JP2003294007A - Hydraulic control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control system, inexpensive and capable increasing an operation speed of an actuator without increasing a revolution speed of an engine. <P>SOLUTION: The system is characterized in that it includes circular circuits 22, 23 for connecting an actuator A and a main pump P1, a fixed delivery sub-pump P3 whose driving source is an engine E, interfluent passages 26, 27 for flowing discharge oil of the sub-pump P3 into the circular circuits, a directional control valve B that is provided in the interfluent passages and links the sub-pump P3 to a tank T or the circular circuits 22, 23 according to a direction selected position, an exhaust valve 41 connected to the circular circuits 22, 23 and a pressure control valve 46 provided between the exhaust valve 41 and the tank T. The exhaust valve 41 keeps its closing position when the sub-pump P3 is linked to the tank via the directional control valve B, while it keeps its opening position when the sub-pump P3 is linked to the circular circuits 22, 23 via the directional control valve B. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device used for a specially equipped vehicle such as a concrete mixer truck or a garbage truck.

[0002]

2. Description of the Related Art As a hydraulic control device used in, for example, a concrete mixer truck, the one shown in FIG. 4 has been conventionally known. In this conventional device, the output shaft d of the engine E is
The variable displacement main pump p1 and the constant displacement charge pump p2 are linked, and the main pump p1 and the charge pump p2 are driven according to the operation of the engine E. Main pump p
1 connects the discharge port 10 to the first port 12 of the switching valve b via the passage 1. A second port 13 of the switching valve b is connected to the suction port 11 of the main pump p1 via the passage 2.

The third and fourth ports 14, 1 of the switching valve b
5 to the actuator a via pipes 5 and 6, respectively.
Connected to. A drum D containing cement is linked to the actuator a, and the drum D is rotated according to the operation of the actuator a.

A controller c for controlling the discharge amount is connected to the main pump p1. When the switching valve b is in the neutral position, the controller c reduces the tilt angle of the swash plate of the main pump p1 to minimize the discharge amount. Further, when the switching valve b is switched to either direction by the operation lever 7, the tilt angle of the swash plate of the main pump p1 is increased and the discharge amount thereof is increased. The discharge amount of the main pump p1 is also proportional to the rotation speed of the engine E. That is, the higher the rotation speed of the engine E, the higher the discharge amount of the main pump p1, and the lower the rotation speed of the engine E, the lower the discharge amount of the main pump p1.

On the other hand, the charge pump p2 has its discharge port 8 side connected to the passage 1 via a check valve 3 and to the passage 2 via a check valve 4. The charge pump p2 thus configured compensates for the shortage of the flow rate in the circuit. That is, this device is a so-called closed circuit, and a certain amount of hydraulic oil is circulated in the circuit. However, the flow rate in the circuit may become insufficient due to oil leakage, and in such a case, the charge pump p2 supplements the insufficient flow rate.

Next, the operation of this conventional device will be described.
When the switching valve b is in the neutral position shown in the figure, the controller c keeps the discharge amount per one rotation of the main pump p1 to a minimum. Therefore, when the main pump p1 is driven according to the operation of the engine E, the minimum flow rate is discharged from the main pump p1. Then, the minimum flow rate discharged from the main pump p1 is guided to the switching valve b via the passage 1. However, since the switching valve b is in the neutral position at this time, this flow rate is passed through the passage 2 to the main pump p1. Is returned to the suction port 11. That is, when the switching valve b is in the neutral position, the pressure oil is not supplied to the actuator a and the rotation of the drum D is stopped.

From the above state, for example, when the switching valve b is switched to the upper position in the drawing, the first port 12 and the third port 14 communicate with each other and the second port 13 and the fourth port 15 communicate with each other.
Communicates with. Further, at this time, the controller c controls the swash plate in the direction of increasing the discharge amount of the main pump p1.
Therefore, the pressure oil discharged from the main pump p1 is
It is supplied to the actuator a through the passage 1 → the switching valve b → the passage 5. Then, the return oil from the actuator a is returned to the suction port 11 of the main pump p1 via the passage 6 → the switching valve b → the passage 2.

With the above arrangement, the actuator a operates at a speed corresponding to the amount of pressure oil supplied. Then, the drum D rotates according to the operating speed of the actuator a. The flow rate discharged from the main pump p1 at this time is obtained by multiplying the discharge amount per one rotation of the main pump p1 by the rotation speed of the engine E. Therefore, when increasing the rotation speed of the drum D, the rotation speed of the engine E is increased.

On the contrary, when the switching valve b is switched to the lower position in the drawing, the first port 12 and the fourth port 15 communicate with each other and the second port 13 and the third port 14 communicate with each other. Communicate. Therefore, the actuator a operates in the direction opposite to the above, and the drum D also rotates in the direction opposite to the above. If the flow rate in the circuit becomes insufficient due to oil leakage or the like while the drum D is rotating as described above, the insufficient amount is supplemented by the charge pump p2.

[0010]

A concrete mixer truck for transporting cement rotates the drum D at a high speed when the cement is discharged from the drum D. In addition, the drum D is rotated at high speed just before discharging the cement in order to mix the cement well. However, in the conventional device, in order to rotate the drum D at a high speed, the rotation speed of the engine E must be increased. When the rotation speed of the engine E is increased, the engine sound becomes louder accordingly,
There is a problem that this engine sound becomes noise in a residential area. In other words, this conventional device has a problem that when the operating speed of the actuator is increased, the engine speed increases and the engine noise becomes loud.

If a large main pump p1 is used, a large flow rate is discharged even if the rotation speed is low, so the rotation speed of the engine E does not have to be increased in order to operate the actuator a at high speed. That is, the engine sound when rotating the drum D can be suppressed low. However, since the variable displacement pump is very expensive, the use of the large-sized main pump p1 causes an inconvenience of increasing the cost of the entire apparatus. An object of the present invention is to provide a hydraulic control device that is inexpensive and can increase the operating speed of an actuator without increasing the rotation speed of the engine.

[0012]

A first invention is an actuator, a main pump having an engine as a drive source, a circulation circuit connecting the actuator and the main pump, and a constant displacement type having an engine as a drive source. Sub-pump, a merging passage for merging the discharge oil of the sub-pump into the circulation circuit, a directional switching valve for connecting the sub-pump to the tank or the circulation circuit according to the switching position, and a circulation passage connected to the circulation circuit. A discharge control valve and a pressure control valve provided between the discharge valve and the tank, and the discharge valve maintains a closed position when the sub pump communicates with the tank through the directional control valve. Is configured to maintain the open position when communicating with the circulation passage via the direction switching valve.

A second invention is the same as the first invention,
A throttle valve is provided on the suction side of the sub-pump, which keeps the throttle position when the sub-pump communicates with the tank through the direction switching valve, and the sub-pump communicates with the circulation circuit through the direction switching valve. The feature is that it keeps the open position when it is in motion.

A third invention is the same as the first invention,
A clutch is provided in the transmission means for transmitting the driving force of the engine to the sub-pump, and this clutch links the engine and the sub-pump while the sub-pump is in communication with the circulation circuit through the direction switching valve, while the sub-pump switches the direction. It is characterized in that the connection between the engine and the sub-pump is cut off when communicating with the tank via the valve.

In a fourth aspect of the present invention, an actuator, a main pump having an engine as a drive source, a circulation circuit connecting the actuator and the main pump, and a constant displacement sub-pump having an electric motor as a drive source are provided. A merging passage for joining the discharge oil of the sub-pump to the circulation circuit, a directional switching valve for providing the sub-pump with the tank or the circulation circuit depending on the switching position, and a discharge valve connected to the circulation circuit, A pressure control valve provided between the discharge valve and the tank and a controller for controlling the switching positions of the electric motor and the discharge valve are provided, and in the controller, the sub pump communicates with the tank through the directional switching valve. While operating, the electric motor stops operating, the discharge valve is kept in the closed position, and the sub pump switches direction. When communicating with the circulation passage through, characterized in that the arrangement to keep the discharge valve actuates the electric motor in the open position.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the first embodiment shown in FIG. 1, a variable displacement type main pump P1, a constant displacement type small charge pump P2, and a constant displacement type sub-pump P3 are connected to an engine E output. It is linked to the axis d. The engine E drives the three pumps P1 to P3. The main pump P1 has one port 20 connected to a port 24 of the actuator A via a passage 22. Also, on the other port 21,
The port 25 of the actuator A is connected via the passage 23. The passage 22 and the passage 23 form a circulation circuit. Further, the drum D is linked to the actuator A, and the drum D is rotated according to the operation of the actuator A.

A port 28 of the direction switching valve B is connected to the passage 22 via a confluence passage 26, and the other port 29 of the direction switching valve B is connected to the passage 23 via a confluence passage 27. . The directional control valve B has an inflow port 3
0 through the passage 32 to the discharge port 33 of the sub-pump P3
And the tank T is connected to the outflow port 31. The directional control valve B thus configured allows the inflow port 30 to communicate with the outflow port 31 when in the neutral position shown in the drawing, but allows the inflow port 30 to communicate with the port 28 when switched to the upper position in the drawing. In addition, the direction switching valve B
Is switched to the lower position in the drawing, the inflow port 30 communicates with the port 29.

Suction port 39 of the sub-pump P3
A tank T is connected to the suction passage 38 via a suction passage 38, and a throttle valve 40 is provided in the suction passage 38. When the throttle valve 40 is in the throttle position shown in the drawing, it throttles the suction passage 38 and increases the flow area of the suction passage 38 when switched to the open position on the right side of the drawing. Therefore, if this throttle valve 40 is in the open position,
A predetermined flow rate is discharged from the sub pump P3, but when the throttle valve 40 is switched to the throttle position, the discharge amount of the sub pump P3 becomes very small.

On the other hand, one port 42 of the discharge valve 41 is connected to the flow passage 22 through a passage 36, and the passage 2
The other port 43 of the discharge valve 41 is connected to 3 via a passage 37. The discharge valve 41 has its ports 44 and 45 connected to the tank T via a pressure control valve 46. When the discharge valve 41 is in the neutral position shown in the figure, it blocks communication between the ports 42 to 45 and other ports, but when switched to the right position in the drawing, the port 43 and the port 45 communicate with each other. Then, when the position is switched to the left side in the drawing, the port 42 and the port 44 communicate with each other.

The discharge port 47 of the charge pump P2 is connected to the passage 22 via a check valve 34 and to the passage 23 via a check valve 35. The charge pump P2 is used to compensate for the insufficient flow rate in the passages 22 and 23.

An operating lever R for operating the tilt angle of the swash plate is mechanically linked to the main pump P1. A controller C is connected to the operation lever R, and the operation amount of the operation lever R is input to the controller C. Also, this controller C has
Direction switching valve B, throttle valve 40, and discharge valve 41
Of the respective solenoids s are connected. Then, by controlling the exciting current of each solenoid s by the controller C, the switching positions of the direction switching valve B, the throttle valve 40, and the discharge valve 41 are controlled.

Next, the operation of the first embodiment will be described. When the operation lever R is not operated, that is, when the tilt angle of the swash plate of the main pump P1 is minimum, the discharge amount of the main pump P1 is maintained at substantially zero. Therefore, even if the engine E operates in this state, the pressure oil is not discharged from the main pump P1. Further, when the operation lever R is not operated in this way, the controller C
The throttle valve 40 is kept in the throttle position by the. Therefore, even if the sub-pump P3 is driven, its discharge amount is very small. Then, a small amount of pressure oil discharged from the sub-pump P3 is directly returned to the tank T via the direction switching valve B.

On the other hand, the charge pump P2 discharges a flow rate proportional to the rotation speed of the engine E, regardless of the operating state of the operating lever R. However, this charge pump P2
Compensates for the insufficient flow rate in the passages 22 and 23, and the discharge pressure thereof is set low. Therefore, the actuator A is not operated by the pressure oil discharged from the charge pump P2. Therefore, the operating lever R
Is in the neutral position, the drum D is stopped.

The discharge amount of the sub-pump P3 is controlled to a very small amount for the following reason. That is,
The state where the operation lever R is not operated is a state where it is not necessary to rotate the drum D. If pressure oil is discharged from the sub-pump P3 in spite of such a state, the load on the engine E increases, and energy loss occurs. Therefore, in this embodiment, when the operation lever R is not operated, the load of the engine E is reduced by reducing the discharge amount of the sub pump P3. By doing so, energy loss can be prevented. However, if the discharge amount of the sub-pump P3 is completely set to zero, the sub-pump P3 may be burned. Therefore, the sub-pump P3 is cooled by discharging a small amount.

When the operating lever R is operated from the above-mentioned state, the tilt angle of the swash plate of the main pump P1 increases, so that the main pump P1 discharges a flow rate according to the rotation speed of the engine E. For example, when pressure oil is discharged from the port 20 of the main pump P1, this pressure oil is supplied to one port 24 of the actuator A via the passage 22, and the return oil from this actuator A passes through the passage 23. Is returned to the port 21 of the main pump P1. When the pressure oil is supplied in this way, the actuator A operates and the drum D rotates at a predetermined speed.

When the rotational speed of the drum D is increased from the above state, the direction switching valve B is switched to the upper position in the drawing by a command from the controller C. When the directional control valve B is switched in this way, the inflow port 30 and the port 28
Is connected to the discharge port 33 of the sub-pump P3.
, But communicates with the passage 22 through the passage 32, the directional control valve B, and the merging passage 26. When the direction switching valve B is switched as described above, the throttle valve 40 is switched to the open position by the command from the controller C, and the discharge amount of the sub pump P3 is increased. Then, the flow rate discharged from the sub-pump P3 joins the passage 22 through the joining passage 26. In this way, the oil discharged from the sub-pump P3 is passed through the passage 2
When they are merged with each other, the operating speed of the actuator A is increased, so that the rotation speed of the drum D is also increased. That is, the rotation speed of the drum D can be increased without increasing the rotation speed of the engine E.

Further, when the directional control valve B is switched to the upper position as described above, the discharge valve 41 is switched to the right position in the drawing in response to a command from the controller C. When the discharge valve 41 is switched in this way, the port 43 and the port 45 communicate with each other, so that the passage 23 on the downstream side of the actuator A is connected to the tank T via the passage 37 → the discharge valve 41 → the pressure control valve 46. Communicate. Therefore, a predetermined flow rate of the pressure oil passing through the passage 23 is discharged to the tank T. Then, the predetermined flow rate is a flow rate merged by the sub-pump P3. That is, the flow rate merged by the sub-pump P3 is discharged to the tank T via the discharge valve 41.

The pressure control valve 46 keeps the pressure on the upstream side constant, and its set pressure is the pressure normally generated in the passage 23 when the pumps P1 to P3 are operated. It is set. That is, this pressure compensation valve 46
This prevents the pressure on the downstream side of the actuator A from dropping too much or rising too much.

On the other hand, the main pump P1 is adapted to rotate in the opposite direction to the above. When the main pump P1 is rotated in the opposite direction, pressure oil is discharged from the port 21, so the actuator A rotates in the opposite direction to the above, and the drum D also rotates in the opposite direction. Also, in this state,
When increasing the rotation speed of the drum D, the direction switching valve B is switched to the lower position in the drawing, and the discharge valve 41 is switched to the left side in the drawing. At the same time, the throttle valve 40 is switched to the open position. By doing so, the operating speed of the actuator A is increased and the rotational speed of the drum D is also increased.

In the second embodiment shown in FIG. 2, the throttle valve 40 of the first embodiment is omitted, while the engine E is used.
The sub-pump P3 is linked to the output shaft d of the above through the clutch 48, and this clutch 48 is controlled by the controller C. The other configurations are the same as those of the first embodiment. The clutch 48 is provided with the engine E and the sub pump P3 when the discharge port 33 of the sub pump P3 communicates with the merging passage 26 or the merging passage 27 via the direction switching valve B, that is, when the drum D is rotated at a high speed. And the sub-pump P3 is disconnected from the engine E at other times. That is, the power of the engine E is supplied to the sub pump P only when the clutch D rotates the drum D at a high speed.
I am trying to tell 3.

According to the second embodiment, the sub pump P
The sub-pump P3 is operated only when it is necessary to supply the discharge oil of No. 3 to the actuator A, and the sub-pump P3 is not driven at all in other cases. By doing so, the load on the engine E is reduced when the actuator A does not need to be operated, and thus the energy loss can be reduced.

In the third embodiment shown in FIG. 3, the drive source of the sub-pump P3 is an electric motor M. That is, the sub-pump P3 is linked to the output shaft of the electric motor M, and the rotation speed of the electric motor M is controlled by the controller C. Further, a rotation speed sensor 49 for detecting the rotation speed of the engine E is connected to the controller C.

The controller C includes a rotation speed sensor 4
The discharge amount of the main pump P1 is calculated based on the rotation speed of the engine E detected by 9 and the operation amount of the operation lever R. When it is determined that the calculated discharge amount of the main pump P1 is smaller than the supply flow rate required by the actuator A, the electric motor M is operated. The operation of the electric motor M drives the sub-pump P3 so that the oil discharged from the sub-pump P3 merges with the oil discharged from the main pump P1 to generate the actuator A.
Supply to. That is, the sub-pump P3 is used to supplement the flow rate that is insufficient with the main pump P1 alone. If the required flow rate is replenished in this way, the excess flow rate is not discharged from the sub-pump P3, and energy loss does not occur. The flow rate required by the actuator A is input to the controller C by an input mechanism (not shown).

The third embodiment can also be used for an idling stop vehicle in which the engine E is temporarily stopped when the vehicle is stopped due to a red light or the like. That is, conventionally, when the concrete mixer truck is made to have the idling stop specification, there is a disadvantage that the rotation of the drum D is stopped when the engine is stopped. However, in the third embodiment, since the sub-pump P3 is driven by the electric motor M that is a drive source different from the engine E, even if the engine E is stopped,
The drum D can be rotated by the electric motor M. Therefore, the disadvantage that the rotation of the drum D is stopped does not occur.

The control when the engine E is stopped in the idling state will be specifically described. First, the controller detects the stop of the engine by the detection signal from the rotation speed sensor 49. Then this controller
Based on the operation amount of the operation lever R, the flow rate discharged by the main pump P1 during the operation of the engine E is specified. Then, the rotation speed of the electric motor M is controlled so that the same flow rate as the specified flow rate is discharged from the sub-pump P3.

Although the constant displacement type sub-pump P3 is used in the first to third embodiments, the constant displacement type sub-pump P3 is less expensive than the variable discharge type pump. Therefore, the cost of the entire apparatus can be reduced as compared with the case where the variable displacement main pump is enlarged. That is, according to the first to third embodiments, the operating speed of the actuator can be increased at low cost and without increasing the engine speed. Further, although the concrete mixer truck has been described as an example in the above-described first to third embodiments, the present invention can also be used for other specially-equipped vehicles equipped with actuators such as hydraulic motors and hydraulic cylinders.

[0037]

According to the first aspect of the present invention, the sub-pump having the engine as the drive source is provided, and the flow rate discharged from the sub-pump is merged with the discharge oil of the main pump to be supplied to the actuator. The operating speed of the actuator can be increased without increasing the engine speed. Therefore, it is possible to prevent the engine noise from increasing when the operating speed of the actuator is increased. Further, since the sub-pump is a constant displacement type, it is possible to suppress an increase in the cost of the entire device as compared with the case where the variable displacement type main pump is enlarged.

According to the second aspect of the invention, when the flow rate discharged from the sub-pump is not required, the work amount of the sub-pump can be reduced by the throttle valve, so that energy loss can be prevented.

According to the third aspect of the invention, when the flow rate discharged from the sub-pump is not required, the driving of the sub-pump can be completely stopped, so that energy loss can be further prevented.

According to the fourth aspect of the invention, the flow rate discharged from the sub-pump driven by the electric motor is combined with the discharge oil of the main pump and supplied to the actuator, so that the engine speed is increased. Even without it, the operating speed of the actuator can be increased. Therefore, the engine noise does not become loud even if the operating speed of the actuator is increased. Also, because the sub-pump is driven by a drive source different from the engine,
The actuator can be operated even when the engine is stopped in the idling stop vehicle.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a circuit diagram of a second embodiment.

FIG. 3 is a circuit diagram of a third embodiment.

FIG. 4 is a circuit diagram of a conventional example.

[Explanation of symbols]

A actuator B directional valve E engine M electric motor P1 main pump P3 sub pump d Output shaft corresponding to the transmission means of the present invention 22 Passages constituting the circulation circuit of the present invention 23 Passages constituting the circulation circuit of the present invention 26 Confluence passage 27 Confluence passage 46 Pressure control valve 40 throttle valve 41 discharge valve 46 Pressure control valve 48 clutch

Claims (4)

[Claims] 1. An actuator, a main pump having an engine as a drive source, a circulation circuit connecting the actuator and the main pump, a constant capacity sub-pump having an engine as a drive source, and a discharge oil of the sub-pump. A merging passage that joins the circulation circuit, a direction switching valve that is provided in the merging passage and that connects the sub-pump to the tank or the circulation circuit according to the switching position, a discharge valve that is connected to the circulation circuit, and the discharge valve and the tank. And a pressure control valve provided between the sub-pump and the tank, the closed position is maintained when the sub-pump is in communication with the tank via the direction switching valve, and the sub-pump is connected to the circulation passage via the direction switching valve. A hydraulic control device characterized in that the open position is maintained when communicating with each other. 2. A throttle valve is provided on the suction side of the sub-pump, and the throttle valve maintains the throttle position when the sub-pump communicates with the tank through the direction switching valve, and the sub-pump circulates through the direction switching valve. 2. A structure in which the open position is maintained when communicating with the circuit.
The described hydraulic control device. 3. A clutch is provided in the transmission means for transmitting the driving force of the engine to the sub-pump, which clutch links the engine and the sub-pump while the sub-pump is in communication with the circulation circuit via the direction switching valve. The hydraulic control device according to claim 1, wherein the engine and the sub-pump are disconnected when the sub-pump communicates with the tank via the direction switching valve. 4. An actuator, a main pump having an engine as a drive source, a circulation circuit connecting the actuator and the main pump, a constant capacity sub-pump having an electric motor as a drive source, and a discharge oil of the sub-pump. And a directional switching valve that is provided in the merging passage and that connects the sub pump to the tank or the circulation circuit according to the switching position, a discharge valve connected to the circulation circuit, and the discharge valve. A pressure control valve provided between the tank and a controller for controlling the switching positions of the electric motor and the discharge valve is provided, and the controller, when the sub pump communicates with the tank via the directional switching valve, The operation of the electric motor is stopped, the discharge valve is kept in the closed position, and the sub-pump circulates through the directional valve. A hydraulic control device characterized in that an electric motor is operated and a discharge valve is kept in an open position when communicating with a passage.