CA1245130A - Hydrostatic pressure worm-rack devices - Google Patents
Hydrostatic pressure worm-rack devicesInfo
- Publication number
- CA1245130A CA1245130A CA000490581A CA490581A CA1245130A CA 1245130 A CA1245130 A CA 1245130A CA 000490581 A CA000490581 A CA 000490581A CA 490581 A CA490581 A CA 490581A CA 1245130 A CA1245130 A CA 1245130A
- Authority
- CA
- Canada
- Prior art keywords
- oil
- worm
- rack
- teeth
- hydrostatic 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
Links
- 230000002706 hydrostatic effect Effects 0.000 title claims abstract description 58
- 230000013011 mating Effects 0.000 claims abstract description 10
- 239000003921 oil Substances 0.000 description 116
- 238000010276 construction Methods 0.000 description 4
- 230000003068 static effect Effects 0.000 description 2
- 241000282887 Suidae Species 0.000 description 1
- 230000004323 axial length Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
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- Magnetic Bearings And Hydrostatic Bearings (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a hydrostatic pressure worm-rack device of the type comprising a worm formed with operating oil supply opening at the opposite flanks of respective teeth of the worm, opposite flanks of respective teeth of the rack being formed with oil pockets, there are provided an oil distributor mounted on one end of the worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of the worm and rack and for supplying pilot oil to pilot oil supply ports provided for the flanks of the teeth at the opposite ends of the worm which firstly mate with the teeth of the rack.
In a hydrostatic pressure worm-rack device of the type comprising a worm formed with operating oil supply opening at the opposite flanks of respective teeth of the worm, opposite flanks of respective teeth of the rack being formed with oil pockets, there are provided an oil distributor mounted on one end of the worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of the worm and rack and for supplying pilot oil to pilot oil supply ports provided for the flanks of the teeth at the opposite ends of the worm which firstly mate with the teeth of the rack.
Description
`-` 124~30 ~, E~YDROSTATIC PRESSURE WORM--RACK DEVICES
.
BACKGROUND OF THE INVENTION
This invention relates to a hydrostatic pressure worm-rack device utilized in a machine tool, for example.
Prior art hydrostatic pressure worm-rack devices can be classified into two types. In one type, hydrostatic pressure oil is supplied from the side of the rack, and in the other type, the hydrostatic pressure oil is supplied from the side of the?worm. Examples of the former type are disclosed in U.S. Pat. Nos. 3,789,956 and 4,148,227 and examples of the latter type are disclosed in U.S. Pat. Nos. 3,595,100 and 3,763,959. These patents illustrate a construction in which the hyd ostatic pressure oil is distributed from the end surfaces of a worm and a construction in which thrust forces g~nerated in hydrostatic pressure oil pockets provided for left and right ends of a worm are caused to balance with each other.
A hydrostatic pressure worm-rack device is used in a machine tool as a feed device. With recent increase in the feed speed of the machine tool, the number of revolutions of the worm is also increased so that lubricating oil in oil pockets provided for worm teeth flanks which do not engage with the teeth of a rack is caused to splash away by centrifugal force so that when the worm subsequently engages with the rack, air would be ,~, . .
~ .,.~
~2~5130 .. . .
- entrapped in the oil pockets which causes a pressure variation in the oil pockets, thus failing smooth high speed feeding.
Furthermore, according to the prior art S construction, since no pilot oil supply ports and pilot oil discharge~grooves are provided at both ends of the worm at which the worm begins to mesh with the rack, oil pressure would rise in the oil pockets so that air remaining in the oil pockets would not be discharged with the result that the pressure in the oil pockets pulsates which prevents smooth feeding.
According to the prior art constructions, at the time of supplying operating oil to the supply ports opening in the tooth flanks, since the operating oil is supplied through one end of the worm, pressure loss occurs before the operating oil reaches the supply ports at the far end. Accordingly, it is impossible to obtain uniform pressure in respective oil pockets, thus failing high speed feeding. ~oreove~, no means was provided for maintaining constant the pressure of the operating oil in respective oil supply ports of the tooth flanks.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved hydrostatic pressure worm-rack device capable of preventing entrapping air into oil pockets provided for the tooth flanks at both ends of the worm which do not mesh with the rack and maintaining uniform the pressure ,,",~
, ~, ~ .
1~513Q
in a plurality of hydrostatic pressure oil pockets when the worm meshes with the rack, thereby enabling smooth and high speed feeding of a machine tool, for example.
According to this invention, there is provided a hydrostatic pressure worm-rack device of the type comprising a worm formed with operating oil supply openings at opposite flanks of respective teeth of the worm, a rack meshing with the worm, opposite flanks of respective teeth of the rack being formed with hydrostatic pressure oil pockets, drive means for driving the shaft of the worm, and means for supplying the operating oil to the suFply openings of the worm, characterized in that there are provided an oil distributor mounted on one en~ of the worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of the worm and the rack and for supplying pilot oil to pilot oil ~upply ports provided for flanks of teeth at the opposite ends of the worm which firstly mate with the teeth of the rack, oil passages provided through the worm shaft and through respective teeth of the worm for independently supplying the operating oil and the pilot oil, and flow quantity adjusting valve means installed between the operating oil supply means and the oil distributor.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
~3~
~245130 Fig. 1 is a longitudinal sectional view showing an embodiment of the hydrostatic pressure worm-rack device according to this invention;
Fig. 2 is a perspective longitudinal sectional view of a distributor shown in Fig. l;
Fig. 3 is a sectional view taken along a line III-III in Fig. l;
Fig. 4 is a sectional view taken along a line IV~IV
in Fig. l;
Fig. 4A is a partial sectional view of the teeth of the worm and rack showing the relation between oil supply passages through the teeth of the worm and oil pocket provided for the rack teeth;
Fig. 5 :is a sectional view taken along a line V-V in Fig. l;
Fig. 6 is a sectional view taken along a line VI-VI
in Fig. 5.
Fig. 7A shows a diagrammatic sectional view of a hydrostatic pressure pad for calculating the hydrostatic pressure rigidity of the constant flow system;
Fig. 7B shows a similar view for calculating the hydrostatic pressure rigidity of the constant pressure system, and Fig. 8 is a plan view showing the annular hydrostatic pressure pad shown in Figs. 7A and 7B
DESCRIPTION OF THE PREFERREn EMBODIMENT
.
lZ~
.
The invention will now be described with reference to the accompanying drawings.
In this specification, a term "operating oil"
includes "static pressure oil", "pilot oil" and "auxiliary oil" in which static pressure oil means the operating oil supplied to oil pockets, pilot oil means the operating oil supplied to oil pockets at the time of commencement of meshing of the worm and the rack and the auxiliary oil means the operating oil supplied to oil supply ports of the worm when th'e worm does not mesh with the rac'~.
One embodiment of the hydrostatic pressure worm-rack device according to this invention will now be described.
As shown in Figs. 1 and 4, a rack 100 is secured to a stationary bed of a machine tool or the like, and a worm 30 is supported by a movable table. A driving device, for example an electric motor, for rotating the worm 30 is mounted on the table for moving the table along a slide way of the bed.
In this embodiment, operating oil is used (1) as hydrostatic oil for hydrostatically supporting the worm and the rac~, ~2) as pilot oil for preventing entrapping of air in hydrostatic pockets formed in the rack and (3) as auxiliary oil which discharges the operating oil out of the flanks at the opposite ends of the worm when it does not mate with the rack and prevents entrapping of air in the hydrostatic oil pockets.
.,; . ~ .
~24S13~
The pressure of pressurized oil outputted from a source 1 (an oil pump) is adjusted to a predete~mined value by a pressure reducing valve 2. Portions of the pressurized oil are adjusted to necessary flow quantities by flow quantity adjusting valves 3a ~ 3d respectively - and then supplied to peripheral grooves 11, 12, 13 and 16 of a distributor 10 rotatably mounted on a worm shaft 20 via oil conduits 6, 7, 8 and 9r respectively. The distributor 10 is constructed not to apply an undue radial force to the worm shaft '20. The pressurized oil is then supplied to the mating surfaces of the teeth of the worm and rack as follows.
We now describe the advantage of using flow quantity adjusting valves over conventional constant pressure valves utilizing fixed throttles with reference to Figs.
7A, 7B and 8 in which Fig. 7A shows a diagrammatic sectional view of a hydrostatic pressure pad for calculating the hydrostatic pressure rigidity of the conistant flow quantity system, Fig. 7B shows a similar view for calculating the hydrostat,ic pressure rigidity of the constant pressure system and Fig. 8 is a plan view showing the annular hydrostatic pressure pad shown in FigsO 7A and 7B.
As is well known in the art, as the gap width h increases the hydrostatic pressure rigidity decreases.
From these Figures we can obtain the following equations.
-6- ,.
'I ' lZD~5130 Weight supported W = af Ap PO ................... (1 Flow quantity at the hydrostatic pessure pad Bh3p ~h3P
12~L p .................... (2) where ~=
b 12L
,"~
Flow quantity through a throttle nd~(P~,--PO) Kc~P~ Po) ......... (3) where nd4 C l28e : viscosity coefficient of oil af: load coeff1cient Ap: hydrostatic pressure pad area = Ll x L2 PO: pressure in pocket Ps original pressure B :width of the land of the hydrostatic pressure . pad h : hydrostatic pressure gap L ;length of the hand of the hydrostatic pressure pad i, 7 ``` 12451~0 d : bore diameter of the throttle.
e: length of the throttle ; By substituting equation (1) into equation (2) we obtain W = afAp--3 ......... ,.. ,........ (4) From equatiPn (4), the hydrostatic pressure rigidity of the constant flow quantity system can be expressed as follows:
aw 3a + .~p~Q
dh Q K h4 (5) By substituting equation (2) into equation (5) we obtain (-- ~ )Q = 3afAp ~ ..... ......... (6) From equations ( 2 ) and (3) we obtain K P~ ---------........ (7 Ko By substituting equation (7) into equation ~1) we obtain .
124~130 a A P
W = - I K ------- -- - (8) ,, b ~,3 From equation (8) the hydrostatic pressure rigidity o the constant: pressure system becomes, dh ~Ap " KL 3)~ ~
Equation (9) shows that the rigidity becomes a maxium when K h3 = 2 .
At this time 2 = 3P, .
Hence ~- dh )~ = a~Ap h ...................... (10) From equations ~6) and (10) we can note that the hydrostatic pressure rigidity of the constant flow quantity system is 3 times larger than that of the constant pressure system.
æ -9-12~5i3~
The passages of the hydrostatic oil, the pilot oil and the auxiliary oil will now be described in detail with reference to Figs. 1 ~ 6.
Hydrostatic oil passaqe This passage is provided for the purpose of supplying the operating oil into hydrostatic pockets provided for the flanks of the teeth at the opposite ends of the worm 30 through oil supply openings for hydrostatically supporting the worm 30.
More particularly, the conduit 6 supplies the hydrostatic oil to the lefthand flank of a tooth of the worm, while the conduit 7 supplies the hydrostatic oil to the righthand flank. Conduits 6 and 7 are respectively connected to annular grooves 12 and 11 of the distributor 10. As shown in Fig. 1, the distributor 10 is rotatably supported by a stationary cylinder formed with oil passages connected to conduits 6 ~ 9 and grooves 11, 12, 13 and 16, respectively.
As shown in Fig. 2, the annular groove 11 is communicated with an arcuate groove llb on the inner surface of distributor 10 through an opening lla. In the same manner, the annular groove 12 is communicated with an arcuate groove 12b through an opening 12a.
As shown in Fig. 3, the worm shaft 20 is formed with oil passages 23 and 25 at positions corresponding to the arcuate grooves llb and 12b. Further, the worm shaft 20 is provided with longitudinal oil passages 2~ and 26 , . ...
-i13V
which are disposed at an equal circum~erential spacing on a circle having a center at the axis of the worm shaft - 20. Oil passages 24 and 26 are connected to oil passages 23 and 25 respectively. At about the central portion of the worm shaft 20, the-oil passage 24 is connected with a radial passage 27 which in turn is connected with a plurality of longitudinal oil passages 28 through the worm 30, which are spaced equally in the circumEerential direction. A plurality of oil passages 29 are ,-onnected 1~ to the oil passages 28 through respective teeth of the worm for supplying hydrostatic oil and the auxi]iary oil to the lefthand flanks of respective teeth of the worm 30. In the same manner, the hydrostatic oil and the auxiliary oil are supplied to the righthand flanks of respective teeth through oil passages 32 connected to oil passages 31. These oil passages 28 and 31 formecl through the worm shaft 20 are spaced equally in the circumferential direction in the same manner as oil passages 24 and 26.
The pressure generated by the operating oil supplied to arcuate grooves llb and 12b of the distributor 10 shown in Fig. 2 creates a force tending to urge the worm shaft 20 thus causing the same to deflect. ~ccordingly, it is necessary to eliminate this force. For creating the same pressure in the surface opposing the arcuate grooves llb and 12b, pairs of arcuate grooves 14b and 15b are formed in the inner surface of the distributor 10 and ., r ~ I
124~i~3V
. the operating oil supplied to the annular grooves 11 and 12 is supplied to these arcuate grooves 14b and 15b via openings 14a and 15a.
. . With the oil passage arrangement of supplying the hydrostatic oil to the flanks of the teeth of the rack, the hydrostatic oil is supplied to the lefthand oil pocket 101' through a circuit including conduit 7, annular groove 11, opening lla, arcuate groove llb, oil passages 23, 24, 27, 28 and 29. In the same manner, the hydrostatic oil is supplied to~the righthand oil pocket 101 provided for the rack teeth through conduit 6, annular groove 12, opening 12a, arcuate groove 12b, oil passages 25, 26, 36', 31 and 32. In this manner, the left- and righthand flanks of t:he worm teeth are hydrostatically supported by the oil supplied to hydrostatic pressure pockets 101 and 101' formed in the rack 100.
The auxiliary oil utilized for the purpose of preventing a;r entrapping is supplied to ports 34 on the not mating flanks of the teeth of the worm at both ends thereof through a circuit including conduit 9, annular groove 13 oE the distributor 10, opening 13a, a hollow ~quare shaped groove 13b, oil passages 24, 26, 27, 36', 28, 31, 29 and 32. As best shown in Pigs. 4A, passages 29 and 32 are alternately formed through the worm.
Por the purpose of maintaining the oil pressure in a plurality of axial oil passages 28 and 31 at a constant ~\ -12-."~ .
12451~0 value, it is necessary to make constant the axial length of these passages. ~or this purposer adjusting pins 35 having a length corresponding to the lead angle of worm 30 are threaded into both ends of the oil passages as shown in Fig. 1, the length being measured from the end surfaces of the worm. The purpose of the adjusting pin or plug 35 is to prevent formation of an air space causing a fluctuation of the oil pressure. At the time of commencement of the meshing of the worm 30 and rack 100, for the purpose of supplying the pressurized oil to the hydrostatic oil pockets at the opposite ends of the worm, cleaning of the ;ack flanks and removing residual air, arcuate grooves 34 leading to points at which meshing starts are formed on the opposite Elanks of the teeth at both ends as shown in Fig. 6. The pilot oil is supplied to oil supp]y ports 33 through a circuit including flow quantity adjusting valve 3d, conduit 8, oil passage 16, annular groove 35b of the worm shat, opening 35a, axial passage 3~ and radial oil passages 37.
The hydrostatic pressure worm-rack device according to this invention has the following advantages.
(1) Since the operating oil does not splash away from the not mating flanks of the worm teeth when the worm is rotated and since no air is entrapped between the mating flanks of the worm and rack, the pressure in the hydrostatic pressure oil pockets would not vary thus ensuring smooth feeding.
~ .
~Z~51~0
.
BACKGROUND OF THE INVENTION
This invention relates to a hydrostatic pressure worm-rack device utilized in a machine tool, for example.
Prior art hydrostatic pressure worm-rack devices can be classified into two types. In one type, hydrostatic pressure oil is supplied from the side of the rack, and in the other type, the hydrostatic pressure oil is supplied from the side of the?worm. Examples of the former type are disclosed in U.S. Pat. Nos. 3,789,956 and 4,148,227 and examples of the latter type are disclosed in U.S. Pat. Nos. 3,595,100 and 3,763,959. These patents illustrate a construction in which the hyd ostatic pressure oil is distributed from the end surfaces of a worm and a construction in which thrust forces g~nerated in hydrostatic pressure oil pockets provided for left and right ends of a worm are caused to balance with each other.
A hydrostatic pressure worm-rack device is used in a machine tool as a feed device. With recent increase in the feed speed of the machine tool, the number of revolutions of the worm is also increased so that lubricating oil in oil pockets provided for worm teeth flanks which do not engage with the teeth of a rack is caused to splash away by centrifugal force so that when the worm subsequently engages with the rack, air would be ,~, . .
~ .,.~
~2~5130 .. . .
- entrapped in the oil pockets which causes a pressure variation in the oil pockets, thus failing smooth high speed feeding.
Furthermore, according to the prior art S construction, since no pilot oil supply ports and pilot oil discharge~grooves are provided at both ends of the worm at which the worm begins to mesh with the rack, oil pressure would rise in the oil pockets so that air remaining in the oil pockets would not be discharged with the result that the pressure in the oil pockets pulsates which prevents smooth feeding.
According to the prior art constructions, at the time of supplying operating oil to the supply ports opening in the tooth flanks, since the operating oil is supplied through one end of the worm, pressure loss occurs before the operating oil reaches the supply ports at the far end. Accordingly, it is impossible to obtain uniform pressure in respective oil pockets, thus failing high speed feeding. ~oreove~, no means was provided for maintaining constant the pressure of the operating oil in respective oil supply ports of the tooth flanks.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved hydrostatic pressure worm-rack device capable of preventing entrapping air into oil pockets provided for the tooth flanks at both ends of the worm which do not mesh with the rack and maintaining uniform the pressure ,,",~
, ~, ~ .
1~513Q
in a plurality of hydrostatic pressure oil pockets when the worm meshes with the rack, thereby enabling smooth and high speed feeding of a machine tool, for example.
According to this invention, there is provided a hydrostatic pressure worm-rack device of the type comprising a worm formed with operating oil supply openings at opposite flanks of respective teeth of the worm, a rack meshing with the worm, opposite flanks of respective teeth of the rack being formed with hydrostatic pressure oil pockets, drive means for driving the shaft of the worm, and means for supplying the operating oil to the suFply openings of the worm, characterized in that there are provided an oil distributor mounted on one en~ of the worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of the worm and the rack and for supplying pilot oil to pilot oil ~upply ports provided for flanks of teeth at the opposite ends of the worm which firstly mate with the teeth of the rack, oil passages provided through the worm shaft and through respective teeth of the worm for independently supplying the operating oil and the pilot oil, and flow quantity adjusting valve means installed between the operating oil supply means and the oil distributor.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
~3~
~245130 Fig. 1 is a longitudinal sectional view showing an embodiment of the hydrostatic pressure worm-rack device according to this invention;
Fig. 2 is a perspective longitudinal sectional view of a distributor shown in Fig. l;
Fig. 3 is a sectional view taken along a line III-III in Fig. l;
Fig. 4 is a sectional view taken along a line IV~IV
in Fig. l;
Fig. 4A is a partial sectional view of the teeth of the worm and rack showing the relation between oil supply passages through the teeth of the worm and oil pocket provided for the rack teeth;
Fig. 5 :is a sectional view taken along a line V-V in Fig. l;
Fig. 6 is a sectional view taken along a line VI-VI
in Fig. 5.
Fig. 7A shows a diagrammatic sectional view of a hydrostatic pressure pad for calculating the hydrostatic pressure rigidity of the constant flow system;
Fig. 7B shows a similar view for calculating the hydrostatic pressure rigidity of the constant pressure system, and Fig. 8 is a plan view showing the annular hydrostatic pressure pad shown in Figs. 7A and 7B
DESCRIPTION OF THE PREFERREn EMBODIMENT
.
lZ~
.
The invention will now be described with reference to the accompanying drawings.
In this specification, a term "operating oil"
includes "static pressure oil", "pilot oil" and "auxiliary oil" in which static pressure oil means the operating oil supplied to oil pockets, pilot oil means the operating oil supplied to oil pockets at the time of commencement of meshing of the worm and the rack and the auxiliary oil means the operating oil supplied to oil supply ports of the worm when th'e worm does not mesh with the rac'~.
One embodiment of the hydrostatic pressure worm-rack device according to this invention will now be described.
As shown in Figs. 1 and 4, a rack 100 is secured to a stationary bed of a machine tool or the like, and a worm 30 is supported by a movable table. A driving device, for example an electric motor, for rotating the worm 30 is mounted on the table for moving the table along a slide way of the bed.
In this embodiment, operating oil is used (1) as hydrostatic oil for hydrostatically supporting the worm and the rac~, ~2) as pilot oil for preventing entrapping of air in hydrostatic pockets formed in the rack and (3) as auxiliary oil which discharges the operating oil out of the flanks at the opposite ends of the worm when it does not mate with the rack and prevents entrapping of air in the hydrostatic oil pockets.
.,; . ~ .
~24S13~
The pressure of pressurized oil outputted from a source 1 (an oil pump) is adjusted to a predete~mined value by a pressure reducing valve 2. Portions of the pressurized oil are adjusted to necessary flow quantities by flow quantity adjusting valves 3a ~ 3d respectively - and then supplied to peripheral grooves 11, 12, 13 and 16 of a distributor 10 rotatably mounted on a worm shaft 20 via oil conduits 6, 7, 8 and 9r respectively. The distributor 10 is constructed not to apply an undue radial force to the worm shaft '20. The pressurized oil is then supplied to the mating surfaces of the teeth of the worm and rack as follows.
We now describe the advantage of using flow quantity adjusting valves over conventional constant pressure valves utilizing fixed throttles with reference to Figs.
7A, 7B and 8 in which Fig. 7A shows a diagrammatic sectional view of a hydrostatic pressure pad for calculating the hydrostatic pressure rigidity of the conistant flow quantity system, Fig. 7B shows a similar view for calculating the hydrostat,ic pressure rigidity of the constant pressure system and Fig. 8 is a plan view showing the annular hydrostatic pressure pad shown in FigsO 7A and 7B.
As is well known in the art, as the gap width h increases the hydrostatic pressure rigidity decreases.
From these Figures we can obtain the following equations.
-6- ,.
'I ' lZD~5130 Weight supported W = af Ap PO ................... (1 Flow quantity at the hydrostatic pessure pad Bh3p ~h3P
12~L p .................... (2) where ~=
b 12L
,"~
Flow quantity through a throttle nd~(P~,--PO) Kc~P~ Po) ......... (3) where nd4 C l28e : viscosity coefficient of oil af: load coeff1cient Ap: hydrostatic pressure pad area = Ll x L2 PO: pressure in pocket Ps original pressure B :width of the land of the hydrostatic pressure . pad h : hydrostatic pressure gap L ;length of the hand of the hydrostatic pressure pad i, 7 ``` 12451~0 d : bore diameter of the throttle.
e: length of the throttle ; By substituting equation (1) into equation (2) we obtain W = afAp--3 ......... ,.. ,........ (4) From equatiPn (4), the hydrostatic pressure rigidity of the constant flow quantity system can be expressed as follows:
aw 3a + .~p~Q
dh Q K h4 (5) By substituting equation (2) into equation (5) we obtain (-- ~ )Q = 3afAp ~ ..... ......... (6) From equations ( 2 ) and (3) we obtain K P~ ---------........ (7 Ko By substituting equation (7) into equation ~1) we obtain .
124~130 a A P
W = - I K ------- -- - (8) ,, b ~,3 From equation (8) the hydrostatic pressure rigidity o the constant: pressure system becomes, dh ~Ap " KL 3)~ ~
Equation (9) shows that the rigidity becomes a maxium when K h3 = 2 .
At this time 2 = 3P, .
Hence ~- dh )~ = a~Ap h ...................... (10) From equations ~6) and (10) we can note that the hydrostatic pressure rigidity of the constant flow quantity system is 3 times larger than that of the constant pressure system.
æ -9-12~5i3~
The passages of the hydrostatic oil, the pilot oil and the auxiliary oil will now be described in detail with reference to Figs. 1 ~ 6.
Hydrostatic oil passaqe This passage is provided for the purpose of supplying the operating oil into hydrostatic pockets provided for the flanks of the teeth at the opposite ends of the worm 30 through oil supply openings for hydrostatically supporting the worm 30.
More particularly, the conduit 6 supplies the hydrostatic oil to the lefthand flank of a tooth of the worm, while the conduit 7 supplies the hydrostatic oil to the righthand flank. Conduits 6 and 7 are respectively connected to annular grooves 12 and 11 of the distributor 10. As shown in Fig. 1, the distributor 10 is rotatably supported by a stationary cylinder formed with oil passages connected to conduits 6 ~ 9 and grooves 11, 12, 13 and 16, respectively.
As shown in Fig. 2, the annular groove 11 is communicated with an arcuate groove llb on the inner surface of distributor 10 through an opening lla. In the same manner, the annular groove 12 is communicated with an arcuate groove 12b through an opening 12a.
As shown in Fig. 3, the worm shaft 20 is formed with oil passages 23 and 25 at positions corresponding to the arcuate grooves llb and 12b. Further, the worm shaft 20 is provided with longitudinal oil passages 2~ and 26 , . ...
-i13V
which are disposed at an equal circum~erential spacing on a circle having a center at the axis of the worm shaft - 20. Oil passages 24 and 26 are connected to oil passages 23 and 25 respectively. At about the central portion of the worm shaft 20, the-oil passage 24 is connected with a radial passage 27 which in turn is connected with a plurality of longitudinal oil passages 28 through the worm 30, which are spaced equally in the circumEerential direction. A plurality of oil passages 29 are ,-onnected 1~ to the oil passages 28 through respective teeth of the worm for supplying hydrostatic oil and the auxi]iary oil to the lefthand flanks of respective teeth of the worm 30. In the same manner, the hydrostatic oil and the auxiliary oil are supplied to the righthand flanks of respective teeth through oil passages 32 connected to oil passages 31. These oil passages 28 and 31 formecl through the worm shaft 20 are spaced equally in the circumferential direction in the same manner as oil passages 24 and 26.
The pressure generated by the operating oil supplied to arcuate grooves llb and 12b of the distributor 10 shown in Fig. 2 creates a force tending to urge the worm shaft 20 thus causing the same to deflect. ~ccordingly, it is necessary to eliminate this force. For creating the same pressure in the surface opposing the arcuate grooves llb and 12b, pairs of arcuate grooves 14b and 15b are formed in the inner surface of the distributor 10 and ., r ~ I
124~i~3V
. the operating oil supplied to the annular grooves 11 and 12 is supplied to these arcuate grooves 14b and 15b via openings 14a and 15a.
. . With the oil passage arrangement of supplying the hydrostatic oil to the flanks of the teeth of the rack, the hydrostatic oil is supplied to the lefthand oil pocket 101' through a circuit including conduit 7, annular groove 11, opening lla, arcuate groove llb, oil passages 23, 24, 27, 28 and 29. In the same manner, the hydrostatic oil is supplied to~the righthand oil pocket 101 provided for the rack teeth through conduit 6, annular groove 12, opening 12a, arcuate groove 12b, oil passages 25, 26, 36', 31 and 32. In this manner, the left- and righthand flanks of t:he worm teeth are hydrostatically supported by the oil supplied to hydrostatic pressure pockets 101 and 101' formed in the rack 100.
The auxiliary oil utilized for the purpose of preventing a;r entrapping is supplied to ports 34 on the not mating flanks of the teeth of the worm at both ends thereof through a circuit including conduit 9, annular groove 13 oE the distributor 10, opening 13a, a hollow ~quare shaped groove 13b, oil passages 24, 26, 27, 36', 28, 31, 29 and 32. As best shown in Pigs. 4A, passages 29 and 32 are alternately formed through the worm.
Por the purpose of maintaining the oil pressure in a plurality of axial oil passages 28 and 31 at a constant ~\ -12-."~ .
12451~0 value, it is necessary to make constant the axial length of these passages. ~or this purposer adjusting pins 35 having a length corresponding to the lead angle of worm 30 are threaded into both ends of the oil passages as shown in Fig. 1, the length being measured from the end surfaces of the worm. The purpose of the adjusting pin or plug 35 is to prevent formation of an air space causing a fluctuation of the oil pressure. At the time of commencement of the meshing of the worm 30 and rack 100, for the purpose of supplying the pressurized oil to the hydrostatic oil pockets at the opposite ends of the worm, cleaning of the ;ack flanks and removing residual air, arcuate grooves 34 leading to points at which meshing starts are formed on the opposite Elanks of the teeth at both ends as shown in Fig. 6. The pilot oil is supplied to oil supp]y ports 33 through a circuit including flow quantity adjusting valve 3d, conduit 8, oil passage 16, annular groove 35b of the worm shat, opening 35a, axial passage 3~ and radial oil passages 37.
The hydrostatic pressure worm-rack device according to this invention has the following advantages.
(1) Since the operating oil does not splash away from the not mating flanks of the worm teeth when the worm is rotated and since no air is entrapped between the mating flanks of the worm and rack, the pressure in the hydrostatic pressure oil pockets would not vary thus ensuring smooth feeding.
~ .
~Z~51~0
(2) Since pilot openings and pilot grooves are formed at the end flanks of the worm, at the time of engaging of the worm and the rackr the pressure does not rise between the inlet and outlet ports of the hydrostatic pressure oil pockets. Moreover, since there is no air remaining in the hydrostatic pressure oil pockets the pressure therein does not pulsate, thus ensuring smooth feeding.
(3) ',incé the operating oil is supplied to flanks from the center of the axial ~il passage formed in the worm shaft, and moreover since the length of the axial oil passages 28 and 31 are made constant, it is possible to create uniform oil pressure in the oil pockets.
~4) i~s described with mathematical equations the hydrostatic pressure rigidity of the constant flow quantity system utilizing the flow quantity adjusting valves 3a ~ 3d is 3 times larger than that of the constant pressure system.
~4) i~s described with mathematical equations the hydrostatic pressure rigidity of the constant flow quantity system utilizing the flow quantity adjusting valves 3a ~ 3d is 3 times larger than that of the constant pressure system.
Claims (5)
1. In a hydrostatic pressure worm-rack device of the type comprising a worm formed with operating oil supply openings at opposite flanks of respective teeth of the worm, a rack meshing with said worm, opposite flanks of respective teeth of said rack being formed with hydrostatic pressure oil pockets, drive means for driving a shaft of said worm, and means for supplying the operating oil to said supply openings of said worm, the improvement which comprises:
an oil distributor mounted on one end of said worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of said worm and said rack and for supplying pilot oil to pilot oil supply ports provided for flanks of teeth at the opposite ends of said worm which firstly mate with the teeth of said rack;
oil passages provided through said worm shaft and through respective teeth of said worm for independently supplying said operating oil and said pilot oil; and flow quantity adjusting valve means installed between said operating oil supply means and said oil distributor.
an oil distributor mounted on one end of said worm shaft for supplying oil to mating surfaces and not mating surfaces of the teeth of said worm and said rack and for supplying pilot oil to pilot oil supply ports provided for flanks of teeth at the opposite ends of said worm which firstly mate with the teeth of said rack;
oil passages provided through said worm shaft and through respective teeth of said worm for independently supplying said operating oil and said pilot oil; and flow quantity adjusting valve means installed between said operating oil supply means and said oil distributor.
2. The hydrostatic pressure worm-rack device according to claim 1 wherein said oil distributor is provided on its inner surface with a first pair of arcuate grooves for supplying the pressurized oil to opposite flanks of the teeth of said worm, and with a second pair of arcuate grooves diametrically opposing said first pair of arcuate grooves and having the same pressure area as said first pair of arcuate grooves.
3. The hydrostatic pressure worm-rack device according to claim 1 wherein said oil passages comprise a plurality of axial oil passages in said worm axis and spaced equally in a circumferential direction on a circle concentric with an axis of said worm shaft and a plurality of radial oil passages equally spaced in the circumferential direction and connected to an annular groove of said oil distributor.
4. The hydrostatic pressure worm-rack device according to claim 1 which further comprises adjusting pins having a length of lead angle of said worm and threaded into said oil passages.
5. The hydrostatic pressure worm-rack device according to claim 1 wherein a pilot oil supply passage and a hydrostatic oil supply opening adjacent thereto are spaced such that said pilot oil supply passage and said hydrostatic oil supply opening do not open in the same oil pocket.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59108719A JPS59225001A (en) | 1983-05-30 | 1984-05-30 | Ski boots |
| JP191087/1984 | 1984-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1245130A true CA1245130A (en) | 1988-11-22 |
Family
ID=14491831
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000490581A Expired CA1245130A (en) | 1984-05-30 | 1985-09-12 | Hydrostatic pressure worm-rack devices |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1245130A (en) |
-
1985
- 1985-09-12 CA CA000490581A patent/CA1245130A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |