Allow the condenser type rotary encoder of transmission shaft axial float
Technical field
The present invention relates to the encoder techniques field, particularly a kind of condenser type rotary encoder that allows the transmission shaft axial float.
Background technology
Rotary encoder is the device of measuring rotating speed, the mechanical quantity such as the angular displacement of output shaft, angular velocity can be converted to the scrambler of corresponding electric pulse or digital quantity.
Traditional rotary encoder generally all is to be fixedly mounted on the motor shaft of motor at present.Because motor shaft not only produces diameter run-out in the motor movement process, also can produce axial float, expanding with heat and contract with cold in addition also to cause the variation of motor shaft axial length.And the axial play of motor shaft can cause the decline of scrambler measuring accuracy, even can affect the serviceable life of scrambler.Take photoelectric rotary coder as example, photoelectric rotary coder generally is comprised of photoelectric code disk and light-sensitive detector; In the practical application, the distance of photoelectric code disk and light-sensitive detector is very little, usually the order of magnitude below millimeter.Photoelectric code disk is fixedly connected with motor shaft, light-sensitive detector and casing are fixed, because the axial float of motor shaft can cause the variation of distance between photoelectric code disk and the photodetector, so require axial float can only float in the setting scope, the variation that exceeds setting not only can make signal quality and the precise decreasing of scrambler, and because friction can be shortened the serviceable life of scrambler, can cause the damage of scrambler axle system and photoelectric code disk when serious.
The impact that scrambler is caused for solving above-mentioned motor shaft play, the patent No. is that the Chinese utility model patent of CN201020619546.2 has proposed a kind of buffer structure of encoder, its structure and principle are as follows: scrambler is installed on the extension shaft of motor, the end face of scrambler is connected by screw on web joint, in the attachment screw hole of described web joint, be provided with spring, screw passes spring and is connected with web joint, guarantees that scrambler has elasticity with being connected of web joint.Described web joint is fixed by screws on the motor end face, and the fixing screw hole on described screw and the web joint is directly fixing.By the buffer structure of above-mentioned design, when can guarantee the extension shaft axial float of motor, scrambler plays the effect that elasticity connects along with extension shaft carries out axial float together.But adopt above-mentioned be flexible coupling or mode that spring connects can to cause scrambler to be measured inaccurate, the error of hysteresis was arranged in the moment that motor begins to rotate, in the moment that motor stops leading error is arranged.
The method of utilizing the principle of measuring electric capacity to obtain displacement just has been suggested decades ago.The patent No. is U.S.3,938,113 United States Patent (USP) discloses a kind of scrambler of measuring electric capacity perception displacement that adopts, its structure and principle are as follows: made the electrode that transmits on the scale, measure via capacity coupled signal on the read head, perhaps the electrode on the read head transmits, and the electrode measurement on the scale is via capacity coupled signal, by the deciphering of certain way, read head just can provide relative shift.Incremental displacement is measured to be needed to make uniform scale at scale, and these scales are always realized with the strip shaped electric poles of evenly distributed conduction.Because the requirement of scale homogeneity, these strip shaped electric poles must be same sizes, same shape and same electric conductivity, only in this way, thereby the information that read head obtains just is not subjected to the impact of electrode heterogencity to calculate exactly relative shift.This capacitive technologies both can be used for the measurement of linear displacement, also can be used for the measurement of the anglec of rotation.
The condenser type rotary encoder divides moving grid and quiet grid two parts, all is precision machined printed circuit board (PCB).As shown in Figure 1, emitting electrode 61 and receiving electrode 62 are arranged on the moving grid, between emitting electrode 61 and receiving electrode 62, screening electrode 63 is arranged, avoid emitting electrode 61 to the coupling of the direct capacitance between the receiving electrode 62.As shown in Figure 2, repeller 71 and screening electrode 72 are arranged on the quiet grid, repeller 71 is consistent with the width of screening electrode 72, and screening electrode 72 needs reliable ground.In the structural drawing of condenser type rotary encoder as depicted in figs. 1 and 2, have 48 emitting electrodes on the moving grid
61, it is variable that the pole span of emitting electrode 61 is pressed actual requirement, and per 4 emitting electrodes 61 are corresponding to a reflecting electrode.Per 8 emitting electrodes 61 are one group on the moving grid, totally 6 groups.Every group of emitting electrode 61 is numbered A to link to each other to emitting electrode 61 circuit of the same numbering of H.During operation, the grid face parallel coaxial of two printed circuit board is relative, and spacing is about 0.1mm.
But above-mentioned this condenser type rotary encoder requires the grid face of two printed circuit board parallel during operation, and it is concentric circles that the center of circle of circular pattern requires, and coaxial with motor shaft or other driving shafts.Air gap between two parallel circuit boards is strict, and reason is when air gap is excessive, signal strength weakening, and signal to noise ratio (S/N ratio) descends, and directly affects the output accuracy of scrambler; When air gap was too small, signal intensity was excessive, surpassed range, made scrambler can't obtain correct signal, and these two circuit boards also can rub when serious, caused losing efficacy or destroying.Therefore the condenser type rotary encoder does not still solve the problem that the motor shaft axial float causes encoder performance to descend, lost efficacy even destroyed.
Summary of the invention
The present invention is installed on the motor shaft in order to solve present existing rotary encoder, the rotary encoder hydraulic performance decline, inefficacy even the destroyed problem that cause owing to the axial float of motor shaft, and a kind of condenser type rotary encoder that allows the transmission shaft axial float that provides.
For reaching above-mentioned functions, technical scheme provided by the invention is:
A kind of condenser type rotary encoder that allows the transmission shaft axial float, comprise quiet grid and moving grid, described condenser type rotary encoder also comprises coaxial inner cylinder and out cylinder, described inner cylinder be fixed on the transmission shaft and with described transmission shaft coaxial rotation, described out cylinder is fixedly installed; Described moving grid is arranged on the outside surface of described inner cylinder, and described quiet grid are arranged on the inside surface of described out cylinder, has certain air gap between described quiet grid and the described moving grid.
Preferably, described quiet grid comprise the exciting electrode bar that some strips are identical, described moving grid comprises more than one induction electrode bar, the length of described induction electrode bar is greater than the length of described exciting electrode bar, to guarantee that when the described transmission shaft generation play, described induction electrode bar covers described exciting electrode bar fully.
Preferably, described quiet grid also comprise the receiving electrode bar of one or more.
Preferably, the quantity of described receiving electrode bar is two, and described two receiving electrode bars are parallel to each other and vertical with described exciting electrode bar, and lays respectively at the top and bottom of exciting electrode bar.
Preferably, described induction electrode bar comprises the first induction electrode bar and the second induction electrode bar of anti-symmetric shape, described the first induction electrode bar and described the second induction electrode bar respectively with two electric capacity of the corresponding formation of described two receiving electrode bars.
Preferably, described the first induction electrode bar and described the second induction electrode bar place of matching are shaped as sine wave shape, and described exciting electrode bar length is greater than the peak-to-peak height of described sine wave.
Transmission shaft of the present invention refers to motor shaft or other driving shaft, the extension shaft that perhaps is connected with motor shaft or other driving shaft.
Beneficial effect of the present invention is: (1), solved because the moving grid that the transmission shaft play causes and quiet grid contact friction even damaged problem, by coaxial inner cylinder and out cylinder are set, and described moving grid is arranged on the outside surface of described inner cylinder, described quiet grid are arranged on the inside surface of described out cylinder, has certain air gap between described quiet grid and the described moving grid, adopt this structure, in transmission shaft radial-play tolerance, the possibility that described moving grid and described quiet grid are not in contact with one another;
(2), measure accurately, exciting electrode bar length is greater than the sine-shaped peak-to-peak height of induction electrode bar on the described moving grid on the described quiet grid, when described inner cylinder and out cylinder move axially, exciting electrode bar on the described quiet grid covers the sine wave shape of induction electrode bar on the described moving grid fully, and signal keeps not being subjected to the impact of axial float like this;
(3), simplified the structure of product, improved the serviceable life of product, by at described quiet grid the receiving electrode bar being set, the electric charge of the induction electrode bar induction on the described moving grid can be sensed on the described receiving electrode bar, thereby has avoided introducing signal transmssion line at moving grid.
Description of drawings
Fig. 1 is the structural representation of existing moving grid;
Fig. 2 is the structural representation of existing quiet grid;
Fig. 3 is structural representation of the present invention;
Fig. 4 is the structural representation after quiet grid of the present invention launch;
Fig. 5 is that moving grid of the present invention cooperates the structural representation after launching with quiet grid;
Fig. 6 is modulation signal acceptance/processor structure schematic diagram.
Embodiment
The present invention is further elaborated to accompanying drawing 6 below in conjunction with accompanying drawing 1:
A kind of condenser type rotary encoder that allows the transmission shaft axial float as shown in Figure 3, comprise quiet grid 2 and moving grid 3, also comprise coaxial inner cylinder 4 and out cylinder 5, inner cylinder 4 be fixed on the transmission shaft 1 and with transmission shaft 1 coaxial rotation, transmission shaft 1 is motor shaft or other driving shaft, or the extension shaft of motor shaft or other driving shaft, out cylinder 5 is fixedly installed, transfixion; Moving grid 3 is arranged on the outside surface of inner cylinder 4, and quiet grid 2 are arranged on the inside surface of out cylinder 5, and quiet grid 2 and moving grid 3 keep coaxial and have certain air gap between the two.Adopt this structure because quiet grid 2 are coaxial with moving grid 3, even axial float occurs transmission shaft 1 like this, friction or collision can not occur in quiet grid 2 and moving grid 3 yet, thereby guarantee the life-span of scrambler.
Quiet grid 2 comprise the exciting electrode bar 21 that some strips are identical, and exciting electrode bar 21 is electrically connected with modulation signal acceptance/processor, and these exciting electrode bars 21 consist of a group or a cycle with even number, such as two, four, six, eight etc.Number according to one-period underexcitation electrode strip 21, degree of whole cycles 360 of pumping signal also is divided into several phase deviations accordingly, because moving grid 3 of the present invention and quiet grid 2 are separately positioned on inner cylinder 4 and the out cylinder 5, in order to express conveniently, as shown in Figure 4, out cylinder 5 structures are launched, become linear structure, but its principle, working method and function are constant.At the present embodiment, consist of a group or a cycle by four exciting electrode bars 21, we press A successively to four exciting electrode bars 21 in one group of exciting electrode bar 21 for convenience of description, B, C, the D numbering, numbering identical exciting electrode bar 21 links together by transmission line 8 and forms an excitation phase, add an amplitude by modulation signal acceptance/processor on the exciting electrode bar 21 of every group of identical numbering, the pumping signal that frequency is identical with phase place, the phase differential of pumping signal is 90 ° on the exciting electrode bar 21 of adjacent numbering, namely is 360 ° of quantity by one group of exciting electrode bar 21 contained exciting electrode bar 21 are divided equally.Suppose that the first group # is that to add a phase place on the exciting electrode bar 21 of A be 0 ° pumping signal, then be numbered the pumping signal phase place that adds on the exciting electrode bar 21 of B and then be 90 °, analogize in proper order, the pumping signal phase place that then is numbered on the exciting electrode bar 21 of D just is 270 °; Being that the phase place of exciting electrode bar 21 of A is identical and the second group # is pumping signal phase place and first group # of the exciting electrode bar 21 of A, is 0 °, the like to all groups.If eight exciting electrode bars 21 consist of one-period, the phase differential of pumping signal is 45 ° on each exciting electrode bar 21 so.
As shown in Figure 3, moving grid 3 comprises more than one induction electrode bar 31, as shown in Figure 5, for explaining conveniently, we also cooperate moving grid 3 cylindraceous and are launched into linear shape and describe with quiet grid 2, after the pumping signal that modulation signal acceptance/processor produces passed to exciting electrode bar 21 on the quiet grid 2, exciting electrode bar 21 was transmitted to induction electrode bar 31 on the moving grid 3 to this signal, by induction electrode bar 31 signal is transferred to modulate circuit again and carries out demodulation.Because moving grid 3 along with inner cylinder 4 is done rotation, is a movement parts, introduces signal transmssion line in movement parts and can cause structure complicated and signal transmssion line easily to be out of order.For addressing this problem, the present invention is provided with receiving electrode bar 22 at quiet grid 2, receiving electrode bar 22 has corresponding area with induction electrode bar 31, the two poles of the earth of electric capacity have just been consisted of like this with regard to receiving electrode bar 22 and induction electrode bar 31, modulation signal on the induction electrode bar 31 just can be reflected back receiving electrode bar 22, sends modulation signal acceptance/processor to by receiving electrode bar 22 again and processes.
For reduce ground unrest or common mold noise interference as far as possible, in the present embodiment, the modulation signal decision design becomes two paths of differential signals to realize common mode noise rejection, for reaching this purpose, as shown in Figure 4, the quantity of receiving electrode bar 22 adopts two, and two receiving electrode bars 22 are parallel to each other and vertical with exciting electrode bar 21, and lay respectively at the top and bottom of exciting electrode bar 21; As shown in Figure 5, induction electrode bar 31 comprises the first induction electrode bar 311 and the second induction electrode bar 312 of anti-symmetric shape, the first induction electrode bar 311 and the second induction electrode bar 312 respectively with two electric capacity of upper and lower two receiving electrode bars, 22 corresponding formations, the modulation signal of two-pass DINSAR is produced by the first induction electrode bar 311 and the second induction electrode bar 312, and is sent to modulation signal reception/processor by upper and lower two receiving electrode bars 22 respectively and processes.
As shown in Figure 5, the first induction electrode bar 311 and the second induction electrode bar 312 places of matching are shaped as sine wave shape, and exciting electrode bar 21 length are greater than the peak-to-peak height of described sine wave.When axial relatively moving occurs because axial float occurs transmission shaft 1 when inner cylinder 4 and out cylinder 5, exciting electrode bar 21 on the quiet grid 2 covers the part of the sine wave shape of the first induction electrode bar 311 and the second induction electrode bar 312 on the moving grid 3 fully, thereby makes modulation signal keep not being subjected to the impact of transmission shaft 1 axial float.
As shown in Figure 5, the
induction electrode bar 31 on each moving
grid 3 can by with quiet grid 2 on the corresponding area induced charge of exciting electrode bar 21.The first
induction electrode bar 311 and the second
induction electrode bar 312 places of matching are shaped as sine wave shape, and on sinusoidal cycle and the quiet grid 2 cycle of every group of
exciting electrode bar 21 corresponding, i.e. equal in length.When moving
grid 3 has relative rotation with quiet grid 2, be without loss of generality, this displacement can be converted to the phasing degree at one-period
The electric charge V that then can respond on the first induction electrode bar 311
A:
Wherein K is coefficient, and is relevant with many factors, and such as air gap, air gap specific inductive capacity etc. between pumping signal amplitude, induction electrode bar 31 areas, moving grid 3 and the quiet grid 2, generally under particular design and working environment, K is approximately constant.
The electric charge V of induction on the second induction electrode bar 312
A*Opposite in sign with induction on the first induction electrode bar 311:
The electric charge of induction is reflected back the upper receiving electrode bar 22 on the quiet grid 2 on the first induction electrode bar 311, the electric charge of induction is reflected back the lower receiving electrode bar 22 on the quiet grid 2 on the second induction electrode bar 312, is transferred to modulation signal reception/processor by these two receiving electrode bars 22 respectively again.
In the present embodiment, the collection of the signal in the modulation signal reception/processor directly links to each other with quiet grid 2 with demodulator circuit, in this circuit, and the integrated generation circuit of pumping signal, this is because demodulation needs this with signal frequently.Pumping signal occurs with the modulation signal demodulation by same processing of circuit.Pumping signal occurs that multiple implementation can be arranged, namely there is mimic channel that the implementation method of digital circuit is also arranged, purpose is exactly to produce the multichannel periodic signal of dividing equally phase differential, adopt in the present embodiment sinusoidal signal, because four exciting electrode bars 21 are one-period, thus pumping signal be four the tunnel differ be 90 the degree sine waves; For guaranteeing signal intensity, preferential proportion is greater than 10KHz, and peak-to-peak value is 3 to 15V sine wave.On the one hand, this four tunnel pumping signal sends corresponding exciting electrode bar 21 to by the signal transmission line 8 on the quiet grid 2, and on the other hand, the sinusoidal signal of 0 degree and 90 degree phase places is namely sinusoidal to send signal demodulation module 13 to simultaneously with cosine signal.
As shown in Figure 6, the two-pass DINSAR modulation signal is delivered to signals collecting and
amplification module 11 from the
receiving electrode bar 22 on the quiet grid 2, because its signal amplitude is faint, need to carry out differential amplification, suppress common-mode noise, signal amplitude is brought up to hundreds of millivolts to thousands of millivolts.
Signal demodulation module 13 receives these modulation signals that amplified, and multiplying each other with the pumping signal of pumping
signal generation module 12 generations can dissociative excitation signal and displacement signal.Multiply each other with sinusoidal excitation signal, signal results comprises trigonometric function and the displacement of pumping signal doubled frequency
Cosine function namely
Compare with the signal of pumping signal doubled frequency,
Be DC quantity, filter high fdrequency component by low-
pass filtering module 14, just obtain
Similarly, the modulation signal that amplified and cosine pumping signal multiply each other, and signal results comprises trigonometric function and the displacement of pumping signal doubled frequency
Sine function namely
Compare with the signal of pumping signal doubled frequency,
Be DC quantity, filter high fdrequency component by low-
pass filtering module 14, just obtain
Obtain displacement by said method
Cosine and sine signal after, just can calculate displacement by the whole bag of tricks.Some product can directly be accepted this cosine and sine signal as the output of scrambler on the market, and this technology is quite ripe, how to convert displacement signal to cosine and sine signal so the present invention repeats no more.
The above embodiment, it is preferred embodiments of the present invention, be not to limit practical range of the present invention, therefore all equivalences of doing according to the described structure of the present patent application claim, feature and principle change or modify, all should be included in the patent claim of the present invention.