JP6331010B2 - Hydraulic drive - Google Patents

Hydraulic drive Download PDF

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JP6331010B2
JP6331010B2 JP2014090346A JP2014090346A JP6331010B2 JP 6331010 B2 JP6331010 B2 JP 6331010B2 JP 2014090346 A JP2014090346 A JP 2014090346A JP 2014090346 A JP2014090346 A JP 2014090346A JP 6331010 B2 JP6331010 B2 JP 6331010B2
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pressure
differential pressure
hydraulic pump
sleeve
actuators
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JP2015209866A (en
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康治 岡崎
康治 岡崎
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株式会社不二越
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  The present invention relates to a hydraulic drive device used in construction machines such as a hydraulic excavator and various work machines, and more specifically, in a hydraulic drive device including a swash plate type variable displacement hydraulic pump (hereinafter referred to as a variable pump), In particular, load sensing that controls the capacity of the variable pump so that the actual differential pressure (hereinafter referred to as PLS pressure) between the discharge pressure of the variable pump and the maximum load pressure of a plurality of actuators is maintained at a certain target differential pressure (hereinafter referred to as Pr pressure). The present invention relates to a hydraulic drive device for control.

Conventionally, this kind of Pr pressure is changed in accordance with changes in engine speed by using a fixed displacement pump (hereinafter referred to as a fixed pump) driven by a prime mover such as an engine together with a variable pump. In order to save energy at the time of traveling operation, there is a technique for detecting the traveling operation and reducing the Pr pressure only during the traveling operation.
In this prior art, the flow rate during operation of the traveling motor is smaller than the flow rate during operation of other actuators (for example, boom cylinders and arm cylinders), but the Pr pressure and PLS pressure are the same regardless of which actuator is operated. Even when a few travel motors are operating, the pressure loss at the flow control valve is the same pressure loss as when a large flow actuator is operating, and the problem is that the energy loss is unnecessarily large. The pressure loss during the traveling operation is reduced by setting the Pr pressure to be low.
However, the pressure loss in the prior art is not linked to the engine speed, and the engine speed is only in the range from medium to high (see, for example, Patent Document 1).

JP 2011-247301 A

  However, in Patent Document 1, although the flow rate during operation of the traveling motor is smaller than the flow rate during operation of other actuators (for example, boom cylinders and arm cylinders), the Pr pressure and PLS pressure are the same regardless of which actuator is operated. Even when the travel motor with a low flow rate is operating, the pressure loss at the flow control valve is the same pressure loss as when the actuator with a large flow rate is operating, and the travel operation is detected to solve the problem that the energy loss is unnecessarily large. Only when the Pr pressure is set low, the pressure loss during the running operation is reduced. However, in the prior art, the pressure loss is reduced without being linked to the engine speed, and the engine speed is only in the region from medium to high.

In the prior art, as shown in FIG. 5, only when the engine speed is from medium to high, Pr pressure decreases like Pr ′ pressure during traveling operation, but Pr pressure remains unchanged at low rotation.
In general, the flow adjustment valve of the travel motor is set so that the travel speed required for the actual machine is obtained at the time of high engine rotation. Accordingly, the opening area is increased because the flow rate adjusting valve is set so that the desired flow rate is obtained in a state where the Pr pressure at the time of high engine rotation is reduced to the Pr ′ pressure.
However, since the Pr pressure does not decrease even when a running operation is detected at a low engine speed, the difference from the Pr ′ pressure at a high engine speed is small. On the other hand, in general, it is halved, but in Patent Document 1, it does not decrease so much theoretically.

Therefore, although the speed of actuators other than traveling varies greatly depending on the engine speed, the actual operator does not decrease the traveling speed even if the engine speed is low, making it difficult to perform fine operations.
Further, except for the circuit example of FIG. 10 in Patent Document 1, in order to reduce the Pr pressure during the running operation, a pressure reducing valve and a throttle are newly added to increase the number of components.
The present invention has been made in order to solve the above-described problems. The absolute value of the target differential pressure is set so that the absolute value of the target differential pressure can be changed only during the traveling operation while maintaining the function of changing the target differential pressure according to the engine speed. It has a differential pressure reducing valve that reduces the pressure loss in the hydraulic circuit during traveling operation and changes the Pr pressure according to the engine speed even during traveling operation. It is an object of the present invention to provide a hydraulic drive device characterized by this.

In order to solve the above problems, the present invention provides:
A prime mover such as an engine, a variable displacement hydraulic pump driven by the prime mover such as the engine, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and the hydraulic pump to the plurality of actuators A plurality of directional control valves for controlling the flow rate of the supplied pressure oil, a plurality of pressure compensating valves for controlling the differential pressure across the plurality of directional switching valves, and a discharge pressure of the hydraulic pump for the plurality of actuators. A pump control means for load sensing that is higher than the maximum load pressure by a target differential pressure, a main relief valve that regulates an upper limit of the discharge pressure of the hydraulic pump, and a target differential pressure of each of the plurality of pressure compensation valves. and it sets the differential pressure between the maximum load pressure in the discharge pressure and the plurality of actuators of the hydraulic pump, the discharge of the fixed pump A differential pressure reducing valve for detecting the differential pressure of the upstream pressure and the downstream pressure when the amount passes through the fixed throttle and the variable throttle, with the differential pressure reducing valve,
A stepped cylindrical sleeve;
A guide fitted to one end of the sleeve;
A pipe joint is screwed to the other end of the sleeve,
A step-shaped spool fitted into a step hole formed in the sleeve;
A spring guide fitted into the stepped hole by the pipe joint;
A retainer fitted to one end of the spool;

And a spring member mounted between the spring guide and the retainer.

According to the present invention, the engine speed is detected by a change in the differential pressure across the throttle installed in the discharge path of the fixed pump, and the target differential pressure Pr pressure of the pump displacement control is changed when the vehicle is not running, so that the variable pump discharge While maintaining the function of changing the actual differential pressure between the pressure and the maximum load pressure, the target differential pressure Pr ′ pressure is set to a pressure lower than the target travel Pr pressure during the travel operation, and the Pr ′ pressure is also set to the engine speed. You can also have a function to change in conjunction.
Further, the pressure loss during the traveling operation can be reduced as in the prior art, and the traveling operation fine operability can be ensured when the engine speed is low.

1 shows a hydraulic control circuit according to a first embodiment of the present invention. FIG. 2 is a characteristic diagram showing a relationship between a target LS differential pressure and an engine speed indicating the characteristics of the hydraulic control circuit in FIG. 1. 3 is a hydraulic control circuit according to a second embodiment of the present invention. FIG. 2 is a schematic longitudinal sectional view showing a schematic structure of a differential pressure reducing valve in FIG. 1. It is a characteristic diagram which shows the relationship of the target LS differential pressure-engine speed which shows the characteristic of the conventional hydraulic control circuit.

DESCRIPTION OF EMBODIMENTS Hereinafter, a hydraulic drive device according to the present invention will be described in detail with reference to the accompanying drawings by giving preferred embodiments.
FIG. 1 shows a hydraulic circuit of a hydraulic drive device 10 according to an embodiment of the present invention, and reference numeral 14 denotes a control valve of the hydraulic drive device 10.
In the present invention, the target pressure difference is detected by the differential pressure reducing valve 31 that detects the differential pressure between the upstream pressure Pp1 (31c) and the downstream pressure Pp2 (31b) when the discharge flow rate of the fixed pump 13 passes through the fixed throttle 30b and the variable throttle 30a. The pressure Pr pressure (31a) is detected.
Here, the pressure receiving area A1 of the upstream pressure Pp1 (31c), the pressure receiving area of the downstream pressure Pp2 (31b) is A2, and the pressure receiving area of the target differential pressure Pr pressure (31a) is A3.
In the present invention, the differential pressure reducing valve 31 is provided with a spring 31d acting in the same direction as the downstream pressure 31b and a pressure chamber 31e for changing the load (elastic force) Fsp of the spring 31d by the traveling operation signal pressure 31f. For the travel operation signal pressure 31f, the pilot pressures 26a, 26b, 27a, 27b for switching the direction switching valve 26 and the direction switching valve 27 for operating the travel motor 16 and the travel motor 17 are selected by the shuttle valves 28, 29, etc. Supply.

  Therefore, when the travel operation signal pressure 31f is supplied to the pressure chamber 31e during the travel operation (travel motor operation) of the travel motors 16 and 17, the spring 31d is bent and the elastic force is increased, so that the differential pressure is different from that when the travel is not performed. The Pr pressure 31a detected by the pressure reducing valve 31 decreases. Further, the discharge flow rate of the fixed pump 12 increases with the increase in the number of revolutions of the engine 11, the differential pressure between the upstream pressure 31c and the downstream pressure 31b increases, and the spool balance position of the differential pressure reducing valve 31 is more upward in the drawing (spring 31d bends). Therefore, as the rotational speed of the engine 11 increases, the spring force of the spring 31d increases. As a result, the higher the rotational speed of the target differential pressure Pr pressure 31a, the higher the differential pressure between the upstream pressure 31c and the downstream pressure 31b. The pressure difference increases.

The characteristics during the running operation are as shown in FIG. 2, and the target differential pressure Pr pressure 31a does not decrease only when the engine speed is medium to high, as in the prior art, but from low engine speed to high engine speed. The target differential pressure Pr pressure 31a decreases over the entire area.
The target differential pressure Pr pressure (31a) , the pump pressure 12b inside the control valve 10 and the high load pressure 21a are guided to the differential pressure reducing valve 31 to the LS valve 23 for adjusting the discharge amount of the variable pump 12 , and the actual differential pressure PLS22 is obtained. And the discharge amount of the variable pump 12 is adjusted so that the actual differential pressure PLS22 becomes equal to the target differential pressure Pr pressure (31a) .

Considering as an extreme example, the spring 31d is in a state in which there is no deflection when the vehicle is not operating, and the spring 31d is bent only during the traveling operation, and the balance of the force of the differential pressure reducing valve 31 where the spring force acts on the differential pressure reducing valve 31. In terms of
Pp1 × A1 = Pp2 × A + Pr × A3 + Fsp (elasticity of spring 31d)
Organize
Pr * A3 = Pp2 * A1-Pp2 * A2-Fsp
The ratio of the pressure receiving areas A1, A2 and A3 of each pressure is set according to the purpose, but in the most general case as a differential pressure reducing valve, if A1 = A2 = A3 is set,
Pr * A1 = Pp1 * A1-Pp2 * A1-Fsp
∴Pr = Pp1-Pp2-Fsp / A1.

When not running: Target differential pressure Pr = Pp1-Pp2 (since Fsp / A1 = 0) (1)

During travel operation: Target differential pressure Pr '= Pp1-Pp2-Fsp / A1 (2)
It becomes.
Therefore, the actual differential pressure PLS22 at the time of running operation = the target differential pressure Pr ′, and the pressure loss during running can be reduced. In addition, the Pr ′ pressure can be changed in the same manner as the target differential pressure Pr pressure when the vehicle is not running in the entire region from the low engine speed to the high engine speed.

FIG. 4 shows another circuit example of the control valve 15. In FIG. 4, the same constituent elements as those of the control valve 14 of FIG.
Therefore, the same function can be obtained by replacing the control valve 14 of FIG. 1 with the control valve 15 of FIG.
FIG. 4 will be described. A difference from the control valve 10 in FIG. 1 is that a line to which a pilot pressure 32 downstream of the discharge line of the fixed pump 13 is inputted is branched and a throttle 33 is arranged.
The downstream of the throttle 33 is connected in series to signal line cutoff circuits 51 and 52 directly connected to the operation direction switching valves 26 and 27 of the travel motors 16 and 17, and is connected to the tank port (T line) in the tank of the control valve 15. It has been done.

Further, the downstream side of the throttle 33 is branched and supplied to the travel operation signal pressure 31f. When the vehicle is not running, the downstream side of the throttle 33 communicates with the tank and has a low pressure of 0.5 MPa or less.
Therefore, the traveling operation signal pressure 31f is 0.5 MPa or less and the spring 31d is in a state where the elastic force is weak. When the direction switching valve 26 or 27 is switched during traveling operation or when the direction switching valves 26 and 27 are switched at the same time and the signal line shut-off circuit 51 or 52 is switched to the shut-off position, the pilot pressure 32 is reduced to the relief pressure. The downstream pressure of 33 is increased and supplied to the travel operation signal pressure 31f, the spring 31d is bent, the elasticity is increased, and as a result, the target differential pressure Pr pressure 31a is decreased.

FIG. 3 shows a schematic structure of the differential pressure reducing valve 31 of the hydraulic drive device 10 according to the embodiment of the present invention.
The differential pressure reducing valve 31 includes a stepped cylindrical sleeve 322, a guide 321 fitted to one end (the left end in FIG. 3) of the sleeve 322, and the other end (the right end in FIG. 3) of the sleeve 322. A pipe joint 315, a stepped spool 312 fitted in a stepped hole 323 formed in the sleeve 322, a spring guide 314 fitted in the stepped hole 323 by the pipe joint 315, A retainer 313 fitted to one end of the spool 312 (the right end in FIG. 3), and a spring member 31 d fitted between the protrusion 314 a of the spring guide 314 and the retainer 313.

On the other hand, the sleeve 322 is provided with a lateral hole 47 in the diameter direction at a position corresponding to the piston 311 , and further, lateral holes 49, 44, 43 communicating with the target differential pressure Pr are formed in the diameter direction.
The spring member 31d is mounted between the protrusion 314a of the spring guide 314 and the retainer 313 fitted to the detail 312a at the other end (right end in FIG. 3) of the sleeve 312.
Reference numerals 316 to 319 denote seal members fitted to the outer periphery of the sleeve 322, for example, an O-ring. From the differential pressure reducing valve 31 when the differential pressure reducing valve 31 is attached to a valve body (not shown). Prevents oil leakage.

Next, the operation of the differential pressure reducing valve 31 will be described.
When the upstream pressure Pp1 (31c) is applied to the left end surface 41 of the piston 310 , a force in the direction of arrow X in FIG. 3 contacts the right end surface of the piston 310 and acts on the spool 312. Further, the downstream pressure Pp2 (31b) is pressurized through the lateral hole 43 of the sleeve 322 to the pressure chamber 42 formed by the step between the outer diameter large portion and the outer diameter small portion of the spool 312 and the inner diameter portion of the sleeve 322. In FIG. 3, a force in the direction of arrow Y acts on the spool 312.

Further, the elastic force of the spring 31d similarly acts on the spool 312 in the direction of arrow Y in FIG. With these inputs, the spool 312 moves in the left-right direction. For example, when the spool 312 moves to the right, the pressure chamber 46 on the right end surface of the spool 312 passes through the internal hole 45 of the spool 312 and the downstream pressure Pp2 via the lateral hole 44 of the sleeve 322. It communicates with (31b) .
Conversely, when the spool 312 moves to the left, the pressure chamber 46 on the right end surface of the spool 312 communicates with the DR port 31g through the inner hole 45 of the spool 312 and the lateral hole 47 of the sleeve 322 to act on the spool 312. The target differential pressure Pr (31a) is output so that the force to be balanced is balanced .

When the travel operation signal pressure 31 f is applied to the pipe joint 315, the piston 311 is pushed leftward and is pushed against the internal step 48 of the sleeve 322. Thereby, the elasticity of the spring 31d is increased by the distance that the piston B 314 has moved.
Accordingly, the pressure receiving area of the left end surface 41 of the piston 310, the stepped portion pressure receiving area of the outer diameter large portion and the outer diameter small portion of the spool 312 of the pressure receiving area chamber 42, and the receiving of the small outer diameter portion of the spool 312 of the pressure receiving chamber 46 are received.

DESCRIPTION OF SYMBOLS 10 Hydraulic drive device 11 Engine 12 Variable pump 13 Fixed pump 14, 15 Control valve 16, 17 Traveling motor 26, 27 Direction switching valve 28, 29 Shuttle valve 30a Variable throttle 30b Fixed throttle 31a Target differential pressure Pr 31b Downstream pressure Pp2
31c Upstream pressure Pp1 31d Spring 31e Pressure chamber 31f Running operation signal pressure 31 Differential pressure reducing valve 32 Pilot pressure 33 Throttle 51, 52 Shut-off circuit 310, 311 Piston 312 Spool 313 Retainer 314 Spring gad 315 Pipe joint 321 Guide 322 Sleeve 323 Stepped Hole

Claims (1)

  1. A prime mover such as an engine, a variable displacement hydraulic pump driven by the prime mover such as the engine, a plurality of actuators driven by pressure oil discharged from the hydraulic pump, and the hydraulic pump to the plurality of actuators A plurality of directional control valves for controlling the flow rate of the supplied pressure oil, a plurality of pressure compensating valves for controlling the differential pressure across the plurality of directional switching valves, and a discharge pressure of the hydraulic pump for the plurality of actuators. A pump control means for load sensing that is higher than the maximum load pressure by a target differential pressure, a main relief valve that regulates an upper limit of the discharge pressure of the hydraulic pump, and a target differential pressure of each of the plurality of pressure compensation valves. and it sets the differential pressure between the maximum load pressure in the discharge pressure and the plurality of actuators of the hydraulic pump, the discharge of the fixed pump A differential pressure reducing valve for detecting the differential pressure of the upstream pressure and the downstream pressure when the amount passes through the fixed throttle and the variable throttle, with the differential pressure reducing valve,
    A stepped cylindrical sleeve;
    A guide fitted to one end of the sleeve;
    A pipe joint is screwed to the other end of the sleeve,
    A step-shaped spool fitted into a step hole formed in the sleeve;
    A spring guide fitted into the stepped hole by the pipe joint;
    A retainer fitted to one end of the spool;
    A spring member mounted between the spring guide and the retainer;
    A hydraulic drive device comprising:
JP2014090346A 2014-04-24 2014-04-24 Hydraulic drive Active JP6331010B2 (en)

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JP6331010B2 true JP6331010B2 (en) 2018-05-30

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Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20010053054A (en) * 1999-05-28 2001-06-25 세구치 류이치 Pump capacity control device and valve device
JP5383591B2 (en) * 2010-05-24 2014-01-08 日立建機株式会社 Hydraulic drive unit for construction machinery

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