JPS6261404B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the amount of additives introduced into a mixer drum in order to maintain the quality of fresh concrete in a truck mixer.

Fresh concrete placed in a mixer drum driven by a hydraulic motor undergoes a hydration reaction over time during transportation, gradually losing its fluidity, resulting in a decrease in workability during concrete pouring. (The fluidity of fresh concrete is generally measured as the slump value as specified in "JISA1101".)

In recent years, in order to prevent a decrease in the slump value of fresh concrete being transported by a truck mixer, additives have been developed that can be added to and mixed with fresh concrete to freely adjust the slump value.

By adding this additive in small amounts to fresh concrete being stirred by a mixer drum, it is possible to prevent a decrease in slump value by using a small amount of water that does not adversely affect strength. In addition to being able to obtain ready-mixed concrete with high quality and good workability, it has also become possible to transport high-strength ready-mixed concrete over long distances, which was previously considered impossible.

However, in order to obtain fresh concrete with a predetermined slump value, the amount and interval of addition of additives must be well adjusted.

It is difficult to determine in advance the amount of additive to be added at one time and the interval between additions because the reaction time varies depending on conditions such as the quality of fresh concrete, temperature, and formulation.

Focusing on this problem, we developed a system that automatically injects a predetermined amount of additives when the ready-mixed concrete in the mixer drum drops below the set slump value to keep the slump value of the ready-mixed concrete constant over a long period of time. A device for controlling the addition of additives that can be transported has already been proposed (Japanese Patent Application No. 77938/1983, Japanese Patent Publication No. 12045/1983).

This is used for hydraulically driven track mixers,
The inlet pressure in the hydraulic motor of the mixer drum, which is proportional to the slump value of fresh concrete, is detected and converted to a current value, and this current value (that is, the slump value) is
It controls the addition of additives based on the

By the way, in this type of truck mixer, the hydraulic circuit that connects the hydraulic pump and the hydraulic motor is generally a closed circuit, and in order to compensate for hydraulic oil leakage and temperature rise in this closed circuit, a small boost pump is installed. is provided, and by operating this in parallel with the hydraulic pump, new hydraulic oil is pre-loaded into the closed circuit.

The amount of oil discharged from the boost pump increases or decreases in proportion to the engine speed, so even if a boost pressure relief valve is provided, this variation cannot be completely eliminated.

The above-mentioned additive dosing control device detects the inlet pressure of the mixer drum's hydraulic motor as the slump value of the fresh concrete, so even if the effective pressure for generating torque remains the same, if the boost pressure in the return circuit increases, The inlet pressure of the hydraulic motor increases by the amount of boost pressure, and the detected slump value of the actual ready-mixed concrete is lower by the increase in boost pressure.As a result, the additive cannot be added properly, and the desired slump is not achieved. There is a problem that it is not possible to obtain ready-mixed concrete of value.

Therefore, the present invention is directed to a system in which the differential pressure between the inlet pressure and the outlet pressure of the hydraulic motor in the hydraulic circuit indicates an accurate amount of work of the hydraulic motor that is not affected by boost pressure, and that amount of work is This method was developed by focusing on the fact that it is proportional to the slump value of concrete, and detects the inlet pressure and outlet pressure of the hydraulic motor, and calculates the differential pressure (slump value).
By automatically controlling the amount of additive added based on the The purpose of this invention is to provide a charging control device.

Embodiments of the present invention will be described below based on the drawings.

Figure 1 is a schematic side view of the track mixer.
1 is a mixer drum, 2 is a hydraulic motor, and 3 is a hydraulic pump, and a closed circuit 4 is formed between the hydraulic motor 2 and the hydraulic pump 3.

Reference numerals 5 and 6 denote oil pressure detectors respectively attached to the inlet and outlet of the hydraulic oil in the hydraulic motor 2. These detectors 5 and 6 are a combination of a Breton tube and a potentiometer, and are detected by the Breton tube. The hydraulic oil pressure is detected as a change in electrical resistance using a potentiometer.

The outputs of the detectors 5 and 6 are input to a controller 7 provided in the driver's cab. The controller 7 controls the hydraulic motor 2 based on the electrical signals from the detectors 5 and 6.
The differential pressure between the inlet pressure and the outlet pressure of the mixer drum is calculated, and a drive signal is output to the device 30 that introduces the additive into the mixer drum so that the differential pressure, that is, the slump value of the fresh concrete, remains at the set value. It's summery.

The circuit configuration of this controller 7 will be explained with reference to the block diagram of FIG.

20 is a differential amplifier, which amplifies the difference between the output voltages of the detectors 5 and 6 and outputs the amplified voltage difference. The output signal of the differential amplifier 20 is further amplified by the amplifier 21 and then enters the low-pass filter 22, where high frequency components due to load fluctuations caused by the rotation of the mixer drum and pressure fluctuations in the hydraulic circuit are removed, and the waveform is adjusted.

The output voltage of the low-pass filter 22 is input to the monitor meter 16 to display the slump value of the fresh concrete as the deflection angle of the pointer 15, and is input to each of the comparators 23, 24, and 25 provided in parallel.

A comparison setting voltage from a variable resistor 33 that sets a slump value is input to the comparators 23, 24, and 25. However, the comparison voltage values are different depending on the internal resistance values of the comparators 23 to 25, and in this embodiment, the comparison voltage value of the comparator 23 is set to be the maximum, and the comparison voltage value is set to gradually decrease thereafter. and comparators 23, 24,
25 compares the output voltage of the low-pass filter 22 with a set voltage, and when the output voltage is higher, outputs a high level signal to AND circuits 26, 27, and 28, which will be described later.

AND circuits 26, 27, 28 are comparator 2
When the outputs of 3, 24, and 25 switch to high level, the gate is opened and the output signals from the oscillation circuit 29 and the frequency dividing circuit 32 are sent to the drive circuit 3 of the additive injection device 30.
Send to 1.

The frequency of the output signal of the oscillation circuit 29 determines the additive injection interval, and at the same time, the frequency of this output signal is changed to 1/2, 1/4 by the frequency dividing circuit 32, and the frequency is changed to 1/2, 1/4 by the AND circuit 25, 26, 27 respectively.

Next, the effect will be explained.

An output signal corresponding to the slump value of fresh concrete in the mixer drum is input from the differential amplifier 20 to comparators 23, 24, and 25.

If this slump value applies to all comparators 2
When it is larger than the comparison voltage value of 3 to 25, the AND circuit 26
28 gates are all opened, and pulse signals from the oscillation circuit 29 and the frequency dividing circuit 32 are input to the drive circuit 31. In this case, since the pulse signals are all synchronized with each other, the drive circuit 31 eventually operates the additive injection device 30 with an output pulse corresponding to the pulse signal of the oscillation circuit 29. When the slump value is large, the intervals between adding the additives become closer in this way, thereby quickly reducing the slump value of the ready-mixed concrete. When the slump value decreases, the output of the differential amplifier 20 also decreases. For example, if the output of the comparator 25 is switched to a low level while the comparators 24 and 23 remain unchanged, the AND circuit 28 closes the gate. Therefore, a pulse signal obtained by dividing the output of the oscillation circuit 29 by two is supplied to the drive circuit 31, and if the slump value further decreases in the same manner, the AND circuit 29
7 also closes the gate, and a pulse signal whose frequency is divided by four is supplied, and the amount of additive added decreases in accordance with the decrease in the slump value. Therefore, it is possible to always supply an appropriate amount of additive in a responsive manner in response to changes in the slump value of fresh concrete.

In the above embodiment, by changing the resistance value of the variable resistor 34 provided in the oscillator 29 using a time dial, the pulse width of the output signal of the oscillator 29 is expanded or contracted to adjust the amount of additive added at one time. be able to.

As explained above, this invention detects the differential pressure between the hydraulic fluid inlet pressure and outlet pressure of the hydraulic motor, so there is no error in the slump value due to boost pressure in the hydraulic circuit, and accurate Since the slump value can be detected, and the additive dosing device is driven based on the detected slump value to control the amount and interval of addition of the additive, the slump value of the fresh concrete being transported can be adjusted to the desired value in a responsive manner. It has the effect of being able to maintain the set value of , and improving concrete placement workability.

[Brief explanation of the drawing]

The drawings show one embodiment of the invention.
The figure is a schematic side view of the track mixer, and FIG. 2 is a block diagram showing the circuit configuration of the controller. 2...Hydraulic motor, 4, 5...Detector, 7...
Controller, 30... Additive injection device.

Claims (1)

[Scope of Claims] 1. In a hydraulically driven truck mixer, means for detecting a slump value based on the differential pressure between the hydraulic fluid inlet pressure and outlet pressure of a hydraulic motor, and a means for detecting a slump value based on a differential pressure between a hydraulic fluid inlet pressure and an outlet pressure of a hydraulic motor, and a means for detecting a slump value by comparing the slump value with a set value. A device for controlling the addition of a ready-mixed concrete additive, comprising means for increasing or decreasing the amount of the additive added in accordance with the result. 2. The means for increasing or decreasing the amount of additive input consists of comparators each having a different set value, AND circuits that open and close based on the output of these comparators, and pulse signals of different frequencies supplied to the drive circuit through each AND circuit. 2. A ready-mixed concrete additive dosing control device according to claim 1, characterized in that the device is comprised of an oscillation circuit that performs the following steps.