JP5791360B2 - Hydraulic circuit for construction machinery - Google Patents

Description

  The present invention relates to a hydraulic circuit of a construction machine using a split pump of variable displacement type 1 cylinder 2 port discharge.

  An example of this type of hydraulic circuit is described in Patent Document 1. In the hydraulic circuit described in, for example, FIG. 8 of Patent Document 1, the pilot pump pressure from the non-operation signal generating valve (15) when all of the first and second system directional control valves are not operated. Is used for the negative control pressure, and the pressure oil from the split pump (51) is returned from the unload valve (2, 3) to the full tank (54). Thereby, the pressure loss (energy loss) when the actuator is not used is reduced.

International publication WO2009 / 123407 (FIG. 8)

  However, in this hydraulic circuit, when only one actuator is used, negative control pressure is also generated in the unload passage of the unused system, causing energy loss.

  The present invention has been made in view of the above circumstances, and its purpose is to reduce the pressure loss (energy loss) of the other system that is not operated more than before when only one actuator of the system is operated. It is to provide a hydraulic circuit of a construction machine that can be reduced.

Means and effects for solving the problems

  To achieve the above object, the present invention provides a first unload passage of a first system connected to one discharge port of a split pump with a regulator for controlling a discharge flow rate, and connected to the first unload passage. A first direction switching valve of a first system for supplying and discharging oil to the actuator, a first throttle of a first system disposed in the first unload passage on the downstream side of the first direction switching valve, and the split A second unload passage of the second system connected to the other discharge port of the pump, a second directional control valve of the second system connected to the second unload passage and for supplying and discharging oil to the actuator, The second throttle of the second system disposed in the second unload passage on the downstream side of the second directional control valve, the first negative control pressure that is the hydraulic pressure upstream of the first throttle, and the upstream of the second throttle 2nd negative control which is the hydraulic pressure of the side A low pressure selection valve that outputs the lower hydraulic pressure of the pressure to the regulator as a third negative control pressure, and is disposed between the upstream side of the first throttle and the low pressure selection valve. When the first negative control pressure and the pilot pump pressure are input and all the first directional control valves of the first system are not operated, the first negative control pressure is output instead of the first negative control pressure. An auxiliary unload valve and a first unload that is arranged upstream of the first throttle and discharges oil from the split pump to the tank according to the output of the first auxiliary unload valve and the third negative control pressure A hydraulic circuit for a construction machine is provided.

  According to this configuration, when all the first direction switching valves of the first system are not operated, even if the second direction switching valves of the second system are operated, they are output from the first auxiliary unloading valve. Due to the pilot pump pressure, the oil from the split pump that is about to flow through the first unload passage of the first system is discharged from the first unload valve to the tank. Thereby, the pressure loss (energy loss) of the 1st system which is not operated can be reduced rather than before.

  In the present invention, it is preferable that the first auxiliary unload valve connects an upstream side of the first throttle to a tank when a pilot pump pressure is output to the first unload valve.

  According to this configuration, the pressure oil can be returned to the tank also from the first auxiliary unload valve in parallel with the first throttle, and the pressure loss (energy loss) of the first system can be further reduced.

  Furthermore, in the present invention, it is preferable that the first unloading valve is disposed upstream of the first directional switching valve.

  According to this configuration, the amount of pressure oil passing through the first direction switching valve is reduced, and the pressure loss (energy loss) of the first system can be further reduced.

It is a circuit diagram showing a hydraulic circuit concerning one embodiment of the present invention. It is the A section enlarged view of FIG. It is the B section enlarged view of FIG. It is a graph which shows the discharge flow rate characteristic of a split pump, and the opening characteristic of an unload valve.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. An embodiment as a hydraulic circuit of a hydraulic excavator is shown below. FIG. 1 is a circuit diagram showing a hydraulic circuit 1 according to an embodiment of the present invention. 2 is an enlarged view of a portion A in FIG. 1, and FIG. 3 is an enlarged view of a portion B in FIG. The hydraulic circuit 1 according to the present embodiment can also be applied to construction machines other than hydraulic excavators.

  As shown in FIG. 1, a hydraulic excavator to which the hydraulic circuit 1 is applied includes a split pump 51 with a regulator 52 that controls the discharge flow rate of pressure oil, a pump 53, a pilot pump 54, tanks 55 and 59, and bucket hydraulic pressure. A cylinder 56, a boom hydraulic cylinder 57, a hydraulic cylinder 58, a dozer hydraulic cylinder 60, a traveling hydraulic motor (not shown), and the like are provided. The hydraulic circuit 1 is assembled with respect to these hydraulic cylinders (56 to 58, 60), actuators such as a traveling hydraulic motor, pumps (51, 53, 54), and a regulator 52.

  The split pump 51 is a variable-capacity one-cylinder two-port discharge pump, and discharges the same amount of pressure oil from the two discharge ports 51a and 51b.

(Configuration of hydraulic circuit)
(Unload passage)
As shown in FIGS. 1 to 3, the hydraulic circuit 1 includes a first unload passage 12 connected to one discharge port 51 a of the split pump 51 and a second unload passage 51 b connected to the other discharge port 51 b of the split pump 51. And an unload passage 13. The first unload passage 12 and the second unload passage 13 both communicate with the tank 55. The first unload passage 12 is a first system unload passage, and the second unload passage 13 is a second system unload passage. The hydraulic circuit 1 also includes a third unload passage 29 of a third system connected to the pump 53. The third unload passage 29 also communicates with the tank 55.

(Direction switching valve)
The hydraulic circuit 1 includes four first direction switching valves 4w to 4z in the first system connected in series to the first unload passage 12, and three second systems in the second system connected in series to the second unload passage 13. Two-way switching valves 5w to 5y are provided. The first direction switching valves 4w to 4z and the second direction switching valves 5w to 5y are all center bypass type and hydraulic pilot type direction switching valves. The hydraulic circuit 1 also includes three third direction switching valves 6w to 6y of a third system connected in series to the third unload passage 29.

  For example, the first direction switching valve 4x is a valve for supplying and discharging pressure oil to the boom hydraulic cylinder 57, the second direction switching valve 5y is a valve for supplying and discharging pressure oil to the hydraulic cylinder 58, and the third The direction switching valve 6x is a valve that supplies and discharges pressure oil to and from the dozer hydraulic cylinder 60.

  Here, among the first direction switching valves 4w to 4z, the first throttle 10 of the first system is provided in the first unload passage 12 between the first direction switching valve 4z on the most downstream side and the tank 55. It has been. Similarly, the second throttle 11 of the second system is provided in the second unload passage 13 between the second direction switching valve 5y on the most downstream side and the tank 55 among the second direction switching valves 5w to 5y. It has been.

  Further, sub valves 17w to 18y are integrally provided for all the direction switching valves 4w to 5y of the first system and the second system, respectively. The sub valves 17w to 18y are center bypass type valves. Further, a pilot passage 20 that branches to the first pilot passage 24, the second pilot passage 25, and the third pilot passage 26 on the downstream side is connected to a pilot pump 54. The four sub valves 17w to 17z of the first system are connected in series to the first pilot passage 24, and the three sub valves 18w to 18y of the second system are connected to the second pilot passage 25 in series. The sub-valves 17w to 18y are in the communication position when the corresponding direction switching valves 4w to 5y are in the neutral position (when not operated), and when the direction switching valves 4w to 5y are in the switching position (when operated). It is formed to be a blocking position.

  A first pilot line throttle 19 is provided in the first pilot passage 24 upstream of the sub valve 17z, and a second pilot line throttle 30 is provided in the second pilot passage 25 upstream of the sub valve 18y. The third pilot passage 26 is also provided with a throttle before reaching the sub valve, and the first pilot passage 24, the second pilot passage 25, and the third pilot passage 26 are all in communication with the tank 55. .

(Low pressure selection valve)
Further, the hydraulic circuit 1 uses the lower one of the first negative control pressure, which is the upstream hydraulic pressure of the first throttle 10, and the second negative control pressure, which is the upstream hydraulic pressure of the second throttle 11, as the third negative control pressure. The low-pressure selection valve 9 that outputs to the regulator 52 is provided. Here, the output of a first auxiliary unloading valve (to be described later) (first negative control pressure or pilot pump pressure from the first pilot passage 24) is input to one chamber 91 of the low pressure selection valve 9. The other chamber 92 is supplied with the output of a second auxiliary unload valve (second negative control pressure or pilot pump pressure from the second pilot passage 25), which will be described later.

  Further, a regulator pilot passage 15 that connects the low-pressure selection valve 9 and the regulator 52 is provided. The third negative control pressure output from the low pressure selection valve 9 is input to the regulator 52 through the regulator pilot passage 15.

(Auxiliary unloading valve)
The hydraulic circuit 1 includes a first auxiliary unloading valve 7 disposed between the most downstream first direction switching valve 4z (upstream of the first throttle 10) and the low pressure selection valve 9, and the most downstream side. And a second auxiliary unloading valve 8 disposed between the low-pressure selection valve 9 and the second direction switching valve 5y (upstream of the second throttle 11). The configuration of the first auxiliary unloading valve 7 of the first system and the configuration of the second auxiliary unloading valve 8 of the second system are the same except that the systems are different from each other. In the description of the first auxiliary unloading valve 7 described below, the configuration of the second auxiliary unloading valve 8 is described by replacing “first” with “second”.

  The first auxiliary unloading valve 7 receives the first negative control pressure that is the hydraulic pressure on the upstream side of the first throttle 10 and the pilot pump pressure from the first pilot passage 24, and all the first direction switching valves of the first system. It is a valve configured to output the pilot pump pressure instead of the first negative control pressure when 4w to 4z are not operated.

  Here, the first auxiliary unloading valve 7 includes a pilot pump pressure output position 7a and a first negative control pressure output position 7b. The pilot pump pressure output position 7a communicates with the first pilot passage 24 on the upstream side of the first pilot line throttle 19 and the pilot passage 14 connected to the low pressure selection valve 9 and the first unload valve 2, and the first This is a position where the first unload passage 12 on the upstream side of the throttle 10 and the tank 55 communicate with each other. The first negative control pressure output position 7 b is a position where the first unload passage 12 and the pilot passage 14 on the upstream side of the first throttle 10 communicate with each other.

  The pressure between the first pilot line throttle 19 and the sub valve 17z is input to one chamber 73 of the first auxiliary unloading valve 7, and the spring 72 is input to the other chamber 71 of the first auxiliary unloading valve 7. (Biasing means) is disposed, and the pressure on the downstream side of the first throttle 10 is input. The first auxiliary unload valve 7 is moved to the pilot pump pressure output position 7a by the spring 72 disposed in the other chamber 71, and the sub valves 17w to 17z are moved to the shut-off position in conjunction with the first direction switching valves 4w to 4z. Thus, when the pilot pump pressure from the pilot pump 54 is introduced into the one chamber 73, the first negative control pressure output position 7b is switched against the urging force of the spring 72.

(Unload valve)
The hydraulic circuit 1 includes a first unload valve 2 that discharges oil from the split pump 51 to the tank 59 according to the output of the first auxiliary unload valve 7 and the third negative control pressure, and a second auxiliary unload valve. And a second unload valve 3 that discharges oil from the split pump 51 to the tank 59 in accordance with the output of No. 8 and the third negative control pressure. The configuration of the first unload valve 2 in the first system and the configuration of the second unload valve 3 in the second system are the same except that the systems are different from each other. In the description of the first unloading valve 2 described below, the configuration of the second unloading valve 3 is described by replacing “first” with “second”.

  The upstream passage 27 of the first unload valve 2 is connected to the first unload passage 12 upstream of the first directional switching valve 4 w, and the downstream passage 28 of the first unload valve 2 communicates with the tank 59. ing.

  Here, the first unload valve 2 includes a cutoff position 2b and a communication position 2a, and the output (first negative control pressure) of the first auxiliary unload valve 7 is provided in one chamber 21 of the first unload valve 2. (Pilot pump pressure from the pilot pump 54) is input, the third negative control pressure is input to the other chamber 22 of the first unload valve 2, and a spring 23 (biasing means) is arranged. The communication position 2a is reached when the output pressure of the first auxiliary unloading valve 7 is higher than the sum of the third negative control pressure and the pressure of the spring 23. Here, the state where the communication position 2a is reached means a state where the opening area of the first unload valve 2 is not zero, that is, only a state where the opening area of the valve is maximum. Absent. Note that the third negative control pressure is input from the low pressure selection valve 9 to the other chamber 22 of the first unload valve 2 through the pilot passage 16 branched from the regulator pilot passage 15.

(Unload flow control valve)
The hydraulic circuit 1 also includes a first unload flow control valve 31 provided in a downstream passage 28 of the first unload valve 2 between the first unload valve 2 and the tank 59. The first unload flow control valve 31 has a shut-off position and a communication position. A pressure on the downstream side of the first unload valve 2 is input to one chamber 33 and a spring 35 (biasing means) is disposed. The pressure of the first unload passage 12 upstream of the first direction switching valve 4w (pressure upstream of the first unload valve 2) is input to the chamber 34. Similarly, the hydraulic circuit 1 includes a second unload flow control valve 32 provided in a downstream passage of the second unload valve 3 between the second unload valve 3 and the tank 59.

(Hydraulic excavator operation)
Here, the characteristics of the split pump 51 and the unload valves 2 and 3 will be described first. FIG. 4 is a graph showing the discharge flow rate characteristics of the split pump 51 and the opening characteristics of the unload valves 2 and 3.

  As shown in FIG. 4A, the discharge flow rate characteristic of the split pump 51 is adjusted by the regulator 52. When the negative control pressure is 0 to Pf, the maximum flow rate Qmax is obtained. When the negative control pressure is Ps, the pressure decreases in proportion to the increase of the negative control pressure. Note that Pf <Ps. Pf is the maximum negative control pressure when the discharge flow rate of the split pump 51 is maximum (Qmax), and Ps is the minimum negative control pressure when the discharge flow rate of the split pump 51 is minimum (Qmin). is there. The discharge flow rate of the split pump 51 refers to the discharge flow rate discharged from one of the two discharge ports 51a and 51b.

  As shown by the solid line in FIG. 4 (b), the opening characteristics of the unload valves 2 and 3 are 0 (blocking position 2b) when the negative control differential pressure is zero. When the pressure is 0 to (Ps−Pf), the pressure increases in proportion to the increase in the negative control differential pressure (unload valve stroke intermediate position (communication position)). When the negative control differential pressure is Ps−Pf or more, the maximum opening area (an Load valve stroke maximum position (communication position)). Note that the amount of oil flowing through the unload valves 2 and 3 increases as the opening area of the unload valves 2 and 3 increases.

  In the example shown in FIG. 4B, the opening characteristics of the unload valves 2 and 3 are linear. However, the unload valves 2 and 3 may be changed depending on the manufacturing convenience of the unload valves 2 and 3 and the preference of the operator. The aperture characteristic of 3 may be non-linear. For example, as shown by the alternate long and short dash line in FIG. 4 (b), by making the opening characteristic concave, the supply flow rate at the time of the composite operation can be increased, and the pressure can be increased only at the time of the additional composite operation. The power of operation increases. Further, as indicated by a two-dot chain line in FIG. 4B, the soft feeling of the operation is increased by making the opening characteristics convex.

  Next, the operation of the hydraulic excavator (the operation of the hydraulic circuit 1) will be described with reference to FIGS. First, it is assumed that all the direction switching valves 4w to 5y of the first system and the second system are not operated. At this time, since all the sub valves 17w to 18y are in the communication position, the pilot pump pressure oil flowing through the first pilot passage 24 and the second pilot passage 25 is discharged to the tank 55. Therefore, the auxiliary unloading valves 7 and 8 are both in the pilot pump pressure output position (7a) by the biasing force of the spring (72). As a result, the output from the auxiliary unload valves 7 and 8 becomes the pilot pump pressure from the pilot pump 54. As a result, a high pressure (> Ps) pilot pump pressure is introduced from the low pressure selection valve 9 to the regulator 52, and the discharge flow rates from the discharge port 51a and the discharge port 51b of the split pump 51 are both minimized (Qmin) ( (See FIG. 4 (a)).

  For example, it is assumed that the actuator is operated by operating only the second direction switching valve 5w from this state. At this time, the sub valve 18w is in the shut-off position, whereby the pilot pump pressure oil flowing through the second pilot passage 25 is introduced into one chamber of the second auxiliary unloading valve 8, and the second auxiliary unloading valve 8 becomes the second negative control. Switch to pressure output position. As a result, the second negative control pressure is output to the second unload valve 3 and the low pressure selection valve 9, and the second negative control pressure is introduced from the low pressure selection valve 9 to the regulator 52. As a result, the discharge flow rate from the discharge port 51a and the discharge port 51b of the split pump 51 both increases to the required flow rate of the second system.

  On the other hand, since the direction switching valves 4w to 4z of the first system are not operated, all the corresponding sub valves 17w to 17z remain in the communication position, and the first auxiliary unloading valve 7 is connected to the pilot pump pressure output position 7a. Maintain the state. As a result, the pilot pump pressure from the pilot pump 54 is introduced into one chamber 21 of the first unload valve 2, and the second negative control pressure is introduced into the other chamber 22 via the second auxiliary unload valve 8. Is done. Since the pilot pump pressure from the pilot pump 54 is high, the opening area of the first unload valve 2 becomes the maximum opening area (maximum position of the unload valve stroke) by this pilot pump pressure, and the pressure oil in the first system is 1 Unload valve 2 discharges to tank 59. In general, the negative control pressure is set to a pressure lower than 3 MPa, and the pilot pump pressure from the pilot pump 54 is set to 3 MPa or more. The pilot pump pressure is set to a pressure higher than the sum of the biasing force of the spring 23 and the negative control pressure.

  Thus, according to the hydraulic circuit 1 of the present embodiment, when all the first direction switching valves 4w to 4z of the first system are not operated, the second direction switching valves of the second system are operated. Even so, the oil from the split pump 51 that is about to flow through the first unload passage 12 is discharged from the first unload valve 2 to the tank 59 by the pilot pump pressure output from the first auxiliary unload valve 7. . As a result, the pressure loss (energy loss) of the first system that is not operated can be reduced as compared with the conventional system.

  When the first auxiliary unload valve 7 is in the pilot pump pressure output position 7a, the pilot pump pressure is output to the first unload valve 2, and the upstream side of the first throttle 10 is connected to the tank 55. Therefore, the pressure oil in the first unload passage 12 can be returned to the tank 55 also from the first auxiliary unload valve 7 in parallel with the first throttle 10, and the pressure loss (energy loss) of the first system is further reduced. can do.

  Furthermore, since the first unloading valve 2 is disposed upstream of the first directional switching valve 4w located on the most upstream side, the amount of pressure oil passing through the first directional switching valves 4w to 4z is reduced, The pressure loss (energy loss) of the first system can be further reduced.

  The arrangement position of the first unloading valve 2 may be on the upstream side of the first throttle 10, and does not necessarily need to be on the upstream side of the first direction switching valve 4w (the same applies to the second unloading valve 3). ).

  When both the direction switching valves 4w to 4z of the first system and the direction switching valves 5w to 5y of the second system are operated and the required flow rate of the second system is greater than the required flow rate of the first system, The load valve 2 switches (moves) from the shut-off position 2b to the communication position 2a by a stroke amount corresponding to the negative control differential pressure (the absolute value of the difference between the first negative control pressure and the second negative control pressure). The surplus oil of the first system (the amount of oil corresponding to the negative control differential pressure) is discharged to the tank 59.

  By adding the first unload flow control valve 31 and the second unload flow control valve 32 to the downstream passage of the first unload valve 2 and the downstream passage of the second unload valve 3, respectively, the load pressure of the actuator Regardless of whether or not the excess flow amount of oil corresponding to the opening of the unload valves 2 and 3 (the operation amount of the direction switching valve) can always be released to the tank 59, the deterioration of operability can be suppressed. The unload flow control valves 31 and 32 are not essential valves and may be omitted.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. .

  For example, in the above-described embodiment, an example in which a hydraulic pilot type directional switching valve is employed has been described, but a manual type directional switching valve may be employed. Furthermore, a manual type directional control valve and a hydraulic pilot type directional control valve may be mixed.

1: Hydraulic circuit 2: First unloading valve 3: Second unloading valve 4w, 4x, 4y, 4z: First direction switching valve 5w, 5x, 5y: Second direction switching valve 7: First auxiliary unloading valve 8: second auxiliary unloading valve 9: low pressure selection valve 10: first throttle 11: second throttle 12: first unloading passage 13: second unloading passage 51: split pump 52: regulator 54: pilot pump 55, 59: Tank

Claims (3)

A first unload passage of the first system connected to one discharge port of a split pump with a regulator for controlling the discharge flow rate;
A first directional valve of a first system connected to the first unload passage and supplying and discharging oil to the actuator;
A first throttle of a first system disposed in the first unload passage downstream of the first directional control valve;
A second unload passage of the second system connected to the other outlet of the split pump;
A second direction switching valve of a second system connected to the second unload passage and supplying and discharging oil to and from the actuator;
A second throttle of the second system disposed in the second unload passage on the downstream side of the second directional control valve;
A low pressure that outputs the lower hydraulic pressure of the first negative control pressure that is the hydraulic pressure upstream of the first throttle and the second negative control pressure that is the hydraulic pressure upstream of the second throttle to the regulator as the third negative control pressure. A selection valve;
In the hydraulic circuit of construction machinery with
When the first negative control pressure and the pilot pump pressure are input and all the first directional control valves of the first system are not operated, disposed between the upstream side of the first throttle and the low pressure selection valve. A first auxiliary unloading valve that outputs the pilot pump pressure instead of the first negative control pressure;
A first unload valve for discharging oil from the split pump to the tank in accordance with the output and the third negative control pressure before Symbol first auxiliary unloading valve,
A hydraulic circuit for a construction machine, comprising: In the hydraulic circuit of the construction machine according to claim 1,
The hydraulic circuit of a construction machine, wherein the first auxiliary unload valve connects an upstream side of the first throttle to a tank when a pilot pump pressure is output to the first unload valve. In the hydraulic circuit of the construction machine according to claim 1 or 2,
The hydraulic circuit for a construction machine, wherein the first unloading valve is disposed upstream of the first directional control valve.