a hydraulic shovel and provided with a pressure oil supply source having a pressure compensation function such as a load sensing system in a hydraulic machine. About.

<Prior Art> FIG. 5 is a longitudinal sectional view showing the configuration of a conventional directional switching valve of this type, and FIG. 6 is a civil engineering and construction having a load sensing system provided with the directional switching valve shown in FIG. It is a circuit diagram of a hydraulic drive in a machine.

The hydraulic drive device shown in FIG. 6 includes a variable displacement hydraulic pump 1 constituting a pressure oil supply source, a pump flow control device 2 for controlling the displacement of the variable displacement hydraulic pump 1,
A directional control valve 5 that includes an actuator driven by pressure oil discharged from the pump 1, for example, a boom cylinder 4, and another actuator (not shown), and controls a flow of pressure oil supplied from the pump 1 to the boom cylinder 4. It has.

As shown in FIG. 5, the directional control valve 5 includes a block body 6 forming a main body, a flow control valve 8 having a spool 7 sliding in the block body 6, and a flow control valve 8 The pressure difference between the inlet pressure Pz and the outlet pressure PL of the flow control valve 8, that is, the front-back differential pressure Pz-PL, is controlled to change the load pressure on the boom cylinder 4, that is, the outlet pressure. A pressure control means for supplying a constant flow rate regardless of fluctuations of the pump supply pressure Pd during PL and the combined operation, that is, a pressure compensating valve 9, and a shuttle valve 10 provided downstream of the flow control valve 8
And

The block body 6 has two pressure oil supply passages 11a and 11b connected to the pump 1, and these pressure oil supply passages 11a and 11b.
a, 11b, respectively, and load passages 12a, 12b connected to the boom cylinder 4, and these load passages 12a, 12b
And tank passages 13a and 13b that can communicate with the vehicle. Further, the spool 7 is connected to the pressure oil supply passage 11a and the load passage 12a, or is connected to the pressure oil supply passage 11b and the load passage 12b, and each meter-in is opened according to the stroke of the spool 7. First variable aperture unit 14
a, 14b, pipes 15a, 15b provided downstream of the first variable throttle portions 14a, 14b and connected to the load passages 12a, 12b, respectively, and connected to these pipes 15a, 15b. Pipe
Load pressure detection ports 17a, 17b, which are connected to these pipe lines 16a, 16b and detect the load pressure PL of the boom cylinder 4 shown in FIG.
a, 17b. The above-mentioned pipes 15a, 15b, 16a, 16b and 18 correspond to the shuttle valve 10 shown in FIG.
And a transmission passage for transmitting the load pressure PL of the boom cylinder 4 detected at the detection ports 17a and 17b as a control pressure to one drive unit of the pump flow control device 2 shown in FIG. doing. Also, the shuttle valve described above
Reference numeral 10 constitutes selecting means for selecting the maximum control pressure in the circuit. The pump pressure Pd is guided to the other drive unit of the pump flow control device 2, and the pump flow control device 2
The displacement of the pump 1 is controlled so that the pressure difference between the pump pressure Pd and the load pressure PL is balanced with a predetermined pressure difference, that is, a pressure difference ΔP corresponding to the force of the spring 22. That is, the flow rate of the pump 1 is controlled so as to always maintain the pump pressure Pd = the load pressure PL + ΔP. And the above mentioned pipeline
In the operating state near the neutral position of the spool 7, the opening 15a, 15b opens to the tank passage 13a, 13b, and the above-mentioned pipe 16a, 16b
b, a discharge passage connecting the transmission passage including the detection ports 17a and 17b and the conduit 18 to the tank passages 13a and 13b.

In the direction switching valve 5 configured as described above, the switching timing for the spool stroke of the flow control valve 8 such as the first variable throttle portions 14a and 14b and the conduits 15a and 15b is intended to drive the boom cylinder 4 independently. Assuming that the spool 7 is moved from the neutral position to the right in FIG. 5, the relationship between the stroke of the spool 7 and the opening area shown in FIG. 7 will be described. Note that the characteristic line 20a in FIG.
The characteristic line 20b shows the opening area between the passage 18 and the detection port 17b, that is, the tank passage 13b, and the characteristic line 20c shows the opening area between the pipe 15a and the load passage 12a. The characteristic line 20d indicates the aperture area, and the characteristic line 20d is the first variable diaphragm unit 14a.
Shows the opening area. When the spool 7 of the flow control valve 8 moves rightward from the state shown in FIG. 5, the characteristic line 20a in FIG.
As shown by, first, the path between the pipe 15a and the tank passage 13a is shut off. At this time, as shown by the characteristic line 20b, the pipeline 18
Is the tank passage 13b through the detection ports 17a, 17b and the conduit 15b.
Is in communication with Further, when the spool 7 moves to the right, the space between the pipe 18 and the detection port 17b is shut off, and the discharge passage which has been formed so as to connect the transmission passage including the pipe 18 and the tank passage 13b up to that time. The passage disappears. Further, when the spool 7 moves rightward, as shown by a characteristic line 20c, the pipe 15a opens into the load passage 12a, and the load pressure PL of the boom cylinder 4 shown in FIG. It is transmitted to one drive unit of the pump flow control device 2 via the detection port 17a, the pipeline 18, the chart valve 10, and the passage 19 shown in FIG. As a result, the discharge pressure Pd of the pump 1 becomes Pd = P
The pressure is increased to L + △ P. When the spool 7 further moves in the above-mentioned state, the first variable throttle portion 14a of the meter-in opens as shown by the characteristic line 20d in FIG. 7, and the hydraulic pump 1 shown in FIG. The pressure oil supplied through the pressure oil supply passage 11a shown in FIG.
The boom cylinder 4 is guided to the boom cylinder 4 via the first variable throttle portion 14a and the load passage 12a, and the boom cylinder 4 operates to drive a boom (not shown). At this time, the first
In the variable throttle section 14a, the differential pressure △ P with respect to the opening amount of the first variable throttle section 14a [No pressure compensation is performed because the pressure compensating valve 9 is a single drive of the boom cylinder 4; = {(Pz = Pd) -PL}], where C is a constant and A is the opening area of the first variable throttle portion 14a, the flow rate Q supplied to the boom cylinder 4 is Becomes The pressure compensating valve 9 does not function when the boom cylinder 4 is driven alone, but when the boom cylinder 4 and other actuators (not shown) are combined, the first variable throttle is used to realize a good combined drive of these actuators. If the pressure difference Pz−PL between the front and rear portions 14a and 14b is controlled to be constant and the value is △ P ′, Becomes

In the above configuration, when the pump flow rate is controlled in accordance with the spool stroke, it is ideal if the displacement of the pump 1 can be reduced to zero when the spool 7 is in the neutral position. In addition, it cannot be held below the predetermined displacement.

Therefore, in the above circuit configuration, when the spool 7 is in the neutral position, the pump 1 prevents the discharged flow from being thrown into the tank via the relief valve 3 to cause energy loss. In addition.

The set pressure of the unload valve 21 is a differential pressure by the spring 22.
Is set to P pressure slightly higher than the set pressure (e.g., pressure difference △ P is in the 25 Kg / cm ² to 15Kg / cm ^2). Thus, when the pump 1 is controlled by the set pressure of the differential pressure ΔP, the unload valve 21 is closed, and when the spool 7 is in the neutral position, the discharge flow of the pump 1 flows from the unload valve 21 to the tank. The discharge side pressure Pd of the pump 1 at that time is 25 kg / cm ² .

<Problem to be Solved by the Invention> In the above-described conventional technology, the maximum value of the flow rate Q supplied to the boom cylinder 4 is determined by the pressure difference caused by the flow rate passing through the direction switching valve 5 when the spool 7 is fully strolled. This is the flow rate when it becomes equal to the differential pressure ΔP that controls the flow rate of the pump 1. That is, the maximum permissible flow rate is determined by the pipeline pressure loss inside the direction switching valve 5 and the maximum opening area of the spool. Therefore, no matter how much the pump has a flow rate, the flow rate is determined by the size of the directional control valve. Here, if the differential pressure ΔP for controlling the pump discharge flow rate is increased, a larger flow rate can be flowed into the directional control valve, but the set pressure of the above-described unload valve must be increased accordingly. The energy loss when the lever is neutral is large.

An object of the present invention is to provide a differential pressure ΔP for controlling a pump discharge flow rate.
It is an object of the present invention to provide a directional control valve capable of increasing the maximum flow rate without changing the flow rate.

<Means for Solving the Problems> The object is to provide a directional control valve having a flow control valve for controlling a flow of a hydraulic pressure supplied from a pressure oil supply source to an actuator, which is connected to the pressure oil supply source. A meter-in having a pressure oil supply passage and a load passage connected to the actuator, wherein the flow control valve connects the pressure oil supply passage and the load passage and opens according to an operation amount of the flow control valve; A first variable throttle unit, a detection port for detecting a load pressure of the actuator, a transmission passage for transmitting the load pressure detected by the detection port as a control pressure of the pressure oil supply source, A directional control valve having a discharge passage communicating with a tank passage, a directional switching valve provided in parallel with the first variable throttle portion, and having a connection pipe connecting the pressure oil supply passage and the load passage; This is achieved by forming a directional control valve having at least two throttles connected in series in the connection pipe line, and communicating between the two throttles and a load pressure detection port. You.

<Operation> The opening area of the first variable throttle unit is A, the throttle amount of one of the at least two throttles connected in series with the second connection conduit is α, and the other is α. When the throttle amount of the throttle is β, the flow rate Q of the pressure oil supplied to the boom cylinder 4 is It is determined by the above equation.

That is, the flow rate Q of the pressure oil supplied to the actuator
Is determined by the ratio of α and β.

Therefore, by considering the ratio of α and β,
It is possible to flow a large amount of flow into the directional control valve without increasing the set pressure of the above-mentioned unload valve, so that the energy loss when the lever is neutral is small.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention, and FIG. 2 is a circuit of a hydraulic drive device in a civil engineering, construction machine or the like equipped with a load sensing system provided with the directional control valve shown in FIG. It is a circuit diagram showing a system.

 The same reference numerals as those in the conventional example indicate the same components.

The directional control valve 50 of this embodiment shown in FIG.
Similarly to the directional control valve 5 shown in FIG.
It has a pressure oil supply passage 11a, 11b connected to the pressure oil supply source shown in the drawing, ie, the pump 1, and a load passage 12a, 12b connected to the actuator shown in FIG. 2, ie, the boom cylinder 4, and has a flow control valve. 80 is the pressure oil supply passage 11
a, 11b and load passages 12a, 12b, and a meter-in first variable throttle section that opens according to the operation amount of the flow control valve 80.
14a and 14b, load pressure detection ports 57a and 57b for detecting the load pressure of the boom cylinder 4, tank passages 13a and 13b, and a pressure compensating valve 9.

The spool 70 of the flow control valve 80 has pipes 56a, 5
6b, and the pipes 21a, 21b are provided so as to communicate with these pipes 56a, 56b.
The apertures 14α and 14α ′ are provided in a and 21b.

The pipes 11a and 11b and the pipes 12a and 12b are connected to the pipes 21a and 21b.
1b and lines 55a and 55b connected to the lines 56a and 56b, and these lines 55a and 55b
β and 14β 'are provided.

That is, in this embodiment, the first variable aperture units 14a and 14b
Are provided in parallel with each other, a connecting line including the pipe 21a, the pipes 56a and 55a, and a connecting pipe including the pipes 21b, 56b, and 55b are provided.A pair of these connecting pipes is provided in each of the connecting pipes. Aperture
14α, 14β, and apertures 14α ′, 14β ′ are provided.
Also, the load pressure detection port described above between the throttles 14α and 14β
The load pressure detection port 57b is provided between the throttles 14α 'and 14β'.

In the directional control valve 50 configured as described above, the flow control valves such as the first variable throttle portions 14a and 14b and the conduits 55a and 55b are provided.
Assuming that the switching timing for the spool stroke of 80 is to move the spool 70 from the neutral state to the right in FIG. 1 in order to drive the actuator, for example, the boom cylinder 4, independently, the spool stroke shown in FIG. The relationship with the opening area will be described with reference to the drawings.

 A characteristic line 20e indicates an opening area between the passage 11a and the conduit 21a.

When the spool 70 of the flow control valve 80 moves rightward from the state shown in FIG. 1, the line between the pipe 55a and the tank passage 13a is first shut off as indicated by the characteristic line 20a in FIG. At this time, as shown by the characteristic line 20b, the pipeline 18 is connected to the load pressure detection port 5
7b communicates with the tank passage 13b via the conduits 56b and 55b. Further, when the spool 70 moves rightward, the discharge passage formed so as to communicate the transmission passage including the pipe 18 and the tank passage 13b disappears. When the spool 70 further moves to the right, the pipeline 55a opens to the load passage 12a as shown by the characteristic line 20c, and the boom cylinder 4 shown in FIG.
The load pressure PL of pipeline 55a, 56a, load pressure detection port 57
a, a pipe 18, a shuttle valve 10, and a pipe 19 shown in FIG.

 As a result, the discharge pressure Pd of the pump 1 increases to the pressure Pd = PL + △ P.

Then, when the spool 70 further moves from the above-mentioned state, as shown by a characteristic line 20d in FIG.
Of the hydraulic pump 1 shown in FIG.
The pressure oil supplied through the pressure compensation valve 9 from the pressure oil supply passage 11a, the first variable throttle portion 14a, and the load passage 12 shown in FIG.
It is led to the boom cylinder 4 via a. At this time, the pipeline 21a is also opened at the same time, and the pressure oil supply passage 11a and the pipeline 56a are communicated via the throttle 14α.

Therefore, the pressure oil in the passage 11a is supplied to the pipe 5 through the throttle 14α.
It is also guided to 6a, and further flows out into the load passage 12a via the restriction 14β in the conduit 55a. Therefore, the pressure in the conduit 56a is equal to the load pressure P
The pressure becomes higher than L by an amount corresponding to the pressure loss of the flow passing through the throttle 14β, and the pressure is transmitted to the pump flow controller 2.

Therefore, the flow rate Q supplied to the boom cylinder 4 can be determined using the schematic diagram of the direction switching valve 50 in FIG.

In FIG. 4, Q is the flow rate passing through the entire directional control valve 50, Q ₁ is the flow rate passing through the first variable throttle section 14a, Q ₂ is the flow rate passing through the throttles 14α and 14β, Pz is the upstream pressure in the first variable throttle section 14a and the throttle 14α, Pl ₁ is the downstream pressure in the first variable throttle section 14a and the throttle 14β, and Pl ₂ is the throttle 14
Pressure between α and 14β.

From the known general formula, Holds.

Here, from (4) and (5), Can be obtained.

And in (3) and (7), Thus, the flow rate Q supplied to the boom cylinder 4 can be obtained.

Therefore, in the present embodiment, the flow rate Q is set by appropriately setting the ratio α / β of the throttle amount of the throttles 14α and 14β or the ratio α ′ / β ′ of the throttle amount of the throttles 14α ′ and 14β ′.
Can be more.

In the present invention, the circuit of the boom cylinder 4 has been described as an example. However, it goes without saying that similar effects can be obtained by using other actuators without being limited to the boom cylinder 4.

<Effects of the Invention> According to the present invention, a connection conduit for connecting a passage and a load passage in parallel with the first variable throttle portion is provided,
The connecting line is provided with at least two throttles connected in series, and the load pressure detection port is communicated between the two throttles, so that a smaller direction switching can be performed within the same differential pressure ΔP. There is an effect that a large flow rate can be flowed even with a valve.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an embodiment of a directional switching valve according to the present invention. FIG. 2 is a hydraulic oil drive for a civil engineering or construction machine having a load sensing system provided with the directional switching valve according to the present invention. FIG. 3 is a circuit diagram showing the device, FIG. 3 is a diagram showing a relationship between a spool and an opening area in the directional switching valve of the present invention, FIG. 4 is a schematic diagram of a waist portion of the directional switching valve in the present invention, and FIG. FIG. 6 is a circuit diagram showing a conventional hydraulic drive device, and FIG. 7 is a diagram showing a relationship between a spool and an opening area in a conventional directional control valve. DESCRIPTION OF SYMBOLS 1 ... Variable displacement hydraulic pump 2 ... Pump flow control device 4 ... Boom cylinder (actuator) 6 ... Block body 9 ... Pressure compensation valve 10 ... Shuttle valve 11a, 11b ... Pressure oil supply passage 12a, 12b Load passages 13a, 13b Tank passages 14a, 14b First variable throttles 14α, 14α 'throttles 14β, 14β' throttles 55a, 55b Pipes 56a, 56b Pipes 57a, 57b Load pressure detection port 18, 19 Pipe line 21 Unload valve 21a, 21b Pipe line 50 Directional switching valve 70 Spool 80 Flow control valve

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Genroku Sugiyama 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (56) References 54-94122 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F15B 11/00-11/22

Claims (1)

(57) [Claims] 1. A directional control valve having a flow control valve for controlling a flow of hydraulic pressure supplied from a pressure oil supply source to an actuator, comprising: a pressure oil supply passage connected to the pressure oil supply source; And a load passage communicated with
A first variable throttle section of a meter-in, wherein the flow control valve connects the pressure oil supply passage and the load passage and opens according to an operation amount of the flow control valve; a detection port for detecting a load pressure of the actuator A directional switching valve having a transmission passage for transmitting the load pressure detected by the detection port as the control pressure of the pressure oil supply source, and a discharge passage communicating the transmission passage with the tank passage. And a connection pipe connecting the pressure oil supply passage and the load passage, the connection pipe having at least two throttles connected in series. A directional switching valve characterized in that communication between a throttle and a load pressure detection port is provided.