JP5576764B2 - Drum rotating device - Google Patents

Description

The present invention relates to an improvement of a drum rotating device that controls the rotation of a drum of a mixer truck.

  In general, an agitator truck called a mixer truck includes a drum that is rotatably mounted on a pedestal for transporting concrete produced in a concrete plant to a placement site.

  This drum includes a cylindrical drum shell and a spiral blade whose outer peripheral portion is fixed to the inner surface of the drum shell, and is similarly driven by a drum rotating device mounted on the mixer truck. The drum rotating device includes a hydraulic pump driven by an engine of the mixer vehicle and a hydraulic motor rotated by pressure oil sent from the hydraulic pump, and connects an output shaft of the hydraulic motor to the drum.

  When putting concrete into the drum, the drum is rotated forward so that the blade feeds the concrete to the back of the drum. Conversely, when discharging concrete from the drum, The concrete is pushed back to the drum opening end with a blade so as to be rotated in the reverse direction and discharged. Further, when the concrete is kneaded in order to uniformly disperse aggregates such as gravel in the mortar in the concrete, the drum is rotated forward and the concrete in the drum is stirred by the blade.

  Although these operations can be performed by the operator in the cab of the mixer vehicle, it is necessary to perform the operation while confirming the rotation state of the drum. An adjustment lever that adjusts the number of rotations per unit time is provided, and the operator can adjust the rotation speed of the drum by operating the adjustment lever.

  Specifically, the adjustment lever is connected to a governor that adjusts the rotation speed of the engine. When the rotation speed of the engine is adjusted by the adjustment lever, the rotation of the hydraulic pump connected to the engine via a PTO (Power Take Off). The speed is also adjusted in proportion to the rotational speed of the engine. Since the discharge flow rate of the hydraulic pump is proportional to the rotation speed and the rotation speed of the hydraulic motor is proportional to the discharge flow rate of the hydraulic pump, if the engine rotation speed is increased by operating the adjustment lever, the rotation speed of the hydraulic motor is also proportional to this. On the contrary, if the engine speed is decreased, the rotational speed of the hydraulic motor is also decreased in proportion to this.

Japanese Utility Model Publication No. 07-4158

  By the way, when the concrete viscosity is relatively low, since the torque for rotating the drum is small, the discharge pressure of the hydraulic pump is also small, so if the capacity of the hydraulic motor is reduced accordingly, the drum is rotated at high speed. However, as described above, in the conventional drum rotation device, the drum rotation speed and the engine rotation speed are in a one-to-one relationship, so that the drum rotates at high speed. If you want to make it happen, you can only increase the engine speed.

  Therefore, in the conventional drum rotating device, when the drum is rotated at a high speed, the rotational speed of the engine must be constantly increased, so that energy is wasted and engine noise is generated.

  Accordingly, the present invention was devised to improve the above-described problems, and an object of the present invention is to provide a drum rotating device that can save energy and suppress the generation of engine noise. That is.

  In order to achieve the above object, the problem-solving means of the present invention is a hydraulic motor that is mounted on a mixer vehicle so as to be rotatable and rotationally drives a drum in two stages, and is driven by the engine of the mixer vehicle. In a drum rotating apparatus including a hydraulic pump that supplies pressure oil to a motor, a changing mechanism that changes the tilt angle of the hydraulic motor, and an adjustment lever that adjusts the engine rotation speed, the changing mechanism is connected via a signal line. When the signal from the signal source is input, it is set to reduce the capacity of the hydraulic motor, and a first switch and a second switch are provided in the middle of the signal line. It is set to close when it is within the adjustment range from the idling speed to a predetermined speed lower than the upper limit speed corresponding to the upper limit of the drum speed. Switch is characterized in that the discharge pressure of the hydraulic pump is set to close to or less than a predetermined threshold value.

  According to the present invention, when the concrete viscosity is low, the capacity of the hydraulic motor can be reduced, and the hydraulic motor can be rotated at a high speed without rotating the engine at a high speed. Since the rotation speed of the drum can be set to an allowable upper limit rotation speed without rotating within a range up to a predetermined rotation speed, energy consumption can be reduced and noise generated by the engine can be suppressed. .

1 is a system diagram of a drum rotating device according to an embodiment. It is a figure explaining the operation mode of the drum rotating apparatus of one embodiment. It is a system diagram of a drum rotating device according to a modification of the embodiment. It is the schematic of the solenoid of the drum rotating apparatus in one modification of one Embodiment.

  The present invention will be described below based on the illustrated embodiment. As shown in FIG. 1, a drum rotating apparatus 1 according to an embodiment is basically a hydraulic motor M having a variable capacity in two stages that is rotatably mounted on a mixer car (not shown) and rotationally drives a drum D. A hydraulic pump P that is driven by the engine E of the mixer vehicle and supplies pressure oil to the hydraulic motor M, a change mechanism T that changes the tilt angle of the swash plate 17 of the hydraulic motor M, and an engine rotational speed. And an adjustment lever L.

  The hydraulic pump P is connected to the engine E of the mixer vehicle via the PTO, and is rotated by the rotational motion of the crankshaft of the engine E being transmitted. The hydraulic pump P is driven at a rotational speed corresponding to the rotational speed of the engine E, and supplies pressure oil to the hydraulic motor M via the loop-shaped pipe line 10.

  A direction switching valve 11 is provided in the middle of the pipe line 10. The direction switching valve 11 includes an unload position 11a for returning the pressure oil discharged from the hydraulic pump P to the suction port of the hydraulic pump P, and a hydraulic motor. A communication position 11b for supplying pressure oil to the pipeline 10 so as to rotate M in the forward direction and a communication position 11c for supplying pressure oil to the pipeline 10 so as to rotate the hydraulic motor M in the reverse direction are provided. Thus, it is possible to switch to each position by operating the switching lever 11d.

  A relief pipe 12 is provided in the middle of the pipe 10 in parallel with the hydraulic motor M. The relief pipe 12 is opened in the middle of the relief pipe 12 when the pressure on the pipe 10 side becomes the relief pressure. Relief valves 13 and 14 are provided, and are connected to a tank 15 in the middle of the relief pipe 12 and between the relief valves 13 and 14. That is, when the pressure in the pipe line 10 becomes equal to or higher than the relief pressure, the relief valves 13 and 14 are opened to release the pressure to the tank 15 and protect the hydraulic circuit in the drum rotating device 1.

  The hydraulic circuit in the drum rotating device 1 includes a charge pump 16 in addition to the hydraulic pump P. The charge pump 16 draws hydraulic oil from the tank 15 and supplies pressure oil to the conduit 10. The pressure oil is stably supplied to the pipe line 10 so that the discharge flow rate does not become insufficient even when the rotation speed of the hydraulic pump P is low by assisting the hydraulic pump P.

  The hydraulic motor M is a variable displacement hydraulic motor in which the tilt angle of the swash plate 17 can be switched in two stages. In the state where the swash plate 17 is illustrated, the capacity is large, and the swash plate 17 However, when it rotates counterclockwise in FIG. 1, the capacity decreases. In other words, the hydraulic motor M is configured such that, if the discharge flow rate of the hydraulic pump P does not change, the rotational speed increases when the capacity is reduced, and the rotational speed decreases when the capacity is increased.

  The changing mechanism T that changes the tilt angle of the swash plate 17 of the hydraulic motor M includes a pair of cylinders 18 and 19 coupled to the swash plate 17 respectively, and a spring 20 that urges the cylinders 18 and 19 in the compression direction. A switching valve 21 for selectively switching the supply of pressure oil to the cylinders 18 and 19 and the discharge of hydraulic oil from the cylinders 18 and 19 and a control valve 22 for switching the switching valve 21 are provided.

  Although not shown, each of the cylinders 18 and 19 includes a cylinder, a piston that is inserted into the cylinder, and a rod that connects the piston and the swash plate 17. The hydraulic oil is discharged from the cylinders 18 and 19. In this state, the urging force of the spring 20 causes the cylinders 18 and 19 to be contracted to position the swash plate 17 at the position shown in FIG. 1, and the capacity of the hydraulic motor M increases. On the contrary, when the hydraulic oil is supplied into the cylinders 18 and 19 to extend, the swash plate 17 is pressed counterclockwise in FIG. 1 to change the tilt angle of the hydraulic motor M, thereby reducing the capacity of the hydraulic motor M. It is supposed to be. That is, the hydraulic motor M is a variable displacement hydraulic motor whose capacity is changed in two stages by the changing mechanism T.

  The switching valve 21 is in the middle of the pipe line 10 and is supplied from the upstream of the hydraulic motor M to a supply position 21b for supplying pressure oil to one of the cylinders 18 and 19, and a discharge communicating with the tank 15 in the cylinders 18 and 19. A valve body 21a having a position 21c and a spring 21d for energizing the valve body 21a so as to take a discharge position 21c are provided, and a switching operation is performed by hydraulic pressure from the control valve 22. That is, when the pilot pressure is supplied from the control valve 22, the valve body 21a is pressed and the spring 21d is contracted, so that the switching valve 21 takes the supply position 21b and expands one of the cylinders 18 and 19. Accordingly, the capacity of the hydraulic motor M is reduced, and conversely, when the hydraulic pressure from the control valve 22 is interrupted, the valve body 21a is energized by the spring 21d, so that the switching valve 21 adopts the discharge position 21c and the cylinder 18 , 19 are communicated with the tank 15, and the swash plate 17 is pressed by the urging force of the spring 20 to take an inclination angle that increases the capacity of the hydraulic motor M.

  In this case, the control valve 22 supplies the hydraulic pressure supplied from the charge pump 16 as a pilot pressure to the switching valve 21 via the pilot passage 23, and switches the switching valve 21 to the supply position 21b. A valve body 22a having an off position 22c for communicating the pilot passage 23 with the tank 15 so that the pilot pressure does not act on the spring, a spring 22d for biasing the valve body 22a so as to adopt the off position 22c, and a spring when energized. The solenoid valve is composed of a valve drive solenoid 22e that exerts an urging force facing 22d to switch the valve body 22a to the on position 22b.

  The valve drive solenoid 22e is connected to the power source Bat via the signal line 30. When a signal is input from the signal line 30, that is, in this case, the control valve 22 is turned on. Switching to 22b, the switching valve 21 switches to the supply position 21b, and the tilt angle of the swash plate 17 of the hydraulic motor M is changed to reduce the capacity. On the other hand, if no signal is input to the valve drive solenoid 22e, that is, in this case, no power is supplied, the control valve 22 is switched to the off position 22c, the switching valve 21 is switched to the discharge position 21c, and the hydraulic motor M The tilt angle of the swash plate 17 is changed to increase the capacity.

  As described above, the changing mechanism T reduces the capacity of the hydraulic motor M when a signal from the power source Bat as a signal source is input, and increases the capacity of the hydraulic motor M when no signal is input from the power source Bat. It is supposed to be.

  Subsequently, the rotational speed of the engine E is adjusted by the governor G, and the governor lever 3 of the governor G is connected to the adjusting lever L swingably attached to the mixer vehicle via the link mechanism 4. ing. By operating the adjusting lever L, the rotational speed of the hydraulic pump P to which the rotational motion of the engine E is transmitted can be adjusted.

  The adjustment lever L is provided with an arc-shaped detected plate 5 along the rotation direction of the adjustment lever in the middle. The adjustment lever L is located in the traveling mode as shown in FIG. In turn, the dead zone a, the low and medium speed range b from the idling rotation speed to the predetermined rotation speed, the high speed area c exceeding the predetermined rotation speed range and the upper limit rotation speed corresponding to the upper limit of the drum rotation speed. The engine speed can be adjusted. Since the rotational motion of the engine E is transmitted to the hydraulic pump P through the above-described PTO, if the engine rotational speed is increased, the hydraulic pump P also increases the rotational speed accordingly and the discharge flow rate increases. If the capacity of the hydraulic motor M does not change, the rotational speed of the hydraulic motor M also increases. Conversely, if the engine rotational speed is slowed down, the discharge flow rate of the hydraulic pump P also decreases, and if the capacity of the hydraulic motor M does not change, the rotational speed of the hydraulic motor M slows down.

  When the adjustment lever L is in the travel mode, the engine rotation speed is controlled by an electronic governor (not shown) that is higher than the governor G. Further, when the adjustment lever L is within the range of the low / medium speed range b, the engine rotation speed can be adjusted within the range from the rotation speed in the idling state to a predetermined rotation speed, for example, about 1250 rpm, at the position of the adjustment lever L. When the adjustment lever L is within the range of the high speed range c, the upper limit rotation speed corresponding to the drum rotation speed upper limit at the position of the adjustment lever L and corresponding to the upper limit of the drum rotation speed, for example, 1250 rpm to It is possible to adjust the engine rotation speed in a range up to 2500 rpm. The upper limit of the drum rotation speed is about 18 rpm, and it may be set to an engine rotation speed that realizes the drum rotation speed of 18 rpm with the capacity of the hydraulic motor M increased. In the case of a diesel engine that is used, it is suitable for generating a relatively large torque in the rotational speed range of 1500 rpm to 2500 rpm and is suitable for rotating the drum rotational speed at a high speed, and if the upper limit rotational speed is set too high, the noise becomes excessive. For this reason, the range of the high speed region c is set to 1250 rpm to 2500 rpm, but is not limited to the above. The predetermined rotational speed is lower than the upper limit rotational speed and can be arbitrarily set in consideration of the upper limit rotational speed. However, the predetermined rotational speed is set to such a degree that noise of the engine E does not cause a problem. The

Returning, in the middle of the signal line 30, a proximity switch 31 as a first switch and a relay switch 32 as a second switch are provided. Note that the order in which the proximity switch 31 as the first switch and the relay switch 32 as the second switch are installed on the signal line 30 may be reversed. When the adjustment lever L is in the range of the low / medium speed range b, the proximity switch 31 is opposed to the detection plate 5 and detects the approach of the detection plate 5, and is detected by the sensor unit 31 a . When an approach of the plate 5 is detected, a switch portion 31b that is turned on and closes is provided. That is, when the adjustment lever L is within a range for adjusting the engine rotation speed from the rotation speed in the idling state to the predetermined rotation speed, the adjustment lever L is turned on. When the detection plate 5 is made of metal, the proximity switch 31 may be a proximity switch such as an induction type, capacitance type, ultrasonic type, or photoelectric type, and the detection plate 5 is non-metallic. In this case, a proximity switch such as a capacitance type, an ultrasonic type, or a photoelectric type may be used.

  Further, in order to detect the discharge pressure of the hydraulic pump P, a pressure sensor 33 is provided in the middle of the pipe line 10 and between the hydraulic pump P and the direction switching valve 11. The pressure sensor 33 outputs a voltage corresponding to the discharge pressure of the hydraulic pump P. Further, an amplifier 34 is provided for energizing the relay switch 32 when the pressure output from the pressure sensor 33 becomes a predetermined threshold value or less. The relay switch 32 is turned on and closed when energized by the amplifier 34, and is opened and opened when there is no power. That is, the relay switch 32 as the second switch is closed when the discharge pressure of the hydraulic pump P is equal to or lower than a predetermined threshold value.

  The discharge pressure of the hydraulic pump P is proportional to the torque when the drum D is rotated. However, if the concrete viscosity in the drum D is low, the torque required to rotate the drum D becomes small. That is, the approximate viscosity of the concrete in the drum D can be determined depending on the discharge pressure of the hydraulic pump P, and when the viscosity is low, the torque required to rotate the drum D is small. The rotational speed of the hydraulic motor M can be increased by reducing the capacity of the hydraulic motor M without increasing the discharge flow rate of P. Therefore, when the concrete viscosity is a value that does not prevent the hydraulic motor M from rotating at a high speed by reducing the capacity of the hydraulic motor M, the capacity of the hydraulic motor M may be reduced. In the invention, in order to judge this, the discharge pressure of the hydraulic pump P is compared with a predetermined threshold value. Therefore, the predetermined threshold may be determined based on the discharge pressure of the hydraulic pump P when the concrete viscosity is such that the hydraulic motor M can be rotated at a high speed by reducing the capacity of the hydraulic motor M. In the embodiment, specifically, 9 MPa.

  That is, in the drum rotating device 1 of this embodiment, the adjustment lever L is in a position where the engine rotation speed is adjusted within a predetermined rotation speed from the rotation speed in the idling state, and the proximity switch 31 is turned on, and the pressure sensor When the discharge pressure of the hydraulic pump P detected at 33 is equal to or lower than a predetermined threshold value, the relay switch 32 is turned on, and a signal from the power source Bat as a signal source is input to the control valve 22 via the signal line 30. The tilt angle of the swash plate 17 of the hydraulic motor M is controlled so as to reduce the capacity of the hydraulic motor M.

  Therefore, as shown in FIG. 2, the operation mode of the drum rotating device 1 of this embodiment is as follows. When the adjustment lever L is in the low / medium speed range b and the concrete viscosity is low, the hydraulic motor M Therefore, the hydraulic motor M can be rotated at high speed without rotating the engine at high speed. In this operation mode, the position of the adjusting lever L is kept in the low / medium speed range b, that is, the drum D is not rotated at high speed by keeping the engine rotational speed within the range from the idling rotational speed to the predetermined rotational speed. Therefore, the energy consumption can be reduced and the noise generated by the engine E can be suppressed.

  In addition, when the concrete viscosity is high, if the capacity of the hydraulic motor M is reduced, the discharge pressure of the hydraulic pump P exceeds the relief pressure, and a sufficient pressure cannot be sent to the hydraulic motor M. In order to drive the rotation of D, a shortage of torque is caused. In this case, a sufficient torque can be secured without reducing the capacity of the hydraulic motor M, thereby preventing the rotation failure of the drum D.

  In this embodiment, even if the concrete viscosity is low, if the adjusting lever L exceeds the predetermined rotational speed and is positioned in the high speed range c, the engine rotational speed becomes high and the capacity of the hydraulic motor M is increased. If the value is kept small, the maximum rotational speed of the drum D may be increased, and the concrete may not be properly kneaded, discharged, or charged. Therefore, the capacity of the hydraulic motor M is increased. It is possible to prevent the rotation speed of the drum D from becoming excessive.

  Further, as described above, the amplifier 34 supplies power to the relay switch 32 and turns on the relay switch 32 when the pressure sensor 33 detects a pressure equal to or lower than a predetermined threshold, but the relay switch 32 supplies power. When the operation is sometimes off, the pressure sensor 33 may be set to supply power to the relay switch 32 when detecting a pressure exceeding a predetermined threshold. In addition, the proximity switch 31 is used to open and close the first switch according to the position of the adjustment lever L in a mixer vehicle having a severe use environment, but the position of the adjustment lever L is in the low / medium speed range b. Therefore, the first switch is not limited to the proximity switch, and is set so as to be turned on / off depending on the position of the governor lever 3 or the link mechanism 4 of the governor G. The second switch is not limited to the relay switch.

  Next, a drum rotating device 40 according to a modification of the embodiment will be described. The drum rotating device 40 is configured such that when the concrete viscosity is low, the operation of the adjusting lever L is restricted so that the adjusting lever L cannot be operated to a range where the engine speed exceeds a predetermined rotational speed. Different from the drum rotating device 1 of the above-described embodiment. Specifically, as shown in FIG. 3, the configuration of the drum rotating device 1 according to the above-described embodiment includes a self-holding solenoid S that can be expanded and contracted, a stopper 41 that is driven by the solenoid S, and a signal. A first coil excitation line 42 and a second coil excitation line 43 branched from the line 30 and a relay switch 44 as a third switch provided in the middle of the second coil excitation line 43 are additionally provided.

  As shown in FIG. 4, the solenoid S includes a solenoid body 50, a plunger 51 that holds the stopper 41 and is inserted into the solenoid body 50 so as to be movable in the axial direction, and is attached to the solenoid body 50 at both ends of the plunger 51. A first coil 52 and a second coil 53 are provided respectively on the outer peripheral side. When the first coil 52 is excited, the plunger 51 is attracted by the electromagnetic force of the first coil 52, as indicated by the broken line in FIG. When the stopper 41 protrudes outward from the solenoid body 50 and extends to excite the second coil 53, the plunger 51 is attracted by the electromagnetic force of the second coil 53, so that the stopper 41 is indicated by a solid line in FIG. The solenoid body 50 is retracted and contracted. Further, in a state where the first coil 52 and the second coil 53 are not energized, the plunger 51 is held in its position by a magnet (not shown), and the solenoid S is a self-holding solenoid. Yes.

  As shown in FIGS. 3 and 4, the solenoid S is within the swing range of the adjustment lever L, and when the stopper 41 is extended and protrudes from the solenoid body 50, the adjustment lever L is rotated at the engine speed. The stopper 41 is provided at a position where it comes into contact with the left side surface of the adjustment lever L in FIG. Therefore, when the solenoid S is extended, even if the adjustment lever L is operated clockwise in FIG. 3 from the low / medium speed range b to the high speed range c, the stopper 41 collides with the adjustment lever L, The movement can be restricted so that the adjustment lever L cannot be operated to the high speed range c side. On the other hand, when the solenoid S is in the contracted state and the stopper 41 is pulled into the solenoid body 50 as indicated by a solid line in FIG. 4, the adjustment lever L is not restricted at all by the stopper 41. Thus, the adjustment lever L can be operated to all positions within the swingable range.

  Further, one end of the first coil 52 is grounded, and the other end is in the middle of the signal line 30 and is downstream of the proximity switch 31 as the first switch and the relay switch 32 as the second switch. It is connected to a first coil excitation line 42 branched from the valve 22 side. On the other hand, one end of the second coil 53 is installed, and the other end is in the middle of the signal line 30 and is upstream of the proximity switch 31 as the first switch and the relay switch 32 as the second switch. It is connected to a second coil excitation line 43 branched from the Bat side.

  Further, a relay switch 44 as a third switch is provided in the middle of the second coil excitation line 43, and this relay switch 44 is used when the pressure output from the pressure sensor 33 falls below a predetermined threshold value. It is connected to the amplifier 34 to be supplied, and is turned off when the amplifier 34 is energized, and is turned on and closed when there is no electricity. That is, the operation is reverse to that of the relay switch 32 as the second switch. As described above, when the pressure detected by the pressure sensor 33 exceeds a predetermined threshold, the amplifier 34 is set to energize the relay switch 32, and the relay switch 32 is turned off when power is supplied. The relay switch 44 may be set to turn on when energized.

Therefore, when the adjustment lever L is operated from the running mode beyond the dead zone a to the low / medium speed range b from the idling rotational speed to the predetermined rotational speed, the pressure detected by the pressure sensor 33 is less than the predetermined threshold value. If it is, the second coil 53 is not excited relay switch 44 as a third switch is turned off, the by the proximity switch 31 is a relay switch 32 as a second switch is turned on is turned on One coil 52 is excited. Then, the solenoid S is extended, and the operation of the stopper 41 to the high speed range c of the adjustment lever L is restricted. Therefore, in this case, the engine rotation speed is limited to a predetermined rotation speed or less. In this case, since both the relay switch 32 and the proximity switch 31 are turned on, the control valve 22 is energized to reduce the capacity of the hydraulic motor M as in the drum rotating device 1 of the embodiment. . In other words, in this case, a state pressure detected is lower concrete viscosity be less than a predetermined threshold value by the pressure sensor 33, similarly to the drum rotation device 1 of the embodiment, the position of the adjusting lever L The upper limit rotational speed that allows the rotational speed of the drum D to be maintained while maintaining the low and medium speed range b, that is, without causing the engine rotational speed to fall within a range from the rotational speed in the idling state to a predetermined rotational speed Energy consumption can be reduced and noise generated by the engine E can be suppressed.

  Further, in this embodiment, when the concrete viscosity is low, the stopper 41 restricts the swing of the adjustment lever L, and the adjustment lever L is set to a range in which the engine rotation speed exceeds the predetermined rotation speed. Can be prevented by the stopper 41 even if the operator mistakenly operates the adjusting lever L to increase the engine rotational speed, thereby reducing energy consumption and suppressing engine E noise. Can be ensured.

  On the other hand, when the pressure detected by the pressure sensor 33 exceeds a predetermined threshold value, the relay switch 44 as the third switch is turned on, the second coil 53 is excited, and the relay switch 32 as the second switch is activated. Since the first coil 52 is turned off and the first coil 52 is not excited, the solenoid S contracts and the stopper 41 does not prevent the adjustment lever L from swinging. In this case, since the relay switch 32 is turned off and the control valve 22 is not energized, the capacity of the hydraulic motor M is increased as in the drum rotating device 1 of the embodiment. That is, in this case, since the pressure detected by the pressure sensor 33 exceeds the predetermined threshold value and the concrete viscosity is high, the swinging operation of the adjustment lever L is not limited, and the capacity of the hydraulic motor M is increased. By doing so, sufficient torque is secured, and the occurrence of defective rotation of the drum D is prevented.

  As in the embodiment, a switch other than the proximity switch 31 can be used as the first switch, and a switch other than the relay switch can be used as the second switch and the third switch. is there.

  Further, the changing mechanism T in each of the above embodiments is not limited to the above-described configuration, and the tilt angle of the swash plate 17 can be changed so as to reduce the capacity of the hydraulic motor M when a signal is input. For example, an electric actuator may be used.

  This is the end of the description of the embodiment of the present invention, but the scope of the present invention is of course not limited to the details shown or described.

  The present invention can be applied to a drum rotating device that rotationally drives the drum of the mixer truck of the present invention.

DESCRIPTION OF SYMBOLS 1,40 Drum rotating device 3 Governor lever 4 Link mechanism 5 Detected plate 10 Pipe 11 Direction switching valve 11a Unload position 11b in direction switching valve, 11c Communication position 11d in direction switching valve 13, 14 Relief valve 15 Tank 16 Charge pump 17 Swash plate 18, 19 Cylinder 20 Spring 21 Switching valve 21a Valve body 21b in switching valve Supply position 21c in switching valve Discharge position 21d in switching valve Spring 22 in switching valve Control valve 22a Control Valve body 22b in valve On-position 22c in control valve Off-position 22d in control valve Spring 22e in control valve Valve drive solenoid 23 in control valve Pilot passage 30 Signal line 31 Near as first switch Switch 31a Sensor unit 31b Switch unit 32 Relay switch 33 as second switch Pressure sensor 34 Amplifier 41 Stopper 42 First coil excitation wire 43 Second coil excitation wire 44 Relay switch 50 as third switch Solenoid body 51 in solenoid 51 Plunger in solenoid 52 1st coil in solenoid 53 2nd coil Bat in solenoid Power source D as signal source Drum E Engine G Governer L Adjustment lever M Hydraulic motor P Hydraulic pump S Solenoid T Change mechanism

Claims (4)

  A hydraulic motor with variable capacity in two stages that is rotatably mounted on the mixer car and rotationally drives the drum, a hydraulic pump that is driven by the engine of the mixer car and supplies pressure oil to the hydraulic motor, and a tilt angle of the hydraulic motor In the drum rotating device having the changing mechanism for changing the speed and the adjusting lever for adjusting the engine rotation speed, the changing mechanism reduces the capacity of the hydraulic motor when a signal from the signal source is input via the signal line. The first switch and the second switch are provided in the middle of the signal line, and the first switch has an adjustment lever that changes the engine rotation speed from the rotation speed in the idling state to the upper limit rotation speed corresponding to the upper limit of the drum rotation speed. The second switch is set to close when it is within the range to be adjusted to a low predetermined rotational speed, and the discharge pressure of the hydraulic pump is below a predetermined threshold Close the drum rotating device, characterized in that it is set to. It has a self-holding solenoid that expands by energizing the first coil and contracts by energizing the second coil, and a stopper driven by the solenoid, and the side of the adjustment lever abuts the stopper when the solenoid is extended Then, a stopper mechanism that prevents the adjustment lever from being rotated to a range where the engine rotation speed is equal to or higher than the predetermined rotation speed is provided. The first coil is energized when the first switch and the second switch are closed , and the second coil The drum rotating device according to claim 1, wherein the drum rotating device is energized when a discharge pressure of the hydraulic pump exceeds the predetermined threshold . The adjustment lever is swingably attached to the mixer vehicle, and an arc-shaped detection plate is provided on the adjustment lever. The first switch adjusts the engine rotation speed from the idling rotation speed to the predetermined rotation speed. The drum rotating device according to claim 1, wherein the drum rotating device is a proximity switch that performs a switch operation by the approach of the detected object when facing the detected plate when within the range to be adjusted. The signal line is branched into a second coil excitation line connected to the second coil and a first coil excitation line connected to the first coil from the upstream side in the middle of the change mechanism downstream, and the signal line The first switch and the second switch are provided between the second coil excitation line and the first coil excitation line, and the discharge pressure of the hydraulic pump exceeds the predetermined threshold value in the middle of the second coil excitation line. The drum rotating device according to claim 2, wherein a third switch is provided for closing.

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