JP2007138817A - Control apparatus of piston concrete pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an impact sound from occurring when a pump cylinder is extended most by decelerating the extension speed when the pump cylinder is extended most in a concrete pump which feeds under pressure ready-mixed concrete by sequential operation of a pair of pump cylinders. <P>SOLUTION: A concrete apparatus comprises a detection means ED to detect the position just before the pump cylinders 20 and 30 are extended most. A discharge oil passage 50 to connect an hydraulic oil passage Pu and the pump cylinders 20 and 30 is connected to an oil tank T via a silencing circuit CS, and the silencing circuit CS is switched to an open side upon detection by the detection means ED when the cylinders 20 and 30 are extended to open the passage 50 to the oil tank T. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a concrete pump that feeds ready-mixed concrete in a hopper by alternately supplying pressure oil discharged from a hydraulic pump to a pair of right and left pump cylinders for feeding concrete.

Conventionally, in the concrete pump, a variable displacement hydraulic pump is used to alternately supply pressure oil to a pair of pump cylinders, and when each pump cylinder is close to the maximum extension position, the discharge amount of the hydraulic pump is reduced. It is well known that the pump cylinders are controlled so as to decelerate the extension speed so as to prevent the generation of a loud impact sound when each cylinder is fully extended (see Patent Document 1).
JP 2003-214332 A

  By the way, what is disclosed in Patent Document 1 is that when each pump cylinder reaches near the maximum extension position, the discharge amount of the pump is reduced by adjusting the swash plate of the variable displacement pump to the reduction side, Since the pump cylinder is controlled to decelerate the extension speed, it is difficult to instantaneously reduce the discharge volume.As a result, the pump cylinder is at its maximum extension position before the pump cylinder sufficiently decelerates. Therefore, there is a problem that the impact sound cannot be suppressed.

  The present invention has been made in view of the above points, and is a novel piston-type concrete in which the extension speed is surely controlled to be reduced before each pump cylinder reaches the maximum extension position to solve the above problem. An object of the present invention is to provide a pump control device.

In order to achieve the above object, the invention described in claim 1 is a piston-type concrete pump configured to pump a ready-mixed concrete in a hopper by a pair of pump cylinders and a dredging operation of these pump cylinders.
Branching oil branched from a detection means for detecting that each pump cylinder is immediately before the maximum extension position, and a discharge oil passage connecting the hydraulic pump and the pair of pump cylinders, and communicating the discharge oil passage to an oil tank A silent circuit that is interposed in the middle of the branch oil passage and controls the opening and closing of the branch oil passage, and the silent circuit is opened when the detection means detects when the pump cylinders are extended. It is characterized by switching control to the side.

  In order to achieve the above object, according to a second aspect of the present invention, in the control according to the first aspect, when the detecting means detects the contraction of each pump cylinder, the silent circuit is moved to the closed side. It is characterized by switching control.

  Furthermore, in order to achieve the above object, according to a third aspect of the present invention, in the control according to the first or second aspect, the silent circuit includes a first switching valve and a second switching valve arranged in parallel, These valves are opened and closed separately between the branch oil passage and the oil tank, and the passage flow rate when the second switching valve is opened is larger than the passage flow rate when the first switching valve is opened. When the detecting means detects when the cylinder is extended, the second switching valve is opened after the first switching valve is opened.

  Furthermore, in order to achieve the above object, according to a fourth aspect of the present invention, in the control 1, 2, or 3, the branch is provided on a discharge oil passage 50 connected to a discharge side of the hydraulic pump. A check valve for preventing the hydraulic oil from flowing backward from the pump cylinder side to the hydraulic pump side is connected to the downstream side of the connecting portion with the oil passage.

  According to the invention described in each claim, since the extension speed at the time of the maximum extension of each pump cylinder can be quickly decelerated by the operation of the silent circuit, it is possible to reliably generate the impact sound at the time of the maximum extension of one of the pump cylinders. Can be suppressed.

  According to the second aspect of the present invention, since the initial extension speed of the other pump cylinder can be reduced, the operation noise during the initial extension of the pump cylinder can be suppressed.

  Furthermore, according to the third aspect of the present invention, the extension speed of the pump cylinder can be decelerated in two stages, so that the extension control of the pump cylinder can be smoothly controlled and the extension time of the pump cylinder can be controlled. Can be prevented from becoming unnecessarily long.

  Furthermore, according to the fourth aspect of the present invention, it is possible to prevent the hydraulic oil from flowing backward from the pump cylinder to the hydraulic pump.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below based on examples of the present invention shown in the accompanying drawings.

  FIG. 1 is a side view of a concrete pump truck, FIG. 2 is a view taken in the direction of arrow 2 in FIG. 1, FIG. 3 is a side view showing a state of pumping ready concrete by boom piping of the concrete pump truck, and FIG. FIG. 5 is a hydraulic circuit diagram of the concrete pump in the low pressure (standard) pumping mode, FIG. 6 is a hydraulic circuit diagram of the concrete pump in the high pressure pumping mode, and FIGS. FIG. 13 is a circuit diagram showing the operation of the silent circuit.

  1-3, a support column 2 is mounted on a base 1 mounted on a front portion of a concrete frame F of a concrete pump vehicle, which is indicated by reference numeral VC, so as to be rotatable around a vertical axis LL. The multi-stage bending boom B is connected to the upper end of the support column 2 by a plurality of telescopic cylinders 3a to 3d so as to be able to be bent up and down. The multi-stage bending boom B is supported with a ready-mixed concrete pressure-feeding boom pipe 4, and the boom pipe 4 can be bent according to the bending and stretching of the multi-stage bending boom B.

  In addition, since the multistage bending boom B and boom piping 4 are conventionally well-known, detailed description is abbreviate | omitted.

  A reciprocating concrete pump P is mounted on the palm frame F. This concrete pump P includes a hopper 6 and is configured so that the ready-mixed concrete put into the hopper 6 can be pumped to the outside from the discharge port 7 at the tip of the concrete pump P.

  As shown in FIG. 3, a flexible pumping pipe 8 provided on the palm frame F is detachably connected to the discharge port 7 of the pump body 5, and the pumping pipe 8 passes through the support column 2. The boom pipe 4 is detachably connected to the base end of the boom pipe 4, and low-pressure (standard pressure) ready-mixed concrete is pumped from the concrete pump P through the boom pipe 4.

  As shown by a two-dot chain line in FIGS. 1 and 2, another discharge pipe 9 can be detachably connected to the discharge port 7 of the concrete pump P. The laying pipe 10 laid on the ground is detachably connected.

  This laying pipe 10 is not operated up and down together with the multistage bending boom B, is used along the ground, a low building, etc., is thicker and more robust than the boom pipe 4, and It is heavier than that, and high-pressure ready-mixed concrete is pumped from the concrete pump P through the laying pipe 10.

  The multi-stage bending boom B is provided with boom position detecting means Se for detecting the position thereof. In this embodiment, the boom position detection means Se includes a turning sensor Se1 that detects a turning angle in the left-right direction of a multi-stage bending boom B, which will be described later, and an angle sensor Se2 that detects the undulation angle.

  As shown in FIGS. 1 to 3, a turning sensor Se <b> 1 is provided between the base 1 and the base end of the support column 2, and the turning sensor Se <b> 1 is connected to the proximity sensor 12 provided on the base 1 and the support. It consists of a dog 13 provided on the column 2, and the support column 2 is a small angle (5 °) or less to the left and right with respect to the vertical center line LL of the palm frame F along with the multistage bending boom B with respect to the base 1 It is turned on when it is at. In addition, an angle sensor Se2 is provided at the base end of the multi-stage bending / extending boom B, and the angle sensor Se2 is configured so that the multi-stage bending / extending boom B has an elevation angle from a prone position of a small angle (10 °) or less. It is turned on at some time.

  Next, a relay control circuit that selectively switches and controls the concrete pump P between a low pressure (standard pressure) operation that is pumped through the boom pipe 4 and a high pressure operation that is pumped through the laying pipe 10 will be described with reference to FIG. 4. To do.

  The power supply circuit 90 to which the main switch MS is connected includes a circuit 91 in which the turning sensor Se1 and a relay CR1 excited by the ON operation of the sensor Se1 are connected in series, and the angle sensor Se2 and the sensor Se2 ON. A circuit 92 in which a relay CR2 excited in operation is connected in series, a circuit 93 in which normally-open relay switches Cr1, Cr21 and a relay CR3, which are turned on by excitation of the relays CR1 and CR2, are connected in series; A concrete pump operation switch S1, a circuit 94 in which a concrete pump operation circuit is connected in series, a manual concrete pump high / low pressure changeover switch S2, a normally open relay switch Cr3 which is turned on by excitation of the relay CR3, , The first and second high and low pressure electromagnetic switching valves V1, V2 (FIG. 5) arranged in parallel. Solenoid 6 reference) SOL1, the circuits 95 connected to solenoid SOL2 in series are connected in parallel.

  The main switch MS, the concrete pump operation switch S1, and the concrete pump high / low pressure changeover switch S2 are provided in a concrete pump operation panel (not shown) provided in the driver's seat of the concrete pump vehicle VC.

  When the turning sensor Se1 and the angle sensor Se2 are turned on with the main switch MS, the concrete pump operation switch S1, and the concrete pump high / low pressure switch S2 turned on, the relays CR1 and CR2 are excited, and the relay switch Cr1 , Cr1 is turned on, the relay CR3 is excited and the relay switch Cr3 is turned on, so that the solenoids SOL1, SOL2 of the first and second high / low pressure electromagnetic switching valves V1, V2 are excited and are on the high pressure operation side (see FIG. 6). Switch to.

  As shown in FIGS. 5 and 6, the concrete pump P is a hydraulically driven reciprocating piston pump, and includes a pair of pump cylinders 20 and 30 in parallel with each other. Drive cylinders 21 and 31 for driving the pump are integrally connected to the base end via the center frame 40, respectively. The pump pistons 22 and 32 that are slidably fitted in the pair of pump cylinders 20 and 30, respectively, and the drive pistons 23 and 33 that are slidably fitted in the drive cylinders 21 and 31, respectively. The piston rods 24 and 34 that slidably penetrate the frame 40 are integrally connected to each other. The drive pistons 23 and 33 divide the corresponding drive cylinders 21 and 31 into front oil chambers 21a and 31a on the piston rod side and base oil chambers 21b and 31b on the piston side.

  The hopper 6 is connected to the tip of the pair of pump cylinders 20 and 30. The hopper 6 is supplied with ready-mixed concrete as needed from a concrete mixer truck or the like, and serves as a supply source of the concrete pump P. Further, the discharge port 7 is opened in the front surface of the hopper 6, and a curved tubular S-shaped valve (oscillating tube) 15 is accommodated and supported in the lower portion of the hopper 6. The S-shaped valve 15 is rotatable about the axis of the rotation support shaft 16 integral therewith, and the front portions of the pair of pump cylinders 20 and 30 can be alternately switched and communicated with the discharge port 7.

  The rotation support shaft 16 is connected to a valve switching drive means D (known in the art) for switching the S-shaped valve 15 by rotating it in synchronism with the operation of both pump pistons 22 and 32. The During the operation of the concrete pump P, the valve switching drive means D discharges a pair of pump cylinders 20 and 30 in the hopper 6 in the state of sucking ready-mixed concrete and in the state of pressure feeding of ready-mixed concrete. The S-shaped valve 15 is switched and controlled so as to be alternately connected to 7 so that the ready-mixed concrete is smoothly pumped.

  A pair of limit switches 25 and 35 are provided on the front side of the pair of drive cylinders 21 and 31, respectively, and an operation signal of these limit switches 25 and 35 is input to the valve switching drive means D. Thus, the S-shaped valve 15 is switched. Further, the control hydraulic pressure generated by the valve switching operation of the valve switching drive means D is supplied as pilot hydraulic pressure to the operation portion of the switching valve V, which will be described later, through the pilot oil passages 43 and 44, and the switching valve V is switched. .

  Two ports on the inlet side of the switching valve V for switching the pair of pump cylinders 20 and 30 so as to mutually operate are a discharge oil passage 50 connected to the discharge side of the variable displacement hydraulic pump Pu, The discharge oil passage 50 is connected to a reflux oil passage 70 connected to the oil tank T, and the discharge oil passage 50 is connected to the oil tank via a relief valve 45.

  Two ports on the outlet side of the switching valve V are connected to hydraulic oil passages 51 and 61, respectively. One hydraulic oil passage 51 is branched into a front oil passage 52 and a base oil passage 53, and the front oil passage 52 communicates with the front oil chamber 21a of the drive cylinder 21 via the direction control valve v1. The base side oil passage 53 communicates with the base oil chamber 31b of the drive cylinder 31 via the direction control valve v2.

  The other second hydraulic oil passage 61 is branched into a front-side oil passage 62 and a base-side oil passage 63, and the front-side oil passage 62 is connected to the front oil of the drive cylinder 31 via the direction control valve v3. The base side oil passage 63 is communicated with the base oil chamber 21b of the drive cylinder 21 via the direction control valve v4. The front-side oil passages 52 and 62 are communicated with each other by a communication oil passage 65 having a direction control valve v <b> 5 interposed therebetween, and a directional control valve v <b> 6 is connected to the middle of the base-side oil passage 53.

  A pilot oil passage 80 is connected to the discharge oil passage 50. The pilot oil passage 80 is branched into a pilot oil passage 81 and a pilot oil passage 82. The pilot oil passage 81 is switched to a first high / low pressure electromagnetic switch. Via the valve V1, the control oil chambers of the direction control valves v1, v2, v6 or the return oil passage 84 opened to the oil tank T are selectively switched and communicated. The pilot oil passage 82 is switched and communicated to the control oil chambers or oil tanks T of the direction control valves v3, v4, v5 via the second high / low pressure electromagnetic switching valve V2. When the pump hydraulic pressure acts on the control oil chambers of the direction control valves v1 to v6 as the pilot hydraulic pressure via the pilot oil passage 81 or the pilot oil passage 82, the valves v1 to v6 are held in a locked state.

  In the middle of the discharge oil passage 50 connected to the discharge side of the variable displacement hydraulic pump Pu, this discharge oil passage 50 is passed through a silent circuit CS (see FIGS. 7 to 12) and a reflux oil passage 101, which will be described later. A branch oil passage 100 connected to the tank T is branched, and further, a logic valve as a check valve is connected to the discharge oil passage 50 downstream of the connection portion of the branch oil passage 100, The logic valve CH prevents the hydraulic oil flowing through the discharge oil passage 50 from flowing backward from the hydraulic cylinders 21 and 31 to the hydraulic pump Pu.

  The concrete pump P is provided with detection means DE for detecting that the paired pump cylinders 20 and 30 are located immediately before the most extended position. The detection means DE is composed of first and second proximity sensors DE1 and DE2. These first and second proximity sensors DE1 and DE2 are provided at the end portions on the extension side of the hydraulic cylinders 31 and 21 (end portions on the center frame 40 side), respectively, before the limit switches 35 and 25. When the pump cylinders 30 and 20 are alternately extended, the first and second proximity sensors DE1 and DE2 are activated before the limit switches 35 and 25 are activated. When the first and second proximity sensors DE1 and DE2 are actuated to detect the extended positions of the pump cylinders 30 and 20, the detection signal is input to a silent circuit CS, which will be described later, and a solenoid in the circuit CS. The first switching valve S1 for small flow rate composed of a valve is switched to the left position (open side).

  Next, the configuration of the silent circuit CS will be described with reference to FIGS. 7 to 12. The silent circuit CS includes a first switching valve S1 for a small flow rate and a first flow valve for a large flow rate. 2 switching valve S2, 1st, 2nd control valve C1, C2 which consists of solenoid valves, and emergency valve EV which consists of on-off valves are provided. Therefore, a fixed throttle 102 is provided at the inlet port of the first switching valve S1 for small flow rate, which is connected to the branch oil passage 100.

  The silent circuit CS is connected between the branch oil passage 100 and a reflux oil passage 101 communicating with the oil tank T. The branch oil passage 100 includes a first switching valve S1 and a second switching valve S2. Are connected in parallel, and an emergency valve EV is connected to the branch oil passage 100 upstream of these switching valves S1, S2. When the emergency valve EV is switched to the right position (closed side), the silent circuit CS is shut off. The first switching valve S1 is switched by a detection signal from the detection means DE, that is, the first proximity sensor DE1 (or the second proximity sensor DE2), and the second switching valve S2 is a branched oil. The pilot hydraulic pressure from the passage 100 is switched via the first control valve C1, and the first control valve C1 is switched to the right position in response to an external control signal. The control valve C2 is switched to the right position in response to an external control signal, and the emergency valve EV is switched by the pilot hydraulic pressure from the branch oil passage 100 via the second control valve C2.

  Next, the operation of this embodiment will be described.

[When the concrete pump P is operated in the low pressure (standard pressure) pumping mode (see Figs. 3 and 5)]
As described above, this is a case where the concrete pump P is operated at a low pressure, and low-pressure (standard pressure) ready-mixed concrete is pumped from the discharge port 7 to the boom pipe 4. As a result, the turning sensor Se1 and the angle sensor Se2 are both turned off. Therefore, the solenoids SOL1 and SOL2 of the high and low pressure electromagnetic switching valves V1 and V2 are both non-excited and are in the left position as shown in FIG. At this time, pilot hydraulic pressure from the hydraulic pump P acts on the control hydraulic chambers of the directional control valves v2, v4 and v5, and these valves v2, v4 and v5 are held in a locked state. The pressure oil flows as shown by the arrows in FIG. That is, the pressure oil is pumped to the front oil chamber 21 a of the drive cylinder 21, and the oil in the front oil chamber 31 a of the drive cylinder 31 is returned to the oil tank T. The oil in the base oil chamber 21 b of the drive cylinder 21 is sent to the base oil chamber 31 b of the drive cylinder 31. Accordingly, the pump piston 32 of one pump cylinder 30 moves forward and the pump piston 22 of the other pump cylinder 20 moves backward, so that the ready-mixed concrete in the hopper 6 is sucked into the pump cylinder 20 and the fresh piston in the pump cylinder 30 is also released. Concrete is pumped from the discharge port 7 to the boom pipe 4.

  When the limit switch 35 is operated at the forward limit of the drive piston 33 of one drive cylinder 31, the signal is applied to the valve switching drive means D to switch the S-shaped valve 15, and from the valve switch drive means D to The control oil pressure is supplied to the switching valve V as a pilot oil pressure through the pilot oil passage 44, and the valve V is switched to the right side in FIG. As a result, the pressure oil from the hydraulic pump Pu can be pumped to the front oil chamber 31a of one drive cylinder 31 and the hydraulic oil in the front oil chamber 21a of the other drive cylinder 21 is returned to the oil tank T. Also, the oil in the base oil chamber 31b of one drive cylinder 31 enters the base oil chamber 21b of the other drive cylinder 21, and the pump piston 22 of the pump cylinder 20 advances and the pump cylinder 30 conversely to the case described above. Since the pump piston 32 is moved backward, the ready concrete in the hopper 6 is sucked into the pump cylinder 30 and the ready concrete in the pump cylinder 20 is pressure-fed from the discharge port 7 to the boom pipe 4. When the limit switch 25 is actuated at the forward limit of the drive piston 23 of the drive cylinder 21, the signal is applied to the valve switching drive means D to switch the S-shaped valve 15 and the control hydraulic pressure from the valve switch drive means D. Passes through the pilot oil passage 43 as pilot hydraulic pressure and is supplied to the electromagnetic switching valve V, which is again switched to the left side in FIG.

  As described above, the dredge operation of the pair of pump cylinders 20 and 30 is continued and the concrete pump P is operated. In the operation of the concrete pump P in the low pressure (standard pressure) pumping mode, as described above, the hydraulic pump Pu Is supplied to the front oil chambers 21a, 31a of the pair of drive cylinders 21, 31. Thus, the pressure receiving areas on the front oil chambers 21a, 31a side (rod side) of the drive pistons 23, 33 are smaller than the pressure receiving areas on the base oil chambers 21b, 31b side (piston side). 21 and 31 are driven at a low pressure, whereby the low-pressure ready-mixed concrete is pumped from the discharge port 7 to the boom pipe 4. Therefore, in the operation of the concrete pump P in this low pressure (standard pressure) pumping mode, the boom pipe 4 formed to be thin to reduce the weight cannot withstand the pumping pressure of the ready-mixed concrete, and is damaged or disconnected. There is no such thing as happening.

[When the concrete pump P is operated in the high-pressure pumping mode (see chain lines in FIGS. 1 and 2 and FIG. 6)]
In this case, the concrete pump P is operated at a high pressure, and the high-pressure ready-mixed concrete is pumped from the discharge port 7 to the laying pipe 10. 4), and the swing sensor Se1 and the angle sensor Se2 are both in the ON state, as shown in FIG. Since the relay circuit is closed, the solenoids SOL1 and SOL2 of both the first and second high / low pressure electromagnetic switching valves V1 and V2 are switched to the right position as shown in FIG. As a result, the pilot hydraulic pressure from the hydraulic pump Pu acts on the control hydraulic chambers of the direction control valves v1, v3 and v6, and these valves v1, v3 and v6 are held in the locked state. The pressure oil flows as shown by arrows in FIG. That is, the pressure oil is pumped to the base oil chamber 31 b of one drive cylinder 31, and the oil in the base oil chamber 21 b of the other drive cylinder 21 is returned to the oil tank T. Further, the front oil chamber 31a of the drive cylinder 31 and the front oil chamber 21a of the drive cylinder 21 are communicated with each other. As a result, the pump piston 32 of one pump cylinder 30 moves forward and the pump piston 22 of the other pump cylinder 20 moves backward, so that the ready-mixed concrete in the hopper 6 is sucked into the pump cylinder 20 and also inside the pump cylinder 30. The ready-mixed concrete is pumped from the discharge port 7 to the laying pipe 10. The limit switch 35 is actuated at the forward limit of the drive piston 33 of the drive cylinder 31, and the switching valve V is switched to the right side of FIG. 6 as described above, and this time the pressure oil from the hydraulic pump Pu is the base of the drive cylinder 21. The oil in the base oil chamber 31b of the drive cylinder 21 is returned to the oil tank T while being pumped to the oil chamber 21b. Further, the front oil chamber 21a of the drive cylinder 21 and the front oil chamber 31a of the drive cylinder 31 are communicated with each other. As a result, the pump piston 22 of the pump cylinder 21 moves forward and the pump piston 32 of the pump cylinder 31 moves backward, so that the ready concrete in the hopper 6 is sucked into the pump cylinder 30 and the ready concrete in the pump cylinder 20 is discharged. It is pumped from the outlet 7 to the laying pipe 10. When the limit switch 25 is actuated at the forward limit of the drive piston 23 of the drive cylinder 21, the signal is applied to the valve switching drive means D to switch the S-shaped valve 15, and from the valve switching drive means D to the control hydraulic pressure. Passes through the pilot oil passage 43 and switches the switching valve V to the left side in FIG. 6 again. Thus, the saddle operation of the pair of pump cylinders 20 and 30 is continued. In the operation of the concrete pump P in the high pressure pumping mode, as described above, the pressure oil from the hydraulic pump Pu is alternately supplied to the base oil chambers 21b and 31b of the pair of drive cylinders 21 and 31. In this case, the pressure receiving area of the base oil chambers 21b, 31b (piston side) of the drive pistons 23, 33 is larger than the pressure receiving area of the drive pistons 23, 33 on the front oil chambers 21a, 31a side (rod side). The pair of drive cylinders 21 and 31 are driven at a high pressure, whereby the high-pressure ready-mixed concrete from the concrete pump P is pumped from the discharge port 7 to the laying pipe 10. Therefore, in the operation of the concrete pump P in this high-pressure pumping mode, the ready-mixed concrete can be pumped efficiently at a high pressure through the laying pipe 10 that is formed to be relatively thick and has no fear of rupture.

  As described above, the concrete pump P can be automatically switched between the low pressure (standard) pumping mode and the high pressure pumping mode based on the detection of the position of the multi-stage bending boom B, that is, the detection result of the turning position and the angular position. Therefore, it is possible to prevent damage and breakage of the equipment such as damage to the boom pipe due to operator's erroneous operation and disconnection of the joint portion of the pipe, thereby improving work safety.

  In FIG. 4, the concrete pump high / low pressure switch S2 connected to the circuit 95 is provided because it is necessary to place ready-mixed concrete using the laying pipe 10 in the low pressure (standard) pumping mode. is there.

  By the way, as described above, when the concrete pump P is operated in either the low pressure (standard pressure) or the high pressure pumping mode, when each pump cylinder 30, 20 of the concrete pump P reaches the maximum extension position, the pump The pistons 32 and 22 make a loud impact sound by hitting the end walls of the pump cylinders 30 and 20, or when the pump cylinders 30 and 20 are initially extended, In this embodiment, one of the pumps is provided by the silent circuit CS connected between the branch oil passage 100 branched from the discharge oil passage 50 and the reflux oil passage 101. Before the cylinder 30 (20) reaches the maximum extension position, the extension speed is gradually reduced, and the extension speed when the other pump cylinder 20 (30) is initially extended. The impact noise in the low speed, and to allow as much as possible reduce the generation of operating noise, will now be described with reference to FIGS. 7-12 the effect of reducing noise.

  In the operating state of the concrete pump P in which the detection means DE, that is, the first proximity sensor DE1 (or the second proximity sensor DE2) is not operated, the emergency valve EV and the second control valve C2 of the silent circuit CS are always in the left position (open side). ) (See FIG. 7).

  (1) Now, when one pump cylinder 30 reaches the position immediately before the most extended end and the first proximity sensor DE1 detects this, the detection signal excites the first switching valve S1 and the first switching valve. Switch S1 to the left position (open side). Thereby, a part of the hydraulic oil from the hydraulic pump Pu flows in order from the discharge oil passage 50 → the branch oil passage 100 → the emergency valve EV → the first switching valve S1 → the oil tank T as shown by the arrows in FIG. Thus, the hydraulic oil with a small flow rate is returned to the oil tank T, and the extension operation of the pump cylinder 30 is temporarily and slowly decelerated (see FIG. 8).

  (2) After a certain time T1 has elapsed, the first control valve C1 switches from the normal position to the left position in response to the control signal. By switching the first control valve C1, the second switching valve S2 is switched to the left position (open side) in response to the pilot hydraulic pressure from the branch oil passage 100. As a result, since both the first switching valve S1 and the second switching valve S2 are in the left position (open side), most of the hydraulic oil from the hydraulic pump Pu is discharged oil passages as shown by arrows in FIG. 50 → emergency valve EV → first switching valve S1 and second switching valve S2 → the oil tank T flows in that order to return the large amount of hydraulic oil to the oil tank T. As a result, the hydraulic oil flowing to the pump cylinder 30 decreases, and the extension speed of the pump cylinder 30 is greatly reduced at a position immediately before the most extended end (see FIG. 9).

  The fixed time T1 is 0 to 1 second, and the fixed time T1 is set to be shorter as the rotational speed of the variable displacement hydraulic pump Pu is faster.

  (3) When one pump cylinder 30 reaches the maximum extension position, the S-shaped valve (oscillating pipe) 15 is switched in response to the control signal from the valve driving means D as described above, and the one pump cylinder 30 is switched. Begins to contract slowly while the other pump cylinder 20 begins to expand slowly.

  (4) After a certain time T2 has elapsed, the first control valve C1 switches to the normal position, and receives the pilot hydraulic pressure from the first control valve C1, and the second switching valve S2 switches to the right position (closed side). (See FIG. 10). As a result, the branch oil passage 100 is communicated with the oil tank T only through the first switching valve S1, and the extension speed of the other pump cylinder 20 that starts to extend at a low speed gradually increases.

  The fixed time T2 is the time after the first control valve C1 is switched in the above (2). As another modified example, the fixed time T2 indicates that the other pump cylinder 20 starts to extend. It is good also as time after detecting with a separate proximity sensor etc. and detecting the proximity sensor.

  (5) Further, when the first proximity sensor DE1 detects when the fixed time T3 has elapsed and the pump cylinder 30 is contracted, the first switching valve S1 is switched to the right position (closed side) (see FIG. 11). . As a result, the branch oil passage 100 that connects the discharge oil passage 50 and the oil tank T is shut off, and all the hydraulic oil discharged from the hydraulic pump Pu is pumped to the hydraulic cylinders 21 and 31. The pump cylinders 20 and 30 are returned to the normal operating speed.

  The noise reduction action (1) to (5) is the case where one pump cylinder 30 is extended and the first proximity sensor DE1 is detected, but the other pump cylinder 20 is extended. The same applies when the second proximity sensor DE2 is detected.

  By the way, in the noise reduction action of (1) to (5), the first switching valve S1 and the second switching valve S2 repeat the opening / closing operation every time the pump cylinders 30 and (20) reach the maximum extension position. The switching valves S1 and S2 may break down due to malfunctions due to the life of the solenoid coil or the sticking of a movable member such as a spool. In this case, the oil discharged from the hydraulic pump Pu always escapes to the oil tank T through the silent circuit CS, and the concrete pump P becomes inoperable. Therefore, when the switching valves S1 and S2 fail, the emergency valve EV is switched to the right position (closed side) by the pilot hydraulic pressure from the second control valve C2 in the normal position (see FIG. 12). It is possible to avoid the inoperability of the concrete pump P by performing the cutoff control.

  Further, the check valve CH provided on the downstream side of the branch portion of the branch oil passage 11 of the discharge oil passage 50 prevents the drive pistons 23 and 33 from self-running due to the weight of the ready-mixed concrete.

  As mentioned above, although the Example of this invention was described, this invention is not limited to the Example, A various Example is possible within the scope of the present invention.

  For example, the hydraulic pump Pu may be a constant displacement pump instead of a variable displacement pump, the check valve may be a check valve instead of a logic valve, and the second switching valve S2 is a solenoid instead of a switching valve. Further, the emergency valve may be a solenoid valve instead of the switching valve.

Overall side view of concrete pump truck 2 arrow view of FIG. Side view showing pumping condition of ready-mixed concrete by boom piping of concrete pump truck Low-high pressure pumping mode switching relay circuit diagram Hydraulic circuit diagram for low pressure pumping mode of concrete pump Hydraulic circuit diagram of high pressure pumping mode of concrete pump Silent circuit diagram Silent circuit diagram Silent circuit diagram Silent circuit diagram Silent circuit diagram Silent circuit diagram Operation flow chart of silent circuit

Explanation of symbols

6 ·················· 20 ······················································································· .... Branch oil passage CH ... Check valve CS ... Silent circuit DE ... Detection means S1 ... ...... First switching valve S3 ......... Second switching valve Pu ...... Hydraulic pump T ...... Oil tank

Claims (4)

In the piston-type concrete pump configured to pump the ready-mixed concrete in the hopper (6) by a pair of pump cylinders (20, 30) and the dredging operation of these pump cylinders (20, 30),
Detection means (DE) for detecting that each pump cylinder (20, 30) is immediately before the maximum extension position;
A branched oil passage branching from a discharge oil passage (50) connecting the hydraulic pump (Pu) and the pair of pump cylinders (20, 30), and communicating the discharge oil passage (50) to an oil tank (T) ( 100)
A silent circuit (CS) interposed in the middle of the branch oil passage (100) for controlling opening and closing of the branch oil passage (100),
The piston-type concrete pump is characterized in that when the detecting means (DE) detects when the pump cylinders (20, 30) are extended, the silent circuit (CS) is controlled to be opened. Control device.   2. The silent circuit (CS) is controlled to be switched to a closed side when the detection means (DE) detects when the pump cylinders (20, 30) are contracted. Piston type concrete pump control device.   The silent circuit (CS) includes a first switching valve (S1) and a second switching valve (S2) arranged in parallel, and these valves (S1, S2) include the branch oil passage (100) and an oil tank. (T) is opened and closed separately, and the passing flow rate when the second switching valve (S2) is opened is larger than the passing flow rate when the first switching valve (S1) is opened, and the pump cylinder ( 20, 30) when the detection means (DE) detects it, the first switching valve (S1) is opened and then the second switching valve (S2) is opened. The control device for a piston-type concrete pump according to claim 1 or 2. On the discharge oil passage (50) connected to the discharge side of the hydraulic pump (Pu), on the downstream side of the connection portion with the branch oil passage (100), from the pump cylinder (20, 30) side. 4. The control device for a piston-type concrete pump according to claim 1, wherein a check valve (CH) for preventing the hydraulic oil from flowing backward is connected to the hydraulic pump (Pu) side. .

Images