JP2000094432A - Driving controlling method for mixer drum driven by engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving controlling method, which can prevent an engine from being overloaded by a mixer drum and can rotate the mixer drum in response to a manipulated variable. SOLUTION: In a rotatively driving of a mixer drum 2 connected with a constant displacement type oil hydraulic motor 4 rotated through the discharging of a variable displacement type oil hydraulic pump 6, which is rotated by an engine 5 and the discharging amount of which is controlled by a solenoid proportional directional control valve 9, an electric controller 18 electrically controls the solenoid proportional directional control valve so as to bring the discharge amount of the variable displacement type oil hydraulic pump to zero when the rotational frequency of the engine becomes below a set value. Thus, when the engine stops due to overloading, a restarting can be performed under the state that the load of the mixer drum is automatically removed, resulting in eliminating a fear of the rotation of the mixer drum at its restarting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control method for a mixer drum such as a concrete mixer truck or a kneader driven by an engine.

[0002]

2. Description of the Related Art Conventionally, a mixer drum of a concrete mixer truck is driven by a traveling engine of a vehicle. The traveling engine rotates a variable displacement hydraulic pump, and discharges oil from the pump to a fixed displacement hydraulic pump. It supplies a motor and rotates a mixer drum connected to the hydraulic motor via a speed reducer. Since the rotation speed of the variable displacement hydraulic pump changes greatly depending on the rotation speed of the engine which changes depending on the running state, the discharge amount of the pump is controlled so that the rotation speed of the mixer drum does not change significantly. Generally, the pump has a swash-shaft or swash-plate type equipped with a pump control unit including a spring center type tilt cylinder for controlling the discharge amount and a proportional directional control valve for controlling the supply of hydraulic pressure to the cylinder. The piston pressure of the pilot pump driven by the engine is controlled by operating the proportional directional control valve manually or simultaneously with the manual operation based on the detected value of the rotation speed of the hydraulic motor. It leads to a tilt cylinder via a proportional directional control valve, which performs an operation of changing the tilt angle of the pump. As the proportional directional control valve of the pump control unit, a hydraulic type or an electromagnetic type is used. In the case of manual operation, the operating lever is operated to control the hydraulic pressure or current acting on the proportional directional control valve. The proportional directional control valve moves to a predetermined operating position. Even if the proportional directional control valve is at a predetermined position, if the engine rotational speed increases or decreases, the pump discharge amount increases or decreases and the rotational speed of the mixer drum increases or decreases. In the electric controller, the detected value of the rotation speed of the hydraulic motor is calculated as a current value for manual operation. When the engine speed is low, the tilt angle of the pump is large, and when the engine speed is high, the tilt angle is large. By controlling the angle to be small, the mixer drum is controlled to rotate within a substantially constant range.

[0003]

The rotating state of the mixer drum is a normal rotation state in which the ready-mixed concrete is kneaded at a low speed and at a constant speed so as to prevent separation of moisture and concrete during transportation. There are a reverse rotation state in which it is lowered and a drum rotation stop state, and the state is switched by an operation lever.

[0004] During transportation, the operation lever is operated in the normal rotation state. In such a case, if the running engine is stopped for parking or the like and then the engine is restarted as it is, the pump has a flow rate having a tilt angle. In the discharge state, the load torque at the time of restarting is increased by the amount corresponding to the rotation of the concrete mixer, so that a greater force is required than at the time of normal engine startup, and the mixer drum is disadvantageously abruptly started. Therefore, conventionally, it has been necessary to perform a troublesome operation in which the operator manually returns the operation lever to the rotation stop state at the time of restart. To avoid this annoyance,
The pump can be provided with a special mechanism for automatically returning the tilt angle of the pump to the neutral position when the engine is stopped. This special mechanism is realized by the tilt cylinder and the proportional directional control valve. Combined with these, the spring force and the pressure of a fixed displacement charge pump that is rotated by the traveling engine are applied to them, and if the operation lever is operated to a specific position, the pressure will be reduced when the engine stops. The tilting cylinder is actuated by the spring force to return the tilting angle to the neutral position, but in other operating positions of the operating lever, this operation is performed unless the hydraulic system of the tilting cylinder is overloaded. Cannot be performed and the tilt angle cannot be returned to the neutral position arbitrarily. For example, there is a problem that the engine stops when the running system is overloaded with a mixer truck on an uphill road or the like. It was easy to.

[0005] Further, in a type in which an electric controller performs correction control so that the number of revolutions of the mixer drum is within a predetermined range, the tilt cylinder operates so that the pump discharges maximum in the forward direction of the pump. When the proportional directional control valve is operated to reverse the pump suddenly and perform maximum discharge while the rotor is rotating forward at the maximum speed, and if the rotation direction of the mixer drum is not detected, Since the maximum discharge state is apparently the same as that at the time of normal rotation, the pump control unit does not perform the correction operation even if the rotation speed of the mixer drum decreases, and the rotation amount of the mixer drum is reduced by the manual operation amount of the proportional directional control valve. There was an inconvenience that the numbers did not follow. Further, when the mixer drum is rotated at a very low speed, there is a disadvantage that an uneven load is applied to the mixer drum due to an uneven load in the drum and the rotation of the drum does not follow the manual operation.

Further, when the drum is to be stopped suddenly, due to the internal leakage of the hydraulic equipment and the bias of the load, a slight delay is caused to the stop operation, or the biased load falls in the drum after the drum is stopped. There was a problem that the drum would move in some cases.

An object of the present invention is to provide a drive control method capable of preventing the engine from being overloaded by the mixer drum and rotating the mixer drum in accordance with the operation amount.

[0008]

According to the present invention, there is provided a variable displacement hydraulic pump which is rotated by an engine and controls the pump discharge amount by an electromagnetic proportional directional control valve, and a fixed displacement which is rotated by discharge of the hydraulic pump. Type hydraulic motor,
A method of controlling the operation of the mixer drum by connecting a mixer drum to the hydraulic motor via a speed reducer and controlling the operation of the electromagnetic proportional directional control valve by an electric controller to control the discharge rate of the pump. The above object is achieved by controlling the electromagnetic proportional directional control valve by an electric controller so that the discharge amount of the variable displacement hydraulic pump becomes zero when the engine speed becomes equal to or less than a set value. I made it. Preferably, the rotational speed and the rotational direction of the fixed displacement hydraulic motor are detected by a rotary encoder, and the detected value is corrected so that the control value from the electric controller to the electromagnetic proportional directional control valve is constant.
Detecting the number of rotations of the fixed displacement hydraulic motor at a small rotation phase angle is advantageous in improving control accuracy.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a closed hydraulic circuit for driving a mixer drum 2 of a concrete mixer truck. The hydraulic motor 4 is connected to a fixed displacement hydraulic motor 4 via a swash plate type or inclined axis type variable displacement hydraulic pump 6 driven by a traveling engine 5 of a mixer truck. 7 are connected.

The variable displacement type hydraulic pump 6 is a spring center type tilt cylinder 8 for tilting a swash plate or the like to change the pump tilt angle, that is, the pump discharge amount, and supplies the tilt cylinder 8. Pump control unit 1 comprising a spring center type electromagnetic proportional directional control valve 9 for controlling the pressure oil to be applied
When the directional control valve 9 is switched, the pilot pressure fluid is supplied from the pilot pump 11 driven by the engine 5 together with the variable displacement hydraulic pump 6 via the pilot circuit 12 to the tilt cylinder 8. Room 8a,
8b, the rod 8c moves, and the swash plate or the like is operated by the rod 8c at a tilt angle corresponding to the switching operation amount. The tilting cylinder 8 moves by moving any of the springs from the neutral position held by the springs 8d, 8d. In the neutral position, the tilting angle of the swash plate or the like is set to zero and the pump discharge amount is set to zero. However, when any of the springs is bent and moved, the swash plate or the like is tilted forward or backward at a predetermined tilt angle, and the swash plate is moved to one of the reciprocating pipelines 7 of the closed hydraulic circuit. A pump discharge amount corresponding to the tilt angle is discharged. 13 is a high-pressure relief valve provided in the closed hydraulic circuit, 14 is a low-pressure relief valve, 15 is a cut-off valve, and 17 is a flushing valve.

The solenoid proportional directional control valve 9 includes a solenoid 9
a or 9b is excited according to the current value when excited.
The spools slide from the neutral position to the switching position by flexing c and 9d, and guide the pilot pressure fluid from the pilot pump 11 to one of the chambers of the tilt cylinder 8.

The operation of the electromagnetic proportional directional control valve 9 is controlled by applying an appropriate amount of current to the solenoids 9a and 9b.
Current amplifier 18 of an electrical controller 18 having
b, 18c. The electric controller 18 supplies a signal of an engine speed detected by an engine speed detector 19 from a flywheel provided on an output shaft of the engine 5, a signal of the hydraulic motor 4 A signal of a motor rotation speed and a rotation direction detected by a rotary encoder 20 for detecting a motor rotation speed and a rotation direction provided on an output shaft, a signal of a command input device 22 operated by a manually operated lever, and the electromagnetic proportional directional control valve A signal from a changeover switch 21 for switching 9 to an automatic operation and a manual operation is input.

As shown schematically in FIG. 1, the operation section 18a receives a command input value from a command input device 22 and receives a signal from a changeover switch 21 to determine whether the operation is manual or automatic. Unit 18d, a manual control system of a manual tilt control unit 18e, a drum rotation feedback control unit 18f for performing feedback control by a signal from the rotary encoder 20, and a signal from the feedback control unit 18f by a signal from the engine speed detector 19. When the manual operation lever 26 is in the manual control area where the changeover switch 21 is turned off, the signal of the command input device 22 is used to perform manual tilt control. A current corresponding to the input value is supplied to one of the current amplifiers 18b through the system of the unit 18e, and the current corresponding to the input value is supplied to the solenoid 9b. Operation of the tilting angle of the pump lever 2
The angle is controlled in accordance with the operation amount of 6.

The operation lever 26 turns on the changeover switch.
When it is in the automatic control area and the reverse position, the command system discriminating unit 18d which receives signals from the command input unit 22 and the changeover switch 21 outputs the input value to the feedback control unit 1.
The current is input to the other current amplifier 18c through the system of 8f and the pump displacement correcting unit 18g, and a current corresponding to the input value is supplied to the solenoid 9a, and the displacement cylinder 8 controls the displacement angle of the pump. In this case, the feedback controller 18f calculates an input value and a signal value related to the number of rotations and the rotation direction from the rotary encoder 20, and sends the current value from the current amplifier 18c to the solenoid 9a so that the signal value becomes equal to the input value. By increasing or decreasing the current, the rotation speed of the mixer drum 2 is controlled to be constant. The pump tilt correction unit 1
8g performs feedforward control for correcting the value from the feedback control unit 18f based on the rotation speed detected by the rotation speed detector 19, and performs current amplifiers 18b and 18c when the detected rotation speed falls below the set rotation speed. The control to reduce the current to the solenoids 9a and 9b from, and to cut off the current when the detected rotation speed becomes zero. When the engine 5 is stopped due to overload or the like, the rotation speed detector 19 Is received by the pump displacement correcting section 18e to cut off the current to the solenoids 9a and 9b, so that the spring-centered electromagnetic proportional directional control valve 9 returns to the neutral position, whereby the chamber 8a of the displacement cylinder 8 8b is connected to the tank, and the rod 8c returns to the neutral position by the springs 8d and 8d, so that the tilt angle of the pump becomes zero, the pump discharge amount becomes zero, and the oil is discharged. Rotation of the motor 4 and the mixer drum 2 is stopped. Therefore, in the automatic operation position of the operation lever,
Even when the engine 5 is restarted, the tilt angle of the pump is zero, so that the mixer drum 2 is not driven and is safe. After the restart, if the operation lever is reset, the mixer drum 2 can be driven with a tilt angle provided to the pump. When the engine speed decreases during traveling on an uphill or the like, the solenoids 9a and 9
Since the current to b is forcibly reduced, the tilt angle of the pump is also reduced, and the driving load of the mixer drum 2 of the engine 5 is reduced, so that the engine stall during running is less likely to occur. The changeover switch simulated on the operation unit 18a is a part that can be actually switched by a program written in the operation unit.

As shown in FIG. 2, the rotary encoder 20 is preferably attached to an extension shaft 25 extending from the rotation shaft 23 of the hydraulic motor 4 to the outside of the casing 24. For example, if a device that detects a minute phase angle of about 0.7 ° is used, when the operation lever 26 is returned to the neutral position and the rotation of the mixer drum 2 is stopped, the rotation axis of the hydraulic motor 4 is set to 0.7. Even if the drum 2 is rotated by about ゜, a rotation signal from the rotary encoder 20 is output to the feedback control unit 18f, whereby current is supplied from one of the current amplifiers to the solenoid so as to return the drum 2 to the original position. Flow, the drum 2
Is transmitted through the speed reducer 3, the drum hardly rotates, and the stop position can be maintained.

The operation lever 26 is operated to one of a manual control position, a neutral position, an automatic control position, and a reverse rotation position.
When the variable displacement hydraulic pump 6 is rotated by the engine 5, the electric controller 18 supplies a current to the electromagnetic proportional directional control valve 9 in accordance with the operation position and the operating state, and the directional control valve 9 The operation of the tilt cylinder 8 is controlled, and the tilt cylinder 8 controls the tilt angle of the swash plate or the like of the pump 6 to control the discharge of the flow rate to one of the pipelines 7. This discharge rotates the hydraulic motor 4 and the mixer drum 2. That is, when the operation lever 26 is in the manual control position, a current corresponding to the operation amount is supplied to the direction control valve 9, and the tilt angle of the pump, the pump discharge amount, and the mixer drum 2 are controlled by the operation amount. It works in proportion to. When the operating lever 26 is operated to the neutral position, the electric current from the electric controller 18 to the directional control valve 9 is cut off, the directional control valve 9 returns to the neutral position, and the tilt cylinder 8 Since the chambers 8a and 8b are connected to the tank, they return to the neutral position by the force of the spring 8d, the pump discharge amount becomes zero, and the mixer drum 2 stops rotating. In this state, since the rotary encoder 20 monitors the rotation of the hydraulic motor 4 as described above, the mixer drum 2 hardly rotates from the stop position. Further, in the automatic control position of the operation lever 26, the mixer drum 2 can be controlled to a constant rotation speed even when the rotation speed of the engine 5 changes. The tilt angle is controlled to zero to reduce the load on the engine 5, or when the engine 5 is stopped, the load on the mixer drum 2 is automatically removed to ensure reliable restart and careless use of the mixer drum 2. Rotation can be prevented. When the operation lever 26 is operated to the reverse rotation position, the rotation direction signal is input from the rotary encoder 20 to the calculation unit 18a. Therefore, even when the operation lever 26 is suddenly operated to the reverse rotation position, the tilt angle of the pump is surely reversed. Can be tilted to a corner. Further, when the mixer drum 2 is rotated at a low speed by manual control, even if an uneven load is applied to the mixer drum due to an uneven load in the drum or the like, the inclination is input by inputting a small rotation phase angle from the rotary encoder 20. The drum 2 can be rotated at a very low rotation speed that matches the operation amount of the operation lever 26 without being influenced by the eccentric load by slightly adjusting the turning angle.

[0017]

As described above, according to the present invention, a fixed displacement hydraulic motor is rotated by a variable displacement hydraulic pump that is rotated by an engine and controls the pump discharge amount by an electromagnetic proportional directional control valve. In the method of rotating the mixer drum connected to the motor, the electromagnetic proportional directional control valve is electrically controlled by the electric controller so that the discharge amount of the pump becomes zero when the rotation speed of the engine becomes equal to or less than the set value. When the engine is stopped due to overload, the load on the mixer drum can be automatically removed and restarted, so that there is no danger of the mixer drum rotating upon restarting.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of a specific configuration of a main part of FIG. 1;

[Description of Signs] 2 mixer drum, 4 fixed displacement hydraulic motor, 5
Running engine, 6 variable displacement hydraulic pump, 8 tilt cylinder, 9 electromagnetic proportional directional control valve, 10 pump control section, 18 electric controller, 19 engine speed detector, 20 rotary encoder,

Claims (3)

[Claims] A variable displacement hydraulic pump that is rotated by an engine and controls a pump discharge amount by an electromagnetic proportional directional control valve; and a fixed displacement hydraulic motor that is rotated by discharge of the hydraulic pump. A method of controlling the operation of the mixer drum by connecting a mixer drum to a hydraulic motor via a speed reducer and controlling the operation of the electromagnetic proportional directional control valve by an electric controller to control the pump discharge amount. An engine-driven mixer, wherein the electromagnetic proportional directional control valve is controlled by an electric controller so that the discharge amount of the variable displacement hydraulic pump becomes zero when the engine speed falls below a set value. Drum drive control method. 2. The method according to claim 1, wherein the number of rotations and the direction of rotation of the fixed displacement hydraulic motor are detected by a rotary encoder, and the detected values are corrected so that the control value from the electric controller to the electromagnetic proportional directional control valve becomes constant. A drive control method for a mixer drum driven by an engine, comprising: 3. The drive control method for an engine-driven mixer drum according to claim 2, wherein the number of rotations of the fixed displacement hydraulic motor is detected at a small rotation phase angle.