JP5454439B2 - Hydraulic control device of excavator - Google Patents

Description

  The present invention relates to a hydraulic control device for a hydraulic excavator that has improved control contents during combined operation of lowering a boom and pushing an arm.

  As shown in FIG. 3, the hydraulic excavator includes a crawler-type lower traveling body 1 and an upper revolving body 2 that is mounted on the lower traveling body 1 so as to be rotatable around an axis perpendicular to the ground. To do.

  The upper swing body 2 is equipped with a boom 3, an arm 4, a bucket 5, and a work attachment 9 including a boom, an arm, and bucket cylinders 6, 7, and 8 for driving the boom 3. Various operations such as excavation, loading, and leveling are performed by pushing (pivoting upward) / pulling (rotating downward) 4 and excavating (rake) / returning bucket 5.

  Further, as other hydraulic actuators, left and right traveling motors that drive the lower traveling body 1 and a swing motor (none of which is shown) that swings the upper swing body 2 are provided.

  A conventional hydraulic circuit in this hydraulic excavator is shown in FIG.

  Here, two hydraulic pumps (first and second hydraulic pumps) 10 and 11 driven by an engine (not shown) are provided, and the first hydraulic pump 10 has left and right cylinders 6, 7 and 8 respectively. A circuit for driving a boom, arm cylinders 6 and 7 and a swing motor and a travel motor on the opposite side (second group) with the one side travel motor (first group) and the second hydraulic pump 11 is illustrated.

  However, hydraulic actuators other than the boom and arm cylinders 6 and 7 are not directly related to the present invention. In order to simplify the circuit configuration as much as possible and facilitate the understanding of the present invention, both cylinders 6 and 7 and related parts thereof are used. Only will be shown and described.

  As the boom and arm control valves, the first and second boom control valves 12 and 13 and the second hydraulic pump 11 are used as the hydraulic source in the first group G1 using the first hydraulic pump 10 as the hydraulic source. The second group G2 is provided with both boom second and arm first control valves 14 and 15, respectively.

  Each control valve 12-15 is comprised as a hydraulic pilot switching valve which switches and operates between a neutral position and a both-sides operation position with pilot pressure.

  Each of the control valves 12 to 15 has a center bypass passage CB. The center bypass passage CB is fully opened at the neutral position, and is throttled in accordance with the operation amount at both side operation positions (the maximum operation amount is fully closed). .

  The control valves 12 and 13 of the first group G1 and the control valves 14 and 15 of the second group G2 are respectively connected to the center bypass lines 16 and 17 for communicating the center bypass passages CB with the hydraulic pumps 10 and 11, respectively. The pump ports are connected by parallel circuits 18 and 19 that connect the pump ports in parallel.

In this case, during the combined operation of pulling the arm and raising the boom, the pump discharge oil is not supplied only to the arm cylinder 7 on the relatively light load side.
(i) In both groups G1 and G2, the arm control valves 13 and 15 are disposed downstream of the hydraulic pumps 10 and 11 (the boom control valves 12 and 14 are upstream),
(ii) A throttle 20 is provided on the inlet side of the second arm control valve 13 in the parallel circuit 18 of the first group G1.

  As a result, during the combined arm pulling / boom raising operation, the discharge oil from the first hydraulic pump 10 is preferentially supplied to the boom cylinder 6 and the operation of the cylinder 6 is ensured.

  At this time, the oil discharged from the second hydraulic pump 11 is sent to the arm cylinder 7 via the parallel circuit 19 and the first arm control valve 15 of the second group G2, so that a necessary flow rate of the arm cylinder 7 is secured. .

  On the other hand, boom and arm remote control valves 21 and 22 as operating means are provided, and the operation of the control valves 12 to 15 is controlled by the pilot pressure from both remote control valves 21 and 22.

  FIG. 4 shows only the boom lowering pilot line 23 and the arm pushing side pilot line 24 among the pilot lines connecting the remote control valves 21 and 22 and the control valves 12 to 15.

  Incidentally, in a hydraulic excavator, although not shown, a straight running valve is usually provided on the uppermost stream side of both groups G1 and G2, and this straight running valve allows the oil discharged from the second hydraulic pump 10 to travel left and right during straight running. While being distributed and supplied to the motors in equal amounts, it is configured to ensure the required flow rate by merging the oil discharged from both hydraulic pumps 10 and 11 during a combined operation in which hydraulic actuators other than traveling motors belonging to the same group are operated simultaneously. Is done.

  At this time, if the bypass line of the group that has not been operated is connected to the tank T, all the pump discharge oil is unloaded, and the above merging action is not performed.

  Therefore, cut valves 25 and 26 are provided on the most downstream side of the center bypass lines 16 and 17.

  The cut valves 25 and 26 are provided between a communication position A where the bypass lines 16 and 17 are communicated with the tank T by a pilot pressure applied to the pilot ports 25a and 26a and a block position B where the bypass lines 16 and 17 are blocked. It is configured as a hydraulic pilot switching valve that switches and operates, and the bypass lines 16 and 17 are shut off by the cut valves 25 and 26 during the combined operation.

  Specifically, the operation amount at the time of the composite operation is detected, the electromagnetic proportional valve is operated via the controller, and the opening area of the cut valves 25 and 26 (the amount of movement to the block position b) is increased according to the operation amount. A configuration is adopted in which control is performed in the direction of decreasing with the operation amount (fully closing with the maximum operation amount).

  The above circuit configuration is shown in Patent Documents 1 and 2.

JP 2007-23606 A Japanese Patent Laid-Open No. 10-102547

  In the hydraulic excavator, a combined operation of pushing the arm 4 while lowering the boom 3 during leveling work is performed. In addition, a combined operation of turning while lowering the boom and pushing the arm is also performed when returning after dumping.

According to the conventional circuit configuration in such a boom lowering / arm pushing combined operation,
(I) The flow rate supplied to the arm cylinder 7 from the first hydraulic pump 10 via the parallel circuit 18 is originally throttled by the throttle 20 provided on the pressure oil inlet side of the arm second control valve 13;
(II) Since the second arm control valve 13 is disposed downstream of the first boom control valve 12, the first boom control valve 12 is moved from the neutral position A to the boom raising position B or the boom lowering position C. When switched, the flow rate supplied to the arm cylinder 7 via the center bypass line 16 is reduced by narrowing the center bypass passage CB,
Due to these two points, there was a situation where the arm cylinder flow rate was insufficient.

  As a result, a necessary arm pushing speed does not appear and a cycle time is lost.

  In addition, since the useless boost pressure is generated by the throttling action (I) and (II), energy loss and heat generation occur, and the pump pressure of both the hydraulic pumps 10 and 11 rises so that the horsepower control works and both The flow rate of the pump is reduced, and the operability of other hydraulic actuators is adversely affected, for example, the turning speed is lowered during combined operation including turning.

  Accordingly, the present invention provides a hydraulic control of a hydraulic excavator that can secure the necessary flow rate of the arm cylinder at the time of the combined operation of lowering the boom / pushing the arm or the combined operation including this, and can suppress the generation of useless boost pressure due to the throttle. A device is provided.

  According to the first aspect of the present invention, the boom cylinder for driving the boom of the work attachment, the arm cylinder for driving the arm, the hydraulic pump as the hydraulic source of both the cylinders, and the operation means for both the boom and the arm are used. Both control valves for the boom and the arm for controlling the operation of the cylinders, and the control valves are connected to the center bypass line for connecting the center bypass passages with the boom control valve as the upstream side, A throttle that is connected by a parallel circuit that connects the pump ports in parallel and that preferentially supplies pump discharge oil to the boom control valve is provided on the inlet side of the parallel circuit of the arm control valve. In addition, the center bypass line In the hydraulic control device of a hydraulic excavator provided with a cut valve on the flow side to cut off the center bypass line as necessary, the center bypass passage opens at both the neutral and boom lowering operations of the boom control valve. The center bypass line is configured to be controlled in the cutoff direction on the most downstream side during the boom lowering operation.

  According to a second aspect of the present invention, in the configuration of the first aspect, at the time of the boom lowering operation, the cut valve control means operates the cut valve to the cut-off side to control the center bypass line in the cut-off direction. is there.

  According to a third aspect of the present invention, in the configuration of the second aspect, the cut valve control means is configured to control the opening area of the cut valve in a direction of decreasing with a large operation amount in accordance with a boom lowering operation amount. Is.

  According to a fourth aspect of the present invention, in the configuration of the third aspect, a remote control valve as the boom operating means, and a hydraulic pilot valve operated by a pilot pressure supplied through a pilot pressure line from the remote control valve as the boom control valve, Using the hydraulic pilot valve controlled by the pilot pressure applied to the pilot port as the cut valve, respectively, and connecting the pilot pressure line on the boom lower side of the remote control valve to the pilot port of the cut valve, the cut valve control means Is configured.

  According to a fifth aspect of the present invention, in the configuration of the third aspect, a boom lowering that detects a boom lowering operation amount of the boom control valve using a hydraulic pilot valve controlled by a pilot pressure applied to a pilot port as the cut valve. An operation amount detection means, a controller that outputs a command signal corresponding to the boom lowering operation amount detected by the boom lowering operation amount detection means, and a secondary pressure corresponding to the command signal from the controller is piloted to the cut valve The cut valve control means is constituted by an electromagnetic proportional valve supplied as a pressure.

  According to the present invention, at the time of boom lowering operation, the center bypass passage of the boom control valve is configured not to be throttled as in the prior art but to open in the same manner as in the neutral state. During the combined operation including the above, the required flow rate can be supplied to the arm cylinder through the center bypass line.

  As a result, the speed of pushing the arm can be increased to increase the cycle time, and the operability of other hydraulic actuators such as a decrease in the turning speed due to a decrease in the pump flow rate can be prevented.

  Moreover, since a useless boost pressure due to the restriction of the bypass passage is not generated, energy loss and heat generation can be suppressed.

  If the center bypass passage of the boom control valve is opened when the boom is lowered as described above, the pump discharge oil is unloaded through the center bypass line when the boom is lowered alone (when the arm control valve is neutral). As a result, the boom lowering operation becomes impossible.

  In this respect, according to the present invention, the center bypass line is controlled in the shut-off direction on the most downstream side during the boom lowering operation, and thus the above-described disadvantage does not occur.

  In this case, according to the inventions of claims 2 to 4, since the shut-off control of the center bypass line is performed using the cut valve originally provided in the circuit, there is no need to add a shut-off valve dedicated for the boom lowering operation. This is advantageous in terms of simplification of circuit configuration and cost.

  According to the third to fifth aspects of the present invention, in order to reduce the opening area of the cut valve, that is, the unload flow rate in accordance with the boom lowering operation amount, the operability is achieved by sending the boom cylinder a flow rate corresponding to the boom lowering operation amount. Will be good.

  In this case, in the invention of claim 4, since the opening of the cut valve is directly controlled by the boom lowering pilot pressure of the remote control valve, the circuit configuration is simple and the operation reliability is high.

  On the other hand, in the invention of claim 5, in order to detect the boom lowering operation amount, send a command signal from the controller to the electromagnetic proportional valve, and control the opening of the cut valve with the secondary pressure of the proportional valve. Proportional valve control is performed in the same manner as the original control, so that it is easy to use the cut valve.

It is a circuit block diagram which shows 1st Embodiment of this invention. It is a circuit block diagram which shows 2nd Embodiment of this invention. It is a schematic side view which shows the whole structure of a hydraulic shovel. It is a conventional circuit block diagram.

  An embodiment of the present invention will be described with reference to FIGS.

  In the following embodiment, in accordance with the description of the background art, both the first and second hydraulic pumps 10 and 11 are provided, and the first hydraulic pump 10 includes the boom, arm, and bucket cylinders 6, 7, and 8 and the left and right sides. A circuit that drives the boom and arm cylinders 6 and 7, the turning motor, and the travel motor on the opposite side (second group) with the travel motor (first group) and the second hydraulic pump 11 is applied.

  Similarly to FIG. 4, only the boom and arm cylinders 6 and 7 and their related parts are shown and described in order to simplify the circuit configuration as much as possible to facilitate understanding of the present invention.

  In FIGS. 1 and 2, portions different from the conventional circuit shown in FIG.

  In the embodiment, the following points are the same as those of the prior art shown in FIG.

  (I) As the boom and arm control valves, the first and second boom control valves 12A and 13 and the second hydraulic pump 11 are added to the first group G1 using the first hydraulic pump 10 as a hydraulic source. The second group G2 having the hydraulic pressure source as a hydraulic source is provided with both boom second and arm first control valves 14 and 15, respectively.

  (II) Each control valve 12A, 13-15 is configured as a hydraulic pilot switching valve that is switched between a neutral position and a two-side operation position by a pilot pressure.

  (III) Each control valve 12A, 13-15 has a center bypass passage CB, and the opening area of the center bypass passage CB is maximized at the neutral position except for the first control valve 12A for the boom, and the two-side operation position The point that is narrowed down according to the operation amount.

  (IV) The control valves 12A and 13 of the first group G1 and the control valves 14 and 15 of the second group G2 are respectively connected to the center bypass line 16, which connects the center bypass passages CB to the hydraulic pumps 10 and 11, respectively. 17 and the parallel circuits 18 and 19 that connect the pump ports in parallel.

  (V) In this case, in the combined operation of arm pulling and boom raising, the pump discharge oil is not supplied only to the arm cylinder 7 on the relatively light load side. The control valves 13 and 15 are disposed downstream of the pumps 10 and 11 (the boom control valves 12 and 14 are upstream), and the second control valve 13 for the arm in the parallel circuit 18 of the first group G1. A restriction 20 is provided on the inlet side.

  (VI) Boom and arm remote control valves 21 and 22 as operating means are provided, and the operation of the control valves 12A and 13 to 15 is controlled by the pilot pressure from both remote control valves 21 and 22.

  (VII) Cut valves 25 and 26 are provided on the most downstream side of both center bypass lines 16 and 17.

  (VIII) The cut valves 25 and 26 are connected to a communication position A for connecting the bypass lines 16 and 17 to the tank T by a pilot pressure applied to the pilot ports 25a and 26a, and a block position B for blocking the tank T. This is configured as a hydraulic pilot switching valve that switches between the two, and cuts off the bypass lines 16 and 17 by the cut valves 25 and 26 during a combined operation in which hydraulic actuators other than traveling motors belonging to the same group are simultaneously operated. The point that is taken.

  The bypass passage CB of the first boom control valve 12 in the conventional circuit shown in FIG. 4 is fully opened at the neutral position A, and is throttled according to the operation amount at both the boom raising and lowering positions B and C (with the maximum operation amount). It is configured to be fully closed).

  In contrast, in the first boom control valve 12A of both the first and second embodiments, as shown in the figure, the center bypass passage CB is fully opened at both the neutral position B and the boom lowering position C, and the boom raising position RO It is configured so that it can be throttled according to the operation amount only (it is fully closed at the maximum operation amount).

  According to this configuration, during the combined operation of lowering the boom / pushing the arm, or during the combined operation in which, for example, turning is added, the center bypass passage CB of the first boom control valve 12A, the center bypass line 16, the second control for the arm. A necessary flow rate (a flow rate corresponding to an arm pushing operation amount) can be supplied to the arm cylinder 7 through the valve 13.

  As a result, the speed of pushing the arm can be increased to increase the cycle time, and the operability of other hydraulic actuators such as a decrease in the turning speed due to a decrease in the pump flow rate can be prevented.

  Moreover, since a useless boost pressure due to the restriction of the bypass passage CB of the first boom control valve 12A is not generated, energy loss and heat generation can be suppressed.

  If the center bypass passage CB of the first boom control valve 12A is opened during the boom lowering operation as described above, the boom second control valve 13 is neutral (ie, the center bypass CB Since the center bypass line 16 is opened with the first boom control valve 12A switched to the boom lowering position C, the discharge of the first hydraulic pump 10 to be supplied to the boom cylinder 6 is maintained. The oil is unloaded through the center bypass line 16, resulting in a problem that the boom lowering operation becomes impossible.

  Therefore, in both embodiments, during the boom lowering operation, the existing cut valve 25 is used so that the center bypass line 16 is narrowed down to the opening area corresponding to the boom lowering operation amount on the most downstream side.

  Specifically, in the first embodiment (FIG. 1), a cut valve pilot line 27 is connected to the pilot pressure line 23 on the boom lower side of the boom remote control valve 21, and the pilot line 27 is connected to the cut valve 25. It is connected to the pilot port 25a.

  Thus, the cut valve control means 28 is configured, and the cut valve control means 28 automatically controls the cut valve 25 to have an opening area corresponding to the boom lowering operation amount during the boom lowering operation.

  If it carries out like this, the flow volume according to the operation amount can be supplied to the boom cylinder 6 at the time of boom lowering single operation.

  Moreover, since the opening control of the bypass line 16 is performed using the cut valve 25 originally provided in the circuit, it is not necessary to add a dedicated shut-off valve at the time of the boom lowering operation, the circuit configuration is simple and the cost is low. I'm sorry.

  Moreover, since the opening area of the cut valve 25, that is, the unload flow rate is reduced according to the boom lowering operation amount, the operability is improved by sending the boom cylinder 6 the flow rate according to the boom lowering operation amount.

  In this case, the opening of the cut valve 25 is directly controlled by the boom lowering pilot pressure of the remote control valve 21, so that the circuit configuration is simple and the operation reliability is high.

  On the other hand, in the second embodiment (FIG. 2), a pilot pressure sensor 29 that detects a boom lowering pilot pressure (boom lowering operation amount), and a command signal corresponding to the boom lowering operation amount detected by the pilot pressure sensor 29. The cut valve control means 32 is constituted by the controller 30 that outputs the pressure and the electromagnetic proportional valve 31 that supplies the secondary pressure corresponding to the command signal from the controller 30 to the cut valve 25 as a pilot pressure.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained.

  Moreover, since the cut valve 25 is proportionally controlled in the same manner as the original control, the cut valve 25 can be used easily.

Other embodiments
(1) In the above embodiment, the existing cut valve 25 is used as a valve that shuts off the bypass line (controls the opening area) during the boom lowering operation, but a valve different from the cut valve 25 is used. It is also possible to adopt a configuration that is provided and controlled separately from the cut valve 25.

  (2) In the above embodiment, the configuration is such that the opening area of the bypass line 16 is controlled by the cut valve 25 according to the boom lowering operation amount during the boom lowering operation. You may comprise so that it may interrupt | block.

3 Boom 4 Arm 6 Boom Cylinder 7 Arm Cylinder 9 Work Attachment 10 Hydraulic Pump 12A First Control Valve for Boom as Control Valve for Boom 13 Second Control Valve for Arm as Control Valve for Arm CB Center Bypass Path 16 Center Bypass Line 18 Parallel circuit 21 Remote control valve for boom as operation means 22 Remote control valve for arm as operation means 23 Boom lower side pilot pressure line 25 Cut valve 25a Pilot port 27 Cut valve pilot line 28 Cut valve control means 29 Pilot pressure sensor 30 Controller 31 Proportional solenoid valve 32 Cut valve control means

Claims (5)

  A boom cylinder for driving the boom of the work attachment, an arm cylinder for driving the arm, a hydraulic pump as a hydraulic source for both cylinders, and the operation of both cylinders according to the operation of both the boom and arm operating means. Both boom and arm control valves to be controlled are provided, and both control valves connect a center bypass line that connects each center bypass passage with the boom control valve as an upstream side, and each pump port in parallel. A throttle for preferentially supplying pump discharge oil to the boom control valve is provided on the inlet side of the parallel circuit of the arm control valve and connected to the parallel control circuit. If necessary, on the most downstream side In the hydraulic control device of a hydraulic excavator provided with a cut valve that shuts off the center bypass line, the boom control valve is configured such that the center bypass passage is opened both during neutral and during boom lowering operation, and the boom A hydraulic control device for a hydraulic excavator, characterized in that the center bypass line is controlled in the cutoff direction on the most downstream side during the lowering operation.   2. The hydraulic control device for a hydraulic excavator according to claim 1, wherein, at the time of the boom lowering operation, the cut valve control means operates the cut valve to the cutoff side to control the center bypass line in the cutoff direction. .   3. The hydraulic pressure of a hydraulic excavator according to claim 2, wherein the cut valve control means is configured to control the opening area of the cut valve in a direction of decreasing with a large operation amount in accordance with a boom lowering operation amount. Control device.   The boom operation means is controlled by a remote control valve, the boom control valve is controlled by a pilot pressure supplied from the remote control valve through a pilot pressure line through a pilot pressure line, and the cut valve is controlled by a pilot pressure applied to a pilot port. 4. The hydraulic valve according to claim 3, wherein each of the hydraulic pilot valves is used, and the cut valve control means is configured by connecting a pilot pressure line on the boom lower side of the remote control valve to a pilot port of the cut valve. Excavator hydraulic control device.   Using the hydraulic pilot valve controlled by the pilot pressure applied to the pilot port as the cut valve, a boom lowering operation amount detecting means for detecting the boom lowering operation amount of the boom control valve, and the boom lowering operation amount detecting means The cut valve control means includes a controller that outputs a command signal corresponding to the detected boom lowering operation amount, and an electromagnetic proportional valve that supplies a secondary pressure corresponding to the command signal from the controller as a pilot pressure to the cut valve. The hydraulic control device for a hydraulic excavator according to claim 3, wherein

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