Performance and characteristics of the hottest DM

The performance and characteristics of DM series hydraulic motor

DM series hydraulic motor is a low-speed high torque hydraulic motor with equal contact stress. It is a new product designed with the latest theory of non pulsating contact stress. Its performance features are: high working pressure, high efficiency, long service life and low noise. The structure features end face flow distribution and hydrostatic support. This series of products are widely used in engineering machinery, such as the hydraulic drive system of the drum of concrete mixer truck, the traveling mechanism of roadheader and road construction machinery, cranes and forklifts, which need to use hydraulic motors. It can replace blade motors, gear motors, cycloid Marta and various series of low-speed high torque hydraulic motors

1 performance characteristics of DM series hydraulic motor

1.1 equal contact stress structure - long service life

the hydraulic motor is designed according to the equal contact stress theory: the convex section of the cam curve is relatively flat, which eliminates the peak value of contact stress and reduces the pressure value. The expected life l of the hydraulic motor can be calculated according to the following formula:

l= (c0/60 × n) × (1/σ ten × Z) Where C0 -- constant value of raceway material n -- rotational speed of compression motor σ—— The contact stress value Z between the hydraulic element and the raceway -- the number of plungers of the hydraulic motor

when l is equal to the fixed value, the optimized design makes (1/σ ten × Z) Minimum, the motor with the most compact structure and the lightest weight can be calculated. In other words, it can be designed according to the requirements of the expected working life of the hydraulic motor, and it can also design products with the highest expected working life according to the restrictions of the host on the structural size and weight of the hydraulic motor. As shown in Figure 1, the working life expectancy of different raceway curves varies greatly

l.2 end face flow distribution structure - high volumetric efficiency

the oil distribution plane is designed according to the oil film support theory, and the back pressure should be appropriately greater than the separation force, so that the clearance of the distribution surface can be automatically reduced and the leakage can be reduced, but the oil film of a certain thickness can still be maintained between the distribution surfaces to avoid rapid wear. At the same time, a spring is installed at the bottom of the valve plate to push the valve plate towards the cylinder block to obtain the preload. After the oil pressure has not been established or the valve surface is worn, the cylinder block and the valve surface will not be separated, affecting the volumetric efficiency

we know from the calculation formula of volumetric efficiency: η v=Qt/（Qt＋∑M） × 100%, of which the hydraulic motor volume leakage Σ Δ Q＝ Δ Q1＋ Δ Q2＋ Δ Q3。

Δ Q1 refers to the leakage at the clearance of the valve distribution surface (shaft), accounting for about 70% - 80% of the total leakage; Δ Q2 refers to the leakage at the gap between the plunger and the cylinder hole

Δ Q3 is the volume loss caused by the elastic compression of the liquid at the bottom of the plunger

when the product design is finalized, the actual impact η The main factors of V are Δ Q1, for shaft distribution, the distribution clearance changes sharply with the accuracy and wear of parts; For the end face distribution, it is designed according to the oil film support theory. Under the working state, the gap between the two distribution planes is only a layer of oil film, so Δ Q2； Can be greatly reduced. In the actual product bench test, its volumetric efficiency η V up to 99%, sometimes it must be adjusted appropriately for the needs of the product Δ Q2。 Wait to make Δ Q2 decreased slightly

1.3 using oil-free bearings, light coincidence and low noise

1.4 when the manufacturer of high-speed motor makes great efforts to improve every efficiency percentage point, the reducer attached to the output shaft will greatly reduce the result of this effort, while using DM series hydraulic motor to drive directly will not have these troubles. Because the intermediate link of the mechanical reducer is omitted or reduced, the power loss caused by the reducer is avoided, and the overall transmission efficiency is improved. As we all know, every intermediate link means incidental power loss. A well-made gear pair will lose 1% - 5% of transmission power. With the loss of oil and bearings, the total loss is considerable

dm series hydraulic motors have the following two points through the preventive measures taken by Jiangsu hydraulic product quality inspection center: 1. Measured, the maximum total efficiency is more than 94%, and its performance curve is shown in Figure 2

2 structural features of DM series hydraulic motors

2.1 various connection modes

2 1.1 mutual torque transmission mode

(L) flange structure plus transmission shaft output flange structure can be designed into disc structure, waist drum structure, quadrilateral or polygon structure according to needs

(2) the hydraulic drive axle is composed of two hydraulic motors of the same model, with double output shafts, which are independent of each other and can be reversed (i.e. with differential function). It can replace the drive axle of all kinds of low-speed vehicles to drive all kinds of low-speed vehicles, mainly used for forklift and vehicle travel drive

(3) wheel motor hydraulic motor is directly installed on the wheel and is mainly used for vehicle travel drive

(4) two speed hydraulic motor

① two speed hydraulic motor is generally used in occasions where the torque required by the host is small at high speed and large at low speed. Using two speed hydraulic motor and quantitative pump to realize low-speed full torque and high-speed half torque can improve work efficiency and reduce the power of prime mover, which is practical, energy-saving and more economical

② when the two speed hydraulic motor is in the working condition of small displacement, at each instant, some pistons in the hydraulic motor are in the suction state, so at this time, the back pressure of the hydraulic motor is required to be 0.4-l.1 im PA, which is actually subject to the sound of no rolling element knocking on the raceway during operation

③ the variable methods of two speed hydraulic motor include hydraulic control and manual control

④ it is generally used to start the hydraulic motor under the condition of large displacement, allowing the control valve to be operated during operation to realize the step speed change of the hydraulic motor

(5) hydraulic motor with brake

① the opening and closing of mechanical brake is controlled, but after raising and putting into operation, the oil circuit. When the control pressure is greater than the brake opening pressure, the mechanical brake automatically opens and the hydraulic motor starts to work, otherwise, the mechanical brake is in a normally closed state

② the opening pressure of mechanical brake is 4-6mpa

③ mechanical brake and hydraulic motor are designed as a whole, with compact structure, small volume, light weight, stable and reliable operation and long service life

2.1.2 hydraulic transmission connection

axial threaded connection, axial plate connection, radial threaded connection, radial plate connection

2.2 adopt modular structure

the motor adopts the integrated plunger roller pair direct transmission mode to replace the beam transmission mode that has been used all the time, which greatly simplifies the structure, significantly reduces the radial size and overall weight, and is especially suitable for the modular configuration mode

the core component of the motor is the raceway with inner curve and the radial plunger, so it is basically distributed by the rotor and plane with idle sub pairs. In the whole DM series, various sizes of plungers are used, which are distributed in one row, two rows or three rows of cylinder blocks. The number of stator raceway curves is 6 or 8, and the corresponding row of plunger is 8 or 10. This core component is responsible for converting hydraulic energy into mechanical energy and output torque, and realizing the step change of displacement. Other components are responsible for installing and fixing rotors and stators, and bearing the axial and radial forces inside and outside the motor. This design ensures that a variety of connection modes can be configured on the same core components

3 selection principle of DM series hydraulic motor

(L) inner curve hydraulic motor is suitable for transmission devices requiring low speed and high torque. If the parameters are appropriate, it can be directly transmitted without gear box deceleration, which saves the cost of reducer, and has small volume, compact structure and convenient installation

(2) select dmg-e series or DMQ series hydraulic motor under the condition of bearing radial force

(3) for occasions with high system pressure, if it is greater than 16MPa, DMQ series can be selected, and if it is less than this pressure, one of the two can be selected as needed

(4) when the inner curve motor is used, a certain back pressure must be guaranteed to avoid the piston pair from separating from the raceway, which will cause the failure of the impact pressure tester to be removed, and the back pressure should be increased with the increase of the speed

(5) the external leakage pipe is required to be connected back to the oil tank. If it is connected with the oil return pipe, its pressure should not exceed one atmospheric pressure