JPH0444121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic device, and relates to a hydraulic device suitable for driving a truck mixer, for example.

(Prior Art) An example of a conventional hydraulic device for a track mixer is shown in FIG. As shown in the figure, this hydraulic device has a discharge line 103 connecting a pump 101 and a motor 102.
A flow direction control valve 105 is interposed between the flow direction control valve 1 and the return flow line 104 from the motor 102.
05 to open and close the discharge line 103 and return line 104, the motor 1
It controls driving, stopping, etc. of 02. Note that 106 indicates a reduction gear, and 107 indicates a mixer drum. When stopping the rotation of the mixer drum 107 in the above device,
The flow direction control valve 105 is positioned at the neutral position to close both the flow paths of the discharge line 103 and the return flow line 104, but at this time, the mixer drum 1
The motor 102 acts as a pump due to the inertia of the drum 107, and high pressure is generated in the return line 104, causing the drum 107 to suddenly stop and cause a shock. In order to prevent this phenomenon, crossover type relief valves 108 and 109 are interposed between the discharge line 103 and the return line 104. That is, a structure is adopted in which the high pressure generated in the return flow line 104 is relieved to the discharge line 103 side by the relief valve 108. In addition, as mentioned above, the pair of relief valves 108 and 10 are oriented in opposite directions.
9 is provided because the discharge line 103 and the return flow line 104 are reversed when the mixer drum 107 rotates forward and backward.

(Problems to be Solved by the Invention) By the way, in the relief valve 108 in the hydraulic device as described above, fluid must not be relieved from the relief valves 108 and 109 when the mixer drum 107 is driven. It is necessary to set the set pressure higher than the circuit operating pressure.
Therefore, when the mixer drum 107 is stopped, the relief valve 108 cannot operate unless the pressure in the return line 104 reaches a high pressure higher than the set pressure, and at this time, the relief valve 108 is subjected to surge pressure. In reality, it is difficult to completely prevent the sudden stop of the mixer drum 107 and the occurrence of a shock in the above-mentioned apparatus.

This invention was made in view of the above, and its purpose is to prevent sudden stops and shocks as described above when stopping the drive of a driven body such as a mixer drum, and to achieve a smooth stop. Another object of the present invention is to provide a hydraulic device that can save power.

(Means for Solving the Problems) Therefore, in the hydraulic device of the present invention, a load sensing valve is used to switch and connect the discharge amount control section 11 of the variable displacement hydraulic pump 1 to the discharge line 3 and the tank 15. 12, and an all-port block type flow rate directional control valve 5 having a flow rate adjustment section for controlling the flow rate from the hydraulic pump 1 to the motor 2,
The load sensing valve 12 has a pilot chamber 16 on which the pressure of the discharge line 3 acts, and a spring chamber 17 opposing the pilot chamber 16. It has a load pressure detection port d for detecting rear pressure, and a vent passage 9 that communicates the load pressure detection port d with the tank 10 in the neutral position, while connecting the flow rate directional control valve 5 and the motor 2. A relief valve 23 is provided as a branch in the return flow line 4, and a pilot relief valve 31 is connected via a pilot line 29 to a spring chamber 27 opposing the pilot chamber 25 of this relief valve 23. A spring chamber 33 opposing the chamber 32 and the load sensing valve 12
The spring chamber 17 was connected to the load pressure detection port d of the flow rate directional control valve 5.

(Function) As a result of the above, when the flow rate directional control valve 5 is in the switching connection and the motor 2 is being driven, the fluid pressure downstream of the flow rate adjustment section is transferred from the load pressure detection port d to the pilot relief valve 31. spring chamber 3
3, and the pressure of the spring chamber 27 of the relief valve 23 acts on the pilot chamber 32 via the pilot line 29. This relief valve 23
The pressure of the return flow line 4 acts on the spring chamber 27 and the pilot chamber 25. This return line 4
Since the pressure is low, the relief valve 23 and the pilot relief valve 32 will not be relieved. In other words, the pressure in the spring chamber 33 of the pilot relief valve 31 is the sum of the fluid pressure in the discharge line 3 and the fluid pressure corresponding to the spring force of the pilot relief valve 31; Since the pressure in the chamber 32 is equal to the low pressure in the return line 4, the pilot relief valve 31 is closed and no relief occurs. On the other hand, since the fluid pressure of the return flow line 4 is led to the pilot chamber 25 and spring chamber 27 of the relief valve 23 as described above, both chambers 25 and 27 have the same pressure, and even the spring force of the spring chamber 27 Then, the relief valve 23 is closed. Therefore, the relief valve 23 does not perform a relief operation in this state, that is, while the motor 2 is being driven.

When stopping the drive of the motor 2,
The flow direction control valve 5 is switched to the neutral position to close the discharge line 3 and the return flow line 4. Then, the spring chamber 33 of the pilot relief valve 31 communicates with the tank 10 via the load pressure detection port d and the vent passage 9. As a result, the pressure in the spring chamber 33 of the pilot relief valve 31 is reduced to a fluid pressure corresponding to the spring force, and the fluid pressure acting on the spring chamber 27 of the relief valve 23 is also reduced. Therefore, the fluid in the return line 4 is relieved with a fluid pressure corresponding to the spring force of both the pilot relief valve 31 and the relief valve 23. As a result, by adjusting the forces of both springs, when stopping a driven body such as a mixer drum, it is possible to relieve the fluid in the return line 4 with a fluid pressure that does not generate a large inertial force on the driven body. This makes it possible to prevent the driven body from suddenly stopping and causing a shock.

Furthermore, when the load pressure detection port d is opened to the tank 10 by switching the flow rate directional control valve 5 to the neutral position, the pressure in the spring chamber 17 of the load sensing valve 12 decreases, thereby controlling the discharge amount. The fluid pressure of the discharge line 3 acts on the portion 11, and the discharge amount of the hydraulic pump 1 is significantly reduced to approximately zero.

(Example) Next, a specific example in which the hydraulic device of the present invention is applied to a drive circuit for a track mixer will be described in detail with reference to the drawings.

In FIG. 1, 1 is a variable displacement hydraulic pump, 2 is a hydraulic motor, and both 1 and 2 are connected by a discharge line 3 and a return line 4.
A flow rate directional control valve 5 is interposed between both lines 3 and 4. In this case, the pair of lines 3a and 4a on the motor 2 side are connected to the flow rate directional control valve 5, such that when one of them is connected to the discharge line 3, the other is connected to the return line 4. The connection state changes depending on the switching position, but for convenience, one side will be called a discharge line 3 and the other side will be called a return line 4 as shown in the figure. Note that 6 indicates a speed reducer connected to the motor 2, and 7 indicates a mixer drum.

The flow rate directional control valve 5 is an all-port block type having both the functions of a directional control valve and a flow rate control valve, and has a pump port P, a tank port T, two cylinder ports A and B, and It has a load pressure detection port d. This load pressure detection port d is for detecting the load pressure downstream of the flow rate adjustment section (not shown) via the feedback passage 8 when the flow rate directional control valve 5 is located at the switching position. When the flow direction control valve 5 is located at the neutral position, the vent passage 9
It is connected to the tank 10 through the.

The variable displacement hydraulic pump 1 includes a swash plate control cylinder 11 as a discharge amount control section for controlling its discharge amount, and a load sensing valve 12 that controls the supply of fluid to the cylinder 11. ing. The swash plate control cylinder 11 moves the swash plate toward the neutral position to reduce the discharge amount when fluid is introduced into the cylinder 11, and on the other hand, when the fluid in the cylinder 11 is discharged, The force of the spring 13 moves the swash plate in the direction of inclination, thereby increasing the discharge amount. The load sensing valve 12 switches the line 14 connected to the swash plate control cylinder 11 into communication with the discharge line 3 and the tank 15, and the fluid in the discharge line 3 enters the pilot chamber 16.
Further, the pressures detected at the load pressure detection ports d of the flow rate direction control valve 5 are respectively introduced into the spring chambers 17, and are opposed to each other. Now, the flow direction control valve 5
is in the neutral position, the fluid pressure in the discharge line 3 tends to rise rapidly since the discharge line 3 is blocked. At this time, the fluid pressure in the discharge line 3 is guided to the pilot chamber 16 of the load sensing valve 12, and the spring chamber 17 thereof is communicated with the tank 10 via the load pressure detection port d, so that the load sensing valve 12 is switched to the switching position S1, and the fluid in the discharge line 3 is led into the swash plate control cylinder 11 via the line 14. As a result, the swash plate moves to the neutral position and no fluid is discharged from the variable pump 1. On the other hand, when the flow rate directional control valve 5 is located at the switching position, in the load sensing valve 12, the fluid pressure of the discharge line 3 is applied to the pilot chamber 16, and the flow rate directional control valve 5 is applied to its spring chamber 17. The fluid pressures downstream of the flow rate adjusting section are respectively guided to face each other. And this load sensing valve 12
When the fluid pressure in the pilot chamber 16 is high, the swash plate control cylinder 1 is located at the switching position S1.
1 and reduces the discharge amount from the pump 1. Conversely, when the pressure in the spring chamber 17 is high, the swash plate control cylinder 11 is moved to the tank 15.
The pump 1 operates to increase the discharge amount from the pump 1. As a result, the differential pressure before and after the flow rate adjusting section of the flow direction control valve 5 is always maintained at a pressure corresponding to the spring force of the load sensing valve 12, that is, the pressure is compensated.

Note that the line 14 is further provided with a safety switching valve 41, which is connected to the discharge line 3.
Acts when the fluid pressure reaches a predetermined pressure or higher,
It directs the fluid in the discharge line 3 to the swash plate control cylinder 11 and stops the supply of further fluid from the pump 1. Further, a charge pump 18 is added to the pump 1, and a line 19 and a check valve 20 are connected from the charge pump 18.
It is possible to supply fluid to the return flow line 4 via. In addition, 21 is a relief valve, and the above-mentioned line 19 is connected by this relief valve 21.
It regulates the fluid pressure inside.

On the other hand, between the discharge line 3 and the return line 4 on the motor 2 side of the flow direction control valve 5, there is a relief valve 22 for relieving the fluid in one line 3 to the other line 4. On the contrary, a relief valve 23 for relieving the fluid in the line 4 to the other line 3 is interposed, and each pilot chamber 24, 25 of each relief valve 22, 23 has a fluid on its primary side. The pressure is guided respectively. Further, each spring chamber 26, 27 of each relief valve 22, 23 is guided to a shuttle valve 30 by a pair of pilot lines 28, 29, and this shuttle valve 3
The highest pressure selected by 0 is introduced into the primary side of the pilot relief 31. In this pilot relief valve 31, fluid pressure on its primary side is introduced into its pilot chamber 32, and fluid pressure on its secondary side is introduced into its spring chamber 33. The secondary side of the pilot relief valve 31 is connected to the load pressure detection port d of the flow rate directional control valve 5 via a line 34.

The specific structures of the relief valves 22, 23, shuttle valve 30, and pilot relief valve 31 are shown in FIG. Relief valves 22, 23 as shown
is a balance piston type, and the main body 3
The main valve 36 is slidably disposed within the main valve 5, and a pilot valve 37 is in contact with the main valve 36. The shuttle valve 30 has a valve body 39 that slides within a main body 38, while the pilot relief valve 31 is a direct acting relief valve having a poppet valve 40.

Next, the operating state of the hydraulic device will be described, but first, the state in which the motor 2 is being driven will be described. In this case, the flow rate directional control valve 5
It is assumed that the motor 2 is located at the switching position S1 and the motor 2 is rotating normally. In this state, the relief valves 22 and 23 interposed between the discharge line 3 and the return line 4 do not operate as described below. That is, the spring chambers 26 and 27 of the relief valves 22 and 23 are connected to the shuttle valve 30 via the pilot lines 28 and 29, and are further connected to the pilot relief valve 31.
In this pilot relief valve 31, the pilot line 28,
29, and the fluid pressure on the secondary side of the pilot relief valve 31 is introduced into the spring chamber 33, respectively. By the way, the secondary side of the pilot relief valve 31 is connected to the load pressure detection port d of the flow rate directional control valve 5 via the line 34, so in this state, the secondary side of the pilot relief valve 31 is The fluid pressure downstream of the flow rate adjustment section of the flow direction control valve 5 acts. On the other hand, fluid pressure on the higher pressure side of the pilot lines 28 and 29 acts on the pilot chamber 32 of the pilot relief valve 31 via the shuttle valve 30, but this fluid pressure acts on the spring chamber 33. Since the pressure does not exceed the sum of the fluid pressure corresponding to the spring force and the fluid pressure corresponding to the spring force, the pilot relief valve 31 is not relieved. In this way, within the pilot lines 28 and 29,
That is, the spring chambers 26, 2 of the relief valves 22, 23
7 is maintained, while the fluid pressure in the discharge line 3 and return line 4 never becomes higher than the pressure in the spring chambers 26, 27 of the relief valves 22, 23. , 23 are never activated. In addition, if the motor 2 etc. stops for some reason while the motor 2 is being driven as described above and the fluid pressure in the discharge line 3 increases abnormally, the pilot shown in Fig. 2 Valve 3
7 is activated and releases the fluid in the spring chambers 26, 27 to the return line 4. As a result, the spring chambers 26, 27
The fluid pressure in the discharge line 3 decreases, opening the main valve 36 and releasing the fluid in the discharge line 3 to the return line.

Next, when the drive of the motor 2 is to be stopped, the flow direction control valve 5 is returned to the neutral position. Then, both the discharge line 3 and the return line 4 are closed, but at the same time, the load pressure detection port d is also communicated with the tank 10. As a result, the secondary side of the pilot relief valve 31, that is, its spring chamber 33, is also opened to the tank 10. Therefore, the fluid in the pilot lines 28 and 29 is relieved by a fluid pressure corresponding to the spring force of the spring chamber 33, and the fluid pressure acting on the spring chamber 27 of the relief valve 23 becomes low, and the return line 4 The fluid is relieved to the discharge line 3 with a fluid pressure corresponding to the spring force of both the pilot relief valve 31 and the relief valve 23.

As a result of the above, if the spring force of the pilot relief valve 31 and the relief valves 22 and 23 is adjusted according to the inertia of the mixer drum 7, sudden stops and shocks of the mixer drum 7 can be prevented, and smooth operation can be achieved. Deceleration characteristics can be obtained. In addition, the above results
It is also possible to adjust the time from switching the lever of the flow direction control valve 5 to stopping the mixer drum 7. Furthermore, if the above structure is adopted, the relief valves 22 and 23, the shuttle valve 30, and the pilot relief valve 31 can be built into the motor end cap, so the entire structure can be made compact. Become.

Although one embodiment of the hydraulic device of the present invention has been described above, the hydraulic device of the present invention is not limited to the above embodiment, and can be implemented with various modifications. For example, in the above example, the hydraulic device is used as a drive device for a track mixer, but the use of this hydraulic device is not limited to this.
In addition, the above example shows an example in which a pair of relief valves are installed in the discharge line and the return line, but this is done in consideration of forward and reverse rotation of the motor, and the relief valve is only installed in the return line. For example, a structure may be adopted in which the discharge is connected to a tank instead of the discharge line.

(Effect of the invention) According to the hydraulic device of this invention, the flow direction control valve 5
By the switching operation, the set pressure of the relief valve 23 connected to the return flow line 4 can be set high when the motor 2 is running and low when the motor 2 is stopped, and the set pressure of the relief valve 23 connected to the return flow line 4 can be set low when the motor 2 is stopped. By switching to the neutral position, the pilot relief valve 3
1 and the spring chamber 17 of the load sensing valve 12 are opened from the load pressure detection port d to the tank 10 via the vent passage 9, so when the motor 2 is stopped, the relief valve 23 and the pilot relief valve 31 are closed. The fluid in the return line 4 can be relieved even with a low set pressure corresponding to both spring forces. Therefore, unlike in the prior art, the driven body driven by the motor does not suddenly stop or a shock occurs at that time, and the driven body can be stopped smoothly.

In addition, the load sensing valve 12 is omitted because it guides the fluid pressure in the discharge line to the discharge amount control unit 11 due to the pressure drop in the spring chamber 17, and significantly reduces the discharge amount of the hydraulic pump 1 to approximately zero. Aiming for power becomes movable.

Moreover, since the single flow direction control valve 5 controls the operation of two valves, the relief valve 23 and the load sensing valve 12, the operation and structure are simplified.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the hydraulic device of the present invention, FIG. 2 is an explanatory diagram showing the structure of its main parts,
FIG. 3 is a circuit diagram of a conventional example. 1...Pump, 2...Motor, 3...Discharge line, 4...Return line, 5...Flow rate directional control valve,
9... Vent passage, 10... Tank, 11... Swash plate control cylinder (discharge amount control section), 12... Load sensing valve, 16... Pilot chamber, 17...
...Spring chamber, 22, 23...Relief valve, 24, 2
5... Pilot chamber, 26, 27... Spring chamber, 2
8, 29...Pilot line, 31...Pilot relief valve, 32...Pilot chamber, 33...
...Spring chamber, 34...Line, d...Load pressure detection port.

Claims (1)

[Claims] 1 Discharge amount control unit 11 of variable displacement hydraulic pump 1
, a load sensing valve 12 which is selectively connected to the discharge line 3 and the tank 15, and an all-port block type flow rate directional control valve 5 having a flow rate adjustment section that controls the flow rate from the hydraulic pump 1 to the motor 2. The load sensing valve 12 has a pilot chamber 16 on which the pressure of the discharge line 3 acts, and a spring chamber 17 opposed to the pilot chamber 16, and the flow rate directional control valve 5 controls the flow rate in the switching position. It has a load pressure detection port d that detects the pressure downstream of the adjustment section, and a vent passage 9 that communicates the load pressure detection port d with the tank 10 in the neutral position, while the flow rate directional control valve 5 and the motor 2 A relief valve 23 is provided as a branch in the return flow line 4 that connects the valve, and a pilot relief valve 31 is connected via a pilot line 29 to a spring chamber 27 of the relief valve 23 that opposes the pilot chamber 25. 31 and a spring chamber 33 opposing the pilot chamber 32 and the spring chamber 17 of the load sensing valve 12 are connected to the load pressure detection port d of the flow direction control valve 5.