JP2001182705A - Warming structure for hydraulic pilot controlled hydraulic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a warming structure for a hydraulic pilot controlled hydraulic circuit that can clear way at least either nonconformity of or demand for conventional warming, if not, a totally renewed warming structure. SOLUTION: This hydraulic pilot controlled hydraulic circuit includes a warming structure, such that pressured oil is delivered into pilot lines (13L, 13R) via a shut-off valve (16) to provide warmth to the both pilot lines (13L, 13R), when an operation lever 11 is in neutral position. This warming structure includes a directional control valve (1), which has communication lines (1fL, 1fR) at both ends of a spool (1b) when the spool (1b) is in the neutral position, such that a drain chamber (1e) of a valve body (1a) and pilot pressure chambers (1cL, 1cR) are made to communicate via the communication lines (1fL, 1fR). The both communication lines (1fL, 1fR) are arranged and a communication passage area of one side (1fL or 1fR) of the communication lines is gradually increased in proportion to a sliding distance amount of the spool (1b), when the spool is moved from the neutral position to one side, while a communication passage area of other side (1fR or 1fL) of the communication lines is decreased gradually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a warm-up structure for a hydraulic circuit operated by a hydraulic pilot.

[0002]

2. Description of the Related Art Most hydraulic circuits include a directional control valve between a hydraulic pump and a hydraulic actuator, and switch the directional control valve to switch the flow of pump discharge oil to operate the hydraulic actuator. The direction switching valve includes a spool that is constantly biased in a neutral direction by a neutral spring provided at both ends, and a valve body that slidably fits the spool inside.
The spool slides inside the valve body and opens based on the operation amount of the operation lever. To slide the spool in this way,
In order to further reduce the operation force of the operation lever and further remote control, the directional control valve has pilot pressure receiving chambers at both ends of the spool and connects the ends of the pilot pipes to both pilot pressure receiving chambers, respectively. A pilot oil pressure control valve with an operation lever is provided at the base end. A typical example of a pilot oil pressure regulating valve is a proportional pressure reducing valve (hereinafter referred to as a “PPC valve”).
(Pressure Proportional Control) ”).
The PPC valve connects the base ends of both pilot lines to the tank when the operation lever is neutral, and at the same time, when operating the operation lever, applies a pilot oil pressure proportional to the operation amount to the operation side pilot pressure receiving chamber via the operation side pilot line. And leave the proximal end of the non-operating pilot line connected to the tank.

[0003] By the way, the pilot oil in both pilot lines basically has only the sliding amount of the spool,
Only the C valve leaning part goes in and out. That is, most remain in both pilot lines. Therefore, in cold regions, the viscous resistance increases due to the low temperature of the oil in both pilot pipelines, which increases the operating force of the operating lever, and the directional control valve does not operate as expected even when the operating lever is operated, or Inconveniences such as malfunction of the hydraulic actuator occur.

For example, in a construction machine such as a hydraulic power shovel equipped with an engine for driving a hydraulic pump, oil is forced to flow into both pilot lines when the engine is started at a low temperature and the operating lever is neutral. There is a type in which the oil is circulated between the tanks (configuration) to increase the oil temperature in both the pilot lines and the inside thereof to reduce the viscous resistance of the oil (effect).

Further, Japanese Patent Publication No. 4-29884 discloses that
"The two pilot pressure chambers at both ends of the spool are connected to the drain chamber in the valve body (that is, the drain chamber to the tank) by communication paths, and only the flow from the drain chamber to each pilot pressure chamber is connected to both communication paths. A check valve is provided (constitution) to allow the hydraulic oil in the drain chamber to flow from both communication passages to the tank through the two pilot pressure receiving chambers, the two pilot pipelines, and the PPC valve in this order when the directional control valve is neutral. A technique (effect) of draining (working), raising the oil temperature in both pilot lines and the inside thereof by this oil flow to reduce the viscous resistance of the oil (effect) is described.

[0006]

However, the above-mentioned prior art has the following disadvantages.

[0007] The configuration in which the oil is forcibly flown into the two pilot lines and circulated between the tank and the tank when the engine is started at a low temperature and the operating lever is neutral is forced warm air.
The warm air is limited to “when the engine is started at a low temperature and when the operating lever is neutral”. That is, after the warming-up, the oil in the two pilot pipes, which has been raised in temperature by the forced warming, stops as before and gradually cools down due to the external cool air, thereby invalidating the previous warming or reducing the warming effect. The operating force of the operating lever gradually increases, and the directional switching valve does not operate as expected even if the operating lever is operated, or the hydraulic actuator gradually malfunctions. May occur.

In the technology described in Japanese Patent Publication No. 4-29884, the warming effect can be expected because "the hydraulic pressure in the drain chamber is higher than the hydraulic pressure in the pilot pressure receiving chamber" and "both pilot lines and both pilot pressure receiving sections". When the oils in the chambers have the same viscous drag. " By the way, as is known, the viscosity resistance of oil increases as the temperature decreases, and the rate of increase in the viscosity resistance sharply increases as the temperature decreases. For example, hydraulic oil EO10-
The pour point of CD is about -25 ° C. In construction machines such as hydraulic power shovels, bulldozers, and wheel loaders, it is common for the engine to start and operate below freezing even without a heating device such as a heater. However, the hydraulic pressure in the drain chamber of the construction machine before starting the engine at such an outside temperature is not high enough to push the oil in the pilot pipeline to the tank against the viscous resistance sharply increased by the low temperature. Rather, there is a concern that the check valve will not even open due to the viscous resistance of the oil at a hydraulic pressure of the drain chamber level. That is, it can be considered that the warming effect can be obtained based on the technology described in Japanese Patent Publication No. 4-29884 only when the outside air temperature is at most about 5 ° C. or more. Moreover, both pilot pipes usually have different lengths and bends from each other due to the positional relationship with the peripheral members. Therefore, in a cold region, the difference in the viscous resistance of the oil between the two pilot lines is large, so that even if one check valve is opened, the other check valve remains in a closed state.

The following is desired in a hydraulic pilot operated hydraulic circuit. The drive source of the hydraulic pump is an engine 8 mounted on a construction machine, for example. Accordingly, in construction machines and the like operating in a cold region, the warm-up of the engine at the time of low-temperature start of the engine and the warm-up of the hydraulic pilot-operated hydraulic circuit (hereinafter simply referred to as “circuit warm-up”) start warming in synchronization with each other. It is desired to end.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described inconveniences and demands, and has as its object to provide a warm-up structure for a hydraulic circuit operated by a hydraulic pilot-operated hydraulic circuit, which can solve at least one of them.

[0011]

In order to achieve the above object, a warm-up structure of a hydraulic pilot-operated hydraulic circuit according to the present invention is firstly described with reference to FIGS. A spool 1b is slidably fitted in the body 1a, a drain chamber 1e to the tank 9 is provided in the valve body 1a, and pilot pressure receiving chambers 1cL and 1cR are provided at both ends of the spool 1b of the valve body 1a. 1 cL, 1
Neutral spring 1 that constantly urges spool 1b in the neutral direction to cR
dL, 1dR and both pilot pressure receiving chambers 1cL, 1cR
To the pilot pressure chamber 1cL (or 1cR) through one of the pilot lines 13L (or 13R), and thereby the spool 1b is connected to the valve body. 1a is slid from the neutral position to the other side, and the directional switching valve 1 which supplies the discharge oil of the hydraulic pump 2 to the hydraulic actuator 3 from the opening opened by the sliding to operate the hydraulic actuator 3
When the operation lever 11 is in the neutral position, the pilot lines 13L and 13R are communicated with the tank 9 when the operation lever 11 is in the neutral position.
When operating the operating lever 11, the operating pilot line 13L
(Or 13R) is provided with a pilot oil pressure of a pressure corresponding to the operation amount of the operation lever 11, and a pilot oil pressure control valve 10 having a pilot oil pressure regulating valve 10 for communicating the non-operation side pilot line 13R (or 13L) to the tank 9. When the operating lever 11 is in neutral with respect to the hydraulic system, both pilot lines 1
3L, 13R and / or both pilot pressure receiving chambers 1cL, 1cR are provided with an on-off valve 16 for allowing pressure oil to flow freely.
1 At the time of neutral, both pilot lines 13L,
13R and / or a warm-up structure of a hydraulic pilot-operated hydraulic circuit that allows pressure oil to flow into both pilot pressure receiving chambers 1cL and 1cR to warm up both pilot lines 13L and 13R (hereinafter referred to as a "first basic warming structure"). The directional control valve 1 has communication passages 1fL, 1fR at both ends of the spool 1b for communicating the drain chamber 1e of the valve body 1a with the pilot pressure receiving chambers 1cL, 1cR when the spool 1b is in the neutral position. In the passages 1fL and 1fR, when the spool 1b slides from the neutral position to one side, the communication area of the communication passage 1fL (or 1fR) on one side gradually increases in accordance with the sliding amount, and the communication passage 1fR (or on the other side). 1 fL) is formed so that the communication area gradually decreases.

According to the first configuration, the following operation and effect can be obtained. The first configuration (first basic warming structure) of the first configuration substantially corresponds to the former of the prior art, and the latter configuration is substantially similar to the latter of the prior art. However, the communication passages 1fL and 1fR in the latter stage of the first configuration are the same as those of the prior art (Japanese Patent Publication No. 4-29884).
However, the present invention does not employ a configuration in which a check valve that allows only the flow from the drain chamber to each pilot pressure receiving chamber is provided in both communication passages. Therefore, the disadvantage of the prior art that "the check valve does not open even due to the viscous resistance of the oil due to the low temperature" basically does not occur. In addition, the structure is simplified and economical. In addition, the following remarkable effects are obtained. (1) Left and right pilot pressure receiving chamber 1 when operating lever 11 is in neutral
Since the cL and 1cR communicate with the drain chamber 1e via the two communication passages 1fL and 1fR, the left and right pilot pressure receiving chambers 1cL and 1cR basically have the same pressure. Therefore, both pilot lines 13L, 1
The difference in the viscous resistance of the oil between the two pilot lines 13L and 13R in the cold state based on the difference in the length and bend of the 3R can be easily offset. That is, it becomes easy to warm up the circuit. (2) The operating lever 1 during hydraulic work, even during warm air
1 Both the communication passages 1fL and 1fR
Since the bubbles contained in the oil in L and 13R are discharged to the tank 9, the switching accuracy of the directional control valve 1 is improved. (3) When the operation lever 11 is in a neutral state during hydraulic operation, even if the oil in the drain chamber 1e is small, it flows into the left and right pilot pressure receiving chambers 1cL and 1cR via the two communication paths 1fL and 1fR.
When operating the operating lever 11, the operating side pilot pressure receiving chamber 1cL
The pilot oil (or 1cR) flows into the drain chamber 1e via the operation-side communication passage 1fL (or 1fR) and returns. Therefore, as in the former of the prior art, the oil in both pilot lines 13L and 13R, which has been raised in temperature after the end of warming, stops there and gradually cools down by external cool air to invalidate the previous circuit warming. There is no inconvenience of reducing the warming effect. (4) Especially in cold weather, both pilot lines 13L, 13R
Pilot lines 13 based on differences in length and bend between them
There is a concern that a large difference may occur in the viscosity resistance of the oil between L and 13R. However, the communication passages 1fL and 1fR are
When b slides from the neutral position to one side, the communication area of the communication path 1fL (or 1fR) on one side gradually increases according to the amount of sliding,
In addition, the communication passage 1fR (or 1fL) on the other side is formed so that the communication area thereof gradually decreases. Therefore, even if the spool 1b in the neutral position slightly moves in the direction of the operation position due to the difference in the viscous resistance between the two pilot lines 13L and 13R (note that the spool 1b does not move).
If it moves greatly, the directional control valve 1 will switch to the operating position, and the actuator 3 will malfunction during warm-up.), A communication area difference will occur between the two communication passages 1fL, 1fR, and this communication will occur. The area difference offsets the difference in viscous drag,
The spool 1b is returned to the direction for maintaining the neutral position. That is, when the circuit is warmed up, the directional control valve 1 is slightly switched to one of the left and right operation positions, and the actuator 3
The erroneous operation of slight movement does not occur, so that early warm-up can be performed efficiently. That is, the first configuration can solve the disadvantages of the prior art, or can be a completely new structure for warming up the hydraulic pilot operated hydraulic circuit.

Secondly, referring also to FIGS. 1 to 3, a spool 1b is slidably fitted in the valve body 1a, and pilot pressure receiving chambers 1cL, 1cL are provided at both ends of the spool 1b of the valve body 1a. 1cR, both pilot pressure receiving chambers 1cL, 1cR
Neutral spring 1 that constantly urges spool 1b in the neutral direction to cR
dL, 1dR and both pilot pressure receiving chambers 1cL, 1cR
The pilot line 13L, 13R is connected to one of the two pilot lines 13L, 13R, and the pilot pressure is applied to one of the pilot pressure receiving chambers 1cL, 1cR via one 13L (or 13R) of the two pilot lines 13L, 13R so that the spool 1b is in the valve body 1a. From the neutral position to the other side, and the discharge valve of the variable displacement hydraulic pump 2 is supplied to the hydraulic actuator 3 from the opening opened by the sliding to actuate the hydraulic actuator 3, and the operation lever 11; When the operating lever 11 is in neutral, the two pilot lines 13L and 13R are communicated with the tank 9. On the other hand, when the operating lever 11 is operated, the operating side pilot line 13
L (or 13R) is provided with a pilot oil pressure of a pressure corresponding to the amount of operation of the operation lever 11, and a pilot oil pressure control valve 10 for connecting the non-operating pilot line 13R (or 13L) to the tank 9 is provided. An operation type hydraulic circuit, further including a first spring 2b1 at one end side, receiving the first spring force P1 of the first spring 2b1 and the maximum load pressure PLs of the hydraulic actuator 3 at one end side, and In response to the discharge pressure Pp of the variable displacement hydraulic pump 2, "Pp = PLs
+ P1 ", an LS valve 2b for increasing or decreasing the discharge amount of the variable displacement hydraulic pump 2, a second spring 5a at one end, and a second spring force P2 of the second spring 5a at one end and a hydraulic actuator. And an unload valve 5 receiving the discharge pressure Pp of the variable displacement hydraulic pump 2 at the other end thereof, and the directional control valve 1 is set at a neutral position in the valve body 1a. In contrast to a closed center type hydraulic pilot operated hydraulic circuit having a drain chamber 1e for draining the maximum load pressure PLs applied to the valve 2b and the unload valve 5 to the tank 9, when the operating lever 11 is in neutral, both pilot lines 13L, 13R And / or both pilot pressure receiving chambers 1cL, 1cR
An opening / closing valve 16 for allowing the pressure oil to flow freely is provided, and both pilot lines 13
L, 13R and / or a warm-up structure of a hydraulic pilot-operated hydraulic circuit that allows pressure oil to flow into both pilot pressure receiving chambers 1cL, 1cR to warm up both pilot lines 13L, 13R (hereinafter referred to as "second basic warm-up"). Structure)), the directional control valve 1 includes communication passages 1fL, 1fR at both ends of the spool 1b for communicating the drain chamber 1e of the valve body 1a with the pilot pressure receiving chambers 1cL, 1cR when the spool 1b is in the neutral position. When the spool 1b slides from the neutral position to one side, the communication area of the communication path 1fL (or 1fR) on one side gradually increases and the communication path 1fR on the other side, when the spool 1b slides from the neutral position to one side. (Or 1 fL) is formed so that the communication area gradually decreases.

According to the second configuration, the following operation and effect can be obtained. The latter configuration of the second configuration is the same as the latter configuration of the first configuration. The second configuration differs from the first configuration in that the preceding configuration of the second configuration is a lower concept of the first configuration. Therefore, according to the second configuration, the operation and effect of the first configuration described in the first configuration can be directly obtained. In other words, the second configuration can also solve the disadvantages of the prior art, or provide a completely new structure for warming up the hydraulic pilot operated hydraulic circuit. Note that the former configuration of the second configuration is different from the front end configuration of the first configuration in that the technical ideas of the second to eighth configurations (all of which are lower concepts of the second configuration), which will be described later in detail, are the first configuration. This is because it cannot be grasped from the preceding configuration.

Third, referring to FIG. 1, in the above-described "second basic warming structure", the maximum load pressure PLs is led to the LS valve 2b through a conduit for guiding the maximum load pressure PLs to the LS valve 2b. LS instead of maximum load pressure introduction position and maximum load pressure PLs
A second direction switching valve 17 is provided which is capable of switching a pump pressure introducing position for guiding the pump discharge pressure Pp to the valve 2b.

According to the third configuration, the following operation and effect can be obtained. When the second directional control valve 17 is switched from the maximum load pressure introducing position to the pump pressure introducing position when the operating lever 11 is in the neutral position, the pump discharge capacity is maximized, and the pump discharge oil is completely drained from the unload valve 5 to the tank 9. At this time, the drain oil is heated by the unload pressure P1. This heated oil passes through the on-off valve 16 and the pilot line 13L,
13R (or left and right pilot pressure receiving chambers 1cL, 1cR) can efficiently heat the circuit in cold weather.

Fourth, referring to FIG. 1, in the above-mentioned "second basic warm-up structure", the directional control valve 1 has the drain chamber 1e of the valve body 1a and the two pilot pressure receiving chambers 1cL when the spool 1b is in the neutral position. , Communication passage 1f communicating with 1cR
L and 1fR are provided at both ends of the spool 1b, and the two communication passages 1fL and 1fR are connected to one communication passage 1fL (or 1fL) according to the sliding amount when the spool 1b slides from the neutral position to one side.
fR) gradually increases and the communication area of the other side communication passage 1fR (or 1fL) gradually decreases, and the LS valve 2b introduces the maximum load pressure PLs to the LS valve 2b.
A maximum load pressure introduction position for guiding the maximum load pressure PLs to the valve 2b;
Pump discharge pressure Pp to LS valve 2b instead of maximum load pressure PLs
And a second direction switching valve 17 having a switchable pump pressure introducing position for guiding the pressure.

According to the fourth configuration, the respective functions and effects of the second and third configurations are obtained by being superimposed.

Fifth, referring to FIG. 1, in the "second basic warming structure", the unloading valve 5 is capable of changing the second spring force P2 of the second spring 5a. It is characterized by.

According to the fifth configuration, the following operation and effect can be obtained. The second spring force P2 of the second spring 5a of the unload valve 5
That the unloading pressure is changeable means that the unload pressure is changeable. The higher the unload pressure, the more efficiently the drain oil in the unload valve 5 rises in temperature. Therefore, if the operating lever 11 is neutralized and the unloading pressure is increased in cold weather, the circuit can be warmed up efficiently and early.

Sixth, referring to FIG. 1, in the warming-up structure of the hydraulic pilot-operated hydraulic circuit of the third or fourth configuration, the unload valve 5 is connected to the second spring 5a of the second spring 5a.
It is characterized in that the spring force P2 can be changed freely.

According to the sixth configuration, the following operation and effect can be obtained. If the second spring force P2 of the second spring 5a of the unloading valve 5 can be changed freely in the warming-up structure of the hydraulic hydraulic circuit operated by the hydraulic pilot-operating circuit of the third configuration, each effect of the third and fifth configurations can be obtained. Are superimposed on each other. On the other hand, in the warm-up structure of the hydraulic pilot-operated hydraulic circuit of the fourth configuration, the second spring force P2 of the second spring 5a of the unload valve 5
Can be changed, it is possible to obtain the respective effects of the fourth and fifth configurations in a superimposed manner.

Seventh, referring to FIG. 1, in the warming-up structure of the hydraulic pilot-operated hydraulic circuit of the sixth configuration, the on-off valve 16 is opened when warming-up starts when the operating lever 11 is neutral.
With this, pressurized oil flows into both pilot pipelines 13L, 13R and / or both pilot pressure receiving chambers 1cL, 1cR,
The second directional control valve 17 is set at the pump pressure introducing position, and / or the second spring force P2 of the second spring 5a of the unload valve 5 is increased. 13L, 13R and / or stop the flow of pressurized oil into both pilot pressure receiving chambers 1cL, 1cR,
It is characterized by including a controller (14) for returning the directional control valve 17 to the maximum load pressure introducing position and / or returning the second spring force P2 of the second spring 5a of the unload valve 5 to its original state.

According to the seventh configuration, the following operation and effect can be obtained. Recently, the controller 14 is a widely used general-purpose device. Therefore, the operation program of the seventh configuration can be easily and inexpensively inserted into the existing controller 14. Further, not only the functions and effects of the above-described second to seventh configurations can be obtained, but also the maintenance and inspection of the warm-up structure of the hydraulic pilot-operated hydraulic circuit can be easily performed without imposing a burden on the operator. Therefore, not only the disadvantages of the prior art can be solved, but also a completely new structure for warming up the hydraulic pilot operated hydraulic circuit.

Eighthly, referring to FIG. 1, in the warming-up structure of the hydraulic pilot operated hydraulic circuit of the seventh configuration, the variable displacement hydraulic pump 2 is driven by the engine 8 and the controller 14 And an operation program for starting and terminating warm-up of the engine 8 in synchronization with the warm-up start and warm-up end of the hydraulic pilot-operated hydraulic circuit.

According to the eighth configuration, the following operation and effect can be obtained. Since the controller 14 has an operation program for starting and ending the warm-up of the engine 8 in synchronization with the warm-up start and the warm-up end of the hydraulic pilot-operated hydraulic circuit,
It can start and end by associating both warm airs. Note that this synchronization is not limited to the meaning that the start time and the end time are the same, but indicates a relationship in which at least one warmed state affects the other warmed state. For example, in an embodiment described later, the engine speed is automatically increased from 1000 rpm at low idling to 1400 rpm at the time of engine warm-up, thereby improving the circuit warm-up and the warm-up efficiency. That is, according to the eighth configuration, the conventional demand can be solved.
Alternatively, a warm-up structure of a completely new hydraulic pilot operated hydraulic circuit is provided.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a hydraulic pilot-operated hydraulic circuit of a hydraulic power shovel (hereinafter simply referred to as "example machine") (hereinafter simply referred to as "hydraulic circuit").
It is. In the following description, center, left, right, left, right,
The term “up and down” or “upright” indicates the state or operation direction of each element on the drawing. First, the basic circuit of the hydraulic circuit will be described.

The functional characteristics of this basic circuit will be described in advance. This basic circuit is described as follows. When the directional control valve 1 switches from the center neutral position to the left and right operation positions, the opening area A (not shown) of the directional control valve 1 becomes larger or smaller. Pressure difference ΔP across the directional control valve 1
(Not shown) variable displacement hydraulic pump 2
Of the directional control valve 1 automatically changes.
(The amount of oil passing through the hydraulic circuit is proportional to the opening area A).
It is one form of). In order to facilitate understanding, this basic circuit configuration will be described operatively.

The basic circuit includes a variable displacement hydraulic pump 2 (hereinafter simply referred to as "pump 2") and a plurality of hydraulic actuators 3 (hereinafter simply referred to as "actuator 3").
And a relief valve 4 (for example, a so-called main relief valve with a relief pressure of 30 MPa) and an unload valve 5. The direction switching valve 1 includes a shuttle valve 6 and pressure compensating valves 7L and 7R.
(Hereinafter collectively referred to as “pressure compensating valve 7”) for each actuator 3. In FIG. 1, only one actuator 3 and its related elements 1, 6, and 7 are described in detail, and other actuators and their related elements are schematically indicated by reference numeral Z.
The symbol K is a general term for the shuttle valve 6 among these Z.

The directional control valve 1 is of a closed center type, and a spool 1b is mounted on a valve body 1a as shown in detail in FIG.
The pilot pressure receiving chambers 1cL and 1cR are provided at the left and right end portions of the spool 1b of the valve body 1a.
The left and right pilot pressure receiving chambers 1cL and 1cR are provided with neutral springs 1dL and 1dR which constantly bias the spool 1b in a neutral direction.

The pump 2 is driven by the engine 8 and includes a servo cylinder 2a and an LS valve 2b (Load Sensing). The servo cylinder 2a extends to reduce the capacity of the pump 2, and shortens to increase the capacity of the pump 2. Details are as follows.

The servo cylinder 2a is connected to the left pressure receiving chamber 2aL.
The return pressure 2aR (large pressure receiving area side) is connected to the output port of the LS valve 2b.

The LS valve 2b is provided with a first spring 2b1 at the right end face of the LS valve 2b for guiding the pump discharge oil to the input port. The LS valve 2b constantly receives the pump discharge pressure Pp in the left pressure receiving chamber 2bL, and the plural actuators 3 are provided in the right pressure receiving chamber 2bR. The maximum load pressure PLs is acceptable. Here, assuming that the hydraulic pressure equivalent to the first spring force P1 of the first spring 2b1 is "P1", "Pp> PLs + P1"
, The LS valve 2b becomes the left position, and supplies the pump discharge oil to the right pressure receiving chamber 2aR of the servo cylinder 2a. As a result, the servo cylinder 2a extends to reduce the capacity of the pump 2. On the other hand, when "Pp <PLs + P1", the LS valve 2b switches to the right position. Then, the oil in the right pressure receiving chamber 2aR of the servo cylinder 2a is reduced by the spring force of the return spring 2as of the left pressure receiving chamber 2aL of the servo cylinder 2a and the pump discharge pressure Pp.
Drain the tank 9 through the right side position of the S valve 2b. As a result, the servo cylinder 2a is shortened and the capacity of the pump 2 is increased. That is, the LS valve 2b automatically performs "pump displacement variable control" so that "Pp = PLs + P1".

The shuttle valve 6 is as follows. The above LS valve 2b
Has been described as "accepting the maximum load pressure PLs of the plurality of actuators 3 in the right pressure receiving chamber 2bR". Incidentally, the load pressures Pl of the plurality of actuators 3 are usually different from each other. That is, the shuttle valves 6 compare the two load pressures Pl for each shuttle valve 6 and sequentially output the high pressure side. That is, the output of the last shuttle valve 6 becomes the maximum load pressure PLs, which is led to the LS valve 2b. The maximum load pressure PLs is also guided to a pressure compensating valve 7 described below.

The pressure compensating valve 7 also has the maximum load pressure PLs as described above.
Receive. In this basic circuit, the inlet pressure of the directional control valve 1 is the pump discharge pressure Pp. Therefore, in order to achieve the first functional feature "so that the differential pressure ΔP (not shown) of the directional control valve 1 becomes constant", the outlet pressure PLss at the left and right operation positions of each directional control valve 1 is required. All must be the maximum load pressure PLs (PLss = PLs). And "PLss = P
“Ls” is the pressure compensating valve 7. That is, as shown in FIG. 1, the pressure compensating valve 7 receives the maximum load pressure PLs and the outlet pressure PLss of the directional control valve 1 on both end faces, and receives “P
If Lss <PLs, the switching valve is switched to the shut-off position for the actuator 3, while if “PLss> PLs”, the switching valve 7a is switched to the communication position for the actuator 3
Is provided. Simply put, the switching valve 7a is "PLs = PLss
"Automatic variable aperture" that switches between the shut-off position and the communication position so that As shown in FIG. 1, when the directional control valve 1 is in the neutral position, the outlet pressure PLss is changed to the drain chamber 1e.
Through the tank 9. That is, the outlet pressures PLss of the other directional control valves 1 except the directional control valve 1 at the neutral position are all the maximum load pressures PLs. The pressure compensating valve 7 is a switching valve 7
A check valve 7b is provided downstream of a. Therefore, even when the directional control valve 1 is in the neutral position, the load pressure Pl of the actuator 3 is maintained.

That is, the LS valve 2b is set to "Pp = PLs +
The pump displacement variable control is automatically performed so as to be "P1", while the pressure compensating valve 7 is automatically throttled so that "PLss = PLs". As a result, when the directional control valve 1 is switched from the neutral position to the left and right operation positions, the directional control valve 1 is switched regardless of the opening area A.
Is constant. " still,
The "front-back differential pressure ΔP" here is the hydraulic pressure P1 (= Pp-PLs) corresponding to the first spring force of the spring 2b1 for the LS valve 2b, and "Pp-PLss = Pp-PLs" for the directional control valve 1. "
It is nothing less than.

Then, the flow rate Q flowing through the throttle is “Q∝A ·
ΔP1 / 2 ”, where the“ throttle ”corresponds to the directional control valve 1. Therefore, “A” is the opening area A of the directional control valve 1. Further, “ΔP” is a hydraulic pressure P1 equivalent to the first spring force.
Therefore, it is a constant value. Therefore, all of the initial functional characteristics "the directional control valve 1 is proportional to ..." are achieved.

The unload valve 5 is as follows. Pressure compensation valve 7
As described in the above, "The directional control valve 1 has the outlet pressure PLs
s to the tank 9 via the drain chamber 1e ". That is, when all of the directional control valves 1 are at the neutral position, the maximum load pressure PLs applied to each of the pressure compensating valves 7 and the LS valve 2b becomes the tank pressure (PLs ≒ 0). Therefore, at this time, the LS valve 2b maintains the left side position to balance the pump discharge pressure Pp only with the hydraulic pressure P1 equivalent to the first spring force of the first spring 2b1, greatly expands the servo cylinder 2a, and minimizes the pump capacity. Direction. However, since all the directional control valves 1 are in the neutral position, there is no place for the pump discharge oil to go, and the pump discharge oil drains completely from the unload valve 5 to the tank 9 (that is, unloads). Details are as follows.

As shown in FIG. 1, the unload valve 5 receives the pump discharge pressure Pp and the maximum load pressure PLs facing the upper and lower pressure receiving surfaces, and has a second spring 5a on the pressure receiving side of the maximum load pressure PLs. . Here, assuming that the hydraulic pressure equivalent to the second spring force P2 of the second spring 5a is "P2", if "P2 <P1" is satisfied, the LS valve 2b operates the hydraulic pressure P corresponding to the first spring force of the first spring 2b1.
The above-mentioned "pump displacement variable control" by 1 cannot be performed.
Therefore, it is naturally "P2>P1"("P1 = 2.2 MPa" and "P2 = 3 MPa" in this basic circuit). That is, if at least one of the directional control valves 1 is in the left or right operation position, the pump 2 is automatically controlled in the discharge capacity by the servo cylinder 2a and the LS valve 2b so that "Pp = PLs + P1". If all of the valves 1 are in the neutral position, "Pp = P2" and the entire amount of pump discharge oil drains from the unload valve 5 to the tank 9 (that is, "Pp = P2").
2 "is the unload pressure).

That is, the basic circuit of FIG.
"The hydraulic pump 3 includes a hydraulic actuator 3 which is capable of stopping or activating the discharge oil of the variable displacement hydraulic pump 2 by switching the direction switching valve 1 and having a first spring 2b1 on one end side and a first spring 2b1 on one end side. First spring force P of one spring 2b1
1 and the maximum load pressure PLs of the actuator 3 and the discharge pressure Pp of the pump 2 on the other end side, so that "Pp> PLs +
At the time of "P1", the discharge amount of the pump 2 is reduced, while "Pp"
LS to increase the discharge of pump 2 when <PLs + P1 ”
A valve 2b (that is, an LS valve 2b for increasing or decreasing the discharge amount of the pump 2 so that "Pp = PLs + P1"); and a second spring 5a at one end, and a second spring 5a of the second spring 5a at one end. An unload valve 5 receiving the force P2 and the maximum load pressure PLs of the actuator 3 and receiving the discharge pressure Pp of the pump 2 at the other end;
b and the maximum load pressure PLs to the unload valve 5
e, a load-sensing type hydraulic circuit that is a closed-center switching valve that drains to the tank 9 via e.

The warm-up structure of the basic circuit includes the pilot oil pressure regulating valve and the pilot line described in the section of "Prior Art", and also includes respective elements described in detail later. First, the pilot oil pressure regulating valve and the pilot line will be described with reference to FIG.

The pilot oil pressure regulating valve 10 is
Left side PPC valve 10L which operates when 1 is tilted to the left
And right-side PPC valve 10R that operates when tilted to the right
It is composed of Each of the PPC valves 10L and 10R receives, as a primary pressure, pump discharge oil reduced to 3 MPa (same as the unload pressure P2) by a second pressure reducing valve 12 shown. That is, the PPC valves 10L and 10R are
When 1 stands upright and neutral, the primary pressure is cut off from the respective pilot lines 13L and 13R (left pilot line 13L and right pilot line 13R) and the left and right pilot lines 13L and 13R are connected to the tank 9. That is, the directional control valve 1 is connected to the two pilot pressure receiving chambers 1 by the connection.
cL, 1cR oil pressure becomes tank 9 pressure, and the left and right neutral springs 1
The neutral position is established by the balance between dL and 1dR. Therefore,
The directional control valve 1 closes and the actuator 3 does not operate.
On the other hand, if the operating lever 11 is tilted leftward, the left PPC valve 10L reduces the primary pressure to a secondary pressure (pilot oil pressure) proportional to the operation amount (tilting amount) of the operating lever 11, This secondary pressure is applied to the left pilot line 1
After 3L, it is led to the left pilot pressure receiving chamber 1cL. At this time, the right PPC valve 10R keeps the right pilot line 13R connected to the tank 9. Therefore, the spool 1b
Moves to the right in the valve body 1a until the pilot oil pressure in the left pilot pressure receiving chamber 1cL balances the spring force of the right neutral spring 1dR and stops. Thereby, the directional control valve 1
Is opened by an amount proportional to the operation amount of the operation lever 11. When the direction switching valve 1 is opened, the pump discharge oil flows to the actuator 3, and the actuator 3 is operated (the illustrated hydraulic cylinder 3 is extended). The operation lever 11
Is tilted rightward from the neutral position, the actuator 3 operates in the opposite direction to that described above (the hydraulic cylinder 3 shown is shortened).

The components are an additional mechanism 1f of the directional control valve 1, a controller 14, an oil temperature detector 15, an on / off valve 16, a second directional control valve 17, an unload pressure variable mechanism 5b, an engine warm-up mechanism 18, and a hydraulic work start. The setting dial 19, the check valve 20, and others. Hereinafter, description will be made in order.

As shown in FIGS. 2 and 3 (a partially enlarged view of FIG. 2), the additional mechanism 1f of the direction switching valve 1 is a communication passage 1fL, 1fR provided in a groove shape at both ends of the spool 1b. The left communication passage 1fL communicates from the left pilot pressure receiving chamber 1cL to the drain chamber 1e in the valve body 1a, while the right communication passage 1fR communicates from the right pilot pressure receiving chamber 1cR to the drain chamber 1e. The two communication passages 1fL, 1fR are small passages having a smaller diameter than the inner diameter of each of the pilot pipe lines 13L, 13R and a smaller cross-sectional area than the pressure receiving area of the spool 1b in each of the pilot pressure receiving chambers 1cL, 1cR. The communication hole 1g shown in FIG. 3 is a passage for communicating the outlet pressure PLss to the drain chamber 1e when the direction switching valve 1 is neutral, as described above. Further, the respective valves (without reference numerals) below and on the left and right of the direction switching valve 1 in FIG. 2 are abnormal pressure prevention valves that are omitted in FIG. 1 (the description is omitted because it is not related to the present invention). Reference numeral 1h shown in FIGS. 1 and 2 is a check valve for reinforcing the amount of oil (this is also not related to the present invention, and the description is omitted).

The controller 14 is composed of a microcomputer or the like, stores various operation programs in advance, is electrically connected to the hydraulic operation start setting dial 19 and other elements to be described later by electric wires, and based on the various operation programs. Various signals are exchanged with each element.

The oil temperature detector 15 is provided in the tank 9,
The oil temperature to in the tank 9 is detected and input to the controller 14. The oil temperature detector 15 may be provided on the discharge side of the pump 2 or on the pilot lines 13L and 13R.

The on-off valve 16 guides the pump discharge oil intermittently into respective pilot lines 13L, 13R provided downstream of the check valves 20 through the check valves 20 arranged in parallel with each other. The valve 16 may guide the pump discharge oil directly into the pilot pressure receiving chambers 1cL and 1cR). On-off valve 1 in FIG.
Reference numeral 6 denotes a solenoid type, which opens when receiving a signal S1 from the controller 14 (left position), and closes when there is no signal S1 by its own spring force (right position). Hereinafter, the signal S1
Is "open signal S1". It may be closed by receiving a signal from the controller 14 and opened by a self-spring force when there is no signal.

The second directional control valve 17 is provided in a conduit for guiding the maximum load pressure PLs to the LS valve 2b, and includes an upper position (a maximum load pressure introduction position) for guiding the maximum load pressure PLs to the LS valve 2b, and a maximum load pressure. Instead of PLs, a lower position (pump pressure introduction position) for guiding the pump discharge pressure Pp is provided so as to be switchable. The presence of the second directional control valve 17 is explained by the description of the LS valve 2b. "The LS valve 2b is capable of receiving the maximum load pressure PLs of the plurality of actuators 3 in the right pressure receiving chamber 2bR."
It is the cause of "acceptable" in The second directional control valve 17 shown in FIG. 1 is of a solenoid type and receives a signal S2 from the controller 14 to be at the pump pressure introducing position, and the signal S2
When there is no, return to the maximum load pressure introduction position by the self-spring force. Hereinafter, signal S2 is referred to as "pump pressure introduction signal S2". It is also possible to switch to the maximum load pressure introduction position in response to a signal from the controller 14 and to return to the pump pressure introduction position by its own spring force when there is no signal.

The variable unload pressure mechanism 5b is provided with a second spring 5a.
Is a proportional solenoid that can change the second spring force (i.e., the unload pressure P2).
, The second spring force P2 is increased as the signal Sa becomes larger, and the second signal P2 is output when there is no signal Sa.
Return to spring force P2. Hereinafter, the signal Sa is referred to as an “unload pressure change signal Sa”. In this example, the unload pressure P2 is "3 MPa", but when the unload pressure change signal Sa is input, the pressure is increased to "4 MPa".

The engine warm-up mechanism 18 is
, An engine start switch 18a, an engine speed setting dial 18b, an engine coolant temperature detector 18c, an engine speed detector 18d, and a fuel adjusting motor 18e.

The hydraulic work start setting dial 19 is manually operated by an operator at a plurality of stages (for example, 0 ° C., 1
0 ° C, 20 ° C) or stepless (for example, 0 to 20 °)
In C), one set oil temperature tos is input to the controller 14.

Therefore, the controller 14 executes the following operation program example (that is, an example of how to use the warm-up structure of the hydraulic circuit in FIG. 1). Prior to the description of the operation program, the state of the example machine before starting the engine and the specifications of the example machine will be described.

The state of the example machine before starting the engine is as follows.
The outside temperature is minus 10 ° C. The engine speed setting dial 18b is simply a fuel lever or a fuel dial that is manually operated by an operator, and freely sets an idle speed Nes of the engine 8 (≒ 1000 rpm (low idle) to 2200 rpm (high idle)). Things. Here, since the engine is not yet started, the state at the time of the previous stop of operation, that is, “Ne = 1000 rpm” corresponding to low idle. Operation lever 1
Reference numeral 1 denotes a state at the time of the previous operation stop, that is, a neutral position.

The specifications of the example machine are as follows. The engine 8 is a diesel engine with a mechanical all-speed governor. In other words, the engine speed Ne is set to "Nes1000-1000" by the engine speed setting dial 18b.
The fixed point freely set within the range of "2200 rpm" is set as an upper limit (no-load maximum rotation speed), and is a rotation speed that changes vertically according to the magnitude of the engine load. Supplementally, the fuel adjusting motor 18e is a motor that can tilt the governor fuel lever. The pump 2 has a maximum discharge amount of approximately 250 L / at the time of engine partial idle (= 1400 rpm).
min.

The operator sets the hydraulic work start setting dial 19 to, for example, "10 ° C. (= tos)".
Then, the engine 8 is started by the engine start switch 18a.

When the controller 14 receives the engine start signal Ss from the engine start switch 18a, the set oil temperature tos (= 10 °) from the hydraulic work start setting dial 19 is received.
C) is stored. Then, from the oil temperature detector 15, the oil temperature to
The engine cooling water temperature detector 1 receives a signal of the idle speed Nes from the engine speed setting dial 18b.
8c, the engine temperature detector 18d
Receives the engine speed Ne from the engine. Here, when the oil temperature to and the water temperature tw are both 30 ° C. or less, the controller 14 outputs the open signal S1 to open the on-off valve 16, outputs the pump pressure introduction signal S2, and outputs the pump pressure introduction signal S2 to the second directional control valve 17 Is switched from the maximum load pressure introduction position to the pump pressure introduction position, and the unload pressure change signal Sa is input to the unload pressure variable mechanism 5b to increase the second spring force P1 of the second spring 5a. Further, if “Ne = 1400 rpm”, the controller 14 sends “Ne = 1400 rpm” to the fuel adjusting motor 18e.
pm "of the motor drive signal Sm.

As described above, since the engine is started when the outside air temperature is minus 10 ° C. as described above, both the oil temperature to and the water temperature tw are minus 10 ° C. "Nes
= 1000 rpm ". Therefore, the controller 14 outputs the open signal S1, the pump pressure introduction signal S2, the unload pressure change signal Sa, and the motor drive signal Sm corresponding to "Ne = 1400 rpm".

The operation and effect of the dual warm air structure based on the above operation program will be described.

(1) When starting the engine, as described above,
Since "the operation levers 11 are all in the neutral position", "all the PPC valves 10L, 10R and all the directional control valves 1 are in the neutral position". For this reason, the maximum load pressure PLs applied to the LS valve 2b
Is the tank pressure (PLs ≒ 0 MPa). Therefore, if the hydraulic circuit is simply composed of the above basic circuit,
Although the discharge amount of the pump 2 becomes minimum, in the first embodiment, the controller 14 switches the second directional control valve 17 to the pump pressure introducing position by the pump pressure introducing signal S2. Therefore, the maximum load pressure PLs (s0M) is applied to the LS valve 2b.
Instead of Pa), the pump discharge pressure Pp is introduced. Therefore, the pump discharge pressure Pp acts on the left and right pressure receiving chambers 2bL and 2bR of the LS valve 2b so that they are balanced with each other.
The first spring force P1 of b1 switches the LS valve 2b to the right position. This maximizes the pump displacement. Here, since the controller 14 sets “Ne = 1400 rpm”, the pump discharge pressure amount is “250 L / min”. The pump discharge pressure Pp at this time is equal to the unload pressure P2 raised by the unload pressure change signal Sa.
(= 4 MPa), and this pressure oil drains from the unload valve 5 to the tank 9. Then, the oil temperature rises at the time of draining, and the oil temperature to in the tank 9 is raised. At the same time,
Since the open / close valve 16 is opened by the open signal S1, the oil in the tank 9 whose temperature is increasing passes through the pump 2, passes through the open / close valve 16, passes through the check valve 20, and passes through all the directional control valves 1. (Or left and right pilot pressure receiving chambers 1cL, 1cR). At the same time as draining from the communication passages 1fL and 1fR at both ends of the spool 1b to the tank 9 via the drain chamber 1e in the valve body 1a, each PP
Drain into tank 9 via C valves 10L and 10R. Therefore, the temperature of the oil in both pilot lines 13L and 13R also rises due to the oil flow against the viscous resistance. That is, the temperature rise due to the oil flow and the temperature rise due to the unloading are superimposed to reduce the viscous resistance of the oil, thereby achieving the circuit warm-up at an early stage.

(2) The engine speed Ne changes from low idle (≒ 1000 rpm) to partial idle (= 14) according to the motor drive signal Sm from the controller 14.
00 rpm), the engine warm-up proceeds at the same time.

Next, an example of a program for ending the circuit warm-up and the engine warm-up (hereinafter referred to as "both warm-up") will be described.

The end of engine warm-up is determined by the controller 14
Is performed by returning the motor drive signal Sm to a signal corresponding to the idle speed Nes (1000 rpm in the first embodiment) based on the engine speed setting dial 18b. The operator can determine the end of the engine warm-up by experiencing the automatic descent of the engine speed Ne. However, a signal such as a buzzer and / or a lamp that emits a signal when the air is warm and stops the signal when the air is finished may be added. Thereafter, the operator sets the idle speed Nes to a desired value (# 1000 to 2200 rpm) by using the engine speed setting dial 18b.

On the other hand, the end of the circuit warm-up
4 is an open signal S1 to the on-off valve 16 and a second directional control valve 17
Pressure introduction signal S2 and unload pressure variable mechanism 5
This is performed by stopping the output of the unload pressure change signal Sa to the control signal b.

That is, the example of the activation of the warm-up ending program by the controller 14 is one of the following (a) and (b) or the earlier one.

(A) Both warm-up airs are terminated when, for example, 10 minutes have elapsed from the start of the engine. That is, the controller 1
4 receives the engine start signal Ss from the engine start switch 18a, activates a built-in counter for counting clock time, and ends both warm-ups after 10 minutes.

(B) The circuit warm-up is terminated at "to = tos (= 10 ° C.)" and the engine warm-up is terminated at "tw = 30 ° C." For example, at the end of circuit warm-up (ie,
"To = tos (= 10 ° C.)", “tw ≦ 30 °
C "and unless the idle speed Nes is increased by the engine speed setting dial 18b," Ne = 1400r
pm ”and keep the engine warm. However, the idle speed Nes can be freely set to, for example, “Ne ≦ 1600 rpm” by the engine speed setting dial 18b. Specifically, even if “tw ≦ 30 ° C.”, “Nes ≦
1600 rpm "can be achieved. On the other hand, if “tw> 30 ° C.”, the engine warm-up has been completed, and the engine speed Ne once returns to low idle at the end of the engine warm-up, but the operator uses the engine speed set dial 18b to set “Ne ≦≦ 2”.
The hydraulic load operation at an arbitrary value of "200 rpm" can be achieved.

The other effects of the first embodiment are as follows.

(A) According to the additional mechanism 1f of the direction switching valve 1, the following operation and effect can be obtained. (A1) When the operation lever 11 is neutral, the left and right pilot pressure receiving chambers 1cL and 1cR are connected to the drain chamber 1e via the two communication passages 1fL and 1fR.
, The left and right pilot pressure receiving chambers 1cL, 1cR basically have the same pressure. Therefore, both pilot lines 13L,
The difference in the viscous resistance of the oil between the two pilot lines 13L and 13R in the cold state due to the difference in the length and the bending of the 13R can be easily offset. That is, it becomes easy to warm up the circuit. (A2) The operation lever 11 during the hydraulic operation, whether during warm-up or when the operation lever 11 is neutral during the hydraulic operation
During operation, the two communication paths 1fL and 1fR are connected to the pilot line 1
Since the bubbles contained in the oil in the 3L, 13R are discharged to the tank 9, the switching accuracy of the directional control valve 1 is improved. (A3) When the operation lever 11 is in a neutral state during hydraulic operation, even if the oil in the drain chamber 1e is small, the two communication passages 1fL, 1fR
Flows into the left and right pilot pressure receiving chambers 1cL and 1cR via the control lever 11 while the operating lever 11 is operated.
cL (or 1cR) of pilot oil flows into the drain chamber 1e via the operation-side communication passage 1fL (or 1fR) and is returned. Therefore, as in the prior art, the oil in the pilot lines 13L and 13R, which have been raised in temperature after the completion of warming, stops there and gradually cools down by external cool air to invalidate the previous circuit warming. Does not occur. (A4) The communication paths 1fL and 1fR are the same as those of the prior art
Instead of the technique described in JP-A-29884, “a check valve that allows only the flow from the drain chamber to each pilot pressure receiving chamber in both communication passages”, each pilot line 13 is used.
It is a small passage having a smaller diameter than the inner diameter of L, 13R and a smaller sectional area than the pressure receiving area of each pilot pressure receiving chamber 1cL, 1cR. Therefore, inconveniences of the prior art such as "the check valve does not open even due to the viscous resistance of oil due to low temperature" basically do not occur. In addition, the structure is simplified and economical.

(B) In the operation program example (method example) of the first embodiment, the hydraulic work start setting dial 19 is used.
Was set to “tos = 10 ° C.”, but 0 ° C., 20 ° C.
Alternatively, they can be set steplessly, and the respective effects can be obtained. For example, if “tos = 0 ° C.”, the operation force of the operation lever 11 is slightly heavy and the response of the directional control valve 1 is slightly delayed, but the actuator 3 operates. By the way, the fact that the operation force of the operation lever 11 is slightly heavy and the response of the directional control valve 1 is slightly delayed means that the actuator 3 can be finely operated. Therefore, the mode is a suitable mode when the actuator 3 is finely operated. Specifically, the finishing accuracy does not decrease even if the hydraulic operation is started even when the oil temperature (0 ° C.) is low in the hanging load operation (so-called “sling operation”) or the slope finishing operation using the example machine. Rather, the finishing accuracy at low temperatures (0 to 30 ° C.) is improved. Furthermore, this mode is suitable for a male operator who does not have a great deal of difficulty in operating the operation lever 11. Conversely, if “tos = 20 ° C.”, the fine operability is slightly reduced as compared with “tos = 30 ° C.”
Since the operation force of the operation lever 11 and the response delay of the directional control valve 1 are substantially improved, the mode is suitable for a female operator who has recently become generalized and has no power. The above-mentioned “tos = 10 ° C.” and the stepless “0 ° C. <tos <20 °” produce the moderate operation and effect in the above description, and thus the repeated description will be omitted. In short, there is a remarkable effect that the degree of freedom is generated in the operation effect.

Other examples will be listed.

(1) Although a plurality of actuators 3 are used in the first embodiment, one actuator 3 may be used depending on the hydraulic circuit. In this case, the pressure compensating valve 7 and the shuttle valve 6 are naturally unnecessary. In this case, it is unnecessary to explain that the "maximum load pressure PLs" is replaced with the "load pressure PL" (the same applies to claims 2 to 8 of the present application).

(2) The pilot pressure switching valve 10 is a PPC
It is not necessary to limit the operation amount (operation stroke or operation inclination angle) of the operation lever 11 to a plurality of steps, such as the valves 10L and 10R, which generate a pilot hydraulic pressure having a pressure proportional to the operation amount of the operation lever 11. And the degree of pressure reduction may be switched for each stage. That is, the pilot pressure switching valve 10 only needs to generate a pilot oil pressure of a pressure corresponding to the operation amount of the operation lever 11.

(3) It is desirable to form the communication paths 1fL and 1fR, which constitute the additional mechanism 1f of the directional control valve 1, as follows (31) to (33). (31) The communication passages 1fL, 1fR in FIG. 3 are grooves provided on the surface of the spool 1b. As shown in detail in FIG.
It is desirable that the side tip be sharpened. (32) FIG. 4 shows only the left side of the spool 1b (the same applies to the right side). However, as shown in FIG. 4, even if the groove depth is made shallower toward the tip without sharpening the tip of the communication path 1fL. Good. (33) FIG. 5 also shows only the left side of the spool 1b (the same applies to the right side). However, as shown in FIG. 5, a communication passage 1fL is provided in the spool 1b, and the opening of the drain chamber 1e side is pointed toward the tip. It may be molded. In this case, the wall of the drain chamber 1e enlarges or reduces the opening of the communication passage 1fL on the drain chamber 1e side as the spool 1b slides. The bolts at both ends of the spool 1b shown in FIG. 3 are blind plugs for processing holes for storing a check ball in the inner hole of the spool 1b described in detail in FIG. The groove-type communication passages 1fL and 1fR and the hole-type communication passage 1fL described in FIG.
1fR is provided avoiding the above-mentioned bolt or penetrating through the inside of the bolt. Each of the communication passages 1fL, 1
According to fR, when the spool 1b slides from the neutral position to one side, the communication path 1fL (or 1f
R) and the communication area of the other side communication passage 1fR (or 1fL) gradually decreases. That is, although the operation and effect of the communication passages 1fL and 1fR in the first embodiment are as described above, in the cold state as they are, both pilots based on the difference in length and bend between the pilot lines 13L and 13R are used. There is a concern that a large difference may occur in the viscous resistance of the oil in the pipes 13L and 13R. However, in each of the communication passages 1fL and 1fR formed by the improvement, the pilot lines 13L and 13R are used.
Even if the spool 1b at the neutral position slightly moves in the direction of the operation position due to the difference in the viscous resistance between the two, the direction switching valve 1 switches to the operation position if the spool 1b moves greatly.
Actuator 3 will malfunction during warm air),
A communication area difference occurs between the two communication passages 1fL and 1fR, and the communication area difference cancels the difference in viscous resistance, and returns the spool 1b to the direction for maintaining the neutral position. That is, when the circuit is warmed up, there is no erroneous operation in which the direction switching valve 1 is slightly switched to one of the left and right operation positions and the actuator 3 is slightly moved, so that early warming can be efficiently performed.

(4) The variable unload pressure mechanism 5b may be omitted. In this case, the unload pressure P2 is a fixed value of 3MP.
a, the effect of increasing the temperature is only slightly slower than in the first embodiment having the unload pressure variable mechanism 5b. Therefore, it is suitable for specifications in regions that are not so cold.

(5) The unload pressure variable mechanism 5b is a solenoid that can change the second spring force of the second spring 5a (that is, the unload pressure P2). This solenoid is, as shown in FIG. A variable throttle 5c provided on the outlet side of the unload valve 5 may be used. That is, the controller 14 sends a signal Sa (in this case, not the unload pressure change signal Sa but the “aperture area change signal Sa”) to the variable throttle 5c. The throttle loss at the variable throttle 5c is a source of oil temperature rise.

(6) The variable unload pressure mechanism 5b
According to the operation program of the embodiment, the oil temperature tos set on the engine speed setting dial 18b is made equal to “to ≦ tos (=
10 ° C) ”and“ to> tos (= 10 ° C) ”.
Stopped at However, as shown by the dotted line in FIG. 1, an unload pressure setting dial 5c is separately provided, and the operator can send an unload pressure change signal from the unload pressure setting dial 5c to the controller 14 as necessary, regardless of the set oil temperature tos. The magnitude and output timing of Sa or the throttle amount change signal Sa may be designated and input, thereby increasing the degree of freedom in changing the unload pressure P2. However, in this case, in the warm-up structure of the hydraulic circuit, as described above, “to>to> to
In the case of "s", the pump displacement is controlled by the LS valve 2b (or in the case of "to>tos", the pump displacement is controlled by the LS valve 2b). Pressure change signal Sa due to
Alternatively, the output timing of the throttle amount change signal Sa from the controller 14 is set to be equal to or lower than the set oil temperature tos if the temperature is specified by the unload pressure setting dial 5c, for example. Otherwise, the "pump displacement variable control" by the LS valve 2b at the time of "to>tos" cannot be performed.)

(7) The second directional control valve 17 may be omitted as shown in FIG. That is, when the operation lever 11 is neutral,
Although the pump 2 is in the minimum discharge amount state, the pump discharge oil still drains completely from the unload valve 5 to the tank 9.
Therefore, the temperature of the oil in the tank 9 is raised. In this case, it is desirable that the controller 14 outputs an unload pressure change signal Sa such as "P2> 10 MPa".
By doing so, the temperature raising effect is enhanced. Note that “P2 ≧ 3
The unload pressure change signal Sa such as "0 MPa" is unnecessary. The reason is that the unload pressure change signal Sa is set to "P2
When the pressure is set to> 30 MPa, the pump discharge oil drains not from the unload valve 5 but from the relief valve 4 to the tank 9. Thus, in the configuration in which the second directional control valve 17 is omitted, the unload valve 5 looks as if it is unnecessary. However, if the unloading valve 5 is not provided, the pump discharge oil will be relieved from the relief valve 4 to the tank 9 when the operation lever 11 is neutral during the hydraulic operation. Therefore, the original machine (hydraulic power shovel)
In a hydraulic circuit of a machine equipped with an all-speed governor type engine such as a bulldozer or a wheel loader, oil overheating occurs. Therefore, in the hydraulic circuit of such a machine, the unload valve 5 is indispensable.

(8) The second pressure reducing valve 12 may be a relief valve dedicated to pilot hydraulic pressure. In this case, although not shown, a small hydraulic pump dedicated to a general pilot hydraulic pressure is provided separately from the pump 2. In this case, the pilot oil pressure becomes the specified pressure of the relief valve dedicated to the pilot oil pressure.

(9) The second pressure reducing valve 12 may be of a sequence type. This is not shown because it is well known, but if the simplest configuration is shown as an example, a second relief valve having a relief pressure of, for example, 4 MPa is provided in the pump discharge path, and the relief oil is supplied to each directional control valve 1. And a pressure reducing valve of, for example, 3.3 MPa is provided in a discharge path of the pump 2 between the second relief valve and the pump 2 so that a secondary pressure (= 3.3 MPa) is supplied to the left and right PPC valves 10L,
Pilot oil pressure to 10R. In this case, the relief valve 4 and the unload valve 5 do not have the same arrangement as in FIG.
It is arranged downstream of the second relief valve. Assuming that the second pressure reducing valve is a sequence type, the secondary pressure of the second pressure reducing valve 12 is set to the set pressure P2 of the unload valve 5 as in the first embodiment.
It is not necessary to set the second pressure reducing valve below, and the degree of freedom in setting the secondary pressure of the second pressure reducing valve is increased.

(10) Although the basic circuit in FIG. 1 is a variable displacement hydraulic pump, it may be a fixed displacement pump. The basic circuit in this case has a configuration in which the servo cylinder 2a, the LS valve 2b, the second direction switching valve 17, and the signal line from the controller 14 to the second direction switching valve 17 are removed from the basic circuit of FIG. In the basic circuit in this case, the “state in which the pump pressure introduction signal S2 is input to the second directional control valve 17” described in the operation program of the first embodiment means “the state in which the pump 2 has a fixed capacity”. It is easy to understand from doing. In other words, the basic circuit in this case can be described by borrowing FIG. 1 as follows: “A hydraulic actuator in which the discharge oil of the fixed displacement hydraulic pump 2 is intermittently turned on or off by switching the directional control valve 1 so as to be stopped or operable. And a second spring 5a at one end, and a second spring 5a at one end.
Of the second spring force P2 and the maximum load pressure PLs of the actuator 3
And the other end side receives an unload valve 5 for receiving the discharge pressure Pp of the pump 2.
A load sensing type hydraulic circuit which is a closed center type switching valve that drains the maximum load pressure PLs to the valve 2b and the unload valve 5 to the tank 9 through the drain chamber 1e.
In other words, the basic circuit of FIG. 1 is also a load sensing hydraulic circuit, but the basic circuit in this case is a completely different form of “fixed displacement hydraulic pump type load sensing hydraulic circuit”. The functional characteristic of the basic circuit in this case is that, when the directional control valve 1 switches from the center neutral position to the left and right operation positions, regardless of the size of the opening area A, the differential pressure across the directional control valve 1 ΔP becomes constant, whereby the amount of oil passing through the directional control valve 1 is proportional to the opening area A ”(note that it is not necessary to explain that the front-rear differential pressure ΔP is the unload pressure P2). That is, in the basic circuit in this case, of the pump discharge oil, the oil that does not flow into the actuator 3 drains from the unload valve 5 to the tank 9. Therefore, the oil temperature rises during this drain. In the basic circuit in this case,
Since the temperature rises even when the operation lever 11 is in the neutral state during normal work,
When the operating lever 11 is in neutral, the engine speed can be reduced to low idle by the accelerator pedal to prevent the occurrence of oil overheating. For example, an all-speed governor type such as a crane truck (however, an accelerator pedal type),
Alternatively, it is also suitable as a warm-up structure of a hydraulic circuit of a machine equipped with a minimum / maximum speed governor type engine which is an accelerator pedal type.

(11) The unload valve 5 is removed from the "load sensing type hydraulic circuit of fixed displacement hydraulic pump type", the directional control valve 1 is an open center type (not shown), and the directional control valve Tank 9 in neutral position
A variable relief valve may be additionally provided in the drain line to the drain (the variable relief valve is provided separately from the relief valve 4). That is, a variable relief valve is added to a normal hydraulic circuit. The variable relief valve receives an operation signal from the controller 14 when the circuit is warmed up, and increases the set relief pressure from 0 Pa to, for example, 4 MPa. The temperature of the drain oil rises due to this pressure increase. That is,
The pilot lines 13L, 13R and the other oil heaters can be warmed up, so that the other two-sided warming action and effects described above can be obtained.

[Brief description of the drawings]

FIG. 1 is an example of a hydraulic circuit operated by a hydraulic pilot including a first embodiment.

FIG. 2 is a partial sectional view of the directional control valve of FIG. 1;

FIG. 3 is a schematic view of the communication passage of FIG. 2;

FIG. 4 is a schematic view of one form of a second example of the communication path.

FIG. 5 is a schematic view of another form of the second example of the communication path.

FIG. 6 is a circuit diagram showing an example of a form of addition to an unload valve.

FIG. 7 is a partial circuit diagram in which the second directional control valve is omitted from FIG. 1;

[Explanation of symbols]

1: Directional switching valve, 1a: Valve body, 1b: Spool, 1
cL, 1cR: Pilot pressure receiving chamber, 1dL, 1dR: Neutral spring,
1e: drain chamber, 1fL, 1fR: communication passage, 2: hydraulic pump, 2b: LS valve, 2b1: first spring, 3: hydraulic actuator, 5: unload valve, 5a: second spring, 8: engine, 9 : Tank, 10: Pilot oil pressure regulator, 11:
Operating lever, 13L, 13R: Pilot line, 14: Controller, 16: On-off valve, 17: Second directional control valve, P
1: first spring force, P2: second spring force, PLs: maximum load pressure, Pp: pump discharge pressure.

Claims (8)

[Claims] A spool (1b) is slidably fitted in a valve body (1a) and a drain chamber (1e) for a tank (9) is provided in the valve body (1a). Pilot pressure receiving chambers (1cL, 1cR) are provided at both ends of the spool (1b), and both pilot pressure receiving chambers (1cL, 1cR) are provided with neutral springs (1dR, 1dL) that constantly bias the spool (1b) in the neutral direction. Both pilot pressure receiving chamber
(1cL, 1cR) to the pilot line (13L, 13R), and the pilot pressure to one pilot pressure receiving chamber (1cL or 1cR) via one (13L or 13R) of both pilot lines (13L, 13R). , The spool (1b) slides in the valve body (1a) from the neutral position to the other side, and the oil discharged from the hydraulic pump (2) is supplied to the hydraulic actuator (3) from the opening opened by the sliding, and the hydraulic pressure is applied to the hydraulic actuator (3). Directional switching valve for actuating the actuator (3)
(1), the operating lever (11), and the two pilot lines (13L, 13R) communicate with the tank (9) when the operating lever (11) is in the neutral position, while the operating side pilot tube is operated when the operating lever (11) is operated. Road (13L
Or 13R) to a pilot oil pressure of a pressure corresponding to the operation amount of the operation lever (11), and a pilot oil pressure regulating valve (1) for communicating the non-operation side pilot line (13R or 13L) to the tank (9).
0), the hydraulic oil can freely flow into both pilot pipelines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR) when the operating lever (11) is neutralized. An on-off valve (16) is provided, and when the operating lever (11) is in neutral, the on-off valve (16) allows the pressurized oil to flow into both pilot lines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR). In the warm-up structure of the hydraulic pilot-operated hydraulic circuit that enables warm-up of the pilot lines (13L, 13R), the directional control valve (1) has the valve body when the spool (1b) is in the neutral position.
At both ends of the spool (1b), communication paths (1fL, 1fR) for communicating the drain chamber (1e) of (1a) and the pilot pressure receiving chambers (1cL, 1cR) are provided, and both communication paths (1fL, 1fR) are provided. When the spool (1b) slides from the neutral position to one side, the communication area of the communication path (1fL or 1fR) on one side gradually increases according to the sliding amount, and the communication of the communication path (1fR or 1fL) on the other side. A warm-up structure for a hydraulic pilot-operated hydraulic circuit, characterized in that the area is formed so that the area gradually decreases. A spool (1b) is slidably fitted in the valve body (1a), and pilot pressure receiving chambers (1cL, 1cR) are provided at both ends of the spool (1b) of the valve body (1a). Pressure receiving chamber (1
cL, 1cR) are provided with neutral springs (1dL, 1dR) that constantly bias the spool (1b) in the neutral direction, and both pilot pressure receiving chambers (1c
L, 1cR) to the pilot line (13L, 13R), and apply pilot oil pressure to one pilot pressure receiving chamber (1cL or 1cR) through one of the pilot lines (13L, 13R) (13L or 13R). This causes the spool (1b) to slide in the valve body (1a) from the neutral position to the other, and the oil discharged from the variable displacement hydraulic pump (2) from the opening opened by this sliding to the hydraulic actuator.
The directional control valve (1) that is supplied to (3) to operate the hydraulic actuator (3), the operating lever (11), and the two pilot lines (13L, 13R) when the operating lever (11) is in the neutral state, is connected to the tank (9). On the other hand, when the operating lever (11) is operated, a pilot oil pressure of a pressure corresponding to the operation amount of the operating lever (11) is given to the operating pilot line (13L or 13R), and the non-operating pilot line is
(13R or 13L) and a pilot oil pressure regulating valve (10) for communicating with the tank (9) .The hydraulic circuit is a hydraulic circuit operated by a pilot and further includes a first spring (2b1) at one end and a first spring (2b1) at one end. The first spring force (P1) of one spring (2b1) and the maximum load pressure (PLs) of the hydraulic actuator (3) are received, and the discharge pressure (Pp) of the variable displacement hydraulic pump (2) is applied to the other end. Receiving "Pp = P
LS valve (2b) for increasing or decreasing the discharge amount of the variable displacement hydraulic pump (2) so as to be "Ls + P1"; and a second spring (5a) at one end, and a second spring (5a) at one end. The unload valve (5) receives the second spring force (P2) and the maximum load pressure (PLs) of the hydraulic actuator (3), and receives the discharge pressure (Pp) of the variable displacement hydraulic pump (2) at the other end. The directional control valve (1) drains the maximum load pressure (PLs) to the LS valve (2b) and the unload valve (5) to the tank (9) at the neutral position in the valve body (1a). When the operating lever (11) is in neutral, both pilot lines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR) are provided for a closed center type hydraulic pilot operated hydraulic circuit having a drain chamber (1e). Valve (16) that allows pressure oil to flow freely
When the operating lever (11) is neutral, the on-off valve (16) allows the pressure oil to flow into both pilot pipelines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR), and both pilot pipelines (13
(L, 13R) in the warm-up structure of the hydraulic pilot-operated hydraulic circuit that enables warm-up of the directional control valve (1) when the spool (1b) is in the neutral position.
At both ends of the spool (1b), communication paths (1fL, 1fR) for communicating the drain chamber (1e) of (1a) and the pilot pressure receiving chambers (1cL, 1cR) are provided, and both communication paths (1fL, 1fR) are provided. When the spool (1b) slides from the neutral position to one side, the communication area of the communication path (1fL or 1fR) on one side gradually increases according to the sliding amount, and the communication of the communication path (1fR or 1fL) on the other side. A warm-up structure for a hydraulic pilot-operated hydraulic circuit, characterized in that the area is formed so that the area gradually decreases. A spool (1b) is slidably fitted in the valve body (1a), and pilot pressure receiving chambers (1cL, 1cR) are provided at both ends of the spool (1b) of the valve body (1a). Pressure receiving chamber (1
cL, 1cR) are provided with neutral springs (1dL, 1dR) that constantly bias the spool (1b) in the neutral direction, and both pilot pressure receiving chambers (1c
L, 1cR) to the pilot line (13L, 13R), and apply pilot oil pressure to one pilot pressure receiving chamber (1cL or 1cR) through one of the pilot lines (13L, 13R) (13L or 13R). This causes the spool (1b) to slide in the valve body (1a) from the neutral position to the other, and the oil discharged from the variable displacement hydraulic pump (2) from the opening opened by this sliding to the hydraulic actuator.
The directional control valve (1) that is supplied to (3) to operate the hydraulic actuator (3), the operating lever (11), and the two pilot lines (13L, 13R) when the operating lever (11) is in the neutral state, is connected to the tank (9). On the other hand, when the operating lever (11) is operated, a pilot oil pressure of a pressure corresponding to the operation amount of the operating lever (11) is given to the operating pilot line (13L or 13R), and the non-operating pilot line is
(13R or 13L) and a pilot oil pressure regulating valve (10) for communicating with the tank (9) .The hydraulic circuit is a hydraulic circuit operated by a pilot and further includes a first spring (2b1) at one end and a first spring (2b1) at one end. The first spring force (P1) of one spring (2b1) and the maximum load pressure (PLs) of the hydraulic actuator (3) are received, and the discharge pressure (Pp) of the variable displacement hydraulic pump (2) is applied to the other end. Receiving "Pp = P
LS valve (2b) for increasing or decreasing the discharge amount of the variable displacement hydraulic pump (2) so as to be "Ls + P1"; and a second spring (5a) at one end, and a second spring (5a) at one end. The unload valve (5) receives the second spring force (P2) and the maximum load pressure (PLs) of the hydraulic actuator (3), and receives the discharge pressure (Pp) of the variable displacement hydraulic pump (2) at the other end. The directional control valve (1) drains the maximum load pressure (PLs) to the LS valve (2b) and the unload valve (5) to the tank (9) at the neutral position in the valve body (1a). When the operating lever (11) is in neutral, both pilot lines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR) are provided for a closed center type hydraulic pilot operated hydraulic circuit having a drain chamber (1e). Valve (16) that allows pressure oil to flow freely
When the operating lever (11) is neutral, the on-off valve (16) allows the pressure oil to flow into both pilot pipelines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR), and both pilot pipelines (13
(L, 13R) in the warm-up structure of the hydraulic pilot operated hydraulic circuit that enables warm-up of the LS valve (2R) in the pipeline that guides the maximum load pressure (PLs) to the LS valve (2b).
The maximum load pressure introduction position that leads the maximum load pressure (PLs) to b), and the pump discharge pressure (Pp) to the LS valve (2b) instead of the maximum load pressure (PLs)
A second directional control valve (17) having a switchable pump pressure introduction position for guiding hydraulic pressure. 4. The warm-up structure of a hydraulic pilot-operated hydraulic circuit according to claim 2, wherein the maximum load pressure (P) is applied to the LS valve (2b).
Ls), the maximum load pressure introduction position that leads the maximum load pressure (PLs) to the LS valve (2b), and the maximum load pressure (PLs) instead of L.
A warm-up structure for a hydraulic pilot-operated hydraulic circuit, comprising a second directional control valve (17) having a switchable pump pressure introducing position for guiding a pump discharge pressure (Pp) to an S valve (2b). 5. A spool (1b) is slidably fitted in the valve body (1a), and pilot pressure receiving chambers (1cL, 1cR) are provided at both ends of the spool (1b) of the valve body (1a). Pressure receiving chamber (1
cL, 1cR) are provided with neutral springs (1dL, 1dR) that constantly bias the spool (1b) in the neutral direction, and both pilot pressure receiving chambers (1c
L, 1cR) to the pilot line (13L, 13R), and apply pilot oil pressure to one pilot pressure receiving chamber (1cL or 1cR) through one of the pilot lines (13L, 13R) (13L or 13R). This causes the spool (1b) to slide in the valve body (1a) from the neutral position to the other, and the oil discharged from the variable displacement hydraulic pump (2) from the opening opened by this sliding to the hydraulic actuator.
The directional control valve (1) that is supplied to (3) to operate the hydraulic actuator (3), the operating lever (11), and the two pilot lines (13L, 13R) when the operating lever (11) is in the neutral state, is connected to the tank (9). On the other hand, when the operating lever (11) is operated, a pilot oil pressure of a pressure corresponding to the operation amount of the operating lever (11) is given to the operating pilot line (13L or 13R), and the non-operating pilot line is
(13R or 13L) and a pilot oil pressure regulating valve (10) for communicating with the tank (9) .The hydraulic circuit is a hydraulic circuit operated by a pilot and further includes a first spring (2b1) at one end and a first spring (2b1) at one end. The first spring force (P1) of one spring (2b1) and the maximum load pressure (PLs) of the hydraulic actuator (3) are received, and the discharge pressure (Pp) of the variable displacement hydraulic pump (2) is applied to the other end. Receiving "Pp = P
LS valve (2b) for increasing or decreasing the discharge amount of the variable displacement hydraulic pump (2) so as to be "Ls + P1"; and a second spring (5a) at one end, and a second spring (5a) at one end. The unload valve (5) receives the second spring force (P2) and the maximum load pressure (PLs) of the hydraulic actuator (3), and receives the discharge pressure (Pp) of the variable displacement hydraulic pump (2) at the other end. The directional control valve (1) drains the maximum load pressure (PLs) to the LS valve (2b) and the unload valve (5) to the tank (9) at the neutral position in the valve body (1a). When the operating lever (11) is in neutral, both pilot lines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR) are provided for a closed center type hydraulic pilot operated hydraulic circuit having a drain chamber (1e). Valve (16) that allows pressure oil to flow freely
When the operating lever (11) is neutral, the on-off valve (16) allows the pressure oil to flow into both pilot pipelines (13L, 13R) and / or both pilot pressure receiving chambers (1cL, 1cR), and both pilot pipelines (13
(L, 13R) In the warm-up structure of the hydraulic pilot-operated hydraulic circuit capable of warming up the unload valve (5), the second spring force (P2) of the second spring (5a) can be changed. A warm-up structure for a hydraulic pilot-operated hydraulic circuit, characterized in that: 6. A warm-up structure for a hydraulic pilot-operated hydraulic circuit according to claim 3, wherein the unload valve is provided.
Is a warm-up structure for a hydraulic pilot-operated hydraulic circuit, wherein the second spring force (P2) of the second spring (5a) is changeable. 7. The warm-up structure of a hydraulic pilot-operated hydraulic circuit according to claim 6, wherein at the start of warm-up when the operating lever (11) is neutral, the on-off valve (16) controls both pilot lines (13L, 1L).
3R) and / or pressurized oil flows into both pilot pressure receiving chambers (1cL, 1cR), and the second directional control valve (17) is set at the pump pressure introduction position, and / or the second spring of the unload valve (5). (5a)
The second spring force (P2) of the pilot lines (13L, 13R) and / or
Alternatively, the flow of the hydraulic oil into both pilot pressure receiving chambers (1cL, 1cR) is stopped, the second directional control valve (17) is returned to the maximum load pressure introduction position, and / or the second spring of the unload valve (5) (5a)
A controller (14) for restoring the second spring force (P2) to the original state. 8. A variable displacement hydraulic pump according to claim 7, wherein said hydraulic pilot operating hydraulic circuit has a warm-up structure.
Is driven by the engine (8), and the controller (14) has an operation program to start and end the warming of the engine (8) in synchronization with the start and end of the warming of the hydraulic pilot operated hydraulic circuit. Features warm-up structure of hydraulic pilot operated hydraulic circuit.