译文：
很多工程机械的工况要求其工作马达在下面两种状态下交替工作：一种是要求马达输出大转矩，保持低转速；另一种是要求马达输出小转矩，保持高转速。而此时由于液压油的压力和流量不易改变，满足不了工况要求。为了达到设计目的，我们只能采用以下两种办法：一种是选用变量马达，另一种办法是采用两个定量马达并联和串联切换的方法。 下面介绍一种能实现马达串并联切换，从而实现高低速的液控换向阀：液控双速阀结构紧凑、操作方便，能极大地简化油路连接，即使在液压油流量和液压一定时，也能可靠方便的实现马达的高低速切换。 液控双速阀的结构原理和工作过程是:该液控双速阀地阀体6为不规则的长方体，中部有一空腔，阀体6上开有6个油口与空腔相通，两个星形密封圈18分别安装在阀体6空腔中的两个沟槽中，实现阀体6与阀芯8的密封，防止液压油泄漏。阀体6的两端分别装有上端盖13和下端盖1，每个短盖分别用4个螺钉11及弹簧垫圈10固定在阀体6上，端盖为举行壳体，上端盖上的油口Ⅲ(12)为控制油口。O形圈9放置于上端盖13的沟槽中。滑动阀芯8装于配于阀体6的空腔中，阀芯8为圆柱形，上面开有3个油道和一个挡圈安装沟槽，分别有一个挡圈19、垫圈4和弹簧3依次穿在阀芯上的挡圈沟槽一端，弹簧的一端压着垫圈4，另一端将压盖2压紧在下端盖1的内壁上。如上端盖13的空腔内无液压油时，弹簧3则将挡圈19压紧于阀体6上，此时，阀体6上的6个油口经阀芯上的3个油道行程3组通口，第1组为油口Ⅵ(16)、油口Ⅵ(17)，第二组为油口Ⅰ(5)、油口Ⅳ(14)，第3组为油口Ⅱ(7)、油口Ⅴ(15)，实现马达Ⅰ(20)和马达Ⅱ(21)的串联;当压力油从油口Ⅲ(12)进入上端盖13的空腔时,阀芯8在压力为2×106~3×106Pa的液压油的作用下向弹簧3一侧滑动，直到阀芯8的另一端面顶在压盖2上，阀芯8才停止移动，此时，阀体6上的6个油口经阀芯上的3个油道形成两组通口，一组为油口Ⅰ(15)、油口Ⅵ(16)、油口Ⅶ(17)，另异族为油口Ⅱ(7)、油口Ⅳ(14)、油口Ⅴ(15)，实现马达Ⅰ(20)和马达Ⅱ(21)的并联。 液控双速阀已在徐工研究院开发的水平定向钻机上取得成功应用，同时也为其它液压系列解决此类工况提供了新的途径，具有很好的应用前景。

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原文：
A lot of construction machinery in working condition demands of their work in the following two kinds of state motor alternating tasks: one requiring a large motor output torque to maintain a low rotational speed; The other is a small motor output torque to maintain a high speed. But at this time due to hydraulic oil pressure and flow is not easy to change, can not meet the conditions required. In order to achieve the design purpose, we can only adopt the following two ways: one is to use a variable motor, another approach is to use two motors in parallel and serial switching of quantitative methods. The following describes a series-parallel switching can achieve motors to achieve high or low speed of the hydraulic control valve: liquid-controlled two-speed valve structure is compact, easy to operate, can greatly simplify the oil line connections, even in the hydraulic oil flow and hydraulic amount of time can also facilitate the realization of reliable high-low speed switching motors. Two-speed hydraulic control valve structure principle and working process is: The two-speed hydraulic control valve to valve 6 as an irregular cuboid, Central has a cavity on the valve 6 to open the oil port has six interlinked with the cavity, the two a star-shaped ring 18 installed in the valve body 6, respectively in the two grooves in the cavity to achieve spool valve body 6 and 8 sealed to prevent leakage of hydraulic oil. Valve 6 is installed on both ends of the respective cover 13 and cover in one, each a short cover were used four screws 11 and spring washers 10 fixed to the valve body 6, the cover for the holding of the shell, the top cover of the oil I Ⅲ (12) for the control of the oil port. O-ring 9 on the cover 13 placed on the trench. Sliding spool valve 8 installed on the distribution in the cavity 6, the spool 8 is cylindrical, the above has opened a three oil Collar Road and installation of a trench, respectively, a Collar 19, 4 and spring washer 3 turn on the Collar to wear grooves in the spool end, one end of the spring Crimping washer 4, the other side of the gland in the next two pressed on the inside cover 1. As cover 13 of the cavity-free hydraulic oil, the spring 3 Collar 19 will be pressed on the valve body 6, on this point, the valve 6 on the six oil port by the spool on the three oil Road trip Group 3 Higuchi, the first an oil port group Ⅵ (16), the oil port Ⅵ (17), the second group, the oil port Ⅰ (5), the oil port Ⅳ (14), Group 3 for the oil port Ⅱ (7 ), the oil port Ⅴ (15), achieved motor Ⅰ (20) and motor Ⅱ (21) of the series; when the pressure oil from an oil port Ⅲ (12) into the cavity on the cover 13 when the spool 8 in the pressure of 2 × 106 ~ 3 × 106Pa under the action of the hydraulic oil to the side of the sliding spring 3, until the spool face another top-eight in the gland 2, the spool 8 stopped moving, this time, valve 6 on the 6 filling port through the spool on the formation of two groups of three oil Road openings, a group for the oil port Ⅰ (15), the oil port Ⅵ (16), the oil port Ⅶ (17), the other mixed as oil port Ⅱ (7 ), the oil port Ⅳ (14), the oil port Ⅴ (15), achieved motor Ⅰ (20) and motor Ⅱ (21) in parallel. Two-speed hydraulic control valve, Xu Power Research Institute in the development of horizontal directional drilling to achieve successful application, but also for other hydraulic series of solutions to such conditions provides a new way to have a good application prospects.