JPH0744773Y2 - Control device for variable displacement hydraulic pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a control device for a variable displacement hydraulic pump, and in particular, it has a high response when the control deviation is large and a response when the control deviation is small. The present invention relates to a control device for a variable displacement hydraulic pump that has low stability and high stability.

[Prior art]

Many of the control devices for variable displacement hydraulic pumps are configured to change the tilt angle of the swash plate of the variable displacement hydraulic pump via a hydraulic servo mechanism, as disclosed in, for example, Japanese Patent Publication No. 57-27987. ing. Usually, this hydraulic servo mechanism is provided with a servo cylinder mechanism, an oil passage for introducing servo pressure to the servo cylinder mechanism, and an oil passage switching mechanism interposed in the oil passage. A spool mounting hole having a port communicating with the servo chamber and a spool slidably accommodated in the hole are provided, and the port is provided at a neutral position where the spool closes the port by a land provided on the spool and at both sides thereof. It is configured to be switchable between an open oil supply position and an oil discharge position.

[Problems to be solved by the invention]

In the control device for the variable displacement hydraulic pump configured as described above, the discharge pressure of the variable displacement hydraulic pump is often used as the servo pressure. In this case, however, since the discharge pressure is high, the response speed of the servo cylinder mechanism is high. There is a problem that the control becomes unstable due to over-control or hunting when the control amount is small.

Therefore, it is conceivable to reduce the passage area to reduce the responsiveness.In this case, control stability can be obtained, but the responsiveness is low even when the control deviation is large and a quick response is required. There is a problem of becoming.

Therefore, for example, as shown in FIG. 5, both ends 135b of the land 135a of the spool 135 that opens and closes the port connected to the servo chamber of the servo cylinder mechanism are tapered to reduce the land 135a and the spool when the control amount is small. A technique is known in which a throttle passage is formed between the mounting hole 131 and the peripheral surface to throttle the flow of servo pressure supplied to the servo cylinder mechanism or the servo pressure discharged from the servo cylinder mechanism to slow the control speed. There is.

However, with a taper spool, it is difficult to machine the taper surface of the gentle slope with high accuracy, and it is difficult to obtain the desired performance. When an excessive load is suddenly applied to the hydraulic actuator that receives hydraulic pressure from the hydraulic pump, the hydraulic pump must promptly reduce the tilt angle of its swash plate to prevent overload of the pump drive prime mover. However, it is difficult for the conventional device to secure sufficient responsiveness in order to secure stability.

The present invention has been made in consideration of the above circumstances, and has a high responsiveness when the control amount is large, and a low responsiveness and a high stability when the control amount is small. It is an object of the present invention to provide a control device for a variable displacement hydraulic pump having various configurations.

[Means for solving problems]

A control device for a variable displacement hydraulic pump according to the present invention comprises a first
In the variable displacement hydraulic pump including the hydraulic servo mechanism U for changing the tilt angle of the swash plate as shown in the figure, the servo pressure is introduced into the servo chamber 2a of the hydraulic servo cylinder mechanism 2 of the hydraulic servo mechanism U. The oil passage switching mechanism 3 for switching the oil passages 6a, 6b to be provided is provided, and the port 33 formed in the oil passage switching mechanism 3 and communicating with the one oil passage 6a communicating with the servo chamber 2a is the port. A low response passage consisting of at least one pair of drill holes having a small cross-sectional area, which are spaced in the axial direction of the spool so as to correspond to the vicinity of both ends of the land of the spool 35 in the neutral position for closing 33, and the at least one pair of low response. And a high response passage formed by at least one pair of drill holes each having a larger cross-sectional area than the low response passage and located in the axial direction of the spool between the passages. Which one Even when moving in the opposite direction, if it is less than the predetermined movement amount, only one low response passage is opened to be in the low response state, and if it is more than the predetermined movement amount, one low response passage and the high response passage are opened to become high response state. It is composed of.

[Action]

In the controller for the variable displacement hydraulic pump according to the present invention, the spool 35 of the oil passage switching mechanism 3 for switching the oil passages 6a, 6b for introducing the servo pressure to the servo chamber 2a of the servo cylinder mechanism 2 of the hydraulic servo mechanism U is , The servo piston 2b and the pilot spool mechanisms 4 and 5 included in the hydraulic servo mechanism U are operatively connected, and then receive a control command (control input) to operate.

When the control input is small and the movement amount of the spool 35 is small, one of the low response passages having a small cross-sectional area is opened, so that the servo chamber 2a of the servo cylinder mechanism 2 receives the servo pressure through the one low response passage. Connected to the source,
The responsiveness of the servo cylinder mechanism 2 is low, that is, the stability is high. On the other hand, when the control input is large and the movement amount of the spool 35 is large, in addition to any one of the low response passages, one of the high response passages having a large cross-sectional area is opened. Since the servo chamber 2a is connected to the servo pressure supply source via one of the low response passage and the high response passage, the responsiveness of the servo cylinder mechanism 2 is enhanced.

[Effect of device]

According to the control device for a variable displacement hydraulic pump of the present invention, as described above, the port communicating with one oil passage communicating with the servo chamber corresponds to the vicinity of both ends of the spool in the neutral position. At least one pair of axially spaced low-response passages of small cross-section, and a larger cross-sectional area than at least one pair of axially spaced low-response passages of the spool between the low-response passages; With a simple structure consisting of a high response passage, when the spool moves from the neutral position to either refueling or oil draining, when the control amount is small and the responsiveness is small while the control amount is small The stability of can be secured.

Moreover, both the low response passage and the high response passage are drill holes that can be easily and accurately formed by, for example, drilling or the like, and therefore can be implemented easily and inexpensively.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the control device for the variable displacement hydraulic pump includes a hydraulic servo mechanism U for changing the tilt angle of the swash plate 1 of the variable displacement hydraulic pump P. , Servo cylinder mechanism 2 and servo chamber oil passage for introducing servo pressure to servo chamber 2a of servo cylinder mechanism 2
6a, 6b, the oil passage switching mechanism 3 interposed in the servo chamber oil passages 6a, 6b, and the discharge pressure Pd of the hydraulic pump P as a control command are received to drive the spool 35 of the oil passage switching mechanism 3. A horsepower control pilot spool mechanism 4 and a flow rate control pilot spool mechanism 5 that receives the external pilot pressure Pi as a control command and drives the spool 35 of the oil passage switching mechanism 3 are provided.

The oil passage switching mechanism 3 is a spool valve mechanism, and is a first port connected to the discharge passage 12 of the variable displacement hydraulic pump P.
32, a second port 33 that communicates with the servo chamber 2a of the servo cylinder mechanism 2, a third port 34 that communicates with the oil tank 9 through the drain oil passage 8, a spool mounting hole 31, and a slidable portion for this. And a spool 35 attached to the.

As shown in FIG. 2, the spool mounting hole 31 is formed in the fixed sleeve 14 fitted and fixed in the cylindrical hole 13a of the housing 13, and the first port 32 and the second port 33 are fixed sleeve 14. And the first port 32 is formed by the oil passages 6a, 6b formed in the housing 13 and the discharge passage 12 of the hydraulic pump P is formed.
The second port 33 is connected to the servo chamber 2a by oil passages 6a and 6b formed in the housing 13. This spool 35 is a first land 35a that opens and closes the second port 33.
And a second land 35b provided on the right side of the first land 35a with a predetermined distance.

The input shaft 35a of the spool 35 is connected to the servo piston 2b of the servo cylinder mechanism 2 via the feedback lever 7 and the pilot spool 41 of the horsepower control pilot spool mechanism 4 via the feedback lever 7 and the horsepower control link 10. Is linked to the pilot spool 51 of the flow control pilot spool mechanism 5 through the feedback lever 7 and the flow control link 11. The spool 35 is elastically biased toward the input shaft 35a by the compression coil spring 36. The pilot spool 41 of the horsepower control pilot spool mechanism 4 or the external pilot pressure that is displaced by receiving the discharge pressure Pd
When the pilot spool 51 of the pilot spool mechanism 5 for flow control which receives Pi and displaces to the left in the figure due to an increase in the control command, the spool 35 displaces in the same direction as the first land 35a and moves. 2 The port 33 is displaced from the neutral position where it closes to the refueling position. At this refueling position, the first land 35a blocks the connection between the second port 33 and the third port 34, and the first port 32 and the second port 33 communicate with each other on the right side of the first land 35a. It has become. Further, the pilot spool 41 of the horsepower control pilot spool mechanism 4 which is displaced by receiving the discharge pressure Pd or the pilot spool 51 of the flow rate control pilot spool mechanism 5 which is displaced by receiving the external pilot pressure Pi is reduced by the control command. When displaced to the right, the spool 35 is displaced from the neutral position to the oil discharge position. At this oil discharge position, the first land 35a blocks the connection between the first port 32 and the second port 33, and the first land 35a
The second port 33 and the third port 34 are communicated with each other on the left side of a.

The second port 33 is provided in the spool mounting hole 31 near the left and right ends of the first land 35a of the spool 35 located at the neutral position.
Two pairs of low response passages 33a having a small cross-sectional area, which are open to each other, and are separated from each other in the axial direction of the spool 35;
Two pairs of high response passages 33b having a large cross-sectional area opening between the spool mounting holes 31 between them, and two pairs of high response passages 33b separated in the axial direction of the spool 35 are formed. These low response passages 3
The 3a and the high response passage 33b are formed by a drill hole that is easily and precisely formed by drilling.

In the control device for a variable displacement hydraulic pump described above, when the amount of increase or decrease of the discharge pressure Pd or the external pilot pressure Pi is small, the spool 35 is slightly displaced from the neutral position in the oil supply position direction or the oil discharge position direction, and the one side The two low response passages 33a having a small cross section are opened. Therefore, the second port 3
The amount of oil flowing through 3 is throttled, and the displacement speed of the servo piston 2b is restricted to be slow (see FIG. 4). As a result, the sensitive movement of the servo piston 2b is prevented, and overcontrol and hunting are prevented. On the other hand, when the amount of increase or decrease of the discharge pressure Pd or the external pilot pressure Pi is large, the spool 35 is largely displaced from the neutral position toward the oil supply position or the oil discharge position, and the two small cross-sectional areas on one side. The low response passage 33a is opened and the two high response passages 33b having a large cross-sectional area on one side are opened (see FIG. 4). As described above, according to the control device for the variable displacement hydraulic pump, the second port 33 is configured by the low response passage 33a and the high response passage 33b which are the drill holes that can be easily and accurately formed by drilling. As a result, it is possible to obtain the effect that the control stability when the control amount is small can be secured without impairing the control responsiveness when the control amount is large.

In the above embodiment, the case where the spool valve mechanism is used as the oil passage switching mechanism 3 has been described, but the present invention can be applied to the case where an oil passage switching mechanism including a spool / sleeve mechanism is used instead of the spool valve mechanism. Of course. Further, the servo piston 2b of the above embodiment has a large diameter on the servo chamber 2a side and a small diameter on the opposite side, but it is needless to say that it may be a servo cylinder mechanism having servo pistons having the same diameter at both ends. .

The oil passage switching mechanism 3, the horsepower control pilot spool mechanism 4, the flow rate control pilot spool mechanism 5 and the like in the above embodiment are only shown in one embodiment, and those other than the characteristic constitution of the present invention are well known. Various mechanisms of can be adopted.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a block diagram of a control device for a variable displacement hydraulic pump, FIG. 2 is a longitudinal sectional view of an oil passage switching mechanism, and FIG. Is a sectional view taken along the line III-III, FIG. 4 is a valve opening characteristic diagram thereof, and FIG. 5 is a longitudinal sectional view of essential parts of a conventional oil passage switching mechanism. P: Variable displacement hydraulic pump, U: Hydraulic servo mechanism,
Pd ... Discharge pressure, Pi ... External pilot pressure, 1 ... Swash plate,
2 ... Servo cylinder mechanism, 2a ... Servo chamber, 2b ... Servo piston, 3 ... Oil passage switching mechanism, 4 ... Horsepower control pilot spool mechanism, 5 ... Flow rate control pilot spool mechanism, 6a, 6b …… Oil passage, 33 …… Second port, 33a
...... Low response passage, 33b ...... High response passage, 35 ...... Spool, 35a ...... First land.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-59-194180 (JP, A) Sekikai-Sho 60-121565 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A variable displacement hydraulic pump having a hydraulic servo mechanism for changing a tilt angle of a swash plate, wherein an oil passage for introducing servo pressure to a servo chamber of a hydraulic servo cylinder mechanism of the hydraulic servo mechanisms is provided. An oil passage switching mechanism for switching is provided, and a port formed in the oil passage switching mechanism that communicates with one oil passage communicating with the servo chamber is located near both ends of the land of the spool at a neutral position for closing the port. A low response passage having a small cross-sectional area and comprising at least one pair of drill holes axially separated from the spool so as to correspond to the portion,
A high response passage which is located between the at least one pair of low response passages and is axially separated from the spool and has at least one pair of drill holes having a larger cross-sectional area than the low response passage; When moving from either direction to refueling or draining oil, if it is less than the predetermined movement amount, only one low response passage opens, and if it is more than the predetermined movement amount, one low response passage and one high response passage are opened. A control device for a variable displacement hydraulic pump, which is configured to be in an open high response state.