JPH0528392Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention is a simultaneous control type variable system that is driven by a prime mover such as an internal combustion engine and discharges two systems of pressure fluid, and the discharge amount is simultaneously and variably controlled. This invention relates to a horsepower control device for a capacity double piston pump.

(Prior Art) The applicant previously proposed two cylinder blocks c and c each having a plurality of pistons b that can be retracted and retracted from a single rotating shaft a, as shown in FIG. Install the blocks so that the heads d of the pistons b face each other, and connect the cylinder blocks c and c to the front and rear surfaces e and f between both cylinder blocks c and c.
A tiltable swash plate g is provided on which the head d of each piston b comes into contact, and control pistons h, h are provided on the front surface e and rear surface f of the swash plate g to control the tilting of the swash plate g. We proposed a variable displacement double piston pump in which the two pistons are brought into contact with each other.

Further, as a means for controlling the pump horsepower, as shown in the second diagram, a swingable arm k to which a rotational moment is applied by a control spring j is provided on a support shaft i,
A pilot piston m, which is retractably provided on a control piston that reciprocates along the arm k, is slidably brought into contact with the arm k so as to resist the rotational moment, and furthermore, the pilot piston m is slidably brought into contact with the arm k so as to resist the rotational moment. It has also been proposed to connect a pilot valve o for applying or removing the discharge pressure of the variable displacement pump n to the control piston.

(Problems to be Solved by the Invention) The double piston pump shown in the first drawing can change the stroke of the piston b that reciprocates in two cylinder blocks at the same time by tilting one swash plate g. The means for tilting the plate g is 1.
It is advantageous in that it is sufficient to assemble it, and the means for horsepower control shown in the second figure is based on a mechanical structure by just using the pilot valve o, so it has the advantage that it can be manufactured easily and at low cost. Since the illustrated double pump tilts the swash plate g using two control pistons h, h, it is impossible to apply the horsepower control means shown in the second figure as is.

The object of the present invention is to make the aforementioned type of horsepower control means applicable to the aforementioned simultaneous control type double piston pump, and to perform horsepower control of the double piston pump with a simple configuration.

(Means for Solving the Problems) In the present invention, two cylinder blocks each having a piston that can be retracted and retracted are mounted on one rotating shaft so that the heads of the pistons of each cylinder block face each other, A tiltable swash plate is provided between the two cylinder blocks, and the head of the piston of each cylinder block comes into contact with both front and rear surfaces, and control pistons are provided on the front and rear surfaces of the swash plate to control the tilting of the swash plate. A pilot valve spool is connected to the side of the control piston, and an arm is provided which can swing freely about a support shaft under the action of the elastic force of a control spring, and one side of the control piston The higher discharge pressure from both cylinder blocks is applied to the cylinder block, and the higher discharge pressure is applied to the other cylinder block through the spool of the pilot valve, and the swash plate is provided with: A stepped pilot piston is provided which can freely move in and out in a direction perpendicular to the tilting direction and whose tip abuts the arm so as to resist the rotational moment caused by the control spring, and each stepped portion of the pilot piston is configured to adjust the discharge pressure of each cylinder block. The above object is achieved by acting through oil passages formed in each control piston and swash plate.

(Function) When the one rotating shaft is rotated by the prime mover,
The two cylinder blocks also rotate simultaneously, and the pistons of each cylinder block are reciprocated by the inclined swash plate. Two systems of fluid are discharged from each cylinder block by this reciprocating motion, and the pump operates as a double piston pump. The swash plate is tilted to an appropriate inclination angle according to the discharge pressure to control the horsepower of the pump by control pistons acting on both the front and rear sides of the swash plate.

To further explain this control, the discharge pressure of each system discharged from each cylinder block acts on each step of the pilot piston provided on the swash plate through the oil passage of each control piston, and the pilot piston is connected to the arm. It exerts a force that resists the rotational moment given by the control spring. When the rotational moment generated in the arm by the pilot piston is larger than the rotational moment due to the control spring, the arm swings against the control spring, and the spool of the pilot valve provided in contact with the arm moves to the open position. move to,
The higher discharge pressure from both cylinder blocks is directed to one control piston which tilts the swashplate to reduce its inclination. Due to this tilting of the swash plate, the pilot piston moves to change its point of action closer to the arm's support axis, and the rotational moment caused by the pilot piston gradually decreases, and the arm begins to swing in the opposite direction, combining with the rotational moment caused by the control spring. When the swinging of the arm returns to the balanced position, the pilot valve spool returns to the closed position, and the introduction of discharge pressure to the one control piston stops, so the tilting of the swash plate also stops, and the discharge matches the pump discharge pressure. A constant control of the pump horsepower is performed by discharging the amount.

When the rotational moment generated in the arm by the pilot piston is smaller than the rotational moment due to the control spring, the arm swings while pushing the pilot piston back into the swash plate due to the force of the control spring. The spool of the pilot valve connects the chamber of the one control piston to the tank and allows the one control piston to move backward, so that the swash plate is arranged so that the angle of inclination is increased by the force of the other control piston. tilts. Due to this tilting movement, the point of action of the pilot piston moves to a point away from the support shaft of the arm, and the rotational moment from the pilot piston gradually increases, causing the arm to swing in the opposite direction until it reaches a position where it balances the rotational moment from the control spring. When the swinging of the arm returns, the pilot valve spool returns to the closed position.
As a result, the connection of the other control piston chamber to the tank is cut off, the tilting of the swash plate is also stopped, and the pump horsepower is controlled to be constant by discharging a discharge amount commensurate with the pump discharge pressure.

(Embodiment) An embodiment of the present invention will be explained with reference to FIGS. 3 to 6. In FIG.
1 shows a cylinder block equipped with a plurality of pistons 5 which can be retracted and retracted, and each cylinder block 3, 4 is fixedly attached to the rotating shaft 1 so that the heads 6 of the respective pistons 5 face each other. Reference numeral 7 denotes a swash plate provided between both cylinder blocks 3 and 4 so as to be freely tiltable on a shaft 8, and the head 6 of the piston 5 of each cylinder block 3 and 4 moves a slide sho 9 to both the front and rear surfaces of the swash plate 7. contact through. Furthermore, control pistons 10 and 11 for controlling the tilting of the swash plate 7 are provided on the front and rear surfaces of the extension portion 7a of the swash plate 7.
Abutted through.

The details of both control pistons 10, 11 are as shown in FIG. 14
The chamber 14 is provided with a spring 14a that pushes the small diameter control piston 11.

In FIG. 4, 15 indicates both control pistons 10,
An arm is provided on the side of 11 to be swingable around a support shaft 16, 17 is a pilot valve with a spool 18 connected to one side 15a of the arm 15, and 19 is connected to the arm 15 via the spool 18. A control spring 20 is a stepped pilot piston provided on the swash plate 7 so as to be able to move in and out in a direction orthogonal to the tilting direction of the swash plate 7. The tip of the pilot piston 20 is slidable. It comes into contact with one side 15b of the arm 15 along the control pistons 10, 11 via the shoe 21.

The details of the pilot piston 20 are as shown in FIG. 5, and include a first stage pressure receiving surface 20a and a second stage pressure receiving surface 20b. As such, the control piston 1
circular chambers 21, 22 formed in the casing 1 around the pistons 10, 11, oil passages 24, 2 formed in each control piston 10, 11, piston shoe 12 and swash plate 7;
5, the discharge pressure of each cylinder block 3, 4, that is, the discharge pressure of two systems of double pumps A and B, is introduced, and the pilot piston 20 applies a rotational moment to the arm 15 in the opposite direction to the rotational moment caused by the control spring 19. give.

The higher pressure of the discharge pressures of the cylinder blocks 3 and 4 extracted by the shuttle valve 26 is introduced into the chamber 14 of the small diameter control piston 11, and the higher pressure is introduced into the chamber 14 of the large diameter control piston 10. One pressure is controlled by the pilot valve 17 and introduced.
Depending on the position of the spool 18 in conjunction with the arm 15, the pilot valve 17 can either introduce the pressure extracted by the shuttle valve 26 into the chamber 13 as described above, or connect the chamber 13 to the tank 27, or Control is performed to close the chamber 13.

The above configuration can be represented by a symbol as shown in FIG. 7, and its operation is as follows.

When the rotating shaft 1 is driven by a prime mover (not shown), each cylinder block 3, 4 rotates, each piston 5 is reciprocated by a swash plate 7, and two systems of pressure fluid are discharged. In this case, when the pressure of the pressurized fluid to be discharged is high, the inclination angle of the swash plate 7 is made small to reduce the discharge amount, and when the pressure is low, the inclination angle is increased to increase the discharge amount, thereby increasing the horsepower of the double pump. Constant control is preferable in order to improve operational efficiency.

In the present invention, a stepped pilot piston 20 is provided on the swash plate 7, and a control piston 1 is provided at each step.
Since the two systems of discharge pressure can be applied through the oil passages 24 and 25 formed in the cylinder blocks 3 and 11, the increase in the discharge pressure of one or both of the cylinder blocks 3 and 4 is generated in the pilot piston 20. If the force becomes greater than expected, the pilot piston 20 can swing the arm 15 in the direction opposite to the arrow, against the rotational moment exerted by the control spring 19, and the pilot valve 17 can be shut off from the closed position shown. It is moved to a position where the pressure extracted by the valve 26 is introduced into the chamber 13 of the control piston 10 of large diameter. As a result, the control piston 10 tilts the swash plate 7 against the other control piston 11 so as to reduce its inclination angle, and the tilting of the swash plate 7 causes the point of action of the pilot piston 20 on the arm 15 to become the same. Since the arm 15 moves toward the support shaft 16, the rotational moment of the arm 15 received from the pilot piston 20 gradually decreases, and the arm 15 swings back in the direction of the arrow. When the rotational moment by the control spring 19 is balanced, the pilot valve 17 returns to the closed position and stops introducing pressure into the chamber 13 of the large diameter control piston 10, so the tilting of the swash plate 7 stops and each cylinder Each piston 5 of blocks 3, 4 delivers a small amount of fluid with a small stroke.

Also, the discharge pressure of one or both of the cylinder blocks 3, 4 becomes low, and the pilot piston 20
If the force generated in is smaller than expected, the arm 15 swings in the direction of the arrow by the control spring 19,
The pilot valve 17 moves from the illustrated closed position to a position connecting the chamber 13 of the large-diameter control piston 10 to the tank 27, making the pressure in the chamber 13 the tank pressure, so that the spring 14a acting on the small-diameter piston 11
and the pressure acting on the chamber 14 via the shuttle valve 26, the swash plate 7 is tilted to increase its angle of inclination. As a result, the point of action of the pilot piston 20 on the arm 15 moves away from the support shaft 16, and the rotational moment generated on the arm 15 by the pilot piston 20 gradually increases, causing the arm 15 to swing in the opposite direction of the arrow. do. When the rotational moment due to the control spring 19 balances the rotational moment due to the pilot piston 20, the pilot valve 17 returns to the closed position and the movement of the control pistons 10, 11 is stopped.
Each piston 5 of the cylinder blocks 3, 4 discharges a large amount with a large stroke.

In the above operation, the relational expression of the forces acting on the arm 15 is as follows: The force generated on the pilot piston 20 is Fp, the force of the control spring 19 is Fs, and the force generated on the pilot piston 20 and the control spring 19 is expressed by Fs. Let Lp and Ls be the distances to each point of application, Fp×Lp=Ls×Fs.

Since Fp is proportional to the discharge pressure from each cylinder block 3 and 4, that is, the pump discharge pressure, and Lp is proportional to the inclination angle of the swash plate 7, that is, the displacement volume of each cylinder block, the arm 15 is balanced and stopped at a predetermined position. By keeping it constant, the pump horsepower can be controlled at a constant level.

8 and 9 show each control piston 10, 1
1 to the pilot piston 20 via the swash plate 7, the oil passages 24 and 25 introduce the discharge pressure of each cylinder block 3 and 4, that is, each pump, to the pilot piston 20. Swash plate 7
The piston shoe 12 supported by the spherical head 28 planted in the piston is brought into contact with the piston shoe 12, and oil is supplied to each stage of the pilot piston 20 from inside each control piston 10, 11 via the piston shoe 12, the spherical head 28, and the swash plate 7. 24 and 25 are formed.

Further, as shown in FIG. 10, it is also possible to add a shift piston 29 so as to apply a force to the arm 15 that is opposite to the force of the control spring 19. According to this, the chamber of the shift piston 29 30
In addition, by introducing pressure from a third pump (not shown), horsepower control including the third pump can be performed.

In this case, the horsepower setting can be changed by introducing external signal pressure instead of the third pump pressure.

Furthermore, if the configuration is such that external signal pressure is introduced into the chamber 13 of the control piston 10 having a large diameter, the slidable stopper 31 provided in the chamber 13 is pushed, and the swash plate is forcibly moved through the control piston 10. By reducing the angle of inclination 7, the maximum discharge amount can be set in two stages.

(Effects of the invention) As described above, according to the invention, two cylinder blocks are provided on one rotating shaft with an intermediate swash plate interposed therebetween, and the swash plate is tilted by the control pistons in front and rear of the cylinder block. In the double piston pump, the swash plate is provided with a stepped pilot piston that abuts the side arms, and each cylinder block is connected to each step via the control piston and an oil passage formed in the swash plate. Since the discharge pressure is applied, a horsepower control means having an arm to which rotational moment is applied by a control spring can be connected to the double piston pump, and the horsepower of the pump can be easily controlled. There are other effects.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional double piston pump, Figure 2 is an explanatory diagram of a conventional horsepower control means, and Figure 3 is a cross-sectional view of a conventional double piston pump.
4 is an enlarged sectional view taken along the line - in FIG. 3, FIG. 5 is an enlarged sectional view of the pilot piston portion in FIG. 4, and FIG. 4 is an enlarged sectional view of the swash plate portion, FIG. 7 is a line diagram of an embodiment of the present invention, FIG. 8 is a sectional view of another embodiment of the present invention, and FIG. 9 is an enlarged sectional view of the main part of FIG. Enlarged cross-sectional view,
FIG. 10 is a sectional view of still another embodiment of the present invention. 1... Rotating shaft, 3, 4... Cylinder block,
5... Piston, 6... Head, 7... Swash plate, 1
0,11...Control piston, 15...Arm, 1
6... Support shaft, 17... Pilot valve, 18... Spool, 19... Control spring, 20... Pilot piston, 24, 25... Oil passage.

Claims (1)

[Scope of utility model registration request] Two cylinder blocks with retractable pistons are mounted on one rotating shaft so that the piston heads of each cylinder block face each other, and each cylinder block is installed between the two cylinder blocks on both the front and rear sides. A tiltable swash plate is provided on which the head of the piston contacts, a control piston for controlling the tilting of the swash plate is placed in contact with the front and rear surfaces of the swash plate, and a pilot is placed on the side of the control piston. An arm is provided which is connected to the valve spool and is swingable about a support shaft under the action of the elastic force of a control spring, and one of the control pistons receives the higher discharge pressure from both cylinder blocks. and the higher discharge pressure is applied to the other side through the spool of the pilot valve, wherein the swash plate has a tip that can be retracted or retracted in a direction orthogonal to the direction of tilting of the swash plate. A stepped pilot piston is provided in contact with the arm so as to resist the rotational moment caused by the control spring, and an oil passage formed in each control piston and swash plate is provided in each stepped portion of the pilot piston to supply the discharge pressure of each cylinder block. A simultaneous control type variable displacement double piston pump characterized in that the pump is actuated through a double piston pump.