JP4423149B2 - Construction machinery - Google Patents

Description

  The present invention relates to a permanent working tool such as a bucket, a hydraulic cylinder for a permanent working tool such as a bucket cylinder that drives the permanent working tool, a swingable arm that supports the permanent working tool, a boom, and the like. It has a working arm and a hydraulic cylinder for working arms such as an arm cylinder and a boom cylinder that drive this working arm. Instead of a permanent working tool, a special working tool as an attachment is used as a hydraulic cylinder for the permanent working tool. The present invention relates to a construction machine such as a hydraulic excavator configured to be attached and used.

  A construction machine such as a hydraulic excavator is provided with a permanent work tool such as a bucket for performing construction work such as excavation work, a swingable arm that supports the permanent work tool, and a work arm such as a boom. The permanent work tool is driven by a hydraulic cylinder for a permanent work tool such as a bucket cylinder, and the arm such as an arm or boom is driven so as to be swung by a hydraulic cylinder for the work arm such as an arm cylinder or boom cylinder. . In these construction machines, instead of permanent work tools, special work tools such as earth drills and crushers as attachments can be attached to hydraulic cylinders for permanent work tools such as bucket cylinders. There is something. The present invention seeks to improve particularly a hydraulic drive circuit provided in such a construction machine. As a conventional technique related to the hydraulic drive circuit of this type of construction machine, the hydraulic drive circuit described in Patent Document 1 can be cited.

  Therefore, in order to make it easier to understand the improvements of the present invention, the above-mentioned conventional construction machine in which a special work tool is attached to a hydraulic cylinder for a permanent work tool and a patent provided on such a construction machine can be used. The hydraulic drive circuit described in Document 1 and the technical matters around it will be described with reference to FIGS. FIG. 4 is a side view showing an example of a conventional construction machine that can be used by replacing a special work tool with a permanent work tool, and FIG. 5 shows a conventional work machine that can be applied to the construction machine of FIG. FIG. 6 is an enlarged hydraulic circuit diagram showing an essential part of the hydraulic circuit diagram of FIG. 5, and FIG. 7 is for controlling the movement of various hydraulic cylinders. It is a longitudinal cross-sectional view which shows the internal structure of this direction control valve. Here, the following description will be given by taking as an example the case where the construction machine is a self-propelled hydraulic excavator.

  First, an example of a hydraulic excavator that can be used in place of a permanent work tool by attaching a special work tool as an attachment to a hydraulic cylinder for the permanent work tool will be described with reference to FIG.

  In the figure, 201 is a crawler type lower traveling body capable of traveling on the work site as a base for installing the upper revolving body 202, and 202 is a swivel mounted on the lower traveling body 201 so as to be able to swivel. An upper revolving body comprising a frame 203 and various devices installed on the upper part of the revolving frame 203, 203 is a revolving frame as a base of the upper revolving body 202, 204 is a cab for operating a hydraulic excavator, 205 Is a building cover on which hydraulic pumps 1 and 2 (see FIG. 5) and an engine for driving the hydraulic pump 1 and 2 are installed, 206 is a counterweight for balancing external force acting on the swivel frame 203 when working by the front 210, and 207 is a lower part A crawler type traveling body constituting the traveling body 201, 210 is a working machine of a hydraulic excavator for excavating earth and sand It is a front.

  The lower traveling body 201 includes a pair of crawler traveling bodies 207 on both the left and right sides. The crawler type traveling body 207 is a traveling body that uses an endless chain-shaped crawler belt 207b driven by a wheel (sprocket) 207a as propulsion means. The left and right wheels 207a are driven to rotate by the left traveling motor 11 and the right traveling motor 22 shown in FIGS. 5 and 6, respectively. The turning frame 203 is installed on the lower traveling body 201 so as to be capable of turning, and is turned by the turning motor 12 shown in FIGS. Various devices such as a driver's cab 204, a building cover 205, and a counterweight 206 are installed on the swivel frame 203, and the upper swivel body 202 is configured by these aggregates.

  The front 210 is installed beside the cab 204 on the turning frame 203. The front 210 includes a bucket 211 as a permanent work tool for performing construction work such as excavation work, and includes a boom 212 and an arm 213 as work arms for supporting the bucket 211 and performing various construction work. ing. The bucket 211 is a work tool that is separately attached to the earth auger 136 and cannot be shown. Therefore, only the reference numeral 136 of the earth auger is shown in parentheses. The boom 212 is pivotally mounted on the revolving frame 203 so that the rear end thereof is pivotally mounted. The arm 213 is pivotally pivotally mounted on the front end of the boom 212 so that the bucket 211 is The arm 213 is pivotally attached to the front end of the arm 213 so as to be rotatable and detachable. Further, the front 210 is a hydraulic actuator for driving these permanent work tools and work arms, and the bucket cylinder 13 that is driven to extend and retract to rotate the bucket 211 and the boom 212 that is expanded and contracted to swing. A boom cylinder 14 that is driven so as to move, and an arm cylinder 15 that is driven to extend and contract to swing the arm 213.

  In the hydraulic excavator shown in FIG. 4, a special working tool such as an earth drill 136 or a crusher 36 (see FIGS. 5 and 6) as an attachment is attached to the bucket cylinder 13 instead of the bucket 211 as a permanent working tool. It is configured so that it can be used. Here, an example in which the earth auger 136 is attached to the hydraulic excavator by replacing it with the bucket 211 is shown. The earth auger 136 is an attachment that is attached to the front end of the bucket cylinder 13 or the arm 213 in the vertical direction to excavate a vertical hole in the ground. The earth auger 136 is rotated and lowered to form a hole in a natural ground, an auger screw 136a for rotating the auger screw 136a, and an auger screw 136a for vertically guiding the auger screw 136a. A reader 136c. When excavating a vertical hole in the ground, it is required to accurately determine the tip position and posture of the auger screw 136a and then proceed with the excavation of the vertical hole so that the position and posture do not fluctuate.

  Next, a conventional hydraulic drive circuit for a construction machine that can be applied to this type of excavator will be described with reference to FIGS.

  In these figures, reference numerals 1 and 2 denote variable displacement hydraulic pumps that are driven by an engine (not shown) and generate pressure oil for driving various hydraulic actuators of a hydraulic excavator such as a bucket cylinder 13 and an arm cylinder 15. 2A is a swash plate as a displacement displacement mechanism provided in each of these hydraulic pumps 1 and 2, 28 and 29 are regulators for controlling the tilting of these swash plates 1A and 2A, and 3 is a reservoir for hydraulic oil. Hydraulic oil tanks 4, 4 and 5 are center bypass pipes for supplying the hydraulic oil generated by the hydraulic pumps 1 and 2 to various hydraulic actuators of the hydraulic excavator, and 6 is provided in the left center bypass pipe 4 It is the 1st directional control valve group which consists of various directional control valves (direction switching valve).

  The center bypass pipeline 4 and the center bypass pipeline 5 are provided with a throttle portion 24 and a throttle portion 25 on the downstream side of the first directional control valve group 6 and a second directional control valve group 16 described later. A control pressure as a pressure signal is generated upstream of the throttle portions 24 and 25 by pressure oil flowing through the center bypass pipes 4 and 5. The control pressures generated on the upstream side of the throttle portions 24 and 25 are guided to the regulators 28 and 29 through the signal lines 26 and 27, respectively, and the swash plates 1A and 2A are tilted through the regulators 28 and 29, respectively. Control each one.

  For example, when all of the directional control valves in the first directional control valve group 6 are operated to the neutral position and the control pressure of the signal line 26 increases to the vicinity of the set pressure of the overload relief valve 38, the increased control pressure Is guided to the regulator 28 to control the tilt of the swash plate 1A so that the discharge capacity of the hydraulic pump 1 is minimized. Further, when any one of the directional control valves in the first directional control valve group 6 is switched from the neutral position to any one of the left and right positions, and the control pressure of the signal line 26 decreases, the degree of the decrease in the control pressure Accordingly, the tilt of the swash plate 1A is controlled by the regulator 28 so as to increase the discharge capacity of the hydraulic pump 1. The control of the swash plate 2A of the hydraulic pump 2 by the regulator 29 based on the control pressure of the signal line 27 is performed by the same mechanism. In the example shown here, the first direction control valve group 6 includes the following direction control valves 7, 8, 9, 10 for controlling the left traveling motor 11, the bucket cylinder 13, the boom cylinder 14, and the arm cylinder 15. Consists of.

  7 is a directional control valve for left travel that controls the movement of the motor 11 by switching the flow and flow rate of pressure oil supplied from the hydraulic pump 1 to the left travel motor 11, and 8 is supplied from the hydraulic pump 1 to the bucket cylinder 13. A directional control valve for a bucket 9 that controls the movement of the cylinder 13 by switching the flow and flow rate of the pressurized oil, and the cylinder 9 switches the flow and flow rate of the pressure oil supplied from the hydraulic pump 1 to the boom cylinder 14. 14 is a direction control valve for the boom that controls the movement of the cylinder 15 by switching the flow and flow rate of the pressure oil supplied from the hydraulic pump 1 to the arm cylinder 15. is there.

  The directional control valve 7 for left travel is operated by an operation signal of the operation means (in the illustrated example, an operation signal based on hydraulic pilot pressure) is sent to either the left or right signal receiving portion so that the left or right position is shifted from the neutral position. Thus, the flow of the pressure oil of the hydraulic pump 1 supplied from the center bypass pipe 4 to the left travel motor 11 can be switched, and the travel motor 11 can be rotated in the desired direction. In that case, the rotational speed of the left traveling motor 11 can be controlled by adjusting the opening amount according to the operation amount of the operation means.

  The bucket direction control valve 8 is configured such that an operation signal is sent to either the left or right signal receiving portion according to the operation direction of the operation means to switch from the neutral position to either the left or right position, and to the left position. While supplying the pressure oil of the bypass line 4 to the bottom side of the bucket cylinder 13, the pressure oil of the rod side is discharged to the tank line 23, and thereby the bucket cylinder 13 can be extended. When switched to the right position, the pressure oil in the center bypass conduit 4 is supplied to the rod side of the bucket cylinder 13 and the pressure oil on the bottom side is discharged to the tank conduit 23, whereby the bucket The cylinder 13 can be reduced. In that case, the speed at which the bucket cylinder 13 expands and contracts can be controlled by adjusting the opening amount according to the operation amount of the operation means.

  When the boom direction control valve 9 is switched from the neutral position to either the left or right position according to the operation direction of the operation means, the operation signal is sent to either the left or right signal receiving portion, and the center is switched to the left position. While supplying the pressure oil of the bypass line 4 to the bottom side of the boom cylinder 14, the pressure oil of the rod side is discharged to the tank line 23, and thereby the boom cylinder 14 can be extended. When switched to the right position, the pressure oil in the center bypass conduit 4 is supplied to the rod side of the boom cylinder 14, and the pressure oil on the bottom side is discharged to the tank conduit 23. The cylinder 14 can be reduced. In that case, the speed at which the boom cylinder 14 expands and contracts can be controlled by adjusting the opening amount according to the operation amount of the operation means.

  The directional control valve 10 for the arm is configured such that when the operation signal is sent to either the left or right signal receiving portion according to the operation direction of the operating means and switched from the neutral position to either the left or right position and switched to the left position, While supplying the pressure oil of the bypass line 4 to the rod side of the arm cylinder 15, the pressure oil on the bottom side thereof is discharged to the tank line 23, whereby the arm cylinder 15 can be reduced. When switched to the right position, the pressure oil in the center bypass pipe 4 is supplied to the bottom side of the arm cylinder 15, and the pressure oil on the rod side is discharged to the tank pipe 23, whereby the arm The cylinder 15 can be extended. In that case, the speed at which the arm cylinder 15 expands and contracts can be controlled by adjusting the opening amount according to the operation amount of the operation means.

  11 is the left traveling motor described above that rotationally drives the left wheel 207a, 12 is the above-described turning motor that drives the turning frame 203 to turn, 13 is the bucket cylinder described above that drives the bucket 211 to rotate, 14 is a boom cylinder that drives the boom 212 to swing, 15 is an arm cylinder that is driven to swing the arm 213, and 16 is a variety of components provided in the right center bypass pipe 5. It is the 2nd direction control valve group which consists of a direction control valve (direction switching valve). The second directional control valve group 16 includes directional control valves 17 to 21 described below.

  Reference numeral 17 denotes a directional control valve for a swing motor that controls the movement of the motor 12 by switching the flow and flow rate of pressure oil supplied from the hydraulic pump 2 to the swing motor 12, and 18 is supplied from the hydraulic pump 2 to the arm cylinder 15. A directional control valve 19 for the arm that controls the movement of the cylinder 15 by switching the flow and flow rate of the pressure oil, and the cylinder 14 by switching the flow and flow rate of the pressure oil supplied from the hydraulic pump 2 to the boom cylinder 14. A direction control valve for a boom that controls the movement of the boom, 20 is a spare direction control valve that controls the movement of a hydraulic actuator that drives a special working tool as an attachment, and 21 is supplied from the hydraulic pump 2 to the right travel motor 22. A directional control valve for right travel that controls the movement of the motor 22 by switching the flow and flow rate of the pressure oil, and 22 is a motor that rotates the right wheel 207a. Right traveling motor, 23 is a tank line for returning the hydraulic fluid of the center bypass line 4, 5 to the hydraulic oil tank 3.

  In the direction control valve 17 for the swing motor, an operation signal is sent to either the left or right signal receiving portion according to the operation direction of the operation means, and is switched from the neutral position to either the left or right position. Thus, the flow of the pressure oil of the hydraulic pump 2 supplied to the swing motor 12 can be switched to rotate the swing motor 12 in a desired direction. In that case, the rotational speed of the swing motor 12 can be controlled by adjusting the opening amount according to the operation amount of the operation means.

  The arm direction control valve 18 is switched from the neutral position to either the left or right position in conjunction with the operation of the arm direction control valve 10 by the operating means. The flow of the pressure oil supplied to the hydraulic pump 2 is switched, but its action is the same as that of the directional control valve 10 for the arm. The boom direction control valve 19 is switched from the neutral position to either the left or right position in conjunction with the operation of the boom direction control valve 9 by the operating means, whereby the hydraulic pump supplied to the boom cylinder 14. The flow of the pressure oil 2 is switched, but the action is not different from the action of the boom direction control valve 9. Therefore, the boom cylinder 14 and the arm cylinder 15 can be expanded and contracted at a desired speed by simultaneously supplying the pressure oil of the hydraulic pump 1 and the hydraulic pump 2.

  The directional control valve 21 for right travel is switched from the neutral position to either the left or right position by sending an operation signal to either the left or right signal receiving portion depending on the operation direction of the operation means. Thus, the flow of the pressure oil of the hydraulic pump 2 supplied to the right traveling motor 22 can be switched to rotate the traveling motor 22 in a desired direction. In that case, the rotational speed of the right traveling motor 22 can be controlled by adjusting the opening amount according to the operation amount of the operation means. The spare direction control valve 20 will be described in detail later.

  The directional control valves 7 to 10 constituting the first directional control valve group 6 are configured as multiple valves composed of tandem circuits connected in series with each other. Similarly, the directional control valves 17 to 21 forming the second directional control valve group 16 are also configured as multiple valves composed of tandem circuits connected in series with each other. Therefore, when these directional control valves 7 to 10 and the directional control valves 17 to 21 are operated to the neutral position, the hydraulic oil of the hydraulic pump 1 and the hydraulic pump 2 are supplied to the center bypass passage 4 and the center bypass passage 5 respectively. It can be circulated downstream and returned to the hydraulic oil tank 3 via the tank line 23.

  When the bucket direction control valve 8, the boom direction control valves 9, 19 and the arm direction control valves 10, 18 are in the neutral position, the bucket cylinder 13 holds the attitude of the bucket 211 as a work tool. A holding pressure is generated by pressure oil for the purpose, and the boom cylinder 14 and the arm cylinder 15 generate a holding pressure for holding the posture of the boom 212 and the arm 213 as work arms. Now, assuming that the bucket cylinder 13, the boom cylinder 14, and the arm cylinder 15 are installed in the manner shown in FIG. 4, the bucket cylinder 13 rod side, the boom cylinder 14 bottom side, and the arm cylinder 15 rod side. In this case, a holding pressure sufficient to balance the weight of the front 210 is generated, and the postures of the bucket 211, the boom 212, and the arm 213 are held, respectively. Maintaining the posture of the work tool and the work arm in this way is particularly important when performing work with a fixed position-type special work tool that performs work with the position fixed. .

  As already described, the bucket cylinder 13 is provided with a special work tool such as an earth drill 136 as an attachment or a crusher 36 (see FIGS. 5 and 6) instead of the bucket 211 as a permanent work tool. Since it can be used, items related to these will be described next. Here, the case where the crusher 36 is attached to the bucket cylinder 13 as a special working tool will be described as an example.

  Reference numeral 30 denotes a merging function that supplies the pressure oil of the center bypass pipe 4 to the pressure oil inflow port 20A of the auxiliary directional control valve 20 and merges the pressure oil of the hydraulic pumps 1 and 2 on the inflow side of the directional control valve 20. A switching valve 31 is a merging pipe that guides the pressure oil in the center bypass pipe 4 to the pressure oil inflow port 20A of the auxiliary directional control valve 20, and 32 is a pressure oil that is led to the pressure oil inflow port 20A through the merging pipe 31. A check valve 33 for preventing the reverse flow of the directional control valve 33. By operating the operation lever 33A, the pilot pressure is sent to the left or right signal receiving portion of the auxiliary directional control valve 20 through the pilot lines 34A, 34B, and the directional control valve 20 Is a control valve as an operation means for switching from (b) position (neutral position) to (b) position (left position) or (c) position (right position), and 36 is crushing for crushing buildings, etc. Machine 37 is a crusher driving cylinder as an actuator for driving the crusher 36.

  The junction switching valve 30 is disposed between the arm direction control valve 10 and the throttle portion 24. This merging switching valve 30 is normally switched to the position (a) (right position) by a spring force, and the hydraulic oil tank 3 supplies the pressure oil in the center bypass line 4 from the hydraulic pump 1 through the tank line 23. To be able to reflux. When a pilot pressure is applied to the left signal receiving portion through the pilot line 70, the pressure oil in the center bypass line 4 is introduced into the tank line 23 by switching to the position (b) (left position). Thus, the pressure oil in the center bypass pipe 4 is introduced into the merging pipe 31. Such switching of the merging switching valve 30 to the (b) position is achieved by switching an additional switching valve 63 (to be described later) to the (B) position (left position) when the auxiliary directional control valve 20 is switched to the (B) position (left position). Or (c) At any time when switching to the position (right position), pilot pressure is introduced into the pilot line 70.

  The crusher 36 is attached to the front end side of the arm 213 by exchanging it with the bucket 211, and the crusher driving cylinder 37 as a hydraulic actuator of the crusher 36 is controlled by the spare direction control valve 20. An operation such as gripping the object to be dismantled at the time of dismantling work or crushing the object with the gripping force of the crusher 36 is performed. This crusher 36, when crushing only a specific part of the construction object in a limited manner, does not crush to an unnecessary part so that the position and orientation are accurately determined and not changed in the same manner as the earth drill 136. It is necessary to be. The crusher driving cylinder 37 is a relatively short hydraulic cylinder for generating a gripping force in the crusher 36, and its movement is controlled by switching the spare direction control valve 20. When the crusher driving cylinder 37 is to be used, it is connected to the spare direction control valve 20 via a separate hydraulic line.

  The spare directional control valve 20 is operated to operate the operation valve 33 so that pilot pressure as an operation signal is sent to either the left or right signal receiving portion via the pilot pipes 34A and 34B, and is thereby switched to the (B) position. Sometimes, the pressure oil of the center bypass pipe 5 and the pressure oil of the center bypass pipe 4 joined to the center bypass pipe 5 through the merge pipe 31 are supplied to the bottom side of the crusher driving cylinder 37, and The pressure oil on the rod side is discharged to the tank pipe line 23, whereby the crusher driving cylinder 37 is extended to generate a strong gripping force on the crusher 36. When the position is switched to the position (c), the pressure oil in the center bypass line 5 is supplied to the rod side of the crusher driving cylinder 37 and the pressure oil on the bottom side is discharged to the tank line 23. Thus, the crusher driving cylinder 37 is reduced and the crusher 36 is expanded.

  When the crusher 36 switches the spare directional control valve 20 to the (B) position to generate a gripping force on the crusher 36, a large load pressure (actuator for accomplishing the work) The hydraulic pressure that is required to be applied to (3) is required, and such a large load pressure is not required when switching to the (c) position for expansion. Therefore, only when the pilot pressure is sent to the pilot line 34A to switch the spare directional control valve 20 to the (B) position, the pilot pressure is passed through the pilot line 68, the shuttle valve 69 and the pilot line 70. By guiding to the left signal receiving portion of the merging switching valve 30, the merging switching valve 30 is switched to the position (b), and the pressure oil of the hydraulic pumps 1 and 2 is merged on the inflow side of the spare directional control valve 20. To be able to. Here, an example in which the crusher 36 is used as an attachment is shown, but the above-described earth drill 136 that requires a large load pressure is used to drive the auger hydraulic motor 136b with the spare directional control valve 20. It can also be controlled.

  When the crusher 36 is used, it is necessary to position the crusher 36 by rotating it, or to apply a twisting force to the crushing object gripped by the crusher 36. In order to perform such an operation, in the example shown here, a crusher hydraulic motor 41 is provided as an additional hydraulic actuator. Therefore, the matters related to this will be outlined.

  41 is a hydraulic motor for a crusher as an additional hydraulic actuator, 61 is a hydraulic pump for the center bypass pipe 4 branched from the center bypass pipe 4 at a connection point 61A between the direction control valve 10 for the arm and the junction switching valve 30. The pressure oil introduction pipe 62 that introduces one pressure oil into the pressure oil inflow port 63A of the additional directional control valve 63, and the pressure oil led to the pressure oil inflow port 63A through the pressure oil introduction pipe 61 flows back. The check valve 63 is an additional directional control valve that controls the movement of the hydraulic motor 41 by switching the flow and flow rate of the pressure oil supplied from the pressure oil introduction pipe 61 to the hydraulic motor 41 for the crusher. is there.

  64 outputs pilot pressure through pilot pipes 65A and 65B to the right and left signal receiving portions of the additional directional control valve 63 by operating the operation lever 64A, and moves the directional control valve 63 to the (a) position (neutral position). ) To (b) position (left position) or (c) position (right position) as an operation means for switching, 66 is the pilot pressure of the higher one of the pilot pressures of the pilot lines 65A and 65B Is a shuttle valve that leads to the pilot line 67 and 69 is a shuttle valve that selects the higher pilot pressure of the pilot pressures of the pilot lines 67 and 68 and leads it to the pilot line 70. The pilot pressure of one of the pilot lines 67 and 68 selected by the valve 69 is led to the signal receiving portion on the left side of the merging switching valve 30, and this is switched to the position (b). A pilot line for introducing a hydraulic fluid of the center bypass line 4 the confluence pipe 31 and the pressure oil inlet conduit 61.

  In the hydraulic drive circuit according to the conventional construction machine as described above, the directional control valve 8 for the bucket, the directional control valves 9 and 19 for the boom, and the directional control valves 10 and 18 for the arms are in the neutral position. In the state shown in the figure, by outputting pilot pressure to the pilot pipe line 34A, the auxiliary directional control valve 20 is switched to the (B) position, and this is driven so as to generate a gripping force in the crusher driving cylinder 37. Then, the pilot pressure in the pilot line 34A is also guided to the left signal receiving portion of the merging switching valve 30 through the pilot line 68, the shuttle valve 69, and the pilot pipe 70, and the merging switching valve 30 is moved to the position (b). Switch. Then, since the center bypass pipe 4 is closed at the downstream side of the arm direction control valve 10 by the merging switching valve 30, the pressure oil of the hydraulic pump 1 is sent to the merging pipe 31 to be reserved. On the inflow side of the directional control valve 20, the pressure oil of the hydraulic pump 2 in the center bypass pipe 5 is joined.

Therefore, the crusher driving cylinder 37 can be driven by a large load pressure.
At this time, the tilt of the swash plates 1A and 2A is controlled through the regulators 28 and 29 by the control pressure generated in the signal lines 26 and 27, and the hydraulic pumps 1 and 2 are discharged according to the magnitude of the load pressure. Since the control is performed so as to increase the capacity, the hydraulic pressures of the center bypass pipelines 4 and 5 both increase. As a result, the center bypass in the region where the directional control valve 8 for the bucket, the directional control valves 9 and 19 for the boom, and the directional control valves 10 and 18 for the arm located upstream of the crusher driving cylinder 37 are provided. The hydraulic pressure in the pipelines 4 and 5 also rises rapidly. When the merging switching valve 30 is switched to the position (b) as described above, the pressure oil in the center bypass pipe 4 is also introduced into the pressure oil introduction pipe 61, so a crusher hydraulic motor 41 is added. It is also possible to drive with pressure oil in the center bypass line 4 while being controlled by the direction control valve 63.

  For the convenience of explanation of the technical problem of the present invention to be described later, the actual structure of the directional control valve will be described. Here, based on FIG. 7, the directional control valve 150 of the same system as the directional control valves 8, 9, 19, 10, and 18 for controlling the drive of the hydraulic cylinder will be described.

  As shown in FIG. 7, the direction control valve 150 is roughly divided into a valve main body (casing) 151 having a fitting hole 151a therein, and a spool 152 slidably fitted into the fitting hole 151a of the valve main body 151. It consists of The valve body 151 includes an inflow port (pump side port) 151b for introducing hydraulic pressure of the hydraulic pump, a bottom port 151c communicating with the bottom side of the hydraulic cylinder, and a rod communicating with the rod side of the hydraulic cylinder. Side port 151d. The spool 152 has a plurality of circular partition-like lands 152a for allowing or blocking the pressure oil introduced into the pump-side port 151b from flowing into the bottom-side port 151c or the rod-side port 151d. Is protruding.

FIG. 7 shows a state where the spool 152 is operated to the neutral position. Since the directional control valve 150 has the above-described structure, when the spool 152 is in such a neutral position, the pressure oil in the vicinity of the pump-side port 151b is theoretically converted to the bottom-side port 151c and the rod-side. Should not flow into port 151d. However, there is a gap between the inner peripheral surface of the fitting hole 151a of the valve body 151 and the outer peripheral surface of the spool 152 so that the spool 152 can be smoothly slid. When the hydraulic pressure of the passages 4 and 5 becomes high, the pressure oil in the vicinity of the pump-side port 151b actually passes through the gap as shown by arrows X and Y, and the bottom-side port 151c and the rod-side Leaks to both ports 151d.
JP-A-11-230112 (page 2-10, FIG. 1-2)

  In the conventional construction machine having the hydraulic drive circuit as described above, when the construction work is performed by a special work tool such as the crusher 36 or the earth auger 136 as an attachment, the special work tool is connected to the distal end side of the arm 213. At the same time, the bucket 211 is replaced and attached to the bucket cylinder 13. Further, hydraulic actuators for driving work tools such as the crusher driving cylinder 37 and the auger hydraulic motor 136 b are installed so that they can be controlled by the spare direction control valve 20. Next, the bucket cylinder 13, the boom cylinder 14 and the arm cylinder 15 are appropriately driven to accurately determine the position and posture of the special work tool. In this state, since the bucket direction control valve 8, the boom direction control valves 9, 19 and the arm direction control valves 10, 18 are in the neutral position, the bucket cylinder 13 on the rod side and the boom cylinder 14 on the bottom side. Also, holding pressure sufficient to balance the weight of the front 210 is generated on the rod side of the arm cylinder, and the postures of the bucket 211, the boom 212, and the arm 213 are held, respectively, and the position and posture of the special work tool fluctuate. Never do.

  After the preparation is completed, when the hydraulic actuator for driving the work implement is driven, this type of hydraulic actuator requires a large load pressure. Therefore, the hydraulic pumps 1 and 2 increase the discharge capacity according to the increase in the load pressure. The tilt of the swash plates 1A and 2A is controlled so as to increase, and as a result, the hydraulic pressure of the center bypass pipes 4 and 5 also increases. Then, the pressure oil in the vicinity of the pump side port in the bucket direction control valve 8, the boom direction control valves 9 and 19 and the arm direction control valves 10 and 18 leaks to the bottom side port and the rod side port. The leaked pressure oil enters the bottom side and the rod side of the bucket cylinder 13, the boom cylinder 14 and the arm cylinder 15.

  When the leaked pressure oil enters the hydraulic cylinders 13, 14, 15, the hydraulic cylinders 13, 14, 15 have a larger cross-sectional area in the bottom side space than the cross-sectional area in the rod side space. The hydraulic cylinders 13, 14, and 15 are extended by the pressure of. That is, the bucket cylinder 13, the boom cylinder 14, and the arm cylinder 15 are extended, and the position and posture of a special work tool as an attachment are changed. As a result, the construction accuracy of the construction work to be performed with the special work tool is lowered. Particularly, when the special work tool is a long one such as the earth auger 136, a connecting shaft or the like that is added to the auger screw 136a or the like. The long tool may be damaged.

  The present invention was created in order to solve the problems found in the prior art, and the technical problem is that a permanent work tool that replaces a special work tool that requires a large load pressure for driving with a permanent work tool is provided. An object of the present invention is to provide a construction machine capable of suppressing fluctuations in the position and posture of a work tool when a special work tool is driven, even when attached to a hydraulic cylinder.

In order to achieve the above technical problem, the present invention
Permanent work tool that performs construction work such as excavation work, and permanent work tool that drives the permanent work tool and generates a holding pressure on one of the bottom side and the rod side when driving is stopped to maintain the posture of the work tool A hydraulic cylinder for the working tool, a directional control valve for the permanent working tool for controlling the movement of the hydraulic cylinder for the working tool, at least one swingable working arm for supporting the permanent working tool, and the working arm. A hydraulic cylinder for the working arm that holds the working arm posture by generating a holding pressure on one of the bottom side and the rod side when the drive is stopped and controlling the movement of the hydraulic cylinder for the working arm. In a construction machine comprising a directional control valve for a working arm that is configured to be used by attaching a special working tool as an attachment to a hydraulic cylinder for a permanent working tool, instead of a permanent working tool,
For the working arm, a connecting oil passage that connects the other of the bottom side and the rod side of the hydraulic cylinder for the permanent working tool and the direction control valve for the permanent working tool, and the other of the bottom side and the rod side of the hydraulic cylinder for the working arm. A pressure relief circuit is provided in at least one of the connecting oil passages for connecting the directional control valve to the pressure oil in the connecting oil passage to the hydraulic oil tank when the special working tool is used.

  In such a construction machine, when a construction work is performed using a special working tool such as a crusher or an earth auger as an attachment, the special working tool is first attached to a hydraulic cylinder for the permanent working tool instead of the permanent working tool. Thereafter, the hydraulic cylinder for the permanent working tool and the hydraulic cylinder for the working arm are driven appropriately by operating the directional control valve for the permanent working tool and the directional control valve for the working arm, respectively. Determine posture accurately. Thereafter, by switching these directional control valves to the neutral position, the posture of the special work tool is held by the holding pressure generated in the hydraulic cylinder for the permanent work tool and the hydraulic cylinder for the work arm. Next, the special work tool is driven to perform construction work.

  At this time, in a conventional construction machine, when a large load pressure is applied and driven, the pressure oil on each inflow port side of the directional control valve for the permanent work tool and the directional control valve for the working arm is in these directions. It leaks to the port on each bottom side and each rod side of the control valve. As a result, the leaked pressure oil enters the bottom side and the rod side of the hydraulic cylinder for the working tool and the hydraulic cylinder for the working arm, respectively, and is generated due to the difference in cross-sectional area between the bottom side space and the rod side space. Since these hydraulic cylinders extend due to the differential pressure, the position and posture of the special work tool as an attachment vary.

  On the other hand, in the construction machine of the present invention, since the pressure relief circuit is provided in the above-described manner, the connection oil passage provided with the pressure relief circuit is kept at a low pressure when the special work tool is used. When the pressure oil on each inflow port side of the directional control valve for the tool and the directional control valve for the work arm is about to leak to the bottom side and the rod side ports of these directional control valves, Of the ports on the rod side, leakage tends to occur toward the port connected to the connecting oil passage maintained at a low pressure. As a result, in a hydraulic cylinder for a permanent working tool or a hydraulic cylinder for a working arm that is connected to a connecting oil passage that is maintained at a low pressure, the pressure oil on the inflow port side is held on the bottom side and the rod side. Almost no penetration occurs on the side where the pressure is generated, and the posture of the special work tool or work arm is less likely to fluctuate.

  Therefore, according to the construction machine of the present invention, even if a special work tool that requires a large load pressure for driving is attached to the hydraulic cylinder for the permanent work tool instead of the permanent work tool, It is possible to prevent the position and posture of the work tool from changing during driving.

  As will be apparent from the following description, the construction machine of the present invention is constructed as shown in the above-mentioned section [Means for Solving the Problems]. Even if it is attached to a hydraulic cylinder for a permanent work tool in place of the permanent work tool, the position and posture of the work tool can be prevented from changing when the special work tool is driven. As a result, when performing construction work with special work tools, the risk of lowering work accuracy and damaging the tools of special work tools is significantly reduced compared to conventional construction machines. Can do.

  When the construction machine of the present invention is embodied, particularly if embodied as in claim 2 of the claims, the pressure relief circuit can be made to function only when necessary, When the pressure release circuit such as excavation work by the work tool functions, inconvenient construction work can be performed smoothly, and a highly versatile construction machine can be obtained. When the construction machine of the present invention is embodied, particularly when embodied as described in claim 3 of the scope of claims, the same effect can be obtained.

  In particular, when embodied as described in claim 2 of the scope of claims, a special valve such as a switching valve for opening and closing the pressure relief circuit and a signal path for sending an operation signal to the switching valve. Even if a control part is not provided, the depressurization circuit can function alone when necessary. And since such performance can be added by a simple structure of providing a restriction on the pressure release circuit, the structure related to the pressure release circuit can be configured to be less likely to fail and manufactured at low cost. Can do. When the construction machine of the present invention is embodied, in particular, as embodied in claim 5 of the claims, the direction control valve for the existing special work tool is added to the signal of the drive start detecting means. As a result, it is possible to add the performance of functioning the depressurization circuit only when necessary to a ready-made construction machine without major modification.

  Hereinafter, how the present invention is actually embodied will be described with reference to FIGS. 1 to 3 to clarify a desirable mode for carrying out the present invention.

  FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive circuit according to a construction machine of a first example embodying the present invention, and FIG. 2 is a diagram showing a hydraulic drive circuit according to a construction machine of a second example. FIG. 3 is a hydraulic circuit diagram similar to FIG. 1 showing a hydraulic drive circuit according to the construction machine of the third example. In these drawings, the portions denoted by the same reference numerals as those in FIGS. 4 to 6 described above represent the same portions as those in FIGS. 4 to 6 and will not be described in detail. These drawings show an example in which the construction machine is a self-propelled hydraulic excavator as in the conventional construction machine.

  The construction machine described below is similar to the conventional construction machine already described. The bucket 211 is a permanent work tool for performing construction work such as excavation work, and the bottom side and the rod side are driven when the bucket 211 is driven to stop driving. A bucket cylinder 13 as a hydraulic cylinder for a permanent working tool that generates a holding pressure on one side and holds the posture of the bucket 211, and a bucket as a directional control valve for a permanent working tool that controls the movement of the bucket cylinder 13 The direction control valve 8 is provided. In addition, as in the conventional construction machine, the boom 212 and the arm 213 as swingable working arms that support the bucket 211, and the bottom side and the rod when the boom 212 and the arm 213 are driven to swing and stop driving. Boom cylinder 14 and arm cylinder 15 that generate holding pressure on one side to maintain the posture of the boom 212 and arm 213, and a directional control valve for the working arm that controls the movement of the boom cylinder 14 and arm cylinder 15 The boom direction control valves 9 and 19 and the arm direction control valves 10 and 18 are provided. Then, instead of the bucket 211 as a permanent work tool, a special work tool such as a crusher or an earth auger as an attachment can be attached to the bucket cylinder 13 and used, and a structure serving as a base Is no different from conventional construction machinery.

  The hydraulic drive circuit of FIGS. 1 to 3 relating to a construction machine embodying the present invention is the bottom side and the rod side of the hydraulic cylinder (bucket cylinder 13) for permanent work tools in the construction machine. A special working tool (crusher 36) is connected to a connecting oil passage 83 that connects a chamber on the opposite side to the side where the holding pressure is generated and a directional control valve for a permanent working tool (bucket directional control valve 8). Is provided with a pressure relief circuit 103 that allows the hydraulic oil in the connecting oil passage 83 to escape to the hydraulic oil tank. Similarly, the chamber on the opposite side of the bottom side and the rod side of the hydraulic cylinder for the working arm (the boom cylinder 14 and the arm cylinder 15) and the rod generating side, and the direction control valve for the working arm (for the boom) In the connecting oil passages 84 and 85 for connecting the directional control valves 9 and 19 and the arm directional control valves 10 and 18), similar pressure release circuits 104 and 105 are provided, respectively. The hydraulic drive circuit has the greatest feature in this respect.

  As can be seen from FIG. 4, in the example shown here, the holding pressure is generated on the rod side in the bucket cylinder 13, on the bottom side in the boom cylinder 14, and on the rod side in the arm cylinder 15. The opposite side is the bottom side in the bucket cylinder 13 and the arm cylinder 15 and the rod side in the boom cylinder 14. Therefore, the connecting oil passage 83 connects the bottom side of the bucket cylinder 13 and the bottom side port of the directional control valve 8 for the bucket, and is provided with a pressure relief circuit 103. The connecting oil passage 84 is connected to the boom. A pressure relief circuit 104 is provided by connecting the rod side of the cylinder 14 and the port on the rod side of the direction control valves 9 and 19 for the boom, and the connecting oil passage 85 is connected to the bottom side of the arm cylinder 15 and the arm. A pressure relief circuit 105 is provided by connecting the bottom side ports of the directional control valves 10 and 18 for use.

  The holding pressure of the bucket cylinder 13 and the arm cylinder 15 is a force that prevents the cylinders 13 and 15 from extending due to the weight of the front 210, and the holding pressure of the boom cylinder 14 is the same as that of the front 210. It is a force that prevents trying to shrink due to weight. Therefore, in FIG. 4, even if these cylinders 13, 14, 15 are arranged so that the bottom side and the rod side are opposite to those shown in the figure, the holding pressure of each of the cylinders 13, 14, 15 is It occurs on the same side as the example of FIG. 4 on the bottom side and the rod side.

  In the hydraulic drive circuit of FIG. 1 relating to the construction machine of the first example that is embodied by embodying the present invention, driving of the crusher 36 as a special working tool is started using the pressure release circuits 103, 104, 105. It is made to open based on the signal of the drive start detection means for detecting this. For this reason, the pressure relief circuits 103, 104, 105 are provided with a normally closed electromagnetic switching valve 101 for opening and closing the circuits 103, 104, 105, and work for the operator to switch when working with the crusher 36. A mode changeover switch 102 is provided. When the operation mode changeover switch 102 is switched to the operation mode by the crusher 36 using the operation mode changeover switch 102 as a drive start detection means, the electromagnetic changeover is performed based on the operation signal. The valve 101 is switched from the closed position to the open position.

  The electromagnetic switching valve 101 in FIG. 1 is switched to the right position shown in the figure when the work mode changeover switch 102 is switched to a work mode other than the work mode by the crusher 36, and the pressure release circuits 103 and 104. , 105 are closed. When the work mode changeover switch 102 is switched to the mode of work by the crusher 36, the operation signal of the work mode changeover switch 102 is sent as an electric signal to the left signal receiving portion of the electromagnetic changeover valve 101, and electromagnetic The switching valve 101 is switched to the left position, thereby opening all of the pressure relief circuits 103, 104, and 105. As a result, the bottom side of the bucket cylinder 13 and the arm cylinder 15 and the rod side of the boom cylinder 14, that is, the side opposite to the side that generates the holding pressure in the hydraulic cylinder are connected to the hydraulic oil tank 3.

  In a construction machine equipped with such a hydraulic drive circuit, when construction work is performed by a crusher 36 that is a special work tool, first, the crusher 36 is replaced with a bucket 211 that is a permanent work tool, and a bucket cylinder 13 and an arm. After attaching the crusher driving cylinder 37 to the spare directional control valve 20 through a hydraulic line, the bucket cylinder 13, the boom cylinder 14 and the arm cylinder 15 are respectively connected to the bucket directional control valve. 8. By appropriately operating the direction control valves 9 and 19 for the boom and the direction control valves 10 and 18 for the arm, the postures of the crusher 36, the boom 212 and the arm 213 are appropriately adjusted. The position and orientation of the crusher 36 can be adjusted so that necessary parts of the object can be gripped or crushed by the crusher 36. Stipulated in probability.

  Thereafter, by switching these directional control valves 8, 9, 19, 10, and 18 to the neutral position, the holding pressure generated on the rod side of the bucket cylinder 13 and the arm cylinder 15 and the bottom side of the boom cylinder 14 respectively. The position and posture of the crusher 36 are maintained. Next, the operation mode changeover switch 102 is switched to the operation mode by the crusher 36, thereby switching the electromagnetic switching valve 101 to the left position and opening the pressure release circuits 103, 104, 105, and then for crusher driving. The cylinder 37 is driven and the desired construction work is performed by the crusher 36.

  By the way, in the conventional construction machine, when a large load pressure is applied to drive the crusher driving cylinder 37, the bucket direction control valve 8, the boom direction control valves 9, 19 and the arm Pressure oil on the inflow port side of the direction control valves 10 and 18 leaks to the bottom side and rod side ports of the direction control valves 8, 9, 19, 10 and 18. As a result, the leaked pressure oil enters the bottom side and the rod side of the bucket cylinder 13, the boom cylinder 14 and the arm cylinder 15, respectively, and the differential pressure generated due to the difference in cross-sectional area between the bottom side space and the rod side space As a result, the bucket cylinder 13, the boom cylinder 14 and the arm cylinder 15 extend, so that the position and posture of the crusher 36 change. If the position and orientation of the crusher 36 change in this way, there is a risk of crushing to a part that does not need to be crushed when only a specific part of the construction target is crushed, and Convenience is not good.

  On the other hand, in this construction machine, the pressure relief circuits 103, 104, 105 are provided and opened when the crusher 36 is operated, so that the connecting oil passages 83, 84, 85 are connected to the pressure relief circuits 103, 104. , 105 communicates with the hydraulic oil tank 3 and is kept at a low pressure. Accordingly, along with this, the bottom side ports of the bucket direction control valve 8 and the arm direction control valves 10 and 18 and the rod side ports of the boom direction control valves 9 and 19 are also kept at a low pressure. It is. Therefore, the pressure oil leaking to the bottom side and rod side ports of the direction control valves 8, 9, 19, 10, and 18 is kept at a low pressure for the bucket direction control valve 8 and the arm direction control. The bucket cylinder 13 and the arm that generate the holding pressure as a result of extremely easy leakage to the bottom side ports of the valves 10 and 18 and the rod side ports of the directional control valves 9 and 19 for the boom. It is almost impossible to enter the rod side of the cylinder 15 and the bottom side of the boom cylinder 14. Since this construction machine has such an action, the postures of the crusher 36, the boom 212, and the arm 213 are not easily changed.

  Here, an example in which the crusher 36 is used as a special work tool has been described. However, another special work tool such as the earth auger 136 in FIG. 4 is used, and this is replaced with the bucket 211 and the bucket cylinder 13. Even when attached to the front end of the arm 213 and driven, the same function as described above can be exhibited. Therefore, according to the present construction machine, the permanent work such as the bucket cylinder 13 is replaced with the special work tool such as the crusher 36 and the earth auger 136 that require a large load pressure for driving instead of the permanent work tool such as the bucket 211. Even if the tool is attached to a hydraulic cylinder for tools, the position and posture of the tool can be prevented from changing when the special tool is driven. As a result, when performing construction work with special work tools, the risk of lowering work accuracy and damaging the tools of special work tools is significantly reduced compared to conventional construction machines. Can do.

  In this construction machine, the pressure release circuits 103, 104, and 105 are switched to a signal of a drive start detecting means for detecting that the crusher 36 has started to be driven, that is, when the crusher 36 is operated. Since the opening is made based on the operation signal of the changeover switch 102, the pressure relief circuits 103, 104, 105 can be made to function only when necessary. Therefore, when the pressure release circuits 103, 104, and 105 such as excavation work by the bucket 211 function, it is possible to smoothly carry out inconvenient construction work, and a highly versatile construction machine can be obtained. The pressure oil on the opposite side of the holding pressure generating side of the bottom side and the rod side of the bucket cylinder 13, boom cylinder 14, and arm cylinder 15 is communicated with the hydraulic oil tank 3 through the pressure release circuits 103, 104, 105. However, since the holding pressures of these hydraulic cylinders 13, 14, and 15 are balanced with the weight of the front 210, the postures of the bucket 211, the boom 212, and the arm 213 do not change.

  In the hydraulic drive circuit of FIG. 2 according to the construction machine of the second example which is configured by embodying the present invention, the depressurization circuits 103, 104, and 105 are driven by the crusher 36 as in the hydraulic drive circuit of FIG. Is opened based on the signal of the drive start detection means for detecting that the operation has started. For this purpose, the pressure relief circuits 103, 104, 105 are provided with a normally closed hydraulic pilot operation type switching valve 108 for opening and closing the circuits 103, 104, 105, and the spare direction control valve 20 is switched. A pilot pressure as an operation signal for operation is used as a signal of the drive start detection means, and the switching valve 101 is switched from the closed position to the open position based on the operation signal based on the pilot pressure.

  In order to realize this, the pilot branch pipelines 34A 'and 34B' branching from the pilot pipelines 34A and 34B, respectively, and the higher pilot pressure of these pilot branch pipelines 34A 'and 34B' are selected. And a pilot valve 106 for guiding the pilot pressure of any one of the pilot branch pipes 34A ′ and 34B ′ selected by the shuttle valve 106 to the left signal receiving portion of the switching valve 108. A pilot line 107 is provided. By such a hydraulic circuit, the pilot pressure output when the operation valve 33 is operated is guided from the pilot branch pipes 34A ′ and 34B ′ to the left signal receiving portion through the shuttle valve 106 and the pilot pipe 107, and the switching valve 108 is supplied. Is switched from the closed position to the open position.

  When the crusher driving cylinder 37 is not driven, the switching valve 108 in FIG. 2 is switched to the right position shown in the figure and closes all the pressure release circuits 103, 104, and 105. Further, when the pilot pressure is output by operating the operation valve 33 and the crusher driving cylinder 37 is driven, this pilot pressure is received from the pilot branch pipes 34A ′ and 34B ′ on the left side of the switching valve 108. The switching valve 108 is switched to the left position, thereby opening all of the pressure relief circuits 103, 104, and 105. As a result, the bottom side and the rod side of the bucket cylinder 13, boom cylinder 14, and arm cylinder 15 are connected to the hydraulic oil tank 3 on the side opposite to the side that generates the holding pressure.

  In the construction machine of the second example, the pressure release circuits 103, 104, and 105, which were performed by the switching operation of the work mode changeover switch 102 in the construction machine of the first example, are opened by operating the operation valve 33. In this respect, the construction machine is different from the construction machine of the first example. Except for this point, the same operational effects as those of the construction machine of the first example described above are obtained. In this construction machine, the operation signal for switching the existing spare directional control valve 20 can be used as it is as the signal of the drive start detection means for detecting that the crusher 36 has started to be driven. Therefore, it is possible to add performance that allows the depressurization circuits 103, 104, and 105 to function only when necessary without making major modifications to the ready-made construction machine.

  In the example shown here, an operation signal for switching the spare directional control valve 20 is used as a signal of the drive start detection means, but instead of this operation signal, crushing as an actuator of the crusher 36 is performed. The system shown in FIG. 2 utilizes the hydraulic pressure of a pair of connecting oil passages that connect the machine drive cylinder 37 and the spare direction control valve 20 for controlling the movement of the crusher drive cylinder 37 as signals of the drive start detection means. The signal can be sent to the signal receiving portion of the switching valve 108 according to the above. Even in such a configuration, when pressure oil is supplied to the crusher driving cylinder 37 from the spare direction control valve 20 by the operation of the operation valve 33 and driven, the connecting oil passage on the pressure oil supply side is driven. Pressure oil is sent to the left signal receiving portion of the switching valve 108 to switch the switching valve 108 to the left position, thereby opening all of the pressure relief circuits 103, 104, and 105. Therefore, even in this case, except for the point that the depressurization circuits 103, 104, and 105 are opened by operating the operation valve 33, the same effects as those of the construction machine of the first example described above are obtained. Play.

  The hydraulic drive circuit of FIG. 3 according to the construction machine of the third example embodying the present invention crushes the pressure oil of each of the connecting oil passages 83, 84, 85 into the connecting oil passages 83, 84, 85. 1 and 2 is common to the hydraulic drive circuit in that each of the pressure relief circuits 103, 104, and 105 that can be released to the hydraulic oil tank 3 when used is used. At times, the means for allowing the pressure oil in each of the connecting oil passages 83, 84, 85 to escape to the hydraulic oil tank 3 is completely different from the previous examples. That is, the hydraulic drive circuit of FIG. 3 does not include the drive start detection means in the example of FIGS. 1 and 2 that detects the start of driving of the crusher 36, and each pressure release circuit 103, 104, The oil passages 105 are respectively provided with throttles 109, 110, and 111, so that the hydraulic oil in each of the connecting oil passages 83, 84, and 85 is released to the hydraulic oil tank 3 when the crusher 36 is used.

  In the hydraulic drive circuit according to this construction machine, a large amount of pressure oil that can drive the hydraulic cylinders 13, 14, 15 flows into the upstream side of the throttles 109, 110, 111 in the pressure release circuits 103, 104, 105. In such a case, the hydraulic pressure can be raised upstream by the resistance of the throttles 109, 110, and 111, and when only a small amount of pressurized oil flows to the upstream side thereof, the pressurized oil is supplied to the throttles 109, 110, The hydraulic oil tank 3 can be smoothly released through 111. Accordingly, by appropriately selecting the cross-sectional areas of the flow paths of the throttles 109, 110, and 111, the bottom side of the bucket cylinder 13, the boom cylinder 14, and the arm cylinder 15 is used when a permanent work tool such as the bucket cylinder 13 is used. In addition, it is possible to smoothly implement even inconvenient construction work when pressure oil is supplied to the opposite side of the holding pressure generating side of the rod side and the pressure relief circuits 103, 104, 105 such as excavation work function. . Further, when a special working tool such as the crusher 36 is used, only a small amount of leaked pressure oil flows upstream of the throttles 109, 110, and 111, so that it can be smoothly released to the hydraulic oil tank 3. it can.

  Therefore, this construction machine also exhibits the same operational effects as those of the construction machine of the first example described above, except for the specific operational effects brought about by the apertures 109, 110, and 111. In addition, in the construction machine, when the depressurization circuits 103, 104, and 105 are configured, the crusher 36 is provided by providing the throttles 109, 110, and 111 in the oil passages of the depressurization circuits 103, 104, and 105, in particular. Since the pressure oil in the connecting oil passages 83, 84, 85 can be released to the hydraulic oil tank 3 during use, the switching valves 101, 108 for opening and closing the pressure relief circuits 103, 104, 105 are provided. In addition, the pressure relief circuits 103, 104, and 105 can be made to function independently only when necessary without providing special control parts such as signal paths for sending operation signals to the switching valves 101 and. it can. Such performance can be added by a simple structure in which the throttles 109, 110, and 111 are provided in the pressure relief circuits 103, 104, and 105. Therefore, the structure related to the pressure relief circuits 103, 104, and 105 is failed. It can be made difficult to manufacture and can be manufactured at low cost.

  In the example described above, the pressure relief circuits 103, 104, and 105 are provided in the connecting oil passages 83, 84, and 85, respectively. For example, the bottom side of the bucket cylinder 13 and the bucket that directly affect the posture of the crusher 36. Even if the depressurization circuit 103 is provided only in the connecting oil passage 83 that connects the directional control valve 8 for use, the effect of suppressing fluctuations in the position and posture of the crusher 36 is exhibited. And, it is a matter that should be selected in design, considering the work contents by the special work tool, etc., in which connection oil passage of this construction machine the pressure relief circuit of this kind is provided. In short, in consideration of the above, a connecting oil passage that connects the bottom side and the rod side of the hydraulic cylinder for the permanent working tool opposite to the holding pressure generating side and the direction control valve for the permanent working tool, and A pressure relief circuit is provided in at least one of the connecting oil passages that connects the working arm directional control valve to the opposite side of the holding pressure generating side of the bottom and rod sides of the hydraulic cylinder for the working arm. Just do it.

  In the example of FIG. 1, the work mode changeover switch 102 is provided for switching the electromagnetic switching valve 101, but this work mode changeover switch 102 is an operation for controlling the hydraulic pumps 1 and 2 according to the work mode. It can also be configured to be used as a switch. In the example of FIGS. 1 and 2, the pressure release circuits 103, 104, and 105 are simultaneously opened and closed by one electromagnetic switching valve 101 and switching valve 108, but the switching valve that opens and closes one oil passage is pressurized. It can also be provided in each of the extraction circuits 103, 104, and 105 so that the respective oil passages are individually opened and closed. In the example of FIG. 3, one throttle 109, 110, and 111 is provided in each oil passage of each of the pressure release circuits 103, 104, and 105. It can also be provided.

1 is a hydraulic circuit diagram showing a hydraulic drive circuit according to a construction machine of a first example embodying the present invention. It is the hydraulic circuit diagram similar to FIG. 1 which shows the hydraulic drive circuit which concerns on the construction machine of a 2nd example. It is the hydraulic circuit diagram similar to FIG. 1 which shows the hydraulic drive circuit which concerns on the construction machine of the 3rd example. It is a side view which shows an example of the conventional construction machine which enabled it to replace a special work tool with a permanent work tool, and to use it. It is a hydraulic circuit diagram which shows an example of the hydraulic drive circuit of the conventional construction machine applicable to the construction machine of FIG. FIG. 6 is an enlarged hydraulic circuit diagram showing a main part of the hydraulic circuit diagram of FIG. 5. It is a longitudinal cross-sectional view which shows the internal structure of the direction control valve for controlling the motion of various hydraulic cylinders.

Explanation of symbols

1, 2 (variable displacement type) hydraulic pump 3 Hydraulic oil tank 4, 5 Center bypass pipe 8 Direction control valve for bucket 9, 19 Direction control valve for boom 10, 18 Direction control valve for arm 13 Bucket cylinder 14 Boom cylinder 15 Arm cylinder 20 Spare direction control valve 30 Junction switching valve 33 Operation valve 34A, 34B Pilot pipe line 36 Crusher 37 Crusher drive cylinder 68, 70 Pilot pipe line 69 Shuttle valve 83, 84, 85 Connecting oil Path 101 Electromagnetic switching valve 102 Work mode switch 103, 104, 105 Pressure release circuit 106 Shuttle valve 107 Pilot line 108 (Hydraulic pilot operation type) switching valve 109, 110, 111 Restriction 136 Earth auger 136b Auger hydraulic motor 210 Front 211 Bucket 21 2 Boom 213 Arm

Claims (6)

  Permanent work tool that performs construction work such as excavation work, and permanent work tool that drives the permanent work tool and generates a holding pressure on one of the bottom side and the rod side when driving is stopped to maintain the posture of the work tool A hydraulic cylinder for the working tool, a directional control valve for the permanent working tool for controlling the movement of the hydraulic cylinder for the working tool, at least one swingable working arm for supporting the permanent working tool, and the working arm. The hydraulic cylinder for the working arm that holds the working arm posture by generating holding pressure on one of the bottom side and the rod side when the drive is stopped and controlling the movement of the hydraulic cylinder for the working arm. In a construction machine comprising a directional control valve for a working arm that is configured to be used by attaching a special working tool as an attachment to a hydraulic cylinder for a permanent working tool, instead of a permanent working tool, Permanent A connecting oil passage for connecting the other of the bottom side and the rod side of the hydraulic cylinder for the working tool and the direction control valve for the permanent working tool, and the other of the bottom side and the rod side of the hydraulic cylinder for the working arm and the working arm. A pressure relief circuit is provided in at least one connecting oil passage of the connecting oil passage connecting the direction control valve so that the pressure oil in the connecting oil passage can be released to the hydraulic oil tank when the special working tool is used. Construction machinery characterized by that.   2. The construction machine according to claim 1, wherein, when the pressure release circuit is configured, by providing a throttle in the oil passage of the pressure release circuit, the hydraulic oil in the connection oil passage is supplied to the hydraulic oil tank when a special work tool is used. A construction machine characterized in that it can be escaped.   2. The construction machine according to claim 1, wherein the depressurizing circuit is opened based on a signal of a drive start detecting means for detecting that the drive of the special work tool is started. .   4. The construction machine according to claim 3, wherein the signal of the drive start detection means is an operation signal of a work mode changeover switch that is switched when working with a special work tool.   4. The construction machine according to claim 3, wherein the signal of the drive start detecting means is an operation signal of a direction control valve for a special work tool for controlling the movement of a hydraulic actuator for driving the special work tool. A featured construction machine.   4. The construction machine according to claim 3, wherein the signal of the drive start detecting means connects a hydraulic actuator for driving the special working tool and a direction control valve for the special working tool for controlling the movement of the hydraulic actuator. A construction machine characterized by the hydraulic pressure of the connecting oil passage.

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