JPH0372441B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method and apparatus for producing ready-mixed concrete in a ready-mixed concrete production plant.

(b) Prior art The applicant has developed a ready-mixed concrete manufacturing plant that takes into consideration the mixing load state of the mixer during the production of ready-mixed concrete, and uses high-speed rotation at the beginning of material introduction, low-speed rotation after gravel is added, and mixing during the middle of mixing. An application has been filed (Japanese Unexamined Patent Publication No. 62-25014) that kneading is performed again at high speed rotation when the load is reduced to shorten the kneading time as much as possible and enable efficient kneading.
It is.

(c) Problems to be Solved by the Invention The kneading load state of the mixer is correlated with the load current value of the motor that drives the mixer. Therefore, the present invention is based on the Japanese Patent Application Laid-Open No.
62-25014, the switching between high-speed rotation and low-feed rotation is performed in relation to the load current value of the drive motor of the mixer, thereby making it possible to perform more efficient kneading.

(d) Means for Solving the Problems The present invention provides a drive motor 2 of a mixer 1 for mixing fresh concrete with a two-stage variable speed, and a current detection circuit 3 for detecting a load current value of the drive motor 2 and a current value. an upper limit current setter 5, a lower limit current setter 6, and a comparison circuit that detects with the current detection circuit 3 and compares the load current value with the set current value of the upper limit current setter 5 and the lower limit current setter 6. 4, and a means for switching the rotation speed of the drive motor 2 based on the output signal of the comparison circuit 4.

(e) Function The present invention measures the load current value of the drive motor 2 of the mixer 1 during kneading with the current detection circuit 3, and sets the load current value and the upper limit current setting device 5 and the lower limit current setting device 6 in advance. The comparator circuit 4 compares the rotation speed of the drive motor 2, which was started at high speed at the start of kneading, with the rotation speed of the drive motor 2, which is changed to a low speed when the load current value exceeds the upper limit current setting and the kneading load becomes large. When the load current value becomes lower than the lower limit current setting value and the kneading load becomes small, the drive motor 2 is switched to high speed rotation again to mix the fresh concrete efficiently.

(E) Embodiment FIG. 1 shows an embodiment of the present invention. Reference numeral 1 denotes a mixer installed in a ready-mixed concrete manufacturing apparatus, and a kneading shaft is rotated by a drive motor 2. The drive motor 2 adopts a variable speed motor; for example, if it is a two-speed variable speed motor, the number of poles should be 4 or 6.
It uses a pole change motor that can change speed by changing the poles. 3 is drive motor 2
The current detection circuit detects the load current value of the current detection circuit 3, and the load current value detected by the current detection circuit 3 is connected to the upper limit current setter 5 and the lower limit current setter 6 in the comparator circuit 4.
When the load current value is less than the lower limit current setting value and the kneading load becomes smaller, a conversion signal is sent to the pole number conversion circuit 7 to change the pole number conversion motor, which is the drive motor 2, to 4 poles. is output for high-speed rotation, and if the load current value exceeds the upper limit current setting and the kneading load becomes large, the drive motor 2
A conversion signal is output to the pole number conversion circuit 7 so as to change the pole number conversion motor to six poles, and the motor rotates at a low speed.

Next, the setting of the upper limit current set value and the lower limit current set value will be described. FIG. 3 is a diagram showing the load current value of the constant speed drive motor 2 during material kneading in a two-shaft mixer. Input the materials first, sand,
Cement and water are added, and after 10 seconds, gravel is added. As soon as gravel starts to be added, the kneading load increases and the load current value increases rapidly. For this reason, if the drive motor is rotated at high speed, the load torque of the drive motor will be large, and if sufficient margin is not provided when selecting the motor, the operation will become unstable, so it is necessary to rotate at low speed to ensure stable speed. be. In this way, the current value at which stable operation cannot be maintained at high speed rotation is set as the upper limit current setting value.

Further, as the mixing progresses, the kneading resistance gradually decreases, so the lower limit current setting value is the load current value that allows stable operation to be maintained even when switching from low speed rotation to high speed rotation.

There is a certain range between the upper limit current setting value and the lower limit current setting value, and as can be seen from Figure 3, the load current value during kneading changes in a mountain shape from a macro perspective. This is because, microscopically, the current is changing while changing up and down, so if the upper limit current setting value and the lower limit current setting value are set within the fluctuation range, there is a risk of causing chattering. Therefore, the interval between the upper limit current setting value and the lower limit current setting value is preferably determined in consideration of the range of fluctuation that varies depending on the mixer capacity and the kneaded materials.

When producing ready-mixed concrete according to the present invention, as shown in the cycle time chart in Figure 2, when sand, cement, and water are started being introduced into the mixer 1, the load current value of the drive motor 2 is low, so the high speed rotation is possible. The load current value of the drive motor 2 increases with the start of gravel feeding, and when it exceeds the upper limit current setting value, the rotation speed is switched to low speed. As the kneading progresses, the load current value of the drive motor 2 becomes less than the lower limit current setting value, and the high speed rotation is again switched to uniformly knead the materials.

When discharging the fresh concrete from the mixer 1 after the completion of mixing the materials, if the mixer 1 is operated at high speed, the fresh concrete may be scattered, so it is preferable to output a mixer gate open signal from the operation panel 8 to the comparison circuit 4. Then, a conversion signal is output from the comparator circuit 4 to the pole number changing circuit 7, and the pole number changing motor, which is the drive motor 2, is changed to six poles and switched to low speed rotation. In addition, the mixer gate opening/closing detector 9 detects that fresh concrete is discharged from the mixer 1 and the mixer gate is closed, and the detection signal is output to the operation panel 8. A conversion signal is output to the number conversion circuit 7, and the pole number conversion motor, which is the drive motor 2, is changed to four poles and switched to high speed rotation in preparation for the next kneading.

(F) Effects of the Invention The present invention detects the kneading load state of the mixer 1 by the load current value of the drive motor 2 that drives the mixer 1, and when the load current value becomes equal to or higher than the upper limit current setting value,
If the kneading resistance increases, the machine will rotate at a low speed, and if the load current value is below the lower limit current setting and the kneading resistance becomes small, the machine will run at a high speed, so the kneading load state will change due to changes in the material feeding order and mixture. This has the practical benefit of ensuring that efficient kneading is always carried out commensurate with the kneading load state, and that the kneading time can be shortened as much as possible.

[Brief explanation of drawings]

FIG. 1 is a diagram clearly showing the implementation sequence of the apparatus of the present invention, FIG. 2 is a chart of cycle time, and FIG. 3 is a diagram showing the load current value of the constant speed drive motor of the mixer during mixing of materials. 1... mixer, 2... drive motor, 3...
Current detection circuit, 4...Comparison circuit, 5...Upper limit current setter, 6...Lower limit current setter, 7...Pole number conversion circuit, 8...Operation panel, 9...Gate opening/closing detector.

Claims (1)

[Claims] 1. The drive motor of the mixer for mixing fresh concrete has a two-stage variable speed, and first the drive motor is rotated at high speed to start kneading, and the load current value of the drive motor during kneading is detected, and the load Ready-mixed concrete characterized in that when the current value becomes equal to or higher than the upper limit current setting value, the rotation speed is switched to low speed for mixing, and when the load current value becomes below the lower limit current setting value, the rotation is switched to high speed again for kneading. manufacturing method. 2 The drive motor of the mixer for mixing fresh concrete has a two-stage variable speed, and first the drive motor is rotated at high speed to start kneading, and the load current value of the drive motor during kneading is detected, and the load current value is set as the upper limit current. If the load current value exceeds the lower limit current setting value, the mixer switches to low speed rotation for kneading, and then when the load current value falls below the lower limit current setting value, it switches to high speed rotation again for kneading, and the mixer changes to low speed rotation by the mixer gate open signal from the operation panel. A method for producing ready-mixed concrete, characterized in that the rotation is switched to high speed in response to a gate closing signal. 3. The drive motor of the mixer for mixing fresh concrete has a two-stage variable speed, and includes a current detection circuit for detecting the load current value of the drive motor, an upper limit current setting device and a lower limit current setting device for setting the current value, and the current detection circuit. A comparison circuit that compares the load current value detected by the circuit with the set current values of the upper limit current setting device and the lower limit current setting device, and the load current value is used to set the upper limit current. Production of ready-mixed concrete characterized by comprising means for switching to low-speed rotation when the load current value exceeds the lower limit current value, and then to high-speed rotation again when the load current value becomes less than or equal to the lower limit current setting value, according to the output signal of the comparison circuit. Device.