SU1721344A1 - Positive-displacement hydraulic drive - Google Patents

Abstract

The invention relates to hydraulic transmissions and can be used in drives of lifting machines and transmissions of vehicles. The purpose of the invention is to improve the dynamic characteristics by introducing negative feedback on the average pressure in the power hydrolines acting on the pressure of the feed pump, is achieved by the fact that the discharge system of the pump 1 is equipped with two check valves 17, 18, the inputs of which are communicated with the power hydraulic lines 3, 4, and the output of the safety valve 16 - with a hydroline feed. The make-up system is provided with a pressure valve 10. The cavities 13, 14 of which are connected to the power lines 3, 4, the inlet with the outlet of the pump 7 of the feed, and the outlet with its suction. 3 hp f-ly, 1 ill.

Description

Taking into account the fact that the control cavity 13 is directly connected to hydroline 3, the control cavity 14 is connected to hydroline 4, and the spring cavity 15 to the input of the sub-head element 8 (battery fluid cavity), the force Рд can be expressed as follows:

Рд -j- (Рз + Р4) -А-Р

Sign

Rd Rz-P4.

(7)

10 Solving equations (6) and (7) together, find

one

15

Rz - -k (Rmax + R Podp RD); R4-t; - (Rmaks + Rnap Rd).

(eight). (9)

where Рз, Р4 are the current pressures of the working fluid in hydrolines 3 and 4, respectively. Taking into account expressions (1) - (3), based on the equilibrium equation of the spool 10

RdR

etc

: 0,

get

-y (РЗ + Р4)

4- (P

Max

+ RPAIR) d (Hmaks X).

Since due to the appropriate choice of parameters of the pressure valve 9

A C Hmaks p (Rmaks - R Podpod),

what was indicated above, then the value of g-d- (Hmaks - X) is obviously much less

magnitude-y (Rmax-R Podp) and compared

with the latter it can be neglected.

Thus, for the hydraulic drive under consideration, in the absence of a force contact of the spool 10 in the axial direction with the body parts of the pressure valve 9, the equality

-tr (RZ + RA) (Rmax + R Podpod), (6)

which shows that during operation of the proposed hydraulic drive, the average pressure in hydrolines 3 and 4 between the pump 1 and the hydraulic motor 2 is maintained almost

ido 1) - zo (4)

five)

out

ju

they are from 9 to et6)

barking at rocky

According to expressions (8) and (9), the maximum pressure in a less loaded

hydroline 3 and 4 takes place at Rd - 0 and

one

is (p max + p sub). Accordingly, this is the maximum pressure that

25 during operation of the hydraulic drive under consideration may be at the outlet of the feed pump 7.

With an increase in pressure in one of the hydraulic lines 3 or 4 to the value of Pmax, in

30 other of the hydraulic lines 3 or 4, as follows from the expressions (8) and (9), the pressure will be equal to RPODP, .. and the pressure differential module 1РД1 on the hydraulic engine 2 will be Рmax-Р oversized. Obviously, the pressure of the working fluid at the outlet of the feed pump 7 will then be Rsub.

If the pressure in one of the hydraulic lines 3

or 4 exceeds the Pmax value (for example,

due to hydraulic overload or

increase the temperature of the working fluid), then the fluid from the more loaded hydraulics through the corresponding check valve 17 or 18, the safety valve 16 adjusted to the pressure drop (Rmax - Ppp), and the corresponding 45 of the check valves 6 or 5 loaded hydroline. In this case, part of the fluid that has passed through the safety valve 16 can flow to the element of the sub-pressure 8 through the maximum opening in this case, the flow area of pressure valve 9.

From the obtained expressions (8) and (9), it can be seen that when the pressure differential Rd changes on the hydraulic engine 2 (and therefore

55 when the load on the output link of the hydraulic motor is changed), the pressures P3 and P3 in both hydrolines 3 and 4 between pump 1 and hydraulic motor 2 change simultaneously in opposite phase. At the same time, the rate of pressure change in each of these hydrolines (and

respectively, in the adjacent cavity of the pump 1 and the hydraulic engine 2) in absolute value is twice less than the rate of change of pressure difference on the hydraulic engine

d pa dt

dPf dt

Since the flow rate associated with its compressibility and flexibility of the walls of the hydraulic channels is proportional to the rate of change of pressure, all other things being equal, when the proposed hydraulic drive is working, its elastic properties are less pronounced and, consequently, the proposed hydraulic drive has an increased stiffness and, accordingly, higher natural frequency and speed.

Claims (4)

Claim 1. A volumetric hydraulic transmission comprising an adjustable pump, a hydraulic motor, power hydrolines telling them in a closed circuit, a discharging system for an adjustable pump with a safety valve and a make-up system with a booster pump, backpressure element and check valves, whose inputs communicate with feed line of the pump, and the outlets are with power lines, because, in order to improve the dynamic transmission characteristics by introducing negative feedback by the amount of pressure of the feed pump, the adjustable pump you 10 15 20 complete with two flow directions, the make-up system is equipped with a spool pressure valve with two control cavities on one side of the spool and a spring on the other, with each of the control valve cavities of the pressure valve connected to one of the power lines, pump feed, and the output - with the element backwater. 2. Transmission according to claim 1, which is so tangible that the effective areas of the ends of the valve spool of the pressure from the side of each of its control cavities are equal to each other. 3. Transfer to PP. 1 and 2, that is, that the cavity of the pressure valve in which the spring is placed is in communication with the support element, and the force of the preliminary pressing of the spring is determined from the expression RPPU (Rmaks RSPP) C X Max, where A is the sum of the effective areas of the control cavities, is equal to the effective area affected by the pressure of the backwater; Rmax - the maximum allowable pressure in the transmission; R subsp - pressure backwater; C - spring stiffness; HMax - maximum displacement of the spool. 4. Transfer by PP. 1-3, characterized in that the supporting element is made in the form of a hydroaccumulator, and the inlet of the feed pump is connected to its hydraulic cavity.