JPS5838390A - Variable displacement type hydraulic pump - Google Patents

Abstract

PURPOSE:To enable to render the entire structure of the above-titled apparatus compact and light, by designing the same such that two-pressure, two-capacity control can be achieved by a single hydraulic pump through provision of a changeover valve which is capable of changing the control pressure acted to a control plunger. CONSTITUTION:Through provision of two spools 22, 23 connected at one end thereof respectively to pressure lines 28, 29, passages 34, 35 opened with movement of these spools 22, 23 are communicated with a back chamber b of a control plunger 21, and a rear chamber K of a pilot plunger 24 is communicated with one pressure line 29. Further, arrangement is such that the pressure lines 28, 29 connected respectively to one end of the spools 22, 23 are communicated selectively with a discharge line 36 via a changeover valve 37. With such an arrangement, two-pressure, two-capacity control can be achieved by a single hydraulic pump by changing the control pressure acted to the control plunger 21 by means of the changeover valve 37. Therefore, it is enabled to render the entire structure of the apparatus compact and light and to lower the manufacturing cost since any other control valves are not required.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable displacement hydraulic pump, and an object thereof is to provide a hydraulic pump that can selectively perform two-pressure and two-capacity control with one hydraulic pump.

Conventionally, when controlling two pressures and two volumes using one variable displacement hydraulic pump, the low pressure side pressure PM and high pressure side pressure negative are determined based on the characteristics shown by curves MA and B shown in Fig. 4. However, not only is it extremely difficult to set the high-pressure side pressure P, but also when the high-pressure side pressure pm changes, the discharge 1iQ1 corresponding to the pressure also changes. There was a drawback that the accuracy varied and stable control could not be performed.

On the other hand, according to this conventional system, the relief pressure (maximum discharge pressure) pA and pB are high, and the required circumferential force within the range of low pressure side pressure P and high pressure side pressure pm is large, resulting in power loss and It also has the disadvantage of generating a large amount of heat.

That is, since the two-pressure control using the method explained above is performed based on the characteristics shown in curve M, B, in other words, the characteristics close to constant horsepower characteristics, the discharge amount q1 at the high pressure side pressure pm
is not stable, and the above-mentioned drawbacks occur. Conventionally, however, a method has been proposed in which this control characteristic is changed to the characteristic shown by curve 0 using two hydraulic pumps to eliminate the above-mentioned drawbacks. Not only must a pump be used, but also one unloading valve for setting the low-pressure side pressure P1 and a relief valve for setting the high-pressure side pressure P1 are required, which is extremely disadvantageous economically and expensive. At the same time, there is a disadvantage that the entire device becomes large and cannot be used in places with limited space.Secondly, in this method, the high pressure side pressure P3 is set using a relief valve, so power loss and heat generation are reduced as described above. This method has a drawback that is even more noticeable than that of the previous method.

However, in view of the above-mentioned problems, the inventor of the present invention has developed a two-pressure control system that can change the actuator between fast feed (light load) and slow feed (heavy load) using only one hydraulic pump. We have proposed a hydraulic pump that allows for easy setting of heavy pressure and small capacity, as well as accurate and stable settings.

Some hydraulic pumps were ugly because they could not arbitrarily adjust the pressure at low pressure and large capacity.

This invention was invented to solve the above-mentioned problems in the previously proposed hydraulic pump.The purpose of this invention is to use one hydraulic pump to produce two pressures and two volumes, that is, two different pressures and two different discharge volumes. The discharge amount can be controlled with sharp cut characteristics while being selectively adjustable.

The configuration of the present invention includes an operation plunger and a pilot plunger that adjust the amount of displacement of the variable control element toward the neutral position, and two spools that control the movement of each plunger toward the variable control element. At the same time, one end of each of these spools is connected to a pressure line communicating with the discharge line of the pump so that the spools are moved by the discharge pressure, and a pressing body is provided at the other end to counteract the movement of these spools. respectively, and each has a passage that opens when the spool moves,
Each of these passages communicates with a rear chamber of the operating plunger, and the rear chamber of the virofft plunger communicates with one of the pressure lines, and one of the pressure lines is selectively connected to the discharge line. A communicating switching valve is provided, and by switching the switching valve, two-pressure, two-capacity control can be selectively performed.Hereinafter, an embodiment of the pump of the present invention will be described in detail with reference to FIG.

The hydraulic pump shown in FIG. 1 is a swash plate type axial plunger pump, and in this 11fi, (1) is a hollow housing body, and a cover (2) is fixed to the lower side of the housing body. A main shaft (5) is rotatably supported inside the housing main body (1) via bearings (3) and (4). The cylinder block (7) is connected to the cylinder block (7) through the
) are both rotatably supported.

This block (7) v- is provided with a large number of pistons (8) that can freely reciprocate with a predetermined stroke, and a shoe (8) supported by a retainer (9) is attached to the tip of each piston (8). 10) are attached respectively, and the shoes (
This swash plate (11), which is in contact with the swash plate (11) constituting the =T variable 19ill element through the 10), can swing freely within a certain range of inclination angle using the trunnion shaft (12) as a fulcrum. 4. A spring (13) constituting a biasing means is interposed between the back surface of the side where the swash plate (10) contacts and the inner surface of the housing body (1), so that the swash plate ( 11) is operated to maximize the inclination angle. Therefore, in this state, when the main shaft (5) is driven to rotate the cylinder block (7), each piston (8) reciprocates, and this reciprocating movement provides the maximum discharge amount.
Further, by adjusting the inclination angle of the swash plate (11), an arbitrary discharge amount can be obtained.

In addition, in Fig. 1 (145 is the valve plate, (15)
is a spring, and (1,!S) is a receiver for the spring (15).

However, the pump shown in Figure IJ1 has a swash plate (to be explained next) in the pump housing body (1) constructed as described above.
An operating plunger (21) and a pilot plunger (24) are installed to adjust the inclination angle of the operating plunger (21) and a pilot plunger (24) to vary the discharge amount, and two spools (
22).

(23) was established.

The plunger (21) is movably inserted into the cylinder chamber (&) provided in the housing body (1), and one end thereof contacts the swash plate (11) as described above, and the other end is in contact with the swash plate (11). A back chamber is formed between the inner wall of the cylinder chamber (&), and the pilot plunger (24
) is freely movable inside the pilot plunger (24), and the tip of the pilot plunger (24) is opposed to the back surface of the plunger (21).

This pilot plunger (24) sets the discharge amount during high pressure control, and consists of a large diameter ff1s (24&) and a small diameter part (24b), and the large diameter 1 (24&) connects the back chamber to the front chamber ( It is divided into a rear chamber (b) and a rear chamber (k).

Further, the lit chamber (kl) of the rear chamber in the cylinder chamber (&) is provided with a stepped portion (e) that engages with the large diameter portion (241L) of the viroft plunger (24),
This stage 1s(e) causes the pilot plunger (2
4) is restricted from moving in the direction of the swash plate.

Further, the spools (22) and (23) are connected to the valve block (25).
), the spool holes (26), (27) are movably installed inside the spool holes (26), (27).
) is a pressure line (28) leading to a discharge line (66);
(29), and the pressure lines (28), (2
9) due to the discharge pressure acting through the spool (22);
This is done by moving (23). On the back side of each of these spools (22) and (23), there is a pressing body (such as a coil spring) that resists the movement.
30) and (31) are provided, and these pressing bodies (
, 150) and (31), the spool hole (26)
, (27) until the discharge pressure exceeds a certain pressure.
23).

Further, the pressing body (60) in the embodiment shown in the drawings-
The pressing force of the spools (22) and (2!1) by (61) is different, and the pressing force of the pressing body (6!
0) sets the pressure during low pressure control (Peng1), and the pressure body (31) corresponding to the spool (26) sets the pressure during high pressure control (pat). 50) and (31) are provided with pressure adjustment screws (32) and (33) that adjust the pressing force and set the discharge pressure at which the spools (22) and (23) move to a predetermined value. .

Further, passages (34) and (35) are provided which open when the spools (22) and C25) are moved, and the high pressure control spool (26) is inserted through the passage (34) of the low pressure control spool (22). The secondary side (2) of the spool hole (27)
7a), and communicates the passageway (35) with the front chamber (b) of the back chamber, and the back side of the biloft plunger (24), that is, the rear chamber (k) of the back chamber.
is connected to the pressure line (29) via the passage (42), and one of these pressure lines (28), (29) is connected to the discharge line (66). A switching valve (67) is provided which selectively communicates with the pressure line (28) through the switching valve (67).
, (29) is selectively connected to the discharge line (56).

This switching valve (37,) is switched in conjunction with the operation of an actuator, and is switched by an electric signal using a limit switch, for example, but this switching control signal is not limited to an electric signal, but may also be a pneumatic signal, Pump pressure may also be used.

Also, in Figure 111, (68) and (39) are tanks (T)
The tank line (38) is a tank line that opens to the secondary side (26&) of the spool holes (26) and (27),
(27 &) and the tank line (39) are connected to the storage chambers (30 m) and (311) of the suppressors (30) and (31). The operation when controlling the capacity will be explained.

In the state shown in FIG. 1, the pilot plunger (24) and the operating plunger (21) are both located at the left end, and in this state, the swash plate (11) is at its maximum inclination angle.
The pump discharge amount is maximum.

First, the operation with the switching valve (37) positioned as shown in FIG. 1 will be explained. In this case, when the main shaft (5) is rotated, the piston (8) provided in the cylinder block (7)
reciprocates to discharge fluid at maximum flow rate, and a portion of the fluid flows only from the discharge line (66) to the pressure line (28) and is introduced into the spool hole (26). This pushes the spool (22) to the right.

Note that the 1r11 pressurization line (29) is the rear chamber (k) on the back side of the switching valve and the pilot plunger (24).
is open to the tank (T) via the passage (42) and the pressure line (29), and is connected to the spool (2).
3) remains stationary. Furthermore, since the spool (22) is pressed to the left by the pressing body (30), the spool (22) does not move until the discharge pressure reaches a predetermined pressure that overcomes this pressing force. If the discharge pressure exceeds the pressing force of the pressing body (60) by one, the spool (22) is pushed to the right, the passage (64) opens, and the discharge fluid flows through the passage (34) and the passage (65). to move the front chamber (b) of the rear chamber GC-entering operation plunger (21) toward the swash plate, and this movement causes the swash plate (11) to move toward the swash plate.
The inclination angle of the can be adjusted to the neutral position.

That is, the switching valve (37) is the 15th! By positioning it at the left-hand position of Q, it is possible to control the so-called low pressure large capacity (PmQ) in which the discharge lid is brought to zero at a low pressure (Pa) as shown by the OL curve shown by the solid line in FIG.

Next, we will explain the operation when the switching valve (67) is switched to the right position in Fig. 1. In this case, the pressure line (28) is connected to the tank ( 〒）
It is open to the pressure line (29) or the discharge line (36).

Therefore, from the discharge line (36) to the pressure line (29)
) The discharge fluid flowing into the back chamber (
k), and the pressure of this fluid, that is, the discharge pressure acts on the pilot plunger (24) to
＜Immediately, the drainer (24) moves to the right side, moves the operating plunger (21), reduces the inclination angle of the swash plate (11), and adjusts the discharge amount to the intermediate position as shown by the dashed line in Fig. 2. The discharge amount QmK is controlled.

This state is maintained until the discharge pressure reaches the high pressure (Yo) set by the suppressor (61), and until the discharge pressure reaches the high pressure (P01), the presser (61) 31) press force 10 wins, said spool (2
6) remains stationary.

Then, when the discharge pressure increases from this state to the above-mentioned high pressure (Pam), the spool (23) begins to move to the right against the pressing body (61), and the passage (35) opens. , fluid is introduced into the front chamber (b) of the back chamber, the operating plunger (21) is moved to the right, the swash plate (11) is adjusted to the neutral position 1 (m), and the discharge amount is controlled to zero. .

In this way, when the switching valve (37) is switched to the right position in Figure 1, the discharge amount is reduced to zero at a high pressure (P at) as shown by the 01 curve shown by the one-dot chain line in Figure 2. It is possible to control the so-called high voltage QIQI (PIQI).

The openings of the passages (34) and (!15) form an orifice between them and the spool holes C26> and (27), and the pressure is reduced by this orifice and the control pressure is applied to the front of the back chamber. It acts on chamber (b). However, this reduced pressure is a pressure sufficient to counteract the 15 rotational moment of the swash plate and the spring (13).

Therefore, if the orifice opening area increases significantly, the depressurization also increases, but this is because the angle of the swash plate (11) decreases to immediately cancel out the increase, and this action is instantaneous. It will be done.

In other words, it functions as a servo mechanism.

That is, the rotational moment of the swash plate (11) is designed to take a substantially constant value regardless of the position of the swash plate angle.
As described above, the reduced pressure acting on the front chamber (b) of the rear chamber is determined by the sum of this rotational moment and the spring (13). Therefore, as the swash plate angle decreases, the reduced pressure increases by the compressive force of the spring (13).

Thus, by repeating the above action, the angle of inclination of the swash plate (11) becomes smaller, and finally, due to the operation of the spool (22) or (23), the angle of inclination becomes close to zero, and the discharge pressure (Pas) or ( The discharge amount becomes zero at To, and the control of the discharge amount is performed by control pressure.
It can be done based on gender.

As described above (according to the hydraulic pump shown in Figure 9J1), the second
The discharge pressure-flow rate characteristics shown in Figures 1 and C curves were obtained.
can be selectively controlled by switching the switching valve (67), and the low pressure and high pressure pm in these operations can be arbitrarily set.

In the embodiment described above, the pressing force of the pressing body (31) is made larger than the pressing force of the pressing body (30) to control low-pressure large capacity and high-pressure small capacity. The pressing forces of (30) and (31) may be made the same to provide two-pressure, two-capacity control of high pressure (or low pressure) large volume and high pressure (or low pressure) small volume, or the pressing force (61) The pressing force of the pump may be made smaller than the pressing force of the suppressor (30) to perform two-pressure, two-capacity control of Shimada large capacity and low pressure small capacity.The embodiment described above is a swash plate type axial plunger pump, The same applies to other variable displacement vane pumps.

That is, in this case the cam ring is the variable control element and the plunger (21) is brought into contact with this cam ring.

As described above, the present invention provides an operating plunger and a pilot plunger, as well as two spools whose one end is connected to a pressure line, and a passage opened by movement of these spools communicates with the back chamber of the operating plunger,
Also, the rear chamber of the virofft plunger is communicated with one of the pressure lines, and the pressure line connected to one end of the spool is selectively communicated with the discharge line via a switching valve. By switching the switching valve, it is possible to selectively control two pressures and two volumes,
Moreover, since the control of these two pressures and two volumes is performed by the control pressure acting on the operating plunger, it can be performed based on the sharp cut characteristic. Since pressure and volume control can be performed, the entire system can be made smaller and lighter, and has excellent economical advantages. Furthermore, since no extra control valve is required, it can be provided at low cost.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings show an embodiment of the hydraulic pump of the present invention, in which Fig. 1 is a longitudinal sectional view thereof, Fig. 2 is a characteristic diagram of two-capacity control, and Fig. 3 is an operation plunger. FIG. 4 is a partially enlarged sectional view of an embodiment in which stroke adjustment is performed between the pilot plunger and the pilot plunger, and FIG. 4 is a characteristic diagram of conventional two-pressure and two-capacity control. (11) - Swash plate (13) - One spring (21) - One operation plunger (22), (25) - Spool (24) -
Pilot spool (28), (29) --- Pressure line (30), (31) --- Pressing body (34), (35) --- Passage (37) --- Switching valve c b > --- Front Chamber (k)... Rear chamber Figure 2, Figure 3, same db 10 2/ Figure 4 -1--1 Pressure

Claims (1)

[Claims] A hydraulic pump whose discharge amount is variable by adjusting the amount of displacement of the variable control element is provided with bias means for pressing the variable control element to a maximum displacement position, and also toward a neutral position of the variable control element. An operating plunger and a pilot plunger are provided to adjust the variable position of each plunger, and the variable control #1j! of each plunger is provided. Two spools are provided to control the movement toward the bare side, and a pressure line communicating with the discharge line of the pump is connected to one end of each of these spools, so that the spools are moved by the discharge pressure, and the other end Each of the spools is provided with a suppressor that opposes the movement of the spool, and a passage that opens when the spool moves is provided, and each of these passages is communicated with the rear chamber of the operating plunger, and the rear chamber of the pilot plunger is connected to the rear chamber of the pilot plunger. , communicated with one of the pressure lines,
A variable displacement liquid field pump characterized in that the rice field line is provided with a switching valve that selectively communicates one of the pressure lines with the discharge in.