JP2011241792A - Control device for piston concrete pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a piston concrete pump simply configured to reduce noises and vibration due to the surge pressure of a hydraulic selector valve or the collision of main hydraulic cylinders during the change-over of the valve of the piston concrete pump.SOLUTION: The control device for the piston concrete pump includes proximity sensors 26a, 26b provided on head side pressure chambers 19a, 19b of the main hydraulic cylinders 4a, 4b of the piston concrete pump for detecting that main hydraulic pistons 6a, 6b come close to stroke ends, respectively. The control device further includes a back pressure valve 28 at a midway position between a pressure oil supply line 21 and a pressure oil drain line 23. When the main hydraulic piston 6a or 6b is detected by the proximity sensor 26a or 26b, the back pressure valve 28 is actuated only for a time set by a timer for restricting pressure oil to be returned to a tank 22 to hold pressure in the head side pressure chambers 19a, 19b, thus reducing the speeds of the main hydraulic pistons 6a, 6b.

Description

  The present invention controls a piston concrete pump for controlling switching of concrete suction and discharge in a piston concrete pump in which concrete in a hopper is alternately sucked and discharged by two concrete pumping cylinders. It relates to the device.

  There are various types of piston-type concrete pumps in which the concrete in the hopper is alternately sucked and discharged by two concrete cylinders for pumping. For example, switching between suction and discharge is possible. As a suction / discharge valve to be performed, there is a swing valve type that swings a swing pipe accommodated in a hopper left and right.

  The rocking valve type piston concrete pump is housed in a hopper with two suction and discharge ports arranged side by side, and a swing tube is swingably moved in the left and right direction, and alternately in the left and right suction and discharge ports. In addition to communicating with each other, two concrete pumping cylinders are communicated with the two suction and discharge ports, and two main hydraulic cylinders are connected to each concrete pumping cylinder via a cleaning chamber, respectively. The concrete pressure-feeding pistons connected to each other and housed in the two concrete pressure-feeding cylinders and the main hydraulic pistons housed in the two main hydraulic cylinders, respectively, are integrally connected via the piston rods. It is. Furthermore, the one end side pressure chambers of the two main hydraulic cylinders are connected to each other by a sealing line, and an oil pump and a tank are provided in the other end side pressure chamber of each of the main hydraulic cylinders, and a hydraulic switching valve is provided in the middle. Connected via a pressure oil supply / discharge line, and by switching the hydraulic pressure switching valve, pressure oil is alternately supplied from the oil pump to the main hydraulic cylinder, and the main hydraulic piston is moved forward and backward alternately to move the concrete pressure. The piston is alternately advanced and retracted, and the concrete pressure feeding cylinder can be alternately switched to suction and discharge.

  In a piston-type concrete pump having such a configuration, in order to switch the suction and discharge of the concrete pumping cylinder, pressure oil is supplied to and discharged from the main hydraulic cylinder by switching the hydraulic switching valve, and the main hydraulic piston in the main hydraulic cylinder When the cylinder is moved forward and backward, the main hydraulic piston may collide with the inner wall of the main hydraulic cylinder at the stroke end, which may cause vibration and noise of the piston-type concrete pump. In addition, vibration and noise may occur in the piston-type concrete pump due to the surge pressure of the hydraulic switching valve when switching the suction and discharge of the piston-type concrete pump. For this reason, conventionally, there have been proposed ones for reducing noise and vibration at the time of valve switching of a piston type concrete pump.

  For example, as shown in FIG. 9, two main hydraulic pressures are connected to two concrete pumping cylinders 3 a and 3 b connected to communicate with two suction and discharge ports 2 a and 2 b provided in the hopper 1. The cylinders 4a and 4b are connected via the cleaning chamber 5, and the main hydraulic pistons 6a and 6b stored in the main hydraulic cylinders 4a and 4b are stored in the concrete pumping cylinders 3a and 3b. 7 a and 7 b are connected via piston rods 8 a and 8 b, the two main hydraulic cylinders 4 a and 4 b are connected to the unidirectionally inclined oil pump 9 and the tank 10, the hydraulic switching valve 11 and the pressure oil supply / discharge line 12. And the rocking pipe 13 in the hopper 1 is swung in accordance with the forward and backward movement of the main hydraulic pistons 6a and 6b alternately, so that the concrete in the hopper 1 is transported to the concrete pressure feeding system. In the concrete pump of the swing valve type that can be alternately sucked and discharged by the cylinders 3a and 3b, the proximity sensors 14a and 14b are disposed at a position y before the forward stroke end position x in the main hydraulic cylinders 4a and 4b. And switching commands S1 and S2 are output to the swing pipe 13 and the hydraulic switching valve 11 based on the operation signals of the proximity sensors 14a and 14b, and the operation time for one stroke of the main hydraulic piston 6a or 6b is reached. The tilt angle is reduced by the correction time set on the basis, and the tilt angle is increased only while the main hydraulic piston 6a or 6b is retracted by the required amount from the forward stroke end position x after the correction time has elapsed. The controller 15 is configured to output a control command S to the oil pump 9. In the figure, 16 indicates a sealing line.

  In the piston-type concrete pump having such a configuration, when the valve is switched, as shown in FIG. 9, when one main hydraulic piston 4b arrives at a position y set before the forward stroke end position x, One proximity sensor 14b is activated and a signal is sent to the controller 15. Next, in the controller 15, from the signal from the one proximity sensor 14b and the signal output from the other proximity sensor 14a last time. The controller 15 calculates a control command S for calculating the operation time for one stroke of the one main hydraulic piston 6b and reducing the tilt angle of the uni-tilt oil pump 9 only during the correction time corresponding to the time. Is output to reduce the pressure oil discharge amount of the unidirectionally inclined oil pump 9 and then when the correction time has elapsed, the switching commands S1 and S2 are controlled with respect to the swing pipe 13 and the hydraulic switching valve 11. The control command S is output from the controller 15 and then the controller 15 increases the tilt angle of the one-side tilting oil pump 9 only while the main hydraulic piston 6b is retracted from the forward stroke end position x by a required amount. To increase the amount of pressure oil discharged from the unidirectionally inclined oil pump 9 and thus reduce the large pressure fluctuation at the time of switching between the main hydraulic pistons 6a and 6b. Pulsation is reduced to reduce pipe vibration and boom vibration (see, for example, Patent Document 1).

  As another example, although not shown, it is detected that the two main hydraulic cylinders in the swing valve type concrete pump are in positions immediately before the main hydraulic pistons reach the forward stroke end. Proximity sensors are provided, and a branch oil passage is branched from a pressure oil supply line that connects the oil pump and the main hydraulic cylinder, and a circuit for noise reduction is provided in the middle of the branch oil passage. There is a configuration in which the downstream end is connected to an oil tank so that the silent circuit is switched to the open side when the proximity sensor detects a main hydraulic piston. With such a configuration, there is one that decelerates the main hydraulic piston just before the main hydraulic piston reaches the forward stroke end to suppress the generation of impact sound when the main hydraulic piston collides with the inner wall of the main hydraulic cylinder. (For example, refer to Patent Document 2). In addition, each main hydraulic piston in the piston-type concrete pump described in Patent Document 2 is further provided with an impact mitigating member formed with a protruding portion via a compression coil spring so that the main hydraulic piston is located at the forward stroke end. It has also been proposed that the main hydraulic piston is cushioned in stages before reaching to suppress the generation of impact noise when the main hydraulic piston collides with the inner wall of the main hydraulic cylinder (for example, And Patent Document 3).

  Furthermore, as another example, although not shown in the figure, a position detection switch for detecting the position of each main hydraulic piston is provided in the two main hydraulic cylinders in the concrete pump of the swing valve type, and the oil pump A main relief valve is provided in the pressure oil supply line that connects the main hydraulic cylinder to the main hydraulic cylinder, and a sub-relief valve in which a solenoid valve and a tank are sequentially connected downstream is connected to the main relief valve to detect the position. There is a configuration in which the solenoid valve is opened when the switch detects the main hydraulic piston. With this configuration, when the main hydraulic piston reaches the forward stroke end, pressure oil is flowed from the main relief valve to the tank with the set pressure of the sub relief valve to decelerate the main hydraulic piston, and the main hydraulic piston becomes the main hydraulic cylinder. There is one that reduces the generation of noise and vibration caused by collision with an inner wall (see, for example, Patent Documents 4 and 5).

JP 2003-214332 A JP 2007-138817 A JP 2009-52473 A Japanese Patent No. 2510974 Japanese Patent Publication No. 07-056255

  However, in the one described in Patent Document 1, when each main hydraulic piston reaches the forward stroke end of the main hydraulic cylinder, it may not be able to sufficiently decelerate. There is a problem that it may not be fully demonstrated.

  Further, in the above-mentioned patent documents 2 and 3, the pressure oil pumped from the oil pump is returned to the tank through the silent circuit each time each main hydraulic piston reaches the forward stroke end. Therefore, there is a problem that the efficiency of the concrete pump is deteriorated. Further, in the device described in Patent Document 3, an impact relaxation member is provided in the main hydraulic cylinder via a compression coil spring, but there is a problem that the structure becomes too complicated.

  Further, in the above-described Patent Documents 4 and 5, the electromagnetic valve is operated based on the detection of the position detection switch even when the sub-relief valve is not operated. Therefore, there is a concern that the service life of the piston-type concrete pump may be affected or the frequency of overhauling the piston-type concrete pump may be increased.

  Therefore, the present invention has a simple structure and does not affect the efficiency of the piston-type concrete pump, and the noise pressure caused by the collision of mechanical parts such as the surge pressure of the hydraulic switching valve and the main hydraulic cylinder when switching the valve of the concrete pump. An object of the present invention is to provide a control device for a piston-type concrete pump capable of sufficiently reducing vibration.

  In order to solve the above-mentioned problem, the present invention, corresponding to claim 1, is a piston rod comprising a concrete pressure-feeding piston in two concrete pressure-feeding cylinders and a main hydraulic piston in two main hydraulic cylinders. Are connected to each other via a cap, and the cap-side pressure chambers or head-side pressure chambers of the main hydraulic cylinders are connected by a sealing line, and the head-side pressure chambers or cap-side pressure chambers of the main hydraulic cylinders are connected to each other. Each main hydraulic piston is connected by connecting an oil pump and a tank via a pressure oil supply / discharge line and a hydraulic switching valve, and switching the hydraulic switching valve to supply pressure oil alternately from the oil pump to the main hydraulic cylinder. By alternately moving forward and backward, the main hydraulic piston pumps the concrete sucked into the concrete pumping cylinder when the main hydraulic piston moves forward, and the main hydraulic piston Each main hydraulic piston is close to the forward stroke end in the vicinity of the forward stroke end of each main hydraulic cylinder in the piston concrete pump designed to suck concrete into the concrete pumping cylinder when retreating. And a back pressure valve that operates to squeeze the pressure oil returned from the main hydraulic cylinder to the tank based on a detection signal of the position detection device at a position upstream of the tank. It is set as the structure which provided.

  According to a second aspect of the present invention, a timer is provided that operates based on the detection signal of the position detection device in the above configuration, and the back pressure valve is operated for a time set in the timer.

  Further, according to claim 3, a pressure switch is provided on the discharge side of the oil pump in the above-described configuration, and the back pressure valve is controlled based on the detection signal of the pressure switch and the detection signal of one of the position detection devices. It is set as the structure made to operate | move.

  Further, corresponding to claim 4, the back pressure valve in the above configuration is provided between the hydraulic pressure switching valve and the tank.

  In each of the above-described configurations, the back-pressure valve that operates so as to throttle the pressure oil has a variable throttle amount.

According to the control device of the piston type concrete pump of the present invention, the following excellent effects are exhibited.
(1) A concrete pumping piston in two concrete pumping cylinders and a main hydraulic piston in two main hydraulic cylinders are integrally connected via a piston rod, respectively, and the cap side of the main hydraulic cylinder is connected. The pressure chambers or head side pressure chambers are connected by a sealed line, and an oil pump and a tank are connected to the head side pressure chamber or cap side pressure chamber of each main hydraulic cylinder via a pressure oil supply / discharge line and a hydraulic switching valve. By connecting, switching the hydraulic switching valve and alternately supplying pressure oil from the oil pump to the main hydraulic cylinder, each main hydraulic piston is alternately advanced and retracted, and when the main hydraulic piston moves forward, Pumps the concrete sucked into the concrete pumping cylinder, and when the main hydraulic piston moves backward, A position detection device for detecting the proximity of each main hydraulic piston to the forward stroke end is provided in the vicinity of the forward stroke end of each main hydraulic cylinder in the piston concrete pump designed to suck in the concrete. In addition, since a back pressure valve that operates to squeeze the pressure oil returned from the main hydraulic cylinder to the tank based on the detection signal of the position detection device is provided at the upstream side position of the tank, The main hydraulic piston can be decelerated in the vicinity of the stroke end with a simple structure, and the noise due to the surge pressure of the hydraulic switching valve when the piston type concrete valve is switched and the impact of the main hydraulic piston on the main hydraulic cylinder and other mechanical parts The vibration can be sufficiently reduced. Further, since the pressure oil returned from the main hydraulic cylinder to the tank is throttled by the back pressure valve, each main hydraulic piston can be decelerated without affecting the efficiency of the piston-type concrete pump.
(2) Also, a timer that operates based on the detection signal of the position detection device is provided, and the back pressure valve is operated for the time set in the timer, so the time for decelerating the main hydraulic piston is optimal. Can be set to a long time.
(3) Further, a pressure switch is provided on the discharge side of the oil pump, and the back pressure valve is operated based on the detection signal of the pressure switch and the detection signal of one of the position detection devices. The back pressure valve does not operate every time the position detection device detects the main hydraulic piston, and each main hydraulic piston can be decelerated without affecting the life of the piston-type concrete pump.
(4) Furthermore, since the back pressure valve is provided between the hydraulic pressure switching valve and the tank, the main hydraulic piston can be decelerated at a position near the stroke end with a simpler structure.
(5) By making the throttle amount of the back pressure valve operating so as to throttle the pressure oil variable, the speed at which each main hydraulic piston is decelerated can be easily adjusted.

1 is a hydraulic circuit diagram showing an embodiment of a control device for a piston-type concrete pump according to the present invention. It is a time chart of the control apparatus in embodiment of FIG. FIG. 2 is an electric circuit diagram of a control device in the embodiment of FIG. 1. It is a flowchart of the control apparatus in embodiment of FIG. It is a hydraulic circuit diagram which shows the other form of implementation of the control apparatus of the piston type concrete pump of this invention. It is a time chart of the control apparatus in embodiment of FIG. It is an electric circuit diagram of the control apparatus in embodiment of FIG. It is a flowchart of the control apparatus in embodiment of FIG. It is a hydraulic circuit diagram which shows an example of the control apparatus of the conventional piston type concrete pump.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 to FIG. 4 show an example in which the present invention is applied to a piston-type concrete pump of the same swing valve type as shown in FIG. Concrete pressure-feeding pistons housed in two concrete pressure-feeding cylinders and main hydraulic pistons 6a and 6b housed in two main hydraulic cylinders 4a and 4b are respectively integrated via piston rods 8a and 8b. The cap-side pressure chambers 17a and 17b of the main hydraulic cylinders 4a and 4b are connected to each other by a sealing line 18, and the oil pump 20 is connected to the head-side pressure chambers 19a and 19b of the main hydraulic cylinders 4a and 4b. The pressure oil supply line 21 connected to the discharge side and the pressure oil discharge line 23 connected to the tank 22 are connected to the pressure oil supply / discharge lines 24a and 24b. The main four-way valve 25 is connected as a hydraulic switching valve, and the main four-way valve 25 is switched to supply pressure oil from the oil pump 20 to the main hydraulic cylinders 4a and 4b alternately. The main hydraulic pistons 6a and 6b are alternately moved forward and backward, and when the main hydraulic piston 6a or 6b moves forward, the concrete sucked into the concrete pumping cylinder is pumped, and the main hydraulic piston In the piston-type concrete pump having a structure in which the concrete in the hopper is sucked into the concrete pumping cylinder when the 6b or 6a moves backward, the forward side (push side) of the main hydraulic cylinders 4a and 4b. When the main hydraulic pistons 6a and 6b move forward and approach the stroke end in the vicinity of the stroke end Proximity sensors 26a and 26b are provided as position detecting devices for the main hydraulic pistons 6a and 6b to be operated, and a 4-port 2-position pilot switching valve type is provided at a midway position between the pressure oil supply line 21 and the pressure oil discharge line 23. A back pressure valve 28 having a variable throttle 27 is provided in the operating position side flow path communicating with the pressure oil discharge line 23, and each hydraulic pilot of the back pressure valve 28, the pressure oil supply line 21, and the pressure oil discharge line 23 are provided. The pilot pipes 29a and 29b are respectively connected to the pilot pipes 29a and 29b, and an electromagnetic valve 30 for a back pressure valve of the 4-port 2-position solenoid valve type is provided in the middle of the pilot pipes 29a and 29b, and the proximity sensor 26a or 26b is operated. The solenoid SOL. Of the back pressure valve solenoid valve 30 is set for a time set in a timer (not shown). 1 is excited to switch the back pressure valve 28 to the operating position, and the pressure oil returned from the main hydraulic cylinders 4a and 4b to the tank 22 is squeezed by the variable throttle 27 to be stored in the main hydraulic pistons 6a and 6b. The pressure in the head side pressure chambers 19a and 19b is held.

  In FIG. 1, reference numeral 31 denotes a position which becomes a stroke end on the forward side (push side) in each of the head side pressure chambers 19 a and 19 b of the main hydraulic cylinders 4 a and 4 b, and a stroke which is a position before reaching the stroke end position 31. The proximity sensors 26a and 26b described above are provided in the vicinity of the end. A pilot switching valve 32 is provided at a position corresponding to the proximity sensors 26a, 26b on the head side pressure chambers 19a, 19b side of the main hydraulic cylinders 4a, 4b. The main hydraulic piston 6a or 6b is a stroke end position on the forward side. The main four-way valve 25 is switched when the pilot pressure is applied to the main four-way valve 25 when the front position 31 is reached. Reference numeral 33 denotes a relief valve provided between the oil pump 20 and the back pressure valve 28 in the pressure oil supply line 21.

  Next, FIG. 2 shows a time chart of the control device for the piston-type concrete pump of the present invention shown in FIG. 1. As shown in FIG. 1, the left main hydraulic cylinder 4a is on the push side and the right main hydraulic cylinder 4a is on the right side. In a state where the cylinder 4b is on the return side and the main four-way valve 25 is switched to the right cross port, the control device for the piston-type concrete pump of the present invention has the main hydraulic piston 6a in the left main hydraulic cylinder 4a. Is pushed to reach a position near the stroke end, the proximity sensor 26a is turned ON. At this time, the timer is turned ON, and the solenoid SOL. Of the back pressure valve solenoid valve 30 is set for the time set in the timer. The back pressure valve 28 is switched to the operating position when 1 is excited and the back pressure valve electromagnetic valve 30 is operated. As a result, the pressure oil returned from the head side pressure chamber 19a of the main hydraulic cylinder 4a to the tank 22 is throttled by the variable throttle 27 of the back pressure valve 28. Thereafter, when the time set by the timer elapses, the solenoid SOL. When 1 is demagnetized, the back pressure valve 28 is switched to the normal position so as to be inactive.

  The control device for a piston-type concrete pump of the present invention for realizing the above operation has an electric circuit configuration as shown in FIG. That is, a proximity sensor / left circuit, a proximity sensor / right circuit including one proximity sensor 26a and another proximity sensor 26b in parallel and a relay T1 for each proximity sensor 26a, 26b, and the instantaneous operation time limit of the relay T1 The return make contact T1 and the solenoid SOL. 1 is provided in parallel with the power supply. As a result, the solenoid SOL. 1 is energized for the time set in the timer when any one of the proximity sensors 26a and 26b is turned on, the back pressure valve 28 is switched to the operating position, and the main hydraulic cylinders 4a and 4b are returned to the tank 22. The pressure of the main hydraulic pistons 6a and 6b is maintained by maintaining the pressure of the head side pressure chambers 19a and 19b in the main hydraulic cylinders 4a and 4b by restricting the pressure oil to be generated by the variable throttle 27 of the back pressure valve 28. It is dropped at the position before the stroke end required.

  In this configuration, as shown in FIG. 4, when the operation of the piston-type concrete pump (CP) is started, the normal position side parallel port of the back pressure valve 28 to the right cross of the main four-way valve 25 in FIG. Pressure oil is supplied to the head-side pressure chamber 19a of the main hydraulic cylinder 4a on the right side of the figure through the port. As a result, the main hydraulic piston 6b in the main hydraulic cylinder 4b is moved (retracted) in the direction indicated by the arrow in FIG. Further, since the cap-side pressure chamber 17b of the main hydraulic cylinder 4b and the cap-side pressure chamber 17a of the main hydraulic cylinder 4a on the left side in the figure are connected by a sealing line 18, the main hydraulic piston 6b is retracted. The main hydraulic piston 6a in the main hydraulic cylinder 4a is moved (moved forward) in the direction indicated by the arrow in FIG. 1, and the main hydraulic cylinder / left-pressing state shown in FIG.

  Next, when the main hydraulic piston 6a in the left main hydraulic cylinder 4a moves forward and reaches a position before the stroke end position 31, the proximity sensor 26a detects the position of the main hydraulic piston 6a, and the proximity sensor 26a is turned ON, and the spool tip of the pilot switching valve 32 is pushed by the main hydraulic piston 6a. As a result, the relay T1 shown in FIG. 3 is excited, and the make contact T1 for returning to the instantaneous operation time limit is turned ON. At this time, the solenoid SOL. 1 is energized and the back pressure valve solenoid valve 30 is operated to switch the back pressure valve 28 to the operating position side parallel port, so that the pressure oil returned from the main hydraulic cylinder 4 a to the tank 22 is throttled by the variable throttle 27. Will be. Since the pressure oil is returned to the tank 22 in such a state that the pressure oil is squeezed, the pressure in the head side pressure chamber 19a in the main hydraulic cylinder 4a is held, and the main hydraulic pistons 6a and 6b are driven at speed. Will be moved in the direction of the stroke end. Thereafter, when the time set in the timer elapses, the make contact T1 for returning to the instantaneous operation time limit is turned OFF and the solenoid SOL1 is demagnetized, so that the back pressure valve solenoid valve 30 and the back pressure valve 28 are switched to the normal position. Thus, the back pressure valve 28 is deactivated. Further, since the spool tip is pushed by the main hydraulic piston 6b as described above, the main four-way valve 25 is switched from the right cross port side in FIG. 1 to the left parallel port side.

  Subsequently, the main four-way valve 25 is switched, and pressure oil is supplied from the oil pump 20 to the head-side pressure chamber 19a of the left main hydraulic cylinder 4a through the normal position side parallel port of the back pressure valve 28 and the parallel port of the main four-way valve 25. Then, the main hydraulic piston 6a in the left main hydraulic cylinder 4a is moved (retracted) to the cap side, and from the cap side pressure chamber 17a of the main hydraulic cylinder 4a to the cap side of the right main hydraulic cylinder 4b. The pressure oil moves into the pressure chamber 17b via the sealing line 18, and the main hydraulic piston 6b in the right main hydraulic cylinder 4b is moved (advanced) to the head side. Right push operation is activated. Thereafter, when the main hydraulic piston 6b in the right main hydraulic cylinder 4b reaches a position before the stroke end position 31 of the head side pressure chamber 19b, the proximity sensor 26b detects the position of the main hydraulic piston 6b, The front end of the spool of the pilot switching valve 32 is pushed by the main hydraulic piston 6b, and the relay T1 shown in FIG. 3 is excited to turn on the make contact T1 for returning to the instantaneous operation time limit. At this time, the solenoid SOL. 1 is excited and the back pressure valve electromagnetic valve 30 is operated, so that the back pressure valve 28 is switched to the operating position side parallel port, and the pressure oil returned from the main hydraulic cylinder 4 a to the tank 22 is changed to the variable throttle 27 of the back pressure valve 28. Will be squeezed. Thereby, the speed of the main hydraulic pistons 6a and 6b at the time of switching is reduced. After that, when the time set in the timer elapses, the make contact T1 for instantaneous operation timed return is turned OFF and the solenoid SOL. 1 is demagnetized, the back pressure valve solenoid valve 30 and the back pressure valve 28 are switched to the normal position, and the main four-way valve 25 is switched from the left parallel port side to the right cross port side in FIG. Similarly, the piston concrete pump will be controlled.

  As described above, according to the control device for the piston-type concrete pump in the embodiment shown in FIGS. 1 to 4, each main hydraulic cylinder 4a, 4b in the piston-type concrete pump has the main pressure chambers 19a, 19b provided with the main pressure chambers 19a, 19b. Proximity sensors 26a and 26b for detecting that the hydraulic pistons 6a and 6b move forward and approach the stroke end are provided, and the proximity sensors 26a and 26b are provided at intermediate positions between the pressure oil supply line 21 and the pressure oil discharge line 23. Since either one of the detection signals is received, the back pressure valve 28 that operates to throttle the pressure oil returned from the main hydraulic cylinders 4a and 4b to the tank 22 for the time set in the timer is provided. The main hydraulic pistons 6a and 6b can be decelerated near the stroke end (front position) with a simple structure. Therefore, it is possible to sufficiently reduce the noise and vibration due to the surge pressure of the main four-way valve 25 and the collision of the main hydraulic pistons 6a and 6b with the mechanical parts such as the main hydraulic cylinders 4a and 4b when the piston concrete pump is switched. it can. Further, since the pressure oil returned from the main hydraulic cylinders 4a, 4b to the tank 22 is throttled by the back pressure valve 28, the main hydraulic pistons 6a, 6b are decelerated without affecting the efficiency of the piston-type concrete pump. Can be made. Further, since the back pressure valve 28 is operated for the time set in the timer, the time for decelerating the main hydraulic pistons 6a and 6b can be set to an optimum time.

  In the above, if the variable throttle 27 of the back pressure valve 28 is made variable and the throttle amount of the pressure oil returned to the tank 22 is made variable, the speed at which the main hydraulic pistons 6a and 6b are decelerated can be arbitrarily adjusted. Will be able to.

  Next, FIGS. 5 to 8 show another embodiment of the control device for the piston-type concrete pump according to the present invention. In the control device for the piston-type concrete pump of the embodiment shown in FIGS. Instead of the configuration in which the back pressure valve 28 is operated only for the set time of the timer, a pressure switch 34 is provided between the oil pump 20 and the back pressure valve 28 in the pressure oil supply line 21, and either the proximity sensor 26a or 26b is provided. If the pressure switch 34 has reached the set pressure when the valve is operating, the solenoid SOL. 1 is excited, the back pressure valve electromagnetic valve 30 is operated, the back pressure valve 28 is switched to the operating position, and the pressure oil returned from the main hydraulic cylinders 4a, 4b to the tank 22 is changed to the back pressure valve 28. A configuration is adopted in which the pressure in the head side pressure chambers 19a and 19b in the main hydraulic pistons 6a and 6b is maintained by restricting with the restrictor 27.

  FIG. 6 shows a time chart of the control device for the piston type concrete pump of the present invention shown in FIG. 5. As shown in FIG. 5, the left main hydraulic cylinder 4a is on the push side and the right main cylinder is on the push side. In the state where 4b is the return side and the main four-way valve 25 is switched to the right cross port, the control device for the piston-type concrete pump in the present embodiment is the main hydraulic piston in the left main hydraulic cylinder 4a. When 6a is pushed to reach the position near the stroke end, the proximity sensor 26a is turned ON, and at this time, the pressure on the discharge side of the oil pump 20 reaches the pressure set by the pressure switch 34 (for example, about 10 MPa). When the pressure switch 34 is ON, the solenoid SOL. The back pressure valve 28 is switched to the operating position when 1 is excited and the back pressure valve electromagnetic valve 30 is operated. As a result, the pressure oil returned from the head-side pressure chamber 19a of the main hydraulic cylinder 4a to the tank 22 is throttled by the variable throttle 27 of the back pressure valve 28. In this state, the main four-way valve 25 is switched, whereby the pressure switch 34 Is turned OFF, and at the same time, the solenoid SOL. 1 is demagnetized and the back pressure valve 28 is deactivated.

  Further, the control device for the piston-type concrete pump shown in FIG. 5 for realizing the above-described operation includes one proximity sensor 26a and the other proximity sensor 26b in parallel as shown in FIG. Proximity sensor / left circuit, proximity sensor / right circuit including relay X1 of 26b, pressure switch circuit including pressure switch 34 and relay X2, make contact X1 of relay X1, make contact X2 of relay X2, and back Solenoid SOL. Of solenoid valve 30 for pressure valve. The back pressure valve circuit having 1 is provided in parallel with the power supply. As a result, the solenoid SOL. 1 is excited when one of the proximity sensors 26a and 26b is turned ON, and the pressure switch 27 is turned ON, and the back pressure valve 28 is switched to the operating position, from the main hydraulic cylinders 4a and 4b. The pressure oil returned to the tank 22 is throttled by the variable throttle 27 of the back pressure valve 28 to maintain the pressure in the head side pressure chambers 19a, 19b in the main hydraulic cylinders 4a, 4b. The moving speed is reduced at the position before the stroke end.

  Other configurations are the same as those shown in FIGS. 1 to 4, and the same components are denoted by the same reference numerals.

  In such a configuration, as shown in FIG. 8, when the operation of the piston-type concrete pump (CP) is started, the normal position side parallel port of the back pressure valve 28 from the oil pump 20 to the right cross of the main four-way valve 25 in FIG. Pressure oil is supplied to the head-side pressure chamber 19b of the main hydraulic cylinder 4b on the right side of the figure through the port, and the main hydraulic cylinder / left-pressing state shown in FIG. 8 is entered.

  Next, when the main hydraulic piston 6a in the left main hydraulic cylinder 4a moves forward and reaches a position before the stroke end position 31, the proximity sensor 26a detects the position of the main hydraulic piston 6a, and the proximity sensor 26a is turned ON. This excites the relay X1 shown in FIG. 7, and the make contact X1 of the relay X1 is turned ON. At this time, if the discharge pressure of the oil pump 20 has reached the set value of the pressure switch 34, the relay X2 of the pressure switch 34 shown in FIG. 7 is energized and the make contact X2 is turned on. Solenoid SOL. Of solenoid valve 30 for pressure valve. 1 is excited, and the back pressure valve electromagnetic valve 30 is switched to the operating position. Next, when the back pressure valve electromagnetic valve 30 is switched to the operating position, the direction of the pilot pressure is changed, whereby the back pressure valve 28 is switched to the operating position side parallel port, so that the main hydraulic cylinder 4a returns to the tank 22. The pressurized oil is throttled by the variable throttle 27 of the back pressure valve 28. Since the pressure oil is returned to the tank 22 in such a state that the pressure oil is squeezed, the pressure in the head side pressure chamber 19a in the main hydraulic cylinder 4a is held, and the main hydraulic pistons 6a and 6b are driven at speed. Will be moved in the direction of the stroke end. Thereafter, the spool tip of the pilot switching valve 32 is pushed by the main hydraulic piston 6a, so that the main four-way valve 25 is switched from the right cross port side to the left parallel port side in FIG. As a result, when the pressure switch 34 is turned off, the relay X2 in FIG. 7 is turned off, and the solenoid SOL. 1 is demagnetized, the back pressure valve solenoid valve 30 and the back pressure valve 28 are switched to the normal position, and the back pressure valve 28 is inactivated.

  Subsequently, the main four-way valve 25 is switched, and pressure oil is supplied from the oil pump 20 to the head-side pressure chamber 19a of the left main hydraulic cylinder 4a through the normal position side parallel port of the back pressure valve 28 and the parallel port of the main four-way valve 25. Then, the main hydraulic piston 6b in the right main hydraulic cylinder 4b is moved (moved forward) to the head side, and the main hydraulic cylinder / right push operation state shown in FIG. Thereafter, when the main hydraulic piston 6b in the right main hydraulic cylinder 4b reaches a position before the stroke end position 31 of the head side pressure chamber 19b, the proximity sensor 26b detects the position of the main hydraulic piston 6b, The spool tip of the pilot switching valve 32 is pushed by the main hydraulic piston 6b. When the proximity sensor 26b is activated, the relay X1 shown in FIG. 7 is excited to turn on the make contact X1. At this time, if the discharge pressure of the oil pump 20 has reached the set value of the pressure switch 34, the relay X2 of the pressure switch 34 shown in FIG. 7 is excited and the make contact X2 is turned on. Solenoid SOL. Of solenoid valve 30 for pressure valve. 1 is excited, the back pressure valve electromagnetic valve 30 is switched to the operating position, the direction of the pilot pressure is changed by the switching, the back pressure valve 28 is switched to the operating position side parallel port, and the main hydraulic cylinder 4b. Thus, the pressure oil returned to the tank 22 is throttled by the variable throttle 27 of the back pressure valve 28. Thereby, the speed of the main hydraulic pistons 6a and 6b at the time of switching is reduced. After that, since the spool tip of the pilot switching valve 32 is pushed by the main hydraulic piston 6b, the main four-way valve 25 is switched from the left parallel port side in FIG. 5 to the right cross port side. As a result, when the pressure switch 34 is turned off, the relay X2 in FIG. 7 is turned off, and the solenoid SOL. 1 is demagnetized, the back pressure valve solenoid valve 30 and the back pressure valve 28 are switched to the normal position, the back pressure valve 28 is inactivated, and thereafter, the piston-type concrete pump is similarly controlled.

  When the discharge pressure of the oil pump 20 is less than the set value of the pressure switch 34, the relay X2 is demagnetized in FIG. 7 and the make contact X2 is OFF, so the proximity sensors 26a and 26b are connected to the main hydraulic piston. Even if the make contact X1 is turned ON by detecting 6a, 6b, the solenoid SOL. 1 is not excited and the back pressure valve 28 does not operate.

  As described above, according to the control device for the piston-type concrete pump in the embodiment shown in FIGS. 5 to 8, each main hydraulic cylinder 4a, 4b in the piston-type concrete pump has the main pressure chambers 19a, 19b provided with the main pressure chambers 19a, 19b. Proximity sensors 26a and 26b for detecting that the hydraulic pistons 6a and 6b are moved forward and close to the stroke end are provided, a pressure switch 34 is provided in the pressure oil supply line 21, and a pressure switch in the pressure oil supply line 21 is provided. When the detection signal of the pressure switch 34 and the detection signal of one of the proximity sensors 26a and 26b are received at the downstream side position 34 and the pressure oil discharge line 23 from the main hydraulic cylinders 4a and 4b to the tank 22 Since the back pressure valve 28 that operates to squeeze the returned pressure oil is provided, the structure is simple. Each main hydraulic piston 6a, 6b can be decelerated at a position near the stroke end (front position), and the surge of the main four-way valve 25 during valve switching of the concrete pump without affecting the efficiency of the piston concrete pump. Noises and vibrations due to pressure and collisions of main hydraulic pistons 6a and 6b with mechanical components such as main hydraulic cylinders 4a and 4b can be sufficiently reduced. Further, since the back pressure valve 28 is operated based on the detection signal of one of the proximity sensors 26a and 26b and the detection signal of the pressure switch 34, the proximity sensors 26a and 26b detect the main hydraulic pistons 6a and 6b. Each time, the back pressure valve 28 does not operate, and the main hydraulic pistons 6a and 6b can be decelerated without affecting the life of the piston-type concrete pump.

  In the above embodiment, the case where the present invention is applied to an oscillating valve type piston concrete pump has been described as an example. However, the present invention is not limited to this, and in the above embodiment, the spool of the pilot switching valve 32 is used. The main four-way valve 25 is switched by the main hydraulic pistons 6a and 6b being pushed at the tip, but the present invention is not limited to this. For example, the main four-way valve 25 is used as an electromagnetic switching valve and the proximity sensors 26a and 26b Although it may be configured to be switched based on detection, the hydraulic switching valve 25 is not limited to a four-way valve, and the case where a pilot-type switching valve is applied to the back pressure valve 28 has been described. Instead, for example, an electromagnetic switching valve that switches only for the time set in the timer based on the detection signals of the proximity sensors 26a and 26b. In other words, the switching valve may be an electromagnetic switching valve that is switched based on the detection signals of the proximity sensors 26a and 26b and the detection signal of the pressure switch 34. The two-position electromagnetic switching valve may be provided only in the middle of the pressure oil discharge line 23, or the back pressure valve 28 and the pressure switch 34 may be provided in the pressure oil supply / discharge lines 24a and 24b, respectively. The downstream ends of the pressure oil supply / discharge lines 24a, 24b in the above embodiment are connected to the cap side pressure chambers 17a, 17b of the main hydraulic cylinders 4a, 4b, respectively, and the heads of the main hydraulic cylinders 4a, 4b are connected. The side pressure chambers 19a and 19b may be connected to each other by a sealing line 18, and various changes may be made without departing from the scope of the present invention. To be added to is a matter of course.

4a, 4b Main hydraulic cylinder 6a, 6b Main hydraulic piston 8a, 8b Piston rod 18 Sealing line 19a, 19b Head side pressure chamber 20 Oil pump 22 Tank 24a, 24b Pressure oil supply / discharge line 25 Main four-way valve (hydraulic switching valve)
26a, 26b Proximity sensor (position detection device)
28 Back pressure valve 34 Pressure switch

Claims (5)

  The concrete pressure-feeding pistons in the two concrete pressure-feeding cylinders and the main hydraulic pressure pistons in the two main hydraulic cylinders are integrally connected to each other via the piston rod, and the cap-side pressure chambers of the main hydraulic cylinders are connected to each other. Alternatively, the head side pressure chambers are connected to each other by a sealed line, and an oil pump and a tank are connected to the head side pressure chamber or cap side pressure chamber of each main hydraulic cylinder via a pressure oil supply / discharge line and a hydraulic switching valve. , By switching the hydraulic switching valve and alternately supplying pressure oil from the oil pump to the main hydraulic cylinder, each main hydraulic piston is alternately advanced and retracted, and when the main hydraulic piston moves forward, the concrete pressure feeding The concrete sucked into the cylinder is pumped, and when the main hydraulic piston moves backward, the concrete pumping cylinder A position detection device for detecting the proximity of each main hydraulic piston to the forward stroke end at a position near the forward stroke end of each main hydraulic cylinder in the piston concrete pump adapted to suck And a back pressure valve that operates to squeeze the pressure oil that is returned from the main hydraulic cylinder to the tank based on a detection signal of the position detection device, at a position upstream of the tank. A control device for a piston-type concrete pump.   The control device for a piston-type concrete pump according to claim 1, wherein a timer that operates based on a detection signal of the position detection device is provided, and the back pressure valve is operated for a time set in the timer.   The piston-type concrete according to claim 1, wherein a pressure switch is provided on the discharge side of the oil pump, and the back pressure valve is operated based on a detection signal of the pressure switch and a detection signal of one of the position detection devices. Pump control device.   4. The control device for a piston-type concrete pump according to claim 1, wherein the back pressure valve is provided between the hydraulic switching valve and the tank.   The control device for a piston-type concrete pump according to claim 1, 2, 3, or 4, wherein the amount of throttle of the back pressure valve that operates so as to throttle the pressure oil is variable.

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