GB1588885A - Hydrostatic power transmission in series with a changespeed gear - Google Patents

Hydrostatic power transmission in series with a changespeed gear Download PDF

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Publication number
GB1588885A
GB1588885A GB4453377A GB4453377A GB1588885A GB 1588885 A GB1588885 A GB 1588885A GB 4453377 A GB4453377 A GB 4453377A GB 4453377 A GB4453377 A GB 4453377A GB 1588885 A GB1588885 A GB 1588885A
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United Kingdom
Prior art keywords
control
piston
hydrostatic
valve
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB4453377A
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ZF Friedrichshafen AG
Original Assignee
ZF Friedrichshafen AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by ZF Friedrichshafen AG filed Critical ZF Friedrichshafen AG
Priority to GB4453377A priority Critical patent/GB1588885A/en
Publication of GB1588885A publication Critical patent/GB1588885A/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/46—Automatic regulation in accordance with output requirements
    • F16H61/465—Automatic regulation in accordance with output requirements for achieving a target input speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H61/00—Control functions within control units of change-speed- or reversing-gearings for conveying rotary motion ; Control of exclusively fluid gearing, friction gearing, gearings with endless flexible members or other particular types of gearing
    • F16H61/38—Control of exclusively fluid gearing
    • F16H61/40—Control of exclusively fluid gearing hydrostatic
    • F16H61/46—Automatic regulation in accordance with output requirements

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gear-Shifting Mechanisms (AREA)
  • Control Of Transmission Device (AREA)

Description

(54) A HYDROSTATIC POWER TRANSMISSION IN SERIES WITH A CHANGE-SPEED GEAR (71) We, ZAHNRADFABRIK FRIEDRICHSHAFEN AKTIENGESELLSCHAFT, of Friedrichshafen-on-the-Bodensee, Federal Republic of Germany, a Joint-Stock Company organised under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a hydrostatic power transmission in series with a changespeed gear which includes clutches to be shifted when a gear change is made, the hydrostatic transmission being operated in dependence on the rotational speed of said clutches and having a device for controlling the transmission ratio which comprises a first valve operable in dependence on the difference in rotational speed between driving and driven sides of the clutch which is to be shifted, said valve controlling the operation of a pair of actuating pistons acting in opposite directions on an adjusting linkage of the control device to adjust the linkage in order to compensate for a shift step, the control device also having a control cylinder/piston assembly and a regulating cylinder/piston assembly.
The starting point of the invention is the prior art as disclosed, for example, by German Offenlegungsschrift No. 2,307.550.
According to this prior art the shift behaviour of a change-speed gear following a hydrostatic transmission is improved in that for the purpose of adapting the speed of rotation of the clutch which is to be operated in the change-speed gear on the commencement of a gear shift the output speed of rotation of the hydrostatic transmission is controlled to follow the positive or negative shift step of the rotational speed which is to be shifted. For this purpose it is possible to use the difference in speed of rotation between driving and driven sides of the clutch signalled by speed pick-ups on the clutch which is to be shifted for the purpose of operating a servo actuating valve, which then operates the actual adjusting device itself.
In the power regulation described in German Offenlegungsschrift 2,307,550 the regulating linkage of the power controlling device and consequently also the adjusting linkage leading from the control device to the hydrostatic adjusting pump are acted on directly by means of a separate actuating piston. This gives rise to two disadvantages: firstly, heavy actuating forces are necessary, which require high-power actuators which are consequently usually relatively large in size, while secondly during the gear shift there occur torque peaks in the form of positive and negative pressure peaks, which act on the control device through the operating pressure and produce interference pulses in it during the adjustment. The quality of the shift is impaired by these pulses.
The problem which the invention aims at solving consists in improving the adjustment of the hydrostatic transmission for the purpose of the follow-up control of the speed of rotation during the gear change, and avoiding interference pulses resulting from pressure peaks.
Accordingly, the present invention consists in a hydrostatic power transmission in series with a change-speed gear which includes clutches to be shifted when a gear change is made, the hydrostatic transmission being operated in dependence on the rotational speed of said clutches and having a device for controlling the transmission ratio which comprises a first valve operable in dependence on the difference in rotational speed between driving and driven sides of the clutch which is to be shifted, said valve controlling the operation of a pair of actuating pistons acting in opposite directions on an adjusting linkage of the control device to adjust the linkage in order to compensate for a shift step, the control device also having a control cylinder/piston assembly and a regulating cylinder/piston assembly, a vent valve being provided which serves during the gear change to vent the pressure chamber of the control cylinder/piston assembly and of the regulating cylinder/ piston assembly, a shut-off valve at the same time closing a pipe connecting the highpressure circuit of the hydrostatic transmission to the pressure chamber of the regulating cylinder/piston assembly.
Although it is known from German Auslegeschrift No. 1,750,503 for the power regulating elements of the hydrostatic part of a compound hydrostatic-mechanical transmission provided with shift clutches to be briefly separated from the control pressure acting on the control device during the shifting of the clutches, that is to say to make them ineffective, nevertheless in this arrangement the influence of the highpressure circuit is not taken into account.
Consequently for the brief duration of the shift the control device comes under the influence of the pressure fluctuations transmitted to the hydrostatic transmission highpressure circuit in consequence of torque shocks on the shifting of the clutches. which is precisely what the present invention seeks to prevent.
The invention ensures in a simple manner that in the clutch shift phase the control device is "unlocked" and its actuation or follow-up control is then effected only in dependence on the difference in rotational speed between driving and driven sides of the clutches. while load variations resulting from the dvnamic cycle of the gear change are no longer superimposed on this followup control operation in the form of pressure peaks. The qualitv of the gear shift is thereby considerably improved. Furthermore, the advantage is gained that the control device can now be made considerably lighter and smaller because of the low actuating forces now required.
In order that the invention mav be more readily understood. reference is made to the accompanying drawing which illustrates di agrammatically and by way of example one embodiment thereof.
A hydrostatic transmission I. comprising a hvdrostatic motor and a hydrostatic pump.
the delivery power of which is usually adjuStable. is driven bv an internal combustion engine 2 or other propulsion enginc. A control device 3 effects the adjustment and adaptation regulation of the hydrostatic transmission 1.
A control piston 4 of the device 3 is movable in a cylinder 4c and is acted on by a variable control pressure, and against the action of a spring 6 effects an adjustment path in the device 3 and consequently also a variation of stroke, that is to say a variation of transmission ratio in the hydrostatic transmission 1.
In the arrangement illustrated a control pressure is applied which is dependent on speed of rotation and which is obtained through a constant displacement pump 17, whose delivery is dependent on speed of rotation, in conjunction with a throttle 18 of constant cross-section.
An operating pressure proportional to load has a restoring action via a pipe 20 on a regulating piston 5 of the device 3, which piston is movable in a cylinder 5c.
The control piston 4 and regulating piston 5 act on an adjusting lever 7 of the control and regulating device 3 and adjust the hydrostatic transmission 1 via a reversing device 8. In order to make it possible for the hydrostatic transmission 1 to be adjusted freely during a gear shift operation and to eliminate the influences of control pressure and load fluctuations, the pressure chambers 4a and 5a of the pistons 4 and 5 are vented by means of a valve 15 and connected to an oil return 10.
Since the operating pressure should not fall during the gear shift operation and since the full load should be transmitted through the clutch which is to be shifted, the pipe 20 extending to the regulating piston pressure chamber 5a is at the same time closed with the aid of a shut-off valve 19. The follow-up control of the hydrostatic transmission is effected by means of an adjusting device 9 having two actuating pistons 13, 14. For an upward gear shift the piston 13 of the device 9 is operated. that is to say the ratio of the hydrostatic transmission is reduced, while for a downward gear shift the piston 14 of the device 9 is operated and the ratio of the hydrostatic transmission is therefore increased.
The adjusting time is delayed by one of two orifices 11 or 12. In each particular case the orifice associated with the piston not loaded with pressure comes into action. The other piston is connected via its associated non-return valve to the oil supply, which is thus not throttled. The follow-up control of the hydrostatic transmission is initiated by means of a directional valve 16, which is operated by known rotational speed pickups (German Published Specification No.2.307.550) not shown in the drawing.
WHAT WE CLAIM IS: 1. A hydrostatic power transmission in series with a change-speed gear which includes clutches to be shifted when a gear change is made, the hydrostatic transmission being operated in dependence on the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. controlling the operation of a pair of actuating pistons acting in opposite directions on an adjusting linkage of the control device to adjust the linkage in order to compensate for a shift step, the control device also having a control cylinder/piston assembly and a regulating cylinder/piston assembly, a vent valve being provided which serves during the gear change to vent the pressure chamber of the control cylinder/piston assembly and of the regulating cylinder/ piston assembly, a shut-off valve at the same time closing a pipe connecting the highpressure circuit of the hydrostatic transmission to the pressure chamber of the regulating cylinder/piston assembly. Although it is known from German Auslegeschrift No. 1,750,503 for the power regulating elements of the hydrostatic part of a compound hydrostatic-mechanical transmission provided with shift clutches to be briefly separated from the control pressure acting on the control device during the shifting of the clutches, that is to say to make them ineffective, nevertheless in this arrangement the influence of the highpressure circuit is not taken into account. Consequently for the brief duration of the shift the control device comes under the influence of the pressure fluctuations transmitted to the hydrostatic transmission highpressure circuit in consequence of torque shocks on the shifting of the clutches. which is precisely what the present invention seeks to prevent. The invention ensures in a simple manner that in the clutch shift phase the control device is "unlocked" and its actuation or follow-up control is then effected only in dependence on the difference in rotational speed between driving and driven sides of the clutches. while load variations resulting from the dvnamic cycle of the gear change are no longer superimposed on this followup control operation in the form of pressure peaks. The qualitv of the gear shift is thereby considerably improved. Furthermore, the advantage is gained that the control device can now be made considerably lighter and smaller because of the low actuating forces now required. In order that the invention mav be more readily understood. reference is made to the accompanying drawing which illustrates di agrammatically and by way of example one embodiment thereof. A hydrostatic transmission I. comprising a hvdrostatic motor and a hydrostatic pump. the delivery power of which is usually adjuStable. is driven bv an internal combustion engine 2 or other propulsion enginc. A control device 3 effects the adjustment and adaptation regulation of the hydrostatic transmission 1. A control piston 4 of the device 3 is movable in a cylinder 4c and is acted on by a variable control pressure, and against the action of a spring 6 effects an adjustment path in the device 3 and consequently also a variation of stroke, that is to say a variation of transmission ratio in the hydrostatic transmission 1. In the arrangement illustrated a control pressure is applied which is dependent on speed of rotation and which is obtained through a constant displacement pump 17, whose delivery is dependent on speed of rotation, in conjunction with a throttle 18 of constant cross-section. An operating pressure proportional to load has a restoring action via a pipe 20 on a regulating piston 5 of the device 3, which piston is movable in a cylinder 5c. The control piston 4 and regulating piston 5 act on an adjusting lever 7 of the control and regulating device 3 and adjust the hydrostatic transmission 1 via a reversing device 8. In order to make it possible for the hydrostatic transmission 1 to be adjusted freely during a gear shift operation and to eliminate the influences of control pressure and load fluctuations, the pressure chambers 4a and 5a of the pistons 4 and 5 are vented by means of a valve 15 and connected to an oil return 10. Since the operating pressure should not fall during the gear shift operation and since the full load should be transmitted through the clutch which is to be shifted, the pipe 20 extending to the regulating piston pressure chamber 5a is at the same time closed with the aid of a shut-off valve 19. The follow-up control of the hydrostatic transmission is effected by means of an adjusting device 9 having two actuating pistons 13, 14. For an upward gear shift the piston 13 of the device 9 is operated. that is to say the ratio of the hydrostatic transmission is reduced, while for a downward gear shift the piston 14 of the device 9 is operated and the ratio of the hydrostatic transmission is therefore increased. The adjusting time is delayed by one of two orifices 11 or 12. In each particular case the orifice associated with the piston not loaded with pressure comes into action. The other piston is connected via its associated non-return valve to the oil supply, which is thus not throttled. The follow-up control of the hydrostatic transmission is initiated by means of a directional valve 16, which is operated by known rotational speed pickups (German Published Specification No.2.307.550) not shown in the drawing. WHAT WE CLAIM IS:
1. A hydrostatic power transmission in series with a change-speed gear which includes clutches to be shifted when a gear change is made, the hydrostatic transmission being operated in dependence on the
rotational speed of said clutches and having a device for controlling the transmission ratio which comprises a first valve operable in dependence on the difference in rotational speed between driving and driven sides of the clutch which is to be shifted, said valve controlling the operation of a pair of actuating pistons acting in opposite directions on an adjusting linkage of the control device to adjust the linkage in order to compensate for a shift step, the control device also having a control cylinder/piston assembly and a regulating cylinder/piston assembly, a vent valve being provided which serves during the gear change to vent the pressure chamber of the control cylinder/piston assembly and of the regulating cylinder/ piston assembly, a shut-off valve at the same time closing a pipe connecting the highpressure circuit of the hydrostatic transmission to the pressure chamber of the regulating cylinder/piston assembly.
2. A transmission as claimed in claim 1, wherein on commencement of the gear shift the shut-off valve closes the connecting pipe and the vent valve connects the said pressure chambers to an oil return, and at the end of the gear shift the vent valve closes the pressure chambers and the shut-off valve opens the connecting pipe.
3. A hydrostatic power transmission in series with a change-speed gear, substantially as herein described with reference to and as shown in the accompanying drawing.
GB4453377A 1977-10-26 1977-10-26 Hydrostatic power transmission in series with a changespeed gear Expired GB1588885A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB4453377A GB1588885A (en) 1977-10-26 1977-10-26 Hydrostatic power transmission in series with a changespeed gear

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4453377A GB1588885A (en) 1977-10-26 1977-10-26 Hydrostatic power transmission in series with a changespeed gear

Publications (1)

Publication Number Publication Date
GB1588885A true GB1588885A (en) 1981-04-29

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ID=10433748

Family Applications (1)

Application Number Title Priority Date Filing Date
GB4453377A Expired GB1588885A (en) 1977-10-26 1977-10-26 Hydrostatic power transmission in series with a changespeed gear

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GB (1) GB1588885A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986000963A1 (en) * 1984-07-30 1986-02-13 Sauer Italiana S.P.A. Manual and automatic governor for a hydrostatic transmission

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1986000963A1 (en) * 1984-07-30 1986-02-13 Sauer Italiana S.P.A. Manual and automatic governor for a hydrostatic transmission

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PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee