JP3419498B2 - Multiple variable piston pump - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a hydraulic power source for a small construction machine, and is capable of obtaining a plurality of independent discharge flow rates from a single cylinder barrel incorporated in a single pump body. Control and lubrication mechanism.

[0002]

2. Description of the Related Art Conventionally, in a compact construction machine having a small installation space, a multiple-type variable piston pump as described above is used and the discharge pressure and the discharge flow rate of the pump are controlled to reduce the size and drive engine. We are trying to use the output effectively. For example, in Japanese Patent Laid-Open No. 1-267367, as shown in FIG. 10, the stroke of the piston 2 that reciprocates in the cylinder barrel 1 tilts the swash plate 4 that constitutes the sliding contact surface of the shoe 3 provided on the piston head. The discharge flow rate is made variable by changing the flow rate. This swash plate 4 is tilted by the control piston 5,
Pressure oil is introduced into the control piston 5 from two independent discharge port lines 6 and 7,
The sum of the areas of the two discharge port pressures acts as thrust, and when the discharge pressure increases, this thrust causes the swash plate 4 to move.
Is tilted, the discharge flow rate is reduced, and so-called constant horsepower control is performed to keep the pump shaft input constant.

More specifically, referring to FIGS. 10 to 12, an even number of pistons 2 are axially slidably inserted in a cylinder barrel 1 supported by bearings 10 in a main body 9 so as to be rotatable together with a shaft 8. There is. As shown in FIG. 12, a piston 2 provided on the cylinder barrel 1
The even-numbered piston cylinder chambers 11 that move in and out are alternately arranged on two different concentric circles in two rows.
2a and an inner opening hole 12b, and these opening holes are in sliding contact with the front end surface of the cylinder barrel.
Is open to. The suction side of the valve plate 13 is provided with a wide arc-shaped slot 14 that allows the outer opening hole 12a and the inner opening hole 12b of the cylinder barrel to communicate with each other substantially along the suction stroke. On the discharge side, an outer opening hole 12 is formed along the discharge stroke.
A circular arc-shaped outer groove 15a that can communicate with a and a circular arc-shaped inner groove 15b that can communicate with the inner opening hole 12b are provided.

On the other hand, the swash plate 4 is biased by the tilting spring 16 so as to have the maximum tilting angle, and the control piston 5 provided on the opposite side of the tilting spring gives a reaction force to the minimum tilting angle. It can be tilted up to. When the cylinder barrel 1 is rotated, the piston 2 slides in the axial direction according to the inclination angle of the swash plate 4, and a pump action is performed.

In the suction stroke, the outer opening holes 12a are alternately bored in the cylinder barrel 1 from the arcuate slot 14.
And hydraulic oil is sucked into each cylinder chamber 11 of the cylinder barrel 1 through the inner opening hole 12b and the inner opening hole 12b, and in the discharge stroke, the outer opening hole 12a forms an arc-shaped outer groove 15a and the inner opening hole 12b forms an arc-shaped inner groove 15b. The pressure oil is discharged separately. Arc-shaped outer groove 15a and arc-shaped inner groove 1
5b is connected to two independent discharge ports,
As a result, two independent discharge flow rates can be obtained from one cylinder barrel built in one pump body.

Further, the tilting shaft 17 of the swash plate 4 abuts a bearing 18 provided on the main body 9 so as to tilt.
The bearing 18 is provided with a pressure oil reservoir 19 for bearing lubrication. The swash plate 4 is provided with a small hole 20 that is open on the discharge stroke side of the sliding contact surface of the swash plate 4 of the shoe 3 of the head of the piston 2 provided in the cylinder barrel 1.
It is supposed to communicate with. A part of the pressure oil discharged by the rotation of the cylinder barrel 1 is supplied to the pressure oil pool 19 through the small hole 20 from the communication hole 21 provided in the shoe 3, and the swash plate tilt shaft 17 and the main body bearing portion 18 are provided. Lubrication is performed between them.

The pump discharge amount is variable by tilting the swash plate 4, and the control piston 5 for controlling the tilt angle of the swash plate 4 is biased in the direction opposite to the swash plate by the control spring 22. Has been done. Control spring 2
2 is appropriately combined with the tilting spring 16 described above. Two rods 23 and 24 are in contact with the control piston 5, and pressure oil is separately guided to the rod rear surfaces 25 and 26 from the above-described two discharge ports. When the pressure in the discharge port increases due to an increase in load (not shown), the two rods 23 and 24 work to push the control piston 5, and the two springs 1
The swash plate 4 is tilted against the spring force of 6, 22 to reduce the discharge flow rate.

The hydraulic pressure applied to the two rod rear surfaces 25 and 26, that is, the pressure of the two discharge ports, is P
1, P2, the discharge flow rate from each discharge port is Q1, Q2
If (Q = Q1≈Q2), then (P1 + P2) × Q
The control piston and the spring are selected so that the constant horsepower characteristic is obtained. With this constant horsepower characteristic, when the resistance is small, that is, when the discharge pressure is low, the maximum discharge amount is obtained and high-speed operation is possible, while when the resistance is large, that is, when the discharge pressure is high, the discharge amount decreases and low-speed operation is possible. Done. In particular, when one of the discharge ports has a low pressure and the other has a high pressure, the hydraulic pressure applied to the control piston is the sum of the two discharge pressures. Since the tilt angle becomes large, the pump discharge amount increases,
High-speed operation is possible, and there is an advantage that drive energy can be more effectively converted into hydraulic energy.

In the multiple variable piston pump as described above, the pressure oils from the two discharge ports must be independently supplied to and controlled by the actuators, so the pressure oils from the discharge ports are directly combined. Can not do it. For this reason, the discharge port pressure must be indirectly transmitted to the control piston or the like, and as described above, two rods that come into contact with one control piston are provided, and pressure oil is separately provided on the back surface of the rods. Was supplied and controlled. Further, also in the lubrication of the tilting shaft of the swash plate, the pressure oil for lubrication is supplied to the pressure oil reservoir from the small hole opened on the discharge stroke side of the swash plate sliding contact surface of the shoe.

[0010]

However, in such a multiple variable piston pump, two rods that contact one control piston are provided, and pressure oil is separately supplied to the back surface of the rods. Therefore, there is a problem that the structure is complicated, and the number of processing steps and the number of parts are large. Further, the lubrication of the bearing portion for tilting the swash plate is intermittent lubrication because pressure oil is supplied every time the piston passes over the small hole of the swash plate, which results in the inability to maintain an effective lubrication state. was there.

According to the present invention, by supplying one pressure oil to the control piston mechanism, the inclination angle of the swash plate is controlled, the structure is simplified, the size is reduced, and the number of processing steps and the number of parts are reduced. Another object of the present invention is to provide a multiple variable piston pump in which vibration and noise are reduced by continuously supplying oil to the tilt shaft lubrication portion of the swash plate.

[0012]

In order to achieve the above object, in the present invention, a multiple type in which a plurality of independent discharge flow rates can be obtained from one cylinder barrel built in one pump body described above. In the variable piston pump, a pressure communication passage is provided so as to be able to communicate with the outer opening hole and the inner opening hole of the cylinder barrel alternately in the discharge stroke region.

The pressure communication passage is opened on the discharge stroke region of the valve plate and on the circumference passing between the arc-shaped outer groove and the arc-shaped inner groove.

This pressure communication passage is communicated with a cylinder chamber for operating a control piston that tilts a swash plate with which a shoe provided on the head of the piston slidably contacts.

Further, the pressure communication passage is communicated with a lubrication portion for lubricating the bearing that abuts the tilting shaft of the swash plate with which the shoe provided on the head of the piston slidably contacts.

Even if two or more opening holes and pressure communication passages which do not interfere with each other due to the rotation of the cylinder barrel are provided and pressure oil is separately supplied to the rear surface of the rod and the bearing lubrication portion, the rod can be supplied from one pressure communication passage. You may make it supply a pressure oil to a back surface and a bearing lubrication part simultaneously.

It is more effective to provide an accumulator section in the pressure communication passage. Further, the opening hole of the seal plate of the pressure communication passage is a small hole, and a throttle is provided between the communication passages depending on conditions such as the position of the small hole, the pressure of the pump or system, the discharge amount, the rotation speed, and the responsiveness.

[0018]

The pressure communication passage is provided so as to be able to communicate with the outer opening hole and the inner opening hole of the cylinder barrel alternately in the discharge stroke region. Therefore, the pressure communication passage is alternately arranged with the two discharge ports by the rotation of the cylinder barrel. Will be in communication. However, since the outer opening hole and the inner opening hole of the cylinder barrel are switched in a short time by the rotation of the cylinder barrel, an intermediate pressure of each discharge port is generated in the pressure communication passage.

More specifically, since the pressure communication passage opens on the circumference passing between the arc-shaped outer groove and the arc-shaped inner groove in the discharge stroke region of the valve plate, as the cylinder barrel rotates, Alternately, the outer and inner openings of the cylinder barrel pass through the openings. At this time, since the piston is in the discharge stroke, the opening hole and the discharge port are momentarily communicated with each other through the outer opening hole or the inner opening hole of the cylinder barrel, and they are switched instantaneously. Intermediate pressure of the pressure of each discharge port is generated. Since the capacity on the pressure communication passage side is smaller than the capacity on the discharge port side, it hardly affects the discharge port side.

This intermediate pressure is transmitted through the pressure communication passage to the cylinder chamber for operating the control piston, for example, the rear surface of the rod which is in contact with the control piston.
This intermediate pressure P ′ is P ′ = (P1 + P2) / 2 when the pressures of the two discharge ports are P1 and P2, respectively. Therefore, the discharge flow rate from each discharge port is Q1, Q2 (Q
= Q1≈Q2), if the rod pressure receiving area is doubled, that is, the same area as the two conventional rods,
Since (P1 + P2) × Q = constant, constant horsepower characteristics can be obtained under the same conditions as those of the conventional control piston and spring.

Further, since the intermediate pressure generated in the pressure communication passage is supplied to the lubrication portion for lubricating the bearing in contact with the tilting shaft of the swash plate, the bearing portion is supplied to the load received from the cylinder barrel and the bearing portion. The intermediate pressure has a substantially proportional relationship.

By providing an accumulator portion in the pressure communication passage, pulsation caused by the difference in pressure between the two discharge ports is smoothed.

If a throttle is appropriately provided between the communication passages,
The size and position of the opening hole of the seal plate of the pressure communication passage,
The deviation and pulsation of the intermediate pressure value due to the conditions such as the pressure of the pump and the system, the discharge amount, the number of revolutions, and the responsiveness are reduced.

Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, the same parts as those of the multiple variable piston pump shown in FIG. 10 described in the prior art are designated by the same reference numerals and the description thereof will be omitted. The cylinder barrel 1 is similar to the conventional one shown in FIG. In FIG. 1, the valve plate 51 with which the cylinder barrel 1 is in sliding contact has an outer opening hole 12a and an inner opening hole 12b of the cylinder barrel at the same time along the suction stroke on the suction side of the valve plate 51, as shown in FIG. A wide arc-shaped groove hole 14 that allows communication is provided, and the outside opening hole 1 is formed on the discharge side of the valve plate 51 along the discharge stroke.
An arc-shaped outer groove 52a that can communicate with 2a and an arc-shaped inner groove 52b that can communicate with the inner opening hole 12b are provided. An opening hole 53 that opens to the top dead center side on the circumference substantially in the middle of the arc-shaped outer groove 52a and the arc-shaped inner groove 52b is provided, and is connected to the pressure communication passage 54.

A single rod 55 is in contact with the control piston 5 for inclining the swash plate 4, and the rod rear surface 56 is in communication with the pressure communication passage 54. When the pressure of the discharge port increases due to an increase in load (not shown), pressure oil is supplied from the above-described opening hole 53 to the rod back surface 56 through the pressure communication passage 54, and the rod 55 pushes the control piston 5 and The swash plate 4 is tilted against the spring force of the individual springs 16 and 22 to reduce the discharge flow rate.

As the cylinder barrel 1 rotates, the outer opening holes 12a and the inner opening holes 12b of the cylinder barrel alternately pass through the opening holes 53, and the pressure communication passage 54 has an intermediate pressure P '= of two discharge port pressures. (P1 + P2) / 2 occurs. This intermediate pressure P ', when the discharge flow rates of the two discharge ports are Q1 and Q2 (Q = Q1≈Q2),
P ′ × 2 × Q = (P1 + P2) × Q = Constant control piston 5 and springs 16, 2
No. 2 is selected so that constant horsepower characteristics can be obtained.

Further, the tilting shaft 17 of the swash plate 4 contacts the bearing 18 provided on the main body 9 and tilts.
The bearing 18 is provided with a pressure oil reservoir 19 for bearing lubrication. A pressure communication passage 54, which communicates with an opening hole 53 formed in the valve plate 51, is connected to the pressure oil reservoir.

In the embodiment, the forced lubrication structure is provided with the oil sump, but a static pressure bearing structure may be used.
It is also possible to supply the intermediate pressure to another lubrication unit or the like.

In the embodiment, the case of constant horsepower control is described, but it goes without saying that the present invention can be applied to other control mechanisms (pressure compensator type, intermediate horsepower type, etc.) obtained by introducing an intermediate pressure to the control piston. . Further, in the embodiment, the intermediate pressure is introduced to the back surface of the rod that abuts the control piston, but the intermediate pressure is applied to the control piston via the one in which the control piston and the rod are integrated or another link mechanism or the like. You may do it.

The operation of this embodiment will be described with reference to FIG.
5 to 5 show the outer opening hole 12a and the inner opening hole 12 of the cylinder barrel that slide on the valve plate 51 of the present invention.
The relationship between b and the opening hole 53 is illustrated. The dotted lines show the outer opening hole 12a and the inner opening hole 12b of the cylinder barrel.
Indicates. In FIG. 3, the outer opening hole 12a communicates with the opening hole 53 while discharging pressure oil to the arc-shaped outer groove 52a, and the pressure of the arc-shaped outer groove is generated in the opening hole. Then, as the cylinder barrel 1 rotates in the direction of the arrow, when the state shown in FIG. 4 is reached, the opening hole 53 is closed, and the pressure oil supplied to the opening hole is retained in the rod back surface and in the pressure oil pocket.

Further, when the cylinder barrel 1 rotates in the direction of the arrow, as shown in FIG. 5, the inner opening hole 12b for discharging pressure oil and the opening hole 53 communicate with each other, and the inner hole 52b is connected to the inner groove 52b. Pressure is generated in the opening hole, and this pressure oil is supplied to the rod back surface and the pressure oil pocket. Thus, as the cylinder barrel 1 rotates, the opening hole 53
Is an arc-shaped outer groove 52a and a arc-shaped inner groove 52b of the valve plate, that is, two communication ports alternately communicate with each other, and
Intermediate pressure of the two discharge ports acts on the control piston 5 and the oil sump 19 of the bearing portion.

The opening hole 53 of the pressure communication passage is provided so as not to directly communicate with the arc-shaped outer groove 52a and the arc-shaped inner groove 52b of the valve plate 51 in the discharge stroke region. It may be provided at a position where it can communicate with the holes 12b alternately without interfering with each other.

FIG. 6 is a side view showing the positions of the opening holes of the valve plate used in the second embodiment of the present invention. Although the opening hole 53 is provided in the top dead center direction in the first embodiment, the relief groove 6 for preventing pulsation on the bottom dead center side of the valve plate 61.
5 shows a case in which the opening hole 64 is provided between No. 5 and the opening hole 63 is provided at an intermediate position of the discharge process of the valve plate. In this way, the opening hole is formed by the arc-shaped outer groove 62a and the arc-shaped inner groove 62b.
It is possible to arbitrarily set it on the circumference passing between
It is possible to obtain a plurality of two or more mutually independent pressure communication passages.

FIG. 7 is a side view showing an opening hole of a valve plate used in the third embodiment of the present invention. In this embodiment, there are two opening holes that alternately communicate with the outer opening hole 12a and the inner opening hole 12b of the cylinder barrel 1, and they are merged in the valve plate 71, the main body or the like to form one pressure communication passage 74. It is what Opening hole 73
It is possible to reduce a shock or the like at the time of switching the pressure oil by providing a relief groove in a or 73b.

Experimental Example FIGS. 8 and 9 show the relationship between the pump discharge pressure-discharge amount-input torque characteristics and the two discharge port pressures and the intermediate pressure generated in the pressure communication passage in the case of the first embodiment. Shown, pump maximum discharge flow rate 41.4 Li
The results are shown for t / min × 2 (at 2300 rpm) and maximum pressure of 21 MPa. As shown in FIG. 8, a performance comparable to that of the conventional constant horsepower characteristic could be obtained.

In FIG. 9, the horizontal axis represents the discharge pressure P1 of the arc-shaped inner groove 12b, and the vertical axis represents the average of the discharge pressure P1 of the arc-shaped inner groove 12b and the discharge pressure P2 of the arc-shaped outer groove 12a, that is, the intermediate pressure P '= (P1 + P2) / 2 is shown. The alternate long and short dash lines A, B and C in FIG. 9 indicate that the discharge pressure P2 is 1 MPa for A and 11 for B.
MPa and C are calculated values of the intermediate pressure P'when the discharge pressure P1 is changed while fixing at 21 MPa. Solid lines A ', B', and C'in FIG. 9 are measured values corresponding to the calculated values A, B, and C, respectively. As is apparent from FIG. 9, the measured values substantially match the calculated values, and the pressure generated in the pressure communication passage opened in the valve plate is the intermediate pressure between the two discharge ports that are alternately switched according to the rotation of the cylinder barrel. Proved to be

[0036]

Since the present invention is constructed as described above, it has the following effects.

One or more intermediate pressures of the two discharge ports can be obtained with a simple structure in which the pressure communication passage is provided so as to be able to communicate with the outer opening hole and the inner opening hole of the cylinder barrel alternately in the discharge stroke region. It became possible to easily and arbitrarily obtain control such as constant horsepower control, lubrication of the tilting shaft of the swash plate, or lubrication of hydrostatic bearings.

By providing a pressure communication passage opening to the valve plate and communicating this one pressure communication passage with one cylinder chamber for operating the control piston, constant horsepower control can be performed, so that the structure is simplified and the number of processing steps is reduced. , The number of parts has been reduced and downsizing has become possible.

Since the intermediate pressure can be continuously supplied to the tilting shaft lubrication portion of the swash plate and the balance of the bearing is improved, vibration and noise are reduced, and smooth operation can be performed at low rotation speed and high pressure. It was

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention.

FIG. 2 is a side view of the valve plate as viewed in the direction of arrows I-I in FIG.

FIG. 3 is an operation explanatory diagram of the present invention.

FIG. 4 is an operation explanatory view of the present invention.

FIG. 5 is an operation explanatory view of the present invention.

FIG. 6 is a side view of a valve plate according to a second embodiment of the present invention.

FIG. 7 is a side view of a valve plate according to a third embodiment of the present invention.

FIG. 8 is an experimental result of the present invention.

FIG. 9 is an experimental result of the present invention.

FIG. 10 is a sectional view of a main part of a conventional multiple variable piston pump.

FIG. 11 is a side view of the valve plate as viewed in the direction of arrow II-II in FIG.

FIG. 12 is a side view of the cylinder barrel as viewed in the direction of arrows along the line III-III in FIGS. 1 and 10.

[Explanation of symbols]

1 cylinder barrel 2 pistons 3 shoes 4 swash plate 5 Control piston 11 Piston cylinder chamber 12a Outside opening hole 12b Inner opening hole 13, 51, 61, 71 Valve plate 14 Arc-shaped slot 15a, 52a, 62a Arc-shaped outer groove 15b, 52b, 62b Arc-shaped inner groove 17 Tilt axis 18 bearings 19 Pressure oil sump 23, 24, 55 rods 25, 26, 56 Rod back 53, 63, 64, 73a, 73b Opening holes 54,74 Pressure communication passage

Claims (6)

(57) [Claims] 1. A swash plate type variable piston pump, wherein the front end of an even number of piston holes in which a piston is axially slidably inserted in a cylinder barrel rotatably supported together with a shaft has two rows. It has outer opening holes and inner opening holes alternately on concentric circles of different diameters, and these opening holes are opened to the valve plate that is in sliding contact with the front end face of the cylinder barrel, and on the suction side of the valve plate. A wide arc-shaped slot is provided that allows the outer and inner openings of the cylinder barrel to communicate with each other almost along the suction stroke.The discharge side of the valve plate communicates with the outer opening along the discharge stroke. A circular arc-shaped outer groove and a circular arc-shaped inner groove that can communicate with the inner opening hole are provided, and multiple independent cylinder barrels built in one pump body In the multiple variable piston pump capable of obtaining the above-mentioned discharge flow rate, there is provided a pressure communication passage capable of alternately communicating with the outer opening hole and the inner opening hole of the cylinder barrel and only one of them in the discharge stroke region. A multiple variable piston pump. 2. The pressure communication passage is provided in a discharge stroke region of the valve plate, and is opened on a circumference passing between the arc-shaped outer groove and the arc-shaped inner groove. The multiple variable piston pump according to claim 1. 3. The pressure communication passage communicates with a cylinder chamber that operates a control piston that tilts a swash plate that is in sliding contact with a shoe provided on the head of the piston. Item 2. The multiple variable piston pump according to item 2. 4. The pressure communication passage is communicated with a lubricating portion for lubricating a bearing that abuts a tilting shaft of a swash plate with which a shoe provided on the head of the piston is in sliding contact. The multiple variable piston pump according to claim 1, 2 or 3. 5. The pressure communication passages are provided at two locations that do not communicate with each other, and one pressure communication passage of a control piston is configured to tilt a swash plate with which a shoe provided on the head of the piston is in sliding contact. The pressure chamber is communicated with the cylinder chamber, and the other pressure communication passage is communicated with a lubrication portion for lubricating a bearing that abuts the tilting shaft of the swash plate with which the shoe provided on the head of the piston slides. The multiple variable piston pump according to claim 1 or 2. 6. The multiple variable piston pump according to claim 1, wherein the pressure communication passage has an accumulator portion.