JP2005068845A - Hydraulic circuit of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine superior in fuel economy, by improving operability of a work machine in traveling. <P>SOLUTION: This hydraulic circuit of the construction machine is provided with respective ones of left and right travel control valves in a center oil passage of two hydraulic pumps; branches off parallel oil passages from the respective ones from the center oil passage upstream side; is provided with an oil passage for supplying pressure oil of the parallel oil passages to a downstream control valve for respective actuators; and is provided with a rectilinearly traveling valve on the upstream side of center oil passage of the one hydraulic pump and the upstream side of the parallel oil passages of the other hydraulic pump. The hydraulic circuit is provided with a bypass oil passage on the upstream side of the travel control valves of the same side center oil passage from the upstream side of one parallel oil passage; is provided with a variable throttle valve and a check valve in the bypass oil passage; and reduces throttle opening of the throttle valve, when performing arm opening operation or boom raising operation, by operating arm opening side pilot hydraulic pressure of an arm control valve, and boom raising side pilot hydraulic pressure of a boom control valve on a control port of the variable throttle valve via a shuttle valve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a hydraulic circuit technique for improving traveling performance and operability in a combined operation of traveling operation and heavy load operation of a work machine in a construction machine such as a hydraulic excavator.

  2. Description of the Related Art Conventionally, construction machines such as a small hydraulic excavator need to perform other work while traveling as well as stopping the construction machine at a certain place. In this case, there are many cases where straight traveling is required, for example, pipe laying or wood sorting work. Therefore, in the hydraulic circuit of this type of construction machine, various devices have been conventionally used in order to improve the straight running performance by using a plurality of hydraulic pumps and to improve the performance of work during straight running or when stopped. ing.

  2 and 3 show an example of a conventional hydraulic circuit (hereinafter referred to as conventional circuit 1). 2 and 3, the center oil passage 12 of the hydraulic pump 11 controls a travel control valve 14 for controlling the travel motor 13, a swing control valve 15 for controlling a swing motor (not shown), and an arm cylinder. An arm control valve 16 and an oil tank T are connected to each other. Similarly, a straight travel valve 23, a travel control valve 25 for controlling the travel motor 24, a boom control valve 26 for controlling a boom cylinder (not shown), and a bucket cylinder (not shown) are controlled in the center oil passage of the hydraulic pump 21. A bucket control valve 27 and an oil tank T are connected. The control valves 14-16 and 25-27 are connected so that pilot pressure oil acts on the pilot port when each remote control valve (not shown) is operated. Hereinafter, in order to simplify the description, the control valves 15, 16, 26 and / or 27 other than the travel control valves 14, 25 will be referred to as control valves for the work implement.

  Further, the parallel oil passage 18 branched from the center oil passage 12 communicates with the travel straight advance valve 23, and the parallel oil passage 19 joins the input oil passages of the turning control valve 15 and the arm control valve 16. The parallel oil passage 28 branched from the center oil passage 22 joins the input oil passages of the boom control valve 26 and the bucket control valve 27. A bypass oil passage 31 branched from the middle of the parallel oil passage 28 is connected to a throttle 32 and a check valve 33, and is connected upstream of the travel control valve 25 of the center oil passage 22. The state of the travel control valve 23 is switched from A to B or vice versa by the pilot pressure of the spring 23b and the pilot port 23a. Pilot pressure is applied to the pilot port 23a when the traveling control valves 14, 25 and the control valve 15, 16, 26, or 27 of the work implement are operated simultaneously (when traveling and other operations are performed simultaneously). A circuit (not shown) is connected so as to be switched. FIG. 3 shows a case where the pilot pressure is applied and the state is switched to the state (a).

  FIG. 2 shows a circuit in the case of traveling only (or operation of the working machine only). In the case of independent traveling, the pressure oil of the hydraulic pump passes through the center oil passage 12 and is supplied to the traveling control valve 14 and the traveling motor 13, and passes through parallel oil passages 18 and 19 to the control valves 15 and 16 of the work implement. Supplied. Similarly, the pressure oil of the hydraulic pump 21 is supplied to the traveling control valve 25 and the traveling motor 24 through the center oil passage 22, and is supplied to the control valves 26 and 27 of the work implement through the parallel oil passage 28. . Accordingly, since the traveling motors 13 and 24 are respectively supplied from the hydraulic pumps 11 and 21, straight traveling is facilitated.

  FIG. 3 is a circuit for operating the work machine while traveling. In this case, the traveling straight valve 23 switches to the state a. In FIG. 3, the pressure oil of the hydraulic motor 11 flows to the travel control valve 14 through the center oil passage 12 and flows to the travel control valve 25 through the parallel oil passage 18, the travel straight valve 23, and the center oil passage 22. On the other hand, the pressure oil of the hydraulic pump 21 flows through the parallel oil passage 28 to the control valves 26 and 27 of the work implement and passes through the center oil passage 22, the traveling straight valve 23, and the parallel oil passage 19, and the control valve 15 of the work implement. , 16 flow. Therefore, in the case of FIG. 3, an equal amount of pressure oil flows from the hydraulic pump 11 to the travel control valves 14 and 25, and straight travel is possible. In addition, pressure oil from the hydraulic pump 21 flows through the control valves 15, 16, 26, and 27 of the work machine, and work can be performed simultaneously. When the flow rate at which the control valves 15, 16, 26, and 27 of the work machine use the pressure oil of the hydraulic pump 21 is small, surplus pressure oil is supplied to the center oil path 22 through the bypass oil path 31. .

  By the way, in the conventional circuit 1, the turning operation of the upper turning body, the raising operation of the boom, the opening operation of the arm and the like by the turning motor during traveling are performed very slowly from the viewpoint of ensuring safety. In addition, the throttle 32 provided in the bypass oil passage 31 (conventional circuit 1) is devised so that the opening area is reduced (the throttle resistance is increased) so that the operation of the work machine does not greatly affect the straight traveling. ing. Furthermore, when the opening area of the throttle 32 is increased, the hydraulic pressure that flows to the control valve (or the actuator) of the work implement does not increase, and a work that requires a high load pressure such as a boom raising operation may not be performed smoothly. As described above, the conventional circuit 1 has a problem in the operability of the work machine during traveling.

The present applicant has made an invention that has solved the above-mentioned problems and has filed an application (Patent Document 1). FIG. 4 shows a circuit diagram of the second embodiment disclosed in Patent Document 1 (hereinafter referred to as conventional circuit 2). As shown in FIG. 4, the conventional circuit 2 is configured by a variable throttle valve 51 instead of the throttle 32 of the conventional circuit 1, and the upper oil passage throttle 51a has a larger opening area than the lower oil passage throttle 51b (throttle restriction). The upper pilot port is connected to the parallel oil passage 28 via the oil passage 52, and the lower pilot port is connected to the center oil passage 22 via the oil passage 53. That is, the throttle resistance is configured to be small when the hydraulic pressure in the parallel oil passage 28 increases.
Published Patent Publication, 2001-254400, Embodiment 2 (see FIG. 2).

  Further, the lower side of the variable throttle valve 51 is urged by a compression spring 51c having a spring coefficient (k) through a dash port 62, and the spring force (kx) of the spring 51c can be apparently changed by the dash port 62. . The input port of the dash port 62 is connected to the output port of the shuttle valve 63 so that the arm opening side pilot hydraulic pressure of the arm control valve and the raising side pilot hydraulic pressure of the boom control valve act on the input ports 64 and 65 of the shuttle valve 63, respectively. Connected to.

Therefore, the conventional circuit 2 is the same as the conventional circuit 1 when traveling alone. When an operation other than the raising operation of the boom and the opening operation of the arm is performed simultaneously with traveling, the spring force acting on the variable throttle valve 51 is small, so that the combined flow rate from the oil passage 28 to the oil passage 22 can be increased. Therefore, in this case, the amount of decrease in travel speed can be suppressed. Further, when the boom is raised or the arm is opened during traveling, the spring force acting on the variable throttle valve 51 is greatly actuated to switch the throttle of the variable throttle valve 51 from 51a to 51b. Arm opening operation is also possible.

As described above, in the hydraulic circuit of the conventional circuit 1, there is a problem that the traveling speed is reduced at a stroke when the operation of fine operation requiring high load pressure is performed when the traveling straight valve 23 is switched, and the engine fuel ratio. The problem of deterioration also occurred. In the conventional circuit 2, the pilot oil passages 52 and 53 are connected to the upper port and the lower port of the variable throttle valve 51, and the spring 51 is biased via the dash port 62. Adjustment of 62 was complicated and was a problem. If the adjustment is not well made, the rise time of the boom raising operation and the arm opening operation may be delayed, or in some cases, the variable throttle valve 51 may not be switched, and the work is smooth. There was a problem that could not be.
The present invention has been made under the background as described above, solves the above-described problems, improves the operability of the work machine during traveling, and provides a hydraulic circuit for a construction machine having an excellent fuel ratio. It is an issue.

The present invention employs the following configuration as means for solving the above-described problems. That is,
According to the first aspect of the present invention, one of each of the left and right travel control valves is provided in the center oil passage of the two hydraulic pumps, and one or a plurality of control valves for the actuator of the work machine are provided downstream of the center oil passage. At the same time, a parallel oil passage is branched from each of the two center oil passages upstream, and an oil passage for supplying pressure oil of the parallel oil passage to the downstream actuator control valves is provided. In a hydraulic circuit of a construction machine provided with a traveling straight valve upstream of the center oil passage of the hydraulic pump and upstream of the parallel oil passage of the other hydraulic pump, the traveling control valve of the same side center oil passage extends from the upstream of the one parallel oil passage. A bypass oil passage is provided upstream, a variable throttle valve and a check valve are provided in the bypass oil passage, and the arm opening side pilot hydraulic pressure of the arm control valve and the boom control valve block are connected to the control port of the variable throttle valve via a shuttle valve. Reacted with arm up side pilot hydraulic diaphragm opening of the narrowed valve is characterized in that to be smaller when the arm opening operations or boom raising operation.

  As described above, according to the configuration of the present invention, the arm opening side pilot hydraulic pressure of the arm control valve and the boom raising side pilot hydraulic pressure of the boom control valve are applied to the control port of the variable throttle valve via the shuttle valve, Since the throttle opening of the throttle valve is reduced when the arm opening operation or boom raising operation is performed, complicated adjustment is not required, and heavy load operations such as arm opening operation or boom raising operation are smooth. It has the effect that it can be performed. Moreover, the effect that energy consumption can also be saved is obtained.

FIG. 1 is a diagram showing a circuit configuration of Embodiment 1 of the present invention. Embodiments of the present invention will be described below with reference to the drawings. The same components as those of the conventional circuit 2 (FIG. 4) are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 1, the upper side of the variable throttle valve 51 is biased by a spring 51d, and the upper port is connected to an oil tank. The lower pilot port 51e is connected via a shuttle valve 63 to an arm opening side pilot hydraulic pressure 64 of the arm control valve and a boom raising side pilot hydraulic pressure 65 of the boom control valve.

  Since the present embodiment is configured as described above, it functions as follows. In the case of a single operation only for traveling, the travel switching valve 23 is in the state A, and the throttle 51a of the variable throttle valve 51 is in communication, so that the hydraulic pressure of the hydraulic pump 11 and the hydraulic pump 21 is changed to the travel switching valve 14 and Therefore, good running performance can be obtained. Further, when the operation of the work machine other than the arm opening operation and the boom raising operation is performed simultaneously with traveling, the throttle 51a of the variable throttle valve 51 is in communication, and the hydraulic pressure of the hydraulic pump 11 is transferred to the traveling switching valves 14 and 25. Since it is supplied and the surplus pressure of the hydraulic pump 21 is supplied through the throttle 51a, the traveling operation and the operation of the working machine are also performed smoothly.

Further, when a heavy load operation such as an arm opening operation or a boom raising operation is performed simultaneously with traveling, the variable throttle valve 51 is quickly switched to the throttle 51b when the start of the operation is detected. Accordingly, in this case, the hydraulic pressure of the hydraulic pump 21 is not supplied to the travel switching valves 14 and 25, but is supplied exclusively to the arm switching valve 16 or the boom switching valve 26. Therefore, operations such as an arm opening operation or a boom raising operation are performed. The heavy load operation of the machine can be performed smoothly.

  Therefore, according to the present embodiment, smooth operation is possible even when a heavy load operation such as an arm opening operation or a boom raising operation is performed simultaneously with traveling, and an effect that work can be performed efficiently is obtained. Further, since complicated adjustment as in the conventional circuit 2 is not required, there is an effect that maintenance work is facilitated.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this example, and the present invention can be changed even if there is a design change without departing from the gist of the present invention. include. For example, the arrangement of the switching valve of the working machine is not limited to the connection described in FIG. 1, and design changes within the scope of the present invention are allowed.

The structure of embodiment of this invention is shown. The circuit structure of the non-running state of the conventional circuit 1 is shown. The circuit structure of the driving state of the conventional circuit 1 is shown. The circuit structure of the conventional circuit 2 is shown.

Explanation of symbols

11 and 21 Hydraulic pumps 14 and 25 Travel control valve 15 Swing control valve 16 Arm control valve 23 Travel straight valve 26 Boom control valve 27 Bucket control valve 51 Variable throttle valve

Claims (1)

One of each of the left and right travel control valves is provided in the center oil passage of the two hydraulic pumps, and one or a plurality of actuator control valves of the work implement are connected downstream of the center oil passage, and the two centers are simultaneously connected. A parallel oil passage is branched from each upstream of the oil passage, an oil passage is provided for supplying pressure oil in the parallel oil passage to each actuator control valve downstream, and the center oil passage upstream and the other of the one hydraulic pump In the hydraulic circuit of a construction machine provided with a traveling straight valve upstream of the parallel oil passage of the hydraulic pump,
A bypass oil passage is provided from upstream of the one parallel oil passage to the upstream of the traveling control valve of the same center oil passage, a variable throttle valve and a check valve are provided in the bypass oil passage, and a shuttle is provided to the control port of the variable throttle valve The arm opening side pilot hydraulic pressure of the arm control valve and the boom raising side pilot hydraulic pressure of the boom control valve are applied via the valve so that the throttle opening of the throttle valve becomes small when the arm opening operation or boom raising operation is performed. A hydraulic circuit of a construction machine characterized by

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