JPS58206893A - Variable displacement type hydraulic apparatus - Google Patents

Abstract

PURPOSE:To enable to prevent heating of a pump and deterioration of fluid, by providing a changeover valve in the piping system of a pump, and imparting a feathering function by the control of the changeover valve. CONSTITUTION:An FC valve 40 is operated independently of the opening of an orifice 29 that is changed by the movement of a spool 23. A control passage 47 is communicated with a discharge passage 17 via a connecting passage 44, and a part of fluid passed through the discharge passage 17 is introduced into a back-pressure chamber 14a of a plunger 14, whereby a swash plate 6 is moved to its neutral position by the control pressure. Thus, it is enabled to obtain a feathering function to compensate the pressure with a low pressure and hence to prevent heating of a pump and deterioration of the fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a variable displacement hydraulic device, more specifically, a pressure-type variable throttle valve whose throttle base is variable in response to discharge pressure, interposed in the discharge passage of a variable displacement pump. At the same time, a flow compensator valve is provided, and a feedback line communicating with the secondary side of the throttle valve is connected to the flow compensator valve.

- The variable displacement pump is equipped with a variable control element and an operation plunger for operating the element, and the movement of the plunger is controlled via a pressure compensator valve (hereinafter abbreviated as PC valve). The variable control element is controlled to control the condition of the pump under the set pressure set by the PO valve.

By the way, the capacity control of the pump is a so-called pressure-on pensator control using a PO valve, and a long lamp (
Since simple constant horsepower control and constant horsepower control cannot be performed,
In order to perform pressure compensator control of the pump as well as flow rate control such as long ramp control and constant horsepower control, a variable throttle valve is interposed in the discharge passage of the pump, and the PO valve and flow compensator are connected to the primary side of the throttle valve. He developed and proposed a variable displacement hydraulic device that was equipped with a valve (hereinafter referred to as the ya valve). (Special application 1986-1
77752) Specifically, as shown in Figure 4, a variable displacement pump (A
) is equipped with a pressure-type variable throttle valve (20) that makes the throttle filtration variable in response to the discharge pressure, and a position control valve (20) is installed on the secondary side of the throttle valve (20). 60) and between this throttle valve (20) and the pump (mu), one end is connected to the discharge passage (17) and the other end is connected to the secondary side of the throttle valve (20). A communicating IO valve (40) is provided, and between the pump (mu) and the NO valve (40),
A po valve (50) whose one end communicates with the discharge passage (1)
), while the PO valve (50) and the YO valve (
40) through a control passage M (47), and this passage (47) communicates with the back chamber (14a) 1ζ of the operation plunger (14) in the pump (M).

Therefore, the pressure of the fluid discharged from the pump (mu 5) is smaller than the pressure set by the PO valve (50), and the pressure difference before and after the throttle valve (20) is smaller than the set pressure of the yO valve (40). In this case, without operating the F' (J valve (40) and the PO valve (50), that is, the pump (
A) discharging fluid at maximum flow from the pump without actuating the operating plunger (14);
Furthermore, if the load pressure of the fluid increases and the opening degree of the throttle valve (20) is reduced, the differential pressure across the throttle valve (20) will rise above the set pressure of the f+'0 valve (40). To operate the yo valve (40), the plunger (
14) Rear chamber (14 & ) /\Fluid is introduced, and its control pressure operates the sylanger (14) to adjust the fluid discharge ridge from the pump (A) for constant horsepower control, etc. I decided to become a senior sergeant.

By the way, the above-mentioned hydraulic device is used, for example, in a construction machine such as a hydraulic excavator, and controls its actuator (80), but when controlling the actuator (80), a closed center type direction is used. Switching valve (60)
During the working process, the switching valve (60) is switched to the closed section, and the actuator (8
According to the hydraulic device, the operation of the switching valve (Li) may be stopped.
60) to the closed section, the pump (
The discharge pressure of the pump is IIIks4 pressure, and at this maximum pressure P
Therefore, although there is no need to compensate for pressure at the highest pressure, Ma
Pressure compensation is performed using r pressure, which consumes extra power, and pressure compensation is performed at the highest pressure, which generates excess heat and raises oil temperature, leading to oil deterioration and leakage problems. Also, there is a problem of wear due to the dust present in the oil.

The present invention was invented in view of the above-mentioned problems, and a switching valve is interposed in the piping system of the pump, and a feathering function is provided by switching control of the switching valve to prevent heat generation or fluid deterioration. This is done in an energy-saving manner.Moreover, a variable displacement violet pump is equipped with a discharge passage, and a pressure-type variable throttle valve is installed in which the throttle bolt is variable in response to the discharge pressure. In addition, in a variable displacement I-type hydraulic device, a flow compensator pulp is provided, and a feedback line communicating with the secondary side of the throttle valve is connected to the valve. It is characterized by interposing a switching valve that selectively switches between the secondary side and the tank, and by switching the feed south packing line to the tank side by the switching valve, the throttle amount of the throttle valve can be adjusted. Regardless, the FO valve is operated and the variable control element is held at the neutral position so that so-called feathering can be performed.

The variable displacement hydraulic device of the present invention will be described below with reference to the embodiments shown in the drawings.
) will be explained.

. Figure 1 shows a swash plate type axial piston pump (mu) as a variable displacement hydraulic device, in which one drive shaft (4) is connected to the housing (1) via one bearing (2), (?)). A pair of cylinder blocks (
5), (5) are connected by spline, and each cylinder block (5), (5) has a swash plate (6),
C6) is shown.

The device of the present invention can be used with any other type of pump other than the two-barrel pump shown in FIG.
Can be used as an oil phase for all variable displacement hydraulic machines including pumps.

The hydraulic charger shown in FIG. 1 is a dual pump, but since the structure is the same, the pump 1 on the left side will be explained for the sake of explanation.

Therefore, the cylinder block (5) in one pump (mu) shown in FIG. The shoe (9) is supported by a retina (8)1ζ
) are respectively attached, and these shoes (9) are in contact with the swash plate (6). The swash plate (6) is supported to freely swing within a certain angle of inclination via the tranny A shaft (10), and a connecting rod (11) is connected with a pin at a position displaced by 180°. (12
) are connected to a bias plunger (16) for pressing the swash plate (6) in the direction of the maximum inclination angle and an operating plunger (14) for adjusting the inclination angle of the swash plate (6). ing.

The bias plunger (16) is an operating plunger (
The housing (14) has a smaller diameter than the housing (14).
) is freely supported by a cylinder body (15) fixed to the end cap (1a) of K, the back chamber (13) of the plunger (16)
a) communicates with the high-pressure side pressure passage of the pump (mu), that is, the discharge passage (17) to be described later;
) so that the discharge pressure acts on it.

Further, the operating plunger (14) is supported so as to be freely movable by a fixed cylinder body (18) + c of an R-marked entcuff (1a'3j), and a control passage (47) described later is supported in the rear chamber (14m). ) is set so that the control pressure acts on the back of the operating plunger (14).

Therefore, the control passage (
When the control pressure from the operating plunger (14) is not applied, the swash plate (6) reaches its maximum inclination angle and the maximum discharge amount is obtained.
When a control pressure is applied to the swash plate (6), the inclination angle of the swash plate (6) is adjusted, and a discharge device commensurate with the inclination angle can be obtained.

In addition, as shown in detail in FIG. 2, the pump (M) is equipped with a pressure-type variable throttle valve (20) in the discharge passage (17) of the pump (M), which has a variable throttle valve in response to the discharge pressure. At the same time, a discharge pressure is applied to one end, and a suppressing force of a pressing body (45) made of a coil spring and a load pressure on the secondary side of the throttle valve (20) are applied to the other end. an IFQ valve (IFQ valve) comprising: a spool (43) that is moved toward the pressing body (45); and the control passage (47) that opens when the spool (43) moves in the direction of the pressing body (45) and communicates with the discharge passage (17). 40), and the aAIh...,'? t
r ridge (A 711--6Th!-One piece Blangise (1A
) is connected to the rear chamber (14 &) of the engine, allowing long ramp control or constant horsepower control.

Further, the throttle valve (20) located in the discharge passage (17)
) A cylinder (80) is connected to the secondary side of the center-closed directional control valve (60) to a load-side passage (30), which will be described later, on the secondary side of the center-closed directional control valve (60), and a control valve The pressure fluid sent through (60) causes the cylinder (8
The above-mentioned pump (40) is intended to perform constant horsepower control with flow compensator control, as shown in Figs. 2 and 6, and the 70-valve (40) and a PO valve (50) are used in combination.

The variable throttle valve (20) used in the pump shown in wi2 and FIG.
1), a spool chamber (22) is provided, and the spool chamber (22) is provided in the spool chamber (22).
22), a pair of first and second lands (
A spool (26) having springs 25 &) and (26b) is freely movable inside, and a large diameter coil spring (24) and a small diameter coil spring (25 ) is provided via an adjusting screw body (26), and a piston (27) is provided outside the second land (23b), while the valve body (21) j
This is an annular chamber (28) that opens into the spool chamber (22).
is provided, and the discharge passage (17) is provided in this annular chamber (28).
) to connect this annular chamber (28) and the second land (
An orifice (29) is formed between the orifice (23b) and the directional control valve (6
0) is connected to the load-side passageway (30) that constantly communicates with the spool chamber (22) and the feedback line (61) of the ten valves (40), and also connects the feedback line (61) of the piston (27). The back chamber (27&) includes the discharge passage (
17) is connected to the high pressure passage (32).

In addition, the pII IfO valve (40) sets the differential pressure between the discharge pressure and the load pressure constant by the pressing body (45),
It detects the differential pressure between the discharge pressure and the load pressure, and as shown in Fig. 2, the valve body (42') has a spool chamber (42').
1), the spool (43) is placed in the spool chamber (42) of
) is freely movable inside each ζ, and the spool (43
) is connected to the discharge passageway (17) at one end side thereof.
44) to apply discharge pressure, and the pressing body (45) is provided on the other end side of the spool (46), and the control body (44) is connected to the housing chamber (46) of the suppressing body (45). The feedback line (61) connected to the downstream side of the valve (60) and the secondary side of the throttle valve (20) is connected to the valve body (41) of the 1FO valve (40), and the spool chamber ( 42) and communicates with the communication path (44) which communicates with the discharge path (17) from the movement of the spool (46) toward the suppressor (45).
47), and in FIG. 2, it is installed in parallel with the PO valve (50).

The PO valve (50) sets the maximum pressure, and has a spool chamber (51) in parallel with the spool chamber (42) and the valve body (41) that constitutes the PO valve (40). A spool (52) is freely movably housed in the spool chamber (51), and one end side of the spool chamber (51) is opened to the communication path (44) to allow the spool (52) to move freely inside the spool chamber (51).
52), and a pressing body (56) consisting of a coil spring on the other end and setting the maximum pressure.
) storage chamber (54) is provided in a communicating manner, and this storage chamber (54)
4), the pressing body (56) is provided so as to face the discharge pressure, and the storage chamber (54) is communicated with the tank.

Therefore, in the hydraulic device as described above, the present invention provides a feedback line (31) of the 70 valves (40) that connects the feedback line (61) to the secondary side of the throttle valve (20) and the tank (T, l). A switching valve that selectively switches between
70) was inserted.

Specifically, as shown in FIG.
By switching the throttle valve (70) to the negative side of the throttle valve (20), the throttle valve (
20) secondary side and Mil record? 0 valve (40), constant horsepower control is performed by this IC valve (40), and by switching the switching valve (70) to the tank (T) side, the feedback line (61) is connected to the tank (T) side. ), and accordingly, the FO valve (40) is operated regardless of the throttle amount of the throttle valve (20), and the downstream side of the throttle valve (20) in the discharge passage (17) is opened. The pump (
The swash plate (6) is adjusted to the neutral position by communicating with the back chamber (14a) of the plunger (14) in the pump (A), and the fluid discharge from the pump (A) is made zero flow.
This is intended to provide a feathering function that compensates for the pressure in A) with a low pressure that overcomes the operation of the bias plunger (16).

The present invention is configured as described above, and the pump (A
), the fluid sucked from the suction passage (19) is discharged to the discharge passage (17), and the fluid flowing through the passage (17) is controlled by the variable throttle valve (20) and the position control valve (60).
is sent to the piston cylinder (80), and the cylinder (80) is actuated.

Therefore, when performing constant horsepower control, the switching valve (70
), the secondary side of the throttle valve (2o) is communicated with the ya valve (40) via the feedback line (61), and the process is performed as follows. First, when the pressure of the fluid flowing through the discharge passage (17) described in iiJ is low and the differential pressure across the throttle valve (20) is smaller than the set pressure of the YO valve (4O), the 10 valves (4U) do not operate, and therefore Pump (mu) swash plate (6)
has the maximum inclination angle and flows out from the throttle valve (20) at the maximum flow rate.

Further, when the pressure of the fluid flowing through the discharge passage (17) increases and the opening degree of the orifice (29) is reduced by movement of the spool (26) of the throttle valve (20), the throttle valve (20)
0) The differential pressure of cocoon weight increases, ? When the pressure rises to the set pressure of the 0 valve (40), the 10 valve (40) is actuated to operate the operating plunger (14) via the control passage (47) to adjust the inclination angle of the swash plate (6). to reduce the discharge flow rate.

Further, when the fluid pressure in the discharge passage (17) becomes higher and exceeds the pressure set by the PO valve (50), the PA valve (50) is activated and the discharge is discharged through the swash plate (6). The flow rate is cut off, and thus flow compensator constant horsepower control with pressure compensator is performed.

By the way, when operating the cylinder (80) using the hydraulic device, the H1I switching valve (60) is switched to the 1 closed section in the middle of the work process, and the operation of the piston (80) is stopped. If so, the switching valve (7
0) to open the feedback line (31) to the tank (T) side.

Then, the back pressure side of the y-a valve (40) is connected via the feedback line (61) and the switching valve (7U),
Since it is opened to the tank (T), the throttle valve (20
), in other words, regardless of the opening degree of the orifice (29) due to the movement of the spool (23). 0 valve (40) operates, and the discharge passage (
17) of the fluid flowing through the discharge passage (17).
is introduced into the rearward chamber (14 &) of the plunger (14), and the control pressure thereof adjusts the diagonal #l, (6) to a neutral position, and a feather ring that compensates for pressure at a low pressure. As explained above (in the hydraulic system of the present invention, a switching valve is interposed in the feedback line of the IFO valve to selectively switch the line between the secondary side of the throttle valve and the tank). Because of this, it was possible to equip the pump with a feather link function, which made it possible to control the flow of the pump in an energy-saving manner, without causing heat generation in the pump or deterioration of the fluid. This made it possible to extend the life of the pump.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway plan view of a hydraulic device according to the present invention, Fig. 2 is a cross-sectional view of its main parts, Fig. 6 is a piping diagram of the same device, and Fig. 4 is a piping diagram showing a conventional example. 0 (mu)...Pump (17)...Discharge passage (20)...Variable throttle valve (+1)...Feedback line (40)...
Flow compensator valve (70)...Switching valve agent Patent attorney Tsu 1) Hisashi Nao

Claims (1)

[Claims] (1) When a pressure-type variable throttle valve (20) whose throttle amount is variable in response to the discharge pressure is installed in the discharge passage (17) of the variable displacement pump (70), a 70-compensator valve (70) is installed. 40) and a variable displacement hydraulic device in which a feedback line (61) communicating with the secondary side of the throttle valve (20) is connected to the valve (40), the feedback line 1l) A variable displacement hydraulic device characterized in that a switching valve (70) is installed to selectively switch a feedback line (31) between the secondary side of the throttle valve (20) and the tank.