JPS6030028Y2 - Mixer drum drive device in concrete mixer vehicle - Google Patents

Description

[Detailed description of the invention] This invention relates to a mixer drum drive device in a concrete mixer truck, and more specifically, the mixer drum rotation speed is set at a medium speed, and when it is lower than this, a manual servo mechanism is used, and when it is higher than this, a manual servo mechanism is used. The present invention relates to a drive device for mixer drums in a concrete mixer vehicle, each of which is controlled using an automatic control mechanism.

In general, a concrete mixer vehicle extracts power from a vehicle engine and transmits the power using a hydraulic pump and a motor to drive a mixer drum.

Further, by controlling the hydraulic pump, forward/reverse rotation and rotational speed of the mixer drum are controlled, and a servo mechanism is usually used to control the hydraulic pump.

Furthermore, concrete mixer trucks must transport the ready-mixed concrete input at the plant to the factory and site without degrading its quality. For this reason, the drum is constantly rotating during transport of the ready-mixed concrete. Must be kept agitated.

Currently, mixer drum drive devices that use servo mechanisms are
There are those using a manual servo mechanism and those using a servo mechanism with automatic control, and each has advantages and disadvantages in traveling stirring.

A control device using a manual servo mechanism has a circuit configuration as shown in FIG.

This means that the hydraulic pump 1 and the hydraulic motor 2 are connected to the main circuit 3,
4, the hydraulic motor 2 drives a mixer drum 6 via a reducer 5, and a boost pump 7.
is connected to a servo cylinder 11 via a servo mechanism 10 consisting of a piston 8 and a spool 9, the hydraulic pump 1 and the boost pump 7 are driven by the vehicle engine 12, and when the lever 13 is fixed at a certain position by manual operation, The spool 9 and the piston 8 move a certain amount, and the tilting angle of the hydraulic pump 1 is set to a certain angle depending on the positional relationship between the two, and the discharge amount per revolution of the hydraulic pump 1 whose discharge amount is variable is determined.

However, with this lever drive device, as shown in characteristic C in Figure 2, when the engine speed is on the X axis and the mixer drum speed is on the Y axis, the mixer drum rotates in proportion to the engine speed during traveling and stirring. numbers rise.

Therefore, when the engine speed is below medium speed, there is no waste in the horsepower consumption, but when the engine speed is above medium speed, the horsepower consumption becomes larger than necessary, which is uneconomical, and the vehicle tends to roll. There are drawbacks.

On the other hand, a mixer drum drive device using a servo mechanism with automatic control has a circuit configuration as shown in FIG. 3. In addition to the circuit shown in FIG. The differential pressure before and after the orifice 14 is guided to both sides of the piston 8 as pilot pressure, and the orifice 1
When a pressure difference occurs before and after 4, the piston 8 is switched to increase or decrease the tilting angle of the hydraulic pump 1 each time.

That is, when the contact lever 13 is fixed at a certain position, the discharge amount of the variable discharge amount pump 1 per hour is set, and the automatically variable orifice 14 is set in proportion to the engine rotation speed during running stirring.
The differential pressure before and after increases, and this differential pressure is used as pilot pressure to guide one side of the piston 8, so the positional relationship between the spool 9 and the piston 8 changes, and the pump discharge amount changes in inverse proportion to the engine speed.

In other words, as the engine speed increases, the amount of discharge is attempted to be reduced, and as the engine speed decreases, the amount of discharge is increased, so the drum speed is related to the engine speed as shown in characteristic d in Figure 4. It is always constant.

However, in the drive device of the above-mentioned automatically controllable Sanibo mechanism,
Since the drum rotation does not fluctuate, the quality of the ready-mixed concrete is good, there is no rolling of the vehicle while driving, and even when the engine speed is medium or higher, the drum rotation speed is constant and does not rotate more than necessary, so horsepower consumption is low. On the other hand, since the drum rotates at a constant speed even when the engine speed is below medium speed, a large amount of horsepower is wasted.

Further, since the orifice 14 is provided in the main circuit 3, there is a large horsepower loss in the hydraulic circuit, which not only causes an increase in oil temperature and deterioration of oil quality, but also has the disadvantage that the servo mechanism will stop due to a partial failure.

Therefore, the purpose of this invention is to incorporate the advantages of a manual servo mechanism and a servo mechanism with automatic control, and to control the drum rotation speed during transport of fresh concrete by using the manual servo mechanism when it is low, and automatically controlling it when it is high. An object of the present invention is to provide a drive device for a mixer drum in a concrete mixer truck, which is controlled by operating an attached servo mechanism.

That is, according to the present invention, when the engine speed is low, the engine speed and the mixer drum rotation speed are made proportional to the middle speed,
An energy-saving mixer drum drive device that rotates the mixer drum at a constant speed regardless of changes in engine speed when the engine is at high speed, and further controls the pump discharge amount using only the boost pressure of the boost pump, reducing horsepower loss in the hydraulic circuit. That's what you get.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6.

A variable displacement hydraulic pump 15 and a constant displacement hydraulic motor 16 are connected via a main circuit 17.18, and the hydraulic motor 16
is connected to the mixer drum 20 via a speed reducer 19.

The main circuit 17 is connected to a boost pump 23 via a check valve 21 and a circuit 22, so that the leakage bone is supplied from the boost pump 23.

The hydraulic pump 15 and the boost pump 23 are connected to the engine 24 of the concrete mixer truck, and increase the discharge pressure in proportion to the rotation speed of the engine 24. The hydraulic pump 15 is connected to the constant displacement motor 16 via the main circuit 17 or 18. It is designed to supply pressure oil to the

The swash plate of the variable discharge hydraulic pump 15 is a servo cylinder 25
The swash plate angle is displaced in accordance with the movement of the piston 26, and the discharge amount per rotation is set in accordance with the swash plate angle.

The oil chambers 27 and 28 of the servo cylinder 25 are connected to circuits 29 and 30.
These circuits 29 and 30 are selectively connected to a boost pump side circuit 32 and 34 or a tank side circuit 33 via a servo valve 31.

The servo valve 31 consists of a piston 35 and a spool 36 slidably inserted into the piston 35. The spool 36 has a normal rotation position 37 on the left, a reverse rotation position 38 on the right, and a neutral position 39. 36
When the servo cylinder 25 switches to the forward rotation position 37,
Boost pressure oil is supplied to the oil chamber 27 of the spring 40.
The piston 26 is displaced against this, and the swash plate of the hydraulic pump 15 is displaced by an arbitrary angle toward the normal rotation side.

At this time, the other oil chamber 28 of the servo cylinder 25 is connected to the tank 4.
2, and the movement of the piston 26 is fed back to the piston 35 of the servo valve 31 via the feedback mechanism 43, and the servo valve 31 is returned to neutral.
As a result, the hydraulic pump 15 discharges the amount of oil set by the swash plate angle to the main circuit 17.

Conversely, when the spool 36 is switched to the right reverse position 38, boost pressure is supplied to the oil chamber 28, and the spring 41
The piston 26 moves against this, the swash plate of the hydraulic pump is displaced to the reverse side, and the oil amount set at the swash plate angle is transferred to the main circuit 1.
Discharge at 8.

The boost pump side circuit 32 is connected to the main circuit 18 via a branch circuit 44 and a check valve 45, and the main circuit 1
8 can be refilled with oil.

The spool 36 is connected to the piston rod 4 via a connecting member 46.
7, and the piston rod 47 is connected to the automatic control cylinder 4
8 via a piston, the control cylinder 48 is integrally coupled with an operating lever 49, and when the angle of the operating lever 49 is displaced, the movement is integrally transmitted to the control cylinder 48 and piston rod 47. It is now possible to do so.

The connecting member 46 and the piston rod 47 are axially connected via an elongated hole 50, the right oil chamber 51 of the control cylinder 48 is connected to the boost pump side circuit 32, and the other oil chamber 52 is connected to the circuit 54, and this circuit 54 branches from the circuit 30 and communicates selectively with the high pressure side or the low pressure side via the servo valve 31.

A spring 53 is interposed within the oil chamber 52, and constantly biases the piston rod 47 in the right direction.

A direct dynamic relief valve 5 is provided in the boost pump side circuit 32.
5 is connected, and an orifice 56 is interposed in the middle as necessary.

The set load of the spring 53 in the automatic control cylinder 48 is made to match the set pressure of the relief valve 55, and when the boost pressure in the oil chamber 51 overcomes the set load of the spring 53, the piston rod 47 resists the spring 53. It moves to the left and switches the spool 36 to the right position 38.

That is, in this case, the relief valve 55 is a direct acting relief valve, and the piston rod 47 of the control cylinder 48
The discharge amount of the variable discharge amount pump 15 is controlled by operating in the override characteristic region, and the output amount of the mixer drum 20 is controlled.
This is to control the rotational speed of the motor to a constant value.

Next, we will discuss the operation.

The control device of this invention is a type of control device that takes advantage of the respective advantages of conventional manual servo and automatic control servo, maintains stable fresh concrete quality and stable driving performance, and saves engine horsepower consumption. The drum rotation speed characteristics are shown in the characteristic diagram of FIG.

In other words, when the engine speed is plotted on the X-axis and the mixer drum rotation speed is plotted on the Y-axis, when the engine speed is below medium speed, the mixer drum speed is proportional as shown in characteristic a, and when the engine speed is medium speed. In the above case, the mixer drum rotational speed is constant regardless of the engine rotational speed as shown in the characteristic.

First, when the mixer truck is running and stirring, the engine rotation should be idling (approximately 450 to 550 r, P
.

m) When the operating lever 49 is set to the stirring position shifted to the right in FIG. 5, the control cylinder 48,
The spool 3 is connected via the piston rod 47 and the connecting member 46.
6 is pulled to the right, thereby switching the position of the spool 36 to the normal rotation position 37.

For this reason, the boost pressure from the boost pump 23 is applied to the circuit 32.
The oil is supplied to one oil chamber 27 of the servo cylinder 25 via the circuit 29, and moves the piston 26 in the positive direction against the spring 40, thereby causing the swash plate of the variable displacement pump 15 to move in response to the movement of the piston 26. A tilting angle is set, and pressure oil corresponding to the tilting angle is discharged to the main circuit 17.

Further, the movement of the piston 26 is fed back to the piston 35 of the servo valve 31 via the feedback mechanism 43, and by moving the piston 35, the servo valve 31 is returned to the neutral state.

When pressure oil is discharged from the hydraulic pump 15 to the main circuit 17, the constant displacement motor 16 begins to rotate, and the mixer drum 20 begins to rotate via the reducer 19.

Next, when the engine rotation is gradually increased from idling to high speed, the mixer drum rotation increases in proportion to the engine rotation as shown in characteristic a.

That is, up to a medium engine speed, the mixer drum rotation speed is proportional to the engine rotation speed using the same mechanism as the conventional manual servo.

Further increase the engine speed until medium speed rotation (approximately 150O
r, p, m), the following operation occurs.

When the engine speed increases, the discharge amount from the hydraulic pump 15 and the boost pump 23 increases, and the pressure oil from the boost pump 23 is supplied from the boost circuit 32 to the oil chamber 51 of the control cylinder 48.

Pressure oil from the boost pump 23 is introduced into the oil chamber 51 even when the speed is medium or lower, but this boost pressure is balanced with the reaction force of the spring 53, and the piston rod 47 does not fluctuate.

However, when the speed becomes medium or higher and the pressure oil of the boost pump 23 rises, this boost pressure overcomes the set load of the spring 53 and pushes the piston 47 to the left in FIG. 5.

When the engine speed becomes medium speed or higher, the boost pressure increases, and when this boost pressure reaches the relief set pressure of the relief valve 55, the relief valve 55 is opened and the tank 4
However, the relief valve 55 has an override characteristic, and the piston 47 is actuated by utilizing this override.

When the piston 47 moves to the left, the spool 36 switches to the right reverse position, and boost pressure is applied from the boost circuits 32 and 34 to the oil chamber 2 of the servo cylinder 25 via the circuit 30.
8 and moves the piston 26 to the hydraulic pump 15.
The swash plate tilt angle of the hydraulic pump 1 is displaced in the negative direction.
Reduce the discharge amount per rotation from 5.

In other words, the discharge amount per rotation of the variable discharge hydraulic pump 15 decreases in inverse proportion to the engine speed, and as a result, the mixer drum rotation speed remains constant regardless of the increase in engine speed, as shown in the characteristic chart in FIG. It will be controlled by

As described above, during running and stirring, the rotational speed of the drum 20 increases in proportion to the engine rotational speed up to medium speed rotation, and at medium speed rotation, the drum rotational speed remains constant regardless of the engine rotational speed.

Next, when pouring fresh concrete, the spool 36 is moved to the right via the operating lever 49, the servo valve 31 is switched to the normal rotation position 37, and the hydraulic pump 15 is driven to rotate in the normal rotation.

As in the case of agitation while running, when the engine speed is below medium speed, the speed of mixer drum 20 increases proportionally, and when the engine speed is above medium speed, boost pressure acts on piston 47 of control cylinder 48. However, since the amount of rightward movement of the spool 36 at the time of injection is large, moving the spool 36 to the left does not affect the control force much, and therefore the engine rotational speed and the drum rotational speed are approximately proportional.

When discharging fresh concrete, the spool 36 is switched to the right reverse position 38 via the operating lever 49, the variable hydraulic pump 15 is reversed, pressure oil is discharged to the main circuit 18 side, and the mixer drum 20 is reversed.

However, at the time of exhaustion, the boost pressure is balanced on both sides of the control cylinder 48, regardless of the engine speed, so the control mechanism does not work as it does during stirring.
Engine rotation and drum rotation speed are proportional.

Furthermore, when in neutral, even if the engine speed reaches medium speed or higher, the piston 4
7 moves to the left, this movement causes the elongated hole 5 of the connecting member 46 to
0, and the movement of the piston 47 is not transmitted to the spool 36, so it does not operate.

As described above, the present invention makes it possible to utilize the advantages of manual servo by making the engine rotation speed proportional to the drum rotation speed when the engine is running at low speed, during the transportation of fresh concrete, and when the engine is running at high speed (medium speed). speed or higher)
Since the system takes advantage of automatic control in which the drum rotation speed is kept constant regardless of the engine rotation speed, the engine rotation is efficiently transmitted to the drum rotation, resulting in an energy-saving control device.

Furthermore, even if the automatic control section breaks down, the rotation can still be controlled mechanically.

Since there is no orifice in the main circuit, there is no horsepower loss in the hydraulic circuit, and oil temperature increases and oil quality deterioration can be prevented.

[Brief explanation of drawings]

Figure 1 is a hydraulic control circuit diagram using a conventional manual servo.
Figure 2 is the drum rotation speed characteristic diagram of Figure 1, Figure 3 is a hydraulic control circuit diagram using a servo with automatic control, Figure 4 is the drum rotation speed characteristic diagram of Figure 3, and Figure 5 is the control of the present invention. The hydraulic circuit diagram of the device, FIG. 6, is a drum rotation speed characteristic diagram of FIG. 5. 15...Variable discharge amount pump, 16...
Constant capacity motor, 20...Mixer drum, 23.
...Boost pump, 24...Engine, 25...Servo cylinder, 31...
Servo valve, 32...Boost pump side circuit, 36...Spool, 47...Zeston rod, 48...Control cylinder, 51...
... Oil chamber, 53 ... Spring, 55 ...
··Relief valve.

Claims (3)

[Scope of utility model registration request] (1) A variable discharge pump and a constant displacement motor connected to a mixer drum are connected in a closed circuit U, and a boost pump driven by the same engine as the variable discharge pump is selectively connected to a servo cylinder via a servo valve. In a hydraulic power transmission device, a servo valve is connected to a piston rod in a control cylinder, a boost pump side circuit is connected to one oil chamber of this control cylinder, and a relief valve is connected to this boost pump side circuit. At the same time, a spring is installed in the opposite position to the oil chamber, so that when the engine speed is below medium speed during running or stirring, the boost pressure supplied to the oil chamber is balanced with the spring and the speed is above medium speed. A drive device for a mixer drum in a concrete mixer vehicle in which the boost pressure overcomes the spring and switches the spool to change the tilt angle of the swash plate of the variable discharge pump. (2) The mixer drum in the concrete mixer vehicle according to claim 1, wherein the spool is connected to the piston rod of the control cylinder through a connecting member, and the connecting member and the piston rod are axially connected through an elongated hole. drive unit. (3) A drive device for a mixer drum in a concrete mixer vehicle as set forth in claim 1 of the registered utility model claim, wherein an orifice is provided in the boost circuit.