JP6381228B2 - Hydraulic drive - Google Patents

Description

  Embodiments described herein relate generally to a hydraulic drive device.

  A hydraulic drive device for driving a hydraulic actuator of a construction machine includes an operation unit (pilot valve), a variable displacement hydraulic pump (hereinafter simply referred to as a hydraulic pump), a hydraulic control valve, and a pump control (control unit). It is equipped with. The operation unit (pilot valve) is for operating each hydraulic actuator. The hydraulic pump supplies pressure oil to each hydraulic actuator. The hydraulic control valve controls the flow rate of the pressure oil supplied to each hydraulic actuator based on the operation signal. The pump control performs drive control of the hydraulic pump based on the operation signal.

  Here, many of the hydraulic control valves used in the construction machines as described above have a plurality of open center type switching valves. These open center type switching valves are connected to the hydraulic pump through a tandem passage and a parallel passage branched from the tandem passage. As the hydraulic pump, a hydraulic pump having negative control discharge flow rate control means (hereinafter referred to as a negative control type hydraulic pump) in which the discharge flow rate decreases as the signal pressure from the hydraulic control valve increases is often adopted. .

  By the way, there are various uses for construction machinery. For example, construction machines are used for many purposes, such as excavation work, work of loading earth and sand on trucks, destruction work of buildings and roads, work of crushing rubble, and work of grabbing and moving rubble. For this reason, various hydraulic actuators are attached to the construction machine, such as for excavation called a bucket, for destruction called a breaker, for crushing called scissors, and for gripping called a grapple. Further, there are many cases where a plurality of these hydraulic actuators are used in combination, and the number of switching valves of the hydraulic control valve is changed according to the application.

  In addition, each hydraulic actuator is set with an appropriate flow rate and pressure of pressure oil. In the negative control type hydraulic pump, since the flow rate of the pressure oil depends on the maximum discharge amount of the hydraulic pump, it is difficult to supply the hydraulic oil with an appropriate flow rate to each hydraulic actuator.

  On the other hand, there is a pressure oil flow rate control method called a load sensing method. The load sensing method detects the maximum load pressure among the load pressures applied to the cylinder port of each switching valve and controls the flow control valve with pressure compensation function to apply pressure oil to the high pressure system (switching valve). It is a system that performs optimum diversion control by turning and also performs flow rate control of the hydraulic pump. In other words, the load sensing method is a method for controlling the flow rate of the pressure oil based on the opening area of the spool of the switching valve. For this reason, it is easy to supply pressure oil at an appropriate flow rate to each hydraulic actuator. However, in the case of the load sensing method, operability such as hunting and shock may be deteriorated during the operation of the construction machine.

Japanese Patent No. 2981311

  The problem to be solved by the present invention is that each hydraulic actuator can be easily increased or decreased, the flow rate of pressure oil to each hydraulic actuator can be easily controlled, and the operability of a construction machine or the like can be improved. It is to provide a hydraulic drive device that can be improved.

  The hydraulic drive apparatus according to the embodiment includes a variable displacement pump, a tank, a first hydraulic control valve, a second hydraulic control valve group, an orifice for detecting a negative control pressure, a flow control valve with a pressure compensation function, and a bypass. With a passage. The variable displacement pump has negative control discharge flow rate control means and supplies pressure oil to the hydraulic actuator. The pressure oil discharged from the variable capacity pump is returned to the tank. The first hydraulic control valve is disposed between the variable displacement pump and the tank, and is connected to the variable displacement pump and the tank via a tandem passage and a parallel passage branched from the tandem passage, respectively. Has a valve. The second hydraulic control valve group is disposed between the parallel passage of the first hydraulic control valve and the tank, and has at least one second hydraulic control valve provided with a closed center type switching valve. The negative control pressure detecting orifice is disposed between the first hydraulic control valve and the tank and on the tandem passage. The flow rate control valve with a pressure compensation function is disposed between an open center type switching valve arranged on the most downstream side among the plurality of open center type switching valves and an orifice, and is connected to a tandem passage. The bypass passage connects the downstream side of the flow rate control valve with a pressure compensation function and the upstream side of the second hydraulic control valve group via a check valve.

The schematic block diagram which shows the hydraulic drive device of embodiment.

  Hereinafter, a hydraulic drive device of an embodiment is explained with reference to drawings.

FIG. 1 is a schematic configuration diagram of a hydraulic drive device.
As shown in the figure, the hydraulic drive device 1 is mounted on, for example, a hydraulic excavator and includes a plurality of hydraulic actuators 2. Further, a hydraulic pump (variable displacement hydraulic pump) 4 for supplying desired hydraulic oil to each hydraulic actuator 2 is provided. Furthermore, a first hydraulic control valve 5 and a second hydraulic control valve group 6 that are provided between the hydraulic actuator 2 and the hydraulic pump 4 and control the flow rate of the pressure oil supplied to the hydraulic actuator 2 are provided.

  In addition, the hydraulic drive device 1 includes an operation unit, a pump control unit (both not shown), and the like. The operation unit outputs an operation signal of each hydraulic actuator 2, and this output signal is input to the first hydraulic control valve 5, the second hydraulic control valve group 6, and the pump control unit. The first hydraulic control valve 5 and the second hydraulic control valve group 6 are inputted with operation signals to an open center type switching valve (spool) 7 and a closed center type switching valve (spool) 19 which will be described later, and based on these operation signals. Each switching valve 7, 19 is driven. The pump control unit performs drive control of the hydraulic pump 4 based on the operation signal.

As the hydraulic pump 4, a negative control type hydraulic pump is employed. Each hydraulic pump 4 is driven by a motor (not shown).
In the present embodiment, the hydraulic drive device 1 includes two hydraulic pumps 4 (4a, 4b), and the first hydraulic control valves 5 (5a, 5b) are connected to the hydraulic pumps 4, respectively. However, the number of hydraulic pumps 4 and first hydraulic control valves 5 is not limited to two, and may be one each, or a plurality of three or more.

  Here, the configurations of the hydraulic pumps 4a and 4b and the first hydraulic control valves 5a and 5b are substantially the same. Therefore, in the following description, only one hydraulic pump 4a and the first hydraulic control valve 5a will be described, and the other hydraulic pump 4b and the second hydraulic control valve 5b will be described by one hydraulic pump 4a and the first hydraulic pressure. The same reference numerals as those of the control valve 5a are attached and description thereof is omitted.

  Examples of the hydraulic actuator 2 include a hydraulic cylinder for driving an arm, a hydraulic motor for rotating a cab (swivel body), a hydraulic cylinder for driving a bucket, a hydraulic cylinder for driving a boom, and a hydraulic motor for driving. . These hydraulic actuators 2 can be arbitrarily connected to the first hydraulic control valve 5 (5a, 5b) and the second hydraulic control valve group 6, respectively.

  The first hydraulic control valve 5 a has a plurality of open center type switching valves (spools) 7 for adjusting the flow rate of the pressure oil to each hydraulic actuator 2. Each open center type switching valve 7 is connected via a tandem passage 8 which is a high-pressure pipe through which pressure oil flows, and a parallel passage 9 branched from the tandem passage 8. The tandem passage 8 is connected to a pump passage 10 through which pressure oil discharged from the hydraulic pump 4a flows on the upstream side. On the other hand, the tank passage 11 is connected to the downstream side. The tank passage 11 communicates with a tank (not shown), and the pressure oil discharged from the hydraulic pump 4 a is finally returned to the tank via the tank passage 11.

  The open center type switching valve 7 is configured such that the oil passage (tandem passage 8) from the hydraulic pump 4a to the tank passage 11 is opened when in the neutral position. Each open center type switching valve 7 is connected to a cylinder port 14 provided in the first hydraulic control valve 5a. Various hydraulic actuators 2 are connected to the cylinder port 14, and a flow rate of pressure oil corresponding to the opening degree of the open center type switching valve 7 is supplied to the hydraulic actuator 2.

In addition, check valves 12 are provided in the parallel passage 9 so as to correspond to the open center type switching valves 7 so that the pressure oil supplied to the open center type switching valves 7 does not flow backward. An orifice 13 is provided on the most downstream side of the parallel passage 9.
On the other hand, a load sensing switching valve 15 is provided downstream of the tandem passage 8, and a negative control orifice 16 is further provided downstream of the load sensing switching valve 15. The load sensing switching valve 15 is configured to be able to block the tandem passage 8. The negative control orifice 16 is for detecting the hydraulic pressure on the tandem passage 8 (negative control hydraulic pressure). The pressure of the negative control orifice 16 is output to the hydraulic pump 4 a via the signal line 17.

A second hydraulic control valve group 6 is provided on the downstream side of the first hydraulic control valve 5 a configured in this way, in other words, between the first hydraulic control valve 5 a and the tank passage 11.
In FIG. 1, the second hydraulic control valve group 6 is provided only on the downstream side of one of the two first hydraulic control valves 5a and 5b. The second hydraulic control valve group 6 is also provided on the downstream side of the first hydraulic control valve 5b. Since these second hydraulic control valve groups 6 have substantially the same structure, the second hydraulic control valve group 6 provided on the downstream side of the other first hydraulic control valve 5b is not shown in FIG.

  The second hydraulic control valve group 6 includes a plurality (two in the present embodiment) of second hydraulic control valves 6a. Each of the second hydraulic control valves 6a has a second pump passage 18, and the second pump passages 18 are connected so as to communicate with each other. Of the second hydraulic control valves 6a, the second pump passage 18 of the second hydraulic control valve 6a on the first hydraulic control valve 5a side is connected to the downstream end of the parallel passage 9 in the first hydraulic control valve 5a. Is done.

  Each second hydraulic control valve 6 a has a closed center type switching valve (spool) 19. When a plurality of second hydraulic control valves 6 a are connected, a plurality of closed center type switching valves 19 are connected in parallel via the second pump passage 18. Further, each closed center type switching valve 19 is connected to the tank passage 11 on the downstream side. When the closed center type switching valve 19 is in the neutral position, the oil passage continuing from the hydraulic pump 4a to the tank passage 11 via the second pump passage 18 is closed.

  Further, each closed center type switching valve 19 is connected to a cylinder port 20 provided in each second hydraulic control valve 6a. Various hydraulic actuators 2 are connected to the cylinder port 20, and pressure oil having a flow rate corresponding to the opening degree of the closed center type switching valve 19 is supplied to the hydraulic actuator 2.

  The second hydraulic control valve group 6 of the present embodiment is illustrated in FIG. 1 when two second hydraulic control valves 6a are connected. However, the second hydraulic control valve group 6 is not limited to this. The control valve group 6 only needs to be composed of at least one second hydraulic control valve 6a. Further, three or more second hydraulic control valves 6a may be connected according to the number of hydraulic actuators 2 used. When three or more second hydraulic control valves 6a are connected, the closed center type switching valves 19 are connected in parallel via the second pump passages 18 of the second hydraulic control valves 6a.

  Here, in the tandem passage 8 of the first hydraulic control valve 5a, a first bypass passage 21 branched from the tandem passage 8 is provided between the load sensing switching valve 15 and the negative control orifice 16. The first bypass passage 21 is connected to a second bypass passage 22 provided in the second hydraulic control valve group 6. The downstream side of the second bypass passage 22 is connected to the second pump passage 18.

In addition, the tandem passage 8 of the first hydraulic control valve 5 a is connected to the tandem passage 8 between the most downstream open center switching valve 7 and the load sensing switching valve 15 among the plurality of open center switching valves 7. A branched third bypass passage 23 is provided. The downstream side of the third bypass passage 23 is also connected to the second bypass passage 22, and the third bypass passage 23 and the second pump passage 18 are connected via the second bypass passage 22.
The second bypass passage 22 is provided with a flow rate control valve 24 with a pressure compensation function between the first bypass passage 21 and the third bypass passage 23, and the third bypass passage 23 and the second pump passage 18 are connected to each other. A check valve 25 is provided therebetween.

  In the flow rate control valve 24 with a pressure compensation function, the load sensing pressure from each closed center type switching valve 19 is passed through the maximum load sensing pressure line 26 in a spring chamber (not shown) provided at one end of the spool. Introduced. Each second hydraulic control valve 6 a is provided with a check valve 27 in the middle of the maximum load sensing pressure line 26, and the pressure oil flowing through the maximum load sensing pressure line 26 does not flow back to the closed center type switching valve 19. It is like that.

Further, the flow rate control valve 24 with a pressure compensation function includes a second pump passage 18 (the second pump passage 18 side of the second bypass passage 22 with respect to the flow rate control valve 24 with a pressure compensation function, at the other end of the spool, hereinafter referred to as a spring. The pressure on the side opposite the chamber is applied.
Here, the spool of the flow rate control valve with pressure compensation function 24 is the sum of the pressure in the spring chamber, that is, the spring force of the spring provided in the spring chamber and the pressure (hydraulic pressure) of the pressure oil introduced into the spring chamber. However, it is configured to be closed when the pressure is higher than the pressure on the opposite side of the spring chamber.

Next, the operation of the hydraulic drive device 1 will be described.
First, the case where the hydraulic actuator 2 connected to the first hydraulic control valve 5a is operated will be described.
In this case, the load sensing switching valve 15 of the first hydraulic control valve 5a is opened. The pressure oil discharged by the driving of the first hydraulic pump 4a is the pump passage 10, the tandem passage 8, the third bypass passage 23, the flow rate control valve 24 with pressure compensation function (second bypass passage 22), negative The gas is passed through the control orifice 16 in this order and returned to the tank passage 11.

Here, since the second hydraulic control valve group 6 is not operated, the hydraulic pressure of the maximum load pressure sensing line 26 is equal to the hydraulic pressure of the tank passage (tank) 11. The oil pressure in the tank passage 11 is lower than the oil pressure in the third bypass passage 23 (second bypass passage 22). For this reason, the spool of the flow rate control valve 24 with the pressure compensation function is opened.
On the other hand, since the negative control orifice 16 is provided on the downstream side of the tandem passage 8, the hydraulic pressure immediately before the negative control orifice 16 is increased by the throttle resistance. For this reason, the discharge amount of the pressure oil of the hydraulic pump 4a becomes the minimum discharge amount.

  If an attempt is made to drive the hydraulic actuator 2 connected to the first hydraulic control valve 5a from such a state, the open center type switching valve 7 moves from the neutral position, and the tandem passage 8 is moved by the open center type switching valve 7. Is interrupted on the way. For this reason, the pressure oil flows through the parallel passage 9 and returns to the tank passage 11. At this time, since the pressure oil is hardly passed through the negative control orifice 16, the hydraulic pressure immediately before the negative control orifice 16 becomes low. Therefore, the discharge amount of the hydraulic oil from the hydraulic pump 4a is the maximum discharge amount.

Next, the case where the hydraulic actuator 2 connected to the second hydraulic control valve group 6 is operated will be described.
In this case, the load sensing switching valve 15 of the first hydraulic control valve 5a is closed. When the load sensing switching valve 15 is closed, the tandem passage 8 is blocked. For this reason, the pressure oil discharged by driving the first hydraulic pump 4 a flows through the pump passage 10 and the parallel passage 9 and is returned to the tank passage 11. At this time, since the pressure oil is hardly passed through the negative control orifice 16, the hydraulic pressure immediately before the negative control orifice 16 becomes low. Therefore, the discharge amount of the hydraulic oil from the hydraulic pump 4a is the maximum discharge amount.

If an attempt is made to drive the hydraulic actuator 2 connected to the second hydraulic control valve group 6 from such a state, the closed center type switching valve 19 moves from the neutral position, and the hydraulic pressure of the maximum load pressure sensing line 26 is It becomes higher according to the load of the hydraulic actuator 2. Then, the pressure (load sensing pressure) of the maximum load pressure sensing line 26 is introduced into the spring chamber of the flow rate control valve 24 with a pressure compensation function, and the spool moves to the closing side.
As a result, the pressure in the second pump passage 18 increases until it becomes equal to the sum of the spring force of the spring of the flow rate control valve 24 with the pressure compensation function and the hydraulic pressure introduced into the spring chamber. The closed center type switching valve 19 is supplied with hydraulic pressure corresponding to the spring force of the spring in the flow rate control valve 24 with a pressure compensation function and pressure oil having a flow rate corresponding to the opening area of the closed center type switching valve 19.

Next, a case where the hydraulic actuator 2 connected to the first hydraulic control valve 5a and the hydraulic actuator 2 connected to the second hydraulic control valve group 6 are operated simultaneously will be described.
In this case, the load sensing switching valve 15 of the first hydraulic control valve 5a is closed. For this reason, the pressure oil discharged by driving the first hydraulic pump 4 a flows through the pump passage 10 and the parallel passage 9 and is returned to the tank passage 11.

The pressure oil flowing through the parallel passage 9 is supplied to the hydraulic actuator 2 via the open center type switching valve 7 of the first hydraulic control valve 5a, and also via the second pump passage 18 and the closed center type switching valve 19. Is supplied to the hydraulic actuator 2.
When the hydraulic actuator 2 connected to the first hydraulic control valve 5a and the hydraulic actuator 2 connected to the second hydraulic control valve group 6 are operated simultaneously, the load applied to each switching valve 7 and 19 is increased. Since they are different, it is possible to adjust the composite operability by appropriately providing an orifice in each of the passages 9 and 10.

  As described above, the hydraulic drive device 1 described above includes the first hydraulic control valve 5 of the negative control system configured by the open center type switching valve 7 and the second hydraulic control valve 6 a (the first hydraulic control valve 6 having the closed center type switching valve 19. 2 hydraulic control valve group 6). The second pump passages 18 of the second hydraulic control valves 6a are connected to the downstream end of the parallel passage 9 in the first hydraulic control valve 5a. Further, a flow rate control valve 24 with a pressure compensation function is provided on a second bypass passage 22 that connects the negative control orifice 16 and the open center type switching valve 7 disposed on the most downstream side and the second pump passage 18. Is provided. Therefore, when the first hydraulic control valve 5 is operated, the flow rate of the pressure oil can be controlled by the negative control method, and when the second hydraulic control valve group 6 is operated, the flow rate of the pressure oil can be controlled by the load sensing method.

  That is, the number of second hydraulic control valves 6a in the second hydraulic control valve group 6 can be easily increased or decreased. Furthermore, the second hydraulic control valve 6a having the closed center type switching valve 19 is adopted as a control valve that increases or decreases in accordance with the number of hydraulic actuators 2, and the flow rate of pressure oil is controlled by a load sensing method. For this reason, the hydraulic actuator 2 can be easily increased or decreased according to the specifications of the hydraulic drive device 1. Moreover, the flow rate control of the pressure oil to each hydraulic actuator 2 can be easily performed. Furthermore, the operability of a hydraulic excavator (construction machine) can be improved.

  Further, by providing the load sensing switching valve 15 in the tandem passage 8 of the first hydraulic control valve 5, it is possible to improve the operability when only the first hydraulic control valve 5 is operated. That is, when only the first hydraulic control valve 5 is operated, by opening the load sensing switching valve 15 of the first hydraulic control valve 5a, each open center type switching valve 7 of the first hydraulic control valve 5 is more Pressure oil with an appropriate flow rate can be supplied.

  In the above-described embodiment, the case where the load sensing switching valve 15 is provided in the tandem passage 8 of the first hydraulic control valve 5 has been described. However, the present invention is not limited to this, and the load sensing switching valve 15 is not provided. Also good. Even in such a configuration, when only the first hydraulic control valve 5 is operated, the flow rate of the pressure oil is reduced by the negative control orifice 16, so that the discharge flow rate of the hydraulic pump 4 is controlled almost appropriately. Is possible.

  According to at least one embodiment described above, when the first hydraulic control valve 5 is operated, the flow rate of the pressure oil can be controlled by the negative control method, and when the second hydraulic control valve group 6 is operated, the load sensing method is used. The flow rate of pressure oil can be controlled. For this reason, increase / decrease of each hydraulic actuator 2 can be performed easily. Moreover, the flow rate control of the pressure oil to each hydraulic actuator 2 can be easily performed. Furthermore, the operability of a hydraulic excavator (construction machine) can be improved.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Hydraulic drive device, 2 ... Hydraulic actuator, 4, 4a, 4b ... Hydraulic pump, 5, 5a, 5b ... 1st hydraulic control valve, 6 ... 2nd hydraulic control valve group, 6a ... 2nd hydraulic control valve, 7 DESCRIPTION OF SYMBOLS ... Open center type switching valve, 8 ... Tandem passage, 9 ... Parallel passage, 11 ... Tank passage (tank), 15 ... Load sensing switching valve, 16 ... Negative control orifice (orifice), 19 ... Closed center type switching valve, 21 ... 1st bypass passage (bypass passage), 22 ... 2nd bypass passage (bypass passage), 23 ... 3rd bypass passage (bypass passage), 24 ... Flow control valve with pressure compensation function, 25 ... Check valve

Claims (2)

A variable displacement pump having negative control discharge flow rate control means for supplying pressure oil to the hydraulic actuator;
A tank to which the pressure oil discharged from the variable displacement pump is returned;
A plurality of open center type switching valves disposed between the variable displacement pump and the tank and connected to the variable displacement pump and the tank via a tandem passage and a parallel passage branched from the tandem passage, respectively; A first hydraulic control valve having;
A second hydraulic control valve group having at least one second hydraulic control valve disposed between the parallel passage of the first hydraulic control valve and the tank and having a closed center type switching valve;
An orifice for negative control pressure detection disposed between the first hydraulic control valve and the tank and on the tandem passage;
Among the plurality of open center type switching valves, a flow rate control valve with a pressure compensation function disposed between the open center type switching valve disposed on the most downstream side and the orifice, and connected to the tandem passage;
A bypass passage connecting a downstream side of the flow rate control valve with pressure compensation function and an upstream side of the second hydraulic control valve group via a check valve;
Hydraulic drive device with   A load sensing switching valve arranged between the open center type switching valve arranged on the most downstream side and the upstream side of the flow rate control valve with pressure compensation function and on the tandem passage and capable of blocking the tandem passage The hydraulic drive device according to claim 1, comprising:

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