JP5513996B2 - Load sensing control device - Google Patents

Description

  The present invention relates to a load sensing control device that detects a load pressure of an actuator and controls a discharge amount of a variable displacement pump.

  A device of this type shown in FIGS. 6 and 7 is conventionally known. In this conventional apparatus, actuators 3 and 3 are connected in parallel to a variable displacement pump P whose tilt angle is controlled by a regulator 1 via flow paths 2 and 2, and the flow paths 2 and 2 are connected to each other. Each is provided with a spool valve V, and further, a pressure compensation valve CV is provided downstream of the spool valve V.

The regulator 1 is supplied with the discharge pressure of the pump P via the discharge pressure pilot flow path 4 and the load pressure of the actuators 3 and 3 via the load pressure pilot flow path 5. ing. Reference numeral 6 denotes a high pressure selection valve. The maximum load pressure is selected by the high pressure selection valve 6, and the selected high load pressure is guided to the regulator 1 via the load pressure pilot flow path 5.
Thus, the regulator 1 from which the pump discharge pressure and the load pressure are derived controls the discharge amount of the pump P so as to keep the discharge pressure higher by the differential pressure set with respect to the maximum load pressure.

The specific configuration of the spool valve V is as shown in FIG. That is, in the valve body 7 of the spool valve V, pump ports 8 a and 8 b connected to the pump P are formed, and actuator ports 9 and 10 connected to the actuator 3 are formed.
A spool 11 is slidably incorporated in the valve body 7, and when the spool 11 is in the neutral position shown in the figure, the pump ports 8a and 8b and an upstream supply passage 12a formed in the valve body 7 are provided. Communication is blocked. The upstream supply flow path 12a thus configured is configured to communicate with the downstream supply flow path 12b via the pressure compensation valve CV incorporated in the valve body 7.

  Then, when the spool 11 moves from the neutral position shown in the figure, for example, in the right direction in the drawing, one notch 13a formed in the spool 11 opens into the annular recess 14 communicating with the upstream supply channel 12a. Accordingly, the pressure oil supplied to the pump port 8a is guided to the upstream supply flow path 12a and is also guided to the downstream supply flow path 12b having a bridge shape by pushing the pressure compensation valve CV open.

  If the spool 11 moves to the right as described above, the downstream supply flow path 12b and the one actuator port 9 communicate with each other through the one annular groove 15. Therefore, the pressure oil guided to the downstream supply channel 12 b is supplied to the actuator 3 via the one actuator port 9. At this time, since the other annular groove 16 formed in the spool 11 opens into the tank passage 17, the return oil of the other actuator port 10 is returned to a tank (not shown).

  When the spool 11 moves to the opposite side, the other notch 13b opens to the annular recess 14 and the downstream supply passage 12b and the other actuator port 10 communicate with each other via the annular groove 16. The one actuator port 9 and the tank passage 17 communicate with each other through the annular groove 15. Therefore, the pressure oil supplied to the pump port 8b is supplied from the other actuator port 10 to the actuator 3 via the upstream supply channel 12a. The return oil from the actuator 3 is returned to the tank from one actuator port 9 through the tank passage 17.

Further, the pressure compensation valve CV is provided with a spring 19 in a pilot chamber 18 formed on the side opposite to the upstream supply flow path 12a, and the pilot chamber 18 has a higher load pressure of the actuator 3. Is to be guided. Further, the valve body 20 of the pressure compensation valve CV is formed with a control throttle 21 for communicating the upstream supply channel 12a and the downstream supply channel 12b. The pressure compensation valve C controls the opening degree of the control throttle 21 so that the pressure in the upstream supply passage 12a becomes the maximum load pressure + the spring force of the spring 19. As a result, the differential pressure across the notch 13a becomes equal to the differential pressure set by the regulator 1 minus the spring force of the spring 19.
Reference numeral 22 in the figure denotes a centering spring, and the spool 11 normally maintains the neutral position shown in the figure by the action of the spring force of the spring 22.

  In the apparatus as described above, when the spool 11 is fully stroked, the communication between the annular grooves 23 and 24 formed in the spool 11 and the annular recess 14 is controlled by the notches 13a or 13b. Therefore, the maximum speed of the actuator 3 is controlled by the notch 13a or 13b.

Japanese Patent No. 3776047

  In the above-described conventional apparatus, when the spool 11 is fully stroked, the speed of the actuator becomes maximum. However, if the stroke of the spool 11 varies, the maximum speed of the actuator also varies. Sometimes made the operator feel uncomfortable.

Further, for example, in a construction machine that drives by driving a pair of hydraulic motors, when the pair of hydraulic motors is operated at the maximum speed and travels straight, the maximum speeds of both the hydraulic motors vary. If so, there also arises a problem that it is impossible to travel straight ahead.
This occurs as a result of accumulation of various dimensional tolerances such as tolerances of the formation positions of the notches 13a and 13b of the spool 11 and dimensional tolerances of caps and spring seats that determine the stroke amount.

  An object of the present invention is to provide a load sensing control device in which the maximum operating speed of an actuator is constant even if the full stroke of the spool varies.

  The present invention relates to a variable displacement pump, a regulator for controlling the tilt angle of the pump, an actuator connected to the pump, a spool valve provided between the pump and the actuator, and a discharge pressure of the pump. The present invention relates to a load sensing control device provided with a discharge pressure pilot flow path for guiding the pressure to the regulator and a load pressure pilot flow path for guiding the load pressure of the actuator to the regulator.

In the first invention, a fixed orifice is provided between a connection point connecting the discharge pressure pilot flow path and the pump and a connection point connecting the load pressure pilot flow path and the actuator, and the spool is full. It is characterized in that the maximum flow rate is determined by the opening of the fixed orifice during the stroke .
The second invention is characterized in that a pressure compensation valve is provided downstream of the spool valve, and the fixed orifice is provided upstream of the pressure compensation valve.
The third invention is characterized in that a pressure compensation valve is provided upstream of the spool valve, and the fixed orifice is provided downstream of the pressure compensation valve.

  According to a fourth aspect of the present invention, a pump port and an actuator port are formed in the spool body of the spool valve, and a spool is slidably incorporated in the valve body. The actuator port communicates with a supply channel formed in the valve body, while the fixed orifice is provided in the supply channel.

The fifth invention is characterized in that a throttle member constituting a fixed orifice is assembled in the supply flow path of the valve body.
The sixth invention is characterized in that a pressure compensation valve is incorporated in the supply flow path of the valve body, and the fixed orifice is formed in the valve body of the pressure compensation valve.

  According to the first to third aspects of the invention, even when the spool is fully stroked, the supply flow rate to the actuator at that time is determined by the opening of the fixed orifice. Therefore, the supply flow rate during the full stroke of the spool is stable and does not vary as in the conventional case.

According to the fourth invention, since the fixed orifice is provided in the supply flow path formed in the valve body of the spool valve, it is not necessary to secure a special space for providing the fixed orifice, and the apparatus is reduced in size accordingly. Can be
According to the fifth aspect of the invention, since the throttle member in which the fixed orifice is formed is incorporated in the supply flow path, the fixed orifice can be easily provided.
According to the sixth aspect, since the fixed orifice is formed in the valve body of the pressure compensation valve, the fixed orifice can be provided by incorporating the pressure compensation valve into the valve body of the spool valve.

It is a circuit diagram of a 1st embodiment. It is sectional drawing of the spool valve of 1st Embodiment. (A) is a graph showing spool stroke and opening characteristics of the notch, (b) is a graph showing spool stroke and opening characteristics of the fixed orifice, and (c) is a graph showing combined opening characteristics of the notch and fixed orifice. . It is sectional drawing of the spool valve of 2nd Embodiment. It is a circuit diagram of a 3rd embodiment. It is a circuit diagram of the conventional load sensing control apparatus. It is sectional drawing of the spool valve in the conventional load sensing control apparatus.

  The first embodiment shown in FIGS. 1 and 2 differs from the prior art in that a fixed orifice 25 is provided between the spool valve V and the pressure compensation valve CV, and the other configurations are the same as in the prior art. Accordingly, the same reference numerals are used for the same constituent elements as those in the prior art, and the description of the conventional apparatus is used as it is in the detailed description.

In the first embodiment, the fixed orifice 25 is provided between the spool valve V and the pressure compensation valve CV. However, as shown in FIG. 2, the fixed orifice 25 is provided in the upstream supply channel 12 a of the spool valve V. The diaphragm member 26 having the shape is incorporated.
In the first embodiment thus configured, the fixed orifice 25 can be configured simply by incorporating the throttle member 26 into the upstream supply flow path 12a as described above.

  By configuring as described above, the composite opening characteristics of the notches 13a and 13b and the fixed orifice 25 with respect to the stroke of the spool 11 are as shown in FIG. That is, the opening degree of the notches 13a and 13b gradually increases according to the stroke of the spool 11, but when the notch exceeds the boundary between the pump port 8a and the annular recess 14, the pump ports 8a and 8b are annular. Opening into the recess 14, the notches 13 a and 13 b lose their control function, and the pump ports 8 a and 8 b are kept fully open with respect to the upstream supply flow path 12 a.

That is, as shown in FIG. 3A, when the stroke of the spool 11 exceeds the dotted line portion, the notches 13a and 13b lose their control function as described above, and the pump port 8a for the upstream supply flow path 12a is lost. , 8b suddenly increases in opening area.
However, in the first embodiment, since the fixed orifice 25 is provided as described above, the maximum flow rate is kept constant by the fixed orifice 25 regardless of the stroke of the spool 11.

Therefore, when the opening characteristic shown in FIG. 3A by the notches 13a and 13b and the opening characteristic shown in FIG. 3B by the fixed orifice 25 are synthesized, the opening characteristic shown in FIG. 3C is obtained. be able to.
In the synthetic aperture characteristics obtained in this way, the maximum flow rate becomes constant if the spool 11 strokes more than a certain amount. For example, the maximum flow rate does not become unstable due to variations in the stroke of the spool 11.

The second embodiment shown in FIG. 4 is different from the first embodiment in that the fixed orifice 27 is formed in the pressure compensation valve CV, and all other configurations are the same as those of the first embodiment.
Therefore, in the description of the second embodiment, the same reference numerals as those in the first embodiment are used, and the detailed description of the overlapping portions is omitted.

The pressure compensation valve CV has a cylindrical shape on the upstream side of the control throttle 21 formed in the valve body 20 and a fixed orifice 27 inside the cylindrical portion.
Accordingly, the opening degree of the notches 13a and 13b gradually increases according to the stroke of the spool 11, but when the notch exceeds the boundary between the pump port 8a and the annular recess 14, the pump ports 8a and 8b are annular. Opening into the recess 14, the notches 13 a and 13 b lose their control function, and the pump ports 8 a and 8 b are kept fully open with respect to the upstream supply flow path 12 a.

That is, as shown in FIG. 3A, when the stroke of the spool 11 exceeds the dotted line portion, the notches 13a and 13b lose their control function as described above, and the pump port 8a for the upstream supply flow path 12a is lost. , 8b suddenly increases in opening area.
However, since the fixed orifice 27 is provided in the second embodiment, the maximum flow rate is kept constant by the fixed orifice 27 regardless of the stroke of the spool 11 as in the first embodiment.

Therefore, when the opening characteristic shown in FIG. 3A by the notches 13a and 13b and the opening characteristic shown in FIG. 3B by the fixed orifice 27 are synthesized, the opening characteristic shown in FIG. 3C is obtained. be able to.
In the synthetic opening characteristic obtained in this way, the maximum flow rate becomes constant if the spool 11 strokes more than a certain amount. For example, the maximum flow rate does not become unstable due to variations in the stroke of the spool 11.

In the third embodiment shown in FIG. 5, the spool valve V and the fixed orifice 28 are provided on the downstream side of the pressure compensation valve CV. The spool valve V and the fixed orifice 28 are the spool valve V of the first and second embodiments. In addition, the same configuration as that of the fixed orifices 25 and 27 can be adopted.
In the third embodiment, as in the first and second embodiments, the maximum flow rate is kept constant by the fixed orifice 28 regardless of the stroke of the spool 11.

Therefore, when the opening characteristic shown in FIG. 3A by the notches 13a and 13b and the opening characteristic shown in FIG. 3B by the fixed orifice 28 are combined, the opening characteristic shown in FIG. 3C is obtained. be able to.
In the synthetic opening characteristic obtained in this way, the maximum flow rate becomes constant if the spool 11 strokes more than a certain amount. For example, the maximum flow rate does not become unstable due to variations in the stroke of the spool 11.

  Ideal for construction machines such as power shovels that perform load sensing control.

P pump 1 regulator 3 actuator CV pressure compensation valve 4 discharge pressure pilot flow path 5 load pressure pilot flow path V spool valve 7 valve body 11 spool 12a upstream supply flow path 12b downstream supply flow path 25 fixed orifice 27 fixed orifice 28 fixed Orifice

Claims (6)

A variable displacement pump, a regulator for controlling the tilt angle of the pump, an actuator connected to the pump, a spool valve provided between the pump and the actuator, and a discharge pressure of the pump to the regulator A load sensing control device comprising a discharge pressure pilot flow path for guiding and a load pressure pilot flow path for guiding the load pressure of the actuator to the regulator, a connection point for connecting the discharge pressure pilot flow path and the pump, and a load A load sensing control device in which a fixed orifice is provided between a pressure pilot flow path and a connection point connecting an actuator, and the maximum flow rate is determined by the opening of the fixed orifice during a full stroke of the spool .   2. The load sensing control device according to claim 1, wherein a pressure compensation valve is provided downstream of the spool valve, and the fixed orifice is provided upstream of the pressure compensation valve.     The load sensing control device according to claim 1, wherein a pressure compensation valve is provided upstream of the spool valve, and the fixed orifice is provided downstream of the pressure compensation valve.   The spool valve has a pump port and an actuator port formed in the valve body, and a spool is slidably incorporated in the valve body, and the pump port and the actuator port are arranged according to the moving position of the spool. The load sensing control device according to any one of claims 1 to 3, wherein the fixed orifice is provided in the supply flow channel while the communication is made through a supply flow channel formed on the supply channel.   The load sensing control device according to claim 4, wherein a throttle member constituting a fixed orifice is assembled in the supply flow path of the valve body.   5. The load sensing control device according to claim 4, wherein a pressure compensation valve is incorporated in the supply passage of the valve body, and the fixed orifice is formed in the valve body of the pressure compensation valve.

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